A control method of a network-constructed doubly-fed asynchronous wind power generation system with power control capability

Abstract

The application belongs to the technical field of power electronic converter control, and discloses a control method of a grid-connected double-fed asynchronous wind power generation system with power control capability, which comprises a control process of a rotor-side converter and a control process of a grid-side converter, wherein the rotor-side converter forms a grid-connected characteristic at the motor stator winding port and controls the energy injected into the DC bus capacitor; the grid-side converter maintains the input and output energy balance of the DC bus capacitor, thereby controlling the DC bus capacitor voltage to be constant; the control process of the rotor-side converter comprises a frequency support control loop, a power control loop, a voltage and current inner loop and pulse width modulation control, and the control process of the grid-side converter comprises a DC voltage control loop, a reactive power control loop, an AC current control loop and pulse width modulation control. The application can realize the grid-connected power dynamic index and provide the output power control capability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronic converter control, and relates to a control method of a network-constructed double-fed asynchronous wind power generation system with power control capability. BACKGROUND

[0002] With the gradual increase of new energy power generation in the power system, the power electronic converter control technology based on new energy power generation system has gradually become a key technology for the construction of new power systems. Wind power generation has the characteristics of centralized management, sustainability, and low operation and maintenance cost. Double-fed asynchronous wind generators have lower costs due to the absence of permanent magnets and have been widely used in wind power plants.

[0003] A double-fed wind power generation system includes a rotor side converter (RSC) and a grid side converter (GSC). The rotor side converter is connected to the rotor winding of a double-fed asynchronous motor, and the grid side converter is connected to the stator winding. After being connected to the grid through a transformer, the rotor side converter and the grid side converter are connected to the same DC bus capacitor through a DC port.

[0004] The control method of the power electronic converter can be divided into two types: grid-following control and grid-forming control. In grid-following control, the converter is synchronized with the grid voltage based on the information of a phase-locked loop, and presents current source characteristics to the outside. In grid-forming control, the converter does not rely on the phase-locked loop to synchronize with the grid voltage, and presents voltage source characteristics to the outside.

[0005] The control method of the power electronic converter in the traditional wind power system is grid-following control. Due to its current source characteristics, a large number of new energy power electronic converters will reduce the strength of the grid, which is reflected in the reduction of the inertia of the power system, the reduction of short-circuit capacity, and the deterioration of stability. The grid-forming converter can provide voltage support, thereby further improving the strength of the grid after a large number of wind power systems are connected, and improving the power quality.

[0006] Currently, the double-fed wind power system with grid-forming control still has several deficiencies, mainly in the control coordination mode of the rotor side converter and the grid side converter, and the power dynamic characteristics of the grid-forming control.

[0007] The inertia response control method of the DC capacitor voltage inertia synchronous grid-forming type control method adopted in the document

S. Xu, H. Wang, Y. Cao, S. Igarashi, J. Li, and X. Cai, “Inertia Response Control of Self-synchronous Voltage Source Doubly-fed Wind Turbines in the Whole Wind Speed Range”

[0008] The virtual synchronous generator grid-forming control method adopted in the document

S. Wang, J. Hu, and X. Yuan, “Virtual Synchronous Control for Grid-Connected DFIG-Based Wind Turbines”

[0009] At the same time, the wind power system often has upper and lower limits of the output power and a frequency dead zone range of the frequency modulation function. The conventional grid-forming control method relies on a control structure switching mechanism to realize the above functions, thereby introducing discontinuous nonlinear elements in the control loop, which is not conducive to the smooth operation of the wind power system. SUMMARY

[0010] The purpose of the present application is to overcome the defects of the coordination between the converters, the power dynamic characteristics of the grid-forming control in the prior art, and to provide a control method of a grid-forming doubly-fed asynchronous wind power system with power control capability. The present application can realize the grid-forming power dynamic index while providing the ability of output power control.

[0011] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0012] A control method of a grid-forming doubly-fed induction wind power generation system with power control capability, comprising a control process of a rotor-side converter and a control process of a grid-side converter, wherein the rotor-side converter forms a grid-forming characteristic at the stator winding port of the motor and controls the energy injected into the DC bus capacitor; the grid-side converter maintains the input and output energy balance of the DC bus capacitor, thereby controlling the DC bus capacitor voltage to be constant;

[0013] The control process of the rotor-side converter comprises a frequency support control loop, a power control loop, a voltage and current inner loop, and a pulse width modulation control, wherein the frequency support control loop constructs an output power instruction in accordance with the grid point frequency variation to meet the grid index; the power control loop controls the output power to follow the instruction signal by adjusting the converter reference phase instruction; the voltage and current inner loop adjusts the voltage modulation waveform to make the stator voltage follow the voltage variation according to the voltage phase instruction and the given amplitude instruction; and the modulation waveform output by the voltage and current inner loop is subjected to pulse width modulation control to generate a driving signal for the rotor-side inverter;

[0014] The control process of the grid-side converter comprises a DC voltage control loop, a reactive power control loop, an AC current control loop, and a pulse width modulation control, wherein the DC voltage control loop maintains the DC bus capacitor voltage to follow the given instruction value by adjusting the AC current d-axis instruction; the reactive power control loop maintains the grid-side converter output reactive power to follow the given instruction value by adjusting the AC current q-axis instruction; the AC current control loop adjusts the voltage modulation waveform to make the output AC current follow the instruction value; and the modulation waveform output by the AC current control loop is subjected to pulse width modulation control to generate a driving signal for the grid-side inverter.

[0015] Preferably, the input signal of the frequency support control loop is the AC voltage frequency at the grid point, and the mathematical expression of the frequency support control loop is as follows:

[0016]

[0017] Wherein, Δ P is the dynamic change of the output power instruction, K f is the primary frequency modulation coefficient, P set is the set output power of the current wind power generation system, f PCC is the AC voltage frequency at the grid point, Δ f PCC is the AC voltage frequency variation at the grid point, f N is the rated frequency of the grid voltage, T j is the inertia response time constant, Tf is the filter time constant, s is the Laplace operator, f DB is the given frequency deadband value.

[0018] Preferably, the input signal of the power control loop is the active power reference command and the reactive power reference command, and the output is the stator internal voltage phase ref and the stator voltage magnitude command U s , which is as follows:

[0019]

[0020]

[0021] wherein: s is the Laplace operator, K d is the derivative controller coefficient, K p is the proportional controller coefficient, K i is the integral controller coefficient, K ii is the second-order integrator coefficient, P ref is the active power reference command, P is the actual output active power, U N is the rated stator voltage magnitude, K pQ is the proportional controller coefficient, K iQ is the integral controller coefficient, Q ref is the reactive power reference command, Q is the actual output reactive power.

[0022] Preferably, the voltage and current inner loop is based on a proportional-integral controller and a coordinate rotation transformation.

[0023] Preferably, the voltage and current inner loop adjusts the voltage modulation waveform according to the voltage phase command and the given magnitude command to make the stator voltage follow the voltage change, and the calculation method is as follows:

[0024]

[0025] wherein, u rscd is the rotor-side converter d-axis voltage modulation command, u sq is the actual stator q-axis voltage, Krvp and K rvi Kp and Ki are the proportional and integral coefficients of the voltage loop proportional-integral controller, respectively, s Laplace operator, i rd id is the actual d-axis rotor current, K rcp and K rci Kp and Ki are the proportional and integral coefficients of the current loop proportional-integral controller, respectively, ω ωes is the stator internal EMF angle frequency, L r Lr is the rotor-side converter filter inductance, i rq iq is the actual q-axis rotor current, u rscq Vqr* is the rotor-side converter q-axis voltage modulation instruction, U s Vsm* is the stator voltage magnitude instruction, u sd Vsd is the actual stator d-axis voltage, i rq iq is the actual q-axis rotor current, i rq iq is the actual q-axis rotor current.

[0026] Preferably, the control of the grid-side converter includes a DC voltage control loop, a reactive power control loop and an AC current control loop, and the calculation method of the grid-side converter control is as follows:

[0027]

[0028] wherein, u gscd Vsd* is the grid-side converter d-axis voltage modulation instruction, u dc-ref Vdc0 is the DC bus capacitor voltage rated value, u dc Vdc is the actual DC bus capacitor voltage, K gvp Kpdc is the DC voltage controller proportional coefficient, s Laplace operator, K gvi Kidc is the DC voltage controller integral coefficient, i gd id* is the grid-side converter output d-axis current, K gcp Kpac is the AC current controller proportional coefficient, K gci Kiac is the AC current controller integral coefficient, u gd Vsd* is the grid-side converter d-axis voltage reference,ω is a stator internal potential angle frequency, L g is a grid-side converter filter inductance value, i gq is a grid-side converter output q-axis current, u gscq is a grid-side converter q-axis voltage modulation instruction, Q gref is a grid-side converter reactive power reference value, Q g is a grid-side converter actual output reactive power, K gqp is a reactive power controller proportional coefficient, K gqi is a reactive power controller integral coefficient, i gq is a grid-side converter output q-axis current, u gq is a grid-side converter q-axis voltage reference, i gd is a grid-side converter output d-axis current.

[0029] Preferably, the frequency support control loop comprises a frequency dead zone controller, an inertia response controller, a primary frequency modulation controller and a power limiting controller; wherein the grid voltage frequency information is first filtered by the frequency dead zone controller, the part exceeding the frequency dead zone range is sent to the inertia response controller and the primary frequency modulation controller, the output power change amount required by inertia support and primary frequency modulation is calculated respectively, and after being adjusted by the power limiting controller, the output power reference instruction is formed.

[0030] Preferably, the power control loop comprises an active control loop and a reactive control loop, wherein the active control loop comprises a proportional integral derivative controller and a frequency integrator connected in parallel to generate a synchronous coordinate system reference phase; the reactive control loop adopts a proportional integral controller to generate an alternating current voltage reference amplitude.

[0031] Preferably, the voltage and current inner loop comprises a stator voltage control loop, a control coordinate system rotation and a rotor current control loop, wherein the stator voltage control loop uses a proportional integral controller, and the rotor current control loop adopts a proportional integral controller with a cross decoupling term; wherein the control signal output by the stator voltage control loop is adjusted by the control coordinate system rotation and used as the reference instruction of the rotor current control loop.

[0032] Preferably, the alternating current control loop is a proportional integral controller with a cross decoupling term and an alternating current voltage feedforward term.

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

[0034] The control method of the network-constructed double-fed asynchronous wind power generation system with power control capability can improve the power output characteristics of the network-constructed double-fed wind power generation system, improve the wind energy utilization rate of the double-fed asynchronous wind power generation system, and realize smooth switching of the frequency dead zone and power limiting in the frequency modulation process, which is specifically embodied in that: 1. The whole machine is realized by adopting the network control. The power control ring in the rotor side converter control generates a voltage reference phase θ ref So that the converter can realize synchronization with the power grid without relying on the phase-locked loop, has stronger weak grid adaptability, and has stronger power grid frequency and voltage support capability in grid-connected operation. 2. Emphasize the cooperation of the double-port control to realize better network construction characteristics. The rotor side converter adopts the network-constructed control method, and the network side converter adopts the network-following control method, which avoids the power ring oscillation problem caused by the small AC line impedance when the two side converters adopt the network-constructed control method, and realizes the reasonable cooperation of the two side converters. 3. Novel network control architecture, considering the flexibility of power control. The frequency support control ring and the power control ring are separated in the rotor side converter control, the frequency support control ring simulates the network dynamic characteristics, the independent power control ring, combined with the voltage and current inner loop control, can realize the rapid and accurate tracking of the output power. Its advantages are that it can meet various power response modes such as frequency dead zone and power limiting without introducing control structure switching; at the same time, the power reference P ref When the wind speed and the rotor speed of the wind turbine change, the output power does not need to go through the network dynamic adjustment process, and can quickly track the power reference change, thereby improving the wind energy capture efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The control block diagram of the network-constructed double-fed asynchronous wind power generation system with power control capability is provided.

[0036] Figure 2 The RSC frequency support control ring block diagram is provided.

[0037] Figure 3 The RSC power control ring block diagram is provided.

[0038] Figure 4 The RSC voltage and current inner loop control block diagram is provided.

[0039] Figure 5 The GSC control block diagram is provided.

[0040] Figure 6 The simulation results of the grid frequency 0.5Hz / s slope change in the embodiment of the application are provided.

[0041] Figure 7Simulation result of 0.2Hz step deviation of grid frequency in the embodiment of the present application;

[0042] Figure 8 Simulation result of 0.2Hz step recovery of grid frequency in the embodiment of the present application;

[0043] Figure 9 Simulation result of step in the dead zone of grid frequency and 0.5Pu step of set output power in the embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the embodiment of the present application more clear, the technical scheme in the embodiment of the present application will be described clearly and completely below with reference to the drawings in the embodiment of the present application.

[0045] Reference Figure 1 , the control method of the power control capable grid-connected type doubly-fed asynchronous wind power generation system of the present application comprises the control method of the rotor side converter of the grid-connected type doubly-fed wind power generation system and the control method of the grid side converter. The rotor side converter forms the grid-connected type characteristic at the stator winding port of the motor and controls the energy injected into the DC bus capacitor; the grid side converter maintains the input and output energy balance of the DC bus capacitor, thereby controlling the constant DC bus capacitor voltage.

[0046] The control process of the rotor side converter comprises four parts: frequency support control loop, power control loop, voltage and current inner loop and pulse width modulation control. The frequency support control loop comprises frequency dead zone controller, inertia response controller, primary frequency control controller and power limiting controller. The grid voltage frequency information is first filtered by the frequency dead zone controller, the part exceeding the frequency dead zone range is sent to the inertia response controller and the primary frequency control controller, the output power change amount required by inertia support and primary frequency control is calculated respectively, and the upper and lower limits are adjusted by the power limiting controller to generate the output active power instruction of the wind power generation system P ref . The power control loop comprises active control loop and reactive control loop. The active control loop comprises two parts: parallelly connected proportional integral derivative controller and frequency integrator, which generates the synchronous coordinate system reference phase θ ref ; the reactive control loop is a proportional integral controller, which generates the AC voltage reference amplitude U refThe inner voltage and current loop includes a stator voltage control loop, a control coordinate system rotation, and a rotor current control loop. The stator voltage control loop uses a proportional-integral controller, while the rotor current controller uses a proportional-integral controller with a cross-decoupling term. The control signal output by the stator voltage control loop, after adjustment based on the control coordinate system rotation, serves as a reference for the rotor current control loop. The modulated waveform output by the inner voltage and current loop undergoes pulse-width modulation control to generate the drive signal for the rotor-side inverter.

[0047] The control process of the grid-side converter includes four parts: DC voltage control loop, reactive power control loop, AC current control loop and pulse width modulation control. The DC voltage control loop is a proportional-integral controller that generates the d-axis current reference command. i d-ref The reactive power control loop is a proportional-integral controller that generates the q-axis current reference command. i q-ref The AC current control loop is a proportional-integral controller with a cross-decoupling term and an AC voltage feed-forward term. The modulated waveform output by the AC current control loop undergoes pulse-width modulation to generate the drive signal for the grid-side inverter.

[0048] For details, see Figure 1 The control included in the present invention is mainly divided into two parts: rotor-side converter control and grid-side converter control, and also includes a control module for auxiliary coordinate transformation such as a phase-locked loop. In the rotor-side converter control, the frequency support control link constructs an output power instruction that meets the grid indicators based on the frequency change of the grid connection point; the power control loop controls the output power to follow the instruction signal by adjusting the converter reference phase instruction; the voltage and current inner loop adjusts the voltage modulation waveform according to the voltage phase instruction and the given amplitude instruction so that the stator voltage follows the voltage change. In the grid-side converter control, the DC voltage control loop maintains the DC bus capacitor voltage following the given instruction value by adjusting the AC current d-axis instruction; the reactive power control loop maintains the grid-side converter output reactive power following the given instruction value by adjusting the AC current q-axis instruction; the current inner loop adjusts the voltage modulation waveform so that the output AC current follows the instruction value.

[0049] like Figure 2 As shown, the input signal of the frequency support control loop is the AC voltage frequency at the grid connection point. f PCC . f DB is the dead zone value of the given frequency, f N is the rated frequency of the grid voltage. The filter adopts a first-order low-pass filter, and the filter time constant is T f The inertia response time constant is Tj , the primary frequency modulation coefficient is K f , and the output power instruction dynamic change amount P , the output power instruction dynamic change amount P set , the current wind power system set output power P ref , the output power instruction value containing the dynamic change amount s , the Laplace operator. The mathematical expression of the frequency support control loop is as follows:

[0050]

[0051] The saturation limiter L1 is responsible for realizing the frequency dead zone of the inertia response, L2 is responsible for realizing the one-way response characteristic and regulation limiter of the inertia response, L3 is responsible for realizing the frequency dead zone and regulation limiter of the primary frequency modulation, and L4 is responsible for realizing the output power reference instruction limiter.

[0052] As shown in Figure 3 , the input signal of the power control loop is the active power reference instruction P ref and the reactive power reference instruction Q ref . The active loop uses a proportional-integral-derivative controller in parallel with a second-order integrator, wherein, P is the actual output active power, K p is the proportional controller coefficient, K i is the integral controller coefficient, K d is the derivative controller coefficient, K ii is the second-order integrator coefficient, is the rated grid angular frequency, is the stator internal electromotive force angular frequency, ref is the stator internal electromotive force phase, is the rotor electric angle of the doubly-fed motor, is the rotor side converter internal electromotive force phase. The mathematical expression of the active loop is as follows:

[0053]

[0054] The reactive loop uses a proportional-integral controller, wherein, Q is the actual output reactive power, K pQ is the proportional controller coefficient, K iQ is the integral controller coefficient, UN is the rated stator voltage amplitude, U s is the stator voltage amplitude command. The mathematical expression of the reactive power loop is as follows:

[0055]

[0056] As shown in Figure 4 , the rotor-side converter voltage and current inner loop is realized based on a proportional-integral controller and coordinate rotation transformation. Among them, u rscd is the rotor-side converter d-axis voltage modulation command, u rscq is the rotor-side converter q-axis voltage modulation command, u sd is the actual stator d-axis voltage, u sq is the actual stator q-axis voltage, i rd_ref is the d-axis rotor current reference command, i rq_ref is the q-axis rotor current reference command, i rd is the actual d-axis rotor current, i rq is the actual q-axis rotor current, u rd is the rotor-side converter d-axis voltage reference, u rq is the rotor-side converter q-axis voltage reference, L r is the rotor-side converter filter inductance. K rvp and K rvi are the proportional and integral coefficients of the voltage loop proportional-integral controller, respectively, K rcp and K rci are the proportional and integral coefficients of the current loop proportional-integral controller, respectively. The mathematical expression of the voltage and current inner loop is as follows:

[0057]

[0058] As shown in Figure 5 , the control of the grid-side converter includes a DC voltage control loop, a reactive power control loop, and an AC current control loop. Among them, u gscd is the grid-side converter d-axis voltage modulation command, u gscq is the grid-side converter q-axis voltage modulation command, K gvp is the DC voltage controller proportional coefficient,K gvi is the integral coefficient of the DC voltage controller, K gcp is the AC current controller proportional coefficient, K gci is the integral coefficient of the AC current controller, K gqp is the proportional coefficient of the reactive power controller, K gqi is the integral coefficient of the reactive power controller, u dc-ref is the DC bus capacitor voltage rating, u dc is the actual DC bus capacitor voltage, Q gref is the reactive power reference value of the grid-side converter, Q g is the actual output reactive power of the grid-side converter, i gd is the d-axis current output by the grid-side converter, i gq is the q-axis current output by the grid-side converter, u gd is the grid-side converter d-axis voltage reference, u gq is the grid-side converter q-axis voltage reference, and Lg is the grid-side converter filter inductance. The grid-side converter control mathematical expression is as follows:

[0059]

[0060] The most important innovation of the wind power generation system control method proposed in the present invention lies in the design of the grid-type control link in the rotor-side converter. In traditional grid-type control, the relationship between power P and power angle θ is used to achieve synchronization between the wind turbine and the power grid; the difference in the effects of different grid-type control methods lies mainly in the different frequency support dynamic characteristics of the power grid, that is, when the grid frequency changes, the output power dynamic characteristics of the wind turbine response are different. In the traditional grid-type control scheme, the two functions of "synchronization using the power-power angle relationship" and "constructing frequency support dynamic characteristics" are implemented in the same control loop, which makes the two affect each other and cannot achieve fast and accurate output power tracking; at the same time, the control structure switching introduced to achieve the frequency support dead zone and the dynamic adjustment dead zone will cause conflicts between multiple integrators in the control loop, requiring additional solutions.

[0061] The remaining parts, such as DC bus capacitor voltage control, reactive power-voltage amplitude control, current-type grid-following control scheme, etc. are not original designs of the present invention and are only components that form a complete control scheme.

[0062] Example:

[0063] The control parameters used in the simulation experiment are shown in Table 1:

[0064] Table 1

[0065]

[0066] The method proposed in this embodiment is verified for effectiveness in different grid frequency fluctuation processes and set output power P set variation processes.

[0067] Figure 6-9 The waveform diagram shows the grid frequency variation, active power reference and actual output power variation, and grid-forming control internal potential frequency variation.

[0068] Among them, the results of the 0.5Hz / s ramp variation process of the grid frequency are shown in Figure 6 It can be seen that when the grid frequency exceeds the frequency dead zone range, the active power reference P ref gradually increases until the set power upper limit is reached, and the actual output power always follows the power reference value.

[0069] The variation process of the grid frequency deviating from the rated frequency by 0.2Hz step is shown in Figure 7 It can be seen that the active power can follow the reference value, and exhibits similar inertia response characteristics when the frequency deviates from the step moment.

[0070] The variation process of the grid frequency returning to the rated frequency by 0.2Hz step is shown in Figure 8 It can be seen that the active power can follow the reference value, and does not exhibit inertia response characteristics in the process of frequency recovery step.

[0071] The process of the grid frequency variation within the dead zone and the set output power Pset variation by 0.5Pu step is shown in Figure 9 It can be seen that when the grid frequency steps within the dead zone, the output power still follows the power reference value; when the set output power Pset varies by step, the output active power can quickly follow the power reference value, and does not exhibit inertia response dynamic characteristics.

[0072] From the above scheme can be seen, the present application for doubly-fed wind power generation system, in the rotor side converter using without phase-locked loop network type control method, and the introduction with stator voltage control of inner ring, can be in the stator port to achieve the ability of self-construction voltage, improve the grid strength; in the network side converter, still using the traditional follow network type control scheme, realize the fast, accurate control of DC bus capacitor voltage, avoid the conflict with the rotor side converter on the control target, and conducive to the existing wind power plant quickly complete the generator network type transformation; in the rotor side converter network type control link, design frequency support control ring and power control ring two relatively independent control part, the dynamic characteristics of network type wind farm involved in frequency regulation, with the power-angle relationship dependent power synchronization characteristics are separated, so as to be able to in the premise of not dependent on mode switching, realize the frequency dead zone, power limiting function, and maintain the precise following of the fan output power to the reference value.

[0073] Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative labor should belong to the scope of protection of the present application.

[0074] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application rather than limit them, although the present application has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that: still can be modified or equivalent to replace the specific embodiments of the present application without making creative labor, any modification or equivalent to replace without departing from the spirit and scope of the present application, its should be covered in the protection scope of the claims of the present application.

Claims

1. A control method for a grid-type doubly-fed asynchronous wind power generation system with power control capability, characterized in that: This includes the control process of the rotor-side converter and the grid-side converter. The rotor-side converter forms a grid-like characteristic at the motor stator winding port and controls the energy injected into the DC bus capacitor. The grid-side converter maintains the input and output energy balance of the DC bus capacitor, thereby controlling the DC bus capacitor voltage to be constant. The control process of the rotor-side converter includes: frequency support control loop, power control loop, voltage and current inner loop and pulse width modulation control, among which the frequency support control loop constructs an output power instruction that meets the grid indicators according to the frequency change of the grid connection point; the power control loop controls the output power to follow the instruction signal by adjusting the converter reference phase instruction; the voltage and current inner loop adjusts the voltage modulation waveform according to the voltage phase instruction and the given amplitude instruction so that the stator voltage follows the voltage change; the modulation waveform output by the voltage and current inner loop is pulse width modulation controlled to generate a drive signal for the rotor-side inverter; among which the input signals of the power control loop are the active power reference instruction and the reactive power reference instruction, and the output stator internal potential phase ref and stator voltage amplitude command U s , as follows: in: s is the Laplace operator, K d is the derivative controller coefficient, K p is the proportional controller coefficient, K i is the integral controller coefficient, K ii is the second-order integrator coefficient, P ref is the active power reference instruction, P is the actual output active power, U N is the rated stator voltage amplitude, K pQ is the proportional controller coefficient, K iQ is the integral controller coefficient, Q ref is the reactive power reference instruction, Q is the actual output reactive power; The control process of the grid-side converter includes: DC voltage control loop, reactive power control loop, AC current control loop and pulse width modulation control. Among them, the DC voltage control loop maintains the DC bus capacitor voltage following the given instruction value by adjusting the AC current d-axis instruction; the reactive power control loop maintains the grid-side converter output reactive power following the given instruction value by adjusting the AC current q-axis instruction; the AC current control loop adjusts the voltage modulation waveform so that the output AC current follows the instruction value; the modulation waveform output by the AC current control loop is controlled by pulse width modulation to generate a drive signal for the grid-side inverter.

2. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The input signal of the frequency support control loop is the AC voltage frequency at the grid connection point. The mathematical expression of the frequency support control loop is as follows: Among them, Δ P is the dynamic change of the output power instruction, K f is the primary frequency modulation coefficient, P set is the set output power of the current wind power generation system, f PCC is the AC voltage frequency at the grid connection point, Δ f PCC is the AC voltage frequency change value at the grid connection point, f N is the rated frequency of the grid voltage, T j is the inertia response time constant, T f is the filter time constant, s is the Laplace operator, f DB is the dead zone value of the given frequency.

3. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The voltage and current inner loop is realized based on proportional-integral controller and coordinate rotation transformation.

4. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 3, characterized in that: The voltage and current inner loop adjusts the voltage modulation waveform according to the voltage phase command and the given amplitude command so that the stator voltage follows the voltage change. The calculation method is as follows: in, u rscd is the d-axis voltage modulation instruction of the rotor-side converter, u sq is the actual stator q-axis voltage, K rvp and K rvi are the proportional and integral coefficients of the voltage loop proportional-integral controller, s is the Laplace operator, i rd is the actual d-axis rotor current, K rcp and K rci are the proportional and integral coefficients of the current loop proportional-integral controller, ω is the angular frequency of the stator internal potential, L r is the filter inductance of the rotor-side converter, i rq is the actual q-axis rotor current, u rscq is the q-axis voltage modulation instruction of the rotor-side converter, U s is the stator voltage amplitude command, u sd is the actual stator d-axis voltage, i rq is the actual q-axis rotor current, i rq is the actual q-axis rotor current.

5. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The grid-side converter control includes the DC voltage control loop, the reactive power control loop, and the AC current control loop. The calculation method for grid-side converter control is as follows: in, u gscd is the d-axis voltage modulation instruction of the grid-side converter, u dc-ref is the DC bus capacitor voltage rating, u dc is the actual DC bus capacitor voltage, K gvp is the DC voltage controller proportional coefficient, s is the Laplace operator, K gvi is the integral coefficient of the DC voltage controller, i gd is the d-axis current output by the grid-side converter, K gcp is the AC current controller proportional coefficient, K gci is the integral coefficient of the AC current controller, u gd is the grid-side converter d-axis voltage reference, ω is the angular frequency of the stator internal potential, L g is the filter inductance value of the grid-side converter, i gq is the q-axis current output by the grid-side converter, u gscq is the q-axis voltage modulation instruction of the grid-side converter, Q gref is the reactive power reference value of the grid-side converter, Q g is the actual output reactive power of the grid-side converter, K gqp is the proportional coefficient of the reactive power controller, K gqi is the integral coefficient of the reactive power controller, i gq is the q-axis current output by the grid-side converter, u gq is the grid-side converter q-axis voltage reference, i gd Output d-axis current for the grid-side converter.

6. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The frequency support control loop includes a frequency dead-band controller, an inertia response controller, a primary frequency modulation controller, and a power limiter controller. The grid voltage and frequency information is first filtered by the frequency dead-band controller. The portion exceeding the frequency dead-band range is sent to the inertia response controller and the primary frequency modulation controller. The output power changes required for inertia support and primary frequency modulation are calculated, respectively. After the upper and lower limits are adjusted by the power limiter controller, an output power reference command is formed.

7. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The power control loop includes an active power control loop and a reactive power control loop, wherein the active power control loop includes a proportional-integral-differential controller and a frequency integrator connected in parallel to generate a synchronous coordinate system reference phase; the reactive power control loop uses a proportional-integral controller to generate an AC voltage reference amplitude.

8. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The voltage and current inner loop includes the stator voltage control loop, the control coordinate system rotation and the rotor current control loop. The stator voltage control loop uses a proportional-integral controller, and the rotor current control loop uses a proportional-integral controller with a cross-decoupling term. The control signal output by the stator voltage control loop is adjusted by the control coordinate system rotation and serves as the reference instruction for the rotor current control loop.

9. The control method of a grid-type doubly-fed asynchronous wind power generation system with power control capability according to claim 1, characterized in that: The AC current control loop is a proportional-integral controller with a cross-decoupling term and an AC voltage feed-forward term.

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