Inverter control method, device and system

Abstract

The application provides an inverter control method, device and system. It relates to power electronic control. The inverter is a three-phase four-wire inverter. The method comprises the following steps: acquiring real-time output voltage of a center line module and real-time inductance current of a filter inductor; comparing the real-time output voltage with a half bus DC voltage corresponding to a DC input source to obtain a real-time voltage deviation; tracking and processing the real-time voltage deviation through a voltage outer loop to obtain a real-time current control instruction; superimposing a virtual impedance component on the real-time current control instruction to obtain a real-time current reference value; comparing the real-time inductance current with the real-time current reference value to obtain a real-time current deviation; tracking and processing the real-time current deviation through a current inner loop; and controlling complementary conduction of a first switch tube and a second switch tube to control inductance current change and to regulate the output voltage of the center line module. Based on the method provided by the application, the power frequency disturbance suppression and dynamic response performance can be improved.

Description

Technical Field

[0001] This application relates to the field of power electronic control, and in particular to an inverter control method, device and system. Background Technology

[0002] In photovoltaic power generation systems, three-phase four-wire inverters typically employ an independent neutral module in conjunction with feedback control to maintain stable neutral voltage and adapt to mixed load power supply.

[0003] However, existing open-loop or dual closed-loop proportional-integral (PI) control has limited ability to suppress power frequency disturbances caused by neutral current under unbalanced and nonlinear load conditions, which can easily lead to voltage fluctuations in split capacitors and bus oscillations. At the same time, changes in inductance parameters will alter the dynamic characteristics of the system, reduce the stability margin, and make it more prone to overshoot or oscillation during sudden load changes.

[0004] Therefore, improving the stability of midpoint voltage control to enhance power frequency disturbance suppression and dynamic response performance has become an urgent problem to be solved in this field. Summary of the Invention

[0005] This application provides an inverter control method, device, and system that can improve the stability of the midpoint voltage control, thereby improving the power frequency disturbance suppression and dynamic response performance.

[0006] In a first aspect, embodiments of this application provide an inverter control method. The inverter is a three-phase four-wire inverter, including a DC input source, a bus capacitor, a three-phase inverter bridge, and a neutral module. The neutral module includes two complementary first and second switching transistors and a filter inductor. The neutral module adopts a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop. The method includes:

[0007] The real-time output voltage of the neutral module and the real-time inductor current of the filter inductor are collected.

[0008] The real-time output voltage is compared with the DC voltage of the half bus corresponding to the DC input source to obtain the real-time voltage deviation.

[0009] Real-time voltage deviation is tracked and processed by the outer voltage loop to obtain real-time current control commands;

[0010] The real-time current reference value is obtained by superimposing a virtual impedance component on the real-time current control command.

[0011] The real-time inductor current is compared with the real-time current reference value to obtain the real-time current deviation.

[0012] The real-time current deviation is tracked and processed through the inner current loop, and the first and second switching transistors are controlled to conduct in a complementary manner to control the change in inductor current and adjust the output voltage of the neutral module.

[0013] In one possible implementation, the voltage outer loop includes a first PI controller and a quasi-resonant controller;

[0014] Real-time voltage deviation is tracked and processed through the outer voltage loop to obtain real-time current control commands, including:

[0015] The real-time voltage deviation is processed by the first PI controller to obtain the real-time base current command component;

[0016] The real-time voltage deviation is processed by a quasi-resonant controller to obtain a real-time compensation current command.

[0017] The real-time base current command component and the real-time compensation current command are superimposed to obtain the real-time current control command.

[0018] In one possible implementation, the real-time voltage deviation is processed by a first PI controller to obtain the real-time base current command component, including:

[0019] The real-time voltage deviation is averaged and filtered to obtain the DC component voltage error signal;

[0020] The DC component voltage error signal is input to the first PI controller to obtain the real-time base current command component.

[0021] In one possible implementation, averaging filtering of the real-time voltage deviation includes:

[0022] Obtain the fluctuation frequency and amplitude of the real-time voltage deviation within the current time period;

[0023] Adjust the average filter window length based on the fluctuation frequency and fluctuation amplitude;

[0024] Based on the adjusted average filter window length, the real-time voltage deviation is averaged and filtered to obtain the DC component voltage error signal.

[0025] In one possible implementation, the methods for averaging the real-time voltage deviation include sliding window averaging and skipping window averaging.

[0026] In one possible implementation, the step of determining the virtual impedance component includes:

[0027] The ratio between the real-time output voltage of the neutral module and the preset virtual impedance is determined as the virtual impedance component.

[0028] In one possible implementation, the inner current loop includes a second PI controller;

[0029] By tracking and processing the real-time current deviation through the inner current loop, the first and second switching transistors are controlled to conduct complementaryly, thereby controlling the inductor current change, including:

[0030] The real-time current deviation is processed by the second PI controller to obtain the real-time duty cycle modulation signal;

[0031] The real-time duty cycle modulation signal is modulated to generate drive signals for controlling the first and second switching transistors.

[0032] The inductor current is controlled by controlling the complementary conduction of the first and second switching transistors through a drive signal.

[0033] In one possible implementation, it also includes:

[0034] Compensation is performed to address the sampling delay caused by the acquisition of real-time output voltage and real-time inductor current.

[0035] Compensation is applied to the computational delay caused by the outer voltage loop and the inner current loop.

[0036] The update delay of the drive signals of the first and second switching transistors is compensated.

[0037] Secondly, embodiments of this application provide an inverter control device. The inverter is a three-phase four-wire inverter, including a DC input source, a bus capacitor, a three-phase inverter bridge, and a neutral module. The neutral module includes two complementary first and second switching transistors and a filter inductor. The neutral module adopts a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop. The device includes:

[0038] The acquisition module is used to acquire the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor.

[0039] The processing module is used to compare the real-time output voltage with the DC voltage of the half bus corresponding to the DC input source to obtain the real-time voltage deviation.

[0040] The processing module is also used to track and process real-time voltage deviation through the voltage outer loop to obtain real-time current control commands;

[0041] The processing module is also used to superimpose virtual impedance components on real-time current control commands to obtain real-time current reference values;

[0042] The processing module is also used to compare the real-time inductor current with the real-time current reference value to obtain the real-time current deviation;

[0043] The processing module is also used to track and process the real-time current deviation through the inner current loop, and control the first and second switching transistors to conduct in a complementary manner to control the change of inductor current and adjust the output voltage of the neutral module.

[0044] Thirdly, this application provides an inverter control system for performing an inverter control method as described in the first aspect and / or any possible implementation of the first aspect.

[0045] Fourthly, this application provides an electronic device, including: a processor, and a memory communicatively connected to the processor;

[0046] The memory stores instructions that the computer executes;

[0047] The processor executes computer execution instructions stored in memory to implement the inverter control method as described in the first aspect and / or any possible implementation of the first aspect.

[0048] Fifthly, this application provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement an inverter control method as described in the first aspect and / or any possible implementation of the first aspect.

[0049] Sixthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements an inverter control method as described in the first aspect and / or any possible implementation of the first aspect.

[0050] The inverter control method, device, and system provided in this application acquire the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor. Based on a dual closed-loop cascade control structure of voltage outer loop and current inner loop, the real-time voltage deviation obtained by comparing the real-time output voltage with the half-bus DC voltage is processed by the voltage outer loop to generate a real-time current control command. Then, a virtual impedance component is superimposed on the real-time current control command to obtain a real-time current reference value. The real-time current deviation between the real-time inductor current and the real-time current reference value is combined with the current inner loop to control the inductor current change. This can simultaneously improve the regulation capability of the output voltage and output current of the inverter neutral module, suppress the power frequency disturbance caused by the neutral current and the resulting voltage fluctuation of the split capacitor and bus oscillation, thereby improving the stability of the neutral point voltage control and improving the power frequency disturbance suppression and dynamic response performance under complex load and inductor parameter change conditions. Attached Figure Description

[0051] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0052] Figure 1 This is a schematic diagram of the inverter provided in this application;

[0053] Figure 2 Example of a dual-closed-loop cascade control logic diagram for an inverter neutral line module;

[0054] Figure 3 Flowchart of the inverter control method provided in this application Figure 1 ;

[0055] Figure 4 Flowchart of the inverter control method provided in this application Figure 2 ;

[0056] Figure 5 Flowchart of the inverter control method provided in this application Figure 3 ;

[0057] Figure 6 Flowchart of the inverter control method provided in this application Figure 4 ;

[0058] Figure 7 Bode plots of the transfer function under different virtual impedances are shown as examples.

[0059] Figure 8 Flowchart of the inverter control method provided in this application Figure 5 ;

[0060] Figure 9 Flowchart of the inverter control method provided in this application Figure 6 ;

[0061] Figure 10 The steady-state operating condition of the inverter is shown in the example.

[0062] Figure 11 This example illustrates the instantaneous load operation of an inverter.

[0063] Figure 12 This example illustrates the instantaneous load shedding condition of an inverter.

[0064] Figure 13 This is a schematic diagram of the inverter control device provided in the embodiments of this application;

[0065] Figure 14 A schematic diagram of the structure of the electronic device provided in this application.

[0066] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0067] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0068] It should be noted that in the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, it does not mean that the applicant has used or necessarily used the solution.

[0069] Three-phase four-wire inverter control technology is widely used in grid-connected and off-grid power supply applications of photovoltaic power generation systems, and is especially suitable for mixed power supply environments where single-phase and three-phase loads are connected simultaneously. Such systems typically maintain neutral-point voltage stability and output voltage symmetry by transmitting unbalanced current and zero-sequence current.

[0070] Common methods for achieving neutral point voltage regulation in existing three-phase four-wire inverters in photovoltaic systems include open-loop control with a fixed duty cycle and dual closed-loop PI control consisting of an outer voltage loop and an inner current loop. These methods stabilize the half-bus voltage by regulating the charging and discharging process of the split capacitor using the neutral inductor current. However, existing open-loop or dual closed-loop PI control has limited ability to suppress power frequency disturbances caused by the neutral inductor current under unbalanced and nonlinear load conditions, easily leading to voltage fluctuations in the split capacitor and bus oscillations. Simultaneously, changes in inductor parameters alter the system's dynamic characteristics, reducing the stability margin and making it more prone to overshoot or oscillations during sudden load changes.

[0071] Therefore, improving the stability of midpoint voltage control to enhance power frequency disturbance suppression and dynamic response performance has become an urgent problem to be solved in this field.

[0072] Based on the aforementioned technical problems, the inverter control method, device, and system provided in this application acquire the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor. Using a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop, the real-time voltage deviation obtained by comparing the real-time output voltage with the half-bus DC voltage is processed by the outer voltage loop to generate a real-time current control command. A virtual impedance component is then superimposed on this real-time current control command to obtain a real-time current reference value. The real-time current deviation between the real-time inductor current and the real-time current reference value is then processed by the inner current loop to control the inductor current change. This approach can simultaneously improve the regulation capability of the inverter's neutral module's output voltage and output current, suppress power frequency disturbances caused by the neutral current and the resulting voltage fluctuations of the split capacitor and bus oscillations. Furthermore, it improves the stability of the neutral point voltage control and enhances power frequency disturbance suppression and dynamic response performance under complex load and inductor parameter variation conditions.

[0073] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0074] Figure 1 A schematic diagram of the inverter provided in this application is shown below. Figure 1 As shown, the inverter is a three-phase four-wire inverter, including a DC input source U. dc Bus capacitor C n1 and C n2 A three-phase inverter bridge and a neutral module, wherein the neutral module includes two complementary first switching transistors Q. bal1 Second switch Q bal2 and filter inductor L n A three-phase four-wire inverter includes three-phase AC phase line output terminals (A, B, C terminals) and a neutral line output terminal (N terminal). N This is the neutral current. DC input source U dc The inverter neutral module employs a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop, representing the DC component of the DC bus voltage. The three-phase four-wire inverter converts the power supplied by the DC input source into AC output and maintains stable output voltage. The DC input source is the DC power source for the inverter. The filter inductor smooths the current and is directly controlled by the inner current loop; the real-time inductor current reflects the instantaneous current state passing through the filter inductor. The bus capacitor, filter inductor, and equivalent series resistance together form the output filter network. The real-time output voltage reflects the instantaneous voltage state at the output terminal of the inverter neutral module, and the output voltage represents the bus capacitor C. n1 and C n2The output voltage. Figure 2 The example inverter neutral module's dual closed-loop cascade control logic diagram is shown below. Figure 2 As shown, the dual closed-loop cascade control structure of the inverter neutral module includes an inner current loop and an outer voltage loop, wherein the outer voltage loop is based on the output voltage V. c For the controlled variable, a parallel structure of a PI controller and a quasi-resonant controller is adopted to achieve DC steady-state error-free regulation and power frequency disturbance suppression. The inner current loop uses the inductor current i L As the controlled variable, a PI controller is used to achieve fast current tracking.

[0075] Figure 3 Flowchart of the inverter control method provided in this application Figure 1 ,like Figure 3 As shown, it includes:

[0076] S301: Collect the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor.

[0077] For example, the real-time output voltage and real-time inductor current of the neutral module are obtained through the sampling unit. After the acquisition is completed, the real-time output voltage and real-time inductor current can be stored in the data register area and used as input quantities for subsequent voltage deviation comparison, current control command generation, current reference value generation, and current deviation comparison.

[0078] S302. Compare the real-time output voltage with the DC voltage of the half bus corresponding to the DC input source to obtain the real-time voltage deviation.

[0079] Example, combination Figure 2 The DC voltage of the half bus is 0.5U. dc 0.5U dc As the DC reference voltage and output voltage V c The difference is taken as the real-time voltage deviation.

[0080] S303: Real-time voltage deviation is tracked and processed through the outer voltage loop to obtain real-time current control commands.

[0081] For example, the voltage outer loop in the dual closed-loop cascade control structure performs voltage regulation, and its input is the real-time voltage deviation. The output is a real-time current control command applied to the current channel, which indirectly regulates the output voltage of the inverter neutral module by adjusting the target inductor current. The voltage outer loop can be implemented using a discrete control algorithm in the digital controller. In this application, considering that the real-time voltage deviation may contain different disturbance components, the voltage outer loop continuously tracks the deviation and generates a real-time current control command.

[0082] Optionally, the voltage outer loop includes a first PI controller and a quasi-resonant controller; Figure 4Flowchart of the inverter control method provided in this application Figure 2 ,like Figure 4 As shown, S303 includes:

[0083] S401. The real-time voltage deviation is processed by the first PI controller to obtain the real-time base current command component.

[0084] For example, the outer voltage loop maintains a constant output voltage and suppresses power frequency disturbances on the load side, employing a parallel processing method involving a first PI controller and a quasi-resonant controller. Specifically, the real-time voltage deviation is input to both the first PI controller and the quasi-resonant controller. The first PI controller outputs the base current command component based on its proportional and integral components. The first PI controller ensures zero steady-state error in DC and provides some suppression of low-frequency disturbances; it is responsible for eliminating DC deviations.

[0085] S402. The real-time voltage deviation is processed by the quasi-resonant controller to obtain the real-time compensation current command.

[0086] For example, to address power frequency disturbances on the load side, a quasi-resonant controller is used to perform fixed-frequency compensation for dynamic disturbances caused by power frequency disturbances in the real-time voltage deviation, thereby enhancing the tracking and suppression capabilities at specific frequencies. Since the error input of the quasi-resonant controller uses the real-time value of the half-bus voltage difference, this method allows the quasi-resonant controller to focus on eliminating the half-bus DC voltage difference.

[0087] This quasi-resonant controller exhibits extremely high amplitude gain at the power frequency, significantly amplifying the error signal at that frequency. This generates a strong compensation current command, giving the voltage loop a very high ability to suppress power frequency disturbances. Simultaneously, the quasi-resonant controller has a built-in phase compensation angle, which can precisely adjust its phase output at the power frequency to compensate for the phase lag of the output voltage at that frequency. This ensures that the system maintains sufficient phase margin while achieving high gain, effectively avoiding system oscillations and balancing disturbance suppression capability with system stability.

[0088] S403. The real-time base current command component and the real-time compensation current command are superimposed to obtain the real-time current control command.

[0089] For example, the real-time current control command formed by superimposing the real-time base current command component and the real-time compensation current command can simultaneously ensure steady-state accuracy and dynamic response. Therefore, the outer voltage loop has a stronger ability to correct voltage fluctuations caused by load imbalance, the fluctuation amplitude of the output voltage is reduced, the current command under power frequency disturbances is smoother, and the control consistency of the system is maintained when parameters change.

[0090] Optional, Figure 5Flowchart of the inverter control method provided in this application Figure 3 ,like Figure 5 As shown, S401 includes:

[0091] S501. Average filtering is performed on the real-time voltage deviation to obtain the DC component voltage error signal.

[0092] For example, the error input of the PI controller uses the average value of the half-bus voltage difference as a filter, supplemented by a low-pass filter, allowing the first PI controller to focus on eliminating the half-bus DC voltage difference. Specifically, multiple sampling points of the real-time voltage deviation can be accumulated and averaged to output a smoothed DC component voltage error signal.

[0093] S502: Input the DC component voltage error signal to the first PI controller to obtain the real-time base current command component.

[0094] For example, the signal is input to the first PI controller for proportional amplification and integral accumulation to generate a real-time base current command component. This base current command component serves as the steady-state regulation quantity of the voltage outer loop. It is superimposed with the subsequent real-time compensation current command to form a real-time current control command, enabling the voltage outer loop to establish a continuous correction effect against DC deviation.

[0095] The DC component in the real-time voltage deviation is extracted separately and input into the first PI controller for processing, which makes the tracking of the DC voltage deviation of the half bus more stable in the outer voltage loop, reduces the jitter of the basic current command component, and makes the subsequent current regulation more continuous, thereby improving the stability and control accuracy of the output voltage.

[0096] Optional, Figure 6 Flowchart of the inverter control method provided in this application Figure 4 ,like Figure 6 As shown, S501 includes:

[0097] S601. Obtain the fluctuation frequency and fluctuation amplitude of the real-time voltage deviation within the current time period.

[0098] For example, the real-time voltage deviation can be sampled and cached first, and the fluctuation frequency and fluctuation amplitude can be calculated based on the change interval and amplitude difference of adjacent sampled values ​​within the current time period.

[0099] S602. Adjust the average filter window length according to the fluctuation frequency and fluctuation amplitude.

[0100] For example, when the fluctuation frequency is high or the fluctuation amplitude is large, the window length can be increased accordingly to smooth out power frequency disturbances and high frequency fluctuations more fully during the averaging process; when the fluctuation frequency is low or the fluctuation amplitude is small, the window length can be decreased accordingly to retain the DC component variation in the real-time voltage deviation.

[0101] S603. Based on the adjusted average filter window length, the real-time voltage deviation is averaged and filtered to obtain the DC component voltage error signal.

[0102] For example, a moving average calculation is performed on the real-time voltage deviation based on the adjusted window length, outputting a DC component voltage error signal. This signal is then sent to the first PI controller to generate the real-time base current command component. This method dynamically changes the time scale of the averaging filter by jointly identifying the frequency and amplitude characteristics of the deviation, making the signal entering the first PI controller closer to the DC component. This separates the adjustment amount in the real-time voltage deviation from the power frequency disturbance component, reduces the interference of the power frequency component on the voltage outer loop, and allows the base current command component to adapt to the operating conditions.

[0103] Based on the method in this example, the average filter window can be adjusted according to the deviation fluctuation, the extraction accuracy of the DC component voltage error signal is improved, the input of the first PI controller is more stable, and thus the adaptability of the voltage outer loop to unbalanced loads and parameter perturbations is enhanced, and the smoothness and control consistency of the output voltage regulation are improved.

[0104] Optionally, the methods for averaging the real-time voltage deviation include sliding window averaging and skip window averaging.

[0105] For example, sliding window averaging filtering can be achieved by the controller continuously accumulating and averaging the deviation signal within a preset time window, or by using skip-window averaging filtering to reduce computational load. Skip-window averaging filtering allows the controller to update the mean of the deviation signal at fixed intervals within a preset time window. Unlike the continuous accumulation and averaging of sliding window averaging filtering, the output of skip-window averaging filtering exhibits discrete jumps, significantly reducing the computational frequency. By processing the real-time voltage deviation using either sliding window averaging filtering or skip-window averaging filtering, the appropriate averaging method can be selected based on different computational resource conditions and disturbance characteristics, and a relatively stable DC component voltage error signal can be output for use in the subsequent voltage outer loop. Thus, both filtering smoothness and computational efficiency can be balanced.

[0106] S304. Add a virtual impedance component to the real-time current control command to obtain the real-time current reference value.

[0107] Example, combination Figure 2 The real-time current reference value is defined as i refInsufficient damping at the resonant frequency of an LC filter can cause spikes in the output voltage amplitude-frequency response, reducing control quality and even triggering system oscillations. This example introduces a virtual impedance element in the control algorithm to suppress this. The virtual impedance component is used to construct equivalent damping at the control level. It does not directly rely on the physical resistance added in the actual hardware, but rather corrects the current reference path, enabling the inverter to maintain controllable dynamic damping characteristics even when the filter inductor parameters change, the output disturbance increases, or the midpoint potential fluctuates.

[0108] Optionally, the steps for determining the virtual impedance components include:

[0109] The ratio between the real-time output voltage of the neutral module and the preset virtual impedance is determined as the virtual impedance component.

[0110] Example, combination Figure 2 The output voltage V c Divide by a preset virtual impedance Z v This yields a virtual current component, which is also the virtual impedance component. This component is superimposed on the reference input of the current loop in the form of negative feedback. Its physical effect is equivalent to connecting a resistor in parallel across the output capacitor; this resistor dissipates resonant energy, reduces the resonant peak value, and thus improves the frequency characteristics of the output voltage. From the DC input source U... dc to inductor current i L The transfer function is:

[0111]

[0112] Where L is the filter inductance L n The inductance value, R is the filter inductance L n The equivalent resistance value, C=C n1 +C n2 S is the differential operator. Figure 7 For example, the Bode plot of the transfer function under different virtual impedances, such as Figure 7 As shown, the gain at the resonant point is determined by the filter inductor L. n With C n1 and C n2 The equivalent capacitance C is generated by resonance. When a virtual load Z is used... v When suppressing resonance, the gain at the resonant point can be significantly reduced, making the system more stable. Therefore, after introducing virtual impedance, the phase characteristics of the controlled object are significantly smoothed, and the transition from low frequency to high frequency is more gradual, thus providing a more ideal output voltage for the outer voltage loop, enabling the outer voltage loop to obtain sufficient stability margin over a wider frequency range.

[0113] S305. Compare the real-time inductor current with the real-time current reference value to obtain the real-time current deviation.

[0114] Example, combination Figure 2 The real-time current reference value i ref With real-time inductor current i L The difference between the two values ​​is defined as the real-time current deviation. The real-time current reference value represents the target current state reached by the filter inductor within the current control cycle, while the real-time inductor current represents the instantaneous current state actually passing through the filter inductor. The difference between the two directly reflects the amplitude and direction that the inner current loop needs to be corrected for.

[0115] S306. Real-time current deviation is tracked and processed through the inner current loop, and the first and second switching transistors are controlled to conduct in a complementary manner to control the change of inductor current and adjust the output voltage of the neutral module.

[0116] Example, combination Figure 2 The real-time current deviation serves as the input to the inner current loop. After the real-time current deviation is input to the inner current loop, the inner current loop generates a switching modulation control quantity based on the real-time current deviation, and controls the complementary conduction state of the first and second switching transistors accordingly, so that the actual inductor current in the filter inductor follows the change of the real-time current reference value. The first and second switching transistors form a complementary conduction dual-transistor switching modulation structure. Under the control of the drive signal, they operate alternately, thereby changing the equivalent applied voltage across the filter inductor, and thus controlling the rising or falling slope of the filter inductor current.

[0117] This example acquires the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor. Based on a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop, the real-time voltage deviation obtained by comparing the real-time output voltage with the half-bus DC voltage is processed by the outer voltage loop to generate a real-time current control command. Then, a virtual impedance component is superimposed on this real-time current control command to obtain a real-time current reference value. The real-time current deviation between the real-time inductor current and the real-time current reference value is combined with the current deviation processed by the inner current loop to control the inductor current change. This can simultaneously improve the regulation capability of the inverter's neutral module's output voltage and output current, suppress power frequency disturbances caused by neutral current and the resulting voltage fluctuations of the split capacitor and bus oscillations, thereby improving the stability of the neutral point voltage control and enhancing power frequency disturbance suppression and dynamic response performance under complex load and inductor parameter variation conditions.

[0118] Optional, Figure 8 Flowchart of the inverter control method provided in this application Figure 5 ,like Figure 8 As shown, the inner current loop includes a second PI controller; S306 includes:

[0119] S801: The real-time current deviation is processed by the second PI controller to obtain the real-time duty cycle modulation signal.

[0120] For example, the second PI controller can be digitally implemented within the inverter controller. Its proportional element is used for rapid response to current changes, and its integral element is used to eliminate steady-state errors. The inner current loop can use the proportional control of the second PI controller to perform tracking calculations on the real-time current deviation and output a real-time duty cycle modulated signal. Combined with... Figure 2 The real-time duty cycle modulation signal can be defined as "d".

[0121] S802. Modulate the real-time duty cycle modulation signal to generate a drive signal for controlling the first and second switching transistors.

[0122] For example, the real-time duty cycle modulated signal, after being processed by pulse width modulation (PWM), can be converted into a pulse width control pulse synchronized with the switching frequency. After being amplified and shaped by the isolation drive circuit, a drive signal that can drive two switching transistors to conduct complementaryly is obtained.

[0123] S803 controls the complementary conduction of the first and second switching transistors by a drive signal to control the change in inductor current.

[0124] For example, the first and second switching transistors can operate in a complementary conduction mode, being in the on and off states respectively within one switching cycle, thereby creating alternating voltages across the filter inductor and thus changing the rise and fall slopes of the filter inductor current.

[0125] This inner current loop tracks the real-time current deviation in a closed loop, converting it into a real-time duty cycle modulation signal. This signal is then modulated to generate a drive signal, controlling the complementary conduction of two switching transistors. This allows the filter inductor current to adjust rapidly according to the real-time current reference value. Because the real-time current deviation can be continuously corrected within the inner loop, the change in the filter inductor current remains consistent with the real-time current control command, thereby achieving effective regulation of the output current of the inverter's neutral module.

[0126] Optional, Figure 9 Flowchart of the inverter control method provided in this application Figure 6 ,like Figure 9 As shown, it also includes:

[0127] S901, Compensate for the sampling delay caused by the acquisition of real-time output voltage and real-time inductor current.

[0128] Example, combination Figure 2 The inner current loop also includes a compensation module. The compensation module compensates for the delay errors caused by the externalized voltage and the internal current loop, thereby eliminating these delay errors. Specifically, the sampling delay compensation is achieved by introducing a compensation term equal to or half a sampling period.

[0129] S902, Compensate for the calculation delay formed by the voltage outer loop and the current inner loop.

[0130] For example, the delay compensation is calculated by shifting the phase forward of the discretized parameters of the outer voltage loop and the inner current loop.

[0131] S903, Compensate for the update delay of the drive signals of the first and second switching transistors.

[0132] For example, update delay compensation is achieved by modeling the time difference between the PWM modulation carrier and the drive output and adding a compensation amount. This compensation amount can be set according to the sampling frequency, control cycle, computation time, and PWM refresh cycle to ensure that the control quantity remains consistent with the actual switching time.

[0133] Combination Figure 2 After obtaining the real-time duty cycle modulation signal "d", a delay compensation process can be performed to obtain the duty cycle modulation signal after delay compensation. Then, the first switch and the second switch are controlled to conduct complementaryly through the duty cycle modulation signal after delay compensation.

[0134] This example can compensate for three main timing errors in the control loop, correct the deviation between the real-time duty cycle modulation signal and the actual switching action, thereby improving the phase consistency and dynamic response consistency of the control loop, and enhancing control stability under load changes.

[0135] Combination Figure 2 After obtaining the duty cycle modulation signal after delay compensation processing, the control logic after the current inner loop includes: controlling the first and second switching transistors to conduct complementaryly through the duty cycle modulation signal after delay compensation processing, and then controlling the DC input source U... dc Confirm Q bal1 Q bal2 Voltage V at the midpoint d V d With output voltage V c The difference between them is determined as the voltage drop V of the filter inductor. L V L Filtered inductor L n Filtering processing, i.e. The inductor current i is obtained after processing the function. L ,in, Let i be the equivalent resistance of the filter inductor. Let the inductor current i be... L With the neutral current iN The difference between them is determined as the output current i. C Then, the output current i C via output bus capacitor C n1 and C n2 Filtering processing, i.e. The output voltage V is obtained after processing by the function. c When a power frequency disturbance current occurs on the load side, the output voltage V c This will generate corresponding fluctuations. The quasi-resonant controller in the outer voltage loop responds quickly, and the loop gain provided at the power frequency forces the inductor current i L This generates a compensation component that is opposite in direction to the disturbance current, thereby canceling the effect of the disturbance on the output voltage V. c The influence of this. Meanwhile, the virtual impedance Z v Provide necessary damping to prevent LC resonance amplification disturbances, ensure smooth dynamic processes, and enable the system to have both strong anti-disturbance capability and good dynamic quality.

[0136] Figure 10 The steady-state operating condition of the inverter is shown in the example. Figure 11 This example illustrates the instantaneous load switching condition of an inverter. Instantaneous load switching refers to the instantaneous connection of the load. Figure 12 This example illustrates the instantaneous load shedding condition of an inverter. Instantaneous load shedding means the instant the load is removed. In the diagram, V... bus1 Indicates the bus capacitance C n1 voltage, V bus2 Indicates the bus capacitance C n2 The voltage, ΔV bus V represents bus1 With V bus2 The difference between them. For example Figure 10 , 11 As shown in Figure 12, after processing by the inverter control method provided in this embodiment, the neutral current i N With inductor current i L They basically maintain the same phase, Q bal1 and Q bal2 The voltage remains basically the same, Q bal1 and Q bal2 The voltage difference between them fluctuates relatively smoothly. Furthermore, due to... Figure 11 and 12 As shown, Q is the value of load during instantaneous load application and removal. bal1 and Q bal2 The voltage difference between them fluctuated significantly only in the early stages, but quickly stabilized.

[0137] The inverter control method provided in this embodiment significantly improves the regulation capability of the inverter's neutral module output voltage and output current, suppresses power frequency disturbances caused by neutral current and the resulting voltage fluctuations of split capacitors and bus oscillations, thereby improving the stability of neutral point voltage control and enhancing power frequency disturbance suppression and dynamic response performance under complex load and inductor parameter variation conditions.

[0138] Figure 13 This is a schematic diagram of the inverter control device provided in the embodiments of this application. The inverter is a three-phase four-wire inverter, including a DC input source, a bus capacitor, a three-phase inverter bridge, and a neutral module. The neutral module includes two complementary conducting first and second switching transistors, and a filter inductor. The neutral module adopts a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop, as shown below. Figure 13 As shown, the device includes:

[0139] The acquisition module 131 is used to acquire the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor.

[0140] Processing module 132 is used to compare the real-time output voltage with the DC voltage of the half bus corresponding to the DC input source to obtain the real-time voltage deviation;

[0141] The processing module 132 is also used to track and process the real-time voltage deviation through the voltage outer loop to obtain real-time current control commands;

[0142] The processing module 132 is also used to superimpose virtual impedance components on the real-time current control command to obtain a real-time current reference value;

[0143] The processing module 132 is also used to compare the real-time inductor current with the real-time current reference value to obtain the real-time current deviation;

[0144] The processing module 132 is also used to track and process the real-time current deviation through the current inner loop, and control the first switch and the second switch to conduct in a complementary manner to control the change of inductor current and adjust the output voltage of the neutral module.

[0145] Optionally, the voltage outer loop includes a first PI controller and a quasi-resonant controller;

[0146] Processing module 132 is specifically used to process the real-time voltage deviation through the first PI controller to obtain the real-time base current command component;

[0147] The processing module 132 is further used to process the real-time voltage deviation through the quasi-resonant controller to obtain the real-time compensation current command;

[0148] The processing module 132 is further used to superimpose the real-time base current command component and the real-time compensation current command to obtain the real-time current control command.

[0149] Optionally, the processing module 132 is further used to perform average filtering on the real-time voltage deviation to obtain the DC component voltage error signal;

[0150] The processing module 132 is further used to input the DC component voltage error signal to the first PI controller to obtain the real-time base current command component.

[0151] Optionally, the processing module 132 is further used to obtain the fluctuation frequency and fluctuation amplitude of the real-time voltage deviation in the current time period;

[0152] The processing module 132 is also specifically used to adjust the length of the average filter window according to the fluctuation frequency and fluctuation amplitude;

[0153] The processing module 132 is further used to perform average filtering on the real-time voltage deviation based on the adjusted average filter window length to obtain the DC component voltage error signal.

[0154] Optionally, the methods for averaging the real-time voltage deviation include sliding window averaging and skip window averaging.

[0155] Optionally, the processing module 132 is further used to determine the ratio between the real-time output voltage of the neutral module and the preset virtual impedance as the virtual impedance component.

[0156] Optionally, the inner current loop includes a second PI controller;

[0157] The processing module 132 is further used to process the real-time current deviation through the second PI controller to obtain a real-time duty cycle modulation signal;

[0158] The processing module 132 is further used to modulate the real-time duty cycle modulation signal to generate a drive signal for controlling the first switch and the second switch.

[0159] The processing module 132 is further used to control the complementary conduction of the first and second switching transistors through a drive signal, so as to control the change of inductor current.

[0160] Optionally, the processing module 132 is also used to compensate for the sampling delay caused by the acquisition of real-time output voltage and real-time inductor current.

[0161] The processing module 132 is also used to compensate for the calculation delay formed by the voltage outer loop and the current inner loop;

[0162] The processing module 132 is also used to compensate for the update delay of the drive signals of the first and second switching transistors.

[0163] The inverter control device provided in this embodiment can execute the inverter control method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0164] This disclosure also provides an inverter control system for executing the inverter control method described above. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0165] Figure 14 A schematic diagram of the structure of the electronic device provided in this application. Figure 14 As shown, the electronic device 50 provided in this embodiment includes at least one processor 501 and a memory 502. Optionally, the electronic device 50 further includes a communication component 503. The processor 501, memory 502, and communication component 503 are connected via a bus.

[0166] In a specific implementation, at least one processor 501 executes computer execution instructions stored in memory 502, causing at least one processor 501 to perform the above-described method.

[0167] The specific implementation process of processor 501 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0168] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0169] The memory may include random access memory (RAM) and non-volatile memory (NVM), such as at least one disk storage device.

[0170] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0171] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0172] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0173] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory, electrically erasable programmable read-only memory, erasable programmable read-only memory, programmable read-only memory, read-only memory, magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0174] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0175] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0176] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0177] In addition, the functional units in the various embodiments of the present invention 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.

[0178] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to related technologies, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0179] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0180] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An inverter control method, characterized in that, The inverter is a three-phase four-wire inverter, including a DC input source, a bus capacitor, a three-phase inverter bridge, and a neutral module. The neutral module includes two complementary switching transistors (first and second), and a filter inductor. The neutral module adopts a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop. The method includes: The real-time output voltage of the neutral module and the real-time inductor current of the filter inductor are collected. The real-time output voltage is compared with the half-bus DC voltage corresponding to the DC input source to obtain the real-time voltage deviation. The real-time voltage deviation is tracked and processed by the outer voltage loop to obtain the real-time current control command; The real-time current reference value is obtained by superimposing a virtual impedance component on the real-time current control command. The real-time inductor current is compared with the real-time current reference value to obtain the real-time current deviation. The real-time current deviation is tracked and processed by the inner current loop, and the first and second switching transistors are controlled to conduct in a complementary manner to control the change of the inductor current and adjust the output voltage of the neutral module.

2. The method according to claim 1, characterized in that, The voltage outer loop includes a first PI controller and a quasi-resonant controller; The step of tracking the real-time voltage deviation through the outer voltage loop to obtain the real-time current control command includes: The real-time voltage deviation is processed by the first PI controller to obtain the real-time base current command component. The real-time voltage deviation is processed by the quasi-resonant controller to obtain a real-time compensation current command; The real-time base current command component and the real-time compensation current command are superimposed to obtain the real-time current control command.

3. The method according to claim 2, characterized in that, The step of processing the real-time voltage deviation through the first PI controller to obtain the real-time base current command component includes: The real-time voltage deviation is averaged and filtered to obtain the DC component voltage error signal; The DC component voltage error signal is input to the first PI controller to obtain the real-time base current command component.

4. The method according to claim 3, characterized in that, The step of averaging and filtering the real-time voltage deviation includes: Obtain the fluctuation frequency and fluctuation amplitude of the real-time voltage deviation within the current time period; The average filter window length is adjusted according to the fluctuation frequency and the fluctuation amplitude. Based on the adjusted average filter window length, the real-time voltage deviation is averaged and filtered to obtain the DC component voltage error signal.

5. The method according to claim 3 or 4, characterized in that, The methods for averaging the real-time voltage deviation include sliding window averaging and skipping window averaging.

6. The method according to claim 1, characterized in that, The steps for determining the virtual impedance component include: The ratio between the real-time output voltage of the neutral module and the preset virtual impedance is determined as the virtual impedance component.

7. The method according to claim 1, characterized in that, The inner current loop includes a second PI controller; The step of tracking the real-time current deviation through the inner current loop and controlling the complementary conduction of the first and second switching transistors to control the change in inductor current includes: The real-time current deviation is processed by the second PI controller to obtain a real-time duty cycle modulation signal; The real-time duty cycle modulation signal is modulated to generate a drive signal for controlling the first and second switching transistors. The drive signal controls the complementary conduction of the first and second switching transistors to control the change in the inductor current.

8. The method according to claim 1, characterized in that, Also includes: The sampling delay caused by acquiring the real-time output voltage and the real-time inductor current is compensated. The calculation delay formed by the outer voltage loop and the inner current loop is compensated. The update delay of the drive signals of the first and second switching transistors is compensated.

9. An inverter control device, characterized in that, The inverter is a three-phase four-wire inverter, including a DC input source, bus capacitors, a three-phase inverter bridge, and a neutral module. The neutral module includes two complementary switching transistors (first and second), and a filter inductor. The neutral module adopts a dual closed-loop cascade control structure with an outer voltage loop and an inner current loop. The device includes: The acquisition module is used to acquire the real-time output voltage of the neutral module and the real-time inductor current of the filter inductor. The processing module is used to compare the real-time output voltage with the half-bus DC voltage corresponding to the DC input source to obtain the real-time voltage deviation; The processing module is also used to track the real-time voltage deviation through the voltage outer loop to obtain real-time current control commands; The processing module is also used to superimpose virtual impedance components on the real-time current control command to obtain a real-time current reference value; The processing module is also used to compare the real-time inductor current with the real-time current reference value to obtain the real-time current deviation; The processing module is also used to track the real-time current deviation through the current inner loop, control the first switch and the second switch to conduct complementaryly, so as to control the change of the inductor current and adjust the output voltage of the neutral module.

10. An inverter control system, characterized in that, The inverter control system is used to execute the inverter control method according to any one of claims 1-8.

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