A wind turbine with a low-voltage equalizing regulator

Area techniques

The invention relates to wind turbines. In more detail, the invention relates to the support of the low voltage offset generators of wind turbines associated with the power distribution grid.

The current state of the art

From a historical point of view wind turbines contribute to the total energy production to power electric networks very little. Low unit power (<100 kW) and the uncertain availability of wind sources caused that the generators of wind turbines have been ignored, when the operators of the energy networks considering reliability of the network. Now, however, are available to generators of wind turbines with an output of 1.5 MW or more. In addition, many designers of energy production are introducing a wind farm containing one hundred or more generators of the wind turbines. Block energy available from wind farms with 1.5 MW generators of wind turbines is comparable with modern power generator gas turbines. The generators of wind turbines are therefore still more acceptable energy sources to the energy network.

For reliable delivery of energy to the energy grid must be the generators of wind turbines (as well as other types of generators) comply with the standards of the interconnection of energy networks, which define the requirements imposed on energy suppliers and black customers energy. In more detail, the requirement of the low voltage compensation (LVRT, of eng. low voltage ride through) typically requires that the energy production unit must remain connected and synchronized with the network, when the voltage at the terminals of the production unit falls to a prescribed level.

The requirement of the low voltage compensation was in the generator plants with steam and gas turbines solved with the help of vital electrical nodes, which are powered by the source of dc voltage, and auxiliary nodes connected to the generators. These types of generators are generally more resistant to voltage fluctuations than, the generators of wind turbines.

In the past, the generators of wind turbines in case of voltage drop allowed to turn off offline. For example, the most common safety concept of the generators of wind turbines is the lean system on a battery backup, which typically contains three independent battery modules. In this type of system it is possible to bend the leaves of the wind turbine from a working position into the parking position, when there is not available energy generator.

During failure of the power supply to the drives of the tilt switch of a drive powered from a generator on the propulsion powered by batteries, until the leaves do not reach the park position. To. the movement of the leaves in the park position occurs automatically due to voltage or frequency errors. This, however, does not meet the requirement of the low voltage offset, because the generator of the wind turbine is allowed to turn off offline.

Currently, the legislation of the generators of wind turbines can require connection and synchronization with the energy networks up to the level of 70 % of the rated voltage. These requirements can be meet such as increased capacity of the various components (motors, generators, converters, etc.) and using bezvýpadkových backup power sources (UPS) for sensitive control circuits. However, more severe voltage fluctuations, e.g. a voltage around 15 % wenovitého voltage, cannot be met using these techniques.

The essence of the invention

Here, the described techniques allow you to affix the generator of the wind turbine, one or more of the following characteristics: 1) stay in sync with the energy grid during severe voltage fluctuations, 2) to maintain

- 1 CZ 307397 B6 the functioning of the inclining system of the leaves despite the lack of voltage at the terminals of the generator, 3) to protect the converter power and the generator from high voltages and currents during the voltage fluctuation, and 4) temporarily wean nevitální subsystems that could be damaged by exposure to high voltage, or could be turned off either by the intervention of the circuit breaker or the activities of the fuses.

Clarification of the drawings

The invention will be closer explained by means of concrete examples of embodiment shown in the drawings, which represents the fig. 1 graph of voltage and time for the model event of the wobble voltage;

fig. 2 a schematic representation of one embodiment of the generator of the wind turbine;

fig. 3 block diagram of one embodiment of the electrical system of the generator of the wind turbine;

fig. 4 block diagram of one embodiment of the converter of energy having a function to respond to the low voltage event;

fig. 5 block diagram of one embodiment of regulator turbines and relevant components for use in the generator of the wind turbine;

fig. 6 flowchart of one low-voltage compensation wind design procedure in the generator turbine.

Examples of implementation of the invention

Fig. 1 is a graph of voltage and time for the model event of the wobble voltage. In the example in fig. 1, the voltage falls from 100 % of the nominal voltage manufacturing unit at 15 % of the rated voltage of the generating unit. After the wobble voltage returns to a higher level. During this wobble voltage must the generator of the wind turbine to stay connected and synchronized with the energy networks, in order to fulfill regulations of low voltage compensation.

Fig. 2 is a schematic representation of one embodiment of the generator of the wind turbine. The wind carries the leaves 200 attached to the rotor 205. Rotation of the sheet 200 can be changed by using the control apparatus (in fig. 2 are not shown). How to change wind speed, the control system of tilt changes the inclination of the leaves 200 to drive the speed of the rotor and prevent overspeed. The typical speed of the rotor to move in the range of 10 to 20 revolutions per minute, however, they may be supported by the different ranges of speed of the rotor. Tilting of the sheets is in the field of well known.

The Rotor 205 is connected to the transmission housing 210, which increases the speed of the shaft to the desired range. Typical gear ratios are in the range of 100:1, so the speed of the rotor 10 to 20 revolutions per minute will result on the high-speed shaft 215 in the 1000 to 2000 revolutions per minute. You can also use the other gear ratios and a different speed. Vysokoiychlostní shaft 215 drives generator 220 variable speeds depending on the speed of the wind.

Generator 220 produces a torque that balances the torque induced by the rotor 205. No other components should the generator produce output power with variable frequency, which would be inappropriate for connection to the energy network.

Converter 230 that contains energy antiparalelně involved inverters 235 and 240, supplies the rotor of the generator 220 performance with variable frequency. The combination of variable rotor speed and power with variable frequency for the generator rotor allows the generator to generate power with constant

-2GB 307397 B6 frequency at voltage levels suitable for the power grid (e.g., 575 V ac). In one embodiment, are inverters 235 and 240 power inverters bipolámího transistor with an isolated junction field effect transistors (1GBT). Power inverters for use in the generators of wind turbines are in the field of well-known and can use any appropriate power inverters.

Transformer 250 regulates the output of the generator of the wind turbine to the voltage of the local energy network. The overall management of wind turbines 275 performed by the regulator which controls the various systems of the wind turbine 275. These systems include e.g., the converter 230 energy, lean, lubricating and cooling systems (in figure 2 not shown) and the rotating system. Many of these systems are sensitive to voltage fluctuations and can be damaged if the voltage of the electrical system of the wind turbine is too high or too low. Specifically, the regulator of the turbine monitors wind speed and issues torque commands to the converter 230 energy and lean commands nakláněcímu system so that the performance at the output of the wind turbines 275 corresponds to the weather conditions and the speed of the rotor is holding below the limit of overspeed.

As described in more detail in connection with fig. 4, the use of převodníkového controller, which monitors the current in one or both invertorech, to the selective activation of the circuit for current limit can protect against the damage that can be caused by high currents during a low voltage event. In one embodiment selectively activates the circuit for the elimination of the surge, to divert current away from the inverters and/or other components that could be damaged by excessive currents.

Fig. 3 is a block diagram of one embodiment of the electrical system of the generator of the wind turbine. The example in figure 3 provides specific voltages that are typical for generators of wind turbines in the class of 1.5 MW for use in the United States. For 50Hz generators of wind turbines can be used other similar voltage. Higher voltage is generally used for higher fixing performance and lower voltage are used for the lower fixing performance. The overall architecture is applicable for many different types and sizes of wind turbines.

Generator 310 adds the energy of alternating current into the energy network, as well as to other components of the electrical system of the wind turbine 300. In one embodiment the generator 310 adds the 575 (which is the rated voltage of the generator), but can supply any other voltage. Generator 310 also provides energy to the converter 315 energy, which works as described above in connection with fig. 2, and the low-voltage switchboard (LVDP) 320.

In one embodiment LVDP 320 includes a transformer for transforming 575V power received from generator 310 to 120 v, 230 v and 400 V power for use in the wind turbine (120 V systems 350, 230 V systems 360, or 400 V systems 370). According to the needs of can provide the other and/or additional power levels. Systems generator wind turbine connected to LVDP 320 includes e.g. management and engines inclining system, steering and engines in the democracy system, various lubrication and cooling systems, electrical outlets and lights, heaters and various equipment.

In one embodiment LVDP 320 provides energy 24V dc current to the controller 340 of the turbine through the bezvýpadkový backup power source 330 (UPS). Bezvýpadkový backup power source 330 (UPS) provides the energy regulator 340 of the turbine in the event that the LVDP 320 is not able to deliver the controller 340 of the turbine the necessary energy. Bezvýpadkový backup power source 330 (UPS) can be any type of bezvýpadkového backup power source known in the art, e.g. battery system, fotočlánkový system or any other power storage system known in the art. In one embodiment bezvýpadkový backup power source 330 (UPS) does not have sufficient capacity to supply power to all electric loads to be operated LVDP 320.

Some of the components in the configurations in fig. 2 and 3 are susceptible to damage caused by fluctuations in voltage in the high voltage (575 V) power supply. Higher voltage can cause disorders such as puncturing of the insulation and high currents in certain components. Low voltages can cause components such as the engines, drain the excessive current, to compensate for the lower

-3 CZ 307397 B6 voltage. Higher currents may lead to burnt fuses, off přerušovačům circuits or to excessive heating, if the voltage drop persists.

Power converters and generators are particularly sensitive to voltage fluctuations. Generators can accumulate magnetic energy, which can be converted to high currents when the voltage of the generator terminals rapidly reduces. These currents can cause failure of the semiconductor devices of the converters of energy connected with the generators.

When the voltage falls to levels as illustrated in fig. 1, it is likely that will occur with the disorder that prevents the generator of the wind turbine to balance the energy in the energy network. If the wind will transmit the energy of the rotor of the turbine, generator wind turbine as a whole absorbs energy that can be accumulated only as rotational kinetic energy in the form of increased speed of the rotor. If you do not take specific measures, can the rotor to reach the limits of the overspeed and cause the shutdown of offline generator wind turbine. In one is used bezvýpadkový a backup power supply 330 to supply power to the controller 340 of the turbine and/or other components of the wind turbine during low voltage events.

As described in more detail below, for protection of the generator of the wind turbine against low voltage events, it's a converter 315 energy powered bezvýpadkovým the backup source and includes a protective circuit that maintains currents within the permissible range. The controller of the converter selectively activates and deactivates the protective circuit to keep the flow of the current in the allowable range. The controller 340 of the turbine is also fed by bezvýpadkovým the backup source and acts to prevent the shutdown from overspeed. If necessary, one or more nevitálních load during the low voltage event disconnects from the voltage to these components to protect from potential damage.

Fig. 4 is a block diagram of one embodiment of the converter of energy having a function to respond to the low voltage event. In one embodiment converter 400 energy includes inverters 410 and 420, the controller 430 of the converter and the circuit 440 for the elimination of the surge. To the converter 400 energy can also be included other components.

The inverter 410 is connected with a generator (in fig. 4 not shown) and the apc 420, which is connected with the energy grid. Circuit 440 for the elimination of the overvoltage is connected with the output of the generator rotor. The controller 430 of the converter is connected to receive data indicating the flow of current in inverter 410 and the controlling circuit 440 for the elimination of the surge. In one embodiment the controller 430 of the converter selectively activates and deactivates the protective circuit 440 for the elimination of surges to keep the current in inverter 410 in the permissible range.

Circuits to eliminate power surges are in the field of well-known and can use any suitable (i.e. the circuit with a sufficient fixing performance) circuit for eliminating surges. Circuit 440 for the elimination of power surges in general works because to take current from the generator rotor and inverter 410 and to keep the currents in the inverter to safe levels. During normal operation, it is therefore circuit 440 for the elimination of the overvoltage inactive. During the low voltage event, the controller 430 of the converter selectively activates the circuit 440 for the elimination of the surge, to keep the mainstream level in the safe range. Circuit 440 for the elimination of the overvoltage and the controller 430 of the converter are thus part of a system that allows the generator of the wind turbine to offset low voltage events and remain in sync with the energy grid.

For the control circuit 440 for the elimination of the overvoltage the controller 430 of the converter monitors rotor side currents (e.g., current in inverter 410) and selectively activates and deactivates the circuit 440 for the elimination of the surge, when they detect current levels that are dangerous for the semiconductor components of the converter 400 energy. The controller 430 of the converter and the circuit 440 for the elimination of the overvoltage, therefore, work to protect the converter 400 energy from damage incurred as a result of low-voltage events.

-4GB 307397 B6

Fig. 5 is a block diagram of one embodiment of regulator turbines and relevant components for use in the generator of the wind turbine. In one embodiment is a regulator of a turbine implemented in the form of a programmable logical controller (PLC), can, however, use other implementations. In one embodiment, the regulator of the turbine starts the turbine at its minimum wind speed (gear speed), adapts the output power of the generator to the wind speed, controls the tilt of the leaves to adapt to the speed of the wind and avoid a shutdown of overspeed, switches off the turbine at its maximum wind speed (switch speed) and rotates the generator of the wind turbine into the wind by using the democracy system. The regulator of the turbine can also provide other functions, such as to control heaters, lighting, system remote control and instrument panel (SCADA).

For support capability of the low voltage compensation controller 500 turbine detects a low voltage event and the event will react. The controller 500 turbine is coupled to system sensors 510, which provide data indicating the status of various system components of the generator of the wind turbine, e.g. rotor speed and generator output voltage. The controller 500 turbine processes these data to determine whether there has been a low-voltage event.

In one embodiment the response to the low voltage event, the controller 500 turbine switches the control system 520, the tilt of active management, in which the electronics and motors are powered by LVDP 540 to a mode in which the engines are fed from bezvýpadkového backup power source 530. In one embodiment are lean engines powered by bezvýpadkového backup power source 530, in order to ensure that the energy to tilt sheets into praporové position. Energy from bezvýpadkového backup power source 530 allows the controller 500 of the turbine and the control system 520 to tilt to regulate the tilt of the leaves during the low voltage event. Eg. the control system 520, the tilt can set up the leaves into a battalion, to slowed or stopped rotation of the rotor shaft. Bezvýpadkový backup power source 530 may also allow the control system 520, the tilt function during the event of the transition voltage, until it is restored to full power.

In one embodiment bezvýpadkový backup source 530 during the low voltage event also powers the one or more sensors. Bezvýpadkový backup power source 530 may, for example, to power the sensors speed of the rotor so that the controller 500 turbines could monitor the rotor speed during the low voltage event. The controller 500 turbine can use the data from the sensor to determine whether the exceeded speed, and accordingly react.

In one embodiment the controller 500 turbine includes control circuits for turning off power to non-critical systems in the generator of the wind turbine responsive to the low voltage event. The load may include, for example, a yaw system and other burdens, which could cause puncturing of the fuses and/or switching přerušovačů circuits. These loads typically contain motors, which, when low-voltage events are drawing high current, to maintain performance. Other non-critical loads, e.g. heaters and lights, are more resistant to damage incurred due to low-voltage events and can be left connected to LVDP 540.

Bezvýpadkový backup source 530 also supplies the regulator converter (figure 5 not shown) to the controller of the converter allow for protection against excessive currents in the invertorech, as described in connection with figure 4. In one embodiment is a controller of the converter powered from the capacitors that store the energy that is used during low voltage events.

Fig. 6 is a flowchart of one embodiment of the procedure of low voltage compensation generator of the wind turbine. The procedure in figure 6 is introduced in a specific sequence merely as an example. The order of certain parts of the procedure can be interchanged without departing from the invention.

Detects to the low voltage event, step 600. The particular voltage, which low voltage event trigger, are specific for each device. In one embodiment is the threshold voltage, which is considered to be the transition to a low-voltage event is defined as a percentage of the nominal voltage. Eg. voltage is less than 75 % of the rated voltage of the generator can be considered a low voltage event. In another example, can be a low voltage event to be considered a voltage that is 50 %

-5 CZ 307397 B6 of the rated generator voltage, or a voltage that is between 15 % and 50% of the rated generator voltage. Low voltage events can also be defined in terms of time, e.g. voltage 75 % of rated generator voltage for more than 0.5 seconds can be considered a low voltage event. To define a low voltage event can be used and other ranges and/or voltage.

When it detects a low voltage event, the selected component activates the backup power supply, step 610. In one embodiment provides power to the components of the wind turbine bezvýpadkový backup power source, e.g. a battery source, to the generator of the wind turbine stay connected and synchronized with the energy grid during the low voltage event. The power supply may be used to supply all or part of the transmitter power controller of the turbine and/or the control system of tilting the leaves.

In one embodiment, for avoidance of conditions exceeding the rotor speed ensures the power from the bezvýpadkového backup power source, to monitor the rotor speed and follow the engines inclining system of the leaves.

Deactivates the power to the unimportant elements or elements that could be damaged in the conditions of a voltage drop, high current, step 620. During the low voltage event, for example, can deactivate the engines and other components of the democracy system.

The regulator in the transmitter power monitors the current from the generator rotor to the inverter, step 630. If the current exceeds the threshold value, the controller of the converter activates the circuit for current limitation, step 640. The circuit for the current limit is in one embodiment a circuit for the elimination of the surge. The threshold value of the current is determined by the flow of current that would damage semiconductor components of the converter voltage. When it ends the low voltage event, resumes the power supply from the generator and the components of the wind turbine to operate in normal conditions, step 650.

Reference to one embodiment or on the embodiments in this description means that the specific character, structure, or characteristic described in connection with the implementation is included in at least one embodiment of the invention. Occurrences of the phrase in one embodiment at various locations of the description do not necessarily refer to the same embodiment.

In the previous description has described the invention with reference to its specific embodiment. However, it is clear that specialists can perform a variety of modifications and variations, without deviating from the broader essence and scope of the invention. Description and images have to be therefore understood rather in an illustrative than in a limiting sense.