Device and method for providing electrical energy at a branch circuit supplying a load

0001The present invention relates to a method and a device for providing electrical energy to be supplied to a consumer, in particular for providing electrical energy to be supplied to an electric vehicle and a system consisting of a charging station and an electric vehicle and a use for the charging process of an electric vehicle.

0002The safety aspect plays a central role in connection with the supply of electrical consumers, in particular electric vehicles. It is known to equip a supply device, which can in particular represent the charging station for an electric vehicle, with a large number of different components, the individual functions of which are described below: First of all, the supply facility must have an energy meter, also known as an "electricity meter", with which the amount of electrical energy drawn from the energy supply company is recorded and made available for further calculation.

0003Such meters record the phase current provided in the power grid as well as the applied voltage. From this, you determine the amount of active energy used in kilowatt hours by multiplying and integrating over time.

0004So-called "Ferraris counters", which work according to the induction principle, are the most widespread. A rotating magnetic field is induced in an aluminum disc by the single or multi-phase alternating current and the mains voltage, which generates a torque in this disc through eddy currents. This torque is proportional to the vector product of current and voltage. The aluminum disc runs in an eddy current brake consisting of a permanent magnet, which generates a braking torque proportional to the speed. The aluminum disk, the edge of which is visible from the outside as a section through a window, has a rotational speed that is proportional to the electrical power. A roller counter is connected to the aluminum disc so that the energy throughput can be read off as a numerical value in kilowatt hours (kWh).

0005In the case of tariff customers, for example in private households, such electromechanical energy meters with two or more counters are used in order to be able to bill different tariffs based on time. For example, built-in or external ripple control receivers, which are controlled by central ripple control systems in the energy supply company, switch between these registers. In this way, the energy consumption can be billed more cheaply for the consumer in times of low network load, for example at night.

0006Digital electronic energy meters (so-called “smart meters”) that do not contain any mechanically moving elements are also already known. The current is detected by current transformers, for example with a soft-magnetic ring core or a current measuring system with Rogowski coils using a shunt resistor (shunt) or Hall elements. The energy is calculated using an electronic circuit. The result is shown in an alphanumeric display, e.g a liquid crystal display (LCD). Such digital electronic energy meters have the particular advantage of being able to be read remotely and therefore make the annual reading that has been customary up to now superfluous, since the meter data is transmitted electronically, for example via the Internet, to the electricity provider.

0007Various variants are used as data interfaces for data transmission to the billing unit of the energy supply company, e.g. infrared, S0 interface, M-Bus, potential-free contact, EIB/KNX, or Power Line Communication (PLC), in which data is transmitted via the normal power line.

0008In addition, as is known, a supply facility for a consumer has monitoring facilities to ensure their proper operation and, if necessary, to initiate appropriate protective measures if the supply facility is overloaded. In terms of their functionality, these are switching devices that are used to connect or disconnect the load circuit, safety devices that are intended to protect the circuits from damage due to excessive line heating or short circuits, and residual current monitoring devices.

0009A switching means is designed in a known manner as an electromagnetically actuated switch ("contactor"), in which a control current flows through a magnetic coil, the magnetic attraction mechanically actuating a contact which closes the main circuit. The switch-on position is maintained as long as the control current flows. Contactors differ from relays in that they have higher switching capacities.

0010So-called FI switches (also known as RCDs) are particularly suitable as residual current monitoring devices<i>"Residual current protective device"</i>) are known which, when a certain differential current strength is exceeded (usually 30 mA in house systems), disconnect the monitored circuit from the rest of the network on all poles, ie with regard to all conductors except the protective conductor.

0011To do this, the RCD compares the level of the current flowing forward with that of the current flowing back. The signed sum of all currents flowing through the RCD must be zero if the system is intact. The comparison takes place in a summation current transformer, which adds all the currents flowing to and from the consumer with the correct sign. If a current is diverted to earth somewhere in the circuit, the sum of the current flowing back and forth in the summation current transformer is not equal to zero: a current difference ΔI occurs, which leads to the RCD responding and thus to the power supply being switched off.

0012Residual current protection devices of the AC type (sensitive to alternating current) only detect purely sinusoidal residual currents. In practice, therefore, so-called “Type A” residual current protective devices that are sensitive to pulsating currents are common. These record purely sinusoidal alternating currents as well as pulsating DC residual currents. This additional sensitivity is achieved through special magnetic materials for the toroidal tape cores used. Residual current devices sensitive to pulse currents work independently of the mains voltage.

0013Equipment used in power electronics, such as frequency converters, inverters, uninterruptible power supplies (UPS), switching power supplies or phase control, generate a bipolar, pulse width modulated output voltage with switching frequencies in the range of up to 20 kHz. In the event of a fault, this equipment can - in addition to 50 Hz AC and pulsed DC fault currents - also cause smooth DC fault currents and AC fault currents of various frequencies as well as mixed frequencies (in the case of frequency converters, for example, the switching frequency and output frequency). Type A residual current circuit breakers cannot precisely detect these residual currents, so that proper tripping of the residual current circuit breaker cannot be guaranteed. Therefore, according to VDE 0160/EN 50178 "Equipment of high-voltage systems with electronic equipment", Sections 5.2.11.2 and 5.3.2.3, a "Type B" RCD must be used to protect against direct and indirect contact if electronic equipment is part of an electrical system in the In the event of a fault, a smooth DC fault current can be generated.

0014Such so-called AC/DC sensitive residual current circuit breakers ("Type B") contain a second summation current transformer for detecting smooth DC residual currents. In the event of a fault, an electronic unit forwards the switch-off command to the trigger. Monitoring for DC fault currents is dependent on the mains voltage. Such a device therefore requires a supply voltage, which is taken from the external conductors and possibly the neutral conductor. The pulse current-sensitive switch part is independent of this and works independently of the mains voltage, as with type A.

0015Residual current circuit breakers of the type described require sensors for highly accurate detection of the current and for further processing of the measurement signal. In addition, it is stipulated that FI switches must be checked at certain intervals. For this purpose, they are operated either by hand or by additional devices provided for this purpose.

0016Finally, as a third component in a monitoring device of a supply facility, overcurrent protection devices in the form of miniature circuit breakers (LS switches or MCB<i>"Mini Circuit</i> Breakers"). Miniature circuit breakers are reusable, non-automatically resetting fuse elements that automatically switch off the circuit in the event of an overload. Such devices protect lines from damage due to excessive heating, which would result from the overcurrent flowing over a longer period of time.

0017An overcurrent can be caused by an overload or a short circuit. In the event of an overload trip, the switch-off occurs if the specified nominal value of the current flowing through the circuit breaker is significantly exceeded for a longer period of time. The time before tripping depends on the strength of the overcurrent - it is shorter with a high overcurrent than with a small overcurrent of the nominal current. A bimetal is used for triggering, which bends when heated by the current flowing through it and triggers the switch-off mechanism. The response time of an overcurrent protection device at different current levels is referred to as a characteristic and is shown in current-time characteristics.

0018If a short-circuit occurs in the system, it must be tripped very quickly, usually within a few milliseconds, by an electromagnet of the circuit breaker through which current flows. This requires sensors for a corresponding detection and switching means for further processing of the measurement signal. Circuit breakers can also be triggered manually, eg for maintenance work or for temporary shutdown. There is a toggle switch or a release button on the front of the switch for this purpose.

0019It is also known to combine a miniature circuit breaker with an FI module in order to ensure that when the FI module detects a residual current situation, the line can be shut down by the miniature circuit breaker.

0020The monitoring or safety devices described above are used in many different ways in practice in the form of the individual components described. Individual circuits or consumer branches, which contain a large number of different electrical consumers, are each protected by appropriately dimensioned components. Appropriate dimensioning of the components, usually having a hierarchical security concept, is carried out in different branches. In this case, there is also protection at different voltage levels of a network separately from one another.

0021Relevant devices for providing electrical energy are from the documents<patcit id="pcit0001" dnum="US2006238932A1"><text>U.S. 2006/238932 A1</text></patcit>, <patcit id="pcit0002" dnum="DE10151163A1"><text>DE 101 51 163 A1</text></patcit> and<patcit id="pcit0003" dnum="DE202008009929U1"><text>DE 20 2008 009929 U1</text></patcit> (post-released) known.

0022In contrast, the present invention is based on the task of developing a monitoring and safety concept which is suitable for such an application in which an individual electrical energy consumer is to experience protection that is specially tailored to his group of consumers and is independent of other consumers.

0023This object is solved by a device according to independent claim 1 and a method according to independent claim 11 .

0024The solution according to the invention is characterized in that compared to the known protection concept described above consisting of individual monitoring devices, a large number of sensors or functional assemblies can be saved if a concept tailored to the protection of an individual consumer group is pursued. This results in corresponding material and thus cost savings, since multiple functionalities can be dispensed with. The provision of a largely optional parameterization for the at least one triggering criterion also eliminates the disadvantage that exists with known overcurrent protection devices, that, for example, a miniature circuit breaker can only be parameterized inadequately with regard to its fuse characteristic (current-time characteristic), since the characteristic is essentially determined by the Material properties of the bimetal used is determined. It is also of particular importance that integration can be achieved in this way so that only a single switch is required, which can be freely assigned to the various functions (residual current monitoring, overcurrent monitoring, switching off as a contactor).

0025Further advantages of the solution according to the invention result in accordance with the embodiments presented in the dependent patent claims: Because the safety and monitoring device has an overcurrent monitoring means that detects the magnitude and/or the time profile of the electrical current provided, the functionality of a circuit breaker can be simulated .

0026If a maximum permissible current value in the consumer circuit can be specified by the parameterization means, this results in effective overcurrent protection in the event of a short circuit.

0027Because the current-time characteristic corresponds to a predeterminable fuse characteristic, the behavior of a miniature circuit breaker for thermal overload protection can be simulated, specifically with significantly improved variability compared to conventional passive miniature circuit breakers.

0028Because the safety and monitoring device has residual current monitoring means, the functionality of an FI switch can be simulated, with both the occurrence of an AC residual current (FI switch of type A) and the occurrence of a DC residual current (FI switch of type A Type B) can be monitored.

0029Both a Hall sensor and a current transformer are preferably considered as sensor means.

0030The switching device is a power switch in the form of a relay and/or a contactor.

0031In one embodiment of the device according to the invention, the safety and monitoring device is preceded by an energy meter fed by an energy supply device, so that the amount of energy consumed by the consumer can be recorded and documented.

0032Another special feature is that each consumer can be assigned a separate security and monitoring device, resulting in an optimization both in terms of costs and in terms of adaptability. Each consumer is assigned a separate energy meter, which means that each unit can be viewed as a self-sufficient individual system ("stand-alone").

0033Other special characteristics of the solution according to the invention can be seen in the fact that the security and monitoring device can have a telemetric function. Of particular importance is the possibility of remote maintenance and monitoring of malfunctions or error conditions. For example, remote restarting after the switching means has been triggered is made possible. A special safety function can also be seen in the fact that, in the event of a fault, a current loss can be achieved by switching off all phases. This is important if there is no external power supply for the monitoring device.

0034In a further embodiment of the solution according to the invention, it is provided that the safety and monitoring device receives the pilot signal of a charging control circuit of the charging stations as one of its input signals, or alternatively the safety and monitoring device receives the "Plug Present" signal of a charging control circuit as one of its input signals receives.

0035The object is explained in more detail below with reference to a drawing showing an exemplary embodiment. Show in the drawing:<dl id="dl0001"><dt>1</dt><dd>a block diagram for the structure of a known system consisting of a consumer and a supply device connected to it via a connection means;</dd><dt>2</dt><dd>a detail on the energy meter according to the in<figref idref="f0001">1</figref> illustrated embodiment;</dd><dt>3</dt><dd>a block diagram of a monitoring and safety device of a supply device for a consumer according to the embodiment of the invention;</dd><dt>Fig.4</dt><dd>a detailed representation of a monitoring and safety device of a supply facility<figref idref="f0002">figure 3</figref>.</dd></dl>

0036<figref idref="f0001">1</figref> shows a consumer 2, which can be an electrical consumer in the form of an electric vehicle, which can be connected via a connection means 10, for example a cable, to a supply device 12 in the form of a charging station.

0037The charging station 12 has a socket 14, monitoring and security components 18, 20, 22 and an energy meter 16 which is connected to the junction box of an energy supply network 13. During charging of the battery of the vehicle 2 via the cable 10, current flows from the power supply network 13 via the meter 16 and the socket 14 and the cable 10, the meter 16 and the charger 6 into the battery. The counter 16 counts the amount of energy flowing into the battery.

0038The monitoring and safety components are an RCD 18, a passive circuit breaker 20 and a contactor 22 for controlled switching on and off of the load circuit.

0039The contactor 22 is controlled via a charging station gateway computer 24. The circuit breaker 20 works in a known manner, ie it is a component which automatically switches off the circuit in the event of an overload. This protects the load circuit from damage caused by excessive heating that would result from the overcurrent flowing over a longer period of time, which overcurrent can be caused either by an overload or by a short circuit. In the event of an overload trip, the switch-off occurs if the specified nominal value of the current flowing through the circuit breaker is exceeded for a longer period of time. The time until tripping depends on the strength of the overcurrent and depends on the characteristic shown in a current-time characteristic.

0040If a short circuit occurs in the system, tripping occurs very quickly, usually within a few milliseconds. The circuit breaker 20 can also be triggered manually, for example for maintenance work or for temporary shutdown. For this purpose, there is a toggle switch or a release button on the front side of the switch 20. After the switch 20 has been released, the operator of the charging station can switch it on again manually.

0041As is known in the prior art, the FI switch 18 is also provided with an external mechanical key actuation in order to be able to carry out corresponding manual procedures. Such manual procedures related to the RCD 18 may be routine testing.

0042How out<figref idref="f0001">figure 2</figref> shows, the energy meter 16 contains on the input side, ie at its connection facing the power supply network 13, a first detector 31 for the phase voltage present at this measuring point and a second detector 32 for the phase current flowing into the meter 16. The detectors 31, 32 are designed as detectors for the corresponding electrical quantities, for example as toroidal current transformers, Hall sensors, etc. The amount of energy supplied over a certain period of time is calculated from the output signals of the detectors 31, 32 and this can be displayed on a display device 33 of the counter 16.

0043The meter 16 is a remotely readable meter which is connected to a billing center 42 via a communication network 40 . The communication network 40 can be part of the energy supply network 13 so that, for example, communication by means of power line communication can take place via the energy supply network 13 . The communication network 40 can also be a wired or wireless communication network. For example, an IP protocol can be used for communication.

0044On the output side, the counter 16 not only has a display device 34 for the calculated amount of energy, but also a further output unit 35 for the phase current, which is detected by the detector 32 . The further output unit 35 can output the measured value of the detector 32 directly or a further processed signal derived from this measured value. As an alternative to this, the phase voltage or a correspondingly further processed signal of the detector 31 can also be output by the further output unit 35 . Finally, the output of an output signal derived jointly from the signals of the detectors 31 and 32, in particular the active phase power, can also be displayed by the further output unit 35.

0045The further output unit 35, like the output unit 34 for the measured amount of energy, is assigned a data interface 36, with this data interface being separate or joint (as in<figref idref="f0001">2</figref> shown) can be formed with the data interface for the amount of energy.

0046The phase current or another electrical signal is available via the data interface 36 for further processing in connection with the monitoring or safety device described below.

0047The structure of a charging station for electric vehicles according to the present embodiment of the invention is in connection with<figref idref="f0002">figure 3</figref> explained as follows: The electrical supply line leading from the energy supply network 13 , which can be a three-phase line, opens into a connection box arranged inside the charging station 12 . From there, the lines are continued on the "electricity meter" 16, which is preferred as a as above in connection with<figref idref="f0001">figure 2</figref> represented digital energy meter is executed and the output value is passed on to a charging station gateway computer (LSG) 24 via a serial interface designed as an RS 232 interface or another serial or parallel interface for evaluating the detected amount of energy. Starting from the energy meter 16, the three-phase lines are routed to an integrated digital monitoring and safety device 50.

0048On the output side of the integrated digital monitoring and safety device 50 is the socket 14 of the charging station, via which the electric vehicle 2 is provided with the aid of the charging cable 10 the desired energy.

0049The communication between the socket 14 and the charging station gateway computer LSG 24 takes place via PWM technology, for example, while the communication between the charging station gateway computer 24 and the power line communication module PLC 26 takes place via the Ethernet protocol, for example.

0050The basic structure of the integrated digital monitoring and security device 50 is in connection with<figref idref="f0002">figure 4</figref> shown: The device 50 includes an evaluation device 52, at the input of which the output signals from sensors 31, 32 for electrical signals, in particular for the phase current and the phase voltage, are present. These sensors 31, 32 can, for example, be those components which also the input signals for the related<figref idref="f0001">figure 2</figref> form the energy meter described.

0051The electrical input variables are further processed within the evaluation circuit 52 with regard to their amplitude and the time profile and are compared with parameters stored within the evaluation circuit 52 or parameters that are predetermined in some other way. As a result, by specifying the parameters, triggering criteria are defined, when they are reached at the output of the evaluation circuit 52, a control signal is emitted, as a result of which the load circuit is switched, ie is either turned on if it was previously off, or turned off if it was previously on.

0052The functionalities that can be implemented with such a structure are described below: The sensors 31, 32 can be used to record and analyze the course of the currents or voltages in the charging circuit over time. Due to the constant recording, these signals and their evaluation results are also available for regular documentation. In addition, the output signals of the sensors 31, 32 can also be made available to other components of the charging circuit via suitable interfaces. The related to<figref idref="f0001">figure 2</figref> illustrated use for the energy meter 16 is just one of the possibilities.

0053When a maximum permissible amplitude value in the current profile is exceeded, the switching means 54 is activated in order to bring about a switch-off process, as a result of which overcurrent protection, for example in the event of a short circuit, is achieved. The safe switching of the switching means 54 can also be detected and monitored by the current detection or voltage detection.

0054One of the parameters specified by the evaluation circuit 52 can be a specific fuse characteristic in order to simulate a specific current-time characteristic. The required current-time behavior can be varied within wide limits by digital simulation of the characteristic. As a result, the overcurrent protection can be set to specific triggering characteristics that can be specified. In particular, it can be provided that previously stored safety characteristics are provided, from which the one corresponding to the application can be selected. For example, a characteristic curve adapted to a specific plug of the charging cable can be used. It is thus possible, for example, to identify a plug or a charging cable for a maximum charging current by means of a plug face or by means of a resistor arranged in the plug, for example a resistor between a plug-present or pilot conductor and a neutral conductor. This information can also be used to adapt the respective fuse characteristic. Compared to conventional functionalities of passive miniature circuit breakers, whose response characteristic cannot be parameterized, this results in far greater flexibility. Within the scope of this functionality, a compensation of the influence of the ambient temperature on the protection conditions is also made possible by appropriate parameterization of the response characteristic. This is intended to prevent the device from being triggered solely by the influence of an increased ambient temperature, without a fault actually being present. The tripping characteristic of the fuse can also be changed during operation, for example based on findings from the evaluation of the connected cable or based on findings about grid and/or installation bottlenecks.

0055The digital evaluation device 52 can also detect fault currents in the charging circuit by appropriate evaluation of current signals and corresponding difference formation and can cause a shutdown by actuating the switching means 54 . Both AC fault currents and DC fault currents can be diagnosed, which means that the behavior of a type A and type B RCD can be simulated. It is of particular importance that in the event of a fault current (AC or DC) being detected, switching means 54 can be switched off permanently and only actively switched on again when the charging station gateway computer is restarted. The start-up routine ("rebooting") can be adapted to this functionality. This also allows, for example implement the safety guidelines prescribed in the Federal Republic of Germany, which always require mains voltage-independent switching in the case of a residual current circuit breaker.

0056As a further important safety function, it can be provided that in the event of a power failure the switching means is forced to open. This also allows the FI switch functionality to be guaranteed.

0057According to an exemplary embodiment of the invention, an automatic test function can also be provided for the FI switch functionality. In this case, the monitoring and safety device 50 can be instructed to simulate a residual current. This can be done, for example, by switching on a controlled resistor between a phase or another conductor and the protective conductor, whereupon the relay of the residual current circuit-breaker is activated (and possibly switched on). not triggered) and this control signal is recognized by the external side and the functionality is therefore found to be OK. This simulation can be carried out separately for all three phases and/or at predetermined time intervals. The particular advantage compared to previous practice is that this test function - which is mandatory by law - is carried out automatically from the outside without an authorized person having to be present at the location of the charging station. For example, such a checking process can take place after a loading process has been completed.

0058The solution described above reduces the amount of components and wiring in the charging station considerably, since double functionalities, which are unavoidable when using separate safety-related components, are avoided.

0059This design offers significant advantages, especially for applications such as those found in charging stations for electric vehicles, in which an energy supply is located directly opposite a consumer. Due to the high flexibility combined with the reduced component costs, an optimized adaptation of the safety requirements to the special requirements of the consumer is achieved.