DC bus balancer circuit

ES 2 553 007 T3

DC bus balancer circuit

Description

BACKGROUND OF THE INVENTION

[0001] Uninterruptible power supplies (UPS) including voltage converters are a fundamental part of many electrical systems, such as power supply systems for computers and servers in data centers. UPS can be used with many typical power systems including single and 3-phase connections, and can be used with low-power systems (for example, a home computer) and high-power systems (for example, large centers. data or process facilities). High power systems typically use a 3 phase power connection (eg, X, Y, and Z phases). A 3-phase UPS voltage converter is typically used to provide 3-phase AC power to a 3-phase load, to convert a 3-phase AC voltage from one level to another, and to provide 3-phase power to a charging in the event of a power outage. The input and output connections to a 3-phase UPS voltage converter are typically three or four terminal connections, one connection for each phase of the 3-phase power connection, and an optional neutral connection. A battery is also typically coupled to the UPS voltage converter and is used to store energy for use in the event of a power failure.

[0002] Typical high power UPS (eg, above 100 kW) are operated using nominal AC input voltages of 3x400 V (in Europe) or 3x480 V (in the US). Transformerless UPS can operate on an internal DC bus voltage of 6450 V. In such a configuration, components contained in the UPS are preferably rated for at least 1,200 V operation, due to large overvoltages associated with loose inductances of physically large bipolar isolating transistor (IGBT) modules. The use of 1200 V components, however, generally leads to increased conduction and switching losses, thus reducing efficiency.

Furthermore, an imbalance in the DC power bus voltages of the UPS decreases its efficiency.

[0004] ANNETTE VON JOUANNE ET AL: A Multilevel Inverter Approach Providing DC-Link Balancing, Ride-Through Enhancement and Common-Mode Voltage Elimination shows a DC voltage balancing circuit. The use of minimum and maximum converters to balance the neutral point voltage in a three-level system is disclosed.

[0005] US 6 459 596 B1 and US 5 644 483 A disclose a rectifier that balances the voltages of four levels.

SUMMARY OF THE INVENTION

[0006] The invention is defined by the features of claim 1.

[0007] Preferred embodiments are defined in the dependent claims.

[0008] The capabilities of the invention, in addition to the invention itself, will be more fully understood after a review of the following figures, detailed description, and claims.

BRIEF DESCRIPTION OF THE FIGURES

[0009]

FIG. 1 is a schematic diagram of an example 3-phase UPS.

FIG. 2 is a circuit diagram of an exemplary AC / DC converter.

FIG. 3 is a graph depicting an exemplary power signal provided to the AC / DC converter of the figure. two.

FIGS. 4A-4C are graphs representing the switching states in the AC / DC converter in the figure. two.

FIG. 5 is a circuit diagram of an exemplary pulse width modulation control circuit. FIG. 6 is a diagram of exemplary control signals for use with the pulse width modulation control circuit of the figure. 5.

FIG. 7 is a circuit diagram of an exemplary DC / AC converter.

FIG. 8 is a graph representing exemplary AC and DC power signals.

FIG. 9A-9C are graphs representing switch states in the DC / AC converter in the figure. 8. FIG. 10 is a circuit diagram of an exemplary AC / AC converter.

FIG. 11 is a circuit diagram of an exemplary DC / DC converter.

FIG. 12 is a circuit diagram of a DC bus balancer in accordance with one embodiment of the invention.

ES 2 553 007 T3

FIG. 13 is a graph depicting exemplary signals for the control of switches included in the DC bus balancer of FIG. 12.

FIG. 14 is a flow diagram of a process to provide power for the 3-phase UPSs shown in the figure. 1.

DETAILED DESCRIPTION

[0010] The following examples provide techniques for providing an uninterruptible 3-phase power supply to a load. For example, a 3-phase uninterruptible power transformer includes AC / DC converters (for example, power factor correction modules), DC / AC converters (for example, inverters), a DC / DC conversion module, multiple buses DC link and a DC bus balancer. AC / DC converters receive 3-phase AC power (for example, 3 x 400 V or 3 x 480 V phase-to-phase) from a 3-phase power supply and convert the 3-phase power to direct current (for example, with multiple voltage levels). Each of the AC / DC converters receives one phase from the 3-phase power connection. During normal operation (for example, when adequate 3-phase power is received from the 3-phase power supply), the DC power present on the DC buses provides power to the DC / AC converters. On the other hand, during normal operation, a DC / DC converter converts the direct current of power present in DC buses to a voltage that is used to charge the battery. During other times (for example, when 3-phase power is insufficient or not available), DC power is supplied to the DC / AC converters from the battery. DC / AC converters convert direct current into 3-phase AC power (for example, each of the DC / AC converters provide a single phase of the 3-phase signal). The voltages received by the AC / DC converters and the voltages provided by the DC / AC converters can be the same or different. During normal operation or otherwise, the DC bus balancer balances the voltages present on the DC buses by moving power between the DC buses.

With reference to the figure. 1, a UPS 5 includes AC / AC modules 10, 20, and 30, a DC / DC module 40, a battery 50, and buses 60, 61, 62, 63, and 64. The AC / AC module 10 includes a AC / DC converter 11 coupled to a DC / AC converter 12 via buses 60, 61, 62, 63 and 64. The AC / AC module 20 includes an AC / DC converter 21 coupled to a DC / AC converter 22 to through buses 60, 61, 62, 63, and 64. The AC / AC module 30 includes and the AC / DC converter 31 coupled to a DC / AC converter 32 through buses 60, 61,

62, 63, and 64. The DC / DC module 40 includes a DC / DC converter 41 and a DC bus balancer 42. The DC / DC converter 41 is coupled to the DC bus balancer 42 via buses 60, 61, 62, 63, and 64. AC / AC modules 10, 20, and 30, and DC / DC module 40 are interconnected via buses 60, 61, 62, 63, and 64. UPS 5 is configured to provide power to a load (not shown) either from 3-phase power supply, coupled to UPS 5, and / or from energy stored in battery 50.

[0012] Each of the AC / AC modules 10, 20, and 30 are configured to receive a phase (for example, phase X, Y, or Z) of a 3-phase power supply at a first current voltage alternating, and to provide a second AC voltage through an outlet. The AC / DC converter 11 includes inputs 13 and 14; the AC / DC converter 21 includes inputs 23 and 24; and the AC / DC converter 31 includes inputs 33 and 34. The DC / AC converter 12 includes outputs 15 and 16; DC / AC converter 22 includes outputs 25 and 26; and the DC / AC converter 32 includes outputs 35 and 36. Each of the AC / AC modules 10, 20, and 30 are configured to be coupled to one phase of a 3 phase power supply and to a neutral connection. For example, input 13 of the AC / DC converter 11 can be coupled to the X phase, input 23 of the AC / DC converter 21 can be coupled to the Y phase, and input 33 of the AC / DC converter. DC 31 can be coupled to phase Z. Inputs 14, 24, and 34 are configured to be coupled to the neutral connection of the 3 phase power supply (or a ground connection). Each of the AC / AC modules 10, 20, and 30 are configured to provide an output that includes one phase of a 3 phase output, although other configurations are possible. For example, output 15 can be configured to provide phase X output, output 25 can be configured to provide phase Y output, and 35 can be configured to provide phase Z output. Each of the outputs 16, 26 and 36 are configured to be coupled to a neutral connection of a load. Each of the AC / AC modules 10, 20, and 30 are configured to share power across buses 60, 61, 62,

63, and 64.

The DC / DC module 40 can receive power from (that is, when in a charging state) and provide power to (that is, when in a discharge state) the AC / AC modules 10, 20 , and / or 30. The DC / DC converter 41 is configured to be coupled to the battery 50 through connections 43, 44, and 45. Connection 44, however, is optional. Battery 50 is preferably a lead acid battery, although other types of batteries can be used. DC / DC module 40 is configured to provide DC power to battery 50 (thereby charging battery 50) when a desired 3-phase power supply is present at inputs 13, 23, and 33 (i.e., the state of charge). Similarly, the DC / DC module 40 is configured to provide one or more DC voltages, using power from the battery 50, to the AC / AC modules 10, 20, and 30 in the absence of a DC power supply. 3 phases desired on inputs 13, 23, and 33 (i.e. discharge status). The state in which the DC / DC module 40 is operating can be controlled by a controller (not shown) that is configured to control, for example, the 3-phase AC input. The DC / DC converter 41

ES 2 553 007 T3 is configured, in the charging state, to receive a fixed DC voltage from the AC / AC modules 10, 20, and 30 and to convert the DC voltage is set to a DC battery charging voltage desired by the battery 50. The DC / DC 41 is further configured to, during the discharge state, receive DC power from the battery 50 at the charging battery voltage, and to convert it to the DC voltage set. The DC / DC converter 41 is configured to provide the DC voltage across the AC / Ac modules 10, 20, and 30 during the discharge state. The DC / DC converter 41 is coupled to the DC bus balancer 42 via buses 60, 61, 62, 63 and

64. DC bus balancer 42 is configured to balance voltages present on buses 60, 61, 62, 63, and 64, as will be described in more detail below.

[0014] UPS 5 is configured to determine if adequate input power is present at the inputs to AC / AC modules 10, 20 and / or 30. UPS 5 can detect the presence of adequate power at the inputs to AC / AC modules using one or more methods and / or circuits. For example, UPS 5 may include circuitry configured to determine if an AC voltage present at inputs 13, 23, 33, if any, is at a desired level. The UPS 5 can also include circuits configured to monitor in which state the DC / DC converter 41 is operating (for example, charging or discharging state) and if a direct voltage is present on buses 60, 61, 63 and / or or 64. For example, if the DC / DC converter 41 is operating in the state of charge, and the respective DC voltage on buses 60, 61, 63 and / or 64 falls below a respective desired level, the circuits may provide a signal which indicates that the alternating voltage supplying the AC / AC converters 11, 21 and 31 has dropped below the desired levels. Other methods and / or circuits can be used to detect if the AC input voltage is below desired levels. UPS 5 is further configured to disconnect from 3-phase power supply (for example, by setting switches (as described below) for off positions).

[0015] The pulse width modulation (PWM) controllers are configured to control the operation of at least some of the components in the UPS 5. For example, separate PWM controllers can be used for the AC / DC converters 11, 21 and 31, the DC / AC converters 12, 22, and 32, the DC / DC module 41, and the DC bus balancer 42, although other configurations are possible. For example, separate PWM controllers that have the same physical configuration, but using different control signals can be used, or alternatively, PWM controllers that have non-identical physical configurations can be used. The PWM controller can be configured to control the switching of a portion of the switches as a function of the frequency and phase of the AC input signal (for example, using a feedback loop), or it can be adjusted according to a desired output (for example, to provide power of a desired frequency and phase to a load coupled to DC / AC converters 12, 22, and 32.

With reference to the figure. 2, an AC / DC converter 200 (for example, an example of the AC / DC converters 11, 21, and 31) includes diodes 205, 215, 225, 235, 245, and 255, switches 210, 220, 230, 240, 250, and 260 (S1, S2, S3, S4, S5, S6), a capacitor 280, and an inductor 285. Switches 210, 220, 230, 240, 250, and 260 are isolated bipolar transistors (IGBTs), although other switches can be used. Preferably, switches 210, 220, 250, and 260 have a maximum voltage rating of 600V and switches 230 and 240 have a maximum voltage rating of 1200V, although other ratings are possible. An input 202 is configured to be coupled to, for example, a phase of the 3-phase power supply (for example, phase X). Coupled between input 202 and a ground connection is capacitor 280. A node 286 of inductor 285 is also coupled to input 202. Coupled to a node 287 of inductor 285 is an anode 227 of diode 225, an emitter 232 of switch 230, a cathode 236 of diode 235, and a collector 241 of switch 240. A cathode 226 of diode 225 is coupled to collector 231 of switch 230. An anode 237 of diode 235 is coupled to emitter 242 of switch 240. Cathode 226, collector 231, anode 207 of diode 205, emitter 212 of switch 210, cathode 216 of diode 215, and collector 221 of switch 220 are coupled together. Anode 237, emitter 242, anode 247 of diode 245, emitter 252 of switch 250, cathode 256 of diode 255, and collector 261 of switch 260 are coupled to each other. A cathode 206 of diode 205 and a collector 211 of switch 210 are coupled to an output 235. An anode 217 of diode 215 and an emitter 222 of switch 220 are coupled to an output 240. A cathode 246 of diode 245 and a collector 251 of switch 250 are coupled to an output 245. An anode 257 of diode 255 and a Emitter 262 of switch 260 are coupled to an output 250. Gates 213, 223, 233, 243, 253, and 263 of switches 210, 220, 230, 240, 250, and 260, respectively, are each coupled to a pulse width modulation controller 275 as will be described. in more detail below. Outlets 265, 266, 267, and 268 are configured to be coupled to buses, 64, 63, 61, and 60, respectively. The inductor 258 preferably has an inductance of 100 uH, although other inductances can be used (for example, depending on the nominal power of the system 5). The capacitor preferably has a capacity of 200 uF, although other capacities can be used (for example, depending on the nominal power of the system 5).

The AC / DC converter 200 is configured to receive AC power from, for example, a 3-phase power connection phase to provide a multi-level direct current output through outputs 265, 266, 267 , and 268. For example, when the AC / DC converter 200 is running and input 202 is coupled to a 480 VAC power supply, the AC / DC converter 200 can induce a voltage (relative to a neutral connection of the power supply). voltage) of about 450 VDC across output 265 and neutral connection, a voltage of about 150 VDC across output 266 and neutral, a

ES 2 553 007 T3 voltage of about -150 VDC across output 267 and neutral, and a voltage of about -450 VDC across output 268 and neutral. Similarly, the AC / DC converter 200 is configured to induce a voltage of about 300 VDC through outputs 265 and 266 (V1), outputs 266 and 267 (V2), and outputs 267 and 268 ( V3).

Preferably, the induced voltage at outputs 265 and 268 is a function of the input voltage. The induced voltage at outputs 265 and 268 is preferably equal to or greater than the voltage across capacitor 280 multiplied by root). The voltage across capacitor 280 (i.e. phase-neutral voltage) is preferably substantially equal to (Input Voltage 202)_z —---—------_ (p_grab . Neutral Voltage) (1) (if a neutral connection is available) and the instantaneous peak voltage across capacitor 280 varies between ± (Phase - Neutral Voltage) (). Preferably, the AC / DC converter 200 is configured such that the supplied voltage at the output 265 is greater than the instantaneous positive peak voltage across the capacitor 280 and the voltage provided at the output 268 is less than the instantaneous voltage. negative peak across capacitor 280. For example, assuming a 480 V input at input 202, the neutral phase is approximately 277 Vrms, and the instantaneous peak voltage across capacitor 280 is approximately 392 V. Therefore, in this example, the converter AC / DC 200 is configured so that output 265 outputs a voltage of approximately 392 V or higher (for example, 450 V) and output 268 outputs a voltage of about -392 or less (for example, -450 V ). Increasing the difference between the absolute value of the output at output voltages 265 and 268 and the absolute value of the instantaneous peak voltages across capacitor 280 can increase the operating tolerance of system 5.

[0019] The combination of capacitor 280, inductor 285, and switches 210, 220, 230, 240, 250, and 260 is configured to act as a boost converter and to convert the AC signal that is supplied to input 202 in a quasi-square four-level waveform (eg, as shown as a signal 305 in Fig. 8) at node 287 of inductor 285. The voltage at node 287 can vary depending on the state of switches 210, 220, 230, 250, 260 (as more fully described below). For example, when the instantaneous value of the AC voltage present at input 202 is between a first voltage level equal to the DC voltage at node 265 (for example, 450 V, as determined by the configuration of the AC / DC 200) and a second voltage level equal to the DC voltage at node 266 (for example, 150 V), the square wave at node 287 of inductor 285 oscillates between these values ​​(in this case 450 V and 150 V ); when the instantaneous value of the AC voltage present at input 202 is between the second voltage level equal to the DC voltage at node 266 and a third voltage level equal to the DC voltage at node 267 (for example, - 150 V), the square wave at node 287 of inductor 285 oscillates between these values ​​(eg, -150 V and -150 V); and when the instantaneous value of the AC voltage present at input 202 is between the third voltage level equal to the DC voltage at node 267 and a fourth voltage level equal to the DC voltage at node 268 (for example, -450 V), the square wave at node 287 of inductor 285 oscillates between these values ​​(eg, -150 V and -450 V). Also, the combination of capacitor 280 and inductor 285 is configured to act as a low pass filter.

The AC / DC converter 200 is configured to induce voltages at outputs 265, 266, 267, and 268 by switching switches 210, 220, 230, 240, 250, and 260. The switches are configured to be driven by PWM controller 275. PWM controller 275 is configured to control switches 210, 220, 230, 240, 250, and 260, depending on which of the three states the AC / DC converter 200 is operating in. Also referenced to the figure. 3, the AC / DC converter 200 is configured to operate in three states. The first state corresponds to when the input voltage received by input 202 is above one third of the voltage provided by output 265 (for example, if the maximum input voltage is 6450 VAC, then the first state corresponds to when input is above 150V). The second state corresponds to when the input received by input 202 is between one-third of the voltage provided by output 265, and one-third of the voltage provided by output 268 (eg, 150V and -150V). The third state corresponds to when the input received by input 202 is below one third of the voltage provided by output 268 (for example, below -150 V). With reference also to the figure. 4, the PWM controller 275 is configured such that during the first state of switches 230 and 250 are set to their on (conductive) state, switches 240 and 260 are set to their off (non-conductive) state, and switches 210 and 220 oscillate between their off and on states (Fig. 4A). The PWM controller 275 is configured such that during the second state, switches 220 and 250 are on, switches 210 and 260 are off, and switches 230 and 240 are oscillating (Fig. 4B). The PWM controller 275 is configured such that during the third state, switches 220 and 240 are on, switches 210 and 230 are off, and switches 250 and 260 are rocking (Fig. 4C).

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With reference to the figures. 5-6, PWM controller 275 is configured to control switches 210, 220, 230, 240, 250, and 260, using control signals. The 275 PWM controller includes comparators 505, 515, and 525, and logic inverters 510, 520, and 530. The PWM controller 275 is configured to cause the AC / DC converter 200 to operate in the states described herein in order to convert an incoming AC signal to the DC signals described herein. A positive input 506 of comparator 505 is coupled to a sinusoidal modulation signal source (to receive a signal 605), and a negative input 507 of comparator 505 is coupled to a first PWM carrier signal 610. A positive input 516 of comparator 515 is coupled to the sinusoidal modulation signal, and a negative input 517 of comparator 515 is coupled to a second carrier PWM signal 615. A positive input 526 of comparator 525 is coupled to the sinusoidal modulation signal , and a negative input 527 of comparator 525 is coupled to a third PWM signal 620. An output 508 from comparator 505 is coupled to switch 210, and switch 220 through logic inverter 510. An output 518 from comparator 515 is coupled to switch 230 and switch 240 through logic inverter 520. An output 528 from comparator 525 is coupled to switch 250 and switch 260 through logic inverter 530.

[0022] The control signals used by the PWM controller 275 have been selected to achieve the desired switching pattern of switches 210, 220, 230, 240, 250, and 260. Signals 605, 610, 615, and 620 are preferably low voltage, generated, for example, by a wave generator. Sine wave signal 605 is a sinusoidal signal having a frequency and phase approximately equal to the frequency and phase of the power supply provided to input 202. Sine wave signal 605 has a peak amplitude approximately equal to a threshold 625, which can be of various values, for example 1V. The first PWM carriers 610, 615, and 620 are triangle waves having a frequency substantially equal to the desired PWM switching frequency of the AC / DC converter 200, although other frequencies are possible. The PWM switching frequency of the AC / DC converter 200 is preferably chosen as a midpoint between the IGBT switching losses and the physical size and cost of the input and output coils and capacitors (e.g., capacitor 280 (C5) and inductor 285). A maximum value of the PWM control signal 610 is approximately equal to the threshold of 625 and a minimum value of the first PWM control signal 610 is approximately equal to one third of the threshold 625. A maximum, the value of the PWM control signal 615 is approximately equal to one third of the threshold of 625 and a minimum value of the PWM control signal 615 is approximately equal to the negative of one third of the threshold 625. A maximum value of the PWM control signal 620 is approximately equal to the negative one-third of the threshold 625 and a minimum value of the PWM control signal 620 is approximately equal to the threshold of 625 multiplied by -1.

[0023] PWM controller 275 is configured to switch switches 210, 220, 230, 240, 250, and 260 using modulation sine wave signal 605 and PWM control signals 610, 615, and 620. As the sine wave modulation signal 605 varies, the comparator 505 will output either a logic one or a logic zero, corresponding to which is greater than the positive input 505 or the negative input 507. Comparator 505 is configured to output a ceri logic one if the positive input 506 is greater than the negative input 507, (for example, the voltage of the sine wave modulation signal 605 is greater than the voltage of the PWM control signal 610). Similarly, the comparator 505 is configured to output a logic zero if the positive input 506 is less than the negative input 507, the voltage of the sine wave modulation signal 605 is less than the voltage of the PWM control signal. 610). While the above discussion has focused on the operation of comparator 505, the operation of comparators 515 and 525 is preferably similar. Preferably, the PWM controller 275 is configured to insert small dead bands such that there is a slight delay between the disconnection of any given switch and the connection of another switch (for example, to protect against unwanted pairs of the switches being fit simultaneous). Switches 210, 220, 230, 240, 250, and 260 are configured such that a logic 1 turns the switch on, while a logic 0 turns the switch off, although the reverse is possible.

[0024] The PWM controller 275 can be configured to vary the duty cycle in which the switches it controls are toggled. For example, using signals 610, 615, 620, and 625, the duty cycle of switches that are repeatedly alternating is varied (eg, in the first state, switches 210 and 220). When comparing intervals 630 and 635, which indicate when switch 210 is on and switch 220 is off, interval 630 is greater than interval 635.

[0025] Referring back to the figure. 2, examples of the operation of the AC / DC converter 200 will be described. The AC / DC converter 200 is configured to provide the respective DC voltages to outputs 265, 266, 267, and 268, acting as a boost converter. For example, in the first state when switch 220 is on and switch 210 is off, inductor 285 will store energy. When switch 220 is off, energy stored in inductor 285 causes current to freely pass through diode 205. In the second state, when switch 230 is on and switch 240 is off, inductor 285 will store energy. When switch 230 is off, inductor 285 causes a freewheel current through diode 235. In the third state, when switch 250 is on, and switch 260 is off, inductor 285 will store energy. When switch 250 is off, energy stored in inductor 285 (L1) causes current to pass freely through diode 255.

ES 2 553 007 T3

With reference to the figures. 2 and 7, a DC / AC converter 700 (eg, an example of the DC / AC converters is 12, 22, and 32) includes diodes 705, 715, 725, 735, 745, and 755; switches 710, 720, 730, 740, 750 and 760, inputs 765, 766, 767 and 768; a filter 770, and an output 702. Switches 710, 720, 730, 740, 750, and 76th are IGBTs although other transistors can be used. Inputs 765, 766, 767, and 768 are configured to receive DC power from, for example, AC / DC converter 200. Coupled to output 702 is anode 727 of diode 725, emitter 732 of switch 730, a cathode 736 of diode 735, and a collector 741 of switch 743. A cathode 726 of diode 725 is coupled to collector 731 of switch 730. An anode 737 of diode 735 is coupled to emitter 742 of switch 740. Cathode 726, collector 731, anode 707 of diode 705, emitter 712 of switch 710, cathode 716 of diode 715, and collector 721 of switch 720 are coupled to each other. Anode 737, emitter 742, anode 747 of diode 745, emitter 752 of switch 750, cathode 756 of diode 755, and collector 761 of switch 760 are coupled to each other. A cathode 706 of diode 705 and a collector 711 of switch 710 are coupled to input 765. An anode 717 of diode 715 and an emitter 722 of switch 720 are coupled to input 766. A cathode 746 of diode 745 and a collector 751 of switch 750 are coupled to input 767. An anode 757 of diode 755 and an emitter 762 of switch 760 is coupled to input 768. Bases 713, 723, 733, 743, 753, and 763 of switches 7iso, 720, 730, 740, 750, and 760 (S7, S8, S9, S10, S11, S12), respectively, are each coupled to a pulse width modulation controller, as will be described in more detail below. Emitter 732 of switch 730, anode 727 of diode 725, collector 741 of switch 740, and cathode 736 of diode 735 (ie, definition of node 772) are coupled to filter 770. Filter 770 includes inductor 785 and capacitor 790 (C6). Inductor 785 (L2) is coupled between node 772 and output 702. Capacitor 790 is coupled between output 702 and ground. The inductor 785 preferably has an inductance of 100 mH, although other inductors can be used (eg, depending on the nominal power of system 5). Capacitor 790 preferably has a capacity of 200 mF, although other capacities can be used (eg, depending on the nominal power of system 5).

[0027] The DC / AC converter 700 is configured to receive DC power from, for example, the AC / DC converter 200, and to provide an AC output through output 702. For example, when the DC converter / AC 700 is in operation, and inputs 765, 766, 767, and 768 are coupled to outputs 265, 266, 267, and 268, respectively, of the AC / DC converter 200, an AC output can be induced at exit 702. The DC A / AC converter 700 is configured to induce at output 702 an AC output that has peak voltages (for example, relative to the neutral connection) approximately equal to the voltages present at input 765 (for example, a positive peak signal voltage at output 702) and input 768 (eg, a negative peak signal voltage at output 702). Other voltages, however, can be induced.

[0028] The DC / AC converter 700 can be realized as a voltage or a controlled current DC / AC converter. Preferably, an external voltage loop is used to maintain a desired voltage when operating the DC / AC converter 700 using current control. For example, a control circuit (not shown) can be configured to control current flow in inductor 785 and to control the voltage present at output 702 (eg, to determine if the output is sinusoidal). The control circuit can be configured to adjust a PWM signal supplied to switches 710, 720, 730, 740, 750, and 760, based on the measured current and voltage values ​​to maintain the desired output voltage. The DC / AC converter 700 can be configured to be operated with a fixed or variable PWM frequency, as described herein.

[0029] The DC / AC converter 700 is configured to convert the DC voltages present at the inputs 765, 766, 767, and 768 into an AC output voltage by changing the switches 710, 720, 730, 740, 750, and 760. The switches are configured to be actuated by a PWM controller 775 which is preferably configured in a similar manner to the PWM controller 275. The control signals provided to the PWM controller 775 may be similar to those provided to the PWM controller 275, although the frequencies and / or amplitudes of the control signals may vary to produce a desired output for a load coupled to output 702. Preferably, the DC / AC converter 700 is configured such that that in any given part of a line cycle (for example, a cycle through the first, second, and third states) two of the six switches 710, 720, 730, 740, 750 and 760 are turned on in a complementary manner, while the remaining four switches are either constantly off or constantly on.

[0030] With reference also to the figure. 8, the 775 PWM controller can make the 700 DC / AC converter operate in three states. The first state corresponds to times when the output voltage provided at output 702 is above one third of the voltage provided at input 765 (for example, the voltage at the input is 450 V, then the first state corresponds to times when the output is above 150V). The second state corresponds to the times when the output is provided at output 702, being between one third of the voltage provided at input 765 and one third of the voltage provided at input 768 (for example, -150 V and 150 V). The third state corresponds to times when the output voltage provided at output 702 is below one third of the voltage provided at input 768 (eg, below -150 V). The PWM controller 775 is configured such that during the first state, switches 730 and 750 are on, switches 740 and 760 are off, and switches 710 and 720 are rocking (see Fig. 9A). The PWM controller 775 is configured so that during the second state, switches 720 and 750 are on, switches 710 and 760 are off, and switches 730 and 740 are rocking (Fig. 9B). The 775 PWM controller is configured as

ES 2 553 007 T3 such that during the third state, switches 720 and 740 are on, switches 710 and 730 are off, and switches 750 and 760 are oscillating (Fig. 9C). In the first state, the switching configuration of switches 710, 720, 730, 740, 750, and 760 is configured to cause a square wave voltage at node 780 that varies between 450 V and 150 V, with a cycle of variable work. For example, the duty cycle of the square wave can vary depending on what part of which state the DC / AC converter is operating in (for example, as the output voltage approaches 450 V in the first state, the cycle of wave square work is approaching 100%). In the second state, the switching settings of switches 710, 720, 730, 740, 750, and 760 are set to cause a square wave voltage at node 780 that varies between 150 V and -150 V, with one cycle variable work. In the third state, the switching settings of switches 710, 720, 730, 740, 750, and 760 are set to cause a square wave voltage at node 780 that varies between -150 and -450 V, with one cycle variable work.

[0031] Filter 770 is configured to filter the output provided at node 772 at a substantially AC output voltage (310) that is provided to output 702. Filter 770 may be an LC low-pass filter, although others filter settings are possible.

With reference to the figure. 10, the AC / AC module 10 includes the AC / DC converter 200, the DC / AC converter 700, the capacitors 905, 910, 915, and 920 (C1, C2, C3, C4). Outputs 265, 266, 267, and 268 are coupled to inputs 765, 766, 767, and 768, respectively. Capacitor 905 is coupled between the junction of output 265 and input 765 and the junction of output 266 and input 766. Capacitor 910 is coupled between the junction of output 266 and input 766 and the neutral connection. Capacitor 915 is coupled between the neutral connection and the junction of output 267 and input 767. Capacitor 920 is coupled between the junction of output 267 and input 767 and the junction of output 268 and input 768. Also, the junction of output 265 and input 765 is coupled to the bus. 64. The junction of output 266 and input 766 is coupled to bus 63. The junction of output 267 and input 767 is coupled to bus 60. The junction of output 268 and input 768 is coupled to bus 61.

[0033] Capacitors 905, 910, 915, and 920 are configured to store energy for a short period of time when, for example, the frequency of the power signal supplied to input 202 differs from the frequency of the signal provided by output 702 and to reduce ripple current on buses 60, 61, 62, 63, and / or 64. The AC / AC module 10 is configured to, in operation, induce a 300 V potential across capacitors 905 and 920, and a 150 V potential across capacitors 910 and 915.

With reference to the figures. 1 and 11, a 1,000 DC / DC converter (e.g., an example of the DC / DC converter 41) is coupled to battery 50 and includes diodes 1005, 1015, 1025, and 1.035, switches 1010, 1020, 1030, and 1040, 1050, 1055, 1060, 1065 capacitors (C1a, C2a, C3a, C4a), 1070, and 1075 capacitors (C7, C8), and 1080 and 1085 coils (L3, L4). Switches 1010, 1020, 1030, and 1040 (S13, S14, S15, S16) are preferably IGBTs, although other switches can be used. Preferably, the diodes are fast or reverse ultrafast recovery diodes (eg, as can be used in other parts of the system 5). A cathode 1006 of diode 1005 is coupled to collector 1011 of switch 1010, and is further coupled to node 1090. An anode 1007 of diode 1005, an emitter 1012 of switch 1010, a cathode 1016 of diode 1015 and a collector 1021 of switch 1020 are coupled together. An anode 1017 of diode 1015 and an emitter 1022 of switch 1020 are coupled together, and are further coupled to node 1091. A positive terminal of capacitor 1051 1050 is coupled to node 1090 and a negative terminal 1052 of capacitor 1050 is coupled to node of 1091. Capacitor 1070 and inductor 1080 are coupled between anode junction 1007, emitter 1012, cathode 1016, and collector 1021 and node 1092. Preferably, inductor 1080 is coupled to anode junction 1007, the emitter 1012, cathode 1016, and collector 1021, and capacitor 1070 is coupled to node 1092. A positive terminal 1056 of capacitor 1055 is coupled to node 1091, and a negative terminal 1057 of capacitor 1055 is coupled to node 1092. A cathode 1026 of diode 1025 is coupled to a collector 1031 of switch 1030, and is further coupled to node 1093. An anode 1027 of diode 1025, an emitter 1032 of switch 1030, a cathode 1036 of diode 1035, a collector of 1041 of switch 1040 are coupled together. An anode 1037 of diode 1035 and an emitter 1042 of switch 1040 are coupled to each other, and are further coupled to node 1094. A positive terminal 1066 of capacitor 1065 is coupled to node 1093 and a negative terminal 1067 of capacitor 1065 is coupled to node 1094. Capacitor 1075 and inductor 1085 are coupled between the junction of anode 1027, emitter 1032, cathode 1036 , and collector 1041 and node 1092. Preferably, inductor 1085 is coupled to the junction of anode 1027, emitter 1032, cathode 1036, and collector 1041, and capacitor 1075 is coupled to node 1092. A positive terminal 1061 of capacitor 1060 is coupled to node 1092, and negative terminal 1062 of capacitor 1060 is coupled to node 1093. Nodes 1090, 1091, 1092, 1093, and 1094 are configured to be coupled to buses 64, 63, 62, 61, and 60, respectively. The switches are configured to be coupled to an 1115 PWM controller. While capacitors 1050, 1055, 1060, and 1065 have been assigned different reference numbers in the figures, capacitors 1050, 1055, 1060, and 1065 can be capacitors 905, 910, 915, and 920, respectively.

[0035] The DC / DC converter 1,000 is configured to provide power and receive power from the 1095 and 1100 cells. The 1095 and 1100 batteries are coupled to the DC / DC converter 1,000 through breakers 1105 and

ES 2 553 007 T3

1110. A positive terminal 1096 of battery 1095 is coupled to the junction of capacitor 1070 and inductor 1080 through switch 1105. A negative terminal 1097 of battery 1095 is coupled to a positive terminal 1101 of battery 1100. A negative terminal 1102 Battery 1100 is coupled to the junction of capacitor 1075 and inductor 1085 through switch 1110. Optionally, negative terminal 1097 of battery 1095 and positive terminal 1101 of battery 1100 may be coupled to node 1092 to reduce the maximum voltage at the battery switches. Preferably, cells 1095 and 1100 are configured to receive and provide a voltage that is between the peak voltage of system 5 (e.g., the voltage present on bus 64) and one third of the peak voltage of system 5 ( for example, the voltage present on bus 63). For example, the 1095 and 1100 batteries can be configured to provide approximately 288 V.

The DC / DC converter 1000 is configured to operate in two states, a charge state and a discharge state. During the state of charge the DC / DC converter 1000 acts as a buck converter and receives a first DC voltage fixed to buses 60, 61, 63, and 64 to provide a voltage of a first level to batteries 1095 and 1110 . During the discharge state, the DC / DC converter 1000 receives DC power from a second level and provides a second DC voltage on buses 60, 61, 63, and 64, respectively. The first voltage set and the second voltage set can be substantially the same. The first DC voltage and the second DC voltage can be substantially the same. During the state of charge, the DC / DC 1000 converter actively charges the 1095 and 1100 batteries, and / or provides a floating charge (for example, to maintain a charge from a fully charged battery).

[0037] Switches 1010, 1020, 1030, and 1040 are configured to be controlled by a PWM controller 1115. Preferably, one configuration of the PWM controller 1115 is similar to the PWM controller 275, although other configurations are possible. Preferably, switches 1010 and 1040 are controlled to oscillate in a similar manner (e.g., both switches 1010 and 1040 are on at approximately the same time) and switches 1020 and 1030 are controlled to cycle in a similar manner (e.g. , switches 1020 and 1030 turn on at approximately the same time). If, however, the junction of negative terminal 1097 and positive terminal 1101 is coupled to node 1092, each of the switches 1010, 1020, 1030, 1040 can be switched independently. The 1115 PWM controller is configured to vary the charging voltage of the 1095 battery by varying the duty cycle of the switch 1010. Similarly, the 1115 PWM controller can vary the charging voltage of the 1110 battery by varying the duty cycle of the switch. 1040.

[0038] When the DC / DC converter 1000 is operating in the state of charge, the PWM controller 1115 makes the DC / DC converter 1000 operate as a buck converter by repeatedly switching switches 1010 and 1040 while holding switches 1020 and 1030 turned off. When switches 1010 and 1040 are turned on, the DC / DC converter 1000 voltages present at nodes 1090 and 1094 load inductors 1080 and 1085. When switches 1010 and 1040 are off, throttling currents (for example, caused by discharge from inductors 1080 and 1085) pass freely through diodes 1015 and 1025. The DC / DC converter 1000 is configured to lower the voltages present. on nodes 1090 and 1094 by varying the duty cycle in which switches 1010 and 1040 are turned on. For example, as the duty cycle of the switching signal provided by the PWM controller 1115 increases toward 1, the voltage provided to batteries 1095 and 1100 increases toward the voltage present at nodes 1090 and 1094. Capacitors 1070 and 1075 are configured to reduce ripple current by filtering high frequency components from the signal provided to the 1095 and 1110 batteries.

[0039] When the DC / DC converter 1000 is operating in the discharge state, the PWM controller 1115 causes the DC / DC Converter 1000 to function as a buck-boost converter, repeatedly turning on the switches 1020 and 1030 and holding the switches 1010 and 1040 off. For example, the DC / DC converter 1000 provides increased voltage from batteries 1095 and 1100 to nodes 1090 and 1094, and provides reduced voltage to nodes 1091 and 1093. When switches 1020 and 1030 are on, batteries 1095 and 1100 cause inductors 1080 and 1085 to store power. When switches 1020 and 1030 are off, the energy stored in inductors 1080 and 1085 (and the energy provided by batteries 1095 and 1100) is discharged (for example, a freewheel) through diodes 1005 and 1035, respectively. The DC / DC converter 1000 is configured to increase the voltage supplied by the batteries 1095 and 1100 to the desired level by varying the duty cycle in which switches 1020 and 1030 are turned on. For example, as the duty cycle of the switching signal provided by the PWM controller 1115 increases toward 1, the voltage provided at nodes 1090, 1091, 1093, and 1094 increases. The DC / DC converter 1000 is also configured to step down the voltage supplied by the 1095 and 1100 batteries and to provide the step down voltage to nodes 1091 and 1093. The DC / DC converter 1000 is configured to reduce the voltage to nodes 1091 and 1093 in a manner similar to that described above. Capacitors 1050, 1055, 1060, and 1065 are configured to filter the high-frequency components of the signals at nodes 1090, 1091, 1093, and 1094.

With reference to FIGS. 1 and 12, an example of the CC 42 bus balancer, here a 1200 DC bus balancer, includes capacitors 1205 (C1b), 1210 (C2b), 1215 (C3b), 1220 (C4b), 1225 (C9), and 1230 (C10), 1235 (S17), 1245 (S18), 1255 (S19), 1265 (S20), 1275 (S21), and 1285 (S22) switches, diodes 1240, 1250,

ES 2 553 007 T3

1260, 1270, 1280, and 1290, and 1295 (L5), 1300 (L6), and 1305 (L7) inductors. A positive terminal 1206 of capacitor 1205, a collector 1236 of switch 1235, and a cathode 1241 of diode 1240 are coupled to a node 1310. An emitter 1237 of switch 1235, an anode 1242 of diode 1240, a collector 1246 of switch 1245 , and a cathode 1251 of diode 1250 are coupled together. An emitter 1247 of switch 1245, an anode 1252 of diode 1250, a collector 1256 of switch 1255, and a cathode 1261 of diode 1260 are coupled together and are further coupled to a node 1311. An emitter 1257 of switch 1255, an anode 1262 of diode 1260, a collector 1266 of switch 1265, and a cathode 1271 of diode 1270 are coupled to each other. An emitter 1267 of switch 1265, an anode 1272 of diode 1270, a collector 1276 of switch 1275, and a cathode 1281 of diode 1280 are coupled to each other, and are further coupled to node 1313. An emitter 1277 of switch 1275, an anode 1282 of diode 1280, a collector 1286 of switch 1285, and a cathode 1291 of diode 1290 are coupled to each other. An emitter 1287 of switch 1285, and an anode 1292 of diode 1290 are coupled to each other, and are further coupled to node 1314. A positive terminal 1206 of capacitor 1205 is coupled to node 1310 and a negative terminal 1,207 of capacitor 1205 is coupled to node 1311. A positive terminal 1211 of capacitor 1210 is coupled to node 1311 and a negative terminal 1212 of capacitor 1210 is coupled to node 1312. A positive terminal 1216 of capacitor 1215 is coupled to node 1312 and a negative terminal 1217 of capacitor 1215 is coupled to node 1313. A positive terminal 1221 of capacitor 1220 is coupled to node 1313 and a negative terminal 1222 of capacitor 1220 is coupled to node 1314. Capacitor 1225 and inductor 1295 are coupled in series between the junction of diodes 1240 and 1250 and the junction of diodes 1260 and 1270. Inductor 1300 and capacitor 1230 are coupled between the junction of diodes 1260 and 1270 and the junction of diodes 1280 and 1290. Therefore, capacitor 1225, inductor 1295, inductor 1300, and capacitor 1230 are coupled in series between the junction of diodes 1240 and 1250 and diodes 1280 and 1290. Inductor 1305 is coupled between node 1312 and the junction of diodes 1260 and 1270. Inductor 1305, however, is optional. For example, if the AC / DC converters 11, 21, and 31 are configured to control an amount of power drawn from the AC input in the respective positive and negative half cycles. The DC bus balancer 1200 can be configured to reduce (and possibly eliminate) the desire to control power consumption at the AC input using the Ac / DC converters 11, 21 and 31 (for example, in order to balance buses 60, 61, 62, 63 and 64) by including inductor 1305. Combination 1225 and inductor 1295 define a resonant tank 1320, and the combination of capacitor 1230 and inductor 1300 defines a resonant tank 1325.

[0041] A PWM controller 1315 is coupled to each of the switches 1235, 1245, 1255, 1265, 1275, and 1285. The PWM controller 1315 is preferably configured in a similar manner to the PWM controller 275. For example, the PWM controller 1,315 includes multiple comparators that are each configured to receive multiple control signals. The control signals are selected in such a way that the desired switching sequence is obtained (eg, as described herein on the DC bus balancer 42). The PWM controller 1315 is configured to provide control signals that preferably have a constant frequency and duty cycle, although other configurations are possible. The control signals provided to switches 1235, 1255, and 1275 are preferably substantially identical, and the control signals provided to switches 1245, 1265, and 1285 are preferably substantially identical. The control signals preferably have a duty cycle of about 50%, although other duty cycles are possible. With reference also to the figure. 13, the PWM controller 1315 is configured to insert dead time between the switching of the 1235, 1245, 1255, 1265, 1275, and 1285 switches such that the switches that are turned off are substantially completely off before the others switches turn on. The use of time-out, however, is optional. PWM controller 1315 is configured to provide a control signal such that switches 1235, 1245, 1255, 1265, 1275, and 1285 switch at a frequency approximately equal to a resonant frequency of resonant tanks 1320 and 1325, although other frequencies are possible.

The DC bus balancer 1200 is configured to balance and maintain the desired voltages on buses 60, 61, 62, 63 and 64 by moving the energy stored in capacitors 1205, 1210, 1215 and 1220 on buses 64, 63 , 61, and 60, as appropriate. Switches 1235, 1245, 1255, 1265, 1275, and 1285 are configured to be changed by PWM controller 1315. PWM controller 1315 is configured to control the switches to be first and second states. In the first state, the 1235, 1255, and 1275 switches are on, while the 1245, 1265, and 1285 switches are off. In the second state, switches 1235, 1255, and 12C are off while switches 1245, 1265, and 1285 are on. Due to these switching states, the voltages within the DC 1200 bus balancer oscillate as shown in Table 1.

<td>binding of</td><td>First State Voltage</td><td>Second State Voltage</td>

<td>Switches 1235 and 1245</td><td>Switches in node 1310</td><td>Voltage at node 1311</td>

<td>1255 and 1265 switches</td><td>Switches in node 1311</td><td>Voltage at node 1313</td>

<td>1275 and 1285 switches</td><td>Switches in node 1313</td><td>Voltage at node 1314</td>

Therefore, when nodes 1310, 1311, 1313, and 1314 provide 450 V, 150 V, -150 V, and -450 V, respectively, then each of the junctions described in Table 1 alternate by approximately

ES 2 553 007 T3

300 V (peak to peak). The remainder of the DC 1200 bus balancer discussion assumes that buses 64, 63, 61, and 60 provide 450 V, 150 V, -150 V, and -450 V, respectively (relative to neutral).

[0043] During balanced operation of the DC bus balancer 1200 (for example, the voltages at nodes 1310, 1311, 1312, 1313, and 1314 are at the desired levels), the signal present at each of the junctions described in Table 1 it is substantially square. Furthermore, during balanced operation, the voltage swings at the junctions described in Table 1 will be substantially in phase with each other and have substantially the same amplitude. The voltage differences across resonant tanks 1320 and 1325 are preferably approximately equal to one third of the total voltage between DC bus 60 and 64 (eg, 300 V). Capacitors 1225 and 1230 are configured to charge to the potential placed across resonant tanks 1320 and 1325, respectively (eg, 300V).

[0044] The balancer bus VDC 1200 is configured to compensate for unbalanced voltages at nodes 1310, 1311, 1312, 1313, 1314 and using the energy stored in resonant tanks 1320 and 1325. During unbalanced operation of the DC 1200 bus balancer, the amplitude of the square wave voltages induced across the junctions described in Table 1 can be uneven, which can cause a square wave voltage to appear across one or more of resonant tanks 1320 and 1325. Each of the resonant tanks 1320 and 1325 are configured such that, as a voltage appears across the resonant tanks 1320 and 1325, a current flows through each of the resonant tanks 1320 and 1325. The resonant tanks 1320 and 1325 are configured to have a low impedance (for example, approaching zero) such that even a small voltage potential across each of the resonant tanks 1320 and / or 1325 can cause a large current flow. through resonant tanks 1320 and / or 1325. The impedance of the resonant tanks 1320 and 1325 can be a function of the frequency at which the 1235, 1245, 1255, 1265, 1275, and 1285 switches are turned on (or vice versa). For example, as the switching frequency approaches equal to the resonant frequency of resonant tanks 1320 and 1325, the impedance of resonant tanks 1320 and 1325 approaches zero. Resonant tanks 1320 and 1325 are configured to allow current to flow that can move energy from capacitors 1205, 1210, 1215, and / or 1220 that have voltage (s) higher than the preferred voltage levels of 300 V and 150 V, respectively, towards capacitors that have voltage (s) lower than the preferred voltage levels. Switches (for example, of switches 1235, 1245, 1255, 1265, 1275, and 1285) that are coupled across the capacitor (for example, of capacitors 1205, 1210, 1215, and / or 1220) that has the Higher voltages are configured to act as a generator and create an alternating current through resonant tanks 1320 and / or 1325 to establish actual power flow to the capacitor (e.g. from capacitors 1205, 1210, 1215, and / or 1220) that has the lowest voltage. DC bus balancer 1200 is configured such that current flow through resonant tanks 1320 and 1325 preferably starts when the voltage difference between the unbalanced capacitors exceeds a voltage drop of the respective diodes 1240, 1250 , 1260, 1270, 1,280, and 1290 (for example, a few volts). Preferably, as the frequency at which switches 1235, 1245, 1255, 1265, 1275, and 1.285 are switched approximates the resonant frequency of resonant tanks 1225 and 1230, zero crossings of the induced current occur closer to time. dead between the first and second states, which can reduce switching losses.

[0045] In operation, referring to Figure 14, with further reference to Figures 1-13, a process 1400 for providing an uninterruptible source of power to a load using UPS 5 includes the stages shown. The 1400 process, however, is exemplary only and not limiting. Process 1400 can be altered, for example, by adding, deleting, modifying, or rearranging the steps. Also, while portions of the process 1400 are shown as successive stages, certain stages may occur in parallel (eg, stages 1435 and 1440).

In step 1405, the UPS 5 is coupled to a 3-phase power supply. AC / AC modules 10, 20, and 30 are coupled to phases X, Y, and Z of the 3-phase power supply, respectively. AC / AC modules 10, 20, and 30 are further coupled to a neutral connection of the 3-phase power supply. The power supply provides 3-phase AC power for the UPS 5.

In step 1410, the UPS 5 is coupled to one or more loads. The UPS 5 can be coupled to a 3 phase load (for example, the AC / AC module 10 provides phase X, the AC / AC module 20 provides phase Y, and the AC / AC module 30 provides phase Z ). Alternatively, the UPS 5 can be coupled to one or more single phase loads. For example, each of the AC / AC modules 10, 20, and 30 can provide single phase power to one or more loads.

[0048] In step 1415, the UPS 5 determines if the AC power is acceptable. If UPS 5 determines that the AC input power is acceptable, then process 1400 proceeds to step 1420. If UPS 5 determines that the input power is unacceptable, for example, it has stopped and / or turned unstable (eg, a low voltage condition), then process 1400 proceeds to step 1430.

In step 1420, the AC / DC modules 11, 21, and 31 convert the input AC power to DC power, which is provided to buses 60, 61, 63, and 64. The AC / DC modules DC 11, 21 and 31 are initialized

ES 2 553 007 T3 (for example, the switches are switched to the state corresponding to a power signal) at startup or at a suitable power that is provided to the UPS 5. Although the following discussion focuses on the AC / DC 11, the operation of the AC / DC modules 21 and 31 can be similar. The AC / DC module 11 processes the input AC power using a combined low-pass filter and boost converter (ie, the combination of capacitor 280 and inductor 285). The PWM controller 275 toggles switches 210, 220, 230, 240, 250, and 260 as a function of the power signal that is received by the AC / DC module 11. For example, the PWM controller 275 makes the switches 210, 220, 230, 240, 250, and 260 operate in one of three states. In the first state, the PWM controller 275 toggles switches 210 and 220 in a mutually exclusive manner, keeping switches 230 and 250 in an on position, and keeping switches 240 and 260 in an off position. In the second state, PWM controller 275 holds switches 210 and 260 in an off-center position, holds switches 220 and 250 in an on position, and switches switches 230 and 240 in a mutually exclusive manner. In the third state, the PWM controller holds switches 210 and 230 in an off-center position, holds switches 220 and 240 in an on position, and switches switches 250 and 260 in a mutually exclusive manner. The PWM controller 275 causes the AC / DC converter 11 to operate in the first state when the AC input that is supplied to the AC / DC module 11 is greater than one third of the voltage provided at the output 265. The controller 275 causes the AC / DC converter PWM 11 to operate in the second state when the AC input provides the AC / DC module 11 with between one-third of the voltage provided at output 265 and one-third of the voltage provided at exit 268. The PWM controller 275 causes the AC / DC converter 11 to operate in the third state when the AC input that is supplied to the AC / DC module 11 is below one third of the voltage provided at the output 268.

In step 1425, the DC / DC converter 1000 charges the battery 50. The DC / DC converter 1000 receives a first set of continuous voltages from buses 60, 61, 63 and 64. When the UPS 5 receives adequate power From the power supply, the DC / DC converter 1000 converts the first set voltage to a first DC voltage that is supplied to the battery 50. The voltage provided to battery 50 is between the voltage present on bus 64 and one third of the voltage provided on bus 64.

[0051] The PWM controller 1115 causes the DC / DC converter 1000 to act as a Buck converter, converting the first set of set voltage to the first voltage. PWM controller 1115 causes switches 1020 and 1030 to be held in an off position, while switches 1010 and 1040 turn off and on substantially simultaneously. Each time switches 1010 and 1040 are turned on, load inductors 1080 and 1085 and cells 1095 and 1100 receive a voltage that is substantially equal to the first voltage. Each time switches 1010 and 1040 are turned off, inductors 1080 and 1085 discharge (eg, freewheel current through diodes 1015 and 1025) and provide substantially the first voltage to batteries 1095 and 1100. Preferably, switches 1010 and 1040 are turned to an on position before inductors 1080 and 1085 are fully discharged.

In step 1430, the PWM controller 1115 causes the DC / DC converter 1,000 to act as a boost converter, converting the second voltage into the second voltage set. PWM controller 1115 causes switches 1020 and 1030 to turn on and off substantially simultaneously, while switches 1010 and 1040 are held in an off position. Each time switches 1020 and 1030 are turned on, inductors 1080 and 1085 charge using power from batteries 1095 and 1100. Each time switches 1020 and 1030 are turned off, inductors 1080 and 1085 discharge and a current is freewheeling across diodes 1005 and 1035 (for example, caused by energy stored in batteries 1095 and 1100 and inductors 1080 and 1085). Preferably, switches 1020 and 1030 are switched to an on state before inductors 1080 and 1085 are fully discharged. Capacitors 1070 and 1075 can be used to reduce the ripple current in the power supplied to nodes 1090, 1091, 1093, and 1094. In addition, the UPS switches are set to a state to receive DC power from battery 50 . For example, upon detecting that AC power supply is unavailable and / or unstable, connection 13 is decoupled from buses 64, 63, 61, and 60 by setting all switches on AC / DC modules 11 to an off position. Similarly, the operation of the AC / DC converters 21 and 31 is similar.

[0053] At stage 1435, the DC 1200 bus balancer balances the voltages present on buses 60, 61, 63, 64. While stage 1435 is shown as a stage placed between other stages, the DC 1200 bus balancing balances the voltages present on buses 60, 61, 63, and 64 in parallel with other stages during the operation of the UPS 5. The DC 1200 bus balancer balances and maintains the desired voltages on buses 60, 61, 62, 63, and 64 by moving stored energy in capacitors 1205, 1210, 1215, and 1220 on buses 64, 63, 61, and 60, as appropriate. The 1235, 1245, 1255, 1265, 1275, and 1285 switches are toggled by the 1315 PWM controller. The 1315 PWM controller toggles the 1235, 1245, 1255, 1265, 1275, and 1285 switches in the first and second states. In the first state, the 1235, 1255, and 1275 switches are on, while the 1245, 1265, and 1285 switches are off. In the second state the 1235, 1255 and 1265 switches are off, while the 1245, 1265 and 1285 switches are on. Voltages on the 1200 DC bus balancer alternate, as shown in Table 1 (see image above). For the

ES 2 553 007 T3 Therefore, when nodes 1310, 1311, 1313, and 1314 provide 450 V, 150 V, -150 V, and -450 V, respectively, each of the junctions described in Table 1 alternate by approximately 300 V (peak to peak). The remainder of the discussion of the DC 1435 bus balancer stage assumes that buses 64, 63, 61, and 60 provide 450 V, 150 V, -150 V, and -450 V, respectively (relative to neutral).

[0054] During balanced operation of the DC bus balancer 1200 (for example, the voltages at nodes 1310, 1311, 1312, 1313, and 1314 are at the desired levels), the signal present at each of the junctions described in Table 1 it is substantially square. Therefore, during balanced operation, the voltage swings at the junctions described in Table 1 will be substantially in phase and have substantially the same amplitude. The voltage differences across the resonant tanks 1320 and 1325 are approximately equal to one third of the total voltage between the DC 60 bus and the bus (eg 300 V). Capacitors 1225 and 1230 charge to the potential placed across resonant tanks 1320 and 1325, respectively (eg, 300 V).

[0055] DC bus balancer 1200 compensates for unbalanced voltages at nodes 1310, 1311, 1312, 1313, 1314 and using stored energy in resonant tanks 1320 and 1325. During unbalanced operation of the DC 1200 bus balancer, the amplitude of the square wave voltages induced across the junctions described in Table 1 may be uneven, which can cause a square wave voltage to appear across one or more of resonant tanks 1320 and 1325. Since a voltage appears across each of resonant tanks 1320 and / or 1325, current flows through each of resonant tanks 1320 and / or 1325, respectively. The amount of current flowing in resonant tanks 1320 and / or 1325 can be increased by reducing the impedance of resonant tanks 1320 and 1325 (eg, near zero impedance). The PWM controller 1315 switches switches 1,235, 1,245, 1,255, 1,265, 1,275, 1,285 and at a frequency such that the impedance of resonant tanks 1320 and 1325 is reduced. For example, as the switching frequency approaches equal to the resonant frequency of resonant tanks 1320 and 1325, the impedance of resonant tanks 1320 and 1325 approaches zero. When a voltage is present across resonant tanks 1320 and 1325 a current flows from the capacitor that has the highest voltage (for example, from capacitors 1205, 1210, 1215, and 1220) to the capacitor that has the highest voltage. low (for example, from capacitors 1205, 1210, 1215 and 1220). Switches (for example, of switches 1235, 1245, 1255, 1265, 1275, and 1285) that are coupled across the capacitor that has the highest voltage (for example, of capacitors 1205, 1210, 1215, and 1220 ) acts as a generator and creates an alternating current through resonant tanks 1320 and / or 1325 to establish actual power flow to the capacitor (for example, from capacitors 1205, 1210, 1215, and 1220) that has the lower voltage. Current flow through resonant tanks 1320 and 1325 preferably begins when the voltage difference between the unbalanced capacitors exceeds a voltage drop of the respective diodes 1240, 1250, 1260, 1270, 1280, and 1290 (e.g. , a few volts).

[0056] An induced current waveform flowing in resonant tanks 1225 and 1230 (eg, caused by unbalanced operation of DC bus balancer 1200) is similar to a sine wave. Preferably, as the frequency that switches 1235, 1245, 1255, 1265, 1275, and 1.285 are switched to approximates the resonant frequency of resonant tanks 1225 and 1230, zero crossings of the induced current occur further. close to the dead time between the first and second states, which can reduce switching losses.

In step 1440, direct current on buses 60, 61, 63, and 64 is converted to AC power by DC / AC converters 12, 22, and 32. Each of DC / AC converters 12 , 22, and 32 are preferably configured as DC / AC converter 700. DC / AC converter 700 receives power from AC / DC converter 200, or battery 50 via buses 60, 61, 63, and 64. The DC / AC converter 700 generates an AC output having peak voltages approximately equal to the voltages present at input 765 and input 768. One phase of each of the DC / AC converters 12, 22, and 32 are preferably varied from such that standard 3 phase power can be provided to one load.

With reference also to Figs. 9-10 the DC / AC converter 700 converts DC power from AC power by switching switches 710, 720, 730, 740, 750, and 760 in a predetermined sequence. The 775 PWM controller toggles switches 710, 720, 730, 740, 750, and 760 in different sequences, depending on the desired output at output 702. When the desired output (at output 702) is between the voltages present at inputs 765 and 766, the PWM controller 775 actively toggles switches 710 and 720 and turns off, setting it on switches 730 and 750 to a position On, and sets switches 740 and 760 to an off position. When the desired output (at output 702) is between the voltages present at inputs 766 and 767 the PWM controller 775 actively switches switches 730 and 740 on and off, sets switches 720 and 750 to an on position , and sets switches 710 and 760 to an off position. When the desired output (at output 702) is between the voltages present at inputs 767 and 768, the PWM controller 775 actively toggles switches 750 and 760 and off, sets switches 720 and 540 to an on position, and switches 710 and 730 to an off position. In each of the three states, the duty cycle of switches 710, 720, 730, 740, 750, and 760 that are being actively changed was varied such that the

ES 2 553 007 T3 output of filter 770 is substantially AC (eg, as shown in Figures 9-10). Filter 770 (eg, an LC low pass filter) filters the signal provided at node 780 into a substantially AC signal that is provided to output 702.

[0059] In step 1445 AC power is provided to a load. The configuration of the power that is supplied to the load may vary depending on the desired operation. For example, each of the DC / AC converters 12, 22, and 32 can provide one phase of a 3-phase power connection, all or part of the converters is DC / AC 12, 22, and 32 can provide single phase power, each of the DC / AC converters 12, 22, and 32 can provide single phase power to individual loads, etc.

[0060] For example, due to the nature of software, the functions described above can be implemented using software, hardware, firmware, cabling, or combinations of any of these. Function application features can also be physically located in various locations, including being distributed in such a way that the function portions are implemented in different physical locations. While three DC / AC converters are shown (eg DC / AC converters 12, 22, 32 and 42) a single DC / AC converter can be used if single phase power is desired. AC / DC and DC / AC converters can be divided into several parallel circuits and interleaved switches, for example to reduce ripple current on buses. The voltages present on buses 61, 62, 64, and 65 may be different from that described in this document. A battery can be coupled directly to buses 61, 63, and / or 64, without the use of a DC / DC converter.

[0061] Although the description herein describes numerous separate capacitors, two or more capacitors can be combined into a single capacitor. For example, FIG. 10 shows capacitor 905 coupled between bus 64 and bus 63, FIG. 11 shows the 1050 capacitor coupled between bus 64 and bus 63, and FIG. 12 shows capacitor 1205 coupled between bus 64 and bus 63. Capacitors 905, 1050, and 1205 can be a single shared capacitor.

With reference to the figure. 2, while the AC / DC converter 200 is configured as a four-quadrant inverter, by providing positive and negative DC voltages, an AC / DC converter can be arranged in other configurations. For example, an AC / DC converter can be configured as a 2-quadrant rectifier, providing only positive DC voltages during the positive half cycles of the input line voltage (and only negative DC voltages during the negative half cycles of the input line voltage). input line) by replacing switches 210 and 260 with diodes.

While the present disclosure uses co-packaged devices (eg a switch and a diode coupled in parallel) other circuits may be used, eg a circuit configured to allow a current to flow in a substantially uninhibited first direction. , while selectively controlling the flow of current in a direction opposite to the first direction, it can be used.