Zero-sequence circulating current control method, system and equipment of inverter parallel operation system and storage medium

Abstract

The invention discloses a zero-sequence circulating current control method, system and device for an inverter parallel operation system and a storage medium, and the method comprises the steps: sampling the output current of each parallel inverter in real time, and calculating a zero-sequence current difference value; presetting a dynamic dead zone threshold value, judging a control mode of the inverter parallel operation system based on the zero sequence current amplitude value and the dynamic dead zone threshold value, dynamically adjusting a control gain in combination with a linear variable gain mechanism, and generating a corresponding control quantity; and superposing the control quantity to a modulation wave of inverter pulse width modulation, and sending the modulation wave to an inverter driving module after amplitude limiting so as to carry out closed-loop dynamic control. According to the invention, the dynamic adaptation of the control intensity and the error amplitude is realized through a linear variable gain mechanism, and the problems of response lag and steady-state overshoot of a traditional sliding mode fixed gain are solved; and through dynamic dead zone dual-mode switching, the mode jump frequency is reduced, high-frequency oscillation is suppressed, and meanwhile, the high robustness of sliding mode control outside a dead zone is kept. The zero-sequence circulating current can be suppressed, buffeting can be smaller, and the dynamic response is better.

Description

Technical Field

[0001] This invention relates to the technical field of power electronics and power system control, and in particular to a zero-sequence circulating current control method, system, device and storage medium for a parallel inverter operation system. Background Technology

[0002] In new energy power generation systems (such as photovoltaic power plants and energy storage clusters), parallel operation of multiple inverters is a core technical solution for achieving high power output and redundancy fault tolerance. However, under complex operating conditions, high-frequency zero-sequence circulating currents can be generated in the system due to factors such as the dispersion of hardware parameters, differences in control loop delays, and impedance mismatches in distributed lines. These circulating currents not only cause inverter arm current distortion and a surge in device switching losses, but also induce common-mode voltage fluctuations. In severe cases, they may trigger false alarms in insulation monitoring or abnormal interruptions in communication links, threatening the safe operation of the system.

[0003] Currently, techniques for suppressing zero-sequence circulating current are mainly categorized into three types: passive filtering, modulation compensation, and closed-loop control. Passive filtering schemes absorb high-frequency circulating current components by adding LC filters or common-mode inductors, but these additional components significantly increase system size and cost. Modulation compensation methods (such as zero-sequence voltage injection and carrier phase optimization) can weaken low-frequency components of the circulating current, but they are sensitive to parameter disturbances and exhibit dynamic response hysteresis during load changes. Traditional sliding mode control in the closed-loop control field is widely used due to its strong robustness, but its fixed gain design and dead-zone threshold setting make it difficult to reconcile dynamic adjustment with steady-state accuracy. Specifically, insufficient gain leads to response hysteresis under large errors, while excessive gain exacerbates high-frequency chattering of switching devices under small errors. Furthermore, the fixed dead-zone boundary easily causes frequent switching of control modes, further amplifying output oscillations and limiting the long-term reliability of the system. The adjustment accuracy of traditional sliding mode control and the chattering phenomenon it generates are difficult to meet practical requirements. In recent years, high-order sliding mode control technology has emerged, which effectively reduces the oscillation amplitude of the output signal while maintaining robustness by improving the algorithm structure. Existing research mainly focuses on traditional fields such as electric motor drives. For the operating conditions of new energy grid-connected systems, there is still room for improvement in relevant control strategies. Summary of the Invention

[0004] In view of the aforementioned existing problems, this invention is proposed. Therefore, this invention provides a zero-sequence circulating current control method, system, device, and storage medium for inverter parallel operation systems to solve the problems of efficiency reduction, device loss, and electromagnetic interference caused by zero-sequence circulating current in multi-inverter parallel systems.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a zero-sequence circulating current control method for a parallel inverter system, comprising: real-time sampling of the output current of each parallel inverter and calculating the zero-sequence current difference;

[0007] A preset dynamic dead zone threshold is used to determine the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold. The control gain is dynamically adjusted in combination with the linear variable gain mechanism to generate the corresponding control quantity.

[0008] The control quantity is superimposed on the modulation wave of the inverter pulse width modulation, and after being limited, it is sent to the inverter drive module for closed-loop dynamic control.

[0009] In a preferred embodiment of the zero-sequence circulating current control method for the inverter parallel operation system described in this invention, the ratio of the common-mode voltage difference of the parallel inverter to the equivalent zero-sequence impedance of the parallel system is used as the zero-sequence current difference.

[0010] As a preferred embodiment of the zero-sequence circulating current control method for the inverter parallel operation system described in this invention, the control mode of the inverter parallel operation system is determined based on the zero-sequence current amplitude and the dynamic dead zone threshold, including: when the zero-sequence current amplitude is greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the sliding mode control mode.

[0011] When the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the proportional control mode.

[0012] As a preferred embodiment of the zero-sequence circulating current control method for the inverter parallel operation system described in this invention, the method involves: dynamically adjusting the control gain using a linear variable gain mechanism to generate the corresponding control quantity, including: constructing an integral sliding mode surface function based on the zero-sequence current difference, expressed as:

[0013] s k =s k-1 +Δi z ·T s

[0014] Among them, s k-1 This is the sliding surface state variable of the previous control cycle, with an initial value of s0 = 0.

[0015] As a preferred embodiment of the zero-sequence circulating current control method for the inverter parallel operation system described in this invention, it further includes: when the zero-sequence current amplitude is greater than the dynamic dead zone threshold, the linear gain coefficient current_k is dynamically adjusted according to the zero-sequence current amplitude, and the linear variable gain coefficient is expressed as:

[0016]

[0017] Where, k mink is the minimum gain coefficient. max For the maximum gain coefficient, |Δi z | represents the absolute value of the current zero-sequence current, I ref The reference threshold for linear gain adjustment;

[0018] The generated sliding mode control output is represented as follows:

[0019] V smc = -current_k·sign(s) k )

[0020] Where sign is the sign function, V smc This is the sliding mode control quantity.

[0021] The beneficial effects of this preferred technical solution are that it reduces the number of mode jumps and suppresses high-frequency oscillations by using dynamic dead-zone dual-mode switching, while retaining the strong robustness of sliding mode control outside the dead zone.

[0022] As a preferred embodiment of the zero-sequence circulating current control method for the transformer parallel operation system described in this invention, it further includes: switching to proportional control when the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, and the control output is expressed as:

[0023] V prop =-K p ·current_k·Δi z

[0024] Among them, K p V is the proportional control coefficient. prop This is a proportional control quantity.

[0025] As a preferred embodiment of the zero-sequence circulating current control method for the inverter parallel operation system described in this invention, the following steps are taken: The control quantity is superimposed onto the modulation wave of the inverter pulse width modulation, and after amplitude limiting, it is sent to the inverter drive module for closed-loop dynamic control. This includes: superimposing the control output onto the modulation wave of the inverter three-phase pulse width modulation, adjusting the common-mode voltage component to suppress circulating current, as expressed in:

[0026]

[0027] Among them, V out To control the output voltage, These are the reference voltage values ​​for the modulation wave of the three-phase pulse width modulation of the inverter. These are the modulation waves of the three-phase pulse width modulation of the adjusted inverter.

[0028] The beneficial effect of this preferred technical solution is that it controls the output V. outThe three-phase modulation wave superimposed on the inverter suppresses zero-sequence circulating current energy by adjusting the common-mode voltage component; the output limiter constrains V. out This prevents waveform distortion caused by overmodulation and reduces stress on switching devices.

[0029] Secondly, the present invention provides a zero-sequence circulating current control system for a parallel inverter system, comprising: a data acquisition and calculation module for real-time sampling of the output current of each parallel inverter and calculating the zero-sequence current difference and its absolute value.

[0030] The control mode switching module is used to preset the dynamic dead zone threshold, determine the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold, and dynamically adjust the control gain in combination with the linear variable gain mechanism to generate the corresponding control quantity.

[0031] The control module is used to superimpose the control quantity onto the modulation wave of the inverter pulse width modulation, and after amplitude limiting, send it to the inverter drive module for closed-loop dynamic control.

[0032] Thirdly, the present invention provides an electronic device, comprising:

[0033] Memory and processor;

[0034] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the zero-sequence circulating current control method for the inverter parallel operation system.

[0035] Fourthly, the present invention provides a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the zero-sequence circulating current control method for the inverter parallel operation system.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention balances the dynamic response speed and steady-state accuracy of the control system through dynamic gain adjustment and smooth dual-mode switching, while reducing the impact of high-frequency oscillations on switching devices, improving system reliability and operating efficiency. It introduces a linear variable gain mechanism and dynamic dead-zone threshold determination to achieve dual-mode synergy of sliding mode control and proportional control, taking into account both strong anti-disturbance and low chattering characteristics. The linear variable gain mechanism realizes dynamic adaptation of control strength and error amplitude, overcoming the response lag and steady-state overshoot problems of traditional sliding mode fixed gain. The dynamic dead-zone dual-mode switching reduces the number of mode jumps, suppresses high-frequency oscillations, and retains the strong robustness of sliding mode control outside the dead zone. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0038] Figure 1 This is a flowchart illustrating a zero-sequence circulating current control method for a parallel inverter system according to an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the control flow of a zero-sequence circulating current control system for an inverter parallel operation system according to an embodiment of the present invention;

[0040] Figure 3 This is a topology diagram of an inverter parallel operation system according to an embodiment of the present invention, which describes a zero-sequence circulating current control method for an inverter parallel operation system.

[0041] Figure 4 The figure shows the simulation results of suppressing the zero-sequence circulating current in the system under conventional sliding mode control, which is a zero-sequence circulating current control method for an inverter parallel operation system according to an embodiment of the present invention.

[0042] Figure 5 The figure shows the simulation results of suppressing the zero-sequence circulating current in a parallel inverter system according to an embodiment of the present invention during super-spiral sliding mode control.

[0043] Figure 6 The figure shows the simulation results of the zero-sequence circulating current control method for a parallel inverter system according to an embodiment of the present invention, which suppresses the zero-sequence circulating current of the system during control.

[0044] Figure 7 This is a simulation result of the output chattering amplitude of the control system in the traditional sliding mode control of the zero-sequence circulating current control method of an inverter parallel operation system according to an embodiment of the present invention;

[0045] Figure 8 This is a simulation result diagram of the output chattering amplitude of the control system during super-spiral sliding mode control of a zero-sequence circulating current control method for an inverter parallel operation system according to an embodiment of the present invention;

[0046] Figure 9 The figure shows the simulation results of the output chattering amplitude of the control system of the present invention, which is a zero-sequence circulating current control method for a parallel inverter system according to an embodiment of the present invention. Detailed Implementation

[0047] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0048] Example 1, referring to Figures 1-2 As one embodiment of the present invention, this embodiment provides a zero-sequence circulating current control method for an inverter parallel operation system, such as... Figure 1 As shown, it includes:

[0049] S100: Real-time sampling of the output current of each parallel inverter and calculation of the zero-sequence current difference;

[0050] S200: Preset dynamic dead zone threshold, determine the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold, and dynamically adjust the control gain in combination with the linear variable gain mechanism to generate the corresponding control quantity.

[0051] S300: The control quantity is superimposed on the modulation wave of the inverter pulse width modulation, and after being limited, it is sent to the inverter drive module for closed-loop dynamic control.

[0052] It should be noted that in inverter parallel operation systems, zero-sequence circulating current can lead to reduced system efficiency, increased device losses, and electromagnetic interference. While traditional sliding mode control can effectively suppress circulating current, its fixed gain design makes it difficult to balance dynamic response and steady-state accuracy, and an unreasonable dead-zone setting can easily cause high-frequency oscillations. This contradiction mainly manifests in insufficient gain leading to response lag under large errors, while excessive gain exacerbates chattering under small errors. Simultaneously, a fixed dead-zone boundary leads to frequent mode switching, affecting control smoothness. This invention proposes a dual-mode collaborative control strategy of linear variable gain and dynamic dead-zone. First, through a linear variable gain mechanism (gain linearly adjusted with the magnitude of the zero-sequence current error), high gain and fast response are achieved under large errors, while low gain suppresses chattering under small errors. Second, based on a dynamic dead-zone threshold, sliding mode control is used outside the dead zone to achieve strong disturbance rejection, while switching to proportional control within the dead zone eliminates high-frequency switching noise.

[0053] It should be noted that this invention balances the dynamic response speed and steady-state accuracy of the control system through dynamic gain adjustment and smooth dual-mode switching, while reducing the impact of high-frequency oscillations on switching devices, thereby improving system reliability and operating efficiency. Its core lies in introducing a linear variable gain mechanism and dynamic dead-zone threshold determination to achieve dual-mode synergy between sliding mode control and proportional control, balancing strong disturbance rejection and low chattering characteristics. Key functions include: adaptive gain adjustment based on the zero-sequence current error amplitude, seamless dual-mode switching under dynamic dead-zone boundaries, and closed-loop feedback and hardware protection of the modulation signal. In a parallel inverter system, this invention dynamically adjusts the control gain coefficient through a linear variable gain mechanism based on real-time zero-sequence current feedback, combined with a dynamic dead-zone threshold to achieve dual-mode switching between sliding mode control and proportional control, thereby optimizing the inverter modulation signal and suppressing zero-sequence circulating current.

[0054] Furthermore, zero-sequence circulating current refers to the zero-sequence current component caused by common-mode voltage imbalance in a parallel inverter system, and its expression is:

[0055]

[0056] Where, Δi z V represents the zero-sequence current difference between each inverter. zero Z represents the common-mode voltage difference of the parallel inverters. p This is the equivalent zero-sequence impedance of a parallel system.

[0057] Dual-mode switching refers to a control strategy that dynamically switches between sliding mode control (outside the dead zone) and proportional control (inside the dead zone) based on the comparison between the zero-sequence current amplitude and the dead zone threshold.

[0058] In this embodiment of the invention, in step S100, the ratio of the common-mode voltage difference of the parallel inverter to the equivalent zero-sequence impedance of the parallel system is used as the zero-sequence current difference.

[0059] In one optional embodiment, the present invention acquires the neutral line current of each inverter using a high-precision current sensor, and extracts the zero-sequence current difference, Δi, through differential calculation. z The absolute value of the error is calculated and used as the basis for gain adjustment and mode switching. The linear variable gain mechanism adjusts the gain coefficient current_k proportionally according to the error amplitude to ensure high gain for fast convergence under large errors and low gain to suppress chattering under small errors.

[0060] Furthermore, the dynamic dead zone threshold (dead_zone) is dynamically tuned based on historical circulating current data and system impedance characteristics to avoid frequent switching problems caused by a fixed dead zone.

[0061] In this embodiment of the invention, step S200, which determines the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold, includes: when the zero-sequence current amplitude is greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the sliding mode control mode.

[0062] When the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the proportional control mode.

[0063] It should be noted that the dynamic dead zone threshold in this embodiment of the invention can be dynamically adjusted according to historical circulation data. When |Δi z When |>dead_zone, sliding mode control is adopted, and its sliding surface accumulates state variables by integrating historical errors to enhance disturbance rejection capability; when |Δi z When |≤dead_zone, switch to proportional control to eliminate steady-state deviation through linear feedback, while avoiding high-frequency switching noise caused by the sign function.

[0064] In this embodiment of the invention, step S200, which dynamically adjusts the control gain using a linear variable gain mechanism to generate the corresponding control quantity, includes: constructing an integral sliding mode surface function based on the zero-sequence current difference, expressed as:

[0065] s k =s k-1 +Δi z ·T s

[0066] Among them, s k-1 This is the sliding surface state variable of the previous control cycle, with an initial value of s0 = 0.

[0067] In this embodiment of the invention, step S200 further includes: when the zero-sequence current amplitude is greater than the dynamic dead zone threshold, the linear gain coefficient current_k is dynamically adjusted according to the zero-sequence current amplitude, and the linear variable gain coefficient is expressed as:

[0068]

[0069] Where, k min k is the minimum gain coefficient. max For the maximum gain coefficient, |Δi z | represents the absolute value of the current zero-sequence current, I ref The reference threshold for linear gain adjustment;

[0070] The generated sliding mode control output is represented as follows:

[0071] V smc = -current_k·sign(s) k )

[0072] Where sign is the sign function, V smc This is the sliding mode control quantity.

[0073] It should be noted that in the embodiments of the present invention, the minimum gain coefficient and the maximum gain coefficient are set according to the system power level and the number of inverters connected in parallel.

[0074] In this embodiment of the invention, step S200 further includes: switching to proportional control when the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, and the control output is expressed as:

[0075] V prop =-K p ·current_k·Δi z

[0076] Among them, K p V is the proportional control coefficient. prop This is a proportional control quantity.

[0077] In this embodiment of the invention, step S300, which involves superimposing the control quantity onto the modulation wave of the inverter's pulse width modulation (PWM), and then sending it to the inverter drive module after amplitude limiting for closed-loop dynamic control, includes: superimposing the control output onto the modulation wave of the inverter's three-phase PWM, and adjusting the common-mode voltage component to suppress circulating current, as shown below:

[0078]

[0079] Among them, V out To control the output voltage, These are the reference voltage values ​​for the modulation wave of the three-phase pulse width modulation of the inverter. These are the modulation waves of the three-phase pulse width modulation of the adjusted inverter.

[0080] It should be noted that the control output V out The energy of the zero-sequence loop current is suppressed by adjusting the common-mode voltage component and superimposed on the three-phase modulation wave of the inverter. The output limiter constrains V. out This prevents waveform distortion caused by overmodulation and reduces stress on switching devices.

[0081] For example, taking two inverters as an example, the specific implementation process of zero-sequence circulating current suppression in an inverter parallel operation system is as follows: Figure 2 As shown, steps A1 to A6 are included:

[0082] Step A1: System Initialization

[0083] Initialize the dual-mode control parameters for linear variable gain and dynamic dead time, with the following specific configuration:

[0084] Gain coefficient range: Set the minimum gain coefficient k min =0.1, maximum gain coefficient kmax =1.5; Dynamic dead zone threshold: Initial setting dead_zone = 0.2A; Proportional control coefficient: K p =0.3, used for linear feedback within the dead zone; control period: T s =1×10 -4 s (corresponding to a 10kHz switching frequency); Output limiting range: Set the output limiting range to [-1.5, 1.5] to prevent overmodulation.

[0085] Step A2: Collect the zero-sequence circulating current difference

[0086] The three-phase current of each inverter is collected in real time using a high-precision current sensor. a i b i c Calculate the zero-sequence current of each inverter:

[0087]

[0088] Where N is the number of parallel inverters, the zero-sequence current difference is calculated as follows:

[0089]

[0090] If |Δi z |>dead_zone, activates the dual-mode control algorithm, otherwise maintains the control output of the previous cycle; when multiple inverters are connected in parallel, the zero-sequence current difference is taken as the maximum difference of the zero-sequence current of all inverters.

[0091] Step A3: Construct the sliding surface function

[0092] Constructing an integral sliding mode surface function based on zero-sequence current difference:

[0093] s k =s k-1 +Δi z ·T s

[0094] Among them, s k-1 This is the sliding surface state variable of the previous control cycle, with an initial value of s0 = 0.

[0095] Step A4: Design of the dual-modal control law

[0096] The control mode is switched based on the relationship between the zero-sequence current difference and the dead-time threshold.

[0097] Outside the dead zone (sliding mode control): when |Δi z |>dead_zone, calculate the linear variable gain coefficient:

[0098]

[0099] Where I ref =0.1A, generating sliding mode control output:

[0100] V smc = -current_k·sign(s) k )

[0101] Within the dead zone (proportional control): when |Δi z If |≤dead_zone, switch to proportional control:

[0102] V prop =-K p ·current_k·Δi z

[0103] Step A5: Overlay control output and limiting protection

[0104] Control output V out (V smc or V prop Superimposed on the inverter's three-phase PWM modulation wave V a,b,cref Adjust the common-mode voltage component to suppress circulating current:

[0105]

[0106] V is constrained by the limiter out Within the range of [-1.5, 1.5], prevent modulation wave distortion.

[0107] Step A6: Feedback and Dynamic Dead Zone Update

[0108] Execute at the end of each control cycle:

[0109] Circulation state detection: If |Δi z If the zone is dead, continue control; otherwise, maintain V. out =0 until the circulation exceeds the limit again;

[0110] Dynamic dead zone tuning: The dead zone threshold is updated based on the average circulation value over the past N=100 cycles, expressed as:

[0111]

[0112] The dead zone range is limited to [0.1A, 0.5A] to avoid oscillations caused by an excessively small threshold or control lag caused by an excessively large threshold.

[0113] It should be noted that this invention detects the zero-sequence current difference of each inverter in real time and calculates its absolute value; designs a linear variable gain coefficient to dynamically adjust the control gain according to the zero-sequence current error amplitude; sets a dynamic dead-zone threshold and optimizes the dead-zone boundary in real time based on system operating conditions; and constructs a dual-mode control law, using sliding mode control outside the dead zone to achieve fast response, and switching to proportional control within the dead zone to suppress high-frequency oscillations. The linear variable gain mechanism achieves dynamic adaptation between control strength and error amplitude, overcoming the response lag and steady-state overshoot problems of traditional sliding mode fixed gain; the dynamic dead-zone dual-mode switching reduces the number of mode jumps, suppressing high-frequency oscillations, while retaining the strong robustness of sliding mode control outside the dead zone. This invention not only excels in suppressing zero-sequence circulating current but also has advantages such as lower chattering and better dynamic response.

[0114] Example 2 is an embodiment of the present invention. This embodiment differs from the first embodiment in that it provides a zero-sequence circulating current control system for a parallel inverter operation system, comprising:

[0115] The data acquisition and calculation module is used to sample the output current of each parallel inverter in real time and calculate the zero-sequence current difference and its absolute value.

[0116] The control mode switching module is used to preset the dynamic dead zone threshold, determine the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold, and dynamically adjust the control gain in combination with the linear variable gain mechanism to generate the corresponding control quantity.

[0117] The control module is used to superimpose the control quantity onto the modulation wave of the inverter pulse width modulation, and after limiting, send it to the inverter drive module for closed-loop dynamic control.

[0118] Specifically, each module of the zero-sequence circulating current control system of the inverter parallel operation system in this embodiment implements the steps of the zero-sequence circulating current control method of the inverter parallel operation system in Embodiment 1, for example:

[0119] In one implementation, the zero-sequence circulating current control system of the inverter parallel operation system can perform the following steps: taking the ratio of the common-mode voltage difference of the parallel inverters to the equivalent zero-sequence impedance of the parallel system as the zero-sequence current difference.

[0120] When the zero-sequence current amplitude is greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is sliding mode control.

[0121] When the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the proportional control mode.

[0122] An integral sliding mode surface function is constructed based on the zero-sequence current difference, and is expressed as follows:

[0123] sk =s k-1 +Δi z ·T s

[0124] Among them, s k-1 This is the sliding surface state variable of the previous control cycle, with an initial value of s0 = 0.

[0125] When the zero-sequence current amplitude is greater than the dynamic dead-zone threshold, the linear gain coefficient current_k is dynamically adjusted according to the zero-sequence current amplitude. The linear variable gain coefficient is expressed as:

[0126]

[0127] Where, k min k is the minimum gain coefficient. max For the maximum gain coefficient, |Δi z | represents the absolute value of the current zero-sequence current, I ref The reference threshold for linear gain adjustment;

[0128] The generated sliding mode control output is represented as follows:

[0129] V smc = -current_k·sign(s) k )

[0130] Where sign is the sign function, V smc This is the sliding mode control quantity.

[0131] When the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, the control switches to proportional control, and the control output is expressed as follows:

[0132] V prop =-K p ·current_k·Δi z

[0133] Among them, K p V is the proportional control coefficient. prop This is a proportional control quantity.

[0134] The control output is superimposed on the modulation wave of the inverter's three-phase pulse width modulation, and the common-mode voltage component is adjusted to suppress circulating current, as shown below:

[0135]

[0136] Among them, V out To control the output voltage, These are the reference voltage values ​​for the modulation wave of the three-phase pulse width modulation of the inverter. These are the modulation waves of the three-phase pulse width modulation of the adjusted inverter.

[0137] It should be noted that the embodiments of the present invention utilize adaptive gain adjustment based on the zero-sequence current error amplitude, seamless dual-mode switching under dynamic dead-zone boundaries, and closed-loop feedback and hardware protection of the modulation signal. Through dynamic gain adjustment and smooth dual-mode switching, the dynamic response speed and steady-state accuracy of the control system are balanced, while reducing the impact of high-frequency oscillations on switching devices, thereby improving system reliability and operating efficiency. The introduction of a linear variable gain mechanism and dynamic dead-zone threshold determination enables dual-mode synergy between sliding mode control and proportional control, balancing strong anti-interference capability with low chattering characteristics.

[0138] Example 3, referring to Figures 3-9 This is one embodiment of the present invention. This embodiment takes two inverters as an example and conducts a simulation experiment in the MATLAB-Simulink environment to verify the beneficial effects of the present invention.

[0139] In this embodiment, the inverter parallel operation system topology is as follows: Figure 3 As shown, where U dc This is a DC voltage source; S is a switching element, whose subscripts indicate the phase sequence and corresponding inverter number from left to right; the AC output filter inductors for inverter 1 and inverter 2 are L1 and L2 respectively; the grid simulation inductor is represented by L... NET The three-phase voltages (a, b, and c) of the power grid are represented by e. a e b e c This is indicated. In this embodiment, the circulating current suppression control is activated after 1.5 seconds. The simulation results are as follows. Figures 4 to 9 As shown.

[0140] like Figure 4 , Figure 5 , Figure 6 As shown, when using traditional sliding mode control, super-spiral sliding mode control, and the control proposed in this invention, the zero-sequence circulating current amplitude of the system is almost zero, and the circulating current suppression effect is good. Figure 7 , Figure 8 , Figure 9 As shown, when using traditional sliding mode control, the control system outputs a chattering amplitude of approximately 0.6A. When using superspiral sliding mode control, the control system outputs a chattering amplitude of approximately 0.1A. However, when using the control proposed in this invention, the control system outputs a chattering amplitude of approximately 0.01A.

[0141] Compared with traditional technologies, this invention achieves dynamic adaptation of control strength and error amplitude through a linear variable gain mechanism, overcoming the response lag and steady-state overshoot problems of traditional sliding mode control with fixed gain. It reduces the number of mode jumps and suppresses high-frequency oscillations through dynamic dead-zone dual-mode switching, while retaining the strong robustness of sliding mode control outside the dead zone. By linearly adjusting the gain with the zero-sequence current error amplitude, it achieves high gain for fast response under large errors and low gain to suppress chattering under small errors. Based on a dynamic dead-zone threshold, sliding mode control is used outside the dead zone to achieve strong disturbance rejection, while switching to proportional control within the dead zone eliminates high-frequency switching noise. Simulation results show that compared with traditional sliding mode control, this invention can significantly suppress zero-sequence circulating current, while keeping the steady-state error within ±0.05A, significantly improving system stability and operating efficiency. It not only excels in suppressing zero-sequence circulating current but also has advantages such as less chattering and better dynamic response.

[0142] This embodiment also provides an electronic device applicable to the zero-sequence circulating current control method of inverter parallel operation systems, including:

[0143] The system includes a memory and a processor. The memory stores computer-executable instructions, and the processor executes these instructions to implement the zero-sequence circulating current control method for a parallel inverter system as proposed in the above embodiments.

[0144] Example 4: This example provides a storage medium on which a computer program is stored. When the program is executed by a processor, it implements the zero-sequence circulating current control method for implementing a parallel operation system of inverters as proposed in the above examples.

[0145] The storage medium proposed in this embodiment and the zero-sequence circulating current control method for realizing the parallel operation system of inverters proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0146] From the above description of the embodiments, those skilled in the art will clearly understand that the embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0147] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0148] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0149] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0150] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0151] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0152] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A zero-sequence circulating current control method for a parallel inverter system, characterized in that, include: The output current of each parallel inverter is sampled in real time, and the zero-sequence current difference is calculated. A preset dynamic dead zone threshold is used to determine the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold. The control gain is dynamically adjusted in combination with the linear variable gain mechanism to generate the corresponding control quantity. The control quantity is superimposed on the modulation wave of the inverter pulse width modulation, and after being limited, it is sent to the inverter drive module for closed-loop dynamic control.

2. The zero-sequence circulating current control method for a parallel inverter system as described in claim 1, characterized in that: The ratio of the common-mode voltage difference of the parallel inverter to the equivalent zero-sequence impedance of the parallel system is taken as the zero-sequence current difference.

3. The zero-sequence circulating current control method for a parallel inverter system as described in claim 2, characterized in that, The control mode of the inverter parallel operation system is determined based on the zero-sequence current amplitude and the dynamic dead zone threshold. When the zero-sequence current amplitude is greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the sliding mode control mode. When the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, the control mode of the inverter parallel operation system is the proportional control mode.

4. The zero-sequence circulating current control method for a parallel inverter system as described in claim 3, characterized in that, The control gain is dynamically adjusted by combining a linear variable gain mechanism to generate corresponding control quantities, including: constructing an integral sliding mode surface function based on the zero-sequence current difference, expressed as: s k =s k-1 +Δi z ·T s Among them, s k-1 This is the sliding surface state variable of the previous control cycle, with an initial value of s0 = 0.

5. The zero-sequence circulating current control method for a parallel inverter system as described in claim 4, characterized in that, Also includes: When the zero-sequence current amplitude is greater than the dynamic dead-zone threshold, the linear gain coefficient current_k is dynamically adjusted according to the zero-sequence current amplitude. The linear variable gain coefficient is expressed as: Where, k min k is the minimum gain coefficient. max For the maximum gain coefficient, |Δi z | represents the absolute value of the current zero-sequence current, I ref The reference threshold for linear gain adjustment; The generated sliding mode control output is represented as follows: V smc =-current_k·sign(s k ) Where sign is the sign function, V smc This is the sliding mode control quantity.

6. The zero-sequence circulating current control method for a parallel inverter system as described in claim 5, characterized in that, Also includes: When the zero-sequence current amplitude is not greater than the dynamic dead zone threshold, the control switches to proportional control, and the control output is expressed as follows: V prop =-K p ·current_k·Δi z Among them, K p V is the proportional control coefficient. prop This is a proportional control quantity.

7. The zero-sequence circulating current control method for a parallel inverter system as described in claim 6, characterized in that, The control quantity is superimposed on the modulation wave of the inverter's pulse width modulation, and after being limited, it is sent to the inverter drive module for closed-loop dynamic control. This includes: superimposing the control output on the modulation wave of the inverter's three-phase pulse width modulation, adjusting the common-mode voltage component to suppress circulating current, as expressed as: Among them, V out To control the output voltage, These are the reference voltage values ​​for the modulation wave of the three-phase pulse width modulation of the inverter. These are the modulation waves of the three-phase pulse width modulation of the adjusted inverter.

8. A zero-sequence circulating current control system for a parallel inverter system, applied to the method described in any one of claims 1-7, characterized in that, include: The data acquisition and calculation module is used to sample the output current of each parallel inverter in real time and calculate the zero-sequence current difference and its absolute value. The control mode switching module is used to preset the dynamic dead zone threshold, determine the control mode of the inverter parallel operation system based on the zero-sequence current amplitude and the dynamic dead zone threshold, and dynamically adjust the control gain in combination with the linear variable gain mechanism to generate the corresponding control quantity. The control module is used to superimpose the control quantity onto the modulation wave of the inverter pulse width modulation, and after amplitude limiting, send it to the inverter drive module for closed-loop dynamic control.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the zero-sequence circulating current control method for the inverter parallel operation system according to any one of claims 1 to 7.

10. A computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the zero-sequence circulating current control method for an inverter parallel operation system according to any one of claims 1 to 7.

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