Wind turbine generator torque control method and system based on doubly-fed wind power converter

Abstract

The invention discloses a wind turbine generator torque control method and system based on a doubly-fed wind power converter. The doubly-fed wind power converter comprises a machine-side converter and a grid-side converter. The wind turbine generator torque control method comprises the steps of collecting operation data of a wind turbine generator grid-connected point and detecting a power grid operation state; when the operation state of the power grid is power failure, controlling the doubly-fed wind power converter to be switched to an off-grid mode for operation; establishing a temporary grid-connected point voltage in a grid construction mode through a machine-side converter, and outputting a torque support power required after power failure according to the torque value of the wind turbine generator set before power failure; and performing closed-loop tracking processing on the torque support power through a grid-side converter, and absorbing the torque support power to a DC bus for load balancing processing. When the power grid is powered off, a certain torque value can still be output, the situation that the wind turbine generator set is immediately shut down due to load shedding caused by the power grid is effectively prevented, and the load impact of the power grid to the wind turbine generator set is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine control, and in particular to a wind turbine torque control method and system based on a double-fed wind power converter. Background Art

[0002] When a wind turbine is generating electricity normally, if the substation circuit breaker trips, the grid may lose power. This will cause the wind turbine to lose load instantly, and its speed will increase sharply. In the face of such an emergency, the controller will take emergency shutdown measures to ensure the safety of the equipment. However, in this process, the mechanical parts of the unit will be subjected to greater pressure, especially the gearbox, which will bear a greater load during emergency shutdown, which poses a potential threat to the long-term stable operation of the wind turbine. It can be seen that the impact caused by power outages in the grid is mainly the load impact caused by the wind turbine load shedding.

[0003] In the prior art, the solutions for power outage in the power grid mainly include the following three categories:

[0004] Category 1: When the power grid loses power, the converter will adjust the stator voltage and current of the motor to ensure that the generator can provide the necessary torque support, thereby alleviating the load impact of the wind turbine during emergency shutdown. However, the converter of this solution often works in the grid-following mode and loses the grid angle at the moment of power failure. Therefore, in the process of identifying the power failure of the grid, the converter may have lost control, resulting in overcurrent in the converter.

[0005] The second type: When the power grid is down, when the power supply of the power grid is interrupted, the system will automatically switch to the energy-consuming device, which absorbs the rotational kinetic energy of the impeller, thereby effectively slowing down the sharp increase in the speed. At the same time, the backup power supply will be activated to provide the necessary power for the wind turbine and start the normal shutdown procedure. However, this solution requires additional investment costs for adding energy-consuming devices, resulting in a higher overall cost for the normal shutdown of the wind turbine.

[0006] Category 3: When the power grid loses power, the emergency shutdown procedure is immediately initiated, and the independent power supply device adjusts the wind turbine's pitch system to reduce the load on the unit and avoid overspeeding of the impeller. However, this solution mainly controls the pitch system without the involvement of the converter control, so its ability to reduce the load of the wind turbine is limited. In the case of heavy load, this solution may not be able to effectively reduce the impact on the unit. Summary of the invention

[0007] The purpose of the present invention is to provide a wind turbine torque control method and system based on a doubly-fed wind power converter, aiming to better solve the problem of load shock caused by wind turbine load shedding due to power outage of the power grid.

[0008] In a first aspect, an embodiment of the present invention provides a method for controlling the torque of a wind turbine generator set based on a doubly-fed wind power converter, wherein the doubly-fed wind power converter includes a machine-side converter and a grid-side converter; the method for controlling the torque of a wind turbine generator set includes:

[0009] Collect the operation data of wind turbine grid connection points and detect the operation status of the power grid;

[0010] When the operating state of the power grid is power failure, controlling the double-fed wind power converter to switch to off-grid mode operation;

[0011] A temporary grid connection point voltage is established in the grid construction mode by the machine-side converter, and the torque support power required after power failure is output according to the torque value of the wind turbine set before power failure;

[0012] The torque support power is tracked in a closed loop by the grid-side converter, and the torque support power is absorbed into the DC bus for load balancing.

[0013] In a second aspect, an embodiment of the present invention provides a wind turbine torque control system based on a doubly-fed wind power converter, which is applied to the wind turbine torque control method based on the doubly-fed wind power converter as described above, comprising:

[0014] A power failure detection unit is used to collect the operating data of the wind turbine grid connection point and detect the grid operation status;

[0015] An off-grid operation unit, used for controlling the double-fed wind power converter to switch to an off-grid mode when the grid is in a power-off state;

[0016] A voltage establishing unit, used for establishing a temporary grid connection point voltage in a grid-building mode through the machine-side converter;

[0017] A power output unit, used to output the torque support power required after power failure according to the torque value of the wind turbine set before power failure;

[0018] A power absorption unit is used to absorb the torque support power through the grid-side converter to achieve load balancing.

[0019] The beneficial effects of the embodiments of the present invention are:

[0020] The embodiment of the present invention controls the machine-side converter to operate in the grid-building mode and the grid-side converter to operate in the grid-following mode. When the grid loses power, the machine-side converter can actively establish a temporary grid-connected point voltage without detecting whether the grid loses power, and calculate the torque support power required by the wind turbine after the power failure, and the grid-side converter absorbs the corresponding torque support power to achieve load balance. It ensures that a certain torque support can still be output when the grid loses power, effectively preventing the wind turbine from immediately shutting down due to power failure, and significantly reducing the load impact of power failure on the wind turbine.

[0021] The grid-side converter of the embodiment of the present invention absorbs the torque support power to the chopper connected to the DC bus for discharge to achieve load balancing. This method does not require additional energy-consuming devices, reducing the overall cost of torque support of the wind turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A schematic flow chart of a method for controlling wind turbine torque in a doubly-fed wind power converter according to an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of a sub-process of step S101 provided in an embodiment of the present invention.

[0025] Figure 3 A schematic diagram of a sub-flow chart of step S103 provided in an embodiment of the present invention.

[0026] Figure 4 Another sub-flow diagram of step S103 provided in an embodiment of the present invention.

[0027] Figure 5 A schematic block diagram of a wind turbine torque control system of a doubly-fed wind power converter provided in an embodiment of the present invention.

[0028] Figure 6 A schematic diagram of energy flow after a power outage in a power grid during supersynchronous operation provided by an embodiment of the present invention.

[0029] Figure 7 A schematic diagram of energy flow after a power outage in a subsynchronous operation provided by an embodiment of the present invention.

[0030] Figure 8 A control block diagram of a doubly-fed machine-side converter in a grid-forming mode provided in an embodiment of the present invention.

[0031] Fig. 9 A schematic diagram of a calculation curve of torque support power / torque support current provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0033] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0034] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0035] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0036] See also Figure 1 , Figure 1 A schematic flow chart of a method for controlling torque of a wind turbine generator set based on a doubly-fed wind power converter according to an embodiment of the present invention.

[0037] The doubly-fed wind power converter of the present invention comprises a machine-side converter and a grid-side converter; the wind turbine torque control method comprises steps S101-S104.

[0038] S101, collecting the operation data of the wind turbine grid connection point and detecting the grid operation status;

[0039] In this step, the wind turbine grid connection point refers to a specific node in the power grid system that connects a single or multiple power generation devices. The voltage level of the wind turbine grid connection point needs to meet the requirements to ensure the stable operation of the power grid.

[0040] S102, when the operating state of the power grid is power failure, controlling the double-fed wind power converter to switch to off-grid mode operation;

[0041] In this step, when the grid loses power, the doubly-fed wind power converter switches from the grid-following mode to the off-grid mode. In the off-grid mode, the doubly-fed wind power converter will adjust its output frequency and voltage according to the preset control logic to meet the needs of independent operation.

[0042] S103, establishing a temporary grid connection point voltage in the grid construction mode through the machine-side converter, and outputting the torque support power required after the power failure according to the torque value of the wind turbine set before the power failure;

[0043] In this step, the machine-side converter can establish a temporary grid-connected point voltage in the grid-building mode without detecting power failure of the grid, and maintain the stable operation of the wind turbine through the temporary grid-connected point voltage. The torque support power required after power failure is output according to the torque value of the wind turbine before power failure. The output torque support power is used to ensure that the wind turbine can continue to provide torque when the grid connection is lost, so as to avoid the wind turbine from being immediately shut down due to power failure.

[0044] S104, performing closed-loop tracking processing on the torque support power through the grid-side converter, and absorbing the torque support power to the DC bus for load balancing processing.

[0045] In this step, the torque support power is effectively absorbed and integrated into the DC bus through the grid-side converter, thereby achieving load balancing for the entire system.

[0046] Based on the process of steps S101-S104, combined with Fig. 9 The torque support power / torque support current calculation curve diagram is shown. The present invention controls the machine-side converter to operate in the grid-building mode, and the grid-side converter to operate in the grid-following mode. When the grid loses power, it can actively establish a temporary grid-connected point voltage. After detecting the off-grid mark, it calculates the torque support power required by the wind turbine after the power failure, and the grid-side converter absorbs the corresponding torque support power to achieve load balance. It ensures that a certain torque support can still be output when the grid loses power, effectively preventing the wind turbine from being immediately shut down due to power failure, and significantly reducing the load impact of the grid failure on the wind turbine.

[0047] Furthermore, after step S104, the torque support power input by the grid-side converter is received through the DC bus, which will raise the voltage of the DC bus until the voltage of the DC bus reaches a preset threshold value and then the chopper is put into use for power discharge to achieve load balancing. This method does not require additional energy-consuming devices, reducing the overall cost of torque support for wind turbines. For details, please refer to Figure 6 and Figure 7 When a power outage occurs in the super-synchronous or sub-synchronous operation state, the torque support power absorbed by the DC bus will cause the voltage of the DC bus to reach the preset threshold value, and the chopper will be put into use for power discharge to achieve load balance.

[0048] See also Figure 2 In one embodiment, step S101 includes:

[0049] S201, obtaining the voltage value, current value, power value and frequency value of the wind turbine generator set;

[0050] S202: When at least one parameter value among the voltage value, the current value, the power value and the frequency value deviates from its preset value, it is determined that the operation state of the power grid is power failure.

[0051] In step S201, the current value and voltage value of the original grid-connected point can be accurately obtained according to the sampling data of the current transformer and the voltage transformer. Based on the current value and voltage value of the grid-connected point, the corresponding power value is calculated. The frequency value of the original grid-connected point voltage can be calculated by the angular frequency output by the phase-locked loop, the frequency adjustment amount generated by the phase-locked loop regulator, or the component of the phase-locked loop input voltage signal. Thus, the voltage value, current value, power value and frequency value of the original grid-connected point are obtained.

[0052] In step S202, it is determined whether the power grid is powered off, including at least one of the following situations:

[0053] Case 1: The current value decreases instantaneously, but the effective current value is still greater than the corresponding preset value;

[0054] Case 2: The deviation between the power feedback value and the power set value reaches the corresponding preset value;

[0055] Case 3: The frequency value exceeds the preset normal range and / or the change rate of the frequency value reaches the preset change rate.

[0056] By combining the above three situations for detection and determination, it is possible to accurately know whether the power grid has lost power. Specifically, to improve the accuracy of the power grid determination, it can be determined that the power grid has lost power when two of the above three situations are met.

[0057] See also Figure 3 In one embodiment, the step of establishing a temporary grid connection point voltage by the machine-side converter in the grid-building mode in step S103 includes:

[0058] S301, controlling the machine-side converter to operate in a grid-building mode;

[0059] S302: Control the generator-side converter by means of primary frequency modulation and reactive power droop to establish a temporary grid-connected point voltage.

[0060] In step S301, the grid-forming mode means that the machine-side converter shows voltage source characteristics to the outside and can independently form and support the stable operation of the grid without an external grid.

[0061] Specific, combined Figure 8 The control block diagram of the doubly-fed machine-side converter in the grid-building mode is shown in FIG. The operating model formula of the machine-side converter in the grid-building mode is:

[0062]

[0063] Where J is the virtual moment of inertia of network control, ω is the actual angular velocity output by network control, and ω n is the rated angular velocity, P e is the input power of network control, P fb is the feedback power of network control, and D is the damping coefficient.

[0064] Among them, the input power P e It consists of active power command and primary frequency modulation control power adjustment, namely: P e =P ref +K ω (ω n -ω fb ), where P ref is the active power, K ω is the active power droop coefficient, ω fb Real-time feedback of angular frequency.

[0065] In step S302, primary frequency regulation refers to adjusting the output power of the machine-side converter to ensure the stability of the grid connection point frequency. Reactive power droop refers to adjusting the output of reactive power to ensure the stability of the grid connection point voltage and to establish a temporary grid connection point voltage when the grid loses power.

[0066] Specifically, the temporary grid connection point voltage is established according to the following formula:

[0067]

[0068] Among them, E s_ref is the virtual electromotive force, K qp , K qi are the proportional coefficient and integral coefficient of the reactive power loop, U ref For a given temporary grid-connected point voltage, Q ref For a given reactive power, Q fb is the reactive power feedback, D q Based on this, by substituting each parameter into the above formula for calculation, the grid connection point voltage can be output.

[0069] See also Figure 4 In one embodiment, the step of outputting the torque support power required after power failure according to the torque value of the wind turbine generator set before power failure in step S103 includes:

[0070] S401, obtaining a torque value of the wind turbine generator set before power failure based on a power latch value latched before power failure of the power grid;

[0071] S402, calculating the torque support power required after power failure based on the torque value of the wind turbine generator set;

[0072] S403. Output the required torque support power through the machine-side converter.

[0073] In this embodiment, the power latch value latched by the power grid before the power outage occurs is used to accurately calculate the torque value generated by the wind turbine just before the power outage. Then, based on the calculated torque value of the wind turbine, the torque support power required to maintain system stability after the power outage is further calculated. Finally, the torque support power is output through the machine-side converter to ensure that torque support is provided for the wind turbine in the event of a power outage.

[0074] In a specific embodiment, the torque support power P required in step S402 is calculated according to the following formula: ref :

[0075]

[0076] Among them, P ref Indicates the torque support power, P Lock represents the power lock value before the power grid is powered off, K represents the torque support coefficient, t 1 Indicates the torque support power maintenance time, t max Indicates the maximum time of torque support. Based on this, the torque support power P can be output by substituting each parameter into the above formula for calculation. ref .

[0077] In one embodiment, there are two embodiments for absorbing torque support power by the grid-side converter in step S104.

[0078] Embodiment 1: The torque support power is tracked in a closed-loop mode by the grid-side converter, and the torque support power is absorbed into the DC bus for load balancing.

[0079] In this embodiment, in the power closed-loop mode, the grid-side converter can monitor and adjust the torque support power in real time to ensure closed-loop tracking of the torque support power. Torque support power refers to the power adjustment performed in the wind power system to maintain the stability of the generator speed or to meet the needs of load changes. The grid-side converter absorbs these adjusted torque support powers into the DC bus, which, as an energy transfer station in the wind power system, can perform load balancing.

[0080] Embodiment 2: The torque support current corresponding to the torque support power is tracked in a closed-loop current mode by the grid-side converter to absorb the torque support power and flow it to the DC bus for load balancing.

[0081] In this embodiment, in the current closed-loop mode, the grid-side converter can absorb active power through the current loop. Specifically, the torque support current I can be calculated according to the following formula: ref :

[0082]

[0083] Among them, I ref Indicates the torque support current, P Lock Indicates the power lock value before the power grid is powered off, K indicates the torque support coefficient, V m Indicates the modulus of the grid-connected point voltage, t 1 Indicates the torque support power maintenance time, t max Indicates the maximum time of torque support. Based on this, the torque support current I can be output by substituting each parameter into the above formula for calculation. ref .

[0084] The grid-side converter calculates the torque support current I ref , in the current closed-loop mode, the torque support power is tracked in a closed-loop manner and the corresponding power is absorbed to perform load balancing processing.

[0085] See also Figure 5 The embodiment of the present invention further provides a wind turbine torque control system based on a double-fed wind power converter, comprising:

[0086] A power failure detection unit 501 is used to collect the operation data of the wind turbine grid connection point and detect the operation status of the grid;

[0087] The off-grid operation unit 502 is used to control the double-fed wind power converter to switch to the off-grid mode when the operation state of the power grid is power failure;

[0088] A voltage establishing unit 503, used to establish a temporary grid connection point voltage in a grid-forming mode through a machine-side converter;

[0089] The power output unit 504 is used to output the torque support power required after power failure according to the torque value of the wind turbine set before power failure;

[0090] The power absorption unit 505 is used to absorb the torque support power through the grid-side converter to achieve load balancing.

[0091] The power discharge unit 506 is used to receive the torque support power input by the grid-side converter through the DC bus to raise the voltage of the DC bus until the voltage of the DC bus reaches a preset threshold value and then input the chopper for power discharge to achieve load balance.

[0092] This system controls the machine-side converter to operate in the grid-building mode and the grid-side converter to operate in the grid-following mode. When the grid loses power, the machine-side converter can actively establish a temporary grid-connected point voltage without detecting whether the grid loses power, and calculate the torque support power required by the wind turbine after the power failure, and the grid-side converter absorbs the corresponding torque support power to achieve load balance. It ensures that a certain torque support can still be output when the grid loses power, effectively preventing the wind turbine from immediately shutting down due to power failure, and significantly reducing the load impact of power failure on the wind turbine.

[0093] The grid-side converter absorbs the torque support power and discharges it to the chopper connected to the DC bus to achieve load balancing. This method does not require additional energy-consuming devices, reducing the overall cost of wind turbine torque support.

[0094] The wind turbine torque control system based on the doubly-fed wind power converter provided in the embodiment of the present invention belongs to the same inventive concept as the wind turbine torque control method based on the doubly-fed wind power converter provided in the above embodiment of the present invention, and can execute the wind turbine torque control method based on the doubly-fed wind power converter provided in any of the above embodiments of the present invention, and has the corresponding functional modules and beneficial effects of executing the wind turbine torque control method based on the doubly-fed wind power converter. For technical details not fully described in this embodiment, please refer to the specific processing content of the wind turbine torque control method based on the doubly-fed wind power converter provided in the above embodiment of the present invention, which will not be repeated here.

[0095] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0096] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for controlling torque of a wind turbine generator set based on a doubly-fed wind power converter, wherein the doubly-fed wind power converter comprises a machine-side converter and a grid-side converter; characterized in that: The wind turbine torque control method comprises: Collect the operation data of wind turbine grid connection points and detect the operation status of the power grid; When the operating state of the power grid is power failure, controlling the double-fed wind power converter to switch to off-grid mode operation; A temporary grid connection point voltage is established in the grid construction mode by the machine-side converter, and the torque support power required after power failure is output according to the torque value of the wind turbine set before power failure; The torque support power is tracked in a closed loop by the grid-side converter, and the torque support power is absorbed into the DC bus for load balancing.

2. The wind turbine torque control method based on a doubly-fed wind power converter according to claim 1, characterized in that: The step of collecting the operation data of the wind turbine grid connection point and detecting the operation status of the power grid includes: Obtaining the voltage value, current value, power value and frequency value of the wind turbine generator grid connection point; When at least one parameter value among the voltage value, current value, power value and frequency value deviates from its preset value, it is determined that the operating state of the power grid is power failure.

3. The wind turbine torque control method based on a doubly-fed wind power converter according to claim 1, characterized in that: The step of establishing a temporary grid connection point voltage in a grid-building mode by the machine-side converter includes: Controlling the machine-side converter to operate in a grid-building mode; The generator-side converter is controlled by primary frequency modulation and reactive power droop to establish a temporary grid-connected point voltage.

4. The wind turbine torque control method based on a doubly-fed wind power converter according to claim 3 is characterized in that: The step of controlling the generator-side converter by means of primary frequency modulation and reactive power droop to establish a temporary grid-connected point voltage includes: The temporary grid connection point voltage is established according to the following formula: Among them, E s_ref is the virtual electromotive force, K qp , K qi are the proportional coefficient and integral coefficient of the reactive power loop, U ref For a given temporary grid-connected point voltage, Q ref For a given reactive power, Q fb is the reactive power feedback, D q is the reactive power droop coefficient.

5. The wind turbine torque control method based on a doubly-fed wind power converter according to claim 1, characterized in that: The step of outputting the torque support power required after power failure according to the torque value of the wind turbine set before power failure comprises: Based on the power latch value latched before the power outage of the power grid, the torque value of the wind turbine set before the power outage is obtained; Based on the torque value of the wind turbine generator set, calculating the torque support power required after power failure; The required torque support power is outputted through the machine-side converter.

6. The wind turbine torque control method based on a doubly-fed wind power converter according to claim 5, characterized in that: The step of calculating the torque support power required after power failure based on the torque value of the wind turbine generator set comprises: Calculate the torque support power P according to the following formula ref : Among them, P ref Indicates the torque support power, P Lock represents the power lock value before the power failure of the power grid, K represents the torque support coefficient, t1 represents the torque support power maintenance time, t max Indicates the maximum time of torque support.

7. The wind turbine torque control method based on a doubly-fed wind power converter according to claim 1, characterized in that: The step of performing closed-loop tracking processing on the torque support power by the grid-side converter and absorbing the torque support power to the DC bus for load balancing processing includes: Performing closed-loop tracking of the torque support power by the grid-side converter in a power closed-loop mode, and absorbing the torque support power to the DC bus for load balancing; or, The grid-side converter performs closed-loop tracking on the torque support current corresponding to the torque support power in the current closed-loop mode, so as to absorb the torque support power and flow it to the DC bus for load balancing.

8. The method for controlling the torque of a wind turbine generator system based on a double-fed wind power converter according to claim 7, characterized in that: The step of performing closed-loop tracking of the torque support current corresponding to the torque support power by the grid-side converter in a current closed-loop mode to achieve absorption of the torque support power includes: Calculate the torque support current I according to the following formula ref : Among them, I ref Indicates the torque support current, P Lock Indicates the power lock value before the power failure, K indicates the torque support coefficient, V m represents the modulus of the grid-connected point voltage, t1 represents the torque support power maintenance time, t max Indicates the maximum time of torque support.

9. The method for controlling the torque of a wind turbine generator system based on a doubly-fed wind power converter according to claim 1, characterized in that: Also includes: The torque support power input by the grid-side converter is received through the DC bus to raise the voltage of the DC bus until the voltage of the DC bus reaches a preset threshold value and then the chopper is put into use for power discharge to achieve load balance.

10. A wind turbine torque control system based on a doubly-fed wind power converter, applied to the wind turbine torque control method based on a doubly-fed wind power converter as described in any one of claims 1 to 9 above, characterized in that: The control system includes: A power failure detection unit is used to collect the operating data of the wind turbine grid connection point and detect the grid operation status; An off-grid operation unit, used for controlling the double-fed wind power converter to switch to an off-grid mode when the grid is in a power-off state; A voltage establishing unit, used for establishing a temporary grid connection point voltage in a grid-building mode through the machine-side converter; A power output unit, used to output the torque support power required after power failure according to the torque value of the wind turbine set before power failure; A power absorption unit is used to absorb the torque support power through the grid-side converter to achieve load balancing.

11. The wind turbine torque control system based on a double-fed wind power converter according to claim 10, characterized in that: The control system also includes: The power discharge unit is used to receive the torque support power input by the grid-side converter through the DC bus to raise the voltage of the DC bus until the voltage of the DC bus reaches a preset threshold value and then the chopper is put into use for power discharge to achieve load balance.

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