WO2021128584A1

WO2021128584A1 - Wind power generation grid-connected inverter and control method therefor

Info

Publication number: WO2021128584A1
Application number: PCT/CN2020/077561
Authority: WO
Inventors: 张为民; 周一晨
Original assignee: 合肥为民电源有限公司
Priority date: 2019-12-24
Filing date: 2020-03-03
Publication date: 2021-07-01
Also published as: CN111030177B; CN111030177A

Abstract

A wind power generation grid-connected inverter and a control method therefor, relating to the technical field of wind power generation. The control method for a wind power generation grid-connected inverter comprises: upon detection of a braking instruction, controlling an inverter circuit to stop inversion; controlling a grid-connected switch to be open; controlling an unloading circuit to perform unloading; and finally, controlling an electronic brake switch to be closed. The wind power generation grid-connected inverter of the present application has a simple structure and is reliable in operation. By means of the control method of the present application, a direct-current bus voltage can be effectively controlled in a normal operation process of a wind turbine, and braking of the wind turbine can be quickly, effectively and safely achieved when the wind turbine satisfies braking conditions.

Description

Wind power generation grid-connected inverter and control method thereof

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office with the application number 201911345576.0 and the invention titled "Wind Power Grid-connected Inverter and Its Control Method" on December 24, 2019, the entire content of which is incorporated by reference In this application.

Technical field

This application relates to the technical field of wind power generation, and in particular to a grid-connected inverter for wind power generation and a control method thereof.

Background technique

At present, the grid-connected inverter for wind power generation usually includes a rectifier circuit, an unloading circuit, a booster circuit, and an inverter circuit. The wind power grid-connected inverter, wind generator and power grid constitute a wind power grid-connected system. The three-phase AC output terminal of the wind turbine is connected to the input terminal of the rectifier circuit, the output terminal of the rectifier circuit is connected to the input terminal of the boost circuit through the unloading circuit, and the output terminal of the boost circuit is connected to the DC side of the inverter circuit. The AC side of the inverter circuit is connected to the grid.

In order to ensure that the DC bus voltage is lower than the preset threshold to prevent the inverter from being burnt due to excessive voltage, the prior art usually uses unloading circuits for unloading to suppress the rise of the DC bus voltage and ensure that the DC bus voltage is lower than the preset Threshold. However, in the case of a rapid increase in wind speed, the DC bus voltage will also increase rapidly, and the use of unloading circuits for unloading is not sufficient to suppress the rise of the DC bus voltage, resulting in excessive DC bus voltage. During the operation of the grid-connected system, when the wind turbine needs to be braked, if the load is directly unloaded for braking, the grid energy will be reversed to the inverter, consuming grid energy; the existing braking method cannot guarantee the safety and effectiveness of the wind turbine Ground braking can easily burn the wind turbine.

Summary of the invention

The purpose of this application is to provide a wind power grid-connected inverter with simple structure and reliable operation and a control method thereof, which can prevent grid energy from being poured back into the inverter when the wind power generator is braking, which can be realized quickly, effectively and safely. The wind turbine brakes.

The specific technical solutions are as follows:

In a first aspect, a method for controlling a wind power grid-connected inverter is provided. The method is applied to a control component in a wind power grid-connected inverter. The wind power grid-connected inverter further includes: an electronic system Active switch, three-phase bridge-type semi-controlled rectifier circuit, unloading circuit, inverter circuit and grid-connected switch, the electronic brake switch is connected to the output end of the wind generator and the three-phase bridge-type semi-controlled rectifier circuit Between the input ends, the output end of the three-phase bridge half-controlled rectifier circuit is connected to the input end of the unloading circuit, the output end of the unloading circuit is connected to a DC bus, and the DC bus is connected to the inverter circuit. The AC side of the inverter circuit is connected to the grid through the grid-connected switch, and the control component is connected to the electronic brake switch, the three-phase bridge semi-controlled rectifier circuit, and the unloading circuit respectively. The load circuit, the inverter circuit, and the grid-connected switch are connected, and the method for controlling the wind power grid-connected inverter includes the following steps: step S1, when a brake command is detected, control the inverter circuit to stop the reverse Change; step S2, control the grid-connected switch to open; step S3, control the unloading circuit to unload; step S4, control the electronic brake switch to close.

Optionally, before the step S2, the method further includes: determining whether the time period after the inverter circuit stops inverting reaches a first preset time period; if the first preset time period is reached, execute all Mentioned step S2.

Optionally, the step S3 includes: controlling the duty cycle of the power switching device in the unloading circuit to increase from zero to 100% according to a preset first step length.

Optionally, after the step S3, the method further includes: controlling the power switching device in the three-phase bridge half-controlled rectifier circuit to be turned on, and performing current limiting control on the output current of the wind generator .

Optionally, the controlling the power switching device in the three-phase bridge-type half-controlled rectifier circuit to turn on includes: controlling the duty cycle of the power switch device in the three-phase bridge-type half-controlled rectifier circuit, starting from zero Increase to 100% according to the preset second step.

Optionally, the performing current limiting control on the output current of the wind power generator includes: when it is determined that the output current of the wind power generator exceeds a preset limit current value, reducing the output current according to a preset third step. The duty cycle of the power switching device in the three-phase bridge half-controlled rectifier circuit is reduced to limit the output current of the wind generator from continuing to increase.

Optionally, the method further includes: in the process of performing current limiting control on the output current of the wind power generator, when the output current of the wind power generator continuously exceeds a preset limit current value for a period of time, reaching the first 2. When the preset time is long, the electronic brake switch is controlled to be closed.

Optionally, the method further includes: when the speed of the wind generator is greater than a preset cut-in speed of the wind generator and less than a preset maximum speed threshold, controlling the three-phase bridge semi-controlled rectifier circuit according to the speed -The power curve table tracks the maximum power of the output of the wind generator.

Optionally, the method further includes: in the process of controlling the three-phase bridge-type semi-controlled rectifier circuit to perform maximum power tracking on the output of the wind turbine, when it is detected that the DC bus voltage of the DC bus is high When a preset grid-connected switch is turned on, the grid-connected switch is controlled to be turned on, and when it is detected that the DC bus voltage is higher than the preset grid-connected voltage, the inverter circuit is controlled to perform inverter output .

Optionally, the controlling the inverter circuit to perform inverter output includes: performing Clarke transformation on the output current of the inverter circuit to obtain that the output current of the inverter circuit is in the αβ two-phase static coordinate system The α-axis current component i _gα and the β-axis current component i _gβ ; the α-axis current component i _gα and the β-axis current component i _gβ are Park transformed to obtain the α-axis current component i _gα and the β-axis current component i gβ _{The reactive current i gd} and the active current i _{gq of the} β-axis current component i _gβ in the dq two-phase rotating coordinate system; the difference between the DC bus voltage and the preset reference voltage is subjected to proportional integral operation to obtain the active current command Value i ^* _gq ; perform proportional integral operation on the difference between the reactive current i _gd and the preset reactive current command value i ^* _gd ^{to obtain the first voltage command value u *} _sd ; compare the active current i _gq Perform proportional integral operation with the difference between the active current command value i ^* _gq to obtain a second voltage command value u ^* _sq ; compare the first voltage command value u ^* _sd and the second voltage command value u ^* _sq Carry out Park inverse transformation to obtain the first control quantity u ^* _sα and the second control quantity u ^* _sβ ; according to the first control quantity u ^* _sα and the second control quantity u ^* _sβ , Space Vector Pulse Width Modulation (SVPWM , Space vector pulse width modulation), to generate a drive signal for controlling the on-off of the power switch device in the inverter circuit.

Optionally, the method further includes: when it is detected that the time period during which the DC bus voltage is continuously less than the grid-connected voltage reaches a third preset time period, and the grid-connected power of the wind power grid-connected inverter is less than The preset minimum grid-connected power, or when an abnormality of the grid is detected, the inverter circuit is controlled to stop the inverter output, wherein the grid-connected power is the output power of the wind generator and the unloading circuit The difference in power consumed.

Optionally, the wind power grid-connected inverter further includes a manual brake switch, and the manual brake switch is arranged between the output end of the wind generator and the electronic brake switch for Manual braking when the electronic brake switch fails or is overhauled.

Optionally, the method further includes: when it is detected that the DC bus voltage of the DC bus is higher than a preset unloading voltage, controlling the unloading circuit to unload, so as to suppress the increase of the DC bus voltage ; Specifically include the following steps: Determine the initial duty cycle according to the following formula:

Among them, D ₁ is the initial duty cycle, U ₃ is the preset unloading voltage, U ₄ is the preset full unloading voltage, U _dc is the DC bus voltage, and the preset full unloading voltage U _{4 is} greater than the preset The unloading voltage U ₃ ; adjust the duty cycle of the power switching device in the unloading circuit to the initial duty cycle; control the duty cycle of the power switching device in the unloading circuit, from the The initial duty cycle starts to increase to 100% according to the preset fourth step.

Optionally, the method further includes: when the duty cycle of the power switching device in the unloading circuit reaches 100%, if the DC bus voltage rises to a preset maximum voltage threshold, controlling the three The duty cycle of the power switching device in the phase bridge half-controlled rectifier circuit is increased from zero according to the preset fifth step, and the output current of the wind generator is controlled by current limit; if the DC bus When the voltage rises to reach the preset braking condition, the braking action is executed; if the DC bus voltage drops to less than or equal to the preset maximum voltage threshold, the power switch device in the three-phase bridge semi-controlled rectifier circuit is disconnected .

On the other hand, the present application also provides a wind power grid-connected inverter. The wind power grid-connected inverter includes a control component for executing any one of the above-mentioned methods. The wind power grid-connected inverter also It includes an electronic brake switch, a three-phase bridge-type semi-controlled rectifier circuit, an unloading circuit, an inverter circuit, and a grid-connected switch. The electronic brake switch is connected to the output end of the wind generator and the three-phase bridge-type semi-controlled Between the input ends of the rectifier circuit, the output end of the three-phase bridge half-controlled rectifier circuit is connected to the input end of the unloading circuit, and the output end of the unloading circuit is connected to a DC bus, and the DC bus is connected to the The DC side of the inverter circuit is connected, the AC side of the inverter circuit is connected to the grid through the grid-connected switch, and the control component is respectively connected to the electronic brake switch, the three-phase bridge half-controlled rectifier circuit, The unloading circuit, the inverter circuit and the grid-connected switch are connected.

Optionally, the three-phase bridge semi-controlled rectifier circuit and the unloading circuit are integrated and packaged in the same Insulated Gate Bipolar Transistor (IGBT, insulated gate bipolar transistor) module, and the inverter circuit adopts Intelligent Power Module ( IPM, Intelligent Power Module).

In this application, when the brake command is detected, the drive signal of the inverter circuit power switch device is first blocked, the inverter output is stopped, and then the grid-connected switch is turned off, which can prevent the grid energy from flowing back to the unloading circuit and consume the grid energy. Control the unloading circuit to unload until it is completely unloaded (the unloading resistance is fully connected), and then control the power switching device of the lower arm of the three-phase half-controlled rectifier bridge to conduct, and at the same time, the output current of the wind turbine Perform current limiting control to prevent excessive current from burning the wind turbine; finally, the electronic brake switch is controlled to close, so that the wind turbine brakes. The wind power grid-connected inverter provided by this application has a simple structure and reliable operation; during the braking process of the wind power grid-connected inverter, the unloading circuit cooperates with the three-phase bridge-type semi-controlled rectifier bridge to realize the gradual unloading and paralleling. Finally achieve the purpose of safe braking.

Of course, implementing any product or method of the present application does not necessarily need to achieve all the advantages described above at the same time.

Description of the drawings

In order to explain the embodiments of the present application and the technical solutions of the prior art more clearly, the following briefly introduces the drawings that need to be used in the embodiments and the prior art. Obviously, the drawings in the following description are merely the present invention. For some of the applied embodiments, those of ordinary skill in the art can obtain other drawings based on these drawings without creative work.

FIG. 1 is a block diagram of the topology structure of a wind power grid-connected inverter system provided by an embodiment of the application;

2 is a schematic diagram of the topology structure of a wind power grid-connected inverter system provided by an embodiment of the application;

3 is a flowchart of a method for controlling a grid-connected inverter for wind power generation according to an embodiment of the application;

4 is a flowchart of a method for unloading control of a wind power grid-connected inverter provided by an embodiment of the application;

Fig. 5 is a flow chart of inverter control of a wind power grid-connected inverter provided by an embodiment of the application.

Detailed ways

In order to make the purpose, technical solutions, and advantages of the present application clearer, the following further describes the present application in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

The embodiment of the present application provides a method for controlling a wind power grid-connected inverter, which can be applied to control components in a wind power grid-connected inverter. Referring to FIG. 1, the wind power grid-connected inverter may further include: Electronic brake switch, three-phase bridge half-controlled rectifier circuit, unloading circuit, inverter circuit and grid-connected switch, the input end of the three-phase bridge half-controlled rectifier circuit is connected to the three-phase AC output end of the wind turbine, three-phase The output end of the bridge half-controlled rectifier circuit is connected to the input end of the unloading circuit, the output end of the unloading circuit is connected to the DC bus, the DC bus is connected to the DC side of the inverter circuit, and the AC side of the inverter circuit is connected to the grid through the grid switch Connected, there is an electronic brake switch between the output end of the wind turbine and the three-phase bridge-type semi-controlled rectifier circuit, and the control components are respectively connected with the three-phase bridge-type semi-controlled rectifier circuit, unloading circuit, inverter circuit, and electronic brake. The switch is connected to the grid-connected switch. Wind turbines can convert wind energy into electrical energy and output three-phase AC power; three-phase bridge-type semi-controlled rectifier circuits can rectify three-phase AC power output by wind turbines and output DC power; inverter circuits can control three-phase bridge-type semi-control The direct current output by the rectifier circuit is inverted, and alternating current is output to the grid. Wind power generators, wind power grid-connected inverters and the grid constitute a wind power grid-connected system.

Referring to Figure 2, the three-phase bridge half-controlled rectifier circuit may include three diodes D1, D2, D3 and three controllable switching devices V2, V3, V4. Each of the three bridge arms may include a diode and A controllable switching device. For the convenience of design, this embodiment provides the lower bridge arms are all controllable switching devices.

The grid-connected inverter for wind power generation may also include a machine-side filter and a grid-side filter. The machine-side filter is arranged at the input end of the three-phase bridge-type semi-controlled rectifier circuit, and is used for filtering the AC power output by the wind generator. The output terminal of the three-phase bridge half-controlled rectifier circuit is connected to the unloading circuit. The unloading circuit is composed of unloading resistor R1 and a controllable power switch tube V1. The output terminal of the unloading circuit is connected in parallel with the bus capacitor C1 and then connected to the inverter The input end of the circuit and the output end of the inverter circuit are connected to one end of the grid-side filter. The grid-side inverter is used to filter the three-phase AC output from the inverter circuit. The other end of the grid-side filter is connected to the grid-connected switch. One end of the grid-connected switch is connected, and the other end of the grid-connected switch is connected to the grid.

The wind power grid-connected inverter may also include a dual power supply auxiliary switching power supply, the first input end of the dual power supply auxiliary switching power supply is connected to the input end of the inverter circuit, and the second input end of the dual power supply auxiliary switching power supply is connected to the grid Connect, the output end of the dual auxiliary switching power supply is connected with the control component.

Among them, the dual power supply auxiliary switching power supply can be powered by the power grid to the dual power supply auxiliary switching power supply, and the dual power supply auxiliary switching power supply can convert the electrical energy provided by the power grid into the electrical energy required by the control component to supply power to the control component. Or, the dual power supply auxiliary switching power supply can be powered by the DC bus voltage connected to the input end of the inverter circuit to the dual power supply auxiliary switching power supply, and the dual power supply auxiliary switching power supply can convert the DC bus voltage into the electrical energy required by the control component , To supply power to the control unit.

The specific working process of the dual power supply auxiliary switching power supply is as follows:

In the absence of power from the power grid, when it is detected that the DC bus voltage is lower than the operating voltage of the dual power supply auxiliary switching power supply, the dual power supply auxiliary switching power supply may not convert the DC bus voltage into the electrical energy required by the control components, that is The dual power supply auxiliary switching power supply does not supply power to the control unit. When it is detected that the DC bus voltage reaches the operating voltage of the dual power supply auxiliary switching power supply, the dual power supply auxiliary switching power supply can convert the DC bus voltage into the electrical energy required by the control component, that is, the dual power supply auxiliary switching power supply supplies power to the control component .

When the power grid has electricity, the dual power supply auxiliary switching power supply can be supplied from the power grid to the dual power supply auxiliary switching power supply. The dual power supply auxiliary switching power supply can convert the electrical energy provided by the power grid into the electrical energy required by the control components to provide control The power supply of the components improves the reliability of the communication and monitoring of the system and the realization of energy dispatching.

The following will describe in detail a method for controlling a wind power grid-connected inverter provided in an embodiment of the present application in conjunction with specific implementations. As shown in FIG. 3, the specific steps may include:

S1. When the brake command is detected, control the inverter circuit to stop the inverter.

In one implementation manner, it is possible to control the inverter circuit to stop the inverter by stopping the output of the drive signal to the power switch device of the inverter circuit.

Among them, the brake command can be a brake command that is triggered when the output current of the wind turbine exceeds a preset braking current value, or a brake command that is triggered when the speed of the wind turbine exceeds the preset brake speed, or the output voltage of the wind turbine The brake command is triggered when the preset overpressure point is exceeded, or the brake command is triggered when the manual brake button is manually pressed.

S2, control the grid-connected switch to turn off.

Controlling the disconnection of the grid-connected switch can prevent the grid energy from flowing back to the unloading circuit and consume the grid energy.

In one embodiment, before controlling the grid-connected switch to turn off, the control component may also determine whether the time period after the inverter circuit stops inverting reaches the first preset time period; if the first preset time period is reached, execute the control grid-connected Steps to switch off.

Waiting for the first preset period of time so that the output current of the grid-side filter is close to zero before the grid-connected switch is turned off. Controlling the grid-connected switch to turn off will have no effect on the system, and the output voltage of the grid-side filter will not be affected. When fluctuations occur, a smooth switch from grid-connected to off-grid can be realized.

S3. Control the unloading circuit to unload.

In an embodiment, the specific process of controlling the unloading circuit to perform unloading may include: controlling the duty cycle of the power switching device in the unloading circuit, starting from zero and increasing according to a preset first step, until the duty cycle The ratio increases to 100%.

Among them, the duty cycle of the power switching device in the unloading circuit is 100%, which means that the unloading resistor is completely connected to the circuit.

S4. Control the electronic brake switch to close to lock the wind generator.

Further, in order to reduce the impact of the current on the wind generator during the braking process, in one embodiment, after step S3, the method may further include: controlling the power switch in the three-phase bridge semi-controlled rectifier circuit The device is turned on and performs current limiting control on the output current of the wind turbine.

In an embodiment, the specific process of controlling the power switching device in the three-phase bridge half-controlled rectifier circuit to turn on may include: controlling the duty cycle of the power switching device in the three-phase bridge half-controlled rectifier circuit, starting from zero according to The preset second step size is increased to 100%.

When the power switching device in the three-phase bridge half-controlled rectifier circuit is gradually turned on, the output current of the wind generator will gradually increase. When the power switching device is completely turned on, that is, the three-phase output terminal of the wind generator is short-circuited. During the gradual conduction of the power switching device in the three-phase bridge half-controlled rectifier circuit, the output current of the wind generator can be monitored to prevent the wind generator from being damaged by the overcurrent.

In one embodiment, performing current limiting control on the output current of the wind generator may include: determining whether the output current of the wind generator exceeds a preset limit current value, and if so, reducing the output current according to the preset third step. The duty cycle of the power switching device in the small three-phase bridge half-controlled rectifier circuit is to limit the output current of the wind turbine to continue to increase.

In one embodiment, in the process of performing current limiting control on the output current of the wind generator, when it is detected that the output current of the wind generator continues to exceed the preset limit current value for a period of time and reaches the second preset period of time, Then you can control the electronic brake switch to close.

Wherein, the braking process of the wind turbine described above can be triggered under braking conditions. For example, the braking condition can be that the output current of the wind turbine exceeds a preset braking current value, or the speed of the wind turbine exceeds a preset braking The speed, or the output voltage of the wind generator exceeds the preset overvoltage point, or the manual brake button is pressed manually.

The control method of the wind power grid-connected inverter of the present application may also include separate unloading control.

In one embodiment, when the wind power grid-connected inverter is running, the control component can detect the DC bus voltage in real time (ie, the voltage U _dc across the capacitor C1 in FIG. 2 ).

When the wind speed is high, when it is detected that the DC bus voltage is higher than the preset unloading voltage (that is, the unloading condition is established), the control component can control the unloading circuit to unload to suppress the rise of the DC bus voltage and prevent the DC bus The voltage is too high.

In the embodiment of the present application, the control component can perform unloading by adjusting the duty cycle of the power switching device in the unloading circuit. Referring to FIG. 4, the specific process may include:

S01: Determine the initial duty cycle according to a preset duty cycle calculation formula.

Among them, the duty cycle calculation formula is as follows:

D ₁ is the initial duty cycle, U ₃ is the preset unloading voltage, U ₄ is the preset complete unloading voltage, and U _dc is the DC bus voltage.

S02. Adjust the duty cycle of the power switching device in the unloading circuit to the initial duty cycle.

S03. Control the duty cycle of the power switching device in the unloading circuit, and increase the duty cycle from the initial duty cycle to 100% according to a preset fourth step.

S04. When the duty cycle of the power switching device in the unloading circuit reaches 100%, if the DC bus voltage rises to the preset maximum voltage threshold, the power switching device in the three-phase bridge half-controlled rectifier circuit is controlled to occupy The air ratio is increased from zero according to the preset fifth step, and the output current of the wind turbine is controlled by current limit.

In the case that the unloading resistor is fully connected to the circuit, if the wind speed continues to increase, the DC bus voltage will also increase rapidly. Using the unloading circuit to unload is not enough to suppress the rise of the DC bus voltage and may cause the DC bus voltage to continue to rise. When it reaches the preset maximum voltage threshold, at this time, the control component can control the inverter circuit to stop the inverter output, and control the duty cycle of the power switching device in the three-phase bridge half-controlled rectifier circuit to start from zero according to the preset The fifth step length is increased to suppress the rise of the DC bus voltage.

S05. If the DC bus voltage rises to reach the preset braking condition, the braking action is executed; if the DC bus voltage drops to less than or equal to the preset maximum voltage threshold, the power switch in the three-phase bridge semi-controlled rectifier circuit is disconnected Device.

In one embodiment, the DC bus voltage can be detected in real time. If the DC bus voltage is on the rise and reaches the preset braking condition, the braking action can be performed. If the DC bus voltage drops to the preset maximum voltage threshold Or below, the power switching device in the three-phase bridge half-controlled rectifier circuit can be disconnected.

In addition, during the braking process, the control component can compare the current unloading duty ratio during braking with the unloading duty ratio during the separate unloading process before braking, and select the larger duty ratio for unloading control. This is more conducive to fast braking.

In an embodiment, in the process of controlling the unloading circuit to unload, the control component may also determine whether the unloading circuit is abnormal. When it is determined that the unloading circuit is abnormal, the control component can output an alarm message.

In one embodiment, the grid-connected inverter for wind power generation of the present application may further include a manual brake switch. The manual brake switch may be arranged between the output end of the wind generator and the electronic brake switch for use in the electronic brake switch. Manual brake when the switch fails or is overhauled.

The embodiment of the application suppresses the rise of the DC bus voltage by controlling the unloading of the unloading circuit and combining the control of the power switch device in the three-phase bridge half-controlled rectifier circuit to turn on, which can effectively suppress the rise of the DC bus voltage and prevent the DC bus. The voltage is too high.

In the braking process, fast, effective and safe braking can be achieved by controlling the unloading of the unloading circuit and controlling the conduction of the switching devices in the three-phase bridge semi-controlled rectifier circuit.

In one embodiment, the control component may also perform maximum power tracking control on the output of the wind turbine. The specific process may include the following steps: When the speed of the wind turbine is greater than the preset cut-in speed of the wind turbine and less than the preset maximum At the speed threshold, the three-phase bridge-type semi-controlled rectifier circuit is controlled to track the maximum power of the output of the wind turbine according to the speed-power curve table.

In an implementation manner, the control component may include a detection device through which the rotation speed of the wind generator can be sampled.

Furthermore, when it is judged that the rotation speed of the wind turbine is greater than the preset cut-in rotation speed of the wind turbine and less than the preset maximum rotation speed threshold, the current rotation speed value of the wind turbine can be combined to find the rotation speed-power curve table of the wind turbine, Obtain the output phase current reference value or output power reference value of the wind turbine.

Then, according to the output phase current reference value or output power reference value of the wind generator, the deviation adjustment control of the output of the wind generator can be performed.

The deviation adjustment control can include: the difference between the output phase current of the wind turbine and the reference value of the output phase current of the wind turbine to obtain the current error value, and the deviation adjustment of the current error value, such as proportional integral control (Proportional Integral Control, PIC) Or Proportional Integral Differential Control (PIDC) to obtain the PWM control signal for controlling the three-phase bridge half-controlled rectifier circuit of the wind turbine; or, it can also include: Combining the output power of the wind turbine with the power of the wind turbine The reference value is differenced to obtain the power error value, and the power error value is subjected to deviation adjustment to obtain the control signal for controlling the three-phase bridge semi-controlled rectifier circuit.

In addition, there are many ways to express the power curve of wind turbines, such as the relationship between wind turbine speed and output power, the relationship between wind turbine output voltage and output power, the relationship between wind turbine output current and output voltage, or The relationship between the speed of the wind turbine and the output current, etc., can switch between various power curves.

In one embodiment, the control component may also perform grid-connected control. The specific process may include: in the process of controlling the three-phase bridge-type semi-controlled rectifier circuit to track the output of the wind turbine with maximum power, when the DC bus voltage is detected When it is higher than the preset grid-connected switch conduction voltage, the grid-connected switch is controlled to conduct; when it is detected that the DC bus voltage is higher than the preset grid-connected voltage, the inverter circuit is controlled to perform inverter output.

In an embodiment, referring to FIG. 5, the specific process of controlling the inverter circuit to perform inverter output may include:

Perform Clarke transformation on the output current of the inverter circuit to obtain the α-axis current component i _gα and β-axis current component i _gβ of the output current of the inverter circuit in the αβ two-phase static coordinate system; among them, the output of the inverter circuit The Clarke transformation of the current requires obtaining the phase of the grid voltage. As an example, the phase θ of the grid voltage can be detected by a PLL (Phase Locked Loop).

_Carry out Park transformation on the α-axis current component i _gα and β-axis current component i _{gβ to obtain the reactive current i gd} and active current of the α-axis current component i _gα and the β-axis current component i _gβ in the dq two-phase rotating coordinate system i _gq .

Perform proportional integral PI calculation on the difference between the DC bus voltage and the preset reference voltage to obtain the active current command value i ^* _gq .

Perform a PI operation on the difference between the reactive current i _gd and the preset reactive current command value i ^* _gd ^{to obtain the first voltage command value u *} _sd .

The PI operation is performed on the difference between the active current i _gq and the active current command value i ^* _gq ^{to obtain the second voltage command value u *} _sq .

Perform Park inverse transformation on the first voltage command value u ^* _sd and the second voltage command value u ^* _sq to obtain the first control quantity u ^* _sα and the second control quantity u ^* _sβ .

According to the first control quantity u ^* _sα and the second control quantity u ^* _sβ , space vector pulse width modulation is performed to generate a drive signal for controlling the on and off of the power switch device in the inverter circuit.

Among them, by adjusting the preset reactive current command value i ^* _gd , the power factor of the wind power grid-connected inverter can be adjusted. For example, when the preset reactive current command value i ^* _gd is 0, wind power can be achieved. Unit power factor operation of grid-connected inverter for power generation.

In one embodiment, the control component may control the inverter circuit to stop the inverter output when it detects the grid-connected cut-out instruction. The specific process may include: when it is detected that the DC bus voltage continues to be less than the grid-connected voltage for a period of time, reaching the third When the preset time period and the grid-connected power of the wind power grid-connected inverter are less than the preset minimum grid-connected power, or the grid is detected to be abnormal, the inverter circuit is controlled to stop the inverter output.

Based on the same technical concept, the embodiment of the present application also provides a wind power grid-connected inverter. The wind power grid-connected inverter includes a control component for executing any one of the above methods. The wind power grid-connected inverter also It can include an electronic brake switch, a three-phase bridge half-controlled rectifier circuit, an unloading circuit, an inverter circuit, and a grid-connected switch. The input end of the three-phase bridge half-controlled rectifier circuit is connected to the three-phase output end of the wind turbine. The output end of the phase bridge half-controlled rectifier circuit is connected to the input end of the unloading circuit, the output end of the unloading circuit is connected to the DC bus, the DC bus is connected to the DC side of the inverter circuit, and the AC side of the inverter circuit is connected to the grid switch through the grid switch. Grid connection, an electronic brake switch is installed between the three-phase bridge-type semi-controlled rectifier circuit and the output of the wind turbine, and the control components are connected with the electronic brake switch, three-phase bridge-type semi-controlled rectifier circuit, unloading circuit, and inverter respectively. The circuit is connected to the grid switch.

In one embodiment, the three-phase bridge half-controlled rectifier circuit and the unloading circuit can be integrated and packaged in the same IGBT module, and the inverter circuit can be an IPM module.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply one of these entities or operations. There is any such actual relationship or order between. Moreover, the terms "include", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes those that are not explicitly listed Other elements of, or also include elements inherent to this process, method, article or equipment. If there are no more restrictions, the element defined by the sentence "including a..." does not exclude the existence of other same elements in the process, method, article, or equipment that includes the element.

The various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the grid-connected inverter for wind power generation, since it is basically similar to the method embodiment, the description is relatively simple, and for related parts, please refer to the part of the description of the method embodiment.

The above are only the preferred embodiments of this application and are not intended to limit this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included in this application Within the scope of protection.

Claims

A control method of a wind power grid-connected inverter, characterized in that the method is applied to a control component in a wind power grid-connected inverter, and the wind power grid-connected inverter further includes: an electronic brake switch , Three-phase bridge-type semi-controlled rectifier circuit, unloading circuit, inverter circuit and grid-connected switch, the electronic brake switch is connected to the output end of the wind generator and the input end of the three-phase bridge-type semi-controlled rectifier circuit In between, the output terminal of the three-phase bridge half-controlled rectifier circuit is connected to the input terminal of the unloading circuit, and the output terminal of the unloading circuit is connected to a DC bus, and the DC bus is connected to the DC of the inverter circuit. Side connection, the AC side of the inverter circuit is connected to the grid through the grid-connected switch, and the control component is respectively connected to the electronic brake switch, the three-phase bridge half-controlled rectifier circuit, and the unloading circuit , The inverter circuit is connected to the grid-connected switch, and the control method of the wind-power grid-connected inverter includes the following steps:

Step S1, when the brake command is detected, control the inverter circuit to stop the inverter;

Step S2: Control the grid-connected switch to be turned off;

Step S3, controlling the unloading circuit to unload;

Step S4: Control the electronic brake switch to close.
The method according to claim 1, characterized in that, before the step S2, the method further comprises:

Judging whether the time period after the inverter circuit stops inverting reaches a first preset time period;

If the first preset duration is reached, the step S2 is executed.
The method according to claim 1, wherein the step S3 includes:

The duty cycle of the power switching device in the unloading circuit is controlled, starting from zero and increasing to 100% according to a preset first step.
The method according to claim 1, characterized in that, after the step S3, the method further comprises:

The power switch device in the three-phase bridge half-controlled rectifier circuit is controlled to be turned on, and the output current of the wind power generator is controlled by current limit.
The method according to claim 4, wherein the controlling the power switching device in the three-phase bridge half-controlled rectifier circuit to be turned on comprises:

The duty cycle of the power switching device in the three-phase bridge half-controlled rectifier circuit is controlled to increase from zero to 100% according to a preset second step.
The method according to claim 4 or 5, wherein the performing current limiting control on the output current of the wind power generator comprises:

When it is judged that the output current of the wind generator exceeds the preset limit current value, the duty cycle of the power switching device in the three-phase bridge half-controlled rectifier circuit is reduced according to the preset third step length, so as to The output current of the wind turbine is limited to continue to increase.
The method according to claim 4, wherein the method further comprises:

In the process of performing current limiting control on the output current of the wind generator, when the output current of the wind generator continues to exceed the preset limit current value for a period of time, and reaches a second preset period of time, the control is controlled. The electronic brake switch is closed.
The method according to claim 1, wherein the method further comprises:

When the speed of the wind generator is greater than the preset cut-in speed of the wind generator and less than the preset maximum speed threshold, the three-phase bridge semi-controlled rectifier circuit is controlled to control the wind generator according to the speed-power curve table. Output for maximum power tracking.
The method according to claim 8, wherein the method further comprises:

In the process of controlling the three-phase bridge half-controlled rectifier circuit to track the maximum power of the output of the wind turbine, when it is detected that the DC bus voltage of the DC bus is higher than the preset grid-connected switch conduction voltage When the grid-connected switch is controlled to be turned on, and when it is detected that the DC bus voltage is higher than the preset grid-connected voltage, the inverter circuit is controlled to perform inverter output.
The method according to claim 9, wherein the controlling the inverter circuit to perform inverter output comprises:

Perform Clarke transformation on the output current of the inverter circuit to obtain the α-axis current component i gα and the β-axis current component i gβ of the output current of the inverter circuit in the αβ two-phase stationary coordinate system;

Perform Parker Park transformation on the α-axis current component i gα and the β-axis current component i gβ to obtain the α-axis current component i gα and the β-axis current component i gβ in the dq two-phase rotating coordinate system Reactive current i gd and active current i gq ;

Perform proportional integral calculation on the difference between the DC bus voltage and the preset reference voltage to obtain the active current command value i * gq ;

Perform proportional integral operation on the difference between the reactive current i gd and the preset reactive current command value i * gd to obtain the first voltage command value u * sd ;

Perform proportional integral operation on the difference between the active current i gq and the active current command value i * gq to obtain a second voltage command value u * sq ;

Perform Park inverse transformation on the first voltage command value u * sd and the second voltage command value u * sq to obtain a first control quantity u * sα and a second control quantity u * sβ ;

Carry out space vector pulse width modulation SVPWM according to the first control quantity u * sα and the second control quantity u * sβ , and generate a drive signal for controlling the on and off of the power switching device in the inverter circuit.
The method according to claim 10, wherein the method further comprises:

When it is detected that the time period during which the DC bus voltage is continuously less than the grid-connected voltage reaches the third preset time period, and the grid-connected power of the wind power grid-connected inverter is less than the preset minimum grid-connected power, or it is detected When the power grid is abnormal, the inverter circuit is controlled to stop the inverter output, wherein the grid-connected power is the difference between the output power of the wind generator and the power consumed by the unloading circuit.
The method according to claim 1, wherein the grid-connected inverter for wind power generation further comprises a manual brake switch, and the manual brake switch is arranged at the output end of the wind power generator and the electronic brake switch. Between the moving switches, it is used for manual braking when the electronic brake switch fails or is overhauled.
The method according to claim 1, wherein the method further comprises: when it is detected that the DC bus voltage of the DC bus is higher than a preset unloading voltage, controlling the unloading circuit to perform unloading, In order to suppress the rise of the DC bus voltage; specifically including the following steps:

Determine the initial duty cycle according to the following formula:

Among them, D 1 is the initial duty cycle, U 3 is the preset unloading voltage, U 4 is the preset full unloading voltage, U dc is the DC bus voltage, and the preset full unloading voltage U 4 is greater than the preset The unloading voltage U 3 ;

Adjusting the duty cycle of the power switching device in the unloading circuit to the initial duty cycle;

The duty cycle of the power switching device in the unloading circuit is controlled, and the duty cycle is increased to 100% according to a preset fourth step from the initial duty cycle.
The method according to claim 13, wherein the method further comprises:

When the duty cycle of the power switching device in the unloading circuit reaches 100%, if the DC bus voltage rises to the preset maximum voltage threshold, the power in the three-phase bridge semi-controlled rectifier circuit is controlled The duty cycle of the switching device is increased from zero according to a preset fifth step, and the output current of the wind generator is controlled by current limit;

If the DC bus voltage rises to reach the preset braking condition, the braking action is executed; if the DC bus voltage drops to less than or equal to the preset maximum voltage threshold, the three-phase bridge semi-controlled rectifier circuit is disconnected Power switching devices in the.
A wind power grid-connected inverter, characterized in that the wind power grid-connected inverter includes a control component for executing the method in any one of claims 1-14, and the wind power grid-connected inverter It also includes an electronic brake switch, a three-phase bridge half-controlled rectifier circuit, an unloading circuit, an inverter circuit, and a grid-connected switch. The electronic brake switch is connected to the output end of the wind generator and the three-phase bridge half Between the input ends of the controlled rectification circuit, the output end of the three-phase bridge half-controlled rectification circuit is connected to the input end of the unloading circuit, and the output end of the unloading circuit is connected to the DC bus, and the DC bus is connected to the The DC side of the inverter circuit is connected, the AC side of the inverter circuit is connected to the grid through the grid-connected switch, and the control component is respectively connected to the electronic brake switch and the three-phase bridge semi-controlled rectifier circuit , The unloading circuit, the inverter circuit and the grid-connected switch are connected.
The grid-connected inverter for wind power generation according to claim 15, wherein the three-phase bridge half-controlled rectifier circuit and the unloading circuit are integrated and packaged in the same insulated gate bipolar transistor IGBT module, and The inverter circuit adopts the intelligent power module IPM.