Balanced current controlled self-synchronizing voltage source control method and system

Abstract

The invention relates to the technical field of self-synchronizing voltage source control, and discloses a balance current controlled self-synchronizing voltage source control method and system. The method comprises the following steps: acquiring and preprocessing operation data of a grid-connected inverter to obtain active / reactive components of voltage and current of a filter element; generating a three-phase terminal voltage instruction of the self-synchronizing voltage source based on the components, and determining a current instruction signal in combination with the grid-connected voltage; a three-phase modulation signal is generated through adjustment of a PIR controller and coordinate inverse transformation, then a filter inductance value is calculated according to the ripple characteristic of the modulation signal and a switching period, a filter capacitance value is determined by combining resonant frequency, and finally accurate control of the self-synchronizing voltage source is realized according to a filter parameter. By dynamically calculating the matching parameters of the filter inductance and the filter capacitance, the active regulation and control capability of the output impedance characteristic of the inverter is enhanced, and the resonance risk during the impedance change of the power grid is effectively inhibited. The technical problem that the stability is limited due to insufficient impedance regulation and control in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of self-synchronous voltage source control, and in particular to a self-synchronous voltage source control method and system for balanced current control. Background Art

[0002] As the penetration rate of renewable energy generation systems in the power system continues to rise, the control strategies of grid-connected inverters, the core interface devices connecting distributed power sources with the power grid, directly impact the stable operation of the power grid. In traditional control architectures, inverters based on PQ control or droop control can achieve basic power transmission functions, but they often struggle to provide the necessary inertia and damping support when dealing with dynamic conditions such as grid voltage fluctuations and frequency offsets. This characteristic is particularly prominent in scenarios with weak power grids or a high proportion of renewable energy access. To enhance the active support capabilities of power electronic equipment for the power grid, Virtual Synchronous Generator (VSG) technology has successfully endowed inverters with inertia response and primary frequency modulation capabilities by simulating the electromechanical transient characteristics of synchronous generators, becoming an important technical approach to enhancing power grid stability.

[0003] However, traditional VSG control methods primarily focus on simulating the mechanical motion equations of the outer power loop, introducing rotor inertia and damping coefficients to achieve self-synchronous operation of the grid-connected inverter. However, in actual engineering applications, the traditional VSG architecture's insufficient inner-loop current control capabilities become apparent when grid voltage experiences three-phase imbalance, harmonic distortion, or asymmetric faults. Due to the lack of an effective negative-sequence and harmonic suppression mechanism, the grid-connected current is susceptible to distortion caused by grid voltage disturbances. In severe cases, this can even trigger overcurrent protection, leading to the disconnection of new energy generators from the grid.

[0004] Therefore, for current control, a composite control strategy combining a PI controller with quasi-resonant (QR) control is commonly used. However, the PI controller in this approach suffers from tracking errors in AC signals, while conventional QR controllers have a narrow resonant bandwidth, making it difficult to achieve full-band harmonic suppression under multi-frequency disturbance conditions. Furthermore, existing technologies have limited ability to actively control the inverter's output impedance characteristics, which can easily lead to resonance risks when the grid impedance changes, restricting the system's stable operation under complex grid conditions. Summary of the Invention

[0005] The present invention provides a self-synchronous voltage source control method and system with balanced current control, which solves the technical problem that the existing technology has limited active regulation capability of the inverter output impedance characteristics, easily induces resonance risk when the grid impedance changes, and restricts the stable operation boundary of the system under complex grid conditions.

[0006] A first aspect of the present invention provides a method for controlling a self-synchronous voltage source with balanced current control, comprising:

[0007] Obtaining and preprocessing the operating data of the grid-connected inverter to generate the active and reactive components corresponding to the filter capacitor voltage, filter inductor current, and filter capacitor current, respectively;

[0008] Determining a three-phase terminal voltage command of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, and determining a current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operating data;

[0009] The current reference value of the current command signal, the active component and the reactive component of the filter inductor current are sequentially passed through a proportional-integral resonant controller and an inverse coordinate transformation to generate a three-phase modulation signal;

[0010] Calculating a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulated signal, and determining a filter capacitance value based on the filter inductance value and a resonant frequency;

[0011] The self-synchronous voltage source is controlled according to the value range of the filter inductance and the filter capacitance.

[0012] Optionally, the acquiring and preprocessing the operation data of the grid-connected inverter to generate active components and reactive components corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, includes:

[0013] Collecting operating data of the grid-connected inverter; wherein the operating data includes filter capacitor voltage, filter inductor current and grid voltage;

[0014] Performing coordinate transformation on the filter capacitor voltage and the filter inductor current to generate active components and reactive components corresponding to the filter capacitor voltage and the filter inductor current, respectively;

[0015] The active component and reactive component corresponding to the filter capacitor voltage and the filter inductor current are discretized, and the active component and reactive component corresponding to the filter capacitor current are determined based on the discretized filter capacitor voltage and filter inductor current.

[0016] Optionally, determining the three-phase terminal voltage instructions of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, and determining the current instruction signal based on the three-phase terminal voltage instructions and the grid-connected voltage corresponding to the operation data includes:

[0017] Determining the active component and reactive component of the output current based on the active component and reactive component corresponding to the filter inductor current and the filter capacitor current, respectively;

[0018] Calculating average active power and average reactive power based on the active component and reactive component corresponding to the filter capacitor voltage and the output current, respectively, and harmonic filtering parameters;

[0019] The average active power and the active power command corresponding to the grid-connected inverter are applied to an active frequency control equation to generate an angular frequency of the self-synchronous voltage source;

[0020] determining a vector angle of the self-synchronous voltage source based on the angular frequency and the Laplace operator of the self-synchronous voltage source;

[0021] The average reactive power and the reactive power command corresponding to the grid-connected inverter are applied to a reactive voltage control equation to generate a terminal voltage amplitude command of a self-synchronous voltage source;

[0022] The vector angle and terminal voltage amplitude command of the self-synchronous voltage source are passed through the three-phase voltage equation to generate the three-phase terminal voltage command of the self-synchronous voltage source;

[0023] A current command signal is determined based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operation data.

[0024] Optionally, the step of sequentially passing the current reference value of the current command signal, the active component and the reactive component of the filter inductor current through a proportional-integral resonant controller and coordinate inverse transformation to generate a three-phase modulation signal includes:

[0025] Performing coordinate transformation on the current command signal to generate a current reference value; wherein the current reference value includes a first current reference value and a second current reference value;

[0026] calculating a first difference between the first current reference value and an active component of the filter inductor current;

[0027] calculating a second difference between the second current reference value and a reactive component of the filter inductor current;

[0028] inputting the first difference and the second difference into a proportional-integral resonant controller respectively to generate a pulse width modulation control signal;

[0029] The pulse width modulation control signal is subjected to coordinate inverse transformation to generate a three-phase modulation signal.

[0030] Optionally, the calculating a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulation signal, and determining a filter capacitance value based on the filter inductance value and the resonant frequency includes:

[0031] Calculating a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulation signal;

[0032] Establishing a current loop open-loop transfer function of the self-synchronous voltage source; wherein the current loop open-loop transfer function includes a total delay time and a current transfer function;

[0033] determining a phase of the current open-loop transfer function based on the phase angle of the current open-loop transfer function, the phase angle of the current transfer function, the total delay time, and the angular frequency;

[0034] evaluating the phase of the current loop open-loop transfer function to generate a system phase stability margin;

[0035] Determining a resonant frequency stability domain range using the total delay time, the phase angle of the current loop open-loop transfer function, and the system phase stability margin;

[0036] Based on the stable domain of the resonant frequency, determine the value range of the blocking frequency;

[0037] Performing a weighted geometric operation on the range of the blocking frequency and the resonant frequency to determine the resonant frequency;

[0038] A filter capacitance value is determined based on the filter inductance value and the resonant frequency.

[0039] Optionally, determining a filter capacitance value based on the filter inductance value and the resonant frequency includes:

[0040] The filter capacitance value is calculated using the filter inductance value and the resonant frequency; wherein the calculation formula of the filter capacitance value is:

[0041] ;

[0042] Where, L represents the filter inductance value, Indicates the resonant frequency.

[0043] A second aspect of the present invention provides a balanced current controlled self-synchronous voltage source control system, comprising:

[0044] An acquisition module is used to acquire and pre-process the operating data of the grid-connected inverter to generate active and reactive components corresponding to the filter capacitor voltage, filter inductor current, and filter capacitor current, respectively;

[0045] a current command signal module, configured to determine a three-phase terminal voltage command of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, and to determine a current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operating data;

[0046] a conversion module, configured to sequentially pass the current reference value of the current command signal, the active component and the reactive component of the filter inductor current through a proportional-integral resonant controller and coordinate inverse transformation to generate a three-phase modulation signal;

[0047] a calculation module, configured to calculate a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulated signal, and determine a filter capacitance value based on the filter inductance value and a resonant frequency;

[0048] A control module is used to control the self-synchronous voltage source according to the value range of the filter inductance value and the filter capacitance value.

[0049] Optionally, the acquisition module includes:

[0050] The acquisition submodule is used to collect the operating data of the grid-connected inverter; wherein the operating data includes the filter capacitor voltage, the filter inductor current, the grid voltage and the bridge arm inductor current;

[0051] a conversion submodule, configured to perform coordinate transformation on the filter capacitor voltage and the filter inductor current to generate active components and reactive components corresponding to the filter capacitor voltage and the filter inductor current, respectively;

[0052] The processing submodule is used to discretize the active component and reactive component corresponding to the filter capacitor voltage and the filter inductor current, and determine the active component and reactive component corresponding to the filter capacitor current based on the discretized filter capacitor voltage and filter inductor current.

[0053] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the self-synchronous voltage source control method for balanced current control as described in any one of the above items is implemented.

[0054] A fourth aspect of the present invention provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the balanced current controlled self-synchronous voltage source control method as described in any one of the above items.

[0055] It can be seen from the above technical solutions that the present invention has the following advantages:

[0056] The present invention collects and preprocesses grid-connected inverter operating data to obtain the active and reactive components of the filter element voltage and current. Based on these components, a three-phase terminal voltage command for the self-synchronous voltage source is generated, and the current command signal is determined in combination with the grid-connected voltage. A three-phase modulation signal is generated through PIR controller regulation and coordinate inverse transformation. The filter inductance value is then calculated based on the ripple characteristics and switching period of the modulation signal, and the filter capacitor value is determined in combination with the resonant frequency. Finally, precise control of the self-synchronous voltage source is achieved based on the filter parameters, forming a complete process of "data processing-command generation-parameter design-closed-loop control". By dynamically calculating the matching parameters of the filter inductor and capacitor (combining ripple characteristics and resonant frequency), the present invention enhances the active control capability of the inverter output impedance characteristics and effectively suppresses the risk of resonance when the grid impedance changes. At the same time, based on the control logic of the self-synchronous voltage source and the harmonic suppression capability of the PIR controller, the system's adaptability to complex grid conditions (such as voltage fluctuations and harmonic interference) is improved, significantly broadening the stable operation boundary of the inverter, and solving the stability problem caused by insufficient impedance control in traditional technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0058] Figure 1 A flowchart of a method for controlling a self-synchronous voltage source with balanced current control provided in the first embodiment of the present invention;

[0059] Figure 2 A control principle diagram of a self-synchronous voltage source with balanced current control provided in the first embodiment of the present invention;

[0060] Figure 3 A schematic diagram of a grid-connected inverter provided in Embodiment 1 of the present invention;

[0061] Figure 4 This is a structural block diagram of a balanced current controlled self-synchronous voltage source control system provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0062] The embodiments of the present invention provide a self-synchronous voltage source control method and system with balanced current control, which is used to solve the technical problem that the existing technology has limited active regulation capability of the inverter output impedance characteristics, easily induces resonance risk when the grid impedance changes, and restricts the stable operation boundary of the system under complex grid conditions.

[0063] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0064] See also Figures 1 to 3 , Figure 1 This is a flowchart of the steps of a self-synchronous voltage source control method for balanced current control provided in Example 1 of the present invention.

[0065] The present invention provides a method for controlling a self-synchronous voltage source with balanced current control, comprising the following steps:

[0066] Step 101: Acquire and pre-process the operating data of the grid-connected inverter to generate active components and reactive components corresponding to the filter capacitor voltage, filter inductor current, and filter capacitor current, respectively.

[0067] In the embodiments of this invention, a grid-connected inverter refers to the core power electronic device that connects distributed power sources (such as solar photovoltaic, wind power, and energy storage systems) to the public power grid. Its primary function is to convert the DC power (or AC power with unstable frequency or voltage) output by the distributed power source into AC power with the same frequency, phase, and amplitude as the power grid, enabling smooth transmission of power to the grid. It also provides power regulation, grid support (such as voltage and frequency stabilization), and protection, serving as a bridge for renewable energy access to the grid.

[0068] Operation data refers to various real-time or historical monitoring data generated by the grid-connected inverter during operation, covering electrical parameters, state parameters, environmental parameters, etc. Among them, the operation data in the present invention includes filter capacitor voltage, filter inductor current and grid voltage.

[0069] Preprocessing refers to the process of performing preliminary processing on the collected original operating data; the preprocessing used in the present invention includes filtering processing and discretization processing.

[0070] The filter capacitor voltage refers to the filter capacitor in the LC (Inductor-Capacitor) filter on the output side of the grid-connected inverter. Voltage across both ends In the inverter's main circuit, the filter capacitor and filter inductor (L) form an LC (Inductor-Capacitor) filter network. Its function is to smooth the PWM (Pulse Width Modulation) pulse voltage output by the inverter, suppress high-frequency harmonics, and make the output voltage waveform closer to a sine wave. The filter capacitor voltage is one of the key parameters for calculating grid-connected power and generating current commands.

[0071] Filter inductor current refers to the current flowing through the filter inductor L in the LC filter. Filter inductor L and filter capacitor The filter inductor current is collected to monitor the inverter's output current in real time, providing feedback for the PIR controller to achieve precise regulation.

[0072] Filter capacitor current refers to the current flowing through the filter capacitor in the LC filter. The current is the difference between the filter inductor current and the grid-connected output current, reflecting the charge and discharge status of the capacitor. By calculating the filter capacitor current, the high-frequency components in the grid-connected power calculation can be corrected, ensuring the accuracy of the average active and reactive power.

[0073] The active component refers to the current / voltage component in an AC circuit that actually performs work. In a grid-connected system, the active component determines the active power transmitted by the inverter to the grid. Control of the active component is achieved through the active-frequency loop, directly impacting the stability of the grid frequency.

[0074] Reactive power refers to the current / voltage component of an AC circuit that does no work and only serves to establish a magnetic field. This reactive power determines the reactive power transmitted by the inverter to the grid. Control of this reactive power is achieved through the reactive-voltage loop, directly impacting grid voltage stability.

[0075] Collect filter capacitance through sensor The system then collects operational data such as the three-phase voltage of the filter inductor, the three-phase current of the filter inductor, and the voltage and current at the grid connection point. These data are then preprocessed, including filtering to eliminate high-frequency noise such as PWM (Pulse Width Modulation) switching ripple and performing discretization conversion to adapt to digital control chip operations. Subsequently, the preprocessed three-phase AC quantities are converted into DC quantities in the dq coordinate system using dq coordinate transformation. The d-axis component is the active component (reflecting the energy transfer characteristics of actual work), and the q-axis component is the reactive component (reflecting the magnetic field establishment characteristics of energy exchange). Specifically, the active / reactive components of the filter capacitor voltage are used to accurately calculate power, the corresponding components of the filter inductor current serve as feedback for current loop control, and the corresponding components of the filter capacitor current are used to correct high-frequency errors in power calculations. Ultimately, these components provide reliable basic parameters for subsequent power and current loop control, ensuring the accuracy and stability of the control algorithm.

[0076] Furthermore, step 101 includes the following sub-steps:

[0077] S11. Collecting operating data of the grid-connected inverter; wherein the operating data includes filter capacitor voltage, filter inductor current and grid-connected voltage.

[0078] In the embodiment of the present invention, the grid-connected inverter filter capacitor is collected Voltage and filter inductors Current ; Collect grid connection point voltage With current .

[0079] S12. Perform coordinate transformation on the filter capacitor voltage and the filter inductor current to generate active components and reactive components corresponding to the filter capacitor voltage and the filter inductor current, respectively.

[0080] In the embodiments of the present invention, coordinate transformation refers to a mathematical tool used to convert the representation of physical quantities between different coordinate systems, thereby simplifying problem analysis and control design. In the field of power electronics and grid-connected inverter control, coordinate transformation specifically refers to the process of converting three-phase AC quantities (such as voltage and current) from the natural coordinate system (abc) to the rotating coordinate system (dq). Its core function is to convert time-varying sinusoidal AC signals into constant DC signals, facilitating zero-error control.

[0081] Voltage on filter capacitor and filter inductor current conduct Coordinate transformation to obtain the filter capacitor voltage of Quantity and (i.e. active and reactive components), and the filter inductor current of Quantity and .

[0082] S13. Discretize the active component and reactive component corresponding to the filter capacitor voltage and the filter inductor current, respectively, and determine the active component and reactive component corresponding to the filter capacitor current based on the discretized filter capacitor voltage and filter inductor current.

[0083] In the embodiments of the present invention, discretization refers to the process of converting continuous-time signals into discrete-time series. This involves converting analog signals into a computer-processable digital form through equal-interval sampling (e.g., collecting data every 100 μs) and quantization (converting analog quantities into digital quantities). In grid-connected inverter control, since the actual control system uses a digital controller, continuous electrical quantities (such as voltage and current) must be discretized.

[0084] The filter capacitor voltage of Quantity and Discretize into and , let the filter capacitor current Quantity and The discrete sequence of , the filter capacitor current can be calculated by the following equation: :

[0085]

[0086] Where, For filter capacitors The value of is the sampling frequency of the grid-connected inverter, is the number of discrete sequence points, and is a natural number, ; 、 They represent the active component (d-axis in the dq coordinate system) and reactive component (q-axis in the dq coordinate system) of the filter capacitor current at the n-1th sampling moment respectively; 、 They represent the active component (d-axis in the dq coordinate system) and reactive component (q-axis in the dq coordinate system) of the filter capacitor voltage at the n-kth sampling moment, respectively.

[0087] By discrete sequence and Get the filter capacitor current Quantity and .

[0088] Step 102: Determine the three-phase terminal voltage instructions of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively; and determine the current instruction signal based on the three-phase terminal voltage instructions and the grid-connected voltage corresponding to the operating data.

[0089] In the embodiment of the present invention, the self-synchronous voltage source refers to a virtual voltage source that achieves autonomous synchronization with the power grid by simulating the characteristics of a synchronous generator (such as moment of inertia and damping coefficient). Its core is to generate a voltage reference that matches the frequency and phase of the power grid through a power loop.

[0090] The three-phase terminal voltage command refers to the three-phase voltage reference value output by the self-synchronous voltage source, which is jointly determined by the active-frequency control and reactive-voltage control and is used to drive the inverter power switch.

[0091] The current command signal refers to the current reference value generated by the balanced current control algorithm based on the deviation between the three-phase terminal voltage command and the actual grid-connected voltage. It is used to guide the current loop to accurately track the target current.

[0092] First, based on the active / reactive components of the filter capacitor voltage, filter inductor current, and filter capacitor current (obtained through coordinate transformation and discretization), the angular frequency of the self-synchronous voltage source is calculated using the active-frequency droop characteristics and reactive-voltage droop characteristics, thereby generating the three-phase terminal voltage command. Then, combined with the collected grid-connected voltage (reflecting the actual grid state), the current command signal is calculated using a balanced current control algorithm. This ensures that the inverter output current tracks the power command while suppressing harmonics caused by grid disturbances (such as voltage imbalance). This completes the closed loop from power command to current control, ensuring stable inverter operation even under non-ideal grid conditions.

[0093] Furthermore, step 102 includes the following sub-steps:

[0094] S21. Determine the active component and reactive component of the output current based on the active component and reactive component corresponding to the filter inductor current and the filter capacitor current, respectively.

[0095] In the embodiment of the present invention, the output current refers to the current that the grid-connected inverter finally outputs to the outside (such as the public grid, load, etc.) after conversion, control and regulation by the internal circuit.

[0096] The output current can be obtained from the following equation: Quantity and :

[0097]

[0098] Where, and They represent the active component (d-axis in the dq coordinate system) and reactive component (q-axis in the dq coordinate system) of the filter capacitor current respectively; and Represent the filter inductor current respectively The active component (d-axis of the dq coordinate system) and the reactive component (q-axis of the dq coordinate system) are:

[0099] S22. Calculate the average active power and the average reactive power according to the active component and reactive component corresponding to the filter capacitor voltage and the output current, respectively, and harmonic filtering parameters.

[0100] It should be noted that according to Figure 2 The control principle diagram of active-frequency power control and reactive-voltage control, and finally the terminal voltage amplitude instruction of the self-synchronous voltage source is obtained. and the vector angle of the self-synchronous voltage source First calculate the average active power and average reactive power .

[0101] In the embodiment of the present invention, average active power refers to the average energy rate actually consumed or transmitted in an AC circuit within one cycle, reflecting the average ability of converting electrical energy into other forms of energy (such as mechanical energy and thermal energy).

[0102] Average reactive power refers to the average value of energy exchange in an AC circuit within one cycle (no actual energy is consumed, it is only used to establish a magnetic field / electric field), reflecting the round-trip exchange rate between electrical energy and magnetic field energy / electric field energy.

[0103] Based on the above results, the average active power can be calculated by the following equation: and average reactive power :

[0104]

[0105] Where, is the harmonic number to be filtered out; is the quality factor; is the angular frequency of the harmonic to be filtered out; is the time constant; s is the Laplace operator; and Respectively represents the output current Quantity; and Represent the filter capacitor voltage of Quantity.

[0106] S23. The average active power and the active power command corresponding to the grid-connected inverter are applied to the active frequency control equation to generate the angular frequency of the self-synchronous voltage source.

[0107] In the embodiment of the present invention, angular frequency, also known as angular velocity, is a physical quantity that describes the speed of periodic changes of an object or physical quantity, and is often used in the electrical field to represent the rate of change of alternating current.

[0108] Active power command refers to the pre-set power reference value to achieve the active power transmission target between the grid-connected inverter and the grid (or load).

[0109] Get the average active power and average reactive power Then, the angular frequency of the self-synchronous voltage source is obtained through the active-frequency control equation and the reactive-voltage control equation. and terminal voltage amplitude command The specific calculation steps are as follows.

[0110] Based on average active power and active power command of the grid-connected inverter , the angular frequency of the self-synchronous voltage source is obtained through the active power-frequency control equation , the active power-frequency control equation is as follows:

[0111] ;

[0112] Where, is the rated angular frequency; is the active power-frequency control droop coefficient; is the reactive-voltage control droop coefficient; is the virtual moment of inertia; is the vector angle of the self-synchronous voltage source; s is the Laplace operator; Indicates active power instruction; Indicates the average active power.

[0113] S24. Determine a vector angle of the self-synchronous voltage source based on the angular frequency and the Laplace operator of the self-synchronous voltage source.

[0114] In the embodiment of the present invention, the Laplace operator refers to the Laplace operator used to describe the distribution characteristics of physical quantities such as electric fields and magnetic fields in electromagnetism.

[0115] The vector angle is the angle of a vector in a plane or space relative to a reference direction (usually a coordinate axis). In power electronics, particularly in three-phase AC systems, the vector angle typically refers to the angle of the voltage or current vector relative to the d-axis in a synchronously rotating coordinate system (such as the dq coordinate system).

[0116] The vector angle of the self-synchronous voltage source is obtained according to the following equation:

[0117]

[0118] Where, is the vector angle of the self-synchronous voltage source; s is the Laplace operator; Indicates the angular frequency.

[0119] S25. Generate a terminal voltage amplitude command of the self-synchronous voltage source by applying the reactive power control equation to the average reactive power and the reactive power command corresponding to the grid-connected inverter.

[0120] In the embodiment of the present invention, the reactive power instruction refers to a pre-set reactive power reference value to meet the requirements of grid voltage support, power factor regulation, etc.

[0121] The terminal voltage amplitude command refers to the voltage amplitude reference value generated by the reactive-voltage control loop in the self-synchronous voltage source control to achieve matching of the inverter output voltage with the grid voltage.

[0122] Based on average reactive power and the reactive power command given by the grid-connected inverter , the terminal voltage amplitude command of the self-synchronous voltage source is obtained through the reactive-voltage control equation , the equation is written as follows:

[0123] ;

[0124] Where, is the voltage instruction; is the reactive-voltage control droop coefficient; is the reactive power instruction; is the average reactive power.

[0125] S26. The vector angle and terminal voltage amplitude command of the self-synchronous voltage source are passed through the three-phase voltage equation to generate a three-phase terminal voltage command of the self-synchronous voltage source.

[0126] It should be noted that when obtaining the terminal voltage amplitude instruction of the self-synchronous voltage source and the vector angle of the self-synchronous voltage source After that, the traditional VSG (Virtual Synchronous Generator) will be directly combined with and The voltage control signal is obtained and used as the modulation wave of PWM modulation. Figure 2 The control principle diagram of the present invention is as follows. The present invention determines the angular frequency of the self-synchronous voltage source and its three-phase terminal voltage command through power angle control, then uses balanced current control to obtain the current command signal. Finally, a balanced current control module integrated with a PIR (Proportional-Integral-Resonant Controller) controller is used to output the PWM control signal of the switching tube.

[0127] In the embodiment of the present invention, the three-phase terminal voltage command refers to a three-phase voltage reference signal generated based on the terminal voltage amplitude command and the vector angle in the self-synchronous voltage source control and used to guide the inverter output.

[0128] Vector angle based on self-synchronous voltage source and terminal voltage amplitude command , the three-phase terminal voltage instructions of the self-synchronous voltage source are obtained by the following equation:

[0129]

[0130] Where, 、 、 is the three-phase terminal voltage instruction; is the terminal voltage amplitude instruction, is the vector angle.

[0131] S27. Determine a current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operation data.

[0132] In the embodiment of the present invention, the current command signal refers to a target current reference value generated by a balanced current control algorithm based on the three-phase terminal voltage commands and the actual voltage at the grid connection point in the control of the grid-connected inverter.

[0133] Grid-connected voltage refers to the actual three-phase voltage at the grid-connected point, which directly reflects the real-time status of the power grid (such as voltage amplitude, frequency, three-phase balance, harmonic content, etc.).

[0134] By three-phase terminal voltage command 、 、 and the collected grid voltage 、 and , the current command signal is obtained through balanced current control:

[0135]

[0136] Where, 、 、 is the three-phase current command signal; is a virtual resistor; In the grid-connected inverter control, the virtual impedance parameter is used. and They represent the equivalent resistance and inductance characteristics of the grid connection loop respectively; 、 、 is the three-phase terminal voltage instruction; 、 and is the grid voltage; s is the Laplace operator.

[0137] By establishing a vector relationship between the power loop output voltage and the electrical quantities at the grid connection point, the current command for self-synchronous control is derived. This method not only improves the system's current control capability, but also significantly enhances the quality of current control under large grid disturbances by optimizing and adjusting the virtual impedance parameters, improving the dynamic performance of the grid-connected system.

[0138] Step 103 : The current reference value of the current command signal, the active component and the reactive component of the filter inductor current are sequentially passed through a proportional-integral resonant controller and coordinate inverse transformation to generate a three-phase modulation signal.

[0139] In the embodiments of the present invention, the proportional-integral resonant controller refers to a composite control algorithm that combines the proportional (P), integral (I), and resonant (R) links, wherein the proportional link accelerates the dynamic response, the integral link eliminates the steady-state error, and the resonant link provides high gain for specific harmonic frequencies (such as the 2nd and 3rd harmonics) to accurately suppress harmonics. It is suitable for zero-error tracking of the fundamental current and effective suppression of harmonic currents in grid-connected inverters.

[0140] Inverse coordinate transformation refers to the process of converting the DC quantity in the rotating coordinate system (dq) into the AC quantity in the three-phase stationary coordinate system (abc) (i.e., dq-abc transformation). It is the inverse operation of coordinate transformation and is used to restore the DC quantity processed by the digital controller into a three-phase AC signal to adapt to the three-phase output characteristics of the inverter.

[0141] The three-phase modulation signal refers to the three-phase AC reference signal generated after coordinate inverse transformation and used to drive pulse width modulation (PWM). Its amplitude and phase determine the on / off time of the inverter switch tube, and ultimately control the inverter output current consistent with the current command.

[0142] First, the current error is calculated by subtracting the current reference value of the current command signal in the dq coordinate system from the active component of the filter inductor current. This error signal is then fed into the PIR controller. The proportional phase quickly responds to the error, the integral phase eliminates the steady-state error of the fundamental current, and the resonant phase selectively suppresses specific harmonics (such as the second harmonic generated by grid imbalance). The resulting output is a voltage control variable in the dq coordinate system. This voltage control variable is then converted into a three-phase AC quantity through an inverse coordinate transformation (dq → abc), generating a three-phase modulation signal. Finally, the three-phase modulation signal drives the PWM module to generate trigger pulses for the switching transistors, controlling the on and off of the inverter's power devices. This ensures that the filter inductor current accurately tracks the current command signal, achieving high-quality grid-connected current output. This entire process, leveraging the PIR controller's harmonic suppression capabilities and adaptability to coordinate transformation, ensures the inverter can output low-distortion current even under grid disturbances, improving grid-connected performance.

[0143] Furthermore, step 103 includes the following sub-steps:

[0144] S31 . Perform coordinate transformation on the current command signal to generate a current reference value; wherein the current reference value includes a first current reference value and a second current reference value.

[0145] In the embodiment of the present invention, the current reference value refers to a preset target value that the inverter output current is expected to reach in the current loop control of the grid-connected inverter, and is a benchmark for current control.

[0146] The first current reference value refers to the current reference value .

[0147] The second current reference value refers to the current reference value .

[0148] The current command signal 、 and go through Transformation Current reference value of the coordinate system and .

[0149] S32: Calculate a first difference between the first current reference value and the active component of the filter inductor current.

[0150] In the embodiment of the present invention, the first difference refers to the current reference value (ie the first current reference value) and the filter inductor current Active component The value obtained by taking the difference between them.

[0151] according to Figure 2Control principle diagram, current reference value and filter inductor current Active component Make the difference and get the first difference.

[0152] S33: Calculate a second difference between the second current reference value and the reactive component of the filter inductor current.

[0153] In the embodiment of the present invention, the second difference refers to the current reference value (i.e. the second current reference value) and the filter inductor current The reactive component The value obtained by taking the difference between them.

[0154] according to Figure 2 Control principle diagram, current reference value and filter inductor current The reactive component Subtract and get the second difference.

[0155] S34 , inputting the first difference and the second difference into a proportional-integral resonant controller respectively to generate a pulse width modulation control signal.

[0156] In the embodiment of the present invention, the pulse width modulation control signal refers to

[0157] according to Figure 2 The control principle diagram shows that the current command signal 、 and go through Transformation Current reference value of the coordinate system and , combined with the collected filter inductor current of Quantity and , the PWM (pulse width modulation) control signal is obtained through current loop control and :

[0158]

[0159] Where, is the PIR controller proportional coefficient, is the integral coefficient of the PIR controller, is the resonance coefficient of the PIR controller, is the quality factor of the current loop PIR controller; s is the Laplace operator; and is the current reference value; and is the filter inductor current of Quantity; is the rated angular frequency. It is designed to filter out the DC component in the system, and the quality factor The main considerations are the gain and stability of the PIR controller.

[0160] S35 , performing inverse coordinate transformation on the pulse width modulation control signal to generate a three-phase modulation signal.

[0161] In the embodiment of the present invention, the three-phase modulation signal refers to a three-phase AC reference signal used to drive a pulse width modulation (PWM) module in a grid-connected inverter.

[0162] The pulse width modulation control signal and go through The inverse transformation obtains the three-phase modulation signal of the pulse width modulation of the inverter 、 and .

[0163] Step 104 : Calculate the filter inductance value according to the ripple coefficient, the ripple maximum value, and the switching period of the three-phase modulation signal, and determine the filter capacitance value based on the filter inductance value and the resonant frequency.

[0164] It should be noted that the main circuit of the new energy grid-connected system and the interaction between the various control loops are very close, and any parameter change may cause the system to become unstable. Therefore, it is necessary to design the parameters of the LC filter. The structure of the grid-connected inverter is as follows: Figure 3 As shown in the figure. is the DC side voltage; is the DC side filter capacitor; For filter inductance, For filter capacitors, is the passive damping resistor; are the grid-side equivalent inductance and resistance respectively; 、 、 is the three-phase voltage on the grid side; PCC is the grid connection point.

[0165] In the embodiments of the present invention, the ripple coefficient refers to a parameter indicating the relative size of the ripple component in the current or voltage, and is usually expressed as the ratio of the ripple amplitude to the fundamental amplitude. It reflects the degree of interference of the ripple on the signal. The smaller the value, the better the ripple suppression effect.

[0166] The maximum ripple value refers to the maximum ripple current / voltage amplitude that appears in the filter inductor or capacitor during PWM modulation. It is a key constraint to consider when designing the filter and must be controlled within the device's allowable range (such as the rated current ripple of the inductor).

[0167] The switching cycle refers to the on-off period of the inverter power switch tube, which is inversely proportional to the switching frequency and determines the frequency characteristics of the PWM ripple.

[0168] The filter inductance value refers to the inductance of the inductor in the LC filter. Its main function is to suppress the high-frequency current ripple generated by PWM modulation. Its value directly affects the ripple suppression effect and the dynamic response speed of the system.

[0169] The resonant frequency refers to the frequency at which the circuit resonates under specific conditions when the inductive reactance of the inductor and the capacitive reactance of the capacitor are equal in magnitude and opposite in phase. At this time, the total impedance of the circuit exhibits a purely resistive characteristic.

[0170] The filter capacitor value refers to the capacitance of the capacitor in the LC filter. It forms a low-pass filter network with the filter inductor to further smooth the voltage ripple. Its value and the inductance value jointly determine the resonant frequency of the filter.

[0171] First, based on the ripple coefficient of the three-phase modulated signal (reflecting the ratio of ripple to fundamental, used to limit the degree of ripple interference), the maximum ripple value (the maximum current pulsation caused by PWM switching, which must be controlled within the device's allowable range), and the switching period (the on-off period of the inverter's power transistor, which determines the ripple frequency characteristics), the filter inductor value is determined using a formula (such as a calculation formula derived from the principle of inductor ripple suppression) to ensure that the inductor can effectively attenuate high-frequency ripple and ensure that the output current ripple meets grid requirements. Then, based on the determined filter inductor value and resonant frequency (which must avoid the grid fundamental, switching frequency, and control bandwidth to prevent resonance from amplifying ripple or causing system oscillation), the filter capacitor value is inferred using the LC resonant frequency formula. This ensures that the low-pass filter network formed by the LC filter can further smooth voltage ripple and avoid resonance risks through parameter matching between the inductor and capacitor, ultimately ensuring the waveform quality of the inverter output current and stable system operation.

[0172] Furthermore, step 104 includes the following sub-steps:

[0173] S41. Calculate the filter inductance value according to the ripple coefficient, the maximum ripple value, and the switching period of the three-phase modulation signal.

[0174] In the embodiment of the present invention, the calculation formula for the value of the filter inductance is:

[0175] ;

[0176] Where, is the PWM modulation ripple coefficient; for The maximum value of the ripple; To self-synchronize and control the switching cycle of the IGBT tube; is the DC side voltage.

[0177] S42. Establish a current loop open-loop transfer function of the self-synchronous voltage source; wherein the current loop open-loop transfer function includes a total delay time and a current transfer function.

[0178] In the embodiment of the present invention, the current loop open-loop transfer function , which describes the mathematical relationship between the input signal (e.g., current command) and the output signal (e.g., actual current) of a current loop control system in an open-loop state. It integrates the transfer characteristics of each link within the current loop (e.g., controller, power device, sensor), reflecting the system's dynamic response to the input signal, such as amplification and phase lag. It is a core tool for analyzing current loop stability (e.g., phase margin and gain margin) and designing controller parameters.

[0179] Total delay time , refers to the total time delay from signal acquisition to execution in current loop control. This delay primarily includes signal sampling delay (Analog to Digital (Analog to Digital) conversion time), digital controller operation delay, and PWM modulation delay. This total delay causes phase lag in the control signal, affecting system stability. It must be quantified in the transfer function and is a key parameter in designing control loop bandwidth and phase compensation.

[0180] Current transfer function , refers to a complex frequency domain function that describes the relationship between the input and output current of a specific link in the current loop (such as the inverter main circuit and filter). For example, the transfer function from the inverter output voltage to the output current reflects the amplification, filtering or phase modulation characteristics of the current in this link, and is the basic component for constructing the open-loop transfer function of the current loop.

[0181] Current loop open-loop transfer function of self-synchronous voltage source control for:

[0182] ;

[0183] Where, is the current loop transfer function; is the control coefficient; e is the natural index; Transfer function for converting inverter output voltage to current; is the total delay time. The calculation formula is:

[0184] ;

[0185] Where, is the delay coefficient, It is the self-synchronous control current sampling time.

[0186] S43 : Determine the phase of the current open-loop transfer function based on the phase angle of the current open-loop transfer function, the phase angle of the current transfer function, the total delay time, and the angular frequency.

[0187] In the embodiment of the present invention, the phase angle refers to a specific value of the phase, which is a quantitative expression of the phase.

[0188] Phase refers to the physical quantity that describes the state (position, trend) of fluctuation at a certain moment in periodic fluctuations (such as sine waves).

[0189] Current loop open-loop transfer function Phase The expression is:

[0190] ;

[0191] Where, is the current loop transfer function The phase angle of is the current transfer function The phase angle of is the delay coefficient, It is the self-synchronous control current sampling time.

[0192] S44. Evaluate the phase of the current loop open-loop transfer function to generate a system phase stability margin.

[0193] In an embodiment of the present invention, the system phase stability margin refers to a key indicator for measuring the stability of a closed-loop control system, and is defined as the difference between the phase angle of the system's open-loop transfer function at the gain crossover frequency (i.e., the frequency when the open-loop gain is 1) and -180°.

[0194] The system phase stability margin is evaluated through the phase expression of the current loop open-loop transfer function.

[0195] S45. Determine the resonant frequency stability domain range using the total delay time, the phase angle of the current loop open-loop transfer function, and the system phase stability margin.

[0196] In the embodiment of the present invention, the resonant frequency stability domain range refers to the range of the resonant frequency allowed in a control system including a resonant link (such as an LC filter circuit, a resonant controller, etc.) that can ensure stable operation of the system.

[0197] Total delay time , system phase stability margin And the current loop open-loop transfer function Phase , the stable range of the resonant frequency is:

[0198] ;

[0199] Where n is a natural number; is pi; is the resonant frequency of the LC filter; is the system sampling frequency; is the system phase stability margin; is the current loop transfer function The phase angle of is the delay coefficient.

[0200] S46. Determine a value range of the blocking frequency based on the stable domain range of the resonant frequency.

[0201] In the embodiment of the present invention, the blocking frequency , refers to a specific frequency or frequency range that needs to be significantly attenuated or "blocked" (suppressed) in a filtering circuit, control system or signal processing.

[0202] If the control bandwidth is , take and The natural number n corresponding to the nearest stable resonance frequency range is set as the stable resonance frequency range selection coefficient , resonant frequency stability range and control bandwidth The smallest difference is considered the closest.

[0203] ;

[0204] Where n is a natural number; is pi; is the resonant frequency of the LC filter; is the system sampling frequency; is the system phase stability margin; is the current loop transfer function The phase angle of is the delay coefficient.

[0205] S47. Perform a weighted geometric operation on the value range of the blocking frequency and the resonant frequency to determine the resonant frequency.

[0206] In the embodiment of the present invention, the resonant frequency refers to the frequency at which the system generates resonance when the frequency of the external force (or excitation) is equal to the natural frequency of the system (or object).

[0207] Calculate the resonant frequency of LC filter using weighted geometric mathematical method Size:

[0208] ;

[0209] Where k1 is the control loop bandwidth coefficient, k2 is the switching frequency coefficient, where K=k1+k2, and .

[0210] like , the resonant frequency can be calculated similarly The value of is:

[0211] ;

[0212] Pick .

[0213] S48. Determine the filter capacitance value based on the filter inductance value and the resonant frequency.

[0214] In the embodiment of the present invention, the filter inductance L and the resonant frequency , the filter capacitance value C can be obtained.

[0215] Furthermore, step S48 includes the following sub-steps:

[0216] S481. Calculate the filter capacitance value using the filter inductance value and the resonant frequency. The calculation formula for the filter capacitance value is:

[0217] ;

[0218] Where, L represents the filter inductance value, Indicates the resonant frequency.

[0219] In the embodiment of the present invention, the resonant frequency and the filter inductance value obtained in step S41 The filter capacitor C can be obtained by solving the simultaneous equations:

[0220] ;

[0221] Where, L represents the filter inductance value, Indicates the resonant frequency.

[0222] The filter inductance value L and filter capacitance value C of the LC filter are obtained through parameter design.

[0223] Step 105 : Control the self-synchronous voltage source according to the value range of the filter inductance and the filter capacitance.

[0224] In the embodiment of the present invention, the self-synchronous voltage source is further controlled by adjusting the value range of the filter inductance and the filter capacitance.

[0225] This approach combines a proportional-integral-resonant (PIR) controller with impedance characteristic adjustment to propose a dynamic balanced current control mechanism. Unlike traditional VSGs, which rely solely on a single current tracking mode (Proportional-Integral (PI)), this approach establishes a phase-amplitude relationship model between the voltage vector output by the power loop and the voltage and current at the grid connection point. This generates a dynamic current reference value for self-synchronous control and utilizes a resonant controller to actively suppress specific harmonics (such as the 2nd and 4th order grid unbalance harmonics).

[0226] By adjusting the equivalent impedance (including both resistance and reactance components) between the inverter's internal potential and the grid voltage, dynamic compensation for grid current imbalance is achieved. Unlike traditional VSG designs with fixed impedance parameters, this solution uses the impedance adjustment as the feedforward input to the PIR controller, forming an impedance-current dual-degree-of-freedom control structure.

[0227] The core advantage of this invention lies in its collaborative optimization of the PIR controller and the current reference value generation mechanism, which solves the difficult problem of harmonic suppression and dynamic tracking under unbalanced grid conditions. Traditional methods using PI controllers, which can only track the fundamental component, lack a targeted compensation mechanism for the negative-sequence and harmonic currents caused by grid voltage imbalance, resulting in severe grid-connected current waveform distortion and delayed dynamic response. This invention, through the resonant adjustment unit of the PIR controller, embeds high-gain compensation characteristics for specific harmonic frequencies (such as the second harmonic corresponding to the negative-sequence component) into the control loop, directly suppressing the generation and amplification of harmonic currents and significantly improving the current waveform quality.

[0228] See also Figure 4 , Figure 4 This is a structural block diagram of a balanced current controlled self-synchronous voltage source control system provided in the second embodiment of the present invention.

[0229] The present invention provides a balanced current controlled self-synchronous voltage source control system, comprising:

[0230] An acquisition module 401 is used to acquire and pre-process the operating data of the grid-connected inverter to generate active and reactive components corresponding to the filter capacitor voltage, filter inductor current, and filter capacitor current, respectively;

[0231] a current command signal module 402 for determining a three-phase terminal voltage command of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, and determining a current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operating data;

[0232] The conversion module 403 is used to sequentially pass the current reference value of the current command signal, the active component and the reactive component of the filter inductor current through a proportional-integral resonant controller and coordinate inverse transformation to generate a three-phase modulation signal;

[0233] A calculation module 404 is configured to calculate a filter inductance value based on a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulation signal, and determine a filter capacitance value based on the filter inductance value and the resonant frequency;

[0234] The control module 405 is used to control the self-synchronous voltage source according to the value range of the filter inductance value and the filter capacitance value.

[0235] Furthermore, the acquisition module 401 includes:

[0236] The acquisition submodule is used to collect the operating data of the grid-connected inverter; wherein the operating data includes the filter capacitor voltage, the filter inductor current, the grid voltage and the bridge arm inductor current;

[0237] The transformation submodule is used to perform coordinate transformation on the filter capacitor voltage and the filter inductor current to generate active components and reactive components corresponding to the filter capacitor voltage and the filter inductor current respectively;

[0238] The processing submodule is used to discretize the active component and reactive component corresponding to the filter capacitor voltage and filter inductor current respectively, and determine the active component and reactive component corresponding to the filter capacitor current based on the discretized filter capacitor voltage and filter inductor current.

[0239] Furthermore, the current command signal module 402 includes:

[0240] An output current submodule, configured to determine the active and reactive components of the output current based on the active and reactive components corresponding to the filter inductor current and the filter capacitor current, respectively;

[0241] The power calculation submodule is used to calculate the average active power and average reactive power based on the active component and reactive component corresponding to the filter capacitor voltage and output current, as well as the harmonic filtering parameters;

[0242] The angular frequency submodule is used to generate the angular frequency of the self-synchronous voltage source by applying the average active power and the active power command corresponding to the grid-connected inverter to the active frequency control equation;

[0243] A vector angle submodule, for determining a vector angle of the self-synchronous voltage source based on an angular frequency and a Laplace operator of the self-synchronous voltage source;

[0244] The terminal voltage amplitude instruction submodule is used to generate the terminal voltage amplitude instruction of the self-synchronous voltage source by using the reactive voltage control equation to convert the average reactive power and the reactive power instruction corresponding to the grid-connected inverter;

[0245] The three-phase terminal voltage instruction submodule is used to generate the three-phase terminal voltage instruction of the self-synchronous voltage source by passing the vector angle and terminal voltage amplitude instruction of the self-synchronous voltage source through the three-phase voltage equation;

[0246] The current command signal submodule is used to determine the current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operation data.

[0247] Furthermore, the transformation module 403 includes:

[0248] A coordinate transformation submodule is used to perform coordinate transformation on the current command signal to generate a current reference value; wherein the current reference value includes a first current reference value and a second current reference value;

[0249] a first difference submodule, configured to calculate a first difference between a first current reference value and an active component of a filter inductor current;

[0250] a second difference submodule, configured to calculate a second difference between a second current reference value and a reactive component of the filter inductor current;

[0251] an input submodule, configured to input the first difference and the second difference into a proportional-integral resonant controller respectively to generate a pulse width modulation control signal;

[0252] The coordinate inverse transformation submodule is used to perform coordinate inverse transformation on the pulse width modulation control signal to generate a three-phase modulation signal.

[0253] Furthermore, the calculation module 404 includes:

[0254] A calculation submodule, used to calculate the filter inductance value according to the ripple coefficient, ripple maximum value and switching period of the three-phase modulation signal;

[0255] Establishing a submodule for establishing a current loop open-loop transfer function of a self-synchronous voltage source; wherein the current loop open-loop transfer function includes a total delay time and a current transfer function;

[0256] a phase submodule, for determining the phase of the current loop open-loop transfer function based on the phase angle of the current loop open-loop transfer function, the phase angle of the current transfer function, the total delay time, and the angular frequency;

[0257] An evaluation submodule is used to evaluate the phase of the current loop open-loop transfer function and generate a system phase stability margin;

[0258] The range submodule is used to determine the resonant frequency stability domain range using the total delay time, the phase angle of the current loop open-loop transfer function, and the system phase stability margin;

[0259] A value submodule, used to determine the value range of the blocking frequency based on the stable domain range of the resonant frequency;

[0260] An operation submodule, used for performing weighted geometric operations on the value range of the blocking frequency and the resonant frequency to determine the resonant frequency;

[0261] The filter capacitance value submodule is used to determine the filter capacitance value based on the filter inductance value and the resonant frequency.

[0262] Furthermore, the filter capacitance value submodule includes:

[0263] The filter capacitance calculation submodule is used to calculate the filter capacitance value using the filter inductance value and the resonant frequency. The filter capacitance value is calculated using the following formula:

[0264] ;

[0265] Where, L represents the filter inductance value, Indicates the resonant frequency.

[0266] An embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the method for controlling a self-synchronous voltage source with balanced current control according to any embodiment of the present invention is implemented.

[0267] An embodiment of the present invention provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer executes a self-synchronous voltage source control method for balanced current control as described in any embodiment of the present invention.

[0268] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0269] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0270] The units described as separate components may or may not be physically separate, and 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 these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0271] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0272] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or 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 for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0273] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-synchronous voltage source control method for balanced current control, characterized in that: include: Obtaining and preprocessing the operating data of the grid-connected inverter to generate the active and reactive components corresponding to the filter capacitor voltage, filter inductor current, and filter capacitor current, respectively; Determining a three-phase terminal voltage command of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, and determining a current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operating data; The current reference value of the current command signal, the active component and the reactive component of the filter inductor current are sequentially passed through a proportional-integral resonant controller and an inverse coordinate transformation to generate a three-phase modulation signal; Calculating a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulated signal, and determining a filter capacitance value based on the filter inductance value and a resonant frequency; The self-synchronous voltage source is controlled according to the value range of the filter inductance and the filter capacitance.

2. The method for controlling a self-synchronous voltage source with balanced current control according to claim 1, wherein: The obtaining and preprocessing of the operation data of the grid-connected inverter to generate active components and reactive components corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, includes: Collecting operating data of the grid-connected inverter; wherein the operating data includes filter capacitor voltage, filter inductor current and grid voltage; Performing coordinate transformation on the filter capacitor voltage and the filter inductor current to generate active components and reactive components corresponding to the filter capacitor voltage and the filter inductor current, respectively; The active component and reactive component corresponding to the filter capacitor voltage and the filter inductor current are discretized, and the active component and reactive component corresponding to the filter capacitor current are determined based on the discretized filter capacitor voltage and filter inductor current.

3. The self-synchronous voltage source control method for balanced current control according to claim 2, characterized in that: The determining of the three-phase terminal voltage instructions of the self-synchronous voltage source based on the active component and reactive component respectively corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, and determining the current instruction signal based on the three-phase terminal voltage instructions and the grid-connected voltage corresponding to the operation data, includes: Determining the active component and reactive component of the output current based on the active component and reactive component corresponding to the filter inductor current and the filter capacitor current, respectively; Calculating average active power and average reactive power based on the active component and reactive component corresponding to the filter capacitor voltage and the output current, respectively, and harmonic filtering parameters; The average active power and the active power command corresponding to the grid-connected inverter are applied to an active frequency control equation to generate an angular frequency of the self-synchronous voltage source; determining a vector angle of the self-synchronous voltage source based on the angular frequency and the Laplace operator of the self-synchronous voltage source; The average reactive power and the reactive power command corresponding to the grid-connected inverter are applied to a reactive voltage control equation to generate a terminal voltage amplitude command of a self-synchronous voltage source; The vector angle and terminal voltage amplitude command of the self-synchronous voltage source are passed through the three-phase voltage equation to generate the three-phase terminal voltage command of the self-synchronous voltage source; A current command signal is determined based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operation data.

4. The method for controlling a self-synchronous voltage source with balanced current control according to claim 3, wherein: The current reference value of the current command signal, the active component and the reactive component of the filter inductor current are sequentially passed through a proportional-integral resonant controller and coordinate inverse transformation to generate a three-phase modulation signal, including: Performing coordinate transformation on the current command signal to generate a current reference value; wherein the current reference value includes a first current reference value and a second current reference value; calculating a first difference between the first current reference value and an active component of the filter inductor current; calculating a second difference between the second current reference value and a reactive component of the filter inductor current; inputting the first difference and the second difference into a proportional-integral resonant controller respectively to generate a pulse width modulation control signal; The pulse width modulation control signal is subjected to coordinate inverse transformation to generate a three-phase modulation signal.

5. The method for controlling a self-synchronous voltage source with balanced current control according to claim 3, wherein: The calculating of the filter inductance value according to the ripple coefficient, the ripple maximum value and the switching period of the three-phase modulation signal, and determining the filter capacitance value based on the filter inductance value and the resonant frequency includes: Calculating a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulation signal; Establishing a current loop open-loop transfer function of the self-synchronous voltage source; wherein the current loop open-loop transfer function includes a total delay time and a current transfer function; determining a phase of the current open-loop transfer function based on the phase angle of the current open-loop transfer function, the phase angle of the current transfer function, the total delay time, and the angular frequency; evaluating the phase of the current loop open-loop transfer function to generate a system phase stability margin; Determining a resonant frequency stability domain range using the total delay time, the phase angle of the current loop open-loop transfer function, and the system phase stability margin; Based on the stable domain of the resonant frequency, determine the value range of the blocking frequency; Performing a weighted geometric operation on the range of the blocking frequency and the resonant frequency to determine the resonant frequency; A filter capacitance value is determined based on the filter inductance value and the resonant frequency.

6. The method for controlling a self-synchronous voltage source with balanced current control according to claim 5, wherein: The determining of the filter capacitance value based on the filter inductance value and the resonant frequency includes: The filter capacitance value is calculated using the filter inductance value and the resonant frequency; wherein the calculation formula of the filter capacitance value is: ； Where, L represents the filter inductance value, Indicates the resonant frequency.

7. A self-synchronous voltage source control system with balanced current control, characterized in that: include: An acquisition module is used to acquire and pre-process the operating data of the grid-connected inverter to generate active and reactive components corresponding to the filter capacitor voltage, filter inductor current, and filter capacitor current, respectively; a current command signal module, configured to determine a three-phase terminal voltage command of the self-synchronous voltage source based on the active component and reactive component corresponding to the filter capacitor voltage, the filter inductor current, and the filter capacitor current, respectively, and to determine a current command signal based on the three-phase terminal voltage command and the grid-connected voltage corresponding to the operating data; a conversion module, configured to sequentially pass the current reference value of the current command signal, the active component and the reactive component of the filter inductor current through a proportional-integral resonant controller and coordinate inverse transformation to generate a three-phase modulation signal; a calculation module, configured to calculate a filter inductance value according to a ripple coefficient, a ripple maximum value, and a switching period of the three-phase modulated signal, and determine a filter capacitance value based on the filter inductance value and a resonant frequency; A control module is used to control the self-synchronous voltage source according to the value range of the filter inductance value and the filter capacitance value.

8. The balanced current controlled self-synchronous voltage source control system according to claim 7, characterized in that: The acquisition module includes: The acquisition submodule is used to collect the operating data of the grid-connected inverter; wherein the operating data includes the filter capacitor voltage, the filter inductor current, the grid voltage and the bridge arm inductor current; a conversion submodule, configured to perform coordinate transformation on the filter capacitor voltage and the filter inductor current to generate active components and reactive components corresponding to the filter capacitor voltage and the filter inductor current, respectively; The processing submodule is used to discretize the active component and reactive component corresponding to the filter capacitor voltage and the filter inductor current, and determine the active component and reactive component corresponding to the filter capacitor current based on the discretized filter capacitor voltage and filter inductor current.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the self-synchronous voltage source control method for balanced current control according to any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the balanced current controlled self-synchronous voltage source control method according to any one of claims 1 to 6.

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