Double-fed wind generator grid connection and power direct vector control method

Abstract

The invention relates to a doubly-fed wind generator grid connection and power direct vector control method, which comprises the following steps of: starting a doubly-fed wind generator, introducing direct current excitation to a rotor excitation winding, and detecting the output voltage frequency of the doubly-fed wind generator; when it is determined that the output voltage frequency is the same as the power grid voltage frequency, the direct-current excitation is disconnected, and the doubly-fed wind generator is connected with the power grid; after grid connection, an excitation power supply is connected, the voltage of an excitation winding is detected, and the voltage of the excitation winding is utilized to adjust the output voltage of the excitation power supply; and adjusting the output voltage of the excitation power supply to respectively carry out grid-connected reactive current control and grid-connected active current control of the doubly-fed wind generator. According to the invention, grid-connected operation of the doubly-fed wind driven generator without the rotating speed sensor is realized, and active power and reactive power control is effectively carried out; generator excitation winding voltage is synchronously tracked to realize generator grid-connected operation power control, and good dynamic control performance and high and low voltage ride through functions are realized.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation technology, and in particular to a method for grid connection and direct vector power control of a doubly fed wind turbine. Background Technology

[0002] Existing doubly-fed induction generator (DFIG) wind power systems require the installation of speed sensors, reducing the system's mechanical strength. Grid connection control of the wind turbine requires tracking the grid voltage; the time difference between tracking and grid connection leads to current surges during connection. During grid connection and operation, the generator needs to track the grid voltage frequency and phase, primarily using a phase-locked loop (PLL) control algorithm. This algorithm involves dynamic adjustment, which introduces errors in the generator's output frequency and phase compared to the grid voltage during frequency and phase locking. This is a major cause of low-frequency oscillations in the power system caused by DFIG wind power systems, and the algorithm must also meet low-voltage ride-through requirements. Therefore, a direct vector control method for DFIG wind turbine grid connection and power output is urgently needed. Summary of the Invention

[0003] The purpose of this invention is to provide a method for grid connection and direct vector power control of a doubly fed wind turbine generator, which solves the problem of dynamic errors in the generator grid connection and operation control tracking of grid voltage frequency and phase in the prior art, resulting in power fluctuations during generator grid connection operation. The method can provide active power support required during faults by keeping the control power angle constant, and has low voltage and high voltage ride-through functions.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A method for grid connection and direct vector power control of a doubly-fed wind turbine includes:

[0006] Start the doubly-fed wind turbine generator, supply DC excitation to the rotor excitation winding, and detect the output voltage frequency of the doubly-fed wind turbine generator;

[0007] When it is determined that the output voltage frequency is the same as the grid voltage frequency, the DC excitation is disconnected, and the doubly-fed wind turbine is connected to the grid.

[0008] After grid connection, the excitation power supply is connected, the voltage of the excitation winding is detected, and the output voltage of the excitation power supply is adjusted using the voltage of the excitation winding.

[0009] The output voltage of the excitation power supply is adjusted to control the reactive current and active current of the doubly-fed wind turbine generator connected to the grid.

[0010] Optimally, determining that the output voltage frequency is the same as the grid voltage frequency includes:

[0011] Obtain the phase sequence of the doubly-fed wind turbine generator and the phase sequence of the grid voltage;

[0012] Calculate the generator speed based on the output voltage frequency;

[0013] When the phase sequence of the doubly fed wind turbine is the same as the phase sequence of the grid voltage, and the generator speed reaches the synchronous speed, the output voltage frequency is the same as the grid voltage frequency.

[0014] Optimally, after grid connection, the excitation power supply is connected, the excitation winding voltage is detected, and the output voltage of the excitation power supply is adjusted using the excitation winding voltage, including:

[0015] Connect the excitation power supply and detect the excitation winding voltage of the doubly fed wind turbine after grid connection;

[0016] Calculate the frequency, amplitude, and phase of the excitation winding voltage, and use the frequency, amplitude, and phase to modulate the excitation power supply output voltage so that the frequency, amplitude, and phase of the excitation winding voltage are the same as the frequency, amplitude, and phase of the excitation power supply output voltage.

[0017] Optimally, adjusting the output voltage of the excitation power supply for grid-connected reactive current control of the doubly-fed wind turbine includes:

[0018] Obtain the output current of the doubly fed wind turbine after grid connection;

[0019] Calculate the reactive current based on the output current;

[0020] The system's setpoint reactive current is preset to the reactive current closed-loop control unit.

[0021] Calculate the excitation power supply output voltage setpoint coefficient by combining the reactive current and the system given reactive current;

[0022] The amplitude of the excitation power supply output voltage is adjusted based on the given coefficient of the excitation power supply output voltage to control the reactive current.

[0023] Optimally, adjusting the output voltage of the excitation power supply for grid-connected active current control of the doubly-fed wind turbine includes:

[0024] Obtain the output current of the doubly fed wind turbine after grid connection;

[0025] Calculate the active current based on the output current;

[0026] Based on the active current and the given active current of the system, calculate the phase setting of the excitation power supply output voltage;

[0027] The output voltage phase of the doubly-fed wind turbine is controlled based on the phase of the excitation power supply output voltage, and it is determined that the output voltage phase leads the grid voltage phase.

[0028] A phase control function is constructed, and the output voltage phase of the doubly-fed wind turbine is adjusted based on the phase control function, thereby adjusting the active current.

[0029] The phase control function can be optimized as follows:

[0030]

[0031] Among them, u o (s) is the output voltage signal of the phase control function, u i (s) is the input voltage signal for the phase control function, K δC τ is the gain compensation coefficient for the advance angle control signal. RC is the time constant.

[0032] The method can be optimized by further including: detecting the rotor operating speed of the doubly-fed wind turbine after grid connection.

[0033] Optimally, the rotor operating speed of the doubly-fed wind turbine after grid connection can be detected by including:

[0034] Obtain the excitation winding voltage frequency and the doubly-fed wind turbine output voltage frequency;

[0035] The rotor speed is calculated based on the excitation winding voltage frequency and the doubly fed wind turbine output voltage frequency.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention utilizes technology that tracks the frequency, phase, and amplitude of the excitation winding voltage of a doubly-fed induction generator (DFIG) to achieve sensorless grid-connected operation of the DFIG. Specifically, it controls the reactive current during grid-connected operation by adjusting the generator's output voltage amplitude and controls the phase difference between the generator's output voltage and the grid voltage by adjusting the excitation power supply's output voltage phase, thereby controlling the active current. This invention combines the operating principle of DFIGs with the advantages of sensorless grid-connected operation and power control, enhancing the mechanical structural strength of the DFIG. It synchronously tracks the generator's excitation winding voltage to achieve power control during grid-connected operation, exhibiting excellent dynamic control performance and high / low voltage ride-through capabilities. The algorithm used in this invention eliminates frequency-locked and phase-locked loop (PLL) components, preventing frequency fluctuations in the grid voltage and power fluctuations caused by the PLL tracking phase. Therefore, it effectively improves the safety, stability, and reliability of the DFIG operation. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart of a doubly-fed wind turbine grid connection and direct vector power control method according to an embodiment of the present invention;

[0040] Figure 2 This is a control principle diagram of a sensorless doubly-fed wind turbine generator system according to an embodiment of the present invention;

[0041] Figure 3 ΔU is an embodiment of the present invention. f Simulation waveform of reactive current control when >0;

[0042] Figure 4 ΔU is an embodiment of the present invention. f Simulation waveform of reactive current control with time lag <0;

[0043] Figure 5 In this embodiment of the invention, the phase control function controls the output modulated wave voltage phase to lead the input voltage phase.

[0044] Figure 6 In this embodiment of the invention, the phase control function controls the output modulated wave voltage phase to lag behind the input voltage phase. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] To address the issues that existing doubly-fed induction generator (DFIG) wind power systems require the installation of speed sensors, which reduces the system's mechanical strength, and that wind turbine grid connection control requires tracking the grid voltage, the time difference between tracking and grid connection leads to current surges during grid connection, and that the generator's grid connection and operation require tracking the grid voltage frequency and phase, the main technology being phase-locked loop (PLL) control algorithms, is a major cause of low-frequency oscillations in the power system, and also requires algorithms to meet low-voltage ride-through requirements, this invention proposes a technical solution that eliminates the need for speed sensors on the DFIG wind power system.

[0048] This embodiment provides a method for grid connection and direct vector power control of a doubly-fed wind turbine, such as... Figure 1 As shown, it includes:

[0049] Start the doubly-fed wind turbine generator, supply DC excitation to the rotor excitation winding, and detect the output voltage frequency of the doubly-fed wind turbine generator;

[0050] Specifically, the wind turbine's mechanical mechanism, namely the prime mover, drives the generator to accelerate its rotation, and the excitation winding is energized with DC current. f ,Depend on Figure 2 Generator output voltage detection unit U l1 The frequency f1 of the three-phase voltage at the generator terminals is determined by equation (1) and the rotational speed n1 of the computer group, where p is the number of pole pairs of the generator.

[0051]

[0052] When it is determined that the output voltage frequency is the same as the grid voltage frequency, the DC excitation is disconnected, and the doubly-fed wind turbine is connected to the grid.

[0053] After grid connection, the voltage of the excitation winding is detected, and the excitation winding is connected in parallel with the excitation power supply.

[0054] The output voltage of the excitation power supply is adjusted to control the reactive current and active current of the doubly-fed wind turbine generator connected to the grid.

[0055] Specifically, this embodiment utilizes the technology of tracking the excitation winding voltage of a doubly-fed wind turbine, including the excitation winding voltage frequency, phase, and amplitude, to achieve grid-connected operation of a doubly-fed wind turbine without a speed sensor. That is, the reactive current of the generator during grid-connected operation is controlled by adjusting the generator output voltage amplitude, and the active current is controlled by adjusting the phase of the excitation power supply output voltage to control the phase difference between the generator output voltage and the grid voltage.

[0056] Further optimization, determining that the output voltage frequency is the same as the grid voltage frequency includes:

[0057] Obtain the phase sequence of the doubly-fed wind turbine generator and the phase sequence of the grid voltage;

[0058] Calculate the generator speed based on the output voltage frequency;

[0059] When the phase sequence of the doubly fed wind turbine is the same as the phase sequence of the grid voltage, and the generator speed reaches the synchronous speed, the output voltage frequency is the same as the grid voltage frequency.

[0060] Specifically, when the generator unit starts and the rotor speed approaches the synchronous speed, the excitation current i is gradually reduced. f After reaching zero, the excitation is disconnected, and the generator voltage and current detection unit detects its terminal voltage u. l1 When the generator and grid voltage phase sequence are the same, the generator is connected to the grid without excitation. Since the generator rotor rotates synchronously with the air gap magnetic field, the voltage of the excitation winding on the rotor is zero or close to the synchronous speed during the grid connection process. The voltage generated on the excitation winding is very small.

[0061] Further optimized, after grid connection, the excitation power supply is connected, the voltage of the excitation winding is detected, and the output voltage of the excitation power supply is adjusted using the voltage of the excitation winding.

[0062] Connect the excitation power supply and detect the excitation winding voltage of the doubly fed wind turbine after grid connection;

[0063] Calculate the frequency, amplitude, and phase of the excitation winding voltage, and use the frequency, amplitude, and phase to control the output voltage of the excitation power supply so that the frequency, amplitude, and phase of the excitation winding voltage are the same as the frequency, amplitude, and phase of the output voltage of the excitation power supply.

[0064] Specifically, after the generator is connected to the grid, to maintain the stability of the wind power generation system and the power grid, the output voltage of the excitation power supply must be synchronized with the excitation winding voltage. The excitation winding voltage u is then monitored after the generator is connected to the grid. f That is, at the grid voltage u G After connection, and with the generator speed not equal to the synchronous speed, the stator current i l1 Under the influence of a circular rotating magnetic field formed in the generator air gap, the excitation winding generates a voltage, and the frequency f of this voltage is calculated. r Amplitude U rm and phase As the modulation wave of the excitation power converter, it controls the output voltage of the excitation power supply to be in the same frequency, amplitude and phase as the voltage generated by the air gap magnetic field in the excitation winding. By connecting the excitation power supply, the output voltage of the excitation power supply and the voltage generated by the excitation winding are synchronously tracked. Thus, the magnetic field formed by the excitation current is strictly synchronized with the air gap magnetic field generated by the stator winding current, and the excitation power supply and excitation winding are connected in parallel, providing the basic conditions for subsequent reactive current control and active current control.

[0065] Further optimized, adjusting the output voltage of the excitation power supply for grid-connected reactive current control of the doubly-fed wind turbine includes:

[0066] Obtain the output current of the doubly fed wind turbine after grid connection;

[0067] Calculate the reactive current based on the output current;

[0068] The system's setpoint reactive current is preset to the reactive current closed-loop control unit.

[0069] Calculate the excitation power supply output voltage setpoint coefficient by combining the reactive current and the system given reactive current;

[0070] The amplitude of the excitation power supply output voltage is adjusted based on the given coefficient of the excitation power supply output voltage to control the reactive current.

[0071] Specifically, after the generator is connected to the grid, the output voltage amplitude U of the excitation power supply is controlled. rmf To adjust the excitation current i f The generator current detection unit i l1 To determine whether the generator output voltage is the same as the grid voltage, the condition is that the calculated generator current approaches zero; from Figure 2 The system reactive current reference i of the reactive current closed-loop control unit Qref The reactive current i calculated from the generator output current is obtained by detecting the generator output current. Q1 In comparison, the reactive current controller utilizes the system reactive current given i Qref and reactive current i Q1 After subtraction, the excitation power supply output voltage setpoint coefficient k is obtained through coefficient adjustment calculation. Qref The excitation power supply output voltage is given by a coefficient k. Qref Adjusting the amplitude of the generator output voltage, that is, setting the excitation power supply output voltage by the setpoint coefficient k. Qref The amplitude of the excitation winding voltage signal is multiplied by the amplitude of the excitation power supply output voltage to control the generator output voltage, thereby adjusting the reactive current control. When the generator output voltage is higher than the grid voltage, i.e., ΔU f >0, the generator outputs leading reactive current, such as Figure 3 As shown; when the generator output voltage is lower than the grid voltage, i.e., ΔU f <0, the generator outputs lagging reactive current, such as Figure 4 As shown, where ΔU f This is the difference between the output voltage of the excitation power converter and the voltage of the excitation winding.

[0072] The specific active and reactive currents are calculated from the feedback three-phase currents as follows:

[0073] The feedback three-phase current is calculated as shown in equation (2):

[0074]

[0075] Among them, i a i b i c For three-phase current, ω is angular velocity, t is time, and I is... m The current amplitude, The power factor angle.

[0076] Specifically, the reactive current for one-quarter of a cycle is calculated using the feedback current from equation (2) as follows: When When calculating, use the currents of phase A and phase C.

[0077] when i a +2i c When ≠0, find:

[0078]

[0079]

[0080] Where β is the intermediate value used in the calculation.

[0081] when When calculating, use the currents of phase B and phase C.

[0082] when i b +2i c When ≠0, find:

[0083]

[0084]

[0085]

[0086] The specific θ is calculated from the generator output voltage using the following method:

[0087]

[0088] Among them, u a u b u c For three-phase voltage, U m This represents the voltage amplitude. When... When calculating, use the voltages of phase A and phase C.

[0089] When u a +2u c When ≠0, find:

[0090]

[0091] when When calculating, use the voltages of phase B and phase C.

[0092] When u b +2u c When ≠0, find:

[0093]

[0094] Then the reactive current can be obtained:

[0095]

[0096] Further optimized, the active current control of the doubly-fed wind turbine generator grid connection by adjusting the excitation power supply output voltage includes:

[0097] Obtain the output current of the doubly fed wind turbine after grid connection;

[0098] Calculate the active current based on the output current;

[0099] Based on the active current and the given active current of the system, calculate the phase reference δ of the excitation power supply output voltage. f ;

[0100] Based on the phase of the excitation power supply output voltage, given δ f Control the output voltage phase of the doubly-fed wind turbine generator and determine that the output voltage phase leads the grid voltage phase;

[0101] A phase control function is constructed, and the output voltage phase of the doubly-fed wind turbine is adjusted based on the phase control function, thereby adjusting the active current.

[0102] Specifically, the active current control of a doubly-fed wind turbine connected to the grid: after the generator is connected to the grid, the active current is controlled by... Figure 2 The active current given i in the system with active current closed-loop control unit Pref The active current i is calculated by detecting the generator output current. P1 The active current controller utilizes the system active current given i Pref and active current i P1 After subtraction, the active current controller uses equation (16) to calculate the phase setpoint (lead angle) δ of the output excitation power supply. f Active current control is achieved by controlling the phase of the generator output voltage, ensuring that the phase leads the grid voltage phase. The constructed phase control function adjusts the excitation power supply output voltage phase to either lead or lag, thereby controlling the generator output voltage phase and ultimately regulating the active current. Specifically, the acquired excitation winding voltage signal is used as the input signal u to the phase control function.i The voltage signal u output after being controlled by the phase control function (13) o Generates a phase difference (lead angle) δ with the input voltage signal. f One of the purposes of regulation is to control the unit speed in order to find the optimal wind-capturing operating point according to system control, that is, to detect the rotor operating speed of the doubly-fed wind turbine after grid connection.

[0103] The specific active current is calculated from the feedback three-phase current as follows:

[0104] Similarly, the active current of the feedback three-phase current can be calculated from equations (3) to (10) used in calculating the reactive current, as shown in equation (12):

[0105]

[0106] Among them, i P1 For active current, I m The current amplitude, The power factor angle.

[0107] The specific function for increasing the output voltage phase of the power converter to lead the grid voltage phase is constructed as shown in equation (13). By introducing an integral element, the following phase control function with leading power angle is constructed. The purpose is to reduce the rotor operating speed n of the unit.

[0108]

[0109] τ RC =R c C p (14)

[0110]

[0111] Among them, u o (s) is the output voltage signal of the phase control function, u i (s) is the input voltage signal for the phase control function, R c and C p It is a virtual parameter, Kδ C τ is the gain compensation coefficient for the advance angle control signal. RC X is a time constant. cp Let s be the virtual capacitive reactance and s be the frequency domain operator.

[0112] Figure 5 The phase control function of equation (13) results in a curve showing the phase relationship between the output voltage and the input signal voltage. The lead angle δ is... f The calculation is determined by equation (16).

[0113]

[0114] The specific function for reducing the output voltage phase of the power converter from leading the grid voltage phase is constructed as shown in equation (17). A lag inertial element is introduced, and the following power angle lag control function is constructed. The purpose is to increase the unit speed n.

[0115]

[0116] Among them, u o (s) is the output voltage signal of the phase control function, u i (s) is the input voltage signal for the phase control function, R l and L p It is a virtual parameter, K δL Defined as the gain compensation coefficient for the lag angle control signal, τ RL Let be the time constant and s be the frequency domain operator.

[0117]

[0118] Among them, X Lp For virtual sensory resistance.

[0119] Figure 6 The phase control function of equation (17) makes the output voltage lag phase relationship curve with the input signal voltage, and the power angle is determined by equation (20).

[0120]

[0121] Further optimized, the method also includes: detecting the rotor operating speed of the doubly-fed wind turbine after grid connection, including:

[0122] Obtain the excitation winding voltage frequency and the doubly-fed wind turbine output voltage frequency;

[0123] The rotor operating speed is calculated based on the excitation winding voltage frequency and the doubly fed wind turbine output voltage frequency.

[0124] Specifically, rotor speed detection during the operation of a doubly-fed wind turbine system: After the generator is connected to the grid, the excitation winding voltage frequency f is detected. r And the generator output voltage frequency f1, and the computer group operating speed n.

[0125]

[0126] This invention utilizes technology that tracks the frequency, phase, and amplitude of the excitation winding voltage of a doubly-fed induction generator (DFIG) to achieve sensorless grid-connected operation of the DFIG. Specifically, it controls the reactive current during grid-connected operation by adjusting the generator's output voltage amplitude and controls the phase difference between the generator's output voltage and the grid voltage by adjusting the excitation power supply's output voltage phase, thereby controlling the active current. This invention combines the operating principle of DFIGs with the advantages of sensorless grid-connected operation and power control, enhancing the mechanical structural strength of the DFIG. It synchronously tracks the generator's excitation winding voltage to achieve power control during grid-connected operation, exhibiting excellent dynamic control performance and high / low voltage ride-through capabilities. The algorithm used in this invention eliminates frequency-locked and phase-locked loop (PLL) components, preventing frequency fluctuations in the grid voltage and power fluctuations caused by the PLL tracking phase. Therefore, it effectively improves the safety, stability, and reliability of the DFIG operation.

[0127] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for grid connection and direct vector power control of a doubly-fed wind turbine, characterized in that, include: Start the doubly-fed wind turbine generator, supply DC excitation to the rotor excitation winding, and detect the output voltage frequency of the doubly-fed wind turbine generator; When it is determined that the output voltage frequency is the same as the grid voltage frequency, the DC excitation is disconnected, and the doubly-fed wind turbine is connected to the grid. After grid connection, the excitation power supply is connected, the voltage of the excitation winding is detected, and the output voltage of the excitation power supply is adjusted using the voltage of the excitation winding. The output voltage of the excitation power supply is adjusted to control the reactive current and active current of the doubly-fed wind turbine generator connected to the grid.

2. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 1, characterized in that, Determining that the output voltage frequency is the same as the mains voltage frequency includes: Obtain the phase sequence of the doubly-fed wind turbine generator and the phase sequence of the grid voltage; Calculate the generator speed based on the output voltage frequency; When the phase sequence of the doubly fed wind turbine is the same as the phase sequence of the grid voltage, and the generator speed reaches the synchronous speed, the output voltage frequency is the same as the grid voltage frequency.

3. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 1, characterized in that, After grid connection, the excitation power supply is connected, the voltage of the excitation winding is detected, and the output voltage of the excitation power supply is adjusted using the voltage of the excitation winding, including: Connect the excitation power supply and detect the excitation winding voltage of the doubly fed wind turbine after grid connection; Calculate the frequency, amplitude, and phase of the excitation winding voltage, and use the frequency, amplitude, and phase to modulate the excitation power supply output voltage so that the frequency, amplitude, and phase of the excitation winding voltage are the same as the frequency, amplitude, and phase of the excitation power supply output voltage.

4. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 1 or 3, characterized in that, Adjusting the output voltage of the excitation power supply for grid-connected reactive current control of the doubly-fed wind turbine includes: Obtain the output current of the doubly fed wind turbine after grid connection; Calculate the reactive current based on the output current; The system's setpoint reactive current is preset to the reactive current closed-loop control unit. Calculate the excitation power supply output voltage setpoint coefficient by combining the reactive current and the given reactive current of the system; The amplitude of the excitation power supply output voltage is adjusted based on the given coefficient of the excitation power supply output voltage to control the reactive current.

5. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 1, characterized in that, Adjusting the output voltage of the excitation power supply for grid-connected active current control of the doubly-fed wind turbine includes: Obtain the output current of the doubly fed wind turbine after grid connection; Calculate the active current based on the output current; Based on the active current and the system given active current, calculate the phase setting of the excitation power supply output voltage; The output voltage phase of the doubly-fed wind turbine is controlled based on the phase of the excitation power supply output voltage, and it is determined that the output voltage phase leads the grid voltage phase. A phase control function is constructed, and the output voltage phase of the doubly-fed wind turbine is adjusted based on the phase control function, thereby adjusting the active current.

6. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 5, characterized in that, The phase control function is: Among them, u o (s) is the output voltage signal of the phase control function, u i (s) is the input voltage signal for the phase control function, s is the frequency domain operator, and K δC τ is the gain compensation coefficient for the advance angle control signal. RC is the time constant.

7. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 1, characterized in that, The method further includes: detecting the rotor operating speed of the doubly fed wind turbine after grid connection.

8. The method for grid connection and direct vector power control of a doubly-fed wind turbine generator according to claim 7, characterized in that, The rotor operating speed of the doubly-fed wind turbine generator after grid connection is detected, including: Obtain the excitation winding voltage frequency and the doubly-fed wind turbine output voltage frequency; The rotor operating speed is calculated based on the excitation winding voltage frequency and the doubly fed wind turbine output voltage frequency.

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