Method and system for controlling transient state current performance of a grid-forming energy storage converter

Abstract

The application discloses a method and system for controlling performance of transient state current of network-constructed energy storage converter, and belongs to the technical field of power electronic converter control. The method comprises the following steps: firstly, a system model of a main circuit topology of the network-constructed energy storage converter, a virtual synchronous generator power outer loop controller and a voltage-current double closed loop control architecture is established; and secondly, in a current inner loop of the voltage-current double closed loop architecture, a sliding mode controller based on a differential sliding mode surface and an exponential reaching law is designed to replace a traditional proportional integral controller. By using the method, problems of current response lag, overshoot increase and insufficient robustness of the traditional proportional integral control in a power grid fault transient process are solved.

Description

Technical Field

[0001] This invention relates to a method and system for controlling the transient steady-state current performance of a grid-type energy storage converter, belonging to the field of power electronic converter control technology. Background Technology

[0002] With the deepening of the "dual carbon" strategy and the acceleration of the global low-carbon energy transition, as of the end of June 2024, the proportion of new energy installed capacity in my country had exceeded 53%. The high proportion and volatility of new energy sources, along with the massive influx of power electronic equipment, have profoundly reshaped the dynamic characteristics of the power system. The "new energy + energy storage" collaborative operation mode has become the core path to support the stable operation of the new power system. As a key interface device for energy conversion, the control strategy of energy storage converters plays a decisive role in maintaining the stability of system frequency and voltage.

[0003] Research on grid-type converters mainly focuses on two major directions: optimization of key parameters (such as inertia and damping) of the virtual synchronous machine and improvement of advanced control algorithms. Regarding parameter optimization, Gong et al. proposed an improved adaptive algorithm to optimize the energy storage capacity allocation of a modular multilevel system by constraining the range of inertia and damping parameters. In terms of algorithm improvement, active disturbance rejection control (ADRC) has attracted much attention due to its independence from accurate models and strong disturbance rejection capability. Wang Xinju et al. combined it with model predictive control and applied it to dual-mode rectifiers, effectively reducing grid-side current harmonics; Wang Shu et al. combined it with adaptive feedforward control based on angular acceleration to improve the disturbance rejection capability of magnetic levitation systems. However, existing improvement strategies still suffer from problems such as complex parameter tuning and high computational load. Therefore, it is urgent to explore new robust control strategies with high computational efficiency and parameter adaptability to improve the metastable current control performance of grid-type energy storage converters under complex operating conditions. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for controlling the transient steady-state current performance of a grid-connected energy storage converter. This invention solves the problems of current response lag, increased overshoot, and insufficient robustness of traditional proportional-integral control during grid fault transient processes, significantly improves transient response speed and steady-state accuracy, and enhances the grid-connected support stability of the grid-connected energy storage converter.

[0005] To achieve the above objectives / to solve the above technical problems, the present invention is implemented using the following technical solution:

[0006] First aspect: A method for controlling the transient steady-state current performance of a grid-type energy storage converter, the method comprising:

[0007] A system model of a grid-type energy storage converter is established. The system model includes a main circuit topology model, a power outer loop control model based on a virtual synchronous generator algorithm, and a voltage-current dual closed-loop control architecture model.

[0008] Based on the current inner loop control module in the voltage-current dual closed-loop control architecture, a sliding mode controller based on the differential sliding surface and the exponential reaching law is designed.

[0009] The sliding mode controller is integrated into the system model to form a closed-loop control system, thereby improving the transient steady-state current control performance of the grid-type energy storage converter.

[0010] Optionally, the virtual synchronous generator algorithm includes:

[0011] Based on the fundamental principles of synchronous motors, the rotor mechanical equations of the virtual synchronous machine are obtained as follows:

[0012] ,

[0013] In the formula: It is the moment of inertia; The damping coefficient; For mechanical torque; Electromagnetic torque; This is the damping torque; Mechanical power; Electromagnetic power; The synchronous angular velocity of the power grid; This is the actual angular velocity;

[0014] To simulate the primary frequency regulation function of a synchronous motor, a virtual speed controller is constructed, and its relational expression is as follows:

[0015] ,

[0016] In the formula For frequency regulation coefficients, in converters, To output active power, For a given output, This is because frequency regulation requires additional active power;

[0017] Combining equations (1) and (2), we get:

[0018] ,

[0019] The virtual synchronous machine regulates its virtual excitation potential. The amplitude-phase angle is used to introduce voltage offset as a feedforward compensation term in the reactive power control loop of the virtual synchronous machine. Based on this, the reactive power output of the system is dynamically corrected. The reactive power-voltage droop characteristic of the quasi-synchronous machine is characterized as follows:

[0020] ,

[0021] In the formula: To output reactive power, This is a reference value for reactive power. This is the effective value of the terminal voltage. This is the actual output voltage of the virtual synchronous machine. This is the reactive power droop coefficient.

[0022] Optionally, the expression for the differential sliding surface is:

[0023] The system state error vector is defined in the rotating coordinate system as follows: :

[0024] ,

[0025] In the formula: , These are the reference values ​​for the d-axis and q-axis output currents, respectively, according to the formula... The following sliding surface for the integrator terminal is designed:

[0026] ,

[0027] in: , >0 represents a design parameter.

[0028] Optionally, the expression for the exponential reaching law is:

[0029] ,

[0030] in, Represents sliding mode variable The time derivative of represents the rate of change of the sliding surface in state space. Represents the sliding mode variable. This represents the approach rate on the sliding surface; the larger the value, the faster the approach. This represents the exponential decay rate on the sliding surface.

[0031] Optionally, under the exponential reaching law, the system mode oscillates at a high frequency at the sliding surface. The expression for the unknown quantity u can be further calculated using equation (8):

[0032] ,

[0033] u is an intermediate variable in the process, not voltage or current, and its relationship with the output is as follows: .

[0034] Optional , The reference current is calculated as follows:

[0035] Substituting u back, we obtain... , The reference current is:

[0036] .

[0037] Optionally, in the voltage-current dual closed-loop control architecture, the voltage outer loop adopts proportional-integral control, and the output serves as a reference command for the current inner loop; the current inner loop adopts the sliding mode controller, and the output is driven by the main circuit power devices after space vector pulse width modulation.

[0038] Optionally, the power outer loop control model based on the virtual synchronous generator algorithm includes an active-frequency control loop and a reactive-voltage control loop, used to simulate the inertia, damping, and primary frequency regulation characteristics of a synchronous generator.

[0039] Second aspect: A control system for an energy storage converter, the system comprising:

[0040] The main power circuit is used to perform DC-to-AC energy conversion;

[0041] The sampling and conditioning unit, connected to the main power circuit, is used to acquire three-phase voltage and current signals;

[0042] A coordinate transformation unit, connected to the sampling and conditioning unit, is used to convert electrical quantities in the abc coordinate system into DC quantities in the dq coordinate system.

[0043] A virtual synchronous generator control module, connected to the coordinate transformation unit, is used to generate voltage amplitude reference commands and phase angle signals based on power commands and feedback power; a voltage outer loop controller, connected to the virtual synchronous generator control module and the coordinate transformation unit, is used to generate current reference commands.

[0044] The inner current sliding mode controller is connected to the outer voltage controller and the coordinate transformation unit, and is used to calculate voltage control commands based on the differential sliding surface and the exponential reaching law.

[0045] The SVPWM modulation module, connected to the current inner loop sliding mode controller, is used to generate drive signals to control the main power circuit.

[0046] Optionally, the output of the current inner loop sliding mode controller is connected to the space vector pulse width modulation module to generate drive signals to control the inverter bridge arm switching devices.

[0047] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0048] This invention addresses transient current control in grid-connected energy storage converters by combining a sliding mode controller with a differential sliding surface design, significantly improving system power response stability. The constructed differential sliding surface, in conjunction with an exponential reaching law mechanism, leverages the robustness of the sliding mode to achieve rapid convergence of current tracking errors, ensuring dynamic suppression of grid disturbances and overcoming the inherent defects of response lag and increased overshoot in traditional proportional-integral control.

[0049] By reconstructing the current inner loop using a sliding mode controller, the complex parameter tuning process is avoided, enhancing the engineering versatility of the control strategy. Simulation experiments show that, compared with traditional proportional-integral control, the proposed sliding mode controller strategy significantly improves the dynamic response speed of the current loop, effectively reduces transient overshoot, and exhibits excellent stability and robustness under different operating conditions.

[0050] This method provides high-precision current tracking capability for grid-connected energy storage converters. In new energy grid connection and microgrid control scenarios, it can significantly enhance the system's fault ride-through capability and power support strength, which is of key value for ensuring the transient stable operation of new power systems. Attached Figure Description

[0051] Figure 1 This is a control block diagram of the energy storage converter based on sliding mode control according to the present invention; Figure 2 This is the active and reactive power loop model of the present invention; Figure 3 This is the trajectory of the state points of the exponential reaching law system of this invention; Figure 4 This invention illustrates the d-axis current following behavior under different strategies during step operation. Figure 5 This invention provides a comparison of steady-state start-up current waveforms under different d-axis current following strategies during steady-state operation. Figure 6 This invention provides a comparison of steady-state primary frequency modulation current waveforms under different d-axis current following strategies during steady-state operation. Figure 7 Comparison of different current-following waveforms in this invention Figure 1 ; Figure 8 Comparison of different current-following waveforms in this invention Figure 2 ; Figure 9 This is a topology diagram of the main circuit of the energy storage converter of the present invention. Detailed Implementation

[0052] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0053] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0054] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] like Figure 1 As shown, a method for controlling the transient steady-state current performance of a grid-type energy storage converter is disclosed, the method comprising:

[0056] Step 1: Establish a system model for the grid-type energy storage converter. The system model includes a main circuit topology model, a power outer loop control model based on the virtual synchronous generator algorithm, and a voltage-current dual closed-loop control architecture model.

[0057] Step 2: Based on the current inner loop control module in the voltage-current dual closed-loop control architecture model, design a sliding mode controller based on differential sliding surface and exponential reaching law to replace the traditional proportional-integral controller.

[0058] Step 3: Integrate the sliding mode controller into the system model to form a closed-loop control system, thereby improving the transient steady-state current control performance of the grid-type energy storage converter.

[0059] In this embodiment, a grid-connected simulation model of a grid-type energy storage converter based on sliding mode control is constructed. Then, three sets of operating conditions are set for comparison. The dynamic performance of all operating conditions is compared by simulation comparison with proportional-integral control through three sets of comparative experiments (step condition, steady state, primary frequency regulation condition, and low voltage ride-through condition).

[0060] The implementation of the control strategy of this invention mainly includes two parts: one is to establish a circuit model, a virtual synchronous machine model, and a dual closed-loop model to build a basic control model; the other part is to build a sliding mode control model based on a differential sliding surface and an exponential reaching law. The inherent strong robustness and fast reaching characteristics of the sliding mode controller can effectively suppress the influence of system parameter changes, grid voltage fluctuations, and load disturbances on current tracking. The superiority of the strategy is verified through comparative experiments and simulations.

[0061] (1) Virtual Synchronizer Algorithm Model;

[0062] Based on the fundamental principles of synchronous motors, the rotor mechanical equations of the virtual synchronous machine can be obtained as follows:

[0063]

[0064] In the formula: It is the moment of inertia; The damping coefficient; For mechanical torque; Electromagnetic torque; This is the damping torque; Mechanical power; Electromagnetic power; This refers to the angular velocity of the power grid synchronization.

[0065] To simulate the primary frequency regulation function of a synchronous motor, a virtual speed controller is constructed, and its relational expression is as follows:

[0066]

[0067] In the formula This is the frequency regulation coefficient. In a converter, To output active power, For a given output, This is because frequency adjustment requires additional active power.

[0068] By combining equations 1 and 2, we can obtain

[0069]

[0070] The virtual synchronous machine regulates its virtual excitation potential. By determining the amplitude-phase angle, precise regulation of reactive power can be achieved, thereby maintaining stable voltage at the grid connection point. To this end, voltage offset is introduced as a feedforward compensation term into the reactive power control loop of the virtual synchronous machine, thereby dynamically correcting the system's reactive power output. The reactive power-voltage droop characteristic of the virtual synchronous machine is characterized as follows:

[0071]

[0072] In the formula: To output reactive power, This is a reference value for reactive power. This is the effective value of the terminal voltage. This is the actual output voltage of the virtual synchronous machine. This is the reactive power droop coefficient.

[0073] (2) Design of sliding mode control;

[0074] The design method for the differential sliding surface and the exponential reaching law is as follows:

[0075] In a rotating coordinate system (dq axis), the system state error vector is defined as follows: :

[0076]

[0077] In the formula: , These are the reference values ​​for the d-axis and q-axis output currents, respectively, according to the formula... The sliding surface of the integrator terminal can be designed as follows:

[0078]

[0079] in: , >0 represents the design parameter and is also where the system reflects its performance and quality.

[0080] Among the four approach laws, to ensure that the sliding motion has good approach properties, that is, the system state variables converge rapidly to the sliding surface in a finite time, while effectively suppressing high-frequency chattering, this invention adopts an exponential approach law, such as... Figure 3 The expression shown is:

[0081] ,

[0082] Under the exponential reaching law, the system mode oscillates at a small amplitude at the sliding surface, eventually reaching the system setpoint. Further calculation yields the expression for the unknown variable u:

[0083] ,

[0084] Substituting u back, we obtain... , The reference current is:

[0085] ,

[0086] Formulas (8) and (9) are used to calculate the setpoint of the inner current loop, generate the actual switching signal through PWM modulation, drive the power electronic converter, and ultimately achieve high-precision and robust current control; specifically, the calculation is: sliding mode control quantity i d i q The relationship between the expressions for the exponential approach term and the sliding mode compensation term is used to ultimately obtain the current control command.

[0087] With the integration stage, the chattering effect of the singular function's sign function on the system can be reduced, resulting in a smoother current flow. Ultimately, it can also be verified that the system in equation... Under the adjustment of [the system / mechanism], it tends to be stable.

[0088] Practical application results:

[0089] To verify the impact of sudden current changes on the system's dynamic performance, the voltage and current dual closed-loop current command was disconnected, and a step function was used to replace the original current command, thus simulating the system. The given active power was kept at 170kW, and the d-axis current at 254A. Because the system was treated as an "open loop," the current followed rapidly, and the system's response under different control strategies is as follows: Figure 4 As shown. From Figure 4 As can be observed in the control experiment, under proportional-integral control, the d-axis current of the system showed a significant overshoot of approximately 93A, and the adjustment time to return to steady state was 0.02s. Under sliding mode control, the overshoot was significantly reduced, and the current quickly followed, with the time to return to steady state being 0.005s.

[0090] To verify the performance of sliding mode control under actual operating conditions, the step input was replaced with the actual voltage loop output input. The model was run under normal conditions, and a 0.5Hz frequency drop was set at 0.3s to simulate the performance under single-frequency modulation. The actual power input remained unchanged, and two sets of proportional-integral control conditions were set to reduce the random effects caused by parameters. The system response under different control strategies is shown below. Figures 5-6 As shown. Under steady-state conditions, the system's settling time is approximately equal under both proportional-integral (PI) and sliding mode (SMT) control. PI control (parameter 1) produces an overshoot of approximately 3A, while PI control (parameter 2) exhibits short-term fluctuations after reaching steady state. SMT control has no overshoot and does not produce fluctuations upon reaching steady state. During a single frequency modulation, the system's settling time is equal under both PI and SMT control; however, both PI control systems exhibit glitches, resulting in severe vibrations within a small range.

[0091] Transient operating conditions such as low-voltage ride-through can generate instantaneous voltage differences, leading to inrush currents that can harm system operation. This paper observes the transient current waveforms of proportional-integral control and sliding mode control under a 90% voltage drop condition. The results are as follows: Figures 6-8 As shown. A transient voltage drop is set between 0.3 and 0.7 s, by... Figure 7 It can be observed that the instantaneous overcurrents of both are identical. During the transient process at point A, the proportional-integral (PI) control has a settling time of 0.2 s and exhibits underdamped oscillations at the steady-state current, with a maximum overshoot of 6 A; the sliding mode control has a settling time of 0.1 s and no overshoot. When the current recovers after the low-voltage ride-through ends, the situation is similar to that at the beginning of the ride-through. The PI control exhibits multiple oscillations with a settling time of 0.07 s; the sliding mode control has a settling time of 0.05 s and no overshoot.

[0092] Simulation results under three operating conditions demonstrate that, compared to traditional proportional-integral control, the proposed sliding mode controller strategy significantly improves the dynamic response speed of the current loop, effectively reduces transient overshoot, and exhibits excellent stability and robustness under different operating conditions. This strategy provides an effective solution for enhancing the fault ride-through capability and power support stability of grid-connected energy storage converters in complex power grid environments.

[0093] Example 1 discloses the main circuit topology model of the energy storage converter, which is as follows: Figure 9 As shown

[0094] The DC side section, including the battery pack and DC support capacitor, is connected between the battery and the inverter bridge. Its function is to stabilize voltage, buffer energy, absorb the high-frequency pulsating current generated by the inverter's switching operations, and provide a stable DC voltage input to the inverter.

[0095] The power conversion section, specifically the three-phase inverter bridge, is the core of the main circuit and typically consists of six power switching devices. It converts direct current (DC) to alternating current (discharge mode) or alternating current to DC (charging mode).

[0096] The AC filtering section uses an LCL filter connected to the inverter bridge output. It filters out harmonics generated by the high-frequency switching of the power switching devices, making the output current a smooth sine wave.

[0097] On the AC grid side, the converter is ultimately connected to the public power grid or AC load.

[0098] Example 2 discloses an energy storage converter control system, the system comprising:

[0099] The main power circuit is used to perform DC-to-AC energy conversion;

[0100] The sampling and conditioning unit, connected to the main power circuit, is used to acquire three-phase voltage and current signals;

[0101] A coordinate transformation unit, connected to the sampling and conditioning unit, is used to convert electrical quantities in the abc coordinate system into DC quantities in the dq coordinate system.

[0102] A virtual synchronous generator control module, connected to the coordinate transformation unit, is used to generate voltage amplitude reference commands and phase angle signals based on power commands and feedback power; a voltage outer loop controller, connected to the virtual synchronous generator control module and the coordinate transformation unit, is used to generate current reference commands.

[0103] The inner current sliding mode controller is connected to the outer voltage controller and the coordinate transformation unit, and is used to calculate voltage control commands based on the differential sliding surface and the exponential reaching law.

[0104] The SVPWM modulation module, connected to the current inner loop sliding mode controller, is used to generate drive signals to control the main power circuit.

[0105] The output of the current inner loop sliding mode controller is connected to the space vector pulse width modulation module to generate drive signals to control the inverter bridge arm switching devices.

[0106] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the transient steady-state current performance of a grid-type energy storage converter, characterized in that, The method includes: A system model of a grid-type energy storage converter is established. The system model includes a main circuit topology model, a power outer loop control model based on a virtual synchronous generator algorithm, and a voltage-current dual closed-loop control architecture model. Based on the current inner loop control module in the voltage-current dual closed-loop control architecture, a sliding mode controller based on the differential sliding surface and the exponential reaching law is designed. The sliding mode controller is integrated into the system model to form a closed-loop control system, thereby improving the transient steady-state current control performance of the grid-type energy storage converter.

2. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 1, characterized in that, The virtual synchronous generator algorithm includes: Based on the fundamental principles of synchronous motors, the rotor mechanical equations of the virtual synchronous machine are obtained as follows: ， In the formula: It is the moment of inertia; The damping coefficient; For mechanical torque; Electromagnetic torque; This is the damping torque; Mechanical power; Electromagnetic power; The synchronous angular velocity of the power grid; This is the actual angular velocity; To simulate the primary frequency regulation function of a synchronous motor, a virtual speed controller is constructed, and its relational expression is as follows: ， In the formula For frequency regulation coefficients, in converters, To output active power, For a given output, This is because frequency regulation requires additional active power; Combining equations (1) and (2), we get: ， The virtual synchronous machine regulates its virtual excitation potential. The amplitude-phase angle is used to introduce voltage offset as a feedforward compensation term in the reactive power control loop of the virtual synchronous machine. Based on this, the reactive power output of the system is dynamically corrected. The reactive power-voltage droop characteristic of the quasi-synchronous machine is characterized as follows: ， In the formula: To output reactive power, This is a reference value for reactive power. This is the effective value of the terminal voltage. This is the actual output voltage of the virtual synchronous machine. This is the reactive power droop coefficient.

3. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 1, characterized in that, The expression for the differential sliding surface: The system state error vector is defined in the rotating coordinate system as follows: : ， In the formula: , These are the reference values ​​for the d-axis and q-axis output currents, respectively, according to the formula... The following sliding surface for the integrator terminal is designed: ， in: , >0 represents a design parameter.

4. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 1, characterized in that, The expression for the exponential reaching law is: ， in, Represents sliding mode variable The time derivative of represents the rate of change of the sliding surface in state space. Represents the sliding mode variable. This represents the approach rate on the sliding surface; the larger the value, the faster the approach. This represents the exponential decay rate on the sliding surface.

5. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 7, characterized in that, Under the exponential reaching law, the system mode oscillates at a high frequency at the sliding surface. The expression for the unknown quantity u is further calculated using equation (8): , u is an intermediate variable in the process, not voltage or current, and its relationship with the output is as follows: .

6. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 7, characterized in that, , The reference current is calculated as follows: Substituting u back, we obtain... , The reference current is: 。 7. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 1, characterized in that, In the voltage-current dual closed-loop control architecture, the voltage outer loop adopts proportional-integral control, and the output serves as the reference command for the current inner loop; the current inner loop adopts the sliding mode controller, and the output is driven by the main circuit power devices after space vector pulse width modulation.

8. The method for controlling the transient steady-state current performance of a grid-type energy storage converter according to claim 1, characterized in that, The power outer loop control model based on the virtual synchronous generator algorithm includes an active-frequency control loop and a reactive-voltage control loop, which are used to simulate the inertia, damping, and primary frequency regulation characteristics of a synchronous generator.

9. A control system for an energy storage converter, characterized in that, The system includes: The main power circuit is used to perform DC-to-AC energy conversion; The sampling and conditioning unit, connected to the main power circuit, is used to acquire three-phase voltage and current signals; A coordinate transformation unit, connected to the sampling and conditioning unit, is used to convert electrical quantities in the abc coordinate system into DC quantities in the dq coordinate system. A virtual synchronous generator control module, connected to the coordinate transformation unit, is used to generate voltage amplitude reference commands and phase angle signals based on power commands and feedback power; a voltage outer loop controller, connected to the virtual synchronous generator control module and the coordinate transformation unit, is used to generate current reference commands. The inner current sliding mode controller is connected to the outer voltage controller and the coordinate transformation unit, and is used to calculate voltage control commands based on the differential sliding surface and the exponential reaching law. The SVPWM modulation module, connected to the current inner loop sliding mode controller, is used to generate drive signals to control the main power circuit.

10. The system according to claim 9, characterized in that, The output of the current inner loop sliding mode controller is connected to the space vector pulse width modulation module to generate drive signals to control the inverter bridge arm switching devices.

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