An inverter control strategy optimization method and system

Abstract

The application discloses an inverter control strategy optimization method and system, relates to the field of inverter control strategy optimization, and is used for improving the power quality of grid-connected current and the stability of a system. The method comprises the following steps: acquiring a voltage deviation amount and a voltage change rate of a direct-current bus voltage; evaluating the real-time execution capability of a current inner loop; the real-time execution capability comprises a current amplitude range and a current change rate range that can be accepted by the current inner loop; generating original compensation demand according to the voltage deviation amount, the voltage change rate and the real-time execution capability; the original compensation demand is used for compensating the direct-current bus voltage; according to the real-time execution capability, the amplitude and the change rate of the original compensation demand are constrained to obtain a current reference instruction subjected to constraint processing; and the current inner loop adjusts the grid-connected current according to the current reference instruction.

Description

Technical Field

[0001] This invention relates to the field of inverter control strategy optimization, and in particular to an inverter control strategy optimization method and system. Background Technology

[0002] In the normal operation of photovoltaic grid-connected inverters, a dual-loop control structure consisting of an outer voltage loop and an inner current loop is typically employed. The outer voltage loop generates a reference current command based on the deviation of the DC bus voltage, and the inner current loop tracks this command to adjust the grid-connected current, thereby maintaining stable DC bus voltage and good power quality under normal, slow changes in sunlight. However, in the actual operation of photovoltaic power plants, rapid cloud cover is frequently encountered, causing a sharp drop in photovoltaic input power on the order of seconds or even sub-seconds.

[0003] In this rapid power compensation scenario, due to the sudden drop in input power, the DC-side capacitor must discharge rapidly to maintain power balance, causing the DC bus voltage to drop at an extremely high slope. This rapid change in physical voltage is sensed by the outer voltage loop, and the conventional linear amplification logic directly generates a large-amplitude active current command with an extremely steep leading edge based on the sudden increase in voltage error. Because the drastic change in this command completely exceeds the linear tracking capability of the inner current loop, it directly causes the inner current loop error to saturate instantaneously, rapidly pushing the modulation wave of the driving power switching devices into the overmodulation region or even saturation state.

[0004] At this point, the inverter loses precise control over the output voltage vector, and the actual AC current surges uncontrollably towards the huge command value. This not only generates severe current overshoot and high-frequency oscillations, leading to a sharp increase in grid-connected current harmonics, but also significantly reduces the system's small-signal stability margin. Existing conventional control methods mainly rely on linear adjustment of the absolute value of voltage deviation, making it difficult to balance the pursuit of rapid response to suppress voltage drops with maintaining stable current loop tracking. They lack a dynamic coordination mechanism based on the severity of voltage drops, easily translating high-slope changes in physical quantities into uncontrolled commands in the control logic. Therefore, in scenarios where photovoltaic grid-connected inverters deal with rapid input power drops caused by cloud cover, when the DC bus voltage drops at a high slope, the conventional voltage outer loop's linear amplification logic for sudden voltage errors does not consider the impact of the DC-side voltage drop rate on the current command impact. This causes instantaneous saturation of the current inner loop command, triggering severe grid-connected current overshoot and oscillations. Consequently, the inverter may disconnect from the grid due to overcurrent protection or excessive harmonics, interrupting power conversion. Summary of the Invention

[0005] This application discloses an inverter control strategy optimization method and system, which aims to solve the problem that in the scenario of rapid input power drop caused by cloud obstruction in photovoltaic grid-connected inverters, the conventional voltage outer loop linear amplification logic for sudden voltage error does not consider the impact of DC side voltage drop rate on current command impact, resulting in instantaneous saturation of current inner loop command, causing serious overshoot and oscillation of grid-connected current, which in turn can easily lead to inverter disconnection from the grid due to overcurrent protection or excessive harmonics, interrupting power conversion.

[0006] In a first aspect, this application discloses an inverter control strategy optimization method, comprising the following steps: Obtain the voltage deviation and rate of change of the DC bus voltage; Evaluate the real-time execution capability of the current inner loop; this real-time execution capability includes the range of current amplitude and the range of current change rate that the current inner loop can handle. Based on the voltage deviation, the voltage change rate, and the real-time execution capability, an initial compensation requirement is generated; this initial compensation requirement is used to compensate the DC bus voltage. Based on this real-time execution capability, the amplitude and rate of change of the original compensation requirement are constrained to obtain a constrained current reference command; The inner current loop adjusts the grid-connected current according to the current reference command.

[0007] Optionally, the current amplitude range is determined, including: Obtain the DC bus voltage, AC grid voltage, and filter inductance value; Calculate the modulation coefficient based on the DC bus voltage, AC grid voltage, and filter inductance value; The current amplitude range is determined based on the modulation coefficient and the DC bus voltage.

[0008] Optionally, the range of current change rate is determined, including: Obtain the DC bus voltage and the filter inductance value; The range of current change rate is determined based on the filter inductance value and the DC bus voltage.

[0009] Optionally, based on the voltage deviation, voltage change rate, and real-time execution capability, the original compensation requirements are generated, including: The system state is determined based on the voltage deviation, voltage change rate, and real-time execution capability; the system state includes normal compensation state and limited compensation state. When the system is in the normal compensation state, the voltage deviation is used as the input, and after calculation with a fixed proportional coefficient and integral coefficient, the output current reference value is obtained to obtain the original compensation requirement. When the system is under limited compensation, the current compensation amount is calculated based on the voltage change rate and the equivalent parameters of the DC bus capacitance to obtain the original compensation requirement.

[0010] Optionally, the system state can be determined based on the voltage deviation, voltage change rate, and real-time execution capability, including: Based on the real-time execution capability, determine whether the current inner loop modulation margin is greater than the margin threshold. When the first preset condition is met, the system state is determined to be the normal compensation state; the first preset condition includes: the voltage deviation is less than the deviation threshold, the voltage change rate is lower than the change rate threshold, and the current inner loop modulation margin is greater than the margin threshold. When the first preset condition is not met, the system state is determined to be a limited compensation state.

[0011] Optionally, the inner current loop adjusts the grid-connected current according to the current reference command, including: Continuously acquire the actual tracking status of the inner current loop; the actual tracking status includes current tracking error and modulation coefficient; Adjust the current reference command according to the actual tracking status; The inner current loop adjusts the grid-connected current according to the adjusted current reference command.

[0012] Optionally, the current reference command can be adjusted according to the actual tracking status, including: If the integral of the absolute value of the current tracking error exceeds the set tolerance threshold or the modulation coefficient is greater than the preset threshold within N consecutive control cycles, a callback factor is generated; N is a preset positive integer. The current reference command is adjusted based on the callback factor.

[0013] Optionally, if the integral of the absolute value of the current tracking error exceeds a set tolerance threshold, or the modulation coefficient is greater than a preset threshold, a callback factor is generated, including: If the integral of the absolute value of the current tracking error exceeds the set tolerance threshold, or the modulation coefficient is greater than the preset threshold, an initial callback factor is generated. The real-time rate of change of DC bus voltage, the real-time rate of change of AC grid voltage, and the real-time rate of change of switching frequency are obtained. The equivalent bandwidth of the inner current loop is calculated based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency. Based on the equivalent bandwidth, the upper limit of the rate of change of the initial callback factor and the recovery slope of the initial callback factor are adjusted to generate the callback factor.

[0014] Optionally, the equivalent bandwidth of the inner current loop is calculated based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency, including: Adjust the inductance and resistance parameters in the current inner loop model based on the real-time rate of change of DC bus voltage, the real-time rate of change of AC grid voltage, and the real-time rate of change of switching frequency. Based on the adjusted current inner loop model, the equivalent bandwidth of the current inner loop is calculated.

[0015] Secondly, this application also discloses an inverter control strategy optimization system, which includes: The status information acquisition module is used to acquire the voltage deviation and voltage change rate of the DC bus voltage. The execution capability assessment module is used to evaluate the real-time execution capability of the current inner loop; the real-time execution capability includes the range of current amplitude and the range of current change rate that the current inner loop can handle. The original compensation requirement generation module is used to generate original compensation requirements based on voltage deviation, voltage change rate, and real-time execution capability; the original compensation requirements are used to compensate for DC bus voltage. The instruction constraint processing module is used to constrain the amplitude and rate of change of the original compensation requirement based on the real-time execution capability, and obtain a constrained current reference instruction. The current regulation module is used to adjust the grid-connected current in the inner current loop according to the current reference command.

[0016] Beneficial Effects: This application provides a method for optimizing inverter control strategies. This method acquires the voltage deviation and rate of change of the DC bus voltage and evaluates the real-time execution capability of the current inner loop (including the current amplitude range and rate of change range), comprehensively considering the current system state and the actual carrying capacity of the current inner loop. Based on this, an initial compensation demand is generated using this information, and the amplitude and rate of change of the initial compensation demand are constrained according to the real-time execution capability of the current inner loop, resulting in a constrained current reference command. Finally, the current inner loop adjusts the grid-connected current according to this command.

[0017] Through the above technical solution, this application effectively solves the problem in the prior art where, when photovoltaic input power drops rapidly, the conventional outer voltage loop fails to consider the impact of the DC-side voltage drop rate on the current command, leading to instantaneous saturation of the inner current loop command and causing severe overshoot and oscillation of the grid-connected current. This application, by introducing an assessment of the real-time execution capability of the inner current loop and dynamic constraints on the compensation command, avoids the runaway of traditional linear amplification logic under extreme conditions. This allows the inverter to maintain stable tracking of the inner current loop even when facing high-slope voltage drops, suppressing grid-connected current overshoot and high-frequency oscillation, significantly improving the power quality of the grid-connected current and the stability of the system. Therefore, this application can effectively prevent the inverter from disconnecting from the grid due to overcurrent protection or excessive harmonics, ensuring the continuity and reliability of power conversion, and demonstrating significant and superior technical effects. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of an inverter control strategy optimization method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another inverter control strategy optimization method provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of an inverter control strategy optimization system provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] To better understand the technical solution proposed in this application, some key terms involved will be explained first.

[0022] The DC bus voltage refers to the voltage on the DC side of the inverter, and its stability is crucial for the normal operation of the inverter. Voltage deviation refers to the difference between the actual and expected values ​​of the DC bus voltage, while the voltage change rate reflects how quickly the DC bus voltage changes. The current inner loop is an important component of the inverter control system, responsible for adjusting the grid-connected current according to reference commands to achieve precise power control. Real-time execution capability is the range of current amplitude and change rate that the current inner loop can effectively track under current operating conditions; it reflects the dynamic response limit of the current inner loop. The original compensation requirement is the theoretical current requirement used to compensate for the DC bus voltage, calculated based on the DC bus voltage deviation and change rate. The constrained current reference command is the actual current command after the original compensation requirement has been constrained by the real-time execution capability of the current inner loop, ensuring that the current inner loop can effectively track the current.

[0023] The following specific embodiments will provide a detailed introduction and explanation of an inverter control strategy optimization method provided in this application.

[0024] Reference Figure 1 This invention provides a method for optimizing inverter control strategies, comprising the following steps: S1, obtains the voltage deviation and voltage change rate of the DC bus voltage.

[0025] For example, the DC bus voltage can be measured in real time by setting a voltage sensor in the inverter control system, and then sampled and calculated by a digital signal processor (DSP). For example, the voltage deviation can be obtained by comparing the real-time measured DC bus voltage with a preset reference voltage, while the rate of voltage change can be obtained by performing differential operations on the DC bus voltage or by estimating it using a first-order low-pass filter.

[0026] S2. Evaluate the real-time execution capability of the inner current loop.

[0027] The real-time execution capability includes the range of current amplitude and the range of current change rate that the inner current loop can handle.

[0028] The current amplitude range can be determined based on the inverter's hardware limitations, such as the maximum current carrying capacity of power devices and the saturation current of the filter inductor. Alternatively, it can be determined by real-time calculation of the inverter's maximum modulation coefficient under the current DC bus voltage, AC grid voltage, and filter inductor value. For example, when the modulation coefficient approaches 1, the linear operating range of the inner current loop is limited, thus affecting the current amplitude it can handle. The current change rate range can be determined based on the dynamic response characteristics of the inner current loop, such as the current loop bandwidth, sampling frequency, and the controller's computing power. For example, the maximum current change rate under different operating conditions can be determined by analyzing the transfer function of the inner current loop or through experimental testing.

[0029] S3. Generate the original compensation requirements based on the voltage deviation, voltage change rate, and real-time execution capability.

[0030] The original compensation requirement is used to compensate for the DC bus voltage.

[0031] For example, a traditional PI controller can be used, taking the voltage deviation as input, performing proportional and integral calculations, and outputting a current reference value as the initial compensation requirement. In some cases, the voltage change rate can also be incorporated, using feedforward control to quickly respond to drastic voltage changes, thereby generating a more accurate initial compensation requirement.

[0032] S4. Based on the real-time execution capability, constrain the amplitude and rate of change of the original compensation requirement to obtain a constrained current reference command.

[0033] For example, if the magnitude of the initial compensation demand exceeds the current amplitude range that the inner current loop can handle, the magnitude of the initial compensation demand needs to be limited within that range. Similarly, if the rate of change of the initial compensation demand exceeds the current rate of change range that the inner current loop can handle, the rate of change of the initial compensation demand needs to be limited, for example, by using a ramp function or limiter to smooth its change. In this way, it can be ensured that the generated current reference command can be effectively tracked by the inner current loop, avoiding command saturation.

[0034] S5. The inner current loop adjusts the grid-connected current according to the current reference command.

[0035] The inner current loop typically employs a proportional-integral (PI) controller or a proportional-resonant (PR) controller to achieve accurate tracking of the grid-connected current. Based on the error between the current reference command and the actual grid-connected current, the controller generates a corresponding modulation signal to drive the inverter's power switching devices, thereby adjusting the grid-connected current to maintain consistency with the reference command.

[0036] The inverter control strategy optimization method proposed in this application effectively solves the grid-connected current overshoot and oscillation problems caused by command saturation in scenarios where photovoltaic input power drops rapidly. This is achieved by introducing an assessment of the real-time execution capability of the current inner loop and dynamically constraining the original compensation requirements based on this assessment. Compared with the linear adjustment method in existing technologies that mainly rely on the absolute value of voltage deviation, the solution proposed in this application can dynamically coordinate the relationship between rapid response and stable tracking based on the severity of the DC bus voltage drop and the actual capability of the current inner loop. For example, when the DC bus voltage drops rapidly, this application can identify the carrying limit of the current inner loop and reasonably limit the current command, avoiding the current inner loop saturation and runaway caused by excessively large or steep commands in traditional solutions. As a result, this application significantly improves the operating stability, reliability, and power quality of the inverter under complex operating conditions, effectively preventing the inverter from disconnecting from the grid due to overcurrent protection or excessive harmonics, thereby ensuring the continuity of power conversion.

[0037] like Figure 2 As shown, specifically, determining the current amplitude range includes: S101: Obtain the DC bus voltage, AC grid voltage, and filter inductance value.

[0038] Specifically, the DC bus voltage refers to the input voltage on the DC side of the inverter, and its value is affected by power supply fluctuations or load changes. The AC grid voltage refers to the AC grid voltage to which the inverter is connected, and its amplitude and frequency are usually determined by the grid characteristics. The filter inductance value refers to the parameter of the inductor element used to filter out high-frequency harmonics on the inverter output side.

[0039] S102. Calculate the modulation coefficient based on the DC bus voltage, AC grid voltage, and filter inductance value.

[0040] The modulation factor is a key parameter in inverter control, reflecting the relationship between the inverter output voltage and the DC bus voltage. It is typically used to limit the amplitude of the inverter output voltage to avoid overmodulation. The modulation factor can be calculated based on principles such as instantaneous power balance and voltage space vector modulation (SVPWM), combined with the DC bus voltage, AC grid voltage, and filter inductance value. For example, in SVPWM, the modulation factor is closely related to the amplitudes of both the DC bus voltage and the AC output voltage.

[0041] S103. Determine the current amplitude range based on the modulation coefficient and the DC bus voltage.

[0042] Once the modulation index is calculated, the maximum current amplitude that the inner current loop can handle can be determined by combining it with the DC bus voltage. This is because the inverter's output capability is limited by both the DC bus voltage and the modulation index. When the modulation index reaches its maximum value, the maximum AC current amplitude that the inverter can output also reaches its theoretical upper limit.

[0043] The proposed solution obtains key electrical parameters of the inverter operation, namely the DC bus voltage, AC grid voltage, and filter inductance value, enabling precise calculation of the inverter's current modulation coefficient. The modulation coefficient directly reflects the effective utilization rate and maximum output capacity of the inverter's output voltage under current operating conditions. By combining this modulation coefficient with the DC bus voltage, the maximum current amplitude that the inner current loop can withstand without overmodulation or saturation can be accurately derived. This dynamic evaluation based on actual operating parameters ensures that the determination of the current amplitude range is real-time and accurate, thus providing a reliable basis for subsequent current reference command constraints.

[0044] In some embodiments described above in this application, evaluating the real-time execution capability of the current inner loop is one of the key steps in optimizing the inverter control strategy. Specifically, the step of determining the current change rate range when evaluating the real-time execution capability of the current inner loop may include the following.

[0045] S201, obtain the DC bus voltage and the filter inductance value.

[0046] The DC bus voltage refers to the voltage on the DC side of the inverter, and its value directly affects the inverter's ability to output AC current. The filter inductance value refers to the parameter of the inductor in the AC side filter circuit of the grid-connected inverter, and this inductor plays a key role in limiting the rate of change of current.

[0047] S202. Determine the range of current change rate based on the filter inductance value and the DC bus voltage.

[0048] Specifically, determining the current rate of change range is achieved by analyzing the inverter's dynamic response capability under a given DC bus voltage and filter inductance value. In practical applications, the response speed and stability of the inner current loop are directly constrained by these physical parameters. For example, when the DC bus voltage is high, the inverter can provide a larger voltage margin, allowing the grid-connected current to change at a faster rate; conversely, when the DC bus voltage is low, the current rate of change will be limited. Simultaneously, a larger filter inductance value strongly impedes current changes, resulting in a slower current rate of change; a smaller filter inductance value results in a faster current rate of change, but may introduce greater ripple. Therefore, by comprehensively considering the DC bus voltage and filter inductance value, the maximum current rate of change that the inner current loop can withstand under current operating conditions can be accurately calculated, thus obtaining the current rate of change range.

[0049] The proposed solution accurately reflects the dynamic response capability of the current inner loop by obtaining the DC bus voltage and the filter inductance value, and determining the current change rate range based on these parameters. The DC bus voltage determines the upper limit of the inverter output voltage, while the filter inductance value directly affects the rate of change of current across the inductor. Therefore, using these two key parameters, the maximum rate of change of current achievable by the current inner loop under unsaturated or undistorted conditions can be calculated. This method of determination based on actual physical parameters makes the evaluation of the real-time execution capability of the current inner loop more accurate and reliable, avoiding performance degradation or system instability caused by blind or empirical settings.

[0050] Specifically, the original compensation requirements are generated based on the voltage deviation, voltage change rate, and real-time execution capability, and different strategies can be adopted depending on the system state.

[0051] The above-mentioned original compensation requirements are generated based on the voltage deviation, voltage change rate, and real-time execution capability, including: S301. Determine the system status based on the voltage deviation, voltage change rate, and real-time execution capability.

[0052] The system status includes normal compensation status and limited compensation status.

[0053] Specifically, based on real-time execution capability, it can be determined whether the current inner loop modulation margin is greater than the margin threshold; when the first preset condition is met, the system state is determined to be the normal compensation state; the first preset condition includes: the voltage deviation is less than the deviation threshold, the voltage change rate is lower than the change rate threshold, and the current inner loop modulation margin is greater than the margin threshold; when the first preset condition is not met, the system state is determined to be the limited compensation state.

[0054] Specifically, real-time execution capability refers to the range of current amplitude and current change rate that the current inner loop can handle under current operating conditions, reflecting the actual operating margin of the current inner loop. The current inner loop modulation margin can be understood as the margin between the output modulation signal and the maximum modulation signal without saturation; its magnitude directly reflects the control capability and potential overload risk of the current inner loop. The margin threshold is a preset reference value used to determine whether the current inner loop modulation margin is sufficient. When the modulation margin is lower than this threshold, it indicates that the current inner loop may be close to saturation or already in a limited state.

[0055] The first precondition is a comprehensive judgment criterion used to identify a relatively stable system operating in a normal state with sufficient margin in the current inner loop. Specifically, a voltage deviation less than a deviation threshold means the deviation between the DC bus voltage and the expected value is within an acceptable range; a voltage change rate lower than a change rate threshold indicates a smooth trend in the DC bus voltage change, and the system has not experienced drastic disturbances; and a current inner loop modulation margin greater than a margin threshold ensures sufficient space for the current inner loop to execute compensation commands, avoiding control failure due to inner loop saturation. When all three conditions are met, the system is judged to be in a normal compensation state, at which point a more aggressive compensation strategy can be adopted. Conversely, if any condition is not met, the system is judged to be in a restricted compensation state, requiring a switch to a more conservative or adaptive compensation strategy.

[0056] This application's solution introduces a multi-dimensional system state judgment mechanism by assessing the modulation margin of the current inner loop and combining it with voltage deviation and voltage change rate. When the DC bus voltage deviation and change rate are both within a small range, and the current inner loop still has sufficient modulation margin, it indicates that the system is in a relatively stable normal operating condition. At this time, the current inner loop is capable of responding to larger compensation demands, so a conventional compensation strategy can be adopted. However, once the voltage deviation or change rate exceeds a preset threshold, or the modulation margin of the current inner loop is insufficient, it means that the system may face significant disturbances or the current inner loop is approaching its operating limit. In this case, if a conventional compensation strategy is still adopted, it may lead to current inner loop saturation, thereby causing grid current distortion or system instability. By timely switching the system state to a limited compensation state, a more conservative or adaptive compensation algorithm can be triggered. For example, in the limited compensation state, the current compensation amount can be calculated based on the voltage change rate and the equivalent parameters of the DC bus capacitance, thereby avoiding excessive demands on the current inner loop, effectively preventing inner loop saturation, and ensuring stable inverter operation.

[0057] S302. When the system is in the normal compensation state, the voltage deviation is used as the input, and after calculation with a fixed proportional coefficient and integral coefficient, the current reference value is output to obtain the original compensation requirement.

[0058] Specifically, under normal compensation conditions, the initial compensation demand is generated using a proportional-integral (PI) control strategy based on the voltage deviation. The voltage deviation serves as the input to the PI controller, which performs calculations using fixed proportional and integral coefficients to output a current reference value. This approach can smoothly and accurately track the DC bus voltage deviation and provide the corresponding compensation current.

[0059] Under limited compensation conditions, traditional PI control may fail to respond promptly due to the system's potential for emergency or rapidly changing operating conditions. Therefore, this application employs a compensation strategy based on the voltage change rate. By combining the voltage change rate with the equivalent parameters of the DC bus capacitance, the required current compensation can be directly calculated. This method can respond more quickly to rapid changes in the DC bus voltage, providing immediate current compensation to prevent further voltage degradation.

[0060] This application's solution introduces system state judgment, enabling the generation of original compensation requirements to adaptively adjust according to actual operating conditions. Under normal compensation conditions, PI control based on voltage deviation achieves accurate and stable compensation of the DC bus voltage, ensuring stable system operation. When the system enters a limited compensation state, such as when the DC bus voltage fluctuates drastically, traditional PI control may be ineffective due to response speed limitations. In this case, switching to a compensation strategy based on the rate of voltage change allows for the rapid calculation of the required compensation current using the trend information of voltage changes and the equivalent parameters of the DC bus capacitor, thereby suppressing drastic voltage fluctuations in a short time. This state-specific compensation strategy enables the inverter to provide efficient and stable DC bus voltage compensation under various operating conditions.

[0061] In some preferred embodiments, a specific example is given below. Assume that during inverter operation, the system continuously monitors the DC bus voltage deviation, voltage change rate, and current inner loop modulation margin. For example, at a certain moment, a voltage deviation of 0.5V is detected (less than the preset deviation threshold of 1V), a voltage change rate of 0.1V / ms (less than the preset change rate threshold of 0.5V / ms), and a current inner loop modulation margin of 15% (greater than the preset margin threshold of 10%). Since all three conditions are met, the system is determined to be in a normal compensation state. At this time, the inverter control system will use the voltage deviation as input, perform a fixed proportional-integral (PI) calculation, output a current reference value, and generate the original compensation requirement. However, at a subsequent moment, a transient disturbance in the power grid causes a rapid drop in the DC bus voltage. At this point, a voltage deviation of 2V is detected (greater than the deviation threshold of 1V), and the voltage change rate is 1V / ms (greater than the change rate threshold of 0.5V / ms). Even though the current inner loop modulation margin remains at 12% (greater than the margin threshold of 10%), the system is still classified as under limited compensation because the voltage deviation and voltage change rate conditions in the first preset condition are not met. In this limited state, the inverter control system calculates the current compensation amount based on the equivalent parameters of the voltage change rate and the DC bus capacitance, generating the original compensation requirement. This allows for a more conservative compensation strategy to avoid excessive burden on the current inner loop and ensure system stability. For example, in another scenario, both the voltage deviation and voltage change rate are within the thresholds, but due to prolonged high-power output, the current inner loop modulation margin drops to 8% (less than the margin threshold of 10%). In this case, the system is also classified as under limited compensation, switching to a limited compensation strategy to prevent current inner loop saturation.

[0062] In some existing technologies, after the inverter control strategy generates and constrains a current reference command, the inner current loop directly adjusts the grid-connected current according to this command. However, in actual operation, due to the complexity of the grid environment, dynamic changes in system parameters, or limitations of the inverter's own operating state, the inner current loop may deviate when tracking the current reference command, or may even fail to track effectively due to the modulation coefficient reaching saturation, thus affecting the regulation accuracy of the grid-connected current and the stability of the system. If the above problems are not solved, it may lead to poor DC bus voltage compensation and even cause system oscillation. To address this, this application further proposes an optimization scheme, which monitors the actual operating state of the inner current loop in real time and dynamically adjusts the current reference command accordingly to ensure that the inner current loop can perform the current regulation task more accurately and stably.

[0063] In this regard, this application further proposes that the steps for the aforementioned inner current loop to adjust the grid-connected current according to the aforementioned current reference command include: S401, continuously acquire the actual tracking status of the inner current loop.

[0064] The actual tracking status includes current tracking error and modulation coefficient.

[0065] Specifically, continuously acquiring the actual tracking status of the current inner loop refers to real-time monitoring of the current inner loop's operating performance within each or multiple control cycles of the inverter control. The current tracking error can be understood as the difference between the actual output current of the current inner loop and the target current reference command, reflecting the tracking accuracy of the current inner loop. The modulation coefficient is the ratio of the amplitude of the modulation signal used by the inverter to convert DC voltage to AC voltage to the amplitude of the DC bus voltage, reflecting the utilization rate and margin of the inverter's output voltage.

[0066] When the modulation coefficient approaches or reaches its upper limit, it indicates that the inverter may be in a saturated state, making it difficult to further increase the output voltage, thus limiting the regulation capability of the inner current loop.

[0067] S402. Adjust the current reference command according to the actual tracking status.

[0068] In practical applications, adjusting the current reference command based on the actual tracking status refers to correcting the original current reference command based on real-time feedback of the current tracking error and modulation coefficient. For example, when the current tracking error is too large, the amplitude or rate of change of the current reference command can be appropriately reduced to avoid overloading the inner current loop; when the modulation coefficient is close to saturation, the current reference command can also be adjusted to provide sufficient modulation margin for the inverter, preventing it from entering the nonlinear operating region. The purpose is to ensure that the inner current loop always operates stably within a controllable range and to improve its tracking accuracy of the current reference command.

[0069] S403, the inner current loop adjusts the grid-connected current according to the adjusted current reference command.

[0070] This application's solution effectively solves the problem in traditional solutions where the current inner loop may fail to accurately track the current reference command due to external disturbances or its own limitations by introducing a continuous monitoring and feedback adjustment mechanism for the actual tracking status of the current inner loop. Specifically, when the current inner loop adjusts the grid-connected current, its actual tracking status (including current tracking error and modulation coefficient) is acquired in real time. If a large current tracking error is detected, it indicates that the current inner loop has failed to effectively track the command, or the modulation coefficient is close to saturation, indicating that the inverter is about to reach its output limit. At this time, the system dynamically adjusts the original current reference command based on this actual tracking status information. This adjustment can be to reduce the amplitude of the command, slow down its rate of change, or provide a backoff mechanism when the modulation coefficient is saturated, thereby providing the current inner loop with a command that is easier to track and more in line with its current execution capability. It is precisely because of this closed-loop feedback adjustment that the current inner loop can avoid runaway or performance degradation caused by overly aggressive commands or changes in external conditions, thus ensuring the stability and accuracy of the grid-connected current.

[0071] In some preferred embodiments, a specific example is given below. Suppose that at a certain moment, due to a sudden drop in grid voltage, the DC bus voltage experiences a significant deviation. The system generates a large initial compensation demand based on the voltage deviation and its rate of change, and after real-time execution capability constraints, obtains a current reference command. However, due to harmonic interference on the grid side, or slight drifts in inverter internal parameters, the inner current loop generates a continuous and non-negligible current tracking error when attempting to track the current reference command. Simultaneously, to quickly respond to the compensation demand, the modulation coefficient of the inner current loop may be pushed close to saturation. In this situation, the solution of this application continuously acquires the actual tracking status of the inner current loop. Once the system detects that the absolute integral of the current tracking error exceeds a set tolerance threshold, or that the modulation coefficient is greater than a preset threshold, it recognizes that the tracking performance of the inner current loop is declining or about to reach its limit. At this time, the system adjusts the current reference command based on this actual tracking status information. For example, a callback factor can be generated, and based on this callback factor, the amplitude of the current reference command can be appropriately reduced or its rate of change limited. In this way, the adjusted current reference command becomes more "mild" and better matches the current inner loop's current execution capability. The current inner loop then adjusts the grid-connected current according to this adjusted command, thereby avoiding overshoot, oscillation, or saturation caused by blindly pursuing the original command, ensuring stable grid-connected current output and effective compensation of DC bus voltage.

[0072] In some embodiments described above, a scheme is proposed whereby the inner current loop adjusts the current reference command based on the actual tracking state. However, in actual operation, when the tracking performance of the inner current loop is poor, such as when a large current tracking error occurs or the modulation coefficient approaches saturation, a simple adjustment strategy may not be able to correct the system state in a timely and effective manner, and may even lead to a decrease in control performance or system instability. To address this, this application further proposes a specific method for adjusting the current reference command by introducing a callback factor to optimize the adjustment process of the current reference command in a more intelligent and robust way.

[0073] The above adjustments to the current reference command based on the actual tracking status specifically include: S501. If the integral of the absolute value of the current tracking error exceeds the set tolerance threshold or the modulation coefficient is greater than the preset threshold within N consecutive control cycles, a callback factor is generated.

[0074] Here, "N consecutive control cycles" refers to the system continuously monitoring the actual tracking status of the inner current loop over a period of time, rather than making judgments based solely on instantaneous values. This continuous judgment helps avoid misjudgments caused by instantaneous disturbances, ensuring that the adjustment mechanism is triggered only when the system actually experiences a persistent tracking problem or approaches its operating limits. N, as a preset positive integer, can be configured according to the specific system dynamic characteristics and control requirements to balance response speed and stability.

[0075] The absolute integral of the current tracking error is an important indicator for measuring the performance of the inner current loop tracking. Current tracking error refers to the deviation between the actual grid-connected current and the current reference command. Integrating its absolute value reflects the cumulative degree of persistent deviation in current tracking. When this integral value exceeds the set tolerance threshold, it indicates that the tracking performance of the inner current loop has continued to deteriorate, requiring strong corrective measures.

[0076] The modulation factor reflects the inverter's output voltage capacity utilization. When the modulation factor approaches or exceeds the preset threshold, it means that the inverter is approaching its voltage output limit and may no longer be able to effectively respond to changes in the current reference command, or may even enter an overmodulation state, resulting in distortion of the output current waveform.

[0077] When any of the above conditions are met, a "callback factor" is generated. This callback factor is a parameter used to correct the current reference command. Its function is to guide the current reference command to adjust in a direction that makes it easier for the inner current loop to track, such as reducing its amplitude or limiting its rate of change.

[0078] S502. Adjust the current reference command based on the callback factor.

[0079] By "adjusting the current reference command based on the callback factor", the current reference command can be made more consistent with the actual execution capability of the inner current loop, thereby improving the overall control performance of the system.

[0080] This application addresses the limitations of simple adjustment strategies in basic schemes by introducing a continuous monitoring and conditional judgment mechanism for the actual tracking state of the current inner loop. Specifically, when the tracking error of the current inner loop accumulates continuously, or the inverter modulation coefficient approaches saturation, it indicates that the current inner loop may already be in or about to enter a state that is difficult to control effectively. At this time, if the original current reference command is continued to be adjusted, it may lead to further deterioration of system performance. This application judges the absolute value integral of the current tracking error and the modulation coefficient over N consecutive control cycles. Once it is found that the error exceeds a preset threshold, a callback factor is actively generated. This callback factor can correct the current reference command, such as appropriately reducing the amplitude of the current reference command or limiting its rate of change, thereby providing greater margin for the current inner loop, enabling it to recover from poor tracking states and preventing the inverter from entering a deep saturation or runaway state. It is precisely because of this intelligent feedback and correction mechanism based on the actual operating state of the system that the current inner loop can regulate the grid-connected current more stably and efficiently.

[0081] In some preferred embodiments, a specific example is given below. Assume that in a grid-connected inverter system, the inner current loop is regulating the grid-connected current. Over N consecutive control cycles, the system continuously monitors the absolute integral of the current tracking error and the modulation coefficient. For example, when the grid voltage suddenly drops, causing the inverter to need to output a larger reactive current to support the grid voltage, the inner current loop may experience a large tracking error. If the absolute integral of the current tracking error continues to accumulate and exceeds a set tolerance threshold, or if the inverter increases the modulation coefficient to output the required current and exceeds a preset threshold (e.g., 0.95), the system will determine that the current inner current loop's execution capability is limited. At this point, the control system generates a callback factor. This callback factor can be a multiplicative coefficient less than 1 or a negative compensation amount. For example, if the callback factor is designed to reduce the amplitude of the current reference command by 5%, or limit its rate of change to half of its original value, the original current reference command will be adjusted based on this callback factor, making the adjusted current reference command's amplitude or rate of change more consistent with the actual carrying capacity of the current inner current loop. The inner current loop then adjusts the grid-connected current according to this adjusted current reference command, thereby avoiding system instability or overmodulation caused by blindly pursuing the original command, and ensuring stable operation and rapid recovery of the inverter in the event of a grid fault.

[0082] In some embodiments described above in this application, a scheme is proposed to generate a callback factor based on the actual tracking state of the inner current loop (including current tracking error and modulation coefficient), and to adjust the current reference command based on this callback factor. However, in its implementation, if the callback factor generation mechanism fails to fully consider the real-time dynamic operating conditions of the inverter, such as the real-time changes in key parameters like DC bus voltage, AC grid voltage, and switching frequency, the callback factor adjustment may be untimely or inaccurate. This limitation may result in poor adjustment of the current reference command, especially when the system faces rapidly changing disturbances, and may even trigger system oscillations or instability, thereby affecting the inverter's stability and grid-connected power quality.

[0083] In this regard, this application further proposes that if the absolute integral of the current tracking error exceeds a set tolerance threshold, or the modulation coefficient is greater than a preset threshold, a callback factor is generated, including: S601. If the integral of the absolute value of the current tracking error exceeds the set tolerance threshold, or the modulation coefficient is greater than the preset threshold, then an initial callback factor is generated.

[0084] Specifically, when the actual tracking status of the inner current loop (including current tracking error and modulation coefficient) indicates a decline in system performance, such as when the absolute integral of the current tracking error exceeds a set tolerance threshold or the modulation coefficient is greater than a preset threshold, an initial callback factor will be generated first. This initial callback factor is intended to provide an initial indication that the current reference command needs to be adjusted.

[0085] S602. Obtain the real-time rate of change of DC bus voltage, the real-time rate of change of AC grid voltage, and the real-time rate of change of switching frequency.

[0086] To ensure more accurate generation of the callback factor and better adaptability to real-time operating conditions, it is necessary to obtain the real-time rate of change of the DC bus voltage, the AC grid voltage, and the switching frequency. The real-time rate of change of the DC bus voltage reflects the dynamic balance of energy on the DC side; the real-time rate of change of the AC grid voltage reflects the degree of disturbance or change in the grid; and the real-time rate of change of the switching frequency is closely related to the switching losses and control bandwidth of the inverter's power devices. These real-time rates of change are key indicators for evaluating the system's dynamic performance and the actual response capability of the current inner loop.

[0087] S603. Calculate the equivalent bandwidth of the inner current loop based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency.

[0088] Specifically, the inductance and resistance parameters in the current inner loop model can be adjusted based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency. Based on the adjusted current inner loop model, the equivalent bandwidth of the current inner loop is calculated.

[0089] Specifically, the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency refer to the instantaneous trends and magnitudes of these key electrical quantities over a short period of time during inverter operation. These rates of change reflect the dynamic characteristics of the system's operating environment and conditions. Adjusting the inductance and resistance parameters in the current inner loop model can be understood as dynamically correcting the inductance and resistance values ​​in the equivalent circuit model upon which the current inner loop depends, based on the aforementioned real-time rates of change. For example, in practical applications, the actual values ​​of the filter inductance and line resistance may undergo slight changes due to factors such as temperature and frequency, which can affect the dynamic response of the current inner loop. By monitoring these rates of change in real time, preset mapping relationships, lookup tables, or adaptive algorithms can be used to dynamically update the inductance and resistance parameters in the current inner loop model, making it closer to actual operating conditions. The aim is to enable the current inner loop model to more accurately reflect the actual physical characteristics of the inverter under its current operating state.

[0090] In practical applications, calculating the equivalent bandwidth of the current inner loop based on the adjusted current inner loop model refers to using the updated model to calculate the frequency response characteristics of the current inner loop after the model parameters are dynamically updated, thereby determining its equivalent bandwidth. For example, the equivalent bandwidth can be determined by performing frequency domain analysis on the adjusted current inner loop model, such as calculating the cutoff frequency of its open-loop transfer function, or by simulating and analyzing its step response time. The aim is to obtain a more accurate equivalent bandwidth of the current inner loop under the current dynamic operating conditions, providing an accurate basis for the subsequent generation of the callback factor.

[0091] This application addresses the problem of inaccurate equivalent bandwidth calculation caused by fixed parameters in the current inner loop model, which is a problem in traditional methods, by introducing dynamic adjustment of the inductance and resistance parameters in the current inner loop model. Specifically, when the DC bus voltage, AC grid voltage, and switching frequency change in real time, these changes directly or indirectly affect the actual inductance and resistance characteristics of the inverter's internal circuitry. If the inductance and resistance parameters in the current inner loop model remain unchanged, the equivalent bandwidth calculated based on this model will not accurately reflect the true response capability of the current inner loop under current dynamic operating conditions. This application dynamically adjusts the inductance and resistance parameters in the current inner loop model according to these real-time rates of change, enabling the current inner loop model to approximate the actual physical characteristics of the inverter in real time. It is precisely because the current inner loop model is more accurate that the equivalent bandwidth calculated based on this adjusted model can more precisely reflect the actual dynamic response capability of the current inner loop. This precise equivalent bandwidth information provides a more reliable basis for the generation of subsequent callback factors, thereby making the adjustment of the upper limit of the rate of change of the callback factors and the rise slope more reasonable, and ensuring that the adjustment of the current reference command is more accurate and effective.

[0092] In some preferred embodiments, a specific example is given below. Suppose that during inverter operation, the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency all show an upward trend. This may indicate that the system is under heavy load or transient impact. In this case, a mapping relationship or lookup table can be preset. Based on these real-time rates of change, the equivalent inductance parameter in the current inner loop model can be slightly reduced to reflect the decrease in equivalent inductance caused by magnetic saturation effect or increased high-frequency losses. Simultaneously, the equivalent resistance parameter can be slightly increased to reflect increased losses. For example, if the real-time rate of change exceeds a certain threshold, the inductance parameter can be reduced by 5% proportionally, and the resistance parameter can be increased by 3% proportionally. After these parameters are adjusted, frequency domain analysis can be performed using the adjusted current inner loop model (e.g., a transfer function model based on an LCL filter) to calculate the -3dB cutoff frequency of its open-loop transfer function, which is the equivalent bandwidth of the current inner loop. For example, the calculated adjusted equivalent bandwidth is 1.5kHz, while using fixed parameters might yield 1.2kHz. This more precise 1.5kHz equivalent bandwidth will be used to adjust the upper limit of the rate of change and the rise slope of the callback factor, so that the callback factor can respond to the actual system dynamics more quickly and accurately, avoiding control lag or overshoot caused by inaccurate bandwidth estimation.

[0093] S604. Based on the equivalent bandwidth, adjust the upper limit of the rate of change of the initial callback factor and the recovery slope of the initial callback factor to generate the callback factor.

[0094] The upper limit of the rate of change limits the maximum change of the callback factor per unit time, preventing overshoot or oscillation; the recovery slope determines the rate at which the adjustment effect of the callback factor on the current reference command gradually decreases after the system returns to normal. By adaptively adjusting these two parameters, it can be ensured that the generated callback factor can both respond quickly to system anomalies and smoothly guide the system recovery, avoiding excessive or insufficient compensation.

[0095] This application's solution overcomes the limitations of generating a callback factor solely based on static thresholds by introducing real-time rate of change of DC bus voltage, AC grid voltage, and switching frequency, and calculating the equivalent bandwidth of the current inner loop based on this real-time information. Because these real-time parameters accurately reflect the actual operating environment of the inverter and the dynamic characteristics of its internal control loop, the calculated equivalent bandwidth can more precisely characterize the real-time execution capability of the current inner loop. Furthermore, by dynamically adjusting the upper limit of the initial callback factor's rate of change and the recovery slope, the generated callback factor can possess stronger adaptability. When the system is in a state of drastic change or instability, the calculated equivalent bandwidth guides the callback factor to adjust in a more aggressive or conservative manner, ensuring that the adjustment of the current reference command can both quickly and effectively suppress anomalies and avoid new instability caused by over-response.

[0096] like Figure 3 As shown in the figure, this embodiment of the invention also provides an inverter control strategy optimization system. The system includes: The status information acquisition module is used to acquire the voltage deviation and voltage change rate of the DC bus voltage. The execution capability assessment module is used to evaluate the real-time execution capability of the current inner loop; the real-time execution capability includes the range of current amplitude and the range of current change rate that the current inner loop can handle. The original compensation requirement generation module is used to generate original compensation requirements based on voltage deviation, voltage change rate, and real-time execution capability; the original compensation requirements are used to compensate for DC bus voltage. The instruction constraint processing module is used to constrain the amplitude and rate of change of the original compensation requirement based on the real-time execution capability, and obtain a constrained current reference instruction. The current regulation module is used to adjust the grid-connected current in the inner current loop according to the current reference command.

[0097] This application also provides a computer-readable storage medium. All or part of the processes in the above method embodiments can be executed by a computer program instructing related hardware. This program can be stored in the computer-readable storage medium, and when executed, it can include the processes of the above method embodiments. The computer-readable storage medium can be an internal storage unit of the task execution device (including a data sending end and / or a data receiving end) of any of the foregoing embodiments, such as the hard disk or memory of the task execution device. The computer-readable storage medium can also be an external storage device of the terminal device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal device. Further, the computer-readable storage medium can include both the internal storage unit of the task execution device and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by the task execution device. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0098] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0099] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, essentially, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0100] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application.

Claims

1. A method for optimizing inverter control strategy, characterized in that, include: Obtain the voltage deviation and rate of change of the DC bus voltage; Evaluate the real-time execution capability of the inner current loop; The real-time execution capability includes the range of current amplitude and the range of current change rate that the inner current loop can handle. Based on the voltage deviation, the voltage change rate, and the real-time execution capability, an initial compensation requirement is generated; the initial compensation requirement is used to compensate the DC bus voltage. Based on the real-time execution capability, the amplitude and rate of change of the original compensation requirement are constrained to obtain a constrained current reference command; The inner current loop adjusts the grid-connected current according to the current reference command.

2. The inverter control strategy optimization method according to claim 1, characterized in that, Determining the current amplitude range includes: Obtain the DC bus voltage, AC grid voltage, and filter inductance value; The modulation coefficient is calculated based on the DC bus voltage, the AC grid voltage, and the filter inductance value. The current amplitude range is determined based on the modulation coefficient and the DC bus voltage.

3. The inverter control strategy optimization method according to claim 1, characterized in that, Determining the range of the current change rate includes: Obtain the DC bus voltage and the filter inductance value; The range of the current change rate is determined based on the filter inductance value and the DC bus voltage.

4. The inverter control strategy optimization method according to claim 1, characterized in that, The step of generating the original compensation requirement based on the voltage deviation, the voltage change rate, and the real-time execution capability includes: The system state is determined based on the voltage deviation, the voltage change rate, and the real-time execution capability; the system state includes a normal compensation state and a limited compensation state. When the system is in the normal compensation state, the voltage deviation is used as input, and after calculation with a fixed proportional coefficient and integral coefficient, the current reference value is output to obtain the original compensation requirement. When the system is in the constrained compensation state, the current compensation amount is calculated based on the equivalent parameters of the voltage change rate and the DC bus capacitance to obtain the original compensation requirement.

5. The inverter control strategy optimization method according to claim 4, characterized in that, The step of determining the system state based on the voltage deviation, the voltage change rate, and the real-time execution capability includes: Based on the real-time execution capability, determine whether the current inner loop modulation margin is greater than the margin threshold; When the first preset condition is met, the system state is determined to be the normal compensation state; the first preset condition includes: the voltage deviation is less than the deviation threshold, the voltage change rate is less than the change rate threshold, and the current inner loop modulation margin is greater than the margin threshold. When the first preset condition is not met, the system state is determined to be the restricted compensation state.

6. The inverter control strategy optimization method according to claim 1, characterized in that, The inner current loop adjusts the grid-connected current according to the current reference command, including: Continuously acquire the actual tracking status of the inner current loop; the actual tracking status includes the current tracking error and modulation coefficient; The current reference command is adjusted according to the actual tracking status; The inner current loop adjusts the grid-connected current according to the adjusted current reference command.

7. The inverter control strategy optimization method according to claim 6, characterized in that, The adjustment of the current reference command based on the actual tracking state includes: If the integral of the absolute value of the current tracking error exceeds a set tolerance threshold or the modulation coefficient is greater than a preset threshold within N consecutive control cycles, a callback factor is generated; N is a preset positive integer. The current reference command is adjusted based on the callback factor.

8. The inverter control strategy optimization method according to claim 7, characterized in that, If the integral of the absolute value of the current tracking error exceeds a set tolerance threshold, or the modulation coefficient is greater than a preset threshold, a callback factor is generated, including: If the integral of the absolute value of the current tracking error exceeds the set tolerance threshold, or the modulation coefficient is greater than the preset threshold, then an initial callback factor is generated. The real-time rate of change of DC bus voltage, the real-time rate of change of AC grid voltage, and the real-time rate of change of switching frequency are obtained. The equivalent bandwidth of the inner current loop is calculated based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency. The upper limit of the rate of change of the initial callback factor and the recovery slope of the initial callback factor are adjusted according to the equivalent bandwidth to generate the callback factor.

9. The inverter control strategy optimization method according to claim 8, characterized in that, The step of calculating the equivalent bandwidth of the inner current loop based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency includes: Based on the real-time rate of change of the DC bus voltage, the real-time rate of change of the AC grid voltage, and the real-time rate of change of the switching frequency, adjust the inductance and resistance parameters in the current inner loop model. Based on the adjusted current inner loop model, the equivalent bandwidth of the current inner loop is calculated.

10. An inverter control strategy optimization system, characterized in that, The system includes: The status information acquisition module is used to acquire the voltage deviation and voltage change rate of the DC bus voltage. The execution capability assessment module is used to assess the real-time execution capability of the current inner loop; the real-time execution capability includes the range of current amplitude and the range of current change rate that the current inner loop can handle. The original compensation requirement generation module is used to generate original compensation requirements based on the voltage deviation, the voltage change rate, and the real-time execution capability; the original compensation requirements are used to compensate the DC bus voltage. The instruction constraint processing module is used to constrain the amplitude and rate of change of the original compensation requirement based on the real-time execution capability, so as to obtain a constrained current reference instruction. The current regulation module is used to adjust the grid-connected current in the inner current loop according to the current reference command.

Images