Wind turbine generator set and wind farm control method and equipment

Abstract

The present disclosure provides a control method and device for a wind turbine generator set and a wind farm. The control method includes: when the fault ride-through flag of the wind turbine generator set is not set, if a voltage drop or voltage rise fault is detected in the power grid, the fault ride-through flag of the wind turbine generator set is set, and the reactive current control mode is switched from the voltage control mode to the fault ride-through mode; when the fault ride-through flag of the wind turbine generator set is set and in the fault ride-through mode, if the power grid voltage is detected to be restored to a preset range, the reactive current control mode is switched from the fault ride-through mode to the voltage control mode; when the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, if the machine-end voltage meets a preset condition, the ride-through flag is released, wherein, in the voltage control mode, the reactive current output target value is determined based on the machine-end voltage target value.

Description

Technical Field

[0001] The present disclosure generally relates to the field of wind power technology, and more specifically, to a control method and device for a wind turbine generator set and a wind farm. Background Art

[0002] Large-scale wind turbines are centrally connected to the power system, and the low voltage ride-through capability and high voltage ride-through capability of the wind turbines are very important capabilities.

[0003] Low voltage ride-through means: when the voltage at the grid connection point drops due to power system accidents or disturbances, the wind turbine generator set can ensure continuous operation without disconnecting from the grid within the specified voltage drop range and time interval. High voltage ride-through means: when the voltage at the grid connection point increases due to power grid accidents or disturbances, the wind turbine generator set can ensure continuous operation without disconnecting from the grid within the specified voltage increase range and time interval. Summary of the invention

[0004] An exemplary embodiment of the present disclosure is to provide a control method and device for a wind turbine generator set and a wind farm, which can effectively control the wind turbine generator set to complete low voltage ride-through and high voltage ride-through.

[0005] According to an exemplary embodiment of the present disclosure, a control method for a wind turbine generator set is provided, the control method comprising: when a fault ride-through flag of the wind turbine generator set is not set, if a voltage drop or voltage rise fault is detected in the power grid, the fault ride-through flag of the wind turbine generator set is set, and the reactive current control mode is switched from the voltage control mode to the fault ride-through mode; when the fault ride-through flag of the wind turbine generator set is set and is in the fault ride-through mode, if the power grid voltage is detected to be restored to a preset range, the reactive current control mode is switched from the fault ride-through mode to the voltage control mode; when the fault ride-through flag of the wind turbine generator set is set and is in the voltage control mode, if the machine-end voltage meets a preset condition, the ride-through flag is released, wherein, in the voltage control mode, the reactive current output target value is determined based on the machine-end voltage target value, and the machine-end voltage target value is determined based on the reactive control command received from the wind farm controller.

[0006] Optionally, when the fault ride-through flag of the wind turbine generator set is set and is in voltage control mode, the machine-end voltage target value remains the machine-end voltage target value determined last time before the fault ride-through flag is set; when the fault ride-through flag of the wind turbine generator set is not set and is in voltage control mode, the machine-end voltage target value is determined based on the reactive power control command currently received from the wind farm controller.

[0007] Optionally, the control method further includes: when the fault ride-through flag of the wind turbine generator set is set and is in the voltage control mode, if it is monitored that the power grid has a voltage drop or voltage rise fault again, the reactive current control mode is switched from the voltage control mode to the fault ride-through mode.

[0008] Optionally, the step of releasing the position of the through-flag includes: if the machine-end voltage meets a preset condition and a notification is received from the wind farm controller allowing the unit to release the position of the fault through-flag, then releasing the position of the through-flag, wherein the control method also includes: when the fault through-flag of the wind turbine generator set is set and is in a voltage control mode, if the machine-end voltage meets a preset condition, then sending a notification to the wind farm controller allowing the wind farm to release the position of the fault through-flag.

[0009] Optionally, the preset conditions include: the machine-end voltage reaches the machine-end voltage target value, or the machine-end voltage remains unchanged for a preset time period; and / or, the control method also includes: when the fault-through flag of the wind turbine generator set is set, notifying the wind farm controller that the fault-through flag has been set.

[0010] Optionally, the control method also includes: when it is monitored that the grid voltage is lower than a first preset threshold, locking the grid phase, and simulating and generating the real-time phase of the grid based on the locked grid phase changing over time; when it is monitored that the grid voltage is lower than a second preset threshold, using the simulated real-time phase of the grid as the current grid phase, wherein the second preset threshold is smaller than the first preset threshold.

[0011] Optionally, in the voltage control mode, the reactive current output target value is determined in the following manner: based on the reactive power output target value in the reactive control command received from the wind farm controller and the machine-end voltage set value, the machine-end voltage target value is determined; based on the machine-end voltage target value and the reactive power measurement value of the wind turbine generator set, the reactive current output target value is determined.

[0012] Optionally, the step of determining the reactive current output target value based on the machine-end voltage target value and the reactive power measurement value of the wind turbine generator set includes: inputting the reactive power measurement value of the wind turbine generator set into a droop controller, and determining the reactive current output target value based on the difference between the machine-end voltage target value and the output of the droop controller.

[0013] Optionally, in the voltage control mode, the reactive current output target value is determined in the following manner: the difference between the reactive power output target value in the reactive control command received from the wind farm controller and the reactive power measurement value is input into the first PI regulator, wherein the first PI regulator is set with an output upper limit value and an output lower limit value; the sum of the output of the first PI regulator and the machine-end voltage set value in the reactive control command received from the wind farm controller is used as the machine-end voltage target value; the reactive power measurement value of the wind turbine generator set is input into the droop controller; the difference between the machine-end voltage target value and the output of the droop controller is input into the second PI regulator after subtracting the machine-end voltage measurement value, and the output of the second PI regulator is used as the reactive current output target value component on the q-axis of the two-phase synchronous rotating coordinate system, wherein the second PI regulator is set with an output upper limit value and an output lower limit value.

[0014] Optionally, in the fault ride-through mode, the reactive current output target value is determined based on the low voltage ride-through reactive current K coefficient or the high voltage ride-through reactive current K coefficient received from the wind farm controller, wherein the control method also includes: when the fault ride-through flag of the wind turbine generator set is not set, receiving and updating the low voltage ride-through reactive current K coefficient and / or the high voltage ride-through reactive current K coefficient from the wind farm controller, wherein the low voltage ride-through reactive current K coefficient and / or the high voltage ride-through reactive current K coefficient are determined by the wind farm controller based on at least one of the following items: the grid connection point system impedance, the impedance of the transformer and the line in the wind farm, and the capacity of the wind farm grid-connected units, wherein the grid connection point system impedance is inversely correlated with the magnitude of the low voltage ride-through reactive current K coefficient and / or the high voltage ride-through reactive current K coefficient.

[0015] According to another exemplary embodiment of the present disclosure, a control method for a wind farm is provided, the control method comprising: when a fault ride-through flag of the wind farm is not set, generating and sending a reactive control command to a wind turbine generator set of the wind farm; when a voltage drop or voltage rise fault is detected in the power grid, setting the fault ride-through flag and stopping generating reactive control commands, wherein the reactive control commands include reactive control commands for transmitting a set value of voltage at the generator end and a target value of reactive power output.

[0016] Optionally, the control method further comprises: setting the fault-through flag when receiving notifications from a first predetermined number of wind turbine generator sets that the wind turbine generator sets have set the fault-through flag.

[0017] Optionally, the control method also includes: when the fault ride-through flag of the wind farm has been set and the grid voltage is monitored to recover to within a preset range, sending a notification to the wind turbine generator set allowing the wind turbine generator set to release the fault ride-through flag position; when the fault ride-through flag of the wind farm has been set, the grid voltage is monitored to recover to within the preset range and a notification from a second predetermined number of wind turbine generator sets allowing the wind farm to release the fault ride-through flag position is received, releasing the fault ride-through flag position.

[0018] Optionally, the reactive control command also includes a reactive control command for sending a low voltage ride-through reactive current K coefficient and / or a high voltage ride-through reactive current K coefficient, wherein the control method also includes: when the fault ride-through flag of the wind farm is not set, based on the grid connection point system impedance, the impedance of the transformer and the line in the wind farm, and the capacity of the wind farm grid-connected units, determining and sending the low voltage ride-through reactive current K coefficient and / or the high voltage ride-through reactive current K coefficient, wherein the grid connection point system impedance is inversely correlated with the magnitude of the low voltage ride-through reactive current K coefficient and / or the high voltage ride-through reactive current K coefficient.

[0019] Optionally, the control method also includes: determining the wind turbine generator set in the island operation state based on the shutdown status of the grid connection point circuit breaker, the wind farm line circuit breaker, and the unit box transformer circuit breaker and the grid connection point system impedance; and sending a shutdown command to the wind turbine generator set in the island operation state.

[0020] According to another exemplary embodiment of the present disclosure, a control device of a wind turbine generator set is provided, the control device comprising: a flag setting unit, when a fault ride-through flag of the wind turbine generator set is not set, if a voltage drop or voltage rise fault is detected in the power grid, the fault ride-through flag of the wind turbine generator set is set; a mode switching unit, when the fault ride-through flag of the wind turbine generator set is set, the reactive current control mode is switched from the voltage control mode to the fault ride-through mode; wherein, when the fault ride-through flag of the wind turbine generator set is set and is in the fault ride-through mode, if the power grid voltage is detected to be restored to a preset range, the reactive current control mode is switched from the fault ride-through mode to the voltage control mode; wherein, when the fault ride-through flag of the wind turbine generator set is set and is in the voltage control mode, if the machine-end voltage meets a preset condition, the flag setting unit releases the ride-through flag position, wherein, in the voltage control mode, the reactive current output target value is determined based on the machine-end voltage target value, and the machine-end voltage target value is determined based on the reactive control command received from the wind farm controller.

[0021] According to another exemplary embodiment of the present disclosure, a control device for a wind farm is provided, the control device comprising: a reactive control command generating unit, which generates a reactive control command to be sent to a wind turbine generator set in the wind farm when a fault ride-through flag of the wind farm is not set; a reactive control command sending unit, which sends a reactive control command to the wind turbine generator set in the wind farm; and a flag setting unit, which sets a fault ride-through flag when a voltage drop or voltage rise fault is detected in the power grid, wherein the reactive control command generating unit stops generating reactive control commands when the fault ride-through flag of the wind farm is set, wherein the reactive control commands include reactive control commands for a transmitter-end voltage set value and a reactive power output target value.

[0022] According to another exemplary embodiment of the present disclosure, a control device of a wind turbine generator set is provided, the control device comprising: a processor; a memory storing a computer program, and when the computer program is executed by the processor, the control method of the wind turbine generator set as described above is implemented.

[0023] According to another exemplary embodiment of the present disclosure, a control device of a wind farm is provided, the control device comprising: a processor; a memory storing a computer program, and when the computer program is executed by the processor, the control method of the wind farm as described above is implemented.

[0024] According to the control method and device of the wind turbine generator set and wind farm of the exemplary embodiment of the present disclosure, a voltage control mode, a reactive current control mode, is proposed, and how to switch between the voltage control mode and the fault ride-through mode is defined. Thus, the adaptability of the wind farm to the operation of the low short-circuit ratio power grid is improved; it can ensure that the unit can successfully ride through the continuous low voltage-high voltage, continuous low voltage-low voltage, continuous high voltage-high voltage, and continuous high voltage-low voltage; it ensures that the fault ride-through state of the wind farm and the wind turbine generator set is consistent, so that the unit and the wind farm controller can cooperate well in various states.

[0025] Additional aspects and / or advantages of the present general inventive concept will be set forth in part in the following description and in part will be apparent from the description or may be learned through practice of the present general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects and features of the exemplary embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings which exemplarily illustrate the embodiments, in which:

[0027] Figure 1 A flow chart showing a control method of a wind turbine generator set according to an exemplary embodiment of the present disclosure;

[0028] Figure 2A flowchart showing a method for determining a reactive current output target value according to an exemplary embodiment of the present disclosure;

[0029] Figure 3 An example of determining a reactive current output target value according to an exemplary embodiment of the present disclosure is shown;

[0030] Figure 4 A flow chart showing a method for controlling a wind farm according to an exemplary embodiment of the present disclosure;

[0031] Figure 5 An example of a control method of a wind farm and a wind turbine generator set according to an exemplary embodiment of the present disclosure is shown;

[0032] Figure 6 A structural block diagram showing a control device of a wind turbine generator set according to an exemplary embodiment of the present disclosure;

[0033] Figure 7 A structural block diagram of a wind farm control device according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0034] Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments will be described below with reference to the drawings in order to explain the present disclosure.

[0035] Figure 1 A flow chart showing a control method of a wind turbine generator set according to an exemplary embodiment of the present disclosure is shown. As an example, the control method may be executed by a wind turbine generator set (eg, a control device of the wind turbine generator set).

[0036] Reference Figure 1 In step S101, when the fault ride-through flag of the wind turbine generator set is not set, if a voltage drop or voltage rise fault is detected in the power grid, the fault ride-through flag of the wind turbine generator set is set, and the reactive current control mode is switched from the voltage control mode to the fault ride-through mode.

[0037] As an example, when the fault ride-through flag of the wind turbine generator set is not set, the reactive current control mode of the wind turbine generator set is the voltage control mode.

[0038] As an example, in the voltage control mode, the reactive current output target value (i.e., the reactive current output set value) is determined based on the machine-end voltage target value, and the machine-end voltage target value is determined based on the reactive control command received from the wind farm controller. That is, according to an exemplary embodiment of the present disclosure, the reactive current output target value is related to the machine-end voltage target value, and the reactive current output target value needs to be set with reference to the machine-end voltage target value.

[0039] As an example, the machine-end voltage target value may be determined based on the reactive power output target value in the reactive control command received from the wind farm controller and the machine-end voltage given value. Further, as an example, in the voltage control mode, the machine-end voltage target value may be determined based on the reactive power output target value in the reactive control command received from the wind farm controller and the machine-end voltage given value; then, the reactive current output target value may be determined based on the machine-end voltage target value and the reactive power measurement value of the wind turbine. As an example, the reactive power measurement value of the wind turbine may be input into the droop controller, and the reactive current output target value may be determined based on the difference between the machine-end voltage target value and the output of the droop controller.

[0040] As an example, various appropriate methods can be used to monitor whether a voltage drop or voltage increase fault occurs in the power grid. For example, the terminal voltage can be used to monitor whether a voltage drop or voltage increase fault occurs in the power grid. The terminal voltage can be the voltage at the output end of the wind turbine generator set.

[0041] As an example, in the fault ride-through mode, the reactive current output target value may be determined based on the low voltage ride-through reactive current K factor or the high voltage ride-through reactive current K factor received from the wind farm controller. For example, in the fault ride-through mode, the reactive current output target value component on the q-axis of the two-phase synchronous rotating coordinate system may be: rated current value*K factor*△U, wherein the K factor is the low voltage ride-through reactive current K factor or the high voltage ride-through reactive current K factor (it should be understood that the low voltage ride-through reactive current K factor is used during low voltage ride-through, and the high voltage ride-through reactive current K factor is used during high voltage ride-through), and △U indicates the depth of grid voltage drop or rise.

[0042] As an example, the control method of the wind turbine generator set according to the exemplary embodiment of the present disclosure may further include: when the fault ride-through flag of the wind turbine generator set is not set, receiving and updating the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor from the wind farm controller. For example, the low voltage ride-through reactive current K factor K_LVRT and / or the high voltage ride-through reactive current K factor K_HVRT may be periodically received, and the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor may be updated to the latest received.

[0043] As an example, the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor may be determined by the wind farm controller based on at least one of the following items: the grid connection point system impedance, the impedance of the transformer and line in the wind farm, and the capacity of the wind farm grid-connected units, so that the units have reasonable high and low voltage ride-through reactive current K factors.

[0044] As an example, the grid connection point system impedance is inversely correlated with the magnitude of the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor. Specifically, the greater the grid connection point system impedance, the smaller the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor; the smaller the grid connection point short-circuit capacity, the larger the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor. That is, the greater the grid connection point short-circuit capacity, the greater the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor; the smaller the grid connection point short-circuit capacity, the smaller the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor.

[0045] In step S102, when the fault ride-through flag of the wind turbine generator set is set and in the fault ride-through mode, if it is monitored that the grid voltage recovers to within a preset range, the reactive current control mode is switched from the fault ride-through mode to the voltage control mode.

[0046] It should be understood that when the fault ride-through flag of the wind turbine generator set is set, the reactive current control mode of the wind turbine generator set may be a voltage control mode or a fault ride-through mode, depending on whether the grid voltage is within a preset range.

[0047] As an example, when the fault ride-through flag of a wind turbine generator set is set and is in a voltage control mode, the machine-end voltage target value remains the machine-end voltage target value determined last time before the fault ride-through flag is set; when the fault ride-through flag of a wind turbine generator set is not set and is in a voltage control mode, the machine-end voltage target value may be determined based on a reactive power control command currently received from a wind farm controller (i.e., a reactive power control command received in real time).

[0048] As an example, the preset range may be: greater than or equal to 0.8 pu and less than or equal to 1.15 pu. It should be understood that the reference value of the per-unit value involved in the present disclosure may be the rated voltage value of the machine end.

[0049] In step S103, when the fault ride-through flag of the wind turbine generator set is set and is in the voltage control mode, if the generator terminal voltage meets a preset condition, the ride-through flag is cleared.

[0050] As an example, the preset condition may include: the machine-side voltage remains stable. For example, the preset condition may include: the machine-side voltage reaches the machine-side voltage target value, or the machine-side voltage remains unchanged within a preset time (that is, although the machine-side voltage is unable to reach the machine-side voltage target value, it has remained stable). For example, the preset time may be set to 2s.

[0051] According to an exemplary embodiment of the present disclosure, since the voltage control mode uses the machine-end voltage as the control target to determine the reactive current output target value, it can automatically balance the influence of active and reactive power on the machine-end voltage to ensure the stability of the unit port voltage within the machine-end voltage range of 0.8-1.15pu, and can enable the timely recovery of the inductive reactive power before re-entering the low crossing or the capacitive reactive power before re-entering the high crossing during the continuous crossing process.

[0052] As an example, when the fault ride-through flag of a wind turbine generator set is set and in voltage control mode, if the terminal voltage meets the preset conditions and a notification is received from the wind farm controller allowing the generator set to release the fault ride-through flag, the ride-through flag can be released. This allows the wind farm and wind turbine generator set to have consistent fault ride-through states, so that the generator set and wind farm controller can cooperate well in various states.

[0053] In addition, as an example, the control method of a wind turbine generator set according to an exemplary embodiment of the present disclosure may also include: when the fault ride-through flag of the wind turbine generator set is set and is in a voltage control mode, if the terminal voltage meets a preset condition, a notification allowing the wind farm to release the fault ride-through flag position may be sent to the wind farm controller.

[0054] In addition, as an example, the control method of the wind turbine generator set according to the exemplary embodiment of the present disclosure may further include: when the fault ride-through flag of the wind turbine generator set is set, the wind farm controller may be notified that the wind turbine generator set has set the fault ride-through flag. That is, the wind farm controller is notified that the wind turbine generator set has entered the fault ride-through state, so that the wind farm controller will not cause a significant change in the reactive power control command due to the voltage mutation caused by the grid fault.

[0055] In addition, as an example, the control method of the wind turbine generator set according to the exemplary embodiment of the present disclosure may further include: when the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, if it is detected that the power grid has a voltage drop or voltage rise fault again, the reactive current control mode is switched from the voltage control mode to the fault ride-through mode. For example, when a fault ride-through has ended and has been switched from the fault ride-through mode to the voltage control mode, if it is detected that the power grid has a voltage drop or voltage rise fault again, it returns to the voltage control mode again, and since the fault ride-through flag has been set at this time, it does not need to be set again.

[0056] The present disclosure takes into account that if the terminal voltage of the unit is low, a serious short circuit fault may occur at this time, and the phase collected by the unit port will gradually deviate from the true grid phase. When the grid voltage begins to recover, if the collected phase is used to gradually track the grid phase, active and reactive deviations may occur, and even negative active phenomena may occur. Therefore, as an example, the control method of the wind turbine generator set according to the exemplary embodiment of the present disclosure may also include: when it is monitored that the grid voltage is lower than the first preset threshold, the grid phase is locked, and the real-time phase of the grid is simulated and generated based on the locked grid phase over time (that is, the locked grid phase is used as a reference to simulate the grid phase over time, so that the real-time phase of the grid can be simulated); when the grid voltage is monitored to be lower than the second preset threshold, the real-time phase of the simulated grid is used as the current grid phase; when the grid voltage is monitored to be not lower than the second preset threshold, the real-time monitored grid phase is directly used, wherein the second preset threshold is less than the first preset threshold. For example, the first preset threshold can be set to 0.9pu, and the second preset threshold can be set to 0.5pu.

[0057] In addition, as an example, the control method of the wind turbine generator set according to the exemplary embodiment of the present disclosure may further include: when switching from the fault ride-through mode to the voltage control mode, the active power is restored. According to the exemplary embodiment of the present disclosure, when the grid voltage is restored, the reactive power is restored first, and after the grid voltage and reactive power are stable, the active power is gradually restored. Through the delayed restoration of the active power, the deviation of the active output and the reactive output is avoided, and even the negative active power phenomenon is avoided.

[0058] Figure 2 A flow chart showing a method for determining a reactive current output target value according to an exemplary embodiment of the present disclosure is shown. In the voltage control mode, the reactive current output target value can be determined in this way.

[0059] Reference Figure 2 and Figure 3 In step S1011, the reactive power output target value Q in the reactive power control command received from the wind farm controller is Cmd1_WT and reactive power measurement value Q measure The difference between the actual measured value of the reactive power output is input to the first PI regulator, wherein the first PI regulator is set with an output upper limit value V max And the output lower limit value V min For example, V max Can be +0.05pu, V min It can be -0.05 pu. That is, the first PI regulator is a limiting PI regulator.

[0060] In step S1012, the output of the first PI regulator is compared with the terminal voltage set value V in the reactive power control command received from the wind farm controller. set1 The sum of the two is taken as the target value of the terminal voltage V ref For example, the terminal voltage given value V set1 The value range is: 0.91pu-1.09pu.

[0061] It should be understood that Q Cmd1_WT and V set1 It can be obtained from the same reactive power control command or from different reactive power control commands. For example, a reactive power control command is used to send Q Cmd1_WT , another reactive control command is used to send V set1 .

[0062] In step S1013, the reactive power measurement value Q of the wind turbine generator set is measure The output of the droop controller can be, for example, the reactive power measurement Q measure The product of the droop coefficient K.

[0063] In step S1014, the terminal voltage target value V ref The difference between the output of the droop controller and the measured value of the terminal voltage V measure Then it is input to the second PI regulator, and the output of the second PI regulator is used as the reactive current output target value component I on the q axis of the two-phase synchronous rotating coordinate system. qref , where the second PI regulator is set with an output upper limit I q_max And the output lower limit value I q_min That is, the second PI regulator is a limiting PI regulator.

[0064] In addition, as an example, in both the fault ride-through mode and the voltage control mode, the reactive current output target value component I on the d-axis of the two-phase synchronous rotating coordinate system can be determined by the following method: dref :The DC voltage target value V of the wind turbine generator set dcref The DC voltage measurement value V dc The difference between the two is input to the third PI regulation, and the output of the third PI regulation is used as the reactive current output target value component I on the d-axis of the two-phase synchronous rotating coordinate system. dref , where the third PI regulator is set with an output upper limit I d_ref_max And the output lower limit value I d_ref_min The DC voltage of the wind turbine generator set is the voltage across the DC capacitor of the wind turbine generator set.

[0065] As an example, when the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, steps S1011 and S1012 can be omitted, and in step S1014, the last determined target value of the terminal voltage before the fault ride-through flag is set is directly used to determine I qref When the fault ride-through flag of the wind turbine generator set is not set and is in the voltage control mode, steps S1011 to S1014 are executed based on the reactive power control command currently received from the wind farm controller.

[0066] In fact, the existing technology has such a problem: in areas with weak power grids, active and reactive power have a greater impact on the grid voltage, especially in Northwest China, Northeast China and Inner Mongolia, where multiple UHV DC transmission lines have been installed and the systems have been put into operation one after another. The local renewable energy power transmission power has increased, but at the same time, the short-circuit capacity of the system has been reduced, resulting in a reduction in the ability of the unit to cope with grid disturbances. Considering the above problems in the existing technology: the present disclosure proposes that the unit adopts a voltage closed-loop control strategy when determining the reactive current output target value based on the terminal voltage target value in the voltage control mode, and adds a droop link with reactive power measurement value as input, which can avoid the reactive tug-of-war problem between different units in the wind farm; and the setting of the low voltage crossing reactive current K coefficient and / or the high voltage crossing reactive current K coefficient fully considers the system impedance of the grid connection point, so that it can automatically balance the impact of active and reactive power on the terminal voltage and adapt to the power grid with relatively low short circuit.

[0067] In addition, some situations (for example, a commutation failure in UHV DC) will cause the power grid to continuously experience low and high voltage conditions. This requires the equipment in the system to have continuous low-high, low-low, high-high, and high-low voltage ride-through capabilities to support the power grid. However, the existing technology has the following problems, which can easily lead to continuous ride-through failures: (1) Before the fault ride-through, the unit has three reactive states: a) inductive reactive output, b) capacitive reactive output, and c) zero reactive output. During the high voltage ride-through period, the unit generates reactive power according to the amplitude of the voltage increase and the reactive power state before the high voltage ride-through. During the subsequent low voltage ride-through period, if the reactive current output target value during the low voltage ride-through period is based on the amplitude of the voltage reduction and the reactive power state before the low voltage ride-through, the reactive power output target value will be reduced. (1) The reactive current value before the low voltage crossing is a value during the transition from the high voltage crossing state to the low voltage crossing state. Therefore, the reactive current value used may not be the reactive current value actually required by the power grid. (2) After the high voltage crossing is completed, before entering the low voltage crossing, the recovery rate of reactive power does not take into account the recovery rate of active power. Under certain working conditions, it enters the secondary low voltage crossing state or the high voltage crossing state, and may even cause the failure of low voltage crossing caused by subsequent power grid failure. (3) The high voltage crossing cannot be exited in time. When the grid voltage is restored, if the high voltage crossing state is not exited in time, the unit is still in the inductive reactive state. If the inductive reactive power coincides with the low voltage, the grid voltage will be deteriorated. In view of the above problems existing in the prior art, the present disclosure proposes that when the fault crossing flag of the wind turbine generator set is set and it is in the voltage control mode, the reactive current output target value is determined based on the last determined machine-end voltage target value before the fault crossing flag is set, thereby avoiding the reactive output current target value not being the reactive current actually required by the power grid during continuous crossing. Moreover, the voltage control mode of the present disclosure can automatically balance the recovery rate of active power and reactive power by controlling the terminal voltage after the fault ride-through to ensure that the active recovery and reactive recovery after the fault ride-through match, thereby providing a guarantee for the success of continuous ride-through. In addition, by effectively setting the grid voltage range that triggers the reactive current control mode to switch from the fault ride-through mode to the voltage control mode, and determining the reactive current output target value based on the terminal voltage target value, the inductive reactive power during high ride-through and the capacitive reactive power during low ride-through can be recovered in time, thereby achieving timely exit from high voltage ride-through or low voltage ride-through, avoiding the subsequent failure of low voltage or high voltage ride-through.

[0068] Figure 4 A flow chart showing a control method of a wind farm according to an exemplary embodiment of the present disclosure is shown. As an example, the control method may be executed by a wind farm control device.

[0069] Reference Figure 4In step S201, when the fault ride-through flag of the wind farm is not set, a reactive power control command is generated and sent to the wind turbine generator set of the wind farm, so that the generator set responds to the reactive power control command and supports the reactive power demand of the grid connection point.

[0070] In step S202, when a voltage drop or voltage rise fault is detected in the power grid, a fault crossing flag is set and generation of reactive power control commands is stopped.

[0071] In one embodiment, in step S202, the generation and sending of reactive power control commands may be stopped.

[0072] In another embodiment, in step S202, the reactive control command may be stopped from being generated, but the reactive control command generated for each wind turbine generator set last time before the fault ride-through flag is set is sent, that is, the reactive control command is maintained at the command before the transient fault.

[0073] Here, the reactive control command includes a reactive control command for sending a given value of a machine-end voltage and a reactive power output target value. According to an exemplary embodiment of the present disclosure, when controlling the reactive power output of a unit, not only the reactive power output target value is sent to the unit, but also the machine-end voltage given value is sent to the unit, so that the unit can control the reactive current output based on the machine-end voltage, for example, to control the reactive current output with the goal of achieving a certain machine-end voltage target value.

[0074] As an example, a wind farm controller that executes the wind farm control method according to the exemplary embodiment of the present disclosure may operate in one of a power factor control mode, a voltage control mode (which should be understood to be different from the voltage control mode of the unit), and a reactive power control mode, and the present disclosure does not limit this.

[0075] As an example, the reactive power output target value of each wind turbine generator set can be determined based on the reactive power output target value of the wind farm, the reactive power measurement value of the wind farm, and the terminal voltage of each wind turbine generator set in the wind farm. It should be understood that the reactive power output target values ​​sent to different wind turbine generator sets may be the same or different; the terminal voltage set values ​​sent to different wind turbine generator sets may be the same or different. The same reactive control command can be used to send both the reactive power output target value and the terminal voltage set value to the unit. Different reactive control commands can also be used to send the reactive power output target value and the terminal voltage set value to the unit.

[0076] As an example, the wind farm control method according to the exemplary embodiment of the present disclosure may further include: setting a fault-through flag when receiving notifications from a first predetermined number of wind turbines that the wind turbines have set a fault-through flag.

[0077] As an example, the control method of a wind farm according to an exemplary embodiment of the present disclosure may further include: when the fault ride-through flag of the wind farm is set and the grid voltage is monitored to recover to a preset range, a notification is sent to the wind turbine generator set to allow the set to release the fault ride-through flag position.

[0078] As an example, the control method of the wind farm according to the exemplary embodiment of the present disclosure may further include: when the fault ride-through flag of the wind farm has been set, the grid voltage is monitored to be restored to a preset range, and a notification of allowing the wind farm to release the fault ride-through flag position is received from a second predetermined number of wind turbines, the fault ride-through flag position is released. As an example, the preset range may be: greater than or equal to 0.8 pu and less than or equal to 1.15 pu.

[0079] As an example, the reactive power control command may further include a reactive power control command for sending a low voltage ride-through reactive current K factor and / or a high voltage ride-through reactive current K factor.

[0080] In one embodiment, the control method of the wind farm according to the exemplary embodiment of the present disclosure may further include: when the fault ride-through flag of the wind farm is not set, the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor may be determined and sent based on the grid connection point system impedance, the impedance of the transformer and the line in the wind farm, and the capacity of the wind farm grid-connected units. That is, when the fault ride-through flag of the wind farm is set, the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor are no longer determined and sent.

[0081] As an example, the grid connection point system impedance and the magnitude of the low voltage crossing reactive current K coefficient and / or the high voltage crossing reactive current K coefficient may be inversely correlated. Specifically, the larger the grid connection point system impedance, the smaller the low voltage crossing reactive current K coefficient and / or the high voltage crossing reactive current K coefficient; the smaller the grid connection point system impedance, the larger the low voltage crossing reactive current K coefficient and / or the high voltage crossing reactive current K coefficient.

[0082] As an example, the grid connection point system impedance (i.e., grid impedance Zs) can be determined in the following manner: in the absence of grid faults, two sets of voltage vectors and current vectors are measured at the grid connection point. V1 and I1 are the first set of voltage vectors and current vectors, respectively, and V2 and I2 are the second set of voltage vectors and current vectors, respectively. Then, Zs = (V1-V2) / (I1-I2) is calculated.

[0083] It should be understood that when the fault ride-through flag of the wind farm is not set, the following can be periodically calculated and sent to the wind turbine generator set: terminal voltage set value, reactive power output target value, low voltage ride-through reactive current K coefficient and / or high voltage ride-through reactive current K coefficient.

[0084] Considering that in the voltage control mode of the unit, the possibility of island operation of the unit will increase. Therefore, the present disclosure also proposes that island detection can be effectively performed from the aspects of grid connection point, line and machine end, so as to reduce the blind spot of island detection in the single-machine voltage control mode. In one embodiment, the control method of the wind farm according to the exemplary embodiment of the present disclosure may also include: based on the off state of the grid connection point circuit breaker, the wind farm line circuit breaker, and the unit box transformer circuit breaker and the grid connection point system impedance, determine the wind turbine generator set in the island operation state; then, send a shutdown command to the wind turbine generator set in the island operation state.

[0085] The existing wind farm controller simply sets the thresholds of high and low ride-through, which cannot match the high and low ride-through of the unit. As a result, the unit may enter fault ride-through while the farm controller does not; or even the unit may not enter fault ride-through while the farm controller enters fault ride-through. The problem of the unit entering secondary fault ride-through may also occur due to improper control of the wind farm controller. According to the exemplary embodiment of the present disclosure, the connection between the reactive power command of the wind farm controller and the unit before and after the fault ride-through is guaranteed, so that the high and low ride-through coordination of the wind farm controller and the unit can be well achieved.

[0086] Figure 5 An example of a method for controlling a wind farm and a wind turbine generator system according to an exemplary embodiment of the present disclosure is shown.

[0087] The left side shows a flow chart of the control method of the wind farm, and the right side shows a flow chart of the control method of the wind turbine generator set. In stage A, the fault ride-through flag of the wind farm is not set, and the fault ride-through flag of the wind turbine generator set is not set, that is, the wind farm and the wind turbine generator set operate normally. In stage B, the fault ride-through flag of the wind turbine generator set is set and is in fault ride-through mode. In stage C, the fault ride-through flag of the wind turbine generator set is set and is in voltage control mode. In stage D, the fault ride-through flag is released.

[0088] Figure 6 A structural block diagram of a control device of a wind turbine generator set according to an exemplary embodiment of the present disclosure is shown.

[0089] like Figure 6 As shown, the control device of the wind turbine generator set according to the exemplary embodiment of the present disclosure includes: a flag setting unit 101 and a mode switching unit 102 .

[0090] Specifically, the flag setting unit 101 is used to set the fault ride-through flag of the wind turbine generator set if a voltage drop or voltage rise fault is detected in the power grid when the fault ride-through flag of the wind turbine generator set is not set.

[0091] The mode switching unit 102 is used to switch the reactive current control mode from the voltage control mode to the fault ride-through mode when the fault ride-through flag of the wind turbine generator set is set; wherein, when the fault ride-through flag of the wind turbine generator set is set and it is in the fault ride-through mode, if it is monitored that the grid voltage recovers to within a preset range, the mode switching unit 102 switches the reactive current control mode from the fault ride-through mode to the voltage control mode; wherein, when the fault ride-through flag of the wind turbine generator set is set and it is in the voltage control mode, if the machine-end voltage meets a preset condition, the flag setting unit 101 releases the ride-through flag position, wherein, in the voltage control mode, the reactive current output target value is determined based on the machine-end voltage target value, and the machine-end voltage target value is determined based on the reactive control command received from the wind farm controller.

[0092] As an example, when the fault ride-through flag of a wind turbine generator set is set and is in voltage control mode, the machine-end voltage target value may be maintained as the machine-end voltage target value determined last time before the fault ride-through flag is set; when the fault ride-through flag of a wind turbine generator set is not set and is in voltage control mode, the machine-end voltage target value may be determined based on the reactive power control command currently received from the wind farm controller.

[0093] As an example, when the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, if the grid is monitored to have a voltage drop or voltage rise fault again, the mode switching unit 102 may switch the reactive current control mode from the voltage control mode to the fault ride-through mode.

[0094] As an example, the control device may further include: a notification unit (not shown), which is used to notify the wind farm controller that the wind turbine has set the fault crossing flag when the fault crossing flag of the wind turbine is set.

[0095] As an example, if the terminal voltage meets a preset condition and a notification is received from the wind farm controller to allow the generator set to release the fault ride-through flag position, the flag setting unit 101 may release the ride-through flag position.

[0096] As an example, when the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, if the terminal voltage meets a preset condition, the notification unit may send a notification to the wind farm controller allowing the wind farm to release the fault ride-through flag.

[0097] As an example, the preset condition may include: the machine-end voltage reaches the machine-end voltage target value, or the machine-end voltage remains unchanged for a preset time period.

[0098] As an example, the control device may also include: a grid phase simulation unit (not shown) and a grid phase acquisition unit (not shown), the grid phase simulation unit being used to lock the grid phase when it is monitored that the grid voltage is lower than a first preset threshold, and to simulate and generate the real-time phase of the grid based on the locked grid phase changing over time; the grid phase acquisition unit being used to use the simulated real-time phase of the grid as the current grid phase when it is monitored that the grid voltage is lower than a second preset threshold, wherein the second preset threshold is smaller than the first preset threshold.

[0099] As an example, the control device may further include: an active power control unit (not shown), the active power control unit being configured to start restoring active power when switching from the fault ride-through mode to the voltage control mode.

[0100] As an example, the preset range may be: greater than or equal to 0.8 pu and less than or equal to 1.15 pu.

[0101] As an example, in the voltage control mode, the reactive current output target value can be determined in the following manner: based on the reactive power output target value in the reactive control command received from the wind farm controller and the machine-end voltage set value, the machine-end voltage target value is determined; based on the machine-end voltage target value and the reactive power measurement value of the wind turbine generator set, the reactive current output target value is determined.

[0102] As an example, based on the machine-end voltage target value and the reactive power measurement value of the wind turbine generator set, the process of determining the reactive current output target value may include: inputting the reactive power measurement value of the wind turbine generator set into a droop controller, and determining the reactive current output target value based on the difference between the machine-end voltage target value and the output of the droop controller.

[0103] As an example, in the voltage control mode, the reactive current output target value can be determined in the following manner: the difference between the reactive power output target value in the reactive control command received from the wind farm controller and the reactive power measurement value is input into the first PI regulator, wherein the first PI regulator is set with an output upper limit value and an output lower limit value; the sum of the output of the first PI regulator and the machine-end voltage set value in the reactive control command received from the wind farm controller is used as the machine-end voltage target value; the reactive power measurement value of the wind turbine is input into the droop controller; the difference between the machine-end voltage target value and the output of the droop controller is input into the second PI regulator after subtracting the machine-end voltage measurement value, and the output of the second PI regulator is used as the reactive current output target value component on the q-axis of the two-phase synchronous rotating coordinate system, wherein the second PI regulator is set with an output upper limit value and an output lower limit value.

[0104] As an example, in the fault ride-through mode, the reactive current output target value may be determined based on a low voltage ride-through reactive current K factor or a high voltage ride-through reactive current K factor received from the wind farm controller.

[0105] As an example, the control device may also include: a K-factor acquisition unit (not shown), which is used to receive and update the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor from the wind farm controller when the fault ride-through flag of the wind turbine generator set is not set.

[0106] As an example, the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor can be determined by the wind farm controller based on at least one of the following items: the grid connection point system impedance, the impedance of the transformer and lines in the wind farm, and the capacity of the wind farm grid-connected units, wherein the grid connection point system impedance may be inversely correlated with the magnitude of the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor.

[0107] Figure 7 A structural block diagram of a wind farm control device according to an exemplary embodiment of the present disclosure is shown.

[0108] like Figure 7 As shown, the control device of a wind farm according to an exemplary embodiment of the present disclosure includes: a reactive power control command generating unit 201 , a reactive power control command sending unit 202 , and a flag setting unit 203 .

[0109] Specifically, the reactive power control command generating unit 201 is used to generate and send a reactive power control command to the wind turbine generator set of the wind farm when the fault ride-through flag of the wind farm is not set.

[0110] The reactive power control command sending unit 202 is used to send reactive power control commands to the wind turbine generator sets in the wind farm.

[0111] The flag setting unit 203 is used to set the fault crossing flag when a voltage drop or voltage rise fault is detected in the power grid, wherein the reactive control command generating unit 201 stops generating reactive control commands when the fault crossing flag of the wind farm is set, wherein the reactive control commands include reactive control commands for transmitting a set value of voltage at the transmitter end and a target value of reactive power output.

[0112] As an example, the flag setting unit 203 may set the fault crossing flag to a position when receiving notifications from a first predetermined number of wind turbine generator sets that the wind turbine generator sets have set the fault crossing flag to a position.

[0113] As an example, the control device may also include: a notification unit (not shown), which is used to send a notification to the wind turbine generator set to allow the set to clear the fault ride-through flag position when the fault ride-through flag of the wind farm has been set and the grid voltage is monitored to recover to a preset range.

[0114] As an example, the flag setting unit 203 may release the fault ride-through flag when the fault ride-through flag of the wind farm has been set, the grid voltage is monitored to recover to a preset range, and a notification is received from a second predetermined number of wind turbines allowing the wind farm to release the fault ride-through flag.

[0115] As an example, the reactive power control command may further include a reactive power control command for sending a low voltage ride-through reactive current K factor and / or a high voltage ride-through reactive current K factor.

[0116] As an example, the control device may also include: a K-factor determination unit (not shown), which is used to determine and send a low voltage ride-through reactive current K factor and / or a high voltage ride-through reactive current K factor based on the grid connection point system impedance, the impedance of the transformer and lines in the wind farm, and the capacity of the wind farm grid-connected units when the fault ride-through flag of the wind farm is not set.

[0117] As an example, the grid connection point system impedance may be inversely correlated with the magnitude of the low voltage ride through reactive current K factor and / or the high voltage ride through reactive current K factor.

[0118] As an example, the control device may also include: an island detection unit (not shown), the island detection unit is used to determine the wind turbine generator set in the island operation state based on the shutdown status of the grid point circuit breaker, the wind farm line circuit breaker, and the unit box transformer circuit breaker and the grid point system impedance; and send a shutdown command to the wind turbine generator set in the island operation state.

[0119] It should be understood that the specific processing performed by the control device of the wind turbine generator set according to the exemplary embodiment of the present disclosure has been referred to. Figure 1-5 The details have been described in detail and will not be repeated here.

[0120] It should be understood that the specific processing performed by the control device of the wind farm according to the exemplary embodiment of the present disclosure has been referred to. Figure 1-5 The details have been described in detail and will not be repeated here.

[0121] It should be understood that the various units in the control device of the wind turbine generator set and the control device of the wind farm according to the exemplary embodiment of the present disclosure can be implemented as hardware components and / or software components. Those skilled in the art can implement the various units, for example, using a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC) according to the processing performed by the defined various units.

[0122] An exemplary embodiment of the present disclosure provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the control method of a wind turbine generator set as described in the above exemplary embodiment. The computer-readable storage medium is any data storage device that can store data read out by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, read-only optical disk, magnetic tape, floppy disk, optical data storage device, and carrier wave (such as data transmission through the Internet via a wired or wireless transmission path).

[0123] An exemplary embodiment of the present disclosure provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements a control method for a wind farm as described in the exemplary embodiment above. The computer-readable storage medium is any data storage device that can store data read out by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, read-only optical disk, magnetic tape, floppy disk, optical data storage device, and carrier wave (such as data transmission through the Internet via a wired or wireless transmission path).

[0124] According to an exemplary embodiment of the present disclosure, a control device of a wind turbine generator set includes: a processor (not shown) and a memory (not shown), wherein the memory stores a computer program, and when the computer program is executed by the processor, the control method of the wind turbine generator set as described in the exemplary embodiment above is implemented. As an example, the control device may be a controller of the wind turbine generator set.

[0125] According to an exemplary embodiment of the present disclosure, a control device for a wind farm includes: a processor (not shown) and a memory (not shown), wherein the memory stores a computer program, and when the computer program is executed by the processor, the control method for the wind farm described in the exemplary embodiment is implemented. As an example, the control device may be a controller of a wind farm.

[0126] Although some exemplary embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that modifications may be made to these embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A control method for a wind turbine generator set, characterized in that: The control method comprises: When the fault ride-through flag of the wind turbine generator set is not set, if a voltage drop or voltage rise fault is detected in the power grid, the fault ride-through flag of the wind turbine generator set is set, and the reactive current control mode is switched from the voltage control mode to the fault ride-through mode; When the fault ride-through flag of the wind turbine generator set is set and it is in the fault ride-through mode, if it is monitored that the grid voltage recovers to within the preset range, the reactive current control mode is switched from the fault ride-through mode to the voltage control mode; When the fault ride-through flag of the wind turbine generator set is set and it is in voltage control mode, if the terminal voltage meets the preset conditions, the ride-through flag is cleared. Wherein, in the voltage control mode, the reactive current output target value is determined based on the machine-end voltage target value, and the machine-end voltage target value is determined based on the reactive power control command received from the wind farm controller.

2. The control method according to claim 1, characterized in that: When the fault ride-through flag of the wind turbine generator set is set and the wind turbine generator set is in voltage control mode, the target voltage value at the generator end is maintained as the target voltage value at the generator end determined last time before the fault ride-through flag is set; When the fault ride-through flag of the wind turbine generator set is not set and the wind turbine generator set is in voltage control mode, the target value of the terminal voltage is determined based on the reactive power control command currently received from the wind farm controller.

3. The control method according to claim 1, characterized in that: The control method further comprises: When the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, if it is detected that the grid has a voltage drop or voltage rise fault again, the reactive current control mode is switched from the voltage control mode to the fault ride-through mode.

4. The control method according to claim 1, characterized in that: The steps to clear the crossing flag bit include: If the terminal voltage meets the preset conditions and the wind farm controller sends a notification that allows the unit to release the fault ride-through flag position, the ride-through flag position is released. The control method further includes: when the fault ride-through flag of the wind turbine generator set is set and in voltage control mode, if the terminal voltage meets a preset condition, sending a notification to the wind farm controller allowing the wind farm to release the fault ride-through flag.

5. The control method according to claim 1 or 4, characterized in that: The preset conditions include: the machine-end voltage reaches the machine-end voltage target value, or the machine-end voltage remains unchanged for a preset time period; and / or, The control method further comprises: when the fault-through flag of the wind turbine generator set is set to a position, notifying the wind farm controller that the fault-through flag has been set to a position.

6. The control method according to claim 1, characterized in that: The control method further comprises: When it is monitored that the grid voltage is lower than a first preset threshold, the grid phase is locked, and a real-time grid phase is generated based on the locked grid phase changing over time by simulation; When the grid voltage is detected to be lower than the second preset threshold, the real-time phase of the simulated grid is used as the current grid phase. The second preset threshold is smaller than the first preset threshold.

7. The control method according to claim 1, characterized in that: In voltage control mode, the reactive current output target value is determined by: Determine a target value of the generator terminal voltage based on a reactive power output target value and a given value of the generator terminal voltage in a reactive power control command received from a wind farm controller; The reactive current output target value is determined based on the terminal voltage target value and the reactive power measurement value of the wind turbine generator set.

8. The control method according to claim 7, characterized in that: The steps of determining the reactive current output target value based on the terminal voltage target value and the reactive power measurement value of the wind turbine generator set include: The reactive power measurement value of the wind turbine generator set is input into the droop controller, and the reactive current output target value is determined based on the difference between the machine terminal voltage target value and the output of the droop controller.

9. The control method according to claim 8, characterized in that: In voltage control mode, the reactive current output target value is determined by: Inputting a difference between a reactive power output target value and a reactive power measurement value in a reactive power control command received from a wind farm controller into a first PI regulator, wherein the first PI regulator is set with an output upper limit value and an output lower limit value; The sum of the output of the first PI regulator and the set value of the terminal voltage in the reactive power control command received from the wind farm controller is used as the target value of the terminal voltage; inputting the reactive power measurement of the wind turbine to the droop controller; The difference between the target value of the machine-end voltage and the output of the droop controller, minus the measured value of the machine-end voltage, is input into the second PI regulator, and the output of the second PI regulator is used as the reactive current output target value component on the q-axis of the two-phase synchronous rotating coordinate system, wherein the second PI regulator is set with an output upper limit value and an output lower limit value.

10. The control method according to claim 1, characterized in that: In the fault ride-through mode, the reactive current output target value is determined based on the low voltage ride-through reactive current K factor or high voltage ride-through reactive current K factor received from the wind farm controller. Wherein, the control method further includes: When the fault ride-through flag of the wind turbine generator set is not set, the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor are received and updated from the wind farm controller. The low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor are determined by the wind farm controller based on at least one of the following items: the grid connection point system impedance, the impedance of the transformer and the line in the wind farm, and the capacity of the wind farm grid-connected unit. The grid connection point system impedance is inversely correlated with the magnitude of the low voltage ride through reactive current K factor and / or the high voltage ride through reactive current K factor.

11. A method for controlling a wind farm, characterized in that: The control method comprises: When the fault ride-through flag of the wind farm is not set, a reactive power control command is generated and sent to the wind turbine generator set of the wind farm; When a voltage drop or voltage rise fault is detected in the power grid, the fault crossing flag is set and the generation of reactive power control commands is stopped. The reactive power control command includes a reactive power control command for sending a set value of voltage at the transmitter end and a reactive power output target value, and a reactive power control command for sending a low voltage ride-through reactive current K coefficient and / or a high voltage ride-through reactive current K coefficient; Among them, when the wind turbine generator set is in the fault ride-through mode, the reactive current output target value is determined based on the received low voltage ride-through reactive current K coefficient or high voltage ride-through reactive current K coefficient.

12. The control method according to claim 11, characterized in that: The control method further comprises: When receiving notifications from the first predetermined number of wind turbine generator sets that the wind turbine generator sets have set the fault-through flag, the fault-through flag is set.

13. The control method according to claim 11, characterized in that: The control method further comprises: When the fault ride-through flag of the wind farm has been set and the grid voltage is detected to be restored to a preset range, a notification is sent to the wind turbine generator set to allow the generator set to release the fault ride-through flag position; When the fault ride-through flag of the wind farm is set, the grid voltage is monitored to be restored to a preset range, and a notification is received from a second predetermined number of wind turbines allowing the wind farm to release the fault ride-through flag, the fault ride-through flag is released.

14. The control method according to claim 11, characterized in that: The control method further comprises: When the fault ride-through flag of the wind farm is not set, the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor are determined and sent based on the grid connection point system impedance, the impedance of the transformer and the line in the wind farm, and the capacity of the wind farm grid-connected units, wherein the grid connection point system impedance is inversely correlated with the magnitude of the low voltage ride-through reactive current K factor and / or the high voltage ride-through reactive current K factor.

15. The control method according to claim 11, characterized in that: The control method further comprises: Based on the off states of the grid connection point circuit breaker, the wind farm line circuit breaker, and the unit box transformer circuit breaker and the grid connection point system impedance, the wind turbine generator set in the island operation state is determined; Send a shutdown command to the wind turbine in island operation.

16. A control device for a wind turbine generator set, characterized in that: The control device comprises: A flag setting unit, when the fault crossing flag of the wind turbine generator set is not set, if a voltage drop or voltage rise fault is detected in the power grid, the fault crossing flag of the wind turbine generator set is set; A mode switching unit, when a fault ride-through flag of the wind turbine generator set is set, switches the reactive current control mode from a voltage control mode to a fault ride-through mode; Wherein, when the fault ride-through flag of the wind turbine generator set is set and the wind turbine generator set is in the fault ride-through mode, if the grid voltage is detected to be restored to a preset range, the reactive current control mode is switched from the fault ride-through mode to the voltage control mode; Wherein, when the fault ride-through flag of the wind turbine generator set is set and in the voltage control mode, if the terminal voltage meets the preset conditions, the flag setting unit releases the ride-through flag position. Wherein, in the voltage control mode, the reactive current output target value is determined based on the machine-end voltage target value, and the machine-end voltage target value is determined based on the reactive power control command received from the wind farm controller.

17. A control device for a wind farm, characterized in that: The control device comprises: A reactive power control command generating unit, when the fault crossing flag of the wind farm is not set, generates and sends a reactive power control command to the wind turbine generator set of the wind farm; A reactive power control command sending unit sends a reactive power control command to a wind turbine generator set in a wind farm; The flag setting unit sets the fault crossing flag when a voltage drop or voltage rise fault is detected in the power grid. The reactive power control command generating unit stops generating reactive power control commands when the fault crossing flag of the wind farm is set. The reactive power control command includes a reactive power control command for sending a set value of voltage at the transmitter end and a reactive power output target value, and a reactive power control command for sending a low voltage ride-through reactive current K coefficient and / or a high voltage ride-through reactive current K coefficient; Among them, when the wind turbine generator set is in the fault ride-through mode, the reactive current output target value is determined based on the received low voltage ride-through reactive current K coefficient or high voltage ride-through reactive current K coefficient.

18. A control device for a wind turbine generator set, characterized in that: The control device comprises: processor; A memory storing a computer program, which, when executed by a processor, implements the control method of a wind turbine generator set according to any one of claims 1 to 10.

19. A control device for a wind farm, characterized in that: The control device comprises: processor; The memory stores a computer program, and when the computer program is executed by the processor, the wind farm control method according to any one of claims 11 to 15 is implemented.

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