Double-fed wind generator system motor side converter control method, module and device

Abstract

This invention discloses a control method, module, and device for a motor-side converter in a doubly-fed induction generator (DFIG) wind turbine system. The method includes: when controlling the motor-side converter, for control quantities other than those used to control the motor's d-axis, a voltage-source grid-connected inverter control method is used to generate them. The control quantities used to control the motor's d-axis, specifically the control quantity for the rotor voltage d-axis, are generated using a current-source control method, thus forming a combined voltage-source and current-source control method to control the motor-side converter. This invention has advantages such as simple implementation, high stability and reliability, frequency support characteristics, and rapid response.

Description

Technical Field

[0001] This invention relates to the field of doubly-fed wind turbine generator system technology, and in particular to a control method, module and device for the motor-side converter of a doubly-fed wind turbine generator system. Background Technology

[0002] As the penetration rate of new energy power generation equipment in the power grid gradually increases, the power grid is increasingly exhibiting characteristics of a weak grid, including high impedance, low inertia, weak damping, and low short-circuit ratio. Doubly fed wind power systems, such as... Figure 1 As shown, its stator winding is directly connected to the power grid, while the rotor winding is connected to the power grid through a converter. The frequency, voltage, amplitude, and phase of the rotor winding power supply are automatically adjusted by the frequency converter according to operating requirements. The unit can achieve constant frequency power generation at different speeds to meet the requirements of the power load and grid connection. Due to the use of AC excitation, the generator and the power system form a "flexible connection," meaning that the excitation current can be adjusted according to the grid voltage, current, and generator speed to precisely regulate the generator output current and ensure it meets the requirements.

[0003] The performance of a doubly-fed induction generator (DFIG) wind turbine system primarily depends on the control performance of the generator-side converter. Currently, the control of the generator-side converter typically employs a stator voltage-oriented vector control strategy, i.e., a current-source control method. The current-source control method is as follows... Figure 2 As shown, where i rd* For the rotor d-axis reference current, i rq* For the rotor q-axis reference current, θ Let 's' be the grid phase-locked angle. Stator voltage orientation uses a phase-locked loop (PLL), aligning the axis of the synchronous rotating coordinate system with the stator voltage vector. The clockwise rotation direction is the axis direction, and the internal coordinate system rotates at the same speed as the voltage vector. This current-source control strategy relies on the PLL maintaining synchronization with the grid. Therefore, when grid disturbances occur, they affect the stator voltage and current output through the PLL, thus impacting system stability. In actual operation, grids with a high proportion of renewable energy generation have repeatedly experienced converter disconnection due to subsynchronous oscillations. The current-source control method, lacking the ability to actively support the grid's frequency and voltage, poses a significant risk to the stable operation of both the grid and the current transformer itself. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a control method, module and device for the motor side converter of a doubly fed wind turbine generator system that is simple to implement, stable and reliable, has frequency support characteristics and can respond quickly.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for controlling a motor-side converter in a doubly-fed wind turbine generator system includes: when controlling the converter on the motor side, for control quantities other than those used to control the motor's d-axis, a voltage source-type grid-connected inverter control method is used to generate them; the control quantities used to control the motor's d-axis, including the control quantities for the rotor voltage d-axis, are generated using a current source-type control method, thereby forming a combined voltage source-type and current source-type control method to control the converter on the motor side.

[0006] Furthermore, in the voltage source type grid-connected inverter control mode, the outer control loop adopts virtual synchronous control to simulate the motor characteristics of a synchronous motor and obtain the stator side angle reference signal.

[0007] Furthermore, in the virtual synchronization control, only active virtual synchronization control is performed, and reactive droop control is not performed.

[0008] Furthermore, during the virtual synchronization control, the network voltage is first determined... u ABC and stator current i ABC The current active power is calculated. P e According to the active power P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s The virtual synchronization controller only performs active virtual synchronization control and does not perform reactive droop control.

[0009] Furthermore, in the voltage source type grid-connected inverter control method, after the outer control loop adopts virtual synchronous control, it also includes obtaining the control components of the grid voltage dq axis and the rotor current dq axis based on the grid voltage signal, the rotor current signal and the stator side angle reference signal obtained by the virtual synchronous control.

[0010] Furthermore, based on the mains voltage signal and the stator side angle reference signal, the control component of the mains voltage dq axis is obtained through 3s / 2r transformation, and based on the rotor current signal and the stator side angle reference signal, the control component of the rotor current dq axis is obtained through 3s / 2r transformation.

[0011] Furthermore, in the voltage source type grid-connected inverter control mode, generating the control quantity on the rotor voltage d-axis in the control inner loop according to the current source type control mode includes: setting the d-axis current parameter... i rd * and the d-axis component of the rotor current ird PI control is performed to obtain the control quantity of the rotor voltage d-axis.

[0012] Furthermore, in the voltage source type grid-connected inverter control mode, the control quantity of the rotor current q-axis is generated in the control inner loop according to the control component of the grid voltage q-axis, the control component of the rotor current q-axis, and the q-axis current feedforward signal.

[0013] Furthermore, the control quantity for generating the rotor current q-axis includes: using the q-axis voltage reference signal. u sq * Control component signal of the q-axis of the grid voltage u sq PI control is performed to obtain a current reference signal, which is then added to the current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis.

[0014] Furthermore, in the voltage source type grid-connected inverter control method, after the control inner loop generates the control quantity of the rotor voltage d-axis and the control quantity of the rotor current q-axis, it also includes transforming the control quantity of the rotor voltage d-axis and the control quantity of the rotor current q-axis to obtain a voltage reference value, and driving the inverter according to the voltage reference value to generate a rotor current value output to the rotor to complete the closed-loop control.

[0015] A method for controlling the motor-side converter of a doubly-fed wind turbine system, comprising the following steps: Control the motor-side converter according to the above control method; When a low-voltage ride-through is detected in the power grid, the current source control method is switched to control the motor-side converter.

[0016] Furthermore, specifically when the motor starts, a current source control method is first used to control the motor-side converter; When it is determined that the motor has entered the preset operating condition, the control switch controls the motor-side converter according to the control method described above.

[0017] Furthermore, it also includes switching back to controlling the motor-side converter according to the above control method when it is determined that the power grid has recovered from a low-voltage ride-through to a normal state.

[0018] Furthermore, when it is determined that a low-voltage ride-through has occurred in the power grid and cannot be recovered, the system determines that the current state is in a fault state and controls the sending of corresponding preset alarm information.

[0019] Furthermore, a control module for the motor-side converter of a doubly-fed wind turbine system includes an outer control loop and an inner control loop. The outer control loop includes a virtual synchronization unit for simulating the rotational inertia and frequency droop characteristics of a synchronous motor using virtual synchronization control. The inner control loop includes an interconnected dq-axis control quantity generation unit and a conversion unit. The dq-axis control quantity generation unit generates q-axis control quantity using a voltage source grid-connected inverter control method and generates d-axis control quantity for the rotor voltage using a current source control method. The conversion unit then generates a voltage reference value output.

[0020] Furthermore, the virtual synchronization unit is a virtual synchronization controller that only performs active power virtual synchronization control and does not perform reactive power droop control, and is used to control the active power... P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s .

[0021] Furthermore, the dq axis control quantity generation unit includes: The 3s / 2r subunit is used to obtain the control component of the grid voltage dq axis by performing a 3s / 2r transformation based on the grid voltage signal and the stator side angle reference signal, and to obtain the control component of the rotor current dq axis by performing a 3s / 2r transformation based on the rotor current signal and the stator side angle reference signal. The q-axis control signal generation subunit is used to generate the q-axis voltage reference signal. u sq * Control component signal of the q-axis of the grid voltage u sq PI control is performed to obtain a current reference signal, which is then added to the current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis; The d-axis control quantity generation subunit is used to generate d-axis current parameters. i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the control quantity of the rotor voltage d-axis. Furthermore, the system also includes a PWM unit connected to the conversion unit, used to generate a drive signal based on the voltage reference value, thereby driving the inverter unit to generate a rotor current value output to the rotor.

[0022] A doubly fed wind turbine system motor-side converter control module includes a processor and a memory. The memory stores a computer program, and the processor executes the computer program to perform the method described above.

[0023] A control device for the motor-side converter of a doubly-fed wind turbine system includes: The above-mentioned doubly fed wind turbine system uses a motor-side converter control module. The second control module is used to control the motor-side converter using a current source control method. The switching control module is used to control the switching of the first control module or the second control module to control the motor-side converter.

[0024] Furthermore, the second control module is a current source controller with a phase-locked loop, which controls the generation of a stator-side angle reference signal and provides it to the current source controller.

[0025] Furthermore, when the switching control module determines that the motor has entered a preset operating condition and / or a low-voltage ride-through has occurred in the power grid, it controls the activation of the first control module.

[0026] Furthermore, the output of the switching control module is also equipped with a PWM module, which is used to generate a drive signal based on the voltage reference values ​​generated by the first control module and the second control module, so as to drive the inverter unit to generate a rotor current value and output it to the rotor.

[0027] Compared with the prior art, the advantages of the present invention are as follows: 1. This invention eliminates the phase-locked loop by adopting a voltage source control method in the main body to control the generator-side converter. It can well adapt to the requirements of weak power grids with high impedance, low inertia, weak damping, and low short-circuit ratio, actively providing frequency and voltage support, and effectively improving the stability of the grid-connected inverter. At the same time, a current source control method is used when controlling the control quantity of the motor d-axis, forming a combined voltage source and current source control method to control the generator-side converter. This allows the advantages of both voltage source grid-connected inverter control and current source control methods to be fully utilized, improving the response speed of active and reactive power while ensuring stability and reliability.

[0028] 2. This invention combines voltage source control with current source control on the generator-side converter. It directly uses current source control in the d-axis voltage loop and further adds current feedforward in the q-axis current loop, enabling rapid response to the system's active power demand and further improving the system's response speed.

[0029] 3. The present invention further controls the motor-side converter by first controlling it according to the voltage source control method. When it is determined that a low voltage ride-through occurs in the power grid, it switches to the current source control method to control the motor-side converter. This can ensure the control performance of the motor-side converter under the low voltage ride-through state, thereby ensuring that the converter can achieve optimal control performance in all states. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structural principle of a doubly fed wind power generation system.

[0031] Figure 2 This is a schematic diagram illustrating the implementation principle of the current source control method.

[0032] Figure 3 This is a schematic diagram illustrating the implementation principle of the motor-side converter control method for a doubly fed wind turbine generator system according to Embodiment 1 of the present invention.

[0033] Figure 4 This is a schematic diagram of the implementation process of virtual synchronization control in Embodiment 1 of the present invention.

[0034] Figure 5 This is a schematic diagram of the structure and principle of the virtual synchronization controller in Embodiment 1 of the present invention.

[0035] Figure 6 This is a schematic diagram of the structural principle of the outer ring generating the dq axis control component in Embodiment 1 of the present invention.

[0036] Figure 7 This is a schematic diagram of the structural principle of the inner ring dq axis control in Embodiment 1 of the present invention.

[0037] Figure 8 This is a schematic diagram of the inner loop control SVPWM structure in Embodiment 1 of the present invention.

[0038] Figure 9 This is a schematic diagram illustrating the implementation principle of the doubly fed wind turbine generator system motor-side converter control method in embodiments 2 and 3 of the present invention.

[0039] Figure 10 This is a detailed flowchart illustrating the control of the motor-side converter in the doubly fed wind turbine system as described in embodiments 2 and 3 of the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0041] Example 1: like Figure 3As shown in this embodiment, the control method for the motor-side converter of the doubly fed wind turbine generator system includes: when controlling the converter on the motor side, for control quantities other than those used to control the motor d-axis, a voltage source grid-connected inverter control method is used to generate them; the control quantities used to control the motor d-axis, including the control quantities for the rotor voltage d-axis, are generated according to a current source control method, so as to form a control method that combines voltage source and current source to control the converter on the motor side.

[0042] Voltage-source grid-connected inverters eliminate the PLL (phase-locked loop) in the grid-connected inverter control, adopting a self-synchronization method while simulating the characteristics of a synchronous motor to actively provide frequency and voltage support. This embodiment uses a voltage-source control method to eliminate the PLL, achieving control of the generator-side converter. This effectively adapts to the needs of weak grids with high impedance, low inertia, weak damping, and low short-circuit ratios. The self-synchronization method simulates the characteristics of a synchronous motor, actively providing frequency and voltage support, effectively improving the stability of the grid-connected inverter. Simultaneously, a current-source control method is used when controlling the d-axis of the generator motor, forming a combined voltage-source and current-source control approach for the generator-side converter. This fully leverages the advantages of both voltage-source and current-source control methods, ensuring stability and reliability while improving active and reactive power response speed. This allows for rapid response to the system's active power demand, effectively enhancing the generator-side control performance of the doubly-fed induction generator (DFIG) and optimizing the weak grid environment.

[0043] In this embodiment, in the voltage source type grid-connected inverter control method, the outer control loop specifically adopts virtual synchronous control to simulate the motor characteristics (rotational inertia and frequency droop characteristics, etc.) of a synchronous motor, obtaining a stator-side angle reference signal. By simulating the electrical characteristics of an actual synchronous generator using virtual synchronous control, the grid-connected inverter can possess the ability to actively regulate frequency and voltage.

[0044] like Figure 4 As shown, in this embodiment of virtual synchronization control, the network voltage is first determined... u ABC and stator current i ABC The current active power is calculated. P e According to active power P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s The virtual synchronous controller only performs active virtual synchronous control and does not perform reactive droop control.

[0045] The virtual synchronization controller used in this embodiment is as follows: Figure 5 As shown, where Kω This is the frequency adjustment factor. J For virtual rotational inertia, D Virtual damping coefficient, P ref For useful reference, ω 0 is the frequency reference. P e For active power feedback, the aforementioned virtual synchronous controller can simulate the rotational inertia and frequency droop characteristics of a synchronous motor. Furthermore, since only active power virtual synchronous control is performed and reactive power droop control is not performed, the system's response speed to reactive power can be further improved.

[0046] Understandably, the specific implementation structure of virtual synchronization control can also adopt other structures according to actual needs.

[0047] In this embodiment of the voltage source type grid-connected inverter control method, after the outer loop adopts virtual synchronous control, it also includes obtaining the control components of the grid voltage dq axis and the rotor current dq axis based on the grid voltage signal, the rotor current signal, and the stator side angle reference signal obtained from the virtual synchronous control. Specifically, this embodiment obtains the grid voltage dq axis control component through a 3s / 2r transformation based on the grid voltage signal and the stator side angle reference signal, and obtains the rotor current dq axis control component through a 3s / 2r transformation based on the rotor current signal and the stator side angle reference signal. For example... Figure 6 As shown, the stator side angle reference is used specifically. θ s and sampling three-phase grid voltage u ABC Rotor three-phase current and rotor angle θ r The dq-axis components of the grid voltage are obtained through 3s / 2r transformation. u sd , u sq and the dq-axis component of the rotor current i rd 、i rq .

[0048] In this embodiment of the voltage source type grid-connected inverter control method, the control quantity of the rotor voltage d-axis is generated in the control inner loop according to the current source type control method, such as... Figure 3 As shown, this specifically includes: setting the d-axis current parameters i rd * and the d-axis component of the rotor current i rdPI control is performed to obtain the control quantity of the rotor voltage d-axis. By adopting voltage source control for the machine-side converter and directly using current source control in the d-axis voltage loop, the advantages of current source control can be leveraged to improve the active power response speed of the system.

[0049] In this embodiment of the voltage source grid-connected inverter control method, the inner control loop also includes a control quantity for generating the rotor current q-axis based on the grid voltage q-axis control component, the rotor current q-axis control component, and the q-axis current feedforward signal. This embodiment adds current feedforward to the q-axis current loop based on the voltage source control method for the generator-side converter. i rq * This allows the advantages of current source control to be leveraged, enabling rapid response to the system's active power demand and further improving the system's response speed.

[0050] In this embodiment, the control quantity for generating the rotor current q-axis includes: the q-axis voltage reference signal. u sq * Control component signal of the q-axis of the grid voltage u sq PI control is performed to obtain a current reference signal, which is then added to the current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis.

[0051] like Figure 7 As shown, in this embodiment, d-axis control is directly determined by the d-axis current parameters. i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the rotor voltage d-axis control quantity. u rd * For q-axis control, specifically the q-axis voltage reference signal... u sq * Set to 0, and set the q-axis voltage reference signal. u sq * Control component of the q-axis of the grid pressure u sq The current reference signal is obtained after PI control, and then fed into the current feedforward. i rq * The q-axis control quantity is then obtained by adjusting the current PI control. u rq* Finally, the voltage reference value is obtained through a 2r / 3s transformation. u abc * .

[0052] This embodiment adopts a dual closed-loop control method of voltage and current in the inner control loop. By directly using the current source control method for the d-axis control and adding current feedforward control for the q-axis control, it can fully integrate the advantages of voltage current source and voltage source control. While ensuring stability and reliability, it improves the active power response speed, so that it has the frequency support characteristics of voltage source control and the fast active and reactive power response capability of current source control.

[0053] It is understandable that the d-axis control, q-axis control, PWM control, etc. in the above-mentioned control inner loop can of course adopt other control methods according to actual needs.

[0054] In this embodiment of the voltage source type grid-connected inverter control method, after the control inner loop generates the control quantities for the rotor voltage d-axis and rotor current q-axis, it also includes transforming the control quantities for the rotor voltage d-axis and rotor current q-axis to obtain a voltage reference value. Based on the voltage reference value, the three-phase inverter is driven to generate a rotor current value output to the rotor to complete the closed-loop control. For example... Figure 8 As shown, this embodiment specifically utilizes the voltage reference value uabc* to drive the three-phase inverter using SVPWM to complete closed-loop control.

[0055] The detailed control process implemented in this embodiment using the above-described doubly-fed wind turbine system motor-side converter control method is as follows: Step 1: Using network voltage u ABC and stator current i ABC The current active power is calculated. P e Then, the stator side angle reference is obtained through virtual synchronous calculation. θ s .

[0056] Step 2: Using the stator side angle reference θ s and sampling three-phase grid voltage u ABC Rotor three-phase current and rotor angle θ r The dq-axis control components of the mains voltage are obtained through 3s / 2r transformation. u sd , u sq and the dq-axis component of the rotor current i rd、i rq .

[0057] Step 3: In the inner control loop, for d-axis control, it is directly determined by the d-axis current parameters. i rd * and the d-axis component of the rotor current i rd Perform PI control to obtain the rotor voltage d-axis control quantity. u rd * For q-axis control, the q-axis voltage reference signal u sq * Set to 0, and correlate with the control component of the q-axis of the mains voltage. u sq After performing PI control, a current reference signal is obtained, which is then added to the q-axis current feedforward signal. i rq * The q-axis control quantity is then obtained by adjusting the current PI control. u rq * Finally, the voltage reference value is obtained through a 2r / 3s transformation. u abc * .

[0058] Step 4: Utilize u abc *The three-phase inverter is driven using SVPWM to generate the rotor current value. i abc This completes closed-loop control.

[0059] This embodiment also provides a doubly-fed wind turbine system motor-side converter control module, such as... Figure 3 As shown, the system includes an outer control loop and an inner control loop. The outer control loop includes a virtual synchronization unit for simulating the rotational inertia and frequency droop characteristics of a synchronous motor using virtual synchronous control. The inner control loop includes a dq-axis control quantity generation unit, a conversion unit, a PWM unit, and an inverter unit connected in sequence. The dq-axis control quantity is input to the dq-axis current and voltage parameters. The conversion unit generates a voltage reference value and outputs it to the PWM unit. The PWM unit drives the inverter unit according to the voltage reference value to generate a rotor current value and output it to the rotor to complete the closed-loop control.

[0060] In this embodiment, the virtual synchronization unit is as follows: Figure 4 As shown, it specifically includes a power calculation subunit and a virtual synchronization controller, wherein the virtual synchronization controller is as follows: Figure 5 As shown.

[0061] In this embodiment, the outer control loop also includes two 3s / 2r transformation units, which are used to connect to the stator-side angle reference respectively. θ s and sampling three-phase grid voltage u ABC Rotor three-phase current and rotor angle θ r The dq-axis control components of the mains voltage are obtained through 3s / 2r transformation. u sd , u sq and the dq-axis component of the rotor current i rd 、i rq ,like Figure 6 As shown.

[0062] In this embodiment, the dq axis control quantity generation unit in the inner loop is as follows: Figure 7 As shown, it includes three multipliers, two PI controllers, and a / 2r3s converter subunit. For d-axis control, it directly uses the d-axis current parameter. i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the rotor voltage d-axis control quantity. u rd * For q-axis control, the q-axis voltage reference is specifically... u sq * Set to 0, and set the q-axis voltage reference. u sq * Control component of the q-axis of the grid pressure u sq The current reference signal is obtained after PI control, and then fed into the current feedforward. i rq * The q-axis control quantity is then obtained by adjusting the current PI control. u rq * Finally, the voltage reference value is obtained through a 2r / 3s transformation. u abc * .

[0063] In this embodiment, the PWM unit in the control inner loop is specifically SVPWM (Space Vector Pulse Modulation), such as... Figure 8 As shown, uabc* is used to drive a three-phase inverter in SVPWM mode to complete closed-loop control.

[0064] The motor-side converter control device of the doubly fed wind turbine system in this embodiment corresponds to the motor-side converter control method of the doubly fed wind turbine system described above, and will not be described in detail here.

[0065] In another embodiment, the motor-side converter control module of the doubly-fed wind turbine system of the present invention may further include a processor and a memory, wherein the memory is used to store a computer program, the processor is used to execute the computer program, and the processor is used to execute the computer program to perform the above-described doubly-fed wind turbine system motor-side converter control method.

[0066] like Figure 3 As shown, the motor-side converter control module of the doubly fed wind turbine system in this embodiment includes an outer control loop and an inner control loop. The outer control loop includes a virtual synchronization unit for simulating the rotational inertia and frequency droop characteristics of a synchronous motor using virtual synchronous control. The inner control loop includes an interconnected dq-axis control quantity generation unit and a conversion unit. The dq-axis control quantity generation unit generates q-axis control quantity using a voltage source grid-connected inverter control method and generates d-axis control quantity for rotor voltage using a current source control method. The conversion unit then generates a voltage reference value output.

[0067] In this embodiment, the virtual synchronization unit is a virtual synchronization controller that only performs active power virtual synchronization control and does not perform reactive power droop control, and is used to adjust the active power... P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s The specific structure of the virtual synchronization controller is as follows: Figure 5 As shown.

[0068] In this embodiment, the dq axis control quantity generation unit includes: The 3s / 2r subunit is used to obtain the control component of the grid voltage dq axis by transforming the grid voltage signal and the stator side angle reference signal through 3s / 2r, and to obtain the control component of the rotor current dq axis by transforming the rotor current signal and the stator side angle reference signal through 3s / 2r. The q-axis control signal generation subunit is used to generate the q-axis voltage reference signal. u sq * Control component signal of the q-axis of the grid voltage u sq PI control is performed to obtain a current reference signal, which is then added to the current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis; The d-axis control quantity generation subunit is used to generate d-axis current parameters.i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the control quantity of the rotor voltage d-axis.

[0069] like Figure 3 As shown, in this embodiment, the 3S / 2R subunit includes two 3S / 2R converters. One is used to obtain the control component of the mains voltage dq axis based on the mains voltage signal and the stator side angle reference signal through 3S / 2R transformation. u sd , u sq A control component for obtaining the dq-axis rotor current based on the rotor current signal and the stator-side angle reference signal through a 3s / 2r transformation. i rd 、i rq The d-axis control quantity generation subunit includes a PI controller, which is directly generated from the d-axis current parameters. i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the rotor voltage d-axis control quantity. u rd * The q-axis control quantity generation subunit includes two PI controllers, which reference the q-axis voltage. u sq * Set to 0, and set the q-axis voltage reference. u sq * Control component of the q-axis of the grid pressure u sq The current reference signal is obtained after PI control, and then fed into the current feedforward. i rq * The q-axis control quantity is then obtained by adjusting the current PI control. u rq * The conversion unit is specifically a 2r / 3s converter, which obtains the voltage reference value through 2r / 3s conversion. u abc * .

[0070] In this embodiment, a PWM unit connected to the conversion unit is also included. This PWM unit generates a drive signal based on a voltage reference value to drive the inverter unit to generate a rotor current value and output it to the rotor. Specifically, the PWM unit is an SVPWM controller that uses uabc* to drive the three-phase inverter in an SVPWM manner to complete closed-loop control.

[0071] The motor-side converter control module of the doubly fed wind turbine system in this embodiment corresponds to the motor-side converter control method of the doubly fed wind turbine system described above, and will not be repeated here.

[0072] Example 2: The steps of the motor-side converter control method for the doubly fed wind turbine system in this embodiment include: The motor-side converter is controlled according to the voltage source control method in Example 1; When a low-voltage ride-through is detected in the power grid, the current source control method is switched to control the motor-side converter.

[0073] The voltage source control method in Example 1 can ensure stable system operation, but when the power grid experiences low-voltage surges, it lacks fault current suppression capabilities. In other words, the control method in Example 1 cannot achieve optimal control performance under low-voltage conditions. Figure 9 As shown, this embodiment monitors the grid voltage status in real time and first controls the motor-side converter according to the voltage source control method in Embodiment 1. When it is determined that the grid has experienced a low voltage ride-through, the current source control method is switched to control the motor-side converter, so that the optimal control performance can still be achieved under the low voltage ride-through state. When the grid voltage recovers, the control method in Embodiment 1 is switched back.

[0074] Considering that using a current source control method with a phase-locked loop can reduce grid current surges, in this embodiment, when the motor starts, the motor-side converter is initially controlled using a current source control method. When it is determined that the motor has entered a preset operating condition, the control switches to control the motor-side converter using the voltage source control method as described in Embodiment 1. Furthermore, when it is determined that the grid has recovered from a low-voltage ride-through to a normal state, the control switches back to the current source control method to control the motor-side converter.

[0075] In specific application embodiments, such as Figure 10 As shown, the detailed flow of the motor-side converter control method for the doubly-fed wind turbine system in this embodiment is as follows: Step S01. When the motor starts, the motor-side converter is first controlled using the current source control method as described in Example 1; Step S02. When it is determined that the motor has entered the preset operating condition, the control switch is used to control the motor-side converter according to the voltage source type control method in Example 1; Step S03. When it is determined that a low voltage ride-through has occurred in the power grid, switch to the current source control mode to control the motor-side converter; Step S04. When it is determined that the power grid has recovered from the low voltage ride-through to the normal state, switch back to the control method of the voltage source type in Example 1 to control the motor-side converter.

[0076] The above-mentioned method involves using a current source control method to control the motor-side converter during the start-up and grid connection of the doubly-fed induction generator (DFIG) to reduce grid current surges. When the motor reaches a preset operating condition (such as stable output), the control switches to the voltage source control method in Example 1 to ensure stable and reliable system operation and improve response speed. When a low-voltage ride-through is detected in the grid, the current source control method is switched to control the motor-side converter. When the grid recovers from the low-voltage ride-through to the normal state, the control method switches back to the voltage source control method in Example 1 to control the motor-side converter. This allows for optimal control across the entire operating range, ensuring that the motor-side current intensity maintains optimal control performance under all operating conditions.

[0077] If a low-voltage ride-through occurs in the power grid and cannot be recovered, it indicates that the current state is faulty and fault handling is required. This also includes determining that the current state is faulty when a low-voltage ride-through occurs in the power grid and cannot be recovered, and controlling the sending of corresponding preset alarm information to prompt timely fault handling, such as shutting down the generator at the same time as the alarm to ensure the safe operation of the generator system.

[0078] This embodiment also provides a control device for the motor-side converter of the doubly-fed wind turbine system, including: The first control module adopts the motor-side converter control module of the doubly fed wind turbine system in Embodiment 1, and is used to control the motor-side converter according to the voltage source type control method in Embodiment 1. The second control module is used to control the motor-side converter using a current source control method. The switching control module is used to control the switching of the first control module or the second control module to control the motor-side converter.

[0079] In this embodiment, the first control module includes an outer control loop and an inner control loop. The outer control loop includes a virtual synchronization unit for simulating the rotational inertia and frequency droop characteristics of a synchronous motor using virtual synchronous control. The inner control loop includes an interconnected dq-axis control quantity generation unit and a conversion unit. The dq-axis control quantity generation unit generates q-axis control quantities using a voltage source-type grid-connected inverter control method and generates d-axis control quantities for the rotor voltage using a current source-type control method. The conversion unit then generates a voltage reference value output. For the specific structure of the first control module, see [link to relevant documentation]. Figure 3 .

[0080] In this embodiment, the virtual synchronization unit is a virtual synchronization controller that only performs active power virtual synchronization control and does not perform reactive power droop control, and is used to adjust the active power... P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s The specific structure of the virtual synchronization controller is as follows: Figure 5 As shown.

[0081] In this embodiment, the dq axis control quantity generation unit includes: The 3s / 2r subunit is used to obtain the control component of the grid voltage dq axis by transforming the grid voltage signal and the stator side angle reference signal through 3s / 2r, and to obtain the control component of the rotor current dq axis by transforming the rotor current signal and the stator side angle reference signal through 3s / 2r. The q-axis control signal generation subunit is used to generate the q-axis voltage reference signal. u sq * Control component signal of the q-axis of the grid voltage u sq PI control is performed to obtain a current reference signal, which is then added to the current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis; The d-axis control quantity generation subunit is used to generate d-axis current parameters. i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the control quantity of the rotor voltage d-axis.

[0082] like Figure 3 As shown, in this embodiment, the 3S / 2R subunit includes two 3S / 2R converters. One is used to obtain the control component of the mains voltage dq axis based on the mains voltage signal and the stator side angle reference signal through 3S / 2R transformation. u sd , u sq A control component for obtaining the dq-axis rotor current based on the rotor current signal and the stator-side angle reference signal through a 3s / 2r transformation. i rd 、i rq The d-axis control quantity generation subunit includes a PI controller, which is directly generated from the d-axis current parameters. i rd * and the d-axis component of the rotor currenti rd PI control is performed to obtain the rotor voltage d-axis control quantity. u rd * The q-axis control quantity generation subunit includes two PI controllers, which reference the q-axis voltage. u sq * Set to 0, and set the q-axis voltage reference signal. u sq * Control component of the q-axis of the grid pressure u sq The current reference signal is obtained after PI control, and then fed into the current feedforward. i rq * The q-axis control quantity is then obtained by adjusting the current PI control. u rq * The conversion unit is specifically a 2r / 3s converter, which obtains the voltage reference value through 2r / 3s conversion. u abc * .

[0083] In this embodiment, the second control module is a current source controller with a phase-locked loop. The phase-locked loop controls the generation of a stator-side angle reference signal, which is provided to the current source controller to achieve current source control.

[0084] In this embodiment, when the switching control module determines that the motor has entered a preset operating condition and / or a low-voltage ride-through has occurred in the power grid, it controls the activation of the first control module, including controlling the activation of the first control module when the motor starts, so as to control the motor-side converter according to the voltage source control method in Embodiment 1; when it determines that a low-voltage ride-through has occurred in the power grid, it switches the control to activate the second control module, so as to switch to the current source control method to control the motor-side converter; when it determines that a low-voltage ride-through has occurred in the power grid and cannot be recovered, it is determined to be in a fault state, and the corresponding preset alarm information is issued. The specific control strategy of the switching control module is shown in Figure 10.

[0085] like Figure 9 As shown, in this embodiment, the output terminal of the switching control module is also equipped with a PWM module, which is used to adjust the voltage reference values ​​generated by the first control module and the second control module. u abc * A drive signal is generated to drive the inverter unit to generate a rotor current value and output it to the rotor.

[0086] The motor-side converter control device of the doubly fed wind turbine system in this embodiment corresponds to the motor-side converter control method of the doubly fed wind turbine system described above, and the switching control module corresponds to the switching control steps described above, which will not be described in detail here.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A control method for the motor-side converter of a doubly-fed wind turbine system, characterized in that, The method includes: when controlling the converter on the motor side, a voltage and current dual closed-loop control mode is adopted in the control inner loop. The control quantity for controlling the motor's d-axis is generated using a current-source control mode for the rotor voltage d-axis. For control quantities other than those for controlling the motor's d-axis, a voltage-source grid-connected inverter control mode is used to generate them, thus forming a combined voltage-source and current-source control mode to control the converter on the motor side. In the voltage-source grid-connected inverter control mode, the control quantity for the rotor current q-axis is generated in the control inner loop based on the grid voltage q-axis control component, the rotor current q-axis control component, and the q-axis current feedforward signal. After generating the control quantities for the rotor voltage d-axis and the rotor current q-axis in the control inner loop, the method further includes transforming the control quantities for the rotor voltage d-axis and the rotor current q-axis to obtain a voltage reference value. The inverter is then driven according to the voltage reference value to generate a rotor current value output to the rotor to complete the closed-loop control.

2. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 1, characterized in that: In the voltage source type grid-connected inverter control mode, the outer control loop adopts virtual synchronous control to simulate the motor characteristics of a synchronous motor and obtain the stator side angle reference signal.

3. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 2, characterized in that: In the virtual synchronization control, only active virtual synchronization control is performed, and reactive droop control is not performed.

4. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 3, characterized in that: During the virtual synchronization control, first, based on the network voltage... u ABC and stator current i ABC The current active power is calculated. P e According to the active power P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s The virtual synchronization controller only performs active virtual synchronization control and does not perform reactive droop control.

5. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 2, characterized in that: In the voltage source type grid-connected inverter control method, after the outer control loop adopts virtual synchronous control, it also includes obtaining the control components of the grid voltage dq axis and the rotor current dq axis based on the grid voltage signal, the rotor current signal and the stator side angle reference signal obtained by the virtual synchronous control.

6. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 5, characterized in that, Based on the mains voltage signal and the stator side angle reference signal, the control component of the mains voltage dq axis is obtained through 3s / 2r transformation. Based on the rotor current signal and the stator side angle reference signal, the control component of the rotor current dq axis is obtained through 3s / 2r transformation.

7. The control method for the motor-side converter of a doubly-fed wind turbine system according to any one of claims 1 to 6, characterized in that, In the voltage source type grid-connected inverter control mode, the control quantity for the rotor voltage d-axis is generated in the control inner loop according to the current source type control mode, including: the d-axis current parameter i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the control quantity of the rotor voltage d-axis.

8. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 7, characterized in that, The control quantity for generating the rotor current q-axis includes: the q-axis voltage reference signal. u sq * With q-axis voltage feedback signal u sq PI control is performed to obtain a current reference signal, which is then added to the q-axis current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis.

9. A control method for the motor-side converter of a doubly-fed wind turbine system, characterized in that the steps are as follows: include: The motor-side converter is controlled according to any one of claims 1 to 8; When a low-voltage ride-through is detected in the power grid, the current source control method is switched to control the motor-side converter.

10. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 9, characterized in that, When the motor starts, the motor-side converter is first controlled using a current source control method. When it is determined that the motor has entered the preset operating condition, the control switch controls the motor-side converter according to the control method described in any one of claims 1 to 8.

11. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 9 or 10, characterized in that, It also includes switching back to the control method described in any one of claims 1 to 8 to control the motor-side converter when it is determined that the power grid has recovered from a low-voltage ride-through to a normal state.

12. The control method for the motor-side converter of a doubly-fed wind turbine system according to claim 9 or 10, characterized in that, It also includes determining that the power grid is in a fault state when it is determined that a low voltage ride-through has occurred and cannot be recovered, and controlling the sending of corresponding preset alarm information.

13. A generator-side converter control module for implementing the method according to any one of claims 1 to 12 in a doubly-fed wind turbine system, characterized in that: It includes an outer control loop and an inner control loop. The outer control loop includes a virtual synchronization unit for simulating the rotational inertia and frequency droop characteristics of a synchronous motor using virtual synchronization control. The inner control loop includes an interconnected dq-axis control quantity generation unit and a conversion unit. The dq-axis control quantity generation unit generates the q-axis control quantity using a voltage source grid-connected inverter control method and generates the d-axis control quantity of the rotor voltage using a current source control method. The conversion unit then generates a voltage reference value output.

14. The doubly-fed wind turbine generator system motor-side converter control module according to claim 13, characterized in that, The virtual synchronization unit is a virtual synchronization controller that performs only active power virtual synchronization control and not reactive power droop control, and is used to control the active power... P e The stator-side angle reference is obtained through a pre-configured virtual synchronous controller. θ s .

15. The doubly-fed wind turbine generator system motor-side converter control module according to claim 13, characterized in that, The dq axis control quantity generation unit includes: The 3s / 2r subunit is used to obtain the control component of the grid voltage dq axis by transforming the grid voltage signal and the stator side angle reference signal through 3s / 2r, and to obtain the control component of the rotor current dq axis by transforming the rotor current signal and the stator side angle reference signal through 3s / 2r. The q-axis control signal generation subunit is used to generate the q-axis voltage reference signal. u sq * With q-axis voltage feedback signal u sq PI control is performed to obtain a current reference signal, which is then added to the q-axis current feedforward signal. i rq * Then, current PI control is performed to obtain the control quantity of the rotor current q-axis; The d-axis control quantity generation subunit is used to generate d-axis current parameters. i rd * and the d-axis component of the rotor current i rd PI control is performed to obtain the control quantity of the rotor voltage d-axis.

16. The doubly-fed wind turbine generator system motor-side converter control module according to claim 13, 14, or 15, characterized in that, It also includes a PWM unit connected to the conversion unit, used to generate a drive signal according to the voltage reference value, so as to drive the inverter unit to generate a rotor current value and output it to the rotor.

17. A control module for the motor-side converter of a doubly-fed wind turbine system, characterized in that, The device includes a processor and a memory, the memory being used to store a computer program and the processor being used to execute the computer program, characterized in that the processor is used to execute the computer program to perform the method as described in any one of claims 1 to 8.

18. A control device for the motor-side converter of a doubly-fed wind turbine system, characterized in that, include: The first control module adopts the control module described in any one of claims 13 to 16; The second control module is used to control the motor-side converter using a current source control method. The switching control module is used to control the switching of the first control module or the second control module to control the motor-side converter.

19. The doubly-fed wind turbine generator system motor-side converter control device according to claim 18, characterized in that, The second control module is a current source controller with a phase-locked loop, which generates a stator-side angle reference signal and provides it to the current source controller.

20. The doubly-fed wind turbine generator system motor-side converter control device according to claim 18 or 19, characterized in that, When the switching control module determines that the motor has entered a preset operating condition and / or the power grid has experienced a low-voltage ride-through, it controls the activation of the first control module.

21. The doubly-fed wind turbine generator system motor-side converter control device according to claim 18 or 19, characterized in that, The output of the switching control module is also equipped with a PWM module, which is used to generate a drive signal based on the voltage reference value generated by the first control module and the second control module, so as to drive the inverter unit to generate a rotor current value and output it to the rotor.

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