A Flexible Switching Self-Frequency Modulation Control Method for Power-Speed of Grid-Forming Wind Turbines

Abstract

The present invention provides a power - speed flexible switching self - frequency modulation control method for a network - forming wind turbine. There are an active power outer - loop control module and a speed outer - loop control module. When performing power outer - loop control, the active power outer - loop control module is connected to the active power control of the machine - side converter; when performing speed outer - loop control, the speed outer - loop control module is connected to the active power control of the machine - side converter. The wind turbine control method provided by the present invention can realize the switching control between the speed and the power outer - loop on the basis of realizing the self - frequency modulation control of the wind turbine, prevent the wind turbine speed from exceeding the rated speed, and avoid the problem of out - of - control of the wind turbine speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical control of wind turbines, and particularly relates to a power - speed flexible switching self - frequency modulation control method for a grid - forming wind turbine. Background Art

[0002] Traditional full - power wind turbines adopt a converter control method based on vector control, which essentially belongs to a current - source control method and uses a double - closed - loop control strategy to achieve decoupling control; the outer loop can be an active - power loop or a speed loop; usually, an active - power outer loop is adopted. Since the influence of grid frequency on the output of the wind turbine cannot be characterized in the active - power outer loop, traditional full - power wind turbines with current - source control do not have the ability to participate in grid frequency modulation. It is necessary to add a virtual - inertia control link that reflects the change of grid frequency on the basis of traditional vector control to achieve the effect of virtual - inertia control, so that the full - power wind turbine can provide inertia and power support for the grid. A full - power wind turbine with this ability can be called a grid - forming wind turbine.

[0003] Currently, the mainstream grid - forming control method for full - power wind turbines mainly features retaining the traditional vector - control structure, that is, a double - closed - loop control. The outer loop can select a power loop or a speed loop according to control needs. The inner loop is a current loop, and synchronization with the grid is achieved through a PLL phase - locked loop. On this basis, the change is reflected in the addition of a virtual - inertia control link that reflects the change of grid frequency in the outer - loop setpoint, so that when the system frequency changes, the active - power output of the wind turbine can be changed, reflecting the control effect of active - power support.

[0004] However, the currently proposed virtual - inertia control method can only be adapted to one control outer loop. When the active power is selected as the control object of the power outer loop, the speed of the wind turbine is no longer directly controlled. As a result, the speed of the wind turbine may get out of control during the control process of inertia response. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a power - speed flexible switching self - frequency modulation control method for a grid - forming wind turbine, enabling the wind turbine to have the ability to automatically switch the control object according to needs and solve the problem of possible speed out - of - control during the traditional inertia response process.

[0006] The present invention achieves the above - mentioned technical objectives through the following technical means.

[0007] A power - speed flexible switching self - frequency modulation control method for a grid - forming wind turbine: There are an active power outer - loop control module and a speed outer - loop control module. When performing active power outer - loop control, the active power outer - loop control module is connected to the active power control of the machine - side converter; when performing speed outer - loop control, the speed outer - loop control module is connected to the active power control of the machine - side converter.

[0008] Further, according to the wind turbine speed, a switch is made between active power outer - loop control and speed outer - loop control. When the wind turbine speed reaches the rated speed, the control switches to speed outer - loop control; otherwise, active power outer - loop control is performed.

[0009] Further, in the active power outer - loop control module, the signal P in passes through a PI controller to obtain the given value i sqref1 of the q - axis component of the stator current of the wind turbine generator, where P in is obtained by the following formula:

[0010] P in = ΔP + P mref - P m

[0011] In the formula, P mref is the given active power of the wind turbine, P m is the actual value of the active power of the wind turbine, ΔP is the additional power, which is obtained by the following formula:

[0012] ΔP = ΔP d + ΔP p

[0013]

[0014] ΔP p = K p (f ref - f)

[0015] In the formula, f is the actual value of the grid frequency, K d is the differential coefficient, ΔP d is the differential additional power, f ref is the grid frequency reference value, K p is the proportional coefficient, ΔP p is the proportional additional power.

[0016] Further, in the speed outer - loop control module, the signal ω rin passes through a PI controller to obtain the given value i sqref2 of the q - axis component of the stator current of the wind turbine generator, where ω rin is obtained by the following formula:

[0017] ω rin = ωrref -ω r

[0018] Where ω rref is the set value of the rotational speed of the wind turbine, and ω r is the actual value of the rotational speed of the wind turbine.

[0019] Furthermore, there is an active current switching module for controlling the switching between the power outer loop control and the rotational speed outer loop control:

[0020]

[0021] Where i sqref is the set value of the q-axis component of the stator current of the wind turbine finally fed into the active power control of the machine-side converter.

[0022] Furthermore, in the active power control of the machine-side converter, i sqref subtracts the q-axis component i sq of the stator current and then inputs it into a PI controller. After the obtained result is inverted, it subtracts the product of the d-axis component i sd of the stator current, the rated frequency ω m and the stator inductance L s to obtain the input U md of the inverse coordinate transformation.

[0023] Furthermore, it also includes the reactive power control of the machine-side converter: The difference between the reactive power set value Q mref and the actual reactive power value Q m of the wind turbine is input into a PI controller to obtain the set value i sdref of the d-axis component of the stator current; then i sdref subtracts the actual value i sd of the d-axis component of the stator current, and the result is input into a PI controller. After the output result of the PI controller is inverted, it adds the product of the q-axis component i sq of the stator current, the rated frequency ω m and the stator inductance L s to obtain the input U mq of the inverse coordinate transformation;

[0024] Finally, the above U mq and the input U md of the inverse coordinate transformation obtained from the active power control of the machine-side converter and the rotor angle θ r are input into the inverse coordinate transformation, and the transformation result generates a pulse control signal through the SVPWM module to control the operation of the rotor-side converter.

[0025] Furthermore, there is a switching control module for controlling the switching signal H, and the active current switching module operates according to the signal H, where:

[0026] When H = i, in the active current switching module, i sqref = i sqref1 ;

[0027] When H = 0, in the active current switching module, i sqref = i sqref2 ;

[0028] The switching control module is divided into a manual switching mode and an automatic switching mode. In the manual switching mode, the signal H is specified manually; in the automatic switching mode:

[0029]

[0030] where ω r is the actual rotational speed of the wind turbine.

[0031] Furthermore, when switching from speed outer loop control to power outer loop control, the PI controller in the active power outer loop control module starts to calculate i in in real time according to P sqref1 ; the output value of the PI controller in the speed outer loop control module is locked and held at the output value at the switching instant;

[0032] When switching from power outer loop control to speed outer loop control, the PI controller in the speed outer loop control module starts to calculate i rin in real time according to ω sqref2 ; the output value of the PI controller in the active power outer loop control module is locked and held at the output value at the switching instant.

[0033] Furthermore, latchers are respectively provided in the active power outer loop control module and the speed outer loop control module. In the switching control module, according to the change of the switching signal, latch signals S 1 , S 2 and reset signals F 1 , F 2 are output, where:

[0034] When a rising edge appears in the switching signal H, set S 1 = F 1 = 0, S 2 = F 2 = 1;

[0035] When a falling edge appears in the switching signal H, set S 1 = F 1 = 1, S 2 = F 2 = 0;

[0036] In the active power outer loop control module:

[0037] When S 1 = F 1 = 1, the latch locks and records the i at the current moment sqref1 , and sends the recorded i sqref1 as the reset value j S1 to the PI controller. The PI controller performs a reset operation and uses the reset value j S1 as the output; conversely, when S 1 = F 1 = 0, the latch does not perform a locking operation and the PI controller does not perform a reset operation.

[0038] In the speed outer loop control module:

[0039] When S 2 = F 2 = 1, the latch locks and records the i at the current moment sqref2 , and sends the recorded i sqref2 as the reset value j S2 to the PI controller. The PI controller performs a reset operation and uses the reset value j S2 as the output; conversely, when S 2 = F 2 = 0, the latch does not perform a locking operation and the PI controller does not perform a reset operation.

[0040] The beneficial effects of the present invention are:

[0041] (1) The present invention provides a power - speed flexible switching self - frequency modulation control method for a network - forming wind turbine. On the basis of realizing the self - frequency modulation control of the wind turbine, it realizes the switching control between the speed and power outer loops; on the one hand, it reflects the change of the grid frequency in the active power output of the wind turbine, reflecting the effect of virtual inertia control, so that the wind turbine has the ability to participate in grid frequency modulation; on the other hand, it switches the control mode according to the wind turbine speed situation in time to prevent the wind turbine speed from exceeding the rated speed and avoid the problem of out - of - control wind turbine speed.

[0042] (2) In the present invention, by adding a reset operation to the PI controllers of both the power outer loop and the speed outer loop, the PI controller is locked and maintained at the output value at the moment of cut - out by using the reset operation, reducing the impact current generated when cutting in again later, and achieving the control purpose of flexible switching.

[0043] (3) On the basis of automatic switching, a manual switching function is added to achieve free and flexible switching between the speed outer loop and the power outer loop according to external instructions. Description of the Drawings

[0044] Figure 1This is the control block diagram of the self - frequency - modulation control method for the grid - forming type wind turbine generator set of the present invention;

[0045] Figure 2 This is the control logic flow chart of the switching control module of the present invention;

[0046] Figure 3 This is the electrical structure diagram of the grid - forming control part of the existing conventional full - power wind turbine generator set;

[0047] Figure 4 This is the control strategy block diagram of the machine - side converter part of the existing wind turbine generator set;

[0048] Figure 5 This is the control structure diagram of the wind turbine generator set set in the test example of the present invention;

[0049] Figure 6 This is the frequency - response waveform diagram (power outer loop) in the maximum - power tracking stage of the test example of the present invention;

[0050] Figure 7 This is the waveform diagram during the flexible switching process between the power outer loop and the speed outer loop in the test example of the present invention;

[0051] Figure 8 This is the frequency - response waveform diagram (speed outer loop) in the constant - speed stage of the test example of the present invention. Detailed implementation manners

[0052] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described by referring to the drawings below are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0053] The first part, description of the technical solution

[0054] As Figure 3 shown, this is the electrical structure diagram of the grid - forming control part of the existing conventional full - power wind turbine generator set, Figure 4 shown, this is the control strategy block diagram for the machine - side converter part among them. The corresponding control strategy is to add a virtual inertia control link that reflects the change of the grid frequency on the basis of traditional vector control. However, in the process of reflecting the inertia response by the above - mentioned control strategy, the rotational speed of the wind turbine is no longer directly controlled, resulting in the possible stall problem of the rotational speed of the wind turbine.

[0055] As Figure 1 shown, this is the control block diagram of the power - speed flexible switching self - frequency - modulation control method for the grid - forming type wind turbine generator set of the present invention, including ① active - power control and ② reactive - power control of the machine - side converter. Among them:

[0056] I. Reactive - power control

[0057] Reactive power control is to control the reactive power on the stator side of a full-power wind turbine to achieve unit power factor operation of the wind turbine. The specific control method is as follows:

[0058] The given reactive power Q mref of the wind turbine and the actual reactive power value Q m are input into a PI controller to obtain the given value i sdref of the d-axis component of the stator current; then, i sdref is subtracted from the actual value i sd of the d-axis component of the stator current, and the result is input into a PI controller. After taking the inverse of the output result of the PI controller, the product of the q-axis component i sq of the stator current, the rated frequency ω m and the stator inductance L s is added, and finally, the input U mq of the inverse coordinate transformation is obtained.

[0059] II. Active power control

[0060] Active power control is to control the active power of a full-power wind turbine and, according to the control command, achieve the manual or automatic switching function between the power outer loop and the speed outer loop, and realize the combined control of power control and speed control. It specifically includes the following six sub-control modules: ① Virtual inertia control module, ② Active power outer loop control module, ③ Speed outer loop control module, ④ Active current switching module, ⑤ Active power inner loop control module, ⑥ Switching control module. Among them:

[0061] 1. Virtual inertia control module

[0062] The actual value f of the grid frequency is multiplied by the differential coefficient K d after passing through the differential transfer function s to obtain the differential additional power ΔP d :

[0063]

[0064] The difference between the reference value f ref of the grid frequency and the actual value f is multiplied by the proportional coefficient K p to obtain the proportional additional power ΔP p :

[0065] ΔP p = K p (f ref - f)

[0066] The differential additional power ΔP d and the proportional additional power ΔP p are added to obtain the additional power ΔP of the entire wind turbine:

[0067] ΔP = ΔP d +ΔP p

[0068] 2. Active power outer loop control module

[0069] The above additional power ΔP is added to the active power reference P of the full-power wind turbine mref and subtracted by the actual value P of the active power of the full-power wind turbine m to obtain the input signal P of the PI controller in :

[0070] P in = ΔP + P mref - P m

[0071] P in After passing through the PI controller, the reference value i of the q-axis component of the stator current of the wind turbine is obtained sqref1 .

[0072] 3. Speed outer loop control module

[0073] The speed reference value ω of the full-power wind turbine rref is subtracted by the actual speed value ω r to obtain the input signal ω of the PI controller rin :

[0074] ω rin = ω rref - ω r

[0075] ω rin After passing through the PI controller, the reference value i of the q-axis component of the stator current of the wind turbine is obtained sqref2 .

[0076] 4. Active current switching module

[0077] An active current switching module is designed between the active power outer loop control module and the speed outer loop control module to regulate the free switching between the two control objects of active power and speed. When active power control is selected, the ② active power outer loop control module is connected; conversely, when speed control is selected, the ③ speed outer loop control module is connected. That is, one of i sqref1 and i sqref2 is selected as the final reference value i of the q-axis component of the stator current of the wind turbine sqref :

[0078]

[0079] 5. Active power inner loop control module

[0080] The above-mentioned i sqref subtracts the q-axis component i of the stator current sq and then inputs it into a PI controller. After the output result of the PI controller is inverted, it subtracts the d-axis component i of the stator current sd , the rated frequency ω m , and the stator inductance L s . The product of the three is used to obtain the input U of the inverse coordinate transformation md .

[0081] Finally, the inputs U md , U mq of the inverse coordinate transformation and the rotor angle θ r are input into the inverse coordinate transformation. The obtained transformation result is then input into the SVPWM module to generate a pulse control signal to control the operation of the rotor-side converter.

[0082] 6. Switching control module

[0083] To achieve the automatic switching function, manual switching function between the power outer loop and the speed outer loop, and ensure smooth switching during the switching process to achieve the control purpose of smooth switching; the following switching control module is designed:

[0084] (1) Switching signal H

[0085] The switching control module outputs a switching signal H. When H = 1, the active current switching module selects to connect the active power outer loop control module, and i sqref = i sqref1 ; when H = 0, the active current switching module selects to connect the speed outer loop control module, and i sqref = i sqref2 :

[0086]

[0087] (2) Switching mode selection

[0088] It includes two items: automatic switching mode and manual switching mode. When manual switching is selected, the switching signal H is specified manually.

[0089] In the automatic switching mode, the switching signal H is set according to the actual speed ω r of the wind turbine; when the wind turbine reaches the rated speed, then H = 0, and the speed outer loop control is selected; otherwise, H = 1, and the power outer loop control is selected:

[0090]

[0091] In the automatic switching mode, the switching between the power outer loop control and the speed outer loop control is carried out according to whether the fan reaches the rated speed. When the fan speed reaches the rated speed, it automatically switches to the direct speed control to avoid the out-of-control of the wind turbine speed under high wind speed conditions, thereby improving the safety of the wind turbine.

[0092] (3) Flexible switching

[0093] 1) To ensure flexible switching between the power outer loop and the speed outer loop, a latch and the corresponding latch signal S are set in the active power outer loop control module 1 , reset signal F 1 , reset value j S1 ; a latch and the corresponding latch signal S are set in the speed outer loop control module 2 , reset signal F 2 , reset value j S2 .

[0094] Taking the active power outer loop control module as an example (the speed outer loop control module is the same), first, the latch determines whether to lock and store the output value i of the PI controller at the current moment according to the received latch signal S 1 ; when S sqref1 = 1, the i at the current moment is locked and recorded 1 , and the recorded i sqref1 is used as the reset value j sqref1 and sent to the PI controller; conversely, when S S1 = 0, it is not locked. 1 The PI controller determines whether to perform a reset operation according to the received reset signal F

[0095] ; when F 1 = 1, the PI controller performs a reset operation and uses the reset value j 1 as i S1 output; conversely, when F sqref1 = 0, the PI control normally calculates i 1 in real time through the input P in . sqref1 .

[0096] 2) The latch signal S 1 , reset signal F 1 of the power outer loop and the latch signal S 2 , reset signal F 2 of the speed outer loop are all controlled by the switching control module. Specifically, the corresponding settings are made by detecting the change of the switching signal H. When the rising edge of the switching signal H is detected (H changes from 0 to 1), S 1 = F 1 = 0, S2 = F 2 = 1; and when a falling edge of the switching signal H appears (H changes from 1 to 0), then set S 1 = F 1 = 1, S 2 = F 2 = 0; at other times, the current moment values of S 1 , F 1 , S 2 , F 2 remain unchanged.

[0097] In summary, ① when switching from speed outer loop control to power outer loop control, the PI controller in the active power outer loop control module starts to normally calculate i in in real time according to P sqref1 ; the output value of the PI controller in the speed outer loop control module is locked and held at the output value at the switching moment. ② When switching from power outer loop control to speed outer loop control, the PI controller in the speed outer loop control module starts to normally calculate i rin in real time according to ω sqref2 ; the output value of the PI controller in the active power outer loop control module is locked and held at the output value at the switching moment. The flow block diagram of the control logic of the above switching control module is as Figure 2 shown.

[0098] By adding a reset operation to the PI controllers in the active power outer loop control module and the speed outer loop control module; when a certain outer loop control module is cut out, the PI controller in this control module is locked and held at the output value at the cut-out moment by using the reset operation; thereby reducing the inrush current generated when switching back to this control module again later, and achieving the control purpose of flexible switching.

[0099] The second part, simulation test

[0100] Build a grid-connected model of a 6.25 MW full-power wind turbine in the RTDS real-time digital simulator, and the structure of the simulation system is as Figure 5 shown, and the detailed parameter settings are as shown in Table 1 below:

[0101] Table 1: Parameter settings of 6.25 MW full-power wind turbine

[0102]

[0103]

[0104] As Figure 6As shown, when the ambient wind speed is 9 m / s, it corresponds to the wind turbine operating in the MPPT maximum power tracking stage. The outer loop of the wind turbine is a power loop, which reflects the control strategy of the grid-connected wind turbine. When a temporary load is applied at the simulation time t = 6 s, the frequency change of the system causes a change in the active power reference of the wind turbine, further affecting the active power output and the speed of the wind turbine. The speed of the wind turbine shows an obvious deceleration process to reflect the control effect of virtual inertia. Since the speed does not exceed the rated value during the entire response process, there is no switching between the power outer loop and the speed outer loop.

[0105] As Figure 7 shown, when the ambient wind speed gradually changes from 9 m / s to 10.5 m / s, the speed of the wind turbine increases with the increase of the wind speed. When a temporary load is applied at the simulation time t = 6 s, the speed of the wind turbine shows a downward trend, reflecting the control effect of virtual inertia response; in the later stage of speed recovery, with the increase of the wind speed, the speed reaches the rated speed, and the wind turbine switches to the speed outer loop, controlling the speed of the wind turbine to stabilize at the rated speed of 1.2 pu. At t = 25 s, although the load is applied again, the wind turbine still operates in the speed outer loop and does not respond to the grid frequency change, playing a role in protecting the wind turbine and avoiding the situation where the speed change exceeds the rated speed.

[0106] As Figure 8 shown, when the ambient wind speed is 10.5 m / s, at this time the speed of the wind turbine has stabilized at the rated speed of 1.2 pu, and the control strategy of the wind turbine has switched to the speed outer loop control strategy. When a temporary load is applied at the simulation time t = 6 s, the speed outer loop does not respond to the change of the grid frequency, so the speed of the wind turbine always remains at the rated speed, playing a role in protecting the wind turbine and avoiding the situation where the speed change exceeds the rated speed.

[0107] The present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions or deformations that those skilled in the art can make all fall within the protection scope of the present invention.

Claims

1. A power-speed flexible switching self-frequency regulation control method for a grid-type wind turbine generator set, characterized in that: An active power outer loop control module and a speed outer loop control module are provided, wherein when the power outer loop control is performed, the active power outer loop control module is connected to the active power control of the machine side converter; when the speed outer loop control is performed, the speed outer loop control module is connected to the active power control of the machine side converter; An active current switching module is provided to control the switching between the power outer loop control and the speed outer loop control: In the formula, i sqref is the given value of the q-axis component of the wind turbine stator current that is finally fed into the active power control of the machine-side converter, i sqref1 is the given value of the q-axis component of the stator current of the wind turbine generator output by the active power outer loop control module, i sqref2 is the given value of the q-axis component of the stator current of the wind turbine output by the speed outer loop control module; In the active power control of the machine-side converter, i sqref Subtract the q-axis component of the stator current i sq Then input into PI controller, the result is inverted, and then the stator current d-axis component i is subtracted. sd , rated frequency ω m , stator inductance L s The product of the three gives the input U of the inverse coordinate transformation. md .

2. The power-speed flexible switching self-frequency regulation control method of a grid-type wind turbine generator set according to claim 1 is characterized in that: According to the fan speed, switch is made between power outer loop control and speed outer loop control. When the fan speed reaches the rated speed, it switches to speed outer loop control; otherwise, power outer loop control is performed.

3. The power-speed flexible switching self-frequency regulation control method of a grid-type wind turbine generator set according to claim 2 is characterized in that: In the active power outer loop control module, the signal P in The given value i of the q-axis component of the wind turbine stator current is obtained through the PI controller. sqref1 , where P in Obtained by the following formula: P in =ΔP+P mref -P m Where P mref is the given active power of the wind turbine, P m is the actual value of the active power of the wind turbine, ΔP is the additional power, which is obtained by the following formula: ΔP=ΔP d +ΔP p ΔP p =K p (f ref -f) Where, f is the actual value of the power grid frequency, K d is the differential coefficient, ΔP d is the differential additional power, f ref is the grid frequency reference value, K p is the proportionality coefficient, ΔP p Add power to the ratio.

4. The power-speed flexible switching self-frequency regulation control method of a grid-type wind turbine generator set according to claim 3 is characterized in that: In the speed outer loop control module, the signal ω rin The given value i of the q-axis component of the wind turbine stator current is obtained through the PI controller. sqref2 , where ω rin Obtained by the following formula: oh rin =ω rref -oh r In the formula, ω rref is the given speed of the wind turbine, ω r is the actual speed of the wind turbine.

5. The power-speed flexible switching self-frequency regulation control method of a grid-type wind turbine generator set according to claim 1 is characterized in that: It also includes the reactive power control of the machine-side converter: the reactive power of the wind turbine is given by Q mref And the actual value of reactive power Q m The difference is input into the PI controller to obtain the given value i of the stator current d-axis component sdref ; then by i sdref Subtract the actual value of the stator current d-axis component i sd The result is input into the PI controller. The output of the PI controller is inverted and then added to the stator current q-axis component i sq , rated frequency ω m , stator inductance L s The product of the three gives the input U of the inverse coordinate transformation. mq ; Finally, the above U mq , the inverse coordinate transformation input U obtained by the active power control of the machine side converter md and the rotor angle θ r The input is inverse coordinate transformation, and the transformation result is generated by the SVPWM module to generate a pulse control signal to control the operation of the rotor side converter.

6. The power-speed flexible switching self-frequency regulation control method of a grid-type wind turbine generator set according to claim 1 is characterized in that: A switching control module is provided for controlling a switching signal H, and the active current switching module performs an operation according to the signal H, wherein: When H=1, the active current switching module i sqref =i sqref1 ; When H=0, the active current switching module i sqref =i sqref2 ; The switching control module is divided into manual switching mode and automatic switching mode. In the manual switching mode, the signal H is manually specified; in the automatic switching mode: In the formula, ω r is the actual speed of the wind turbine.

7. The power-speed flexible switching self-frequency regulation control method of a grid-type wind turbine generator set according to claim 6 is characterized in that: When the speed outer loop control is switched to the power outer loop control, the PI controller in the active power outer loop control module starts to normally control the active power according to P in Real-time computing sqref1 ; The output value of the PI controller in the speed outer loop control module is locked and maintained at the output value at the switching moment; When the power outer loop control is switched to the speed outer loop control, the PI controller in the speed outer loop control module starts to work normally according to ω rin Real-time computing sqref2 The output value of the PI controller in the active power outer loop control module is locked and maintained at the output value at the switching moment.

8. The power-speed flexible switching self-frequency regulation control method for a grid-type wind turbine generator set according to claim 6 is characterized in that: The active power outer loop control module and the speed outer loop control module are respectively provided with latches. In the switching control module, latch signals S1, S2 and reset signals F1, F2 are output according to the change of the switching signal, wherein: When the switching signal H has a rising edge, set S1 = F1 = 0, S2 = F2 = 1; When the switching signal H has a falling edge, set S1 = F1 = 1, S2 = F2 = 0; In the active power outer loop control module: When S1=F1=1, the latch locks and records the current i sqref1 , and record the i sqref1 As the reset value j S1 The PI controller performs a reset operation and sets the reset value j S1 As output; on the contrary, when S1=F1=0, the latch does not perform the locking operation and the PI controller does not perform the reset operation; In the speed outer loop control module: When S2=F2=1, the latch locks and records the current i sqref2 , and record the i sqref2 As the reset value j S2 The PI controller performs a reset operation and sets the reset value j S2 As output; on the contrary, when S2=F2=0, the latch does not perform the locking operation and the PI controller does not perform the reset operation.

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