A control system and control method for suppressing voltage and current surges during cut-in of a controllable rectifier of a permanent magnet generator

Abstract

The application discloses a control system and a control method for suppressing voltage and current impact during controllable rectification cut-in of a permanent magnet generator. Before switching from uncontrolled rectification to controllable rectification, the three-phase terminal voltage and the three-phase current are synchronously sampled at a preset fixed electric angle, and the direct-axis voltage and current and the quadrature-axis voltage and current in the synchronous rotating coordinate system are obtained through coordinate transformation. The current loop integral term is initialized as the corresponding voltage filter value, the voltage loop integral term is initialized as the negative value of the corresponding quadrature-axis current filter value, the initial voltage is given as the bus voltage plus a preset bias, and the direct-axis current is given as the corresponding current filter value. After the controllable rectification is started, the voltage given value is ramped up to the target value at a fixed slope, and the direct-axis current given value is set to zero after the bus voltage is followed to the position. The application eliminates the impact caused by the mismatch of the controller state from the root, realizes seamless switching of the mode, and significantly improves the system reliability and dynamic response performance.

Description

Technical Field

[0001] This invention relates to a control system and method for suppressing voltage and current surges when a permanent magnet generator is switched on for controlled rectification. Background Technology

[0002] In a permanent magnet starter-generator system, the motor initially operates as a motor, driven by an external power source to complete the starting process. After starting, the motor switches to generator mode. To fully utilize system inertia and simplify control, an uncontrolled rectification phase is typically performed at the beginning of generator operation, during which the generator's phase voltage naturally builds up as the speed increases. When the system needs to switch to a stable controlled rectification generator mode, the switch of the controlled rectifier unit is closed and dual closed-loop control is initiated. However, this switching-in moment generates severe voltage and current spikes, causing severe stress impacts on power switching devices, motor windings, and DC-side capacitors, potentially leading to device damage or protection activation.

[0003] In existing technologies, various solutions have been proposed to address the aforementioned impact problem. For example, CN110620496B discloses a method for suppressing the starting inrush current of a three-phase voltage-type PWM rectifier in a controllable permanent magnet motor generator system. This method suppresses the impact by simply ramping up the DC-side voltage command with the uncontrolled rectifier output voltage as the initial value. However, this method does not solve the core problem of the mismatch between the internal state of the dual closed-loop controller and the actual operating state of the system. At the moment of switching, the PI controllers of the voltage loop and current loop are still in the initial zero state, which will generate drive signals that do not conform to actual needs, resulting in limited current impact suppression effect and slow dynamic response speed.

[0004] For example, CN101399459A discloses a controllable voltage regulation method and device for permanent magnet generators, which achieves voltage stabilization control by adding an additional voltage regulation circuit. However, this solution increases the system hardware cost and complexity, and does not specifically optimize for the impact problem during mode switching. Some other solutions use complex synchronization algorithms or soft-start circuits, which have drawbacks such as high algorithm implementation difficulty, high response delay, and increased cost, and cannot meet the stringent requirements for system reliability and speed in high-end equipment such as aviation and automotive. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies by providing a control system and method for suppressing voltage and current surges when a permanent magnet generator switches to controlled rectification. By precisely initializing the internal state and setpoint of the dual closed-loop controller before switching to controlled rectification, the controller is positioned at its optimal operating point that matches the current system operating state at startup, thereby achieving a smooth and shock-free switch from "uncontrolled rectification" to "controlled rectification".

[0006] The technical solution of the present invention: A control system for suppressing voltage and current surges during controlled rectification switching of a permanent magnet generator includes: A permanent magnet synchronous generator is driven by a prime mover. An uncontrolled rectifier bridge is connected to the three-phase output terminals of the permanent magnet synchronous generator and is used for power conversion during the uncontrolled rectification stage. A controllable rectifier unit is connected in parallel with the three-phase output terminals of the permanent magnet synchronous generator and is used for power conversion during the controllable rectification stage. The DC bus capacitor is connected between the DC output terminal of the controllable rectifier unit and the load. The sampling module includes a voltage sampling unit, a current sampling unit, and a DC bus voltage sampling unit, which are used to sample the three-phase terminal voltage, three-phase current, and DC bus voltage of the permanent magnet synchronous generator, respectively. The position detection module, including a position sensor and a decoding circuit, is used to acquire the rotor electrical angle of the permanent magnet synchronous generator. θ e ; The dual closed-loop controller includes a voltage loop controller and a current loop controller, which enables a smooth switch from the uncontrolled rectification stage to the controlled rectification stage.

[0007] The system employs a topology combining an uncontrolled rectifier bridge and a controlled rectifier unit in parallel. This retains the advantages of the initial uncontrolled rectification phase during power generation, which requires no complex control and utilizes system inertia for natural voltage build-up. It also provides a hardware pathway for the subsequent transition to controlled rectification mode. A sampling module collects three-phase voltage, current, and DC bus voltage in real time, while a position detection module acquires the rotor's precise electrical angle. Both modules together provide accurate system status input to the dual-loop controller. The dual-loop control architecture, with an outer voltage loop stabilizing the bus voltage and an inner current loop limiting the three-phase current, simultaneously ensures voltage regulation accuracy and current response speed. This architecture eliminates the need for additional soft-start circuits, voltage regulation circuits, or other hardware, reducing system cost and size while providing the necessary hardware support for subsequent software algorithms to achieve shock-free switching.

[0008] The controllable rectifier unit is a three-phase full-bridge inverter, which is reused as a rectifier. The permanent magnet start-up-generation system itself requires a three-phase full-bridge inverter for the motor operation during the start-up phase. By reusing this inverter as a rectifier, there is no need to configure a separate controllable rectifier bridge, maximizing the utilization of hardware resources. This feature significantly simplifies the system structure, reduces the number of power devices, and lowers the system's weight, size, and cost. It is particularly suitable for applications with stringent space and weight requirements, such as aviation, automotive, and marine applications, while also improving system integration and reliability.

[0009] The dual-loop controller also includes a coordinate transformation unit, comprising a Clarke transformation module and a Park transformation module, used to convert voltage and current signals in a three-phase stationary coordinate system into direct-axis and quadrature-axis signals in a synchronously rotating coordinate system, respectively. Based on the coordinate transformation theory of motor control, sinusoidal AC quantities in a three-phase stationary coordinate system are difficult to control without steady-state error using a PI controller. By converting the three-phase AC quantities into AC quantities in a two-phase stationary coordinate system using the Clarke transformation, and then into DC quantities in a dq coordinate system that rotates synchronously with the rotor using the Park transformation, the PI controller can achieve high-precision, steady-state error-free control of the DC quantities. This feature transforms the complex three-phase AC control problem into a simple DC control problem, significantly improving control accuracy and dynamic response speed. More importantly, it provides the only feasible parameter basis for the accurate initialization of the subsequent controller state.

[0010] A control method for suppressing voltage and current surges when a permanent magnet generator switches to controlled rectification is disclosed. During the uncontrolled rectification phase, the controller continuously monitors the motor speed and DC bus status. When the conditions for switching to controlled rectification are met, the controller performs the following steps simultaneously with the last uncontrolled rectification cycle: S1. Synchronously sample the three-phase terminal voltage and three-phase current of the permanent magnet synchronous generator. Transform the sampled three-phase terminal voltage and three-phase current into a synchronous rotating coordinate system using Clarke transform and Park transform, respectively, to obtain the direct-axis voltage. u dm quadrature axis voltage u qm Direct-axis current i d and cross-axis current i q The three-phase voltage and current are synchronously sampled under a preset fixed electrical angle, and the dq-axis quantities are obtained through coordinate transformation and then low-pass filtered. The preset fixed electrical angle sampling ensures that the sampling time is completely consistent with the angle used for the Park transform, avoiding the inclusion of AC ripple at twice the fundamental frequency in the transformation result. Low-pass filtering removes high-frequency switching noise and electromagnetic interference during the sampling process. This step provides accurate, ripple-free input data for all subsequent initialization operations, ensuring the accuracy of initialization from the outset.

[0011] For direct-axis voltage u dm quadrature axis voltage u qm 、 Direct-axis current i d and cross-axis current i q Low-pass filtering is performed separately to obtain the corresponding direct-axis voltage filter value. u dmfCross-axis voltage filter value u qmf Direct-axis current filter value i df and cross-axis current filter value i qf ; S2. Set the initial values ​​of the direct-axis current loop and quadrature-axis current loop integrators to the filter values ​​corresponding to the current direct-axis voltage, respectively. u dmf The filter value corresponding to the current quadrature axis voltage u qmf Initialize the direct-axis and quadrature-axis current loop integrators to the corresponding dq-axis voltage filter values. When the PI controller is in steady state, the proportional term output is zero, and the integral term output is equal to the steady-state input voltage of the controlled object. This step ensures that the voltage command output of the current loop at the moment of switching is exactly equal to the steady-state voltage required by the motor, completely eliminating the output abrupt change and three-phase current surge caused by the integrator being initially zero.

[0012] S3. Initialize the output of the voltage loop integrator to the filter value corresponding to the current quadrature-axis current. -i qf At the same time, the initial voltage setpoint of the voltage loop controller is... u dc_init Set to the current DC bus voltage sampling value u dcfdb The sum of the initial voltage and the preset positive voltage bias Δu is used to initialize the voltage loop integrator to the negative of the quadrature-axis current filter value, while setting the initial voltage setpoint to the bus voltage plus a small positive bias. In steady state, the voltage loop output equals the quadrature-axis current setpoint, and the quadrature-axis current during the uncontrolled rectification phase is the current system's steady-state active current. A slightly higher initial setpoint ensures that the controlled rectifier unit naturally takes over the operation of the uncontrolled rectifier bridge, preventing current backflow. This avoids integral saturation of the voltage loop due to initial state mismatch, prevents drastic jumps in the current loop setpoint, and ensures the continuity of the switching process.

[0013] S4. Set the direct-axis current setpoint of the inner loop current controller. i dref Initialize the direct-axis current to the filter value idf corresponding to the current direct-axis current; initialize the direct-axis current setpoint to the current direct-axis current filter value. During the uncontrolled rectification stage, due to the nonlinear conduction characteristics of the diodes, the motor's direct-axis current is not zero. Directly setting it to zero would cause a drastic change in the direct-axis current. This step achieves a smooth transition of the direct-axis current, further suppressing three-phase current fluctuations during the switching process.

[0014] S5. Enable the voltage setpoint of the controllable rectifier unit control voltage loop. u dc_init The voltage is increased linearly from the initial voltage setpoint to the system target voltage value. udc_target The control voltage setpoint is ramped up to the target value with a fixed slope. This avoids voltage loop output fluctuations caused by sudden changes in the voltage setpoint, and balances surge suppression and dynamic response through slope adjustment. This step ensures a rapid transition to the target voltage without surges, avoiding response delays caused by slow ramps.

[0015] S6. When the DC bus voltage feedback value is detected. u dcfdb After reaching the target voltage value, set the direct-axis current loop value. i dref Set to zero. After the bus voltage reaches its set point, set the direct-axis current to zero. Zero direct-axis current in steady state enables unity power factor operation, resulting in the highest motor generation efficiency. This step, after completing the mode switch, brings the system into its optimal steady-state operating state, improving generation efficiency and motor operating economy.

[0016] The formulas for calculating the direct-axis voltage and quadrature-axis voltage are as follows: , in, u ag , u bg , uc g The three-phase terminal voltages obtained from sampling. θ e To synchronize the rotation angle.

[0017] The formulas for calculating the direct-axis current and quadrature-axis current are as follows: , in, i a , i b , i c The three-phase currents obtained from sampling, θ e To synchronize the rotation angle.

[0018] In step S1, the synchronous rotation angle required for the Park transformation θ eThe rotor position is acquired by a position sensor mounted on the shaft of the permanent magnet synchronous generator via a decoding circuit, or estimated by a sensorless observation algorithm. The rotor electrical angle is the core parameter of the Park transform, and its accuracy directly determines the accuracy of the coordinate transformation. Position sensors (such as rotary transformers and encoders) can directly acquire high-precision rotor positions, suitable for applications requiring high control accuracy. Sensorless algorithms estimate the rotor position through the motor's voltage and current model, suitable for applications where sensors cannot be installed or where cost is a concern. This feature improves the versatility of the control method of this invention, enabling it to adapt to permanent magnet power generation systems with different configurations.

[0019] In step S1, the synchronous sampling of the three-phase terminal voltage and the three-phase current is performed under a preset fixed electrical angle, and the sampled direct-axis voltage is obtained. u dm quadrature axis voltage u qm Direct-axis current i d and cross-axis current i q The corresponding filtered values ​​are obtained after low-pass filtering. u dmf , u qmf , i df and i qf The preset fixed electrical angle sampling ensures consistent sampling phase during each mode switch, avoiding inconsistencies in initialization errors caused by random sampling phases. Low-pass filtering further improves the signal-to-noise ratio of the dq axis quantities and filters out high-frequency interference. This enhances the accuracy and consistency of initialization parameters, ensuring the stability and repeatability of impact suppression effects under different operating conditions and preventing fluctuations in impact suppression effects due to sampling errors.

[0020] In step S3, the preset positive voltage bias Δu ranges from 5V to 10V, with the specific value determined based on the system's DC bus voltage level. The value of Δu must satisfy two constraints: first, it must be large enough to ensure the controlled rectifier unit can naturally take over the operation of the uncontrolled rectifier bridge, avoiding current backflow; second, it must be small enough to prevent small-range voltage and current surges caused by an excessively high initial setting. The selection of Δu allows those skilled in the art to quickly determine a suitable bias value based on different system voltage levels, balancing the continuity of the switching process with the surge suppression effect.

[0021] In step S5, the preset fixed slope is set comprehensively based on the system's dynamic response requirements and impact suppression needs. A smaller slope results in better impact suppression, while a larger slope leads to a faster dynamic response. The slope determines the rate of voltage rise; an excessively large slope causes excessive voltage loop output fluctuations, generating impacts; an excessively small slope prolongs the time it takes for the system to reach the target voltage, reducing dynamic response performance. A suitable slope achieves the optimal balance between impact suppression and dynamic response.

[0022] The beneficial effects of this invention are: This invention fundamentally eliminates initial controller surges: By initializing the integral term and setpoint of the dual closed-loop controller to values ​​consistent with the actual operating state of the current system, the voltage command output by the controller at the instant the controllable rectifier is turned on is the steady-state value required by the current system. This avoids integral saturation and output abrupt changes caused by state mismatch, suppressing current and voltage spikes at the source. The surge suppression effect of this invention is improved by more than 80%, and the three-phase current spike at the moment of switching can be controlled within 5% of the rated current.

[0023] Seamless switching is achieved: When the controllable rectifier unit is put into operation, the “starting point” of its controller is the “end point” of the uncontrolled rectifier stage, realizing a smooth connection between the two stages in electromagnetic and control states. This results in almost no disturbance to the motor and DC bus voltage, and the bus voltage fluctuation can be controlled within 2% of the rated voltage.

[0024] Improved system reliability and lifespan: Effectively avoids overcurrent and overvoltage stress during switching, protects power devices, motor windings and DC bus capacitors, and improves the reliability and lifespan of the entire power generation system, especially suitable for applications with extremely high reliability requirements such as aviation and automotive.

[0025] The algorithm is simple and easy to implement: This invention does not require any additional hardware circuits. It can be implemented by performing a series of initialization operations before switching through software algorithms. It is low in cost and easy to integrate and implement in existing digital controllers (such as DSP and FPGA).

[0026] Balancing dynamic response and stability: By employing a strategy of slightly higher initial voltage setpoint and fixed ramp-up, the system ensures a shock-free entry while maintaining a fast dynamic response speed towards the target voltage. This avoids oscillations that may be caused by sudden changes in the setpoint, and the system voltage regulation time can be reduced by more than 30%. Attached Figure Description

[0027] Figure 1 A schematic diagram of a controllable power generation system for permanent magnet motors is provided for this invention.

[0028] Figure 2 The DC bus voltage and three-phase AC current are compared using the traditional method.

[0029] Figure 3 The present invention provides a control method for controlling the bus voltage and three-phase AC current when the circuit is switched on. Detailed Implementation

[0030] Example 1: like Figure 1 As shown, the controllable power generation system of the permanent magnet motor of the present invention includes a prime mover, a permanent magnet synchronous generator (PMSM), an uncontrolled rectifier bridge, a three-phase full-bridge controllable rectifier unit, a DC bus capacitor, an electrical load, a sampling module, a position detection module, and a dual closed-loop controller.

[0031] like Figure 2 As shown, the system works as follows: Start-up phase: The external power supply drives the permanent magnet synchronous generator as a motor through a three-phase full-bridge controllable rectifier unit (operating in inverter mode at this time), which in turn drives the prime mover to start. When the motor speed reaches the preset generator speed threshold, the start-up process ends, and the system enters the uncontrolled rectifier generation phase.

[0032] Uncontrolled rectification stage: All IGBTs in the three-phase full-bridge controlled rectifier unit are turned off. The three-phase AC power output from the permanent magnet synchronous generator is rectified into DC power by the uncontrolled rectifier bridge, charging the DC bus capacitor and supplying power to the load. At this time, the dual closed-loop controller is in standby mode, continuously monitoring the motor speed and DC bus voltage u. dcfdb .

[0033] Triggering condition judgment: When the controller detects that the motor speed is stable at more than 90% of the rated generating speed, and the DC bus voltage is... u dcfdb When the voltage reaches 70% or more of the target voltage, the conditions for switching to controllable rectification are met.

[0034] Controller initialization: While executing the last uncontrolled rectifier cycle, the controller performs the following initialization steps: S1. State Sampling and Coordinate Transformation: The electrical angle of 0° is pre-set as the sampling trigger point in the controller. The position sensor detects the rotor position in real time, and the rotor electrical angle θ is output by the decoding circuit. e .

[0035] When θ e When the temperature is equal to 0°, the controller hardware triggers the three-phase voltage sampling unit and the three-phase current sampling unit to synchronously sample and obtain the three-phase terminal voltage u. ag u bg u cg and three-phase current i a i b i c The sampled values ​​are then subjected to Clarke transform to obtain u.αm u βm and i α i β Then, it undergoes a Park transformation (transformation angle θ). e ) to obtain u dm u qm i d i q The above signal is low-pass filtered with a cutoff frequency of 1kHz to obtain u. dmf u qmf i df i qf .

[0036] S2, Current Loop Integral Initialization: Set the integral term output of the d-axis current loop PI controller to u dmf Set the integral term output of the q-axis current loop PI controller to u qmf .

[0037] S3, Voltage Loop Integration and Setpoint Initialization: Set the integral term output of the voltage loop PI controller to -iqf, and simultaneously set the initial voltage loop setpoint u. dc_init Set to u dcfdb +5V.

[0038] S4. Direct-axis current setpoint initialization: Initialize the setpoint value i of the d-axis current loop. dref Set to i df .

[0039] Controlled rectification startup and voltage ramp-up: After completing all initialization operations, the controller immediately activates the PWM drive signal for the three-phase full-bridge controlled rectifier unit, initiating dual closed-loop control. Voltage loop setpoint u dcref The voltage is linearly increased from 200V+5V to the target voltage of 270V at a fixed slope of 100V / s.

[0040] Steady-state switching: When the controller detects the DC bus voltage feedback value u dcfdb After stabilizing within the range of 270V±1V for 100ms, the d-axis current loop setpoint i is... dref When set to 0, the system enters a steady-state operation with controllable rectification based on unity power factor.

[0041] Implementation results: After adopting the method of the present invention, the peak three-phase current at the moment of switching is reduced from 4.2 times the rated current of the traditional method to 0.3 times the rated current, the DC bus voltage overshoot is reduced from 25% of the traditional method to 1.8%, there is no obvious oscillation during the switching process, and the system operates smoothly.

Claims

1. A control system for suppressing voltage and current surges at cut-in of a controllable rectifier of a permanent magnet generator, characterized in that include: A permanent magnet synchronous generator is driven by a prime mover. An uncontrolled rectifier bridge is connected to the three-phase output terminals of the permanent magnet synchronous generator and is used for power conversion during the uncontrolled rectification stage. A controllable rectifier unit is connected in parallel with the three-phase output terminals of the permanent magnet synchronous generator and is used for power conversion during the controllable rectification stage. The DC bus capacitor is connected between the DC output terminal of the controllable rectifier unit and the load. The sampling module includes a voltage sampling unit, a current sampling unit, and a DC bus voltage sampling unit, which are used to sample the three-phase terminal voltage, three-phase current, and DC bus voltage of the permanent magnet synchronous generator, respectively. A position detection module comprising a position sensor and a decoding circuit for obtaining a rotor electrical angle of a permanent magnet synchronous generator θ e ; The dual closed-loop controller includes a voltage loop controller and a current loop controller, which enables a smooth switch from the uncontrolled rectification stage to the controlled rectification stage.

2. The control system for suppressing voltage and current surges at cut-in of a permanent magnet generator controllable rectifier according to claim 1, characterized in that, The controllable rectifier unit is a three-phase full-bridge inverter, which is multiplexed as a rectifier.

3. The control system for suppressing voltage and current surges at cut-in of a permanent magnet generator controllable rectifier according to claim 1, characterized in that, The dual closed-loop controller also includes a coordinate transformation unit, which includes a Clarke transformation module and a Park transformation module, used to convert voltage and current signals in a three-phase stationary coordinate system into direct-axis and quadrature-axis signals in a synchronous rotating coordinate system, respectively.

4. A control method for suppressing voltage and current surge at cut-in of a permanent magnet generator controllable rectifier, the system operates in uncontrolled rectification phase, the controller continuously monitors the motor speed and DC bus state, characterized in that, When the conditions for switching to controlled rectification are met, the controller performs the following steps while executing the last uncontrolled rectification cycle: S1. Synchronously sample the three-phase terminal voltage and three-phase current of the permanent magnet synchronous generator. Transform the sampled three-phase terminal voltage and three-phase current into the synchronous rotating coordinate system using Clarke transform and Park transform, respectively, to obtain the direct-axis voltage. u dm quadrature axis voltage u qm Direct-axis current i d and cross-axis current i q ; For direct-axis voltage u dm quadrature axis voltage u qm 、 Direct-axis current i d and cross-axis current i q Low-pass filtering is performed separately to obtain the corresponding direct-axis voltage filter value. u dmf Cross-axis voltage filter value u qmf Direct-axis current filter value i df and cross-axis current filter value i qf ; S2. Set the initial values ​​of the direct-axis current loop and quadrature-axis current loop integrators to the filter values ​​corresponding to the current direct-axis voltage, respectively. u dmf The filter value corresponding to the current quadrature axis voltage u qmf ; S3. Initialize the output of the voltage loop integrator to the filter value corresponding to the current quadrature-axis current. -i qf At the same time, the initial voltage setpoint of the voltage loop controller is... u dc_init Set to the current DC bus voltage sampling value u dcfdb The sum of the preset positive voltage bias Δu; S4, setting the direct-axis current given value of the inner ring current controller to i dref initialized to the filter value idf corresponding to the current direct-axis current S5, opening the voltage set value of the controllable rectifier unit control voltage loop u dc_init linearly increasing from the initial voltage set value to the system target voltage value at 270 V / s u dc_target ; S6, when the DC bus voltage feedback value is detected u dcfdb The direct axis current loop given value is set to zero after following to the target voltage value i dref The direct axis current loop given value is set to zero after following to the target voltage value 5. The control method of claim 4, wherein the control method is characterized by: The formulas for calculating the direct-axis voltage and quadrature-axis voltage are as follows: ， in, u ag , u bg , uc g The three-phase terminal voltages obtained from sampling, θ e To synchronize the rotation angle.

6. The control method of claim 4, wherein the voltage and current surge at the cut-in of the permanent magnet generator controlled rectification is suppressed by, The formulas for calculating the direct-axis current and quadrature-axis current are as follows: ， wherein i a , i b , i c is the sampled three-phase current, θ e is the synchronous rotation angle.

7. The control method of claim 4, wherein the voltage and current surge at the cut-in of the permanent magnet generator controlled rectification is suppressed by, In step S1, the synchronous rotation angle required for the Park transformation θ e The position sensor is obtained by a decoding circuit from a position sensor installed on the shaft of the permanent magnet synchronous generator, or estimated by a sensorless observation algorithm.

8. The control method of claim 4, wherein the voltage and current surge at the cut-in of the permanent magnet generator controlled rectification is suppressed by, In step S1, the synchronous sampling of the three-phase terminal voltage and the three-phase current is performed under a preset fixed electrical angle, and the sampled direct-axis voltage is obtained. u dm quadrature axis voltage u qm Direct-axis current i d and cross-axis current i q The corresponding filtered values ​​are obtained after low-pass filtering. u dmf , u qmf , i df and i qf .

9. The control method of claim 4, wherein, In step S3, the value of the preset positive voltage bias Δu ranges from 5V to 10V, and the specific value is determined according to the DC bus voltage level of the system.

10. The control method of claim 4, wherein, In step S5, the preset fixed slope is set comprehensively based on the system dynamic response requirements and impact suppression needs. The smaller the slope, the better the impact suppression effect; the larger the slope, the faster the dynamic response speed.

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