A method and system for stator current fault suppression of a doubly-fed wind generator

Abstract

The application relates to a stator current fault suppression method and system of a doubly-fed wind power generator, which comprises the following steps: determining the stator current fault condition of the doubly-fed wind power generator according to rotor current and DC bus voltage; and inputting a first low-voltage ride-through protection circuit and / or a second low-voltage ride-through protection circuit according to the stator current fault condition of the doubly-fed wind power generator. The technical scheme provided by the application suppresses the stator fault current of the doubly-fed wind power generator, ensures the stable operation of the wind power generator set, and avoids the phenomenon that the set is not controlled for a long time and the resistance energy consumption exceeds the limit due to the multiple inputs of the protection circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected new energy power generation units, and in particular to a method and system for suppressing stator current faults of a doubly-fed wind turbine generator. Background Art

[0002] Under the condition of deep voltage drop at the machine end, the peak value of the stator and rotor fault current of the unit is larger.

[0003] Typically, the method of activating the low voltage ride-through protection circuit is used to suppress the stator and rotor fault current of the wind turbine generator set. However, the low voltage ride-through protection strategy has limited effect on suppressing the above-mentioned stator fault current. The lack of effective damping in the fault circuit causes the stator fault current and stator flux to decay slowly. The transient transition process of the unit after the fault lasts for a long time, which is very likely to cause the protection circuit to be activated multiple times, resulting in the unit being out of control for a long time.

[0004] At present, no solution has been proposed that can effectively solve the unstable operation of wind turbines caused by excessive stator and rotor fault currents. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to propose a method for suppressing stator current fault of a doubly fed wind turbine. The method effectively suppresses the stator fault current of the doubly fed wind turbine, ensures the stable operation of the wind turbine generator set, and avoids the phenomenon of the unit being out of control for a long time and the resistance energy consumption exceeding the limit due to multiple activation of the protection circuit as a whole.

[0006] The purpose of the present invention is achieved by adopting the following technical solutions:

[0007] The present invention provides a method for suppressing stator current faults of a doubly-fed wind turbine generator, the improvement of which lies in that the method comprises:

[0008] Determine the stator current fault condition of the doubly-fed wind turbine generator based on the rotor current and DC bus voltage;

[0009] The first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit are activated according to the stator current fault condition of the doubly fed wind generator.

[0010] Preferably, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are both Crowbar protection circuits.

[0011] Furthermore, the determining of the stator current fault condition of the doubly-fed wind turbine generator according to the rotor current and the DC bus voltage includes:

[0012] When U dc >U dc,max And Ir,max2 r r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition;

[0013] When U dc >U dc,max And I r >I r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition;

[0014] Among them, I r is the rotor current of the doubly fed wind turbine generator, Ir max1 is the first low voltage ride through protection circuit action limit, Ir max2 is the second low voltage ride through protection circuit action limit, U dc is the DC bus voltage, U dc,max is the maximum DC bus voltage.

[0015] Furthermore, the step of activating the first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit according to the stator current fault condition of the doubly fed wind turbine generator comprises:

[0016] When the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is activated, and after a delay of Δt1 or Δt2, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is exited;

[0017] When the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is first activated, and after a delay of Δt1 or Δt2, the second low voltage ride through protection circuit or the first low voltage ride through protection circuit is activated, and after a delay of Δt2 or Δt1, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are exited.

[0018] Δt1 is the activation time of the first LVRT protection circuit, and Δt2 is the activation time of the second LVRT protection circuit.

[0019] Furthermore, the equivalent resistance of the first low voltage ride through protection circuit is equal to the equivalent resistance of the second low voltage ride through protection circuit.

[0020] The present invention provides a stator current fault suppression system for a doubly-fed wind turbine generator, the improvement of which lies in that the system comprises:

[0021] a determination module, configured to determine a stator current fault condition of the doubly-fed wind turbine generator according to the rotor current and the DC bus voltage;

[0022] ​​The input module is used to input the first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit according to the stator current fault condition of the doubly fed wind turbine generator.

[0023] Preferably, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are both Crowbar protection circuits.

[0024] Furthermore, the determining module is used to:

[0025] When U dc >U dc,max And I r,max2 r r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition;

[0026] When U dc >U dc,max And I r >I r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition;

[0027] Among them, I r is the rotor current of the doubly fed wind turbine generator, Ir max1 is the first low voltage ride through protection circuit action limit, Ir max2 is the second low voltage ride through protection circuit action limit, U dc is the DC bus voltage, U dc,max is the maximum DC bus voltage.

[0028] Furthermore, the input module is used to:

[0029] When the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is activated, and after a delay of Δt1 or Δt2, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is exited;

[0030] When the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is first activated, and after a delay of Δt1 or Δt2, the second low voltage ride through protection circuit or the first low voltage ride through protection circuit is activated, and after a delay of Δt2 or Δt1, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are exited.

[0031] Δt1 is the activation time of the first LVRT protection circuit, and Δt2 is the activation time of the second LVRT protection circuit.

[0032] ​​Furthermore, the equivalent resistance of the first low voltage ride through protection circuit is equal to the equivalent resistance of the second low voltage ride through protection circuit.

[0033] Compared with the closest prior art, the present invention has the following beneficial effects:

[0034] The technical solution provided by the present invention determines the stator current fault condition of the doubly-fed wind turbine generator based on the rotor current and the DC bus voltage; activates the first low voltage ride-through protection circuit and / or the second low voltage ride-through protection circuit according to the stator current fault condition of the doubly-fed wind turbine generator; effectively suppresses the stator fault current of the doubly-fed wind turbine generator, ensures the stable operation of the wind turbine generator set, and avoids the phenomenon of the unit being out of control for a long time and the resistance energy consumption exceeding the limit caused by the protection circuit being activated multiple times as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of a method for suppressing stator current fault of a doubly-fed wind turbine generator;

[0036] Figure 2 The present invention is a structural diagram of a stator current fault suppression system of a doubly-fed wind turbine generator. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0039] The present invention provides a method for suppressing stator current fault of a doubly-fed wind turbine generator, such as Figure 1 As shown, the method includes:

[0040] Step 101: Determine a stator current fault condition of a doubly-fed wind turbine generator according to the rotor current and the DC bus voltage;

[0041] Step 102: Activate the first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit according to the stator current fault condition of the doubly fed wind turbine generator.

[0042] Specifically, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are both Crowbar protection circuits.

[0043] Furthermore, the step 101 includes:

[0044] When U dc >U dc,max And I r,max2 r r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition;

[0045] When U dc >U dc,max And I r >I r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition;

[0046] Among them, I r is the rotor current of the doubly fed wind turbine generator, Ir max1 is the first low voltage ride through protection circuit action limit, Ir max2 is the second low voltage ride through protection circuit action limit, U dc is the DC bus voltage, U dc,max is the maximum DC bus voltage.

[0047] In the best embodiment of the present invention, it is necessary to monitor the rotor current and DC bus voltage of the wind turbine generator set in real time before step 101; the action limit of the protection circuit in the present invention is set according to the actual working conditions.

[0048] Furthermore, the step 102 includes:

[0049] When the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is activated, and after a delay of Δt1 or Δt2, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is exited;

[0050] In the best embodiment of the present invention, at the moment of fault occurrence, U dc >U dc,max And I r,max2 r r,max1 At this time, it indicates that the electromagnetic torque amplitude of the wind turbine generator set exceeds the limit and the low voltage ride through protection circuit needs to be activated. However, since the limit is not exceeded, the low voltage ride through protection circuit is activated into the second-level protection circuit, which mainly increases the energy consumption of the protection circuit, absorbs excess energy, delays Δt2, and exits the low voltage ride through protection circuit.

[0051] ​​​​When the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is first activated, and after a delay of Δt1 or Δt2, the second low voltage ride through protection circuit or the first low voltage ride through protection circuit is activated, and after a delay of Δt2 or Δt1, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are exited.

[0052] In the best embodiment of the present invention, at the moment of fault occurrence, if U dc >U dc,max And I r >I r,max1 This indicates high rotor current and electromagnetic torque amplitudes, necessitating activation of the low-voltage ride-through protection circuit. The first low-voltage ride-through protection circuit is activated first, primarily to limit the fault current amplitude and reduce the impact damage of electromagnetic torque on the shaft system. After the fault current decays over a certain period of time (this time is determined by the rotor fault current decay characteristics), the second low-voltage ride-through protection circuit is activated, primarily to increase the protection circuit's energy consumption and absorb excess energy. Both circuits are set based on a fixed activation time. Δt1 and Δt2 are set based on actual operating conditions.

[0053] Δt1 is the activation time of the first LVRT protection circuit, and Δt2 is the activation time of the second LVRT protection circuit.

[0054] Specifically, the equivalent resistance of the first low voltage ride through protection circuit is equal to the equivalent resistance of the second low voltage ride through protection circuit.

[0055] The present invention provides a stator current fault suppression system for a doubly-fed wind turbine generator, such as Figure 2 As shown, the system includes:

[0056] a determination module, configured to determine a stator current fault condition of the doubly-fed wind turbine generator according to the rotor current and the DC bus voltage;

[0057] The input module is used to input the first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit according to the stator current fault condition of the doubly fed wind turbine generator.

[0058] Specifically, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are both Crowbar protection circuits.

[0059] Furthermore, the determining module is used to:

[0060] When U dc >U dc,max And I r,max2 r r,max1 ​​When , the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition;

[0061] When U dc >U dc,max And I r >I r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition;

[0062] Among them, I r is the rotor current of the doubly fed wind turbine generator, Ir max1 is the first low voltage ride through protection circuit action limit, Ir max2 is the second low voltage ride through protection circuit action limit, U dc is the DC bus voltage, U dc,max is the maximum DC bus voltage.

[0063] Furthermore, the input module is used to:

[0064] When the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is activated, and after a delay of Δt1 or Δt2, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is exited;

[0065] When the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is first activated, and after a delay of Δt1 or Δt2, the second low voltage ride through protection circuit or the first low voltage ride through protection circuit is activated, and after a delay of Δt2 or Δt1, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are exited.

[0066] Δt1 is the activation time of the first LVRT protection circuit, and Δt2 is the activation time of the second LVRT protection circuit.

[0067] Furthermore, the equivalent resistance of the first low voltage ride through protection circuit is equal to the equivalent resistance of the second low voltage ride through protection circuit.

[0068] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0069] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0070] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0071] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for suppressing stator current fault of a doubly-fed wind turbine generator, characterized in that: The method comprises: Determine the stator current fault condition of the doubly-fed wind turbine generator based on the rotor current and DC bus voltage; activating a first low voltage ride through protection circuit and / or a second low voltage ride through protection circuit according to a stator current fault condition of the doubly-fed wind turbine generator; Determining the stator current fault condition of the doubly-fed wind turbine generator according to the rotor current and the DC bus voltage includes: When U dc >U dc,max And I r,max2 r r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition;​​ When U dc >U dc,max And I r >I r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition; Among them, I r is the rotor current of the doubly fed wind turbine generator, Ir max1 is the first low voltage ride through protection circuit action limit, Ir max2 is the second low voltage ride through protection circuit action limit, U dc is the DC bus voltage, U dc,max is the maximum value of DC bus voltage; The method of activating the first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit according to the stator current fault condition of the doubly fed wind turbine generator comprises: When the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is activated, and after a delay of Δt1 or Δt2, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is exited; When the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is first activated, and after a delay of Δt1 or Δt2, the second low voltage ride through protection circuit or the first low voltage ride through protection circuit is activated, and after a delay of Δt2 or Δt1, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are deactivated; Δt1 is the activation time of the first LVRT protection circuit, and Δt2 is the activation time of the second LVRT protection circuit.

2. The method according to claim 1, wherein The first low voltage ride through protection circuit and the second low voltage ride through protection circuit are both Crowbar protection circuits.

3. The method according to claim 1, wherein The equivalent resistance of the first low voltage ride through protection circuit is equal to the equivalent resistance of the second low voltage ride through protection circuit.

4. A stator current fault suppression system for a doubly-fed wind turbine generator, characterized in that: The system comprises: a determination module, configured to determine a stator current fault condition of the doubly-fed wind turbine generator according to the rotor current and the DC bus voltage; An input module, configured to input the first low voltage ride through protection circuit and / or the second low voltage ride through protection circuit according to a stator current fault condition of the doubly-fed wind turbine generator; The determining module is configured to: When U dc >U dc,max And I r,max2 r r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition;​​ When U dc >U dc,max And I r >I r,max1 When , the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition; Among them, I r is the rotor current of the doubly fed wind turbine generator, Ir max1 is the first low voltage ride through protection circuit action limit, Ir max2 is the second low voltage ride through protection circuit action limit, U dc is the DC bus voltage, U dc,max is the maximum value of DC bus voltage; The input module is used to: When the stator current fault condition of the doubly-fed wind turbine generator is the first fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is activated, and after a delay of Δt1 or Δt2, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is exited; When the stator current fault condition of the doubly-fed wind turbine generator is the second fault condition, the first low voltage ride through protection circuit or the second low voltage ride through protection circuit is first activated, and after a delay of Δt1 or Δt2, the second low voltage ride through protection circuit or the first low voltage ride through protection circuit is activated, and after a delay of Δt2 or Δt1, the first low voltage ride through protection circuit and the second low voltage ride through protection circuit are deactivated; Δt1 is the activation time of the first LVRT protection circuit, and Δt2 is the activation time of the second LVRT protection circuit.

5. The system according to claim 4, wherein: The first low voltage ride through protection circuit and the second low voltage ride through protection circuit are both Crowbar protection circuits.

6. The system according to claim 4, wherein: The equivalent resistance of the first low voltage ride through protection circuit is equal to the equivalent resistance of the second low voltage ride through protection circuit.

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