Enhanced grid-forming converter transient stability improvement strategy and system based on current amplitude limiting

Abstract

The invention discloses an enhanced transient stability improvement strategy and system for a grid-forming converter based on current amplitude limiting, and aims to effectively suppress a power angle instability phenomenon in a power grid fault or transient period and ensure that the converter has higher stability in a grid-connected process. The specific implementation comprises a dynamic dq-axis current amplitude limiting control strategy and a reference power control structure. Three-phase voltage and current of a grid-connected point of the converter are measured in real time, and a dq-axis current reference value and a power ring reference value are dynamically adjusted by combining a power angle and angular velocity deviation in an active power link, so that power angle instability during a transient period is accurately inhibited. According to the control strategy, the risks of overcurrent and system instability are effectively reduced, and particularly when a power grid breaks down or is in a normal condition, quick response and stable output of the system are ensured by switching the control modes in real time.

Description

An enhanced transient stability improvement strategy and system for grid-connected converters based on current limiting Technical Field

[0001] This invention relates to the field of power system new energy control technology, and in particular to an enhanced transient stability improvement strategy and system for grid-connected converters based on current limiting. Background Technology

[0002] Traditional power systems are rapidly transforming into clean and low-carbon new power systems, with renewable energy generation based on voltage source converters receiving widespread attention. In recent years, new energy sources such as wind power and photovoltaics have developed rapidly, and the proportion of renewable energy installed capacity in the power grid is increasing daily. Most renewable energy power generation equipment uses power electronics as its interface to connect to the power grid. As the proportion of various renewable energy power generation equipment in the system continues to increase, the traditional power system dominated by synchronous machines will be gradually replaced by a new power system dominated by power electronic equipment.

[0003] Converter control strategies often employ grid-following and grid-connected control strategies. Unlike traditional generators and other equipment, converters using power electronics interfaces exhibit significant differences in dynamic characteristics. Furthermore, with the increasing proportion of renewable energy sources, research has revealed that grid-following converters cannot provide voltage support to the system during transient processes. Therefore, applying grid-connected converters to achieve transient synchronization stability control has become a research frontier and hot topic.

[0004] In applications, it has been found that the port characteristics of power electronic converters are also constrained by their hardware capabilities. It is generally believed that the overload current that the converter can provide is limited. In order to protect the safety of the power electronic converter itself, when the system suffers faults such as transmission line short circuits, short lines, and circuit breaker tripping, the grid-type converter should trigger its corresponding current limiting control strategy. Therefore, the research on current limiting control of grid-type converters has become an urgent problem to be solved. Summary of the Invention

[0005] To address the stability challenges of power systems facing transient faults, this invention discloses an enhanced transient stability improvement strategy and system for grid-connected converters based on current limiting. The aim is to improve the power angle stability of the power system during grid faults and reduce the probability of instability in grid-connected converter systems under fault conditions such as grid voltage dips, thereby providing a reliable guarantee for the safe and stable operation of the power system. This strategy demonstrates excellent stability and anti-interference capabilities when dealing with system faults, providing a new technical approach for improving grid reliability and power transmission quality.

[0006] To address the aforementioned problems, this invention provides an enhanced dq-axis current limiting control strategy, which consists of two parts: a dynamic dq-axis current limiting control strategy and a reference power control strategy (RPCS). These two components work together to form an efficient and flexible control mechanism, effectively addressing transient instability issues caused by grid faults.

[0007] The preferred dynamic dq-axis current limiting control strategy has the following specific control expression:

[0008]

[0009] in, Indicates the reference value of the d-axis current; Indicates the q-axis current reference value; I dwf Indicates the actual value of the d-axis current; I qref Indicates the actual value of the q-axis current; I max δ0' represents the maximum current limit; I represents the actual current value; δ0' represents the initial operating power angle value of the converter; δ' represents the actual operating power angle value of the converter.

[0010] Preferably, the specific control expression for the reference value control structure is as follows:

[0011]

[0012] Where, P ref Q represents the reference value for active power in the active power loop; ref Indicates the reactive power reference values ​​of the reactive power loop; k1 and k2

[0013] represents the control coefficient, and 1>k1>k2>0; S represents the total power of the system; P represents the active power at the grid connection point calculated by the system through the measurement module measuring voltage and current; Δω represents the angular velocity deviation.

[0014] Preferably, the specific control process of the dynamic dq-axis current limiting control strategy includes the following steps:

[0015] Step 1: Calculate the active power and reactive power using the key electrical quantities U and I at the grid connection points of new energy sources in the power grid;

[0016] Step 2: Use this power as the power loop input, and apply the active power equation:

[0017]

[0018] And reactive power equation:

[0019]

[0020] Calculate the power angle δ' and voltage reference value of the power loop output, as well as the angular velocity deviation Δω of the power loop output;

[0021] Step 3: Perform a Parker transformation on the obtained power angle δ' and voltage reference value to obtain the dq-axis component of the voltage reference value; Step 4: If the triggering condition is not met (I≥I), proceed with the determination. max And (δ'≥δ0'), then the dq axis component of the voltage reference value obtains a PWM signal through the voltage and current double inner loop structure to control the converter output;

[0022] Step 5: If the triggering condition (I≥I) is met by judgment... max If δ'≥δ0'), then the enhanced dq-axis current limiting control strategy takes effect. The dq-axis current reference value control and reference power control are performed through the expression of the enhanced dq-axis current limiting control strategy to obtain the final dq-axis current reference value signal.

[0023] Step 6: Input the dynamically adjusted final dq axis current reference value signal into the current loop to control the current output of the converter and generate a corresponding PWM signal to achieve precise adjustment of the converter;

[0024] Step 7: During the control period, the strategy remains in a hold state until δ'<δ0' is detected. At this point, the dynamic dq-axis current limiting control strategy is exited, and the previous grid-type converter control strategy is restored.

[0025] To address the aforementioned technical problems, this invention also provides an enhanced dq-axis current limiting control strategy structure, comprising:

[0026] Acquisition Module: This module is responsible for accurately acquiring the electrical quantity data required for system operation; specifically, it includes:

[0027] Measure the voltage and current values ​​at the converter's grid connection point;

[0028] Measure the frequency deviation Δω of the converter control output;

[0029] The phase difference δ0' between the converter grid connection point voltage and the grid voltage is measured under normal operating conditions of the measurement system.

[0030] The real-time voltage phase difference δ' after a system failure is measured reflects the current operating status of the system.

[0031] Transformation module: Used to perform Park transformation on the electrical quantities obtained by the measurement module and the signals before the PWM signal is generated;

[0032] Comparison Module: This module compares the electrical quantity data acquired by the acquisition module with preset thresholds, performs corresponding comparisons and judgments on the current and power angle values ​​obtained by the acquisition module, and determines the segmented range of the current reference value to be output; it compares the power calculated from the current and voltage with the thresholds to determine the reference value that the power should track. Combining the results obtained from the above two control strategies, it determines whether it is necessary to switch between current reference value and power reference value modes, ensuring that the system can select the appropriate control strategy according to different fault conditions.

[0033] Regulation Module: This module is responsible for regulating the electrical parameters required for system operation. It performs real-time calculations based on the expression of the enhanced dq-axis current limiting control strategy and outputs control signals to the PWM converter system to enhance system stability.

[0034] Beneficial effects

[0035] This invention enables the original grid-type control converter strategy to achieve current limiting; and significantly improves and optimizes the power angle stability of the grid-type converter during the current limiting period. Attached Figure Description

[0036] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with their description, serve to explain the principles, including providing a further understanding of the disclosure. The drawings are included in and form part of this specification.

[0037] Figure 1 is a schematic flowchart of the enhanced dq-axis current limiting control strategy control method according to an embodiment of the present disclosure.

[0038] Figure 2 is a schematic diagram of a power electronic converter control system according to an embodiment of the present disclosure;

[0039] Figure 3 is a schematic diagram of the power reference value control structure according to an embodiment of the present disclosure;

[0040] Figure 4 is a schematic diagram of the simulation verification of the control system according to the embodiments of this disclosure;

[0041] Figure 5 is a schematic diagram comparing the simulation results of the power angle-time curve of the dynamic dq axis current limiting control strategy according to the embodiments of this disclosure.

[0042] Figure 6 is a schematic diagram of the simulation results of the active power-power angle curve of the dynamic dq axis current limiting control strategy according to the embodiments of this disclosure.

[0043] Figure 7 is a schematic diagram comparing the simulation results of the power angle-time curve of the enhanced dq-axis current limiting control strategy according to the embodiments of this disclosure. Detailed Implementation

[0044] To make the objectives, features, and advantages of the present invention more apparent and easier to understand, the technical solutions of the present invention are now clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the present invention is not limited to the embodiments described below, and specific implementation methods can be determined based on the technical solutions of the present invention and in combination with actual circumstances. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0045] The present disclosure will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] The specific control expressions for the dynamic dq-axis current limiting control strategy described in this disclosure include:

[0047]

[0048] in Indicates the reference value of the d-axis current; Indicates the q-axis current reference value; I dwf Indicates the actual value of the d-axis current; I qref Indicates the actual value of the q-axis current; I max δ0' represents the maximum current limit; I represents the actual current value; δ0' represents the initial operating power angle value of the converter; δ' represents the actual operating power angle value of the converter.

[0049] The specific control expression for the reference value control structure is as follows:

[0050]

[0051] Where, P ref Q represents the reference value for active power in the active power loop; ref The reactive power reference value is represented by k1 and k2, which represent control coefficients, and 1>k1>k2>0; S represents the total power of the system; P represents the active power at the grid connection point calculated by the system through the measurement module of voltage and current; Δω represents the angular velocity deviation.

[0052] The dynamic dq-axis current limiting control strategy in this scheme can be divided into the following key steps:

[0053] Step 0-1: Detect the key electrical quantities U and I at the grid connection point of new energy sources in the power grid to determine the trigger condition I≥I for current reference value control. max And whether δ'≥δ0' is satisfied, the reference current is pre-allocated during the control period, and P and k1P are judged. ref k2P ref The relationship between Δω and 0 is used to pre-allocate the power reference value during the control period. When the above triggering conditions are met, the system will activate the boosted dq-axis current limiting control strategy and maintain the new control state; if not met, it will continue to maintain the original stable state to ensure that the system is not subject to unnecessary interference.

[0054] Step 0-2: Under the new control state, the dynamic dq-axis current limiting control strategy of this scheme is adopted to redistribute the current reference values ​​of the d-axis and q-axis, as well as the active and reactive power reference values, in order to control the converter system accordingly.

[0055] Step 0-3: Introduce a feedback mechanism of power angle δ' during the control process, which transforms the original static sinusoidal power curve into a dynamic power curve and maintains maximum power output throughout the process. At the same time, combined with the reference power for joint control, the control effect of the system is further enhanced.

[0056] Steps 0-4: The introduction of the new power curve enables the control strategy to automatically recover during a fault, allowing the power angle to return to its initial value δ0'. Regardless of the fault depth, the power angle will automatically return to the initial operating point at a certain time, achieving self-recovery. This effect can be achieved through the control expression given above, and its specific power angle time curve expression is shown below:

[0057]

[0058] Simultaneously, in conjunction with the reference power control strategy, the power deviation during the control period is further reduced, so that the energy required for acceleration and deceleration at the power angle is reasonably distributed.

[0059] Steps 0-5: When the power angle δ' successfully returns to δ0', the boost-type dq-axis current limiting control strategy automatically exits, and the grid-type control strategy switches back to the initial voltage source mode, thereby restoring the normal system operation mode.

[0060] As shown in Figure 1, the control method includes:

[0061] Step 1-1: Calculate the active power and reactive power using the key electrical quantities U and I at the grid connection point of new energy sources in the power grid.

[0062] Steps 1-2: Use this power as the power loop input, and apply the active power equation...

[0063]

[0064] And reactive power equation:

[0065]

[0066] Calculate the power angle δ' and voltage reference value of the power loop output, as well as the angular velocity deviation Δω of the power loop output;

[0067] Steps 1-3: Perform Parker transformation on the obtained power angle δ' and voltage reference value to obtain the dq-axis component of the voltage reference value.

[0068] Steps 1-4: If the triggering condition (I≥ and δ'≥δ0') is not met, the dq axis component of the voltage reference value is used to obtain a PWM signal through the voltage and current double inner loop structure to control the converter output.

[0069] Steps 1-5: If the triggering condition (I≥I) is met by judgment... max If δ'≥δ0'), then the enhanced dq-axis current limiting control strategy takes effect. The dq-axis current reference value control and reference power control are performed through the expression of the enhanced dq-axis current limiting control strategy to obtain the final dq-axis current reference value signal.

[0070] Steps 1-6: Input the dynamically adjusted final dq axis current reference value signal into the current loop to control the current output of the converter and generate the corresponding PWM signal to achieve precise adjustment of the converter;

[0071] Steps 1-7: During the control period, the strategy remains in a hold state until δ'<δ0' is detected. At this point, the dynamic dq-axis current limiting control strategy is exited, and the previous grid-type converter control strategy is restored.

[0072] A dynamic dq-axis current limiting control strategy structure is disclosed to implement the aforementioned control strategy. Figure 2 illustrates the dynamic dq-axis current limiting control strategy structure of this disclosure.

[0073] The structure of this enhanced dq-axis current limiting control strategy includes: an acquisition module, a transformation module, a comparison module, and an adjustment module.

[0074] 1. Acquisition Module: This module is responsible for accurately acquiring the electrical quantity data required for system operation. Specifically, it includes:

[0075] Measure the voltage and current values ​​at the converter grid connection point;

[0076] The frequency deviation Δω of the converter control output is measured through the system active power loop output.

[0077] The phase difference δ0' between the converter grid connection point voltage and the grid voltage is measured through the system active power loop output under normal system conditions.

[0078] By measuring the real-time voltage phase difference δ' after a system fault occurs through the system's active power loop output, the current operating status of the system can be reflected.

[0079] 2. Transformation Module: Used to perform Park transformation on the electrical quantities obtained by the measurement module and the signals before the PWM signal is generated. The voltage and current quantities obtained by the acquisition module are combined with δ' and Park transformed before being input into the double-loop structure.

[0080] 3. Comparison Module: This module compares the electrical quantity data acquired by the acquisition module with preset thresholds, including the triggering conditions of the dynamic dq-axis current control strategy and the reference power structure, to determine whether the control mode needs to be switched. It compares the current and power angle values ​​obtained by the acquisition module to determine the segmented range of the current reference value that should be output. At the same time, it compares the power signal with the corresponding threshold in the formula to obtain the corresponding reference power value control segmented range.

[0081] 4. Adjustment Module: This module is responsible for adjusting the electrical parameters required for system operation. Combining the dynamic dq-axis current limiting control strategy expression and the reference power control strategy expression, it outputs the expression results for the corresponding ranges obtained from the comparison module.

[0082] Figure 4 shows the experimental simulation structure diagram for implementing this embodiment. In this embodiment, based on a grid-type converter, relevant experimental simulations were conducted. To clearly see the effects of dynamic dq-axis current limiting and the boosted dq-axis current limiting control strategy, multi-component sectional control experiments were performed below for effect comparison, further illustrating the control method and effect of this embodiment.

[0083] To explain the effect of the dynamic dq-axis current limiting strategy, the simulation system is shown in Figure 4, and the simulation results of the power angle-time curve after implementing the dynamic dq-axis current limiting control strategy are shown in Figure 5. The system operates stably until 1.0 second. At 1.0 second, a voltage drop fault occurs in the power grid, and the grid voltage drops sharply from a per-unit value of 1.0 to a per-unit value of 0.2, simulating a typical power grid fault scenario.

[0084] As clearly seen in Figure 5(a), the grid-type converter without the dynamic dq-axis current limiting control strategy exhibits significant transient instability after a voltage drop. Specifically, the power angle deviates rapidly, the system cannot quickly recover stability, leading to severe fluctuations in current and voltage. In contrast, Figure 5(b) shows the converter behavior after implementing the dynamic dq-axis current limiting control strategy. After the fault occurs, the converter responds quickly and adjusts the power angle, successfully suppressing the transient fluctuations of the system through limiting control, allowing the power angle to gradually recover to a stable state, and the system exhibits stronger disturbance rejection capability. This result fully demonstrates the effectiveness and advantages of this control strategy in improving the transient stability of the converter.

[0085] Furthermore, the analysis in Figure 5(b) shows that although the power angle does not decrease immediately after the fault is cleared due to the inertial characteristics of the power loop, but rather exhibits inertial response characteristics, indicating that the system has a certain inertial energy storage and delay effect, the control strategy can still ensure that the system eventually stabilizes under a certain inertial effect, avoiding long-term instability. This phenomenon demonstrates the comprehensive capability of the dynamic dq-axis current limiting control strategy in handling system inertia and faults, not only optimizing the instantaneous response but also ensuring that the system can recover smoothly after a fault.

[0086] Figure 6 further illustrates the simulation results of the active power versus power angle curves after implementing the dynamic dq-axis current limiting control strategy. It can be clearly seen that, after adjusting the control strategy, the active power-power angle curve of the converter system changes from a sinusoidal shape in the traditional technique to a horizontal maximum value curve. This change signifies a significant improvement in the stability of the system's power output. The control strategy ensures that the converter can maintain maximum power output under complex fault conditions, avoiding drastic power fluctuations, thereby effectively improving the system's reliability and the stability of the power supply.

[0087] Simulation results fully demonstrate the significant role of the dynamic dq-axis current limiting control strategy in improving the stability of grid-connected converter systems. This strategy not only effectively addresses transient disturbances caused by grid faults but also ensures the safe and reliable operation of the power system.

[0088] To clearly demonstrate the effectiveness of the enhanced dq-axis current limiting control strategy after incorporating the reference power control structure, as well as the drawbacks of dynamic dq-axis current limiting control, another set of simulation experiments was conducted. The simulation system is shown in Figure 4, and the simulation results of the power angle-time curve after implementing the enhanced dq-axis current limiting control strategy are shown in Figure 7. The system was in a stable operating state before 1.0 second. At 1.0 second, a voltage dip fault occurred in the power grid, with the grid voltage dropping sharply from a per-unit value of 1.0 to a per-unit value of 0.2, simulating a typical power grid fault scenario. This simulation aimed to test the converter system's response and stability under fault conditions.

[0089] As shown in Figure 7(a), when the basic dynamic dq-axis current limiting control strategy is implemented, the power angle will continuously increase if a fault occurs in the converter system. Although the power angle recovers to the initial operating point after the first implementation of the dynamic dq-axis current limiting control strategy, the converter system accumulates a large amount of reverse acceleration energy as the control strategy exits, causing the dynamic dq-axis current limiting control strategy to be triggered again at subsequent times. This process can be clearly seen in the current simulation waveform. This repeated control triggering negatively affects the transient stability of the converter, fails to effectively suppress the power angle oscillation of the system, and thus affects the system stability.

[0090] Figure 7(b) shows the simulation results of the power angle-time curve after implementing the enhanced dq-axis current limiting control strategy. By comparing the simulation results before and after the addition of the power reference value control structure, it can be clearly seen that the introduction of the power reference value control structure effectively suppresses excessive oscillation of the power angle, reduces unnecessary power angle fluctuations after a fault, and significantly enhances the stability of the system. Compared with the basic dynamic dq-axis current limiting control strategy, the enhanced strategy can better regulate the power angle fluctuations of the system, avoid repeated triggering of current limiting control, and further improve the transient stability of the system.

[0091] Simulation results of the active power-power angle curves under the implementation of the enhanced dq-axis current limiting control strategy and the dynamic dq-axis current limiting control strategy were compared. It is evident that under the dynamic dq-axis current limiting control strategy, the system experienced two current limiting control triggers, and the power angle oscillation amplitude was large, negatively impacting the stability of the converter system. In contrast, under the enhanced dq-axis current limiting control strategy, the active power-power angle curve of the system was effectively controlled, the power angle oscillation amplitude was significantly reduced, and the stability of the converter system was significantly improved.

[0092] These simulation results demonstrate that the enhanced dq-axis current limiting control strategy has significant advantages in addressing the transient stability problem of converters. By introducing a power reference value control structure, the power angle control process is optimized, effectively improving the system's response speed and stability during faults, avoiding unnecessary oscillations caused by the accumulation of reverse acceleration energy, and thus ensuring the smooth operation of the converter system.

[0093] Finally, the invention is simple to implement and remains effective even when there are multiple converters.

[0094] Those skilled in the art should understand that the above embodiments are merely for illustrative purposes and are not intended to limit the scope of this disclosure. The system capacity, system voltage, line parameters, etc., shown may vary depending on the specific parameters of the power electronic grid-connected generator set and the power grid it is connected to. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications are still within the scope of this disclosure.

Claims

1. A current-limiting-based enhanced transient stability improvement strategy for grid-connected converters, characterized in that: It includes D-CLiS, i.e., dynamic dq-axis current limiting control strategy, and RPCS, i.e., reference power control structure.

2. The enhanced grid-type converter transient stability improvement strategy and system based on current limiting as described in claim 1, characterized in that: The specific control expression for the dynamic dq-axis current limiting control strategy is as follows: in, Indicates the reference value of the d-axis current; Indicates the q-axis current reference value; I dwf Indicates the actual value of the d-axis current; I qref Indicates the actual value of the q-axis current; I max δ0' represents the maximum current limit; I represents the actual current value; δ0' represents the initial operating power angle value of the converter; δ' represents the actual operating power angle value of the converter.

3. The enhanced transient stability improvement strategy for grid-type converters based on current limiting as described in claim 1, characterized in that: The specific control expression for the reference value control structure is as follows: Where, P ref Q represents the reference value for active power in the active power loop; ref The reactive power reference value is represented by k1 and k2, which represent control coefficients, and 1>k1>k2>0; S represents the total power of the system; P represents the active power at the grid connection point calculated by the system through the measurement module of voltage and current; Δω represents the angular velocity deviation.

4. The enhanced transient stability improvement strategy for grid-type converters based on current limiting according to claim 2, characterized in that, The specific control process of the dynamic dq-axis current limiting control strategy includes the following steps: Step 1: Calculate the active power and reactive power using the key electrical quantities U and I at the grid connection point of new energy sources; Step 2: Use this power as the power loop input, and apply it according to the active power equation: And reactive power equation: Calculate the power angle δ' and voltage reference value of the power loop output, as well as the angular velocity deviation Δω of the power loop output; Step 3: Perform a Parker transformation on the obtained power angle δ' and voltage reference value to obtain the dq-axis component of the voltage reference value; Step 4: If the triggering condition (I≥I) is not met, determine if the triggering condition is not met. max And (δ'≥δ0'), then the dq-axis component of the voltage reference value obtains a PWM signal through the voltage and current double inner loop structure to control the converter output; Step 5, if the trigger condition (I≥I) is met by judgment. max If δ'≥δ0'), then the enhanced dq-axis current limiting control strategy takes effect. The dq-axis current reference value control and reference power control are performed through the expression of the enhanced dq-axis current limiting control strategy to obtain the final dq-axis current reference value signal; Step 6: Input the dynamically adjusted final dq-axis current reference value signal into the current loop to control the current output of the converter and generate the corresponding PWM signal to achieve precise adjustment of the converter; Step 7: The strategy is in a hold state during the control period until δ'<δ0' is detected. At this time, the dynamic dq-axis current limiting control strategy is exited, and the previous grid-type converter control strategy is restored.

5. A system using an enhanced grid-type converter transient stability improvement strategy based on current limiting as described in any one of claims 1 to 4, characterized in that, The improved dq-axis current limiting control strategy structure includes: an acquisition module: the acquisition module is responsible for accurately acquiring the electrical quantity data required for system operation; specifically, it includes: measuring the voltage and current values ​​V through the converter grid connection point. abc and I abc and I' abc The active power loop output measures the angular velocity deviation Δω of the system during operation, the phase difference δ'0 between the converter grid connection point voltage and the grid voltage under normal operating conditions, and the real-time voltage phase difference δ'' after a system fault. The conversion module performs Park transformation on the electrical quantities obtained from the measurement module and the signal before PWM signal generation. It combines the voltage and current quantities obtained from the acquisition module with δ' and inputs them into the dual-loop structure. The comparison module compares the electrical quantity data obtained from the acquisition module with preset thresholds, including the trigger conditions of the dynamic dq-axis current control strategy and the reference power structure, to determine whether a control mode switch is needed. It compares the current and power angle values ​​obtained from the acquisition module to determine the current reference value segment interval to be output. It also compares the power signal with the corresponding threshold in the formula to obtain the corresponding reference power value control segment interval. The adjustment module is responsible for adjusting the electrical quantity parameters required for system operation. Combining the dynamic dq-axis current limiting control strategy expression and the reference power control strategy expression, it outputs the expression result of the corresponding interval obtained by the comparison module.

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