Full-power converter high voltage ride through control method and system

Abstract

The invention provides a high-voltage ride-through control method and system for a full-power converter, and the method comprises the steps: obtaining a rated current value, a DC unloading input voltage threshold value and a DC unloading cut-out voltage threshold value of the full-power converter when a high-voltage fault occurs in a power grid; selecting a preset ride-through control strategy according to the rated current value, a direct current unloading input voltage threshold value, a direct current unloading cut-out voltage threshold value and the state of the voltage of the power grid; and performing high-voltage ride-through control on the full-power converter based on the selected ride-through control strategy. According to the technical scheme provided by the invention, the risk caused by the high-voltage fault of the power grid can be well handled, and powerful support is provided for the safe operation of the power grid.

Description

Technical Field

[0001] The present application relates to the technical field of high voltage ride through control, and in particular to a high voltage ride through control method and system for a full power converter. Background Art

[0002] For full-power converters based on synchronous generators, since the machine-side converter is isolated from the grid by the busbar, the fault response plan for the grid-side converter is the focus. When the converter uses conventional control strategies, a sudden grid surge fault will be limited by the response speed of the current controller, and current shocks will occur during the transient state of voltage rise and recovery, which may cause the busbar to shut down due to overvoltage in severe cases. During the steady state of voltage rise, if no response strategy is adopted, overmodulation will occur, resulting in out-of-control of the grid-side output current. In severe cases, a large amount of harmonic current will cause an overcurrent shutdown.

[0003] When the wind turbine is running, if the power input to the converter side is the same as the power output to the grid side, the DC bus voltage remains constant. Once a high voltage fault occurs in the grid, on the one hand, the converter on the grid side cannot normally output power to the grid. On the other hand, when the grid voltage is high enough, power backflow will occur. In both cases, the converter DC bus voltage will rise. If no measures are taken to suppress it, once the voltage reaches the DC bus capacitor withstand voltage or the upper limit of the IGBT working withstand voltage, the capacitor will be damaged or exceed the IGBT protection threshold to cause a fault, and the safe and stable operation of the grid cannot be guaranteed. Therefore, it is urgent to propose a solution that can accurately control the high voltage ride-through of the full-power converter to ensure the safe and stable operation of the grid. Summary of the invention

[0004] The present application provides a full-power converter high voltage ride-through control method and system, so as to at least solve the technical problem that the prior art cannot accurately control the full-power converter high voltage ride-through.

[0005] A first aspect of the present application provides a high voltage ride through control method for a full power converter, the method comprising:

[0006] When a high voltage fault occurs in the power grid, the rated current value, DC load shedding input voltage threshold, and DC load shedding cut-out voltage threshold of the full power converter are obtained;

[0007] Selecting a preset ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid;

[0008] High voltage ride-through control is performed on the full power converter based on the selected ride-through control strategy.

[0009] Preferably, the preset ride-through control strategies include: Chopper loop suppression strategy, grid voltage feedforward response speed acceleration strategy and inductive reactive current injection to suppress converter outlet voltage strategy.

[0010] Furthermore, the selection of the ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid includes:

[0011] If the voltage of the power grid is in a transient process of rising and recovering, a Chopper loop suppression strategy and a power grid voltage feedforward response speed acceleration strategy are used to perform high voltage ride-through control of the full power converter;

[0012] If the voltage of the power grid is in a high voltage ride-through steady state process, a high voltage ride-through control of the full power converter is performed by injecting inductive reactive current to suppress the converter outlet voltage strategy.

[0013] Furthermore, the Chopper loop suppression strategy includes:

[0014] When the DC bus voltage connected to the full power converter is greater than the DC load shedding input voltage threshold, the Chopper circuit is controlled to be input;

[0015] When the DC bus voltage connected to the full-power converter is less than the DC load shedding cut-out voltage threshold, the Chopper loop is controlled to be cut out.

[0016] Furthermore, the grid voltage feedforward response speed acceleration strategy includes:

[0017] The voltage and current of the power grid are transformed into a two-phase synchronous rotating coordinate system, and the d-axis voltage component and the q-axis voltage component of the voltage are determined by using a decoupling feedforward and PI closed-loop control method;

[0018] Transforming the d-axis voltage component and the q-axis voltage component of the voltage into a two-phase stationary coordinate system to obtain the voltage component in the two-phase stationary coordinate system;

[0019] The voltage component in the two-phase stationary coordinate system is transformed into a three-phase stationary coordinate system, and then a control voltage vector is obtained through PWM control.

[0020] Furthermore, the strategy of injecting inductive reactive current to suppress the converter outlet voltage includes:

[0021] Obtaining the voltage per unit value range of the power grid;

[0022] Determine a reactive current reference value according to the voltage per unit value range of the power grid and the rated current value of the full-power converter;

[0023] Based on the active current reference value, an inductive reactive current is injected into the full-power converter to suppress the converter outlet voltage.

[0024] A second aspect of the present application provides a high voltage ride through control system for a full power converter, including:

[0025] An acquisition module is used to acquire the rated current value, DC load shedding input voltage threshold, and DC load shedding cut-out voltage threshold of the full power converter when a high voltage fault occurs in the power grid;

[0026] A selection module, used for selecting a preset ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid;

[0027] The control module is used to perform high voltage ride-through control on the full power converter based on a selected ride-through control strategy.

[0028] Preferably, the preset ride-through control strategies include: Chopper loop suppression strategy, grid voltage feedforward response speed acceleration strategy and inductive reactive current injection to suppress converter outlet voltage strategy.

[0029] The third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in the first aspect is implemented.

[0030] A fourth aspect of the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in the first aspect of the present application.

[0031] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0032] The present application proposes a method and system for controlling high voltage ride-through of a full-power converter, the method comprising: when a high voltage fault occurs in the power grid, obtaining the rated current value, DC load shedding input voltage threshold, and DC load shedding cut-out voltage threshold of the full-power converter; selecting a preset ride-through control strategy according to the rated current value, DC load shedding input voltage threshold, DC load shedding cut-out voltage threshold, and the voltage state of the power grid; and performing high voltage ride-through control on the full-power converter based on the selected ride-through control strategy. The technical solution proposed in the present application can better cope with the risks brought by high voltage faults in the power grid and provide strong support for the safe operation of the power grid.

[0033] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0035] Figure 1 A flowchart of a high voltage ride through control method for a full power converter provided according to an embodiment of the present application;

[0036] Figure 2 A schematic diagram of a Chopper circuit provided according to an embodiment of the present application;

[0037] Figure 3 The present invention is a structural diagram of a full-power converter high voltage ride-through control system provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0038] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0039] The present application proposes a method and system for controlling high voltage ride-through of a full-power converter, the method comprising: when a high voltage fault occurs in the power grid, obtaining the rated current value, DC load shedding input voltage threshold, and DC load shedding cut-out voltage threshold of the full-power converter; selecting a preset ride-through control strategy according to the rated current value, DC load shedding input voltage threshold, DC load shedding cut-out voltage threshold, and the voltage state of the power grid; and performing high voltage ride-through control on the full-power converter based on the selected ride-through control strategy. The technical solution proposed in the present application can better cope with the risks brought by high voltage faults in the power grid and provide strong support for the safe operation of the power grid.

[0040] A high voltage ride through control method and system for a full power converter according to an embodiment of the present application will be described below with reference to the accompanying drawings.

[0041] Embodiment 1

[0042] Figure 1 Flow chart of a high voltage ride through control method for a full power converter provided according to an embodiment of the present application, such as Figure 1 As shown, the method includes:

[0043] Step 1: When a high voltage fault occurs in the power grid, the rated current value, the DC load shedding input voltage threshold, and the DC load shedding cut-out voltage threshold of the full power converter are obtained.

[0044] It should be noted that the full-power converter includes: a grid-side converter and a motor-side converter.

[0045] Step 2: Select a preset ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid.

[0046] It should be noted that the preset ride-through control strategies include: Chopper loop suppression strategy, grid voltage feedforward response speed acceleration strategy and inductive reactive current injection to suppress converter outlet voltage strategy.

[0047] In the embodiment of the present disclosure, the selection of the ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid includes:

[0048] If the voltage of the power grid is in a transient process of rising and recovering, a Chopper loop suppression strategy and a power grid voltage feedforward response speed acceleration strategy are used to perform high voltage ride-through control of the full power converter;

[0049] If the voltage of the power grid is in a high voltage ride-through steady state process, a high voltage ride-through control of the full power converter is performed by injecting inductive reactive current to suppress the converter outlet voltage strategy.

[0050] Furthermore, the Chopper loop suppression strategy includes:

[0051] When the DC bus voltage connected to the full power converter is greater than the DC load shedding input voltage threshold, the Chopper circuit is controlled to be input;

[0052] When the DC bus voltage connected to the full-power converter is less than the DC load shedding cut-out voltage threshold, the Chopper loop is controlled to be cut out.

[0053] It should be noted that if Figure 2 As shown in the figure, the Chopper circuit is a DC energy consumption circuit controlled by a controllable IGBT element. Its working principle is that the Chopper circuit is connected to the positive and negative poles of the DC bus, and the DC bus voltage of the converter is monitored in real time. When the voltage exceeds the threshold, the IGBT element is controlled to be turned on, and the excess energy on the DC side is consumed by the energy consumption element, so as to achieve the purpose of maintaining the stability of the DC bus voltage.

[0054] When the DC bus voltage is greater than the input threshold, the Chopper circuit is controlled to be input to suppress the DC bus voltage rise; when the DC bus voltage is less than the cut-out threshold, the Chopper circuit is controlled to be cut out. In this way, in the transient state of grid voltage rise or recovery, the load shedding can be quickly put into operation to suppress overvoltage, and in the steady state of grid voltage rise, unnecessary active power consumption can be avoided by load shedding.

[0055] Furthermore, the grid voltage feedforward response speed acceleration strategy includes:

[0056] The voltage and current of the power grid are transformed into a two-phase synchronous rotating coordinate system, and the d-axis voltage component and the q-axis voltage component of the voltage are determined by using a decoupling feedforward and PI closed-loop control method;

[0057] Transforming the d-axis voltage component and the q-axis voltage component of the voltage into a two-phase stationary coordinate system to obtain the voltage component in the two-phase stationary coordinate system;

[0058] The voltage component in the two-phase stationary coordinate system is transformed into a three-phase stationary coordinate system, and then a control voltage vector is obtained through PWM control.

[0059] It should be noted that the grid voltage and grid current are transformed into a two-phase synchronous rotating coordinate system through coordinate transformation, and u in the figure is obtained in the synchronous rotating coordinate system. s Components, and then use decoupling feedforward and PI closed-loop control to obtain ud, u q Voltage component, not using u d Voltage feedforward, change to use u in α coordinate system α , and then transformed to the three-phase stationary coordinate system, the control voltage u is obtained through PWM control c vector, speeds up the feedforward response, improves transient active power absorption, and enhances system stability.

[0060] Furthermore, the strategy of injecting inductive reactive current to suppress the converter outlet voltage includes:

[0061] Obtaining the voltage per unit value range of the power grid;

[0062] Determine a reactive current reference value according to the voltage per unit value range of the power grid and the rated current value of the full-power converter;

[0063] Based on the active current reference value, an inductive reactive current is injected into the full-power converter to suppress the converter outlet voltage.

[0064] It should be noted that the grid-side converter can reduce the voltage at the converter outlet by injecting inductive reactive current, and this method does not require the addition of any hardware. The converter outlet voltage can be reduced by simply controlling the grid-side reactive current to an appropriate value in the converter grid-side control strategy. This method has a very short response time and can start injecting inductive reactive current about 10ms after the fault.

[0065] When the grid voltage per unit value range is 1.1≤U T When ≤1.3, the reactive current conforms to the following formula:

[0066] I q ≤-I N ×1.5×(U T -1.1)

[0067] In the formula, I N is the grid-side converter rated current, U T It is the per unit value of the positive sequence voltage of the power grid. The negative sign “-” represents the inductive reactive current.

[0068] For example, during the high-break steady state, inductive reactive current is injected to support the grid voltage recovery, the grid voltage rises to 1.3pu, and the reactive current reference value I q It can be obtained by the formula Iq=-2680×1.5×(1.3-1.1).

[0069] Step 3: Perform high voltage ride-through control on the full power converter based on the selected ride-through control strategy.

[0070] It should be noted that, for full-power converters, they are generally equipped with Chopper circuits, and the functions of injecting inductive reactive current and accelerating the grid voltage feedforward response speed only require the update of the control software. Therefore, the solution proposed in this article does not require the addition of new hardware, is very low in cost, and is technically easy to implement. For wind turbine manufacturers, the use of full-power converters in conjunction with wind farm-level SVC and other devices and AVC strategies can better cope with the risks brought by high-voltage faults in the grid and provide strong support for the safe operation of the grid.

[0071] In summary, the high voltage ride through control method for a full power converter proposed in this embodiment can better cope with the risks brought by high voltage faults in the power grid and provide strong support for the safe operation of the power grid.

[0072] Embodiment 2

[0073] Figure 3 : is a structural diagram of a full-power converter high voltage ride-through control system provided according to an embodiment of the present application, such as Figure 3 As shown, the system comprises:

[0074] The acquisition module 100 is used to acquire the rated current value, the DC load shedding input voltage threshold, and the DC load shedding cut-out voltage threshold of the full power converter when a high voltage fault occurs in the power grid;

[0075] A selection module 200, configured to select a preset ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid;

[0076] The preset ride-through control strategies include: Chopper loop suppression strategy, grid voltage feedforward response speed acceleration strategy and inductive reactive current injection to suppress converter outlet voltage strategy.

[0077] The control module 300 is configured to perform high voltage ride through control on the full power converter based on a selected ride through control strategy.

[0078] In the embodiment of the present disclosure, the selection module 200 is further used to:

[0079] If the voltage of the power grid is in a transient process of rising and recovering, a Chopper loop suppression strategy and a power grid voltage feedforward response speed acceleration strategy are used to perform high voltage ride-through control of the full power converter;

[0080] If the voltage of the power grid is in a high voltage ride-through steady state process, a high voltage ride-through control of the full power converter is performed by injecting inductive reactive current to suppress the converter outlet voltage strategy.

[0081] Wherein, the Chopper loop suppression strategy includes:

[0082] When the DC bus voltage connected to the full power converter is greater than the DC load shedding input voltage threshold, the Chopper circuit is controlled to be input;

[0083] When the DC bus voltage connected to the full-power converter is less than the DC load shedding cut-out voltage threshold, the Chopper loop is controlled to be cut out.

[0084] The grid voltage feedforward response speed acceleration strategy includes:

[0085] The voltage and current of the power grid are transformed into a two-phase synchronous rotating coordinate system, and the d-axis voltage component and the q-axis voltage component of the voltage are determined by using a decoupling feedforward and PI closed-loop control method;

[0086] Transforming the d-axis voltage component and the q-axis voltage component of the voltage into a two-phase stationary coordinate system to obtain the voltage component in the two-phase stationary coordinate system;

[0087] The voltage component in the two-phase stationary coordinate system is transformed into a three-phase stationary coordinate system, and then a control voltage vector is obtained through PWM control.

[0088] The strategy of injecting inductive reactive current to suppress the converter outlet voltage includes:

[0089] Obtaining the voltage per unit value range of the power grid;

[0090] Determine a reactive current reference value according to the voltage per unit value range of the power grid and the rated current value of the full-power converter;

[0091] Based on the active current reference value, an inductive reactive current is injected into the full-power converter to suppress the converter outlet voltage.

[0092] In summary, the full-power converter high voltage ride-through control system proposed in this embodiment can better cope with the risks brought by high voltage faults in the power grid and provide strong support for the safe operation of the power grid.

[0093] Embodiment 3

[0094] In order to implement the above embodiments, the present disclosure further proposes an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in Embodiment 1 is implemented.

[0095] Embodiment 4

[0096] In order to implement the above embodiments, the present disclosure further proposes a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method described in the first embodiment is implemented.

[0097] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0098] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0099] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A high voltage ride through control method for a full power converter, characterized in that: The method comprises: When a high voltage fault occurs in the power grid, the rated current value, DC load shedding input voltage threshold, and DC load shedding cut-out voltage threshold of the full power converter are obtained; Selecting a preset ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid; High voltage ride-through control is performed on the full power converter based on the selected ride-through control strategy.

2. The method according to claim 1, characterized in that The preset ride-through control strategies include: Chopper loop suppression strategy, grid voltage feedforward response speed acceleration strategy and inductive reactive current injection to suppress converter outlet voltage strategy.

3. The method according to claim 2, characterized in that The selecting of the ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid includes: If the voltage of the power grid is in a transient process of rising and recovering, a Chopper loop suppression strategy and a power grid voltage feedforward response speed acceleration strategy are used to perform high voltage ride-through control of the full power converter; If the voltage of the power grid is in a high voltage ride-through steady state process, a high voltage ride-through control of the full power converter is performed by injecting inductive reactive current to suppress the converter outlet voltage strategy.

4. The method according to claim 3, characterized in that The Chopper loop suppression strategy includes: When the DC bus voltage connected to the full power converter is greater than the DC load shedding input voltage threshold, the Chopper circuit is controlled to be input; When the DC bus voltage connected to the full-power converter is less than the DC load shedding cut-out voltage threshold, the Chopper loop is controlled to be cut out.

5. The method according to claim 3, characterized in that The grid voltage feedforward response speed acceleration strategy includes: The voltage and current of the power grid are transformed into a two-phase synchronous rotating coordinate system, and the d-axis voltage component and the q-axis voltage component of the voltage are determined by using a decoupling feedforward and PI closed-loop control method; Transforming the d-axis voltage component and the q-axis voltage component of the voltage into a two-phase stationary coordinate system to obtain the voltage component in the two-phase stationary coordinate system; The voltage component in the two-phase stationary coordinate system is transformed into a three-phase stationary coordinate system, and then a control voltage vector is obtained through PWM control.

6. The method according to claim 3, characterized in that The strategy of injecting inductive reactive current to suppress the converter outlet voltage includes: Obtaining the voltage per unit value range of the power grid; Determine a reactive current reference value according to the voltage per unit value range of the power grid and the rated current value of the full-power converter; Based on the active current reference value, an inductive reactive current is injected into the full-power converter to suppress the converter outlet voltage.

7. A full power converter high voltage ride through control system, characterized in that: The system comprises: An acquisition module is used to acquire the rated current value, DC load shedding input voltage threshold, and DC load shedding cut-out voltage threshold of the full power converter when a high voltage fault occurs in the power grid; A selection module, used for selecting a preset ride-through control strategy according to the rated current value, the DC load shedding input voltage threshold, the DC load shedding cut-out voltage threshold and the voltage state of the power grid; The control module is used to perform high voltage ride-through control on the full power converter based on a selected ride-through control strategy.

8. The system according to claim 7, characterized in that The preset ride-through control strategies include: Chopper loop suppression strategy, grid voltage feedforward response speed acceleration strategy and inductive reactive current injection to suppress converter outlet voltage strategy.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method according to any one of claims 1 to 6 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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