Method and system for controlling power balance and voltage balance of three-phase inverter

Abstract

The invention provides a control method and system for power balance and voltage balance of a three-phase inverter, and relates to the technical field of power electronic control, and the method comprises the steps: employing a double second-order generalized integrator, and separating positive and negative sequence components of voltage and current; calculating to obtain a negative sequence voltage amplitude according to the separated voltage negative sequence component, judging whether the negative sequence voltage amplitude exceeds a set value or not, if yes, inputting negative sequence voltage outer loop control, generating a negative sequence current instruction, inputting negative sequence current inner loop control, obtaining a final negative sequence current instruction according to the negative sequence current instruction, and driving an inner loop current controller to output corresponding current; according to a preset rule, adaptively determining a capacitance value of the virtual capacitor; and the positive sequence voltage is embedded into the virtual resistor and the virtual inductor for decoupling calculation, a final positive sequence current instruction is obtained, and an inner loop current controller is driven to output corresponding current based on the final positive sequence current instruction. According to the invention, the accuracy and reliability of power distribution of the three-phase inverter parallel system can be improved.

Description

Technical Field

[0001] This application relates to the field of power electronic control technology, and in particular to a control method and system for power balancing and voltage balancing of a three-phase inverter. Background Technology

[0002] Currently, for three-phase inverter systems with multiple devices connected in parallel, such as energy storage power stations, microgrids, and grid-type virtual synchronous generators (VSGs), the industry widely adopts droop control strategies (Pf, QV control) for power distribution. This type of control strategy relies on the positive sequence component of the grid voltage, and has the following drawbacks under grid voltage imbalance conditions: 1. The introduction of the negative sequence component of the voltage leads to second harmonic pulsation components in active and reactive power, which significantly reduces the power detection and regulation accuracy of traditional droop control, causing power distribution errors among the parallel devices; 2. The negative sequence component of the output voltage of each device will form circulating current, threatening the stable operation of the system; 3. Power distribution among devices relies on communication, but communication delays and interruptions will affect the stable operation of the system, resulting in low reliability.

[0003] Therefore, how to improve the accuracy and reliability of power distribution in a three-phase inverter parallel system is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a control method for power balancing and voltage balancing in a three-phase inverter, which can improve the accuracy and reliability of power distribution in a parallel three-phase inverter system. This application also provides a control system for power balancing and voltage balancing in a three-phase inverter, achieving the same technical effect.

[0005] The first objective of this application is to provide a control method for power balancing and voltage balancing of a three-phase inverter.

[0006] The aforementioned objective of this application is achieved through the following technical solution: A control method for power balancing and voltage balance of a three-phase inverter, comprising: A dual second-order generalized integrator is used to separate the positive and negative sequence components of voltage and current; Based on the separated negative sequence voltage component, the negative sequence voltage amplitude is calculated. It is then determined whether the negative sequence voltage amplitude exceeds a set value. If so, then: The outer loop control of negative sequence voltage is activated to generate a negative sequence current command, and the inner loop control of negative sequence current is activated. Based on the negative sequence current command, the final negative sequence current command is obtained, and the inner loop current controller is driven to output the corresponding current based on the final negative sequence current command. The capacitance value of the virtual capacitor is adaptively determined according to preset rules; The positive sequence voltage is embedded in virtual resistors and virtual inductors for decoupling calculation to obtain the final positive sequence current command. Based on the final positive sequence current command, the inner loop current controller is driven to output the corresponding current.

[0007] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, The positive-sequence transfer function of the dual second-order generalized integrator is: ; The negative-order transfer function of the dual second-order generalized integrator is: ; In the formula, This represents the orthogonal transfer function. This represents the negative-order transfer function. Indicates the damping coefficient. Indicates the resonant frequency. This represents the Laplace operator.

[0008] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, the use of dual second-order generalized integrators to separate the positive and negative sequence components of voltage and current includes: By employing a dual second-order generalized integrator, the positive and negative sequence components of voltage and current are separated to obtain the negative sequence component of voltage, the positive sequence component of voltage, the negative sequence component of current, and the positive sequence component of current in the αβ coordinate system.

[0009] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, The expression for the negative sequence component of the voltage is: ; The expression for the positive sequence component of the voltage is: ; The expression for the positive sequence component of the current is: ; The expression for the negative sequence component of the current is: ; In the formula, This represents the voltage components in the α coordinate system. This represents the voltage components in the β coordinate system; This represents the components of the negative sequence voltage in the α coordinate system. This represents the negative sequence voltage component in the β coordinate system. This represents the positive-sequence voltage component in the α coordinate system. This represents the positive-sequence voltage component in the β coordinate system. This represents the components of the current in the α coordinate system. This represents the components of the current in the β coordinate system. This represents the positive sequence current component in the α coordinate system. This represents the positive sequence current component in the β coordinate system. This represents the component of the negative sequence current in the α coordinate system. This represents the component of the negative sequence current in the β coordinate system.

[0010] Preferably, in the control method for power balancing and voltage balance of the three-phase inverter, the formula for calculating the negative sequence voltage amplitude is: ; In the formula, This represents the magnitude of the negative sequence voltage.

[0011] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, the step of engaging the negative-sequence voltage outer loop control and generating a negative-sequence current command includes: Obtain the negative sequence component of the three-phase inverter AC voltage on the DQ axis, and calculate the deviation of the negative sequence D-axis voltage and the deviation of the negative sequence Q-axis voltage. The specific calculation formula is as follows: ; ; In the formula, This indicates the deviation of the negative sequence D-axis voltage. This represents the negative sequence component of the AC voltage of the three-phase inverter on the D-axis. This indicates the deviation of the negative-sequence Q-axis voltage. This represents the negative sequence component of the AC voltage of a three-phase inverter on the Q-axis. Based on the deviations of the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage, decoupling calculations are performed on the virtual resistance and virtual inductance along the D and Q axes to obtain the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage. The specific calculation formulas are as follows:

[0012] In the formula, This represents the negative sequence D-axis voltage. Indicates virtual resistance. Represents pi (π). Represents virtual inductance. This represents the negative-sequence Q-axis voltage; Based on the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage, the decoupling of the negative-sequence voltage in the current loop is calibrated to obtain the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration. The specific calculation formula is as follows: ; ; In the formula, This indicates the negative sequence D-axis voltage calibration. This indicates the negative-sequence Q-axis voltage calibration; Based on the negative sequence D-axis voltage calibration and the negative sequence Q-axis voltage calibration, the negative sequence current command is obtained.

[0013] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, obtaining the negative-sequence current command based on the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration includes: Based on the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration, a negative-sequence current command is generated through a proportional relationship, wherein the negative-sequence current command includes... and , This indicates the command for negative sequence current on the D-axis. This command indicates the negative sequence current in the Q-axis region.

[0014] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, the step of engaging the negative sequence current inner loop control and obtaining the final negative sequence current command based on the negative sequence current command includes: The negative sequence components of the D-axis current and Q-axis current are obtained from the outer voltage loop, and the calculation formula is as follows: ; In the formula, This represents the negative sequence component of the D-axis current. This represents the negative sequence component of the Q-axis current. Represents virtual capacitance. This represents the negative sequence component of the D-axis voltage. This represents the negative sequence component of the Q-axis voltage; Based on the negative sequence components of the D-axis and Q-axis currents, the virtual capacitor is decoupled along the D and Q axes in the two-phase rotating coordinate system current to obtain the D-axis virtual capacitor compensation current and the Q-axis virtual capacitor compensation current. The calculation formulas are as follows: ; In the formula, This represents the virtual capacitor compensation current along the D-axis. This indicates the Q-axis virtual capacitor compensation current; Based on the D-axis virtual capacitor compensation current, the Q-axis virtual capacitor compensation current, and the negative sequence current command, the final negative sequence current command is obtained, and the calculation formula is as follows: ; In the formula, This indicates a negative-sequence given D-axis current calibration. This indicates a negative-sequence given Q-axis current calibration, the final negative-sequence current command including... and .

[0015] Preferably, in the control method for power balancing and voltage balancing of the three-phase inverter, the step of embedding the positive-sequence voltage into virtual resistors and virtual inductors for decoupling calculation to obtain the final positive-sequence current command includes: Obtain the positive-sequence component of the three-phase inverter AC voltage on the DQ axis, and calculate the deviation of the positive-sequence D-axis voltage and the deviation of the positive-sequence Q-axis voltage. The specific calculation formula is as follows: ; ; In the formula, This indicates the deviation of the positive-sequence D-axis voltage. This represents the positive-sequence component of the AC voltage of the three-phase inverter on the D-axis. This indicates the deviation of the positive-sequence Q-axis voltage. This represents the positive sequence component of the AC voltage of a three-phase inverter on the Q-axis. Based on the deviations of the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, decoupling calculations are performed on the virtual resistance and virtual inductance along the D and Q axes to obtain the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage. The specific calculation formulas are as follows:

[0016] In the formula, This represents the positive-sequence D-axis voltage. This represents the positive-sequence Q-axis voltage; Based on the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, the decoupling of the positive-sequence voltage in the current loop is calibrated to obtain the positive-sequence D-axis voltage calibration and the positive-sequence Q-axis voltage calibration. The specific calculation formula is as follows: ; ; In the formula, This indicates the positive-sequence D-axis voltage calibration. This indicates the positive-sequence Q-axis voltage calibration; Based on the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, the decoupling of the positive-sequence given current is calibrated to obtain the final positive-sequence current command. The calculation formula is as follows: ; ; In the formula, This indicates that the D-axis current is calibrated in positive sequence. This indicates positive-sequence given Q-axis current calibration. Represents the D-axis current. Indicating the Q-axis current, the final positive sequence current command includes... and .

[0017] The second objective of this application is to provide a control system for power balancing and voltage balancing of a three-phase inverter.

[0018] The second objective of this application is achieved through the following technical solution: A power balancing and voltage balancing control system for a three-phase inverter, comprising: The separation unit is used to separate the positive and negative sequence components of voltage and current using a dual second-order generalized integrator. The judgment unit is used to calculate the negative sequence voltage amplitude based on the separated negative sequence voltage component and to determine whether the negative sequence voltage amplitude exceeds a set value. The first control unit is used to, when it is determined that the amplitude of the negative sequence voltage exceeds the set value, engage the outer loop control of the negative sequence voltage, generate a negative sequence current command, engage the inner loop control of the negative sequence current, obtain the final negative sequence current command according to the negative sequence current command, and drive the inner loop current controller to output the corresponding current based on the final negative sequence current command. The determining unit is used to adaptively determine the capacitance value of the virtual capacitor according to preset rules; The second control unit is used to embed the positive sequence voltage into virtual resistors and virtual inductors for decoupling calculation to obtain the final positive sequence current command, and drive the inner loop current controller to output the corresponding current based on the final positive sequence current command.

[0019] The beneficial effects of the above technical solution are as follows: (1) The outer loop of negative sequence voltage aims to suppress negative sequence voltage components and force the amplitude and phase of three-phase voltage to be symmetrical. It detects the negative sequence voltage deviation under unbalanced load in real time and outputs a negative sequence current reference command. The inner loop of negative sequence current quickly tracks the command and accurately compensates for the negative sequence current generated by load imbalance, thus solving the problem of three-phase voltage asymmetry from the source.

[0020] (2) The adaptive design of virtual capacitor can adjust the equivalent capacitance parameters in real time according to the dynamic disturbance intensity of the system. Combined with the negative sequence current embedding logic, the virtual capacitor can directly respond to the current change, thereby shortening the dynamic response time of the system and significantly improving the anti-interference stability.

[0021] (3) Virtual resistors and virtual inductors are separated into active and reactive power regulation channels through decoupling design to avoid cross interference; at the same time, the positive sequence current command is dynamically corrected by voltage deviation to ensure that the active and reactive power of multiple inverters are evenly distributed.

[0022] (4) Based on local signals and without relying on communication methods, reliability is significantly improved. Furthermore, power sharing can be achieved simply by upgrading the software algorithm, without the need to replace the hardware of the device itself, resulting in low engineering application costs.

[0023] In summary, the above technical solutions can improve the accuracy and reliability of power distribution in a three-phase inverter parallel system. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating a control method for power balancing and voltage balancing of a three-phase inverter provided in an embodiment of this application. Figure 2 This is a negative sequence voltage control loop diagram provided in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of a three-phase inverter power balancing and voltage balancing control system provided in the embodiments of this application. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In the embodiments provided in this application, it should be understood that the disclosed methods and systems can be implemented in other ways. The system embodiments described below are merely illustrative. For example, the division of units and modules is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or modules can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, and can be electrical, mechanical, or other forms.

[0028] In addition, each functional unit in the various embodiments of this application can be integrated into a single processor, or each unit can be a separate device, or two or more units can be integrated into a single device; each functional unit in the various embodiments of this application can be implemented in hardware or in the form of hardware plus software functional units.

[0029] Those skilled in the art will understand that all or part of the steps of the following method embodiments can be implemented by program instructions and related hardware. The aforementioned program instructions can be stored in a computer-readable storage medium. When the program instructions are executed, they perform the steps of the following method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0030] It should be understood that the use of terms such as "system," "device," "unit," and / or "module" in this application is merely one method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" or "several" means two or more, unless otherwise explicitly specified.

[0032] If a flowchart is used in this application, it is used to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0033] It should also be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the article or device that includes the aforementioned element.

[0034] The embodiments in this application are written in a progressive manner.

[0035] like Figure 1 As shown in the figure, this application provides a control method for power balancing and voltage balancing of a three-phase inverter, including: S101. A dual second-order generalized integrator is used to separate the positive and negative sequence components of voltage and current; Specifically, in S101, the Dual Second-Order Generalized Integrator (DSOGI) is an adaptive filtering technique for power system signal processing. Its core function is to separate the positive and negative sequence components in the three-phase voltage / current and suppress harmonics and DC disturbances. Through the positive and negative sequence transfer functions of the Dual Second-Order Generalized Integrator, the decoupling and separation of positive and negative sequence components under unbalanced grid conditions can be achieved.

[0036] In some embodiments, the positive-order transfer function of the dual second-order generalized integrator is: ; The negative-order transfer function of the dual second-order generalized integrator is: ; In the formula, This represents the orthogonal transfer function. This represents a negative-order transfer function. Indicates the damping coefficient. Indicates the resonant frequency. This represents the Laplace operator.

[0037] In some embodiments, one implementation of this step specifically includes: using a dual second-order generalized integrator to separate the positive and negative sequence components of voltage and current to obtain the negative sequence component of voltage, the positive sequence component of voltage, the negative sequence component of current, and the positive sequence component of current in the αβ coordinate system (also known as the two-phase stationary coordinate system or Clarke coordinate system).

[0038] The expression for the negative-sequence voltage component is as follows: ; The expression for the positive-sequence voltage component is: ; The expression for the positive sequence component of the current is: ; The expression for the negative sequence component of the current is: ; In the formula, This represents the voltage components in the α coordinate system. This represents the voltage components in the β coordinate system; This represents the components of the negative sequence voltage in the α coordinate system. This represents the negative sequence voltage component in the β coordinate system. This represents the positive-sequence voltage component in the α coordinate system. This represents the positive-sequence voltage component in the β coordinate system. This represents the components of the current in the α coordinate system. This represents the components of the current in the β coordinate system. This represents the positive sequence current component in the α coordinate system. This represents the positive sequence current component in the β coordinate system. This represents the component of the negative sequence current in the α coordinate system. This represents the component of the negative sequence current in the β coordinate system.

[0039] S102. Calculate the negative sequence voltage amplitude based on the separated negative sequence voltage component, and determine whether the negative sequence voltage amplitude exceeds the set value. If so, execute S103. In S102, specifically, the setpoint can be preset based on actual needs. For example, the setpoint can be set to 5% of the rated value. The rated value refers to the specified values ​​for voltage, current, power, etc., when the equipment is operating normally under specific technical conditions (such as cooling medium and environmental conditions). This application is not limited to this. The formula for calculating the negative sequence voltage amplitude is: ; In the formula, This represents the magnitude of the negative sequence voltage.

[0040] S103. Activate the negative sequence voltage outer loop control, generate a negative sequence current command, and activate the negative sequence current inner loop control. Based on the negative sequence current command, obtain the final negative sequence current command. Based on the final negative sequence current command, drive the inner loop current controller to output the corresponding current. In S103, specifically, when it is determined that the negative sequence voltage amplitude exceeds the set value, dual-loop control is performed. In the outer loop control, the negative sequence voltage outer loop control is activated to generate a negative sequence current command to suppress the negative sequence voltage to within 5% of the rated value, thereby achieving three-phase voltage balance. In the inner loop control, the negative sequence current inner loop control is activated to convert the negative sequence current command generated by the outer loop into an actual current output, thereby obtaining the final negative sequence current command. Based on the final negative sequence current command, the inner loop current controller is driven to output the corresponding current to cancel the negative sequence component.

[0041] In some embodiments, one implementation of the step of engaging negative-sequence voltage outer loop control to generate negative-sequence current commands specifically includes: S1031. Obtain the negative sequence component of the three-phase inverter AC voltage on the DQ axis, and calculate the deviation of the negative sequence D-axis voltage and the deviation of the negative sequence Q-axis voltage. The specific calculation formula is as follows: ; ; In the formula, This indicates the deviation of the negative sequence D-axis voltage. This represents the negative sequence component of the AC voltage of the three-phase inverter on the D-axis. This indicates the deviation of the negative sequence Q-axis voltage. This represents the negative sequence component of the AC voltage of a three-phase inverter on the Q-axis. Specifically, refer to Figure 2 As shown in the figure, the negative sequence voltage is embedded in virtual resistance and virtual inductance for decoupled calculation. This represents pi (which can take the value 3.1415926). Indicates virtual resistance. Represents virtual inductance. This indicates the AC voltage of the three-phase inverter. The three-phase inverter has a capacity of f, where f represents the frequency. The three-phase inverter AC voltage... The negative order components on the DQ axis include and .

[0042] S1032. Based on the deviations of the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage, decouple the virtual resistance and virtual inductance along the D and Q axes to obtain the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage. The specific calculation formula is as follows:

[0043] In the formula, This represents the negative-sequence D-axis voltage. Indicates the negative sequence Q-axis voltage; S1033. Based on the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage, the decoupling of the negative-sequence voltage in the current loop is calibrated to obtain the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration. The specific calculation formula is as follows: ; ; In the formula, This indicates negative sequence D-axis voltage calibration. Indicates negative sequence Q-axis voltage calibration; S1034. Obtain the negative sequence current command based on the negative sequence D-axis voltage calibration and the negative sequence Q-axis voltage calibration.

[0044] Specifically, based on the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration, a negative-sequence current command is generated through a proportional relationship. This negative-sequence current command includes... and , This indicates the command for negative sequence current on the D-axis. This command indicates the negative sequence current in the Q-axis region.

[0045] In the negative-sequence voltage outer loop, the negative-sequence D-axis voltage calibration and negative-sequence Q-axis voltage calibration are obtained through decoupling calculations. The negative-sequence current command is then directly generated through a proportional relationship (without an integral term). Essentially, this is a PI controller (integral term I=0, only the proportional term P is retained). Generally, a PI controller consists of a proportional term (P) and an integral term (I): the proportional term is used for rapid response to input deviations, and the integral term is used to eliminate steady-state errors. "Integral term I=0, only the proportional term P is retained" indicates that this stage is essentially a pure proportional (P) controller, a simplified form of a PI controller (retaining only proportional functionality). The negative-sequence voltage calibration and the negative-sequence current command have a proportional conversion relationship. The negative-sequence current command specifically includes... and , This indicates the command for negative sequence current on the D-axis. This command indicates the negative sequence current in the Q-axis region.

[0046] In other embodiments, one implementation of the step of engaging negative-sequence current inner-loop control and obtaining the final negative-sequence current command based on the negative-sequence current command specifically includes: S1034. Obtain the negative sequence components of the D-axis current and Q-axis current from the outer voltage loop. The calculation formula is as follows: ; In the formula, This represents the negative sequence component of the D-axis current. This represents the negative sequence component of the Q-axis current. Represents virtual capacitance. This represents the negative sequence component of the D-axis voltage. This represents the negative sequence component of the Q-axis voltage; Specifically, the negative sequence current is embedded in virtual capacitor control for decoupling calculation, and the given value of the negative sequence current loop is obtained from the voltage outer loop, including... and .

[0047] S1035. Based on the negative sequence components of the D-axis and Q-axis currents, perform decoupling calculations on the virtual capacitor along the DQ axes in the two-phase rotating coordinate system current to obtain the D-axis virtual capacitor compensation current and the Q-axis virtual capacitor compensation current. The calculation formulas are as follows: ; In the formula, This represents the virtual capacitor compensation current along the D-axis. This indicates the Q-axis virtual capacitor compensation current; S1036. Based on the D-axis virtual capacitor compensation current, Q-axis virtual capacitor compensation current, and negative sequence current command, the final negative sequence current command is obtained. The calculation formula is as follows: ; In the formula, This indicates a negative-sequence given D-axis current calibration. This indicates a negative-sequence given Q-axis current calibration; the final negative-sequence current command includes... and .

[0048] Specifically, the current is compensated by the decoupled virtual capacitor (including and ) and the negative sequence current command generated by the voltage outer loop (including and The superposition of these parameters yields the final negative sequence current command (including...). and This drives the inner loop current controller to output the corresponding current, thus canceling out the negative sequence component.

[0049] S104. Based on preset rules, adaptively determine the capacitance value of the virtual capacitor; Specifically, in S104, the virtual capacitor possesses capacitance characteristics simulated by an algorithm, playing a role in providing dynamic impedance compensation in negative-sequence control. The capacitance value of the virtual capacitor can be adaptively determined according to preset rules. The prediction rule can be the principle that "the more unbalanced the negative-sequence voltage, the stronger the compensation effect of the virtual capacitor." Specifically, when the negative-sequence voltage balance is poor, the virtual capacitor will enhance its compensation effect according to the preset rules to achieve voltage balance. In practical applications, the preset rules can also be other, and this application is not limited to them. The adaptive design of the virtual capacitor can adjust the equivalent capacitance parameters in real time according to the intensity of dynamic disturbances in the system. Combined with negative-sequence current embedding logic, the virtual capacitor can directly respond to current changes, shortening the system's dynamic response time and significantly improving anti-interference stability.

[0050] S105. The positive sequence voltage is embedded in the virtual resistor and virtual inductor for decoupling calculation to obtain the final positive sequence current command. Based on the final positive sequence current command, the inner loop current controller is driven to output the corresponding current.

[0051] Specifically, in S105, the calculation of embedding virtual resistance and inductance control with negative sequence voltage can be referenced. The calculation of embedding virtual resistance and virtual inductance with positive sequence voltage can be decoupled to obtain the final positive sequence current command. Then, based on the final positive sequence current command, the inner loop current controller is driven to output a current that can achieve power sharing, thereby realizing power sharing among multiple three-phase inverters.

[0052] In some embodiments, one implementation of the step of embedding the positive-sequence voltage into virtual resistors and virtual inductors for decoupled calculation to obtain the final positive-sequence current command specifically includes: S1051. Obtain the positive sequence component of the three-phase inverter AC voltage on the DQ axis, and calculate the deviation of the positive sequence D-axis voltage and the deviation of the positive sequence Q-axis voltage. The specific calculation formula is as follows: ; ; In the formula, This indicates the deviation of the positive-sequence D-axis voltage. This represents the positive-sequence component of the AC voltage of the three-phase inverter on the D-axis. This indicates the deviation of the positive-sequence Q-axis voltage. This represents the positive sequence component of the three-phase inverter AC voltage on the Q-axis; the positive sequence component of the three-phase inverter AC voltage on the DQ-axis includes... and ; S1052. Based on the deviations of the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, decouple the virtual resistance and virtual inductance along the D and Q axes to obtain the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage. The specific calculation formula is as follows:

[0053] In the formula, Represents the positive-sequence D-axis voltage. Represents the positive-sequence Q-axis voltage; S1053. Based on the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, the decoupling of the positive-sequence voltage in the current loop is calibrated to obtain the positive-sequence D-axis voltage calibration and the positive-sequence Q-axis voltage calibration. The specific calculation formula is as follows: ; ; In the formula, This indicates the positive-sequence D-axis voltage calibration. Indicates positive sequence Q-axis voltage calibration; S1054. Based on the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, the decoupling of the positive-sequence given current is calibrated to obtain the final positive-sequence current command. The calculation formula is as follows: ; ; In the formula, This indicates that the D-axis current is calibrated in positive sequence. This indicates positive-sequence given Q-axis current calibration. Represents the D-axis current. Represents the Q-axis current. Represents the positive-sequence D-axis voltage. This indicates the positive-sequence Q-axis voltage, and the final positive-sequence current command includes... and It drives the inner loop current controller and outputs a current that enables power sharing among multiple devices.

[0054] The beneficial effects of the above embodiments are as follows: (1) The outer loop of negative sequence voltage aims to suppress negative sequence voltage components and force the amplitude and phase of three-phase voltage to be symmetrical. It detects the negative sequence voltage deviation under unbalanced load in real time and outputs a negative sequence current reference command. The inner loop of negative sequence current quickly tracks the command and accurately compensates for the negative sequence current generated by load imbalance, thus solving the problem of three-phase voltage asymmetry from the source. (2) The adaptive design of virtual capacitor can adjust the equivalent capacitance parameters in real time according to the dynamic disturbance intensity of the system. Combined with the negative sequence current embedding logic, the virtual capacitor can directly respond to the current change, thereby shortening the dynamic response time of the system and significantly improving the anti-interference stability.

[0055] (3) Virtual resistors and virtual inductors are separated into active and reactive power regulation channels through decoupling design to avoid cross interference; at the same time, the positive sequence current command is dynamically corrected by voltage deviation to ensure that the active and reactive power of multiple inverters are evenly distributed.

[0056] (4) Based on local signals and without relying on communication methods, reliability is significantly improved. Furthermore, power sharing can be achieved simply by upgrading the software algorithm, without the need to replace the hardware of the device itself, resulting in low engineering application costs.

[0057] In summary, the above embodiments can improve the accuracy and reliability of power distribution in a three-phase inverter parallel system.

[0058] like Figure 3 As shown, in another embodiment of this application, a control system for power balancing and voltage balancing of a three-phase inverter is provided, comprising: The separation unit 10 is used to separate the positive and negative sequence components of voltage and current using a dual second-order generalized integrator. The judgment unit 11 is used to calculate the negative sequence voltage amplitude based on the separated negative sequence voltage component and to determine whether the negative sequence voltage amplitude exceeds the set value. The first control unit 12 is used to activate the negative sequence voltage outer loop control, generate a negative sequence current command, and activate the negative sequence current inner loop control when it is determined that the negative sequence voltage amplitude exceeds the set value. Based on the negative sequence current command, the final negative sequence current command is obtained, and the inner loop current controller is driven to output the corresponding current based on the final negative sequence current command. The determining unit 13 is used to adaptively determine the capacitance value of the virtual capacitor according to preset rules; The second control unit 14 is used to embed the positive sequence voltage into the virtual resistor and virtual inductor for decoupling calculation to obtain the final positive sequence current command, and drive the inner loop current controller to output the corresponding current based on the final positive sequence current command.

[0059] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for power balancing and voltage balancing of a three-phase inverter, characterized in that, include: A dual second-order generalized integrator is used to separate the positive and negative sequence components of voltage and current; Based on the separated negative sequence voltage component, the negative sequence voltage amplitude is calculated. It is then determined whether the negative sequence voltage amplitude exceeds a set value. If so, then: The outer loop control of negative sequence voltage is activated to generate a negative sequence current command, and the inner loop control of negative sequence current is activated. Based on the negative sequence current command, the final negative sequence current command is obtained, and the inner loop current controller is driven to output the corresponding current based on the final negative sequence current command. The capacitance value of the virtual capacitor is adaptively determined according to preset rules; The positive sequence voltage is embedded in virtual resistors and virtual inductors for decoupling calculation to obtain the final positive sequence current command. Based on the final positive sequence current command, the inner loop current controller is driven to output the corresponding current.

2. The method as described in claim 1, characterized in that, The positive-sequence transfer function of the dual second-order generalized integrator is: ； The negative-order transfer function of the dual second-order generalized integrator is: ； In the formula, This represents the orthogonal transfer function. This represents the negative-order transfer function. Indicates the damping coefficient. Indicates the resonant frequency. This represents the Laplace operator.

3. The method as described in claim 2, characterized in that, The method employs dual second-order generalized integrators to separate the positive and negative sequence components of voltage and current, including: By employing a dual second-order generalized integrator, the positive and negative sequence components of voltage and current are separated to obtain the negative sequence component of voltage, the positive sequence component of voltage, the negative sequence component of current, and the positive sequence component of current in the αβ coordinate system.

4. The method as described in claim 3, characterized in that, The expression for the negative sequence component of the voltage is: ； The expression for the positive sequence component of the voltage is: ； The expression for the positive sequence component of the current is: ； The expression for the negative sequence component of the current is: ； In the formula, This represents the voltage components in the α coordinate system. This represents the voltage components in the β coordinate system; This represents the components of the negative sequence voltage in the α coordinate system. This represents the negative sequence voltage component in the β coordinate system. This represents the positive-sequence voltage component in the α coordinate system. This represents the positive-sequence voltage component in the β coordinate system. This represents the components of the current in the α coordinate system. This represents the components of the current in the β coordinate system. This represents the positive sequence current component in the α coordinate system. This represents the positive sequence current component in the β coordinate system. This represents the component of the negative sequence current in the α coordinate system. This represents the component of the negative sequence current in the β coordinate system.

5. The method as described in claim 4, characterized in that, The formula for calculating the negative sequence voltage amplitude is: ； In the formula, This represents the magnitude of the negative sequence voltage.

6. The method as described in claim 5, characterized in that, The negative sequence voltage outer loop control, which generates a negative sequence current command, includes: Obtain the negative sequence component of the three-phase inverter AC voltage on the DQ axis, and calculate the deviation of the negative sequence D-axis voltage and the deviation of the negative sequence Q-axis voltage. The specific calculation formula is as follows: ； ； In the formula, This indicates the deviation of the negative sequence D-axis voltage. This represents the negative sequence component of the AC voltage of the three-phase inverter on the D-axis. This indicates the deviation of the negative-sequence Q-axis voltage. This represents the negative sequence component of the AC voltage of a three-phase inverter on the Q-axis. Based on the deviations of the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage, decoupling calculations are performed on the virtual resistance and virtual inductance along the D and Q axes to obtain the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage. The specific calculation formulas are as follows: In the formula, This represents the negative sequence D-axis voltage. Indicates virtual resistance. Represents pi (π). Represents virtual inductance. This represents the negative-sequence Q-axis voltage; Based on the negative-sequence D-axis voltage and the negative-sequence Q-axis voltage, the decoupling of the negative-sequence voltage in the current loop is calibrated to obtain the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration. The specific calculation formula is as follows: ； ； In the formula, This indicates the negative sequence D-axis voltage calibration. This indicates the negative-sequence Q-axis voltage calibration; Based on the negative sequence D-axis voltage calibration and the negative sequence Q-axis voltage calibration, the negative sequence current command is obtained.

7. The method as described in claim 6, characterized in that, The step of obtaining the negative-sequence current command based on the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration includes: Based on the negative-sequence D-axis voltage calibration and the negative-sequence Q-axis voltage calibration, a negative-sequence current command is generated through a proportional relationship, wherein the negative-sequence current command includes... and , This indicates the command for negative sequence current on the D-axis. This command indicates the negative sequence current in the Q-axis region.

8. The method as described in claim 7, characterized in that, The inner loop control for inputting negative sequence current, based on the negative sequence current command, obtains the final negative sequence current command, including: The negative sequence components of the D-axis current and Q-axis current are obtained from the outer voltage loop, and the calculation formula is as follows: ； In the formula, This represents the negative sequence component of the D-axis current. This represents the negative sequence component of the Q-axis current. Represents virtual capacitance. This represents the negative sequence component of the D-axis voltage. This represents the negative sequence component of the Q-axis voltage; Based on the negative sequence components of the D-axis and Q-axis currents, the virtual capacitor is decoupled along the D and Q axes in the two-phase rotating coordinate system current to obtain the D-axis virtual capacitor compensation current and the Q-axis virtual capacitor compensation current. The calculation formulas are as follows: ； In the formula, This represents the virtual capacitor compensation current along the D-axis. This indicates the Q-axis virtual capacitor compensation current; Based on the D-axis virtual capacitor compensation current, the Q-axis virtual capacitor compensation current, and the negative sequence current command, the final negative sequence current command is obtained, and the calculation formula is as follows: ； In the formula, This indicates a negative-sequence given D-axis current calibration. This indicates a negative-sequence given Q-axis current calibration, the final negative-sequence current command including... and .

9. The method as described in claim 8, characterized in that, The step of embedding the positive-sequence voltage into virtual resistance and virtual inductance for decoupling calculation to obtain the final positive-sequence current command includes: Obtain the positive-sequence component of the three-phase inverter AC voltage on the DQ axis, and calculate the deviation of the positive-sequence D-axis voltage and the deviation of the positive-sequence Q-axis voltage. The specific calculation formula is as follows: ； ； In the formula, This indicates the deviation of the positive-sequence D-axis voltage. This represents the positive-sequence component of the AC voltage of the three-phase inverter on the D-axis. This indicates the deviation of the positive-sequence Q-axis voltage. This represents the positive sequence component of the AC voltage of a three-phase inverter on the Q-axis. Based on the deviations of the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, decoupling calculations are performed on the virtual resistance and virtual inductance along the D and Q axes to obtain the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage. The specific calculation formulas are as follows: In the formula, This represents the positive-sequence D-axis voltage. This represents the positive-sequence Q-axis voltage; Based on the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, the decoupling of the positive-sequence voltage in the current loop is calibrated to obtain the positive-sequence D-axis voltage calibration and the positive-sequence Q-axis voltage calibration. The specific calculation formula is as follows: ； ； In the formula, This indicates the positive-sequence D-axis voltage calibration. This indicates the positive-sequence Q-axis voltage calibration; Based on the positive-sequence D-axis voltage and the positive-sequence Q-axis voltage, the decoupling of the positive-sequence given current is calibrated to obtain the final positive-sequence current command. The calculation formula is as follows: ； ； In the formula, This indicates that the D-axis current is calibrated in positive sequence. This indicates positive-sequence given Q-axis current calibration. Represents the D-axis current. Indicating the Q-axis current, the final positive sequence current command includes... and .

10. A control system for power balancing and voltage balancing of a three-phase inverter, characterized in that, include: The separation unit is used to separate the negative sequence component of the voltage using a dual second-order generalized integrator, thus separating the positive and negative sequence components of the voltage and current. The judgment unit is used to calculate the negative sequence voltage amplitude based on the separated negative sequence voltage component and to determine whether the negative sequence voltage amplitude exceeds a set value. The first control unit is used to, when it is determined that the amplitude of the negative sequence voltage exceeds the set value, engage the outer loop control of the negative sequence voltage, generate a negative sequence current command, engage the inner loop control of the negative sequence current, obtain the final negative sequence current command according to the negative sequence current command, and drive the inner loop current controller to output the corresponding current based on the final negative sequence current command. The determining unit is used to adaptively determine the capacitance value of the virtual capacitor according to preset rules; The second control unit is used to embed the positive sequence voltage into virtual resistors and virtual inductors for decoupling calculation to obtain the final positive sequence current command, and drive the inner loop current controller to output the corresponding current based on the final positive sequence current command.

Images