Parallel system of fractional order single-phase inverter and circulating current suppression method, device and medium thereof

Abstract

This invention discloses a parallel system of fractional-order single-phase inverters and its circulating current suppression method, device, and medium. The method includes: establishing a mathematical model of the fractional-order single-phase inverter; constructing a dual closed-loop control loop based on the mathematical model; and controlling the output voltage and output current of the parallel fractional-order single-phase inverters. i 0 Perform tracking control; calculate the initial reference voltage through droop control. U r0 Based on the inverter's droop factor and reactive power, calculate the adaptive virtual inductance and adaptive virtual resistance of the fractional-order single-phase inverter; based on the adaptive virtual inductance and adaptive virtual resistance of the fractional-order single-phase inverter, calculate the voltage drop that should be generated by the adaptive virtual impedance; based on the initial reference voltage... U r0 The voltage drop caused by the virtual impedance is used to obtain the controller reference voltage. U r ; set the controller reference voltage U r This invention serves as the input to a controller-based dual-closed-loop control loop to control the operation of a fractional-order single-phase inverter. It effectively suppresses circulating current.

Description

Technical Field

[0001] This invention relates to the field of inverter control technology, and in particular to a parallel system of fractional-order single-phase inverters and its circulating current suppression method, device and medium. Background Technology

[0002] A fractional-order inverter is a power electronic device composed of fractional-order capacitors and inductors. Compared with traditional integer-order inverters, it has better dynamic response and higher energy transfer efficiency, and has been widely used in new energy, medical equipment, and other fields. In practical applications, multiple inverters are often operated in parallel to improve system capacity and reliability. However, inconsistencies in the electrical parameters of each inverter can lead to circulating currents, causing overheating or even damage to the equipment.

[0003] In existing technologies, droop control and fixed virtual impedance control are the main methods for suppressing parallel circulating currents. Under inductive line impedance conditions, to ensure that the reactive power of each distributed power unit is distributed proportionally to its rated capacity, the system impedance must be proportional to the reactive power droop factor and inversely proportional to the output reactive power. However, actual line impedances are difficult to precisely match this ideal condition, meaning that fixed virtual impedance cannot completely solve the problem of inaccurate reactive power distribution.

[0004] To address this, some studies have proposed an adaptive virtual impedance strategy to achieve precise reactive power allocation by dynamically adjusting the equivalent system impedance. However, existing adaptive virtual impedance methods are all based on integer-order inverter models and fail to consider the fractional-order characteristics of fractional-order components. Currently, there is a lack of circulating current suppression techniques based on adaptive virtual impedance for parallel fractional-order inverter systems. Summary of the Invention

[0005] This invention provides a parallel system of fractional single-phase inverters and its circulating current suppression method, device and medium to overcome the defects in the prior art. By dynamically adjusting the system impedance, it achieves precise distribution of reactive power in the parallel system of fractional single-phase inverters, thereby effectively suppressing circulating current.

[0006] According to one aspect of the present invention, a method for suppressing parallel circulating current in a fractional-order single-phase inverter is provided, comprising: A mathematical model of a fractional-order single-phase inverter is established; the mathematical model includes fractional-order inductors and fractional-order capacitors. Based on the mathematical model, a dual closed-loop control loop based on a fractional-order controller is constructed, and the output voltage of the parallel fractional-order single-phase inverter is controlled. and output current i 0 Perform tracking and control; The initial reference voltage is calculated using droop control. Ur0 ; Based on the droop coefficient of the fractional-order single-phase inverter and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ; Based on the adaptive virtual inductor of the fractional-order single-phase inverter and adaptive virtual resistance Calculate the voltage drop that the adaptive virtual impedance should produce. ; According to the initial reference voltage U r0 and the voltage drop that the virtual impedance should produce. The controller reference voltage is obtained. U r ; The controller reference voltage U r This serves as the input to the dual closed-loop control loop based on the fractional-order controller to control the operation of the fractional-order single-phase inverter.

[0007] Optionally, a mathematical model of a fractional-order single-phase inverter is established, including: Based on Kirchhoff's laws, a circuit topology analysis is performed on the parallel system of fractional single-phase inverters, which includes fractional inductors and fractional capacitors, to determine the state equations of the fractional inductors and fractional capacitors in a single fractional single-phase inverter. Based on the output voltage of the fractional-order single-phase inverter The two-phase stationary coordinate system is obtained. , The mathematical expression of the component in the time domain; Will , The components are transformed by Park to obtain the state equations of the fractional inductor and the fractional capacitor on the synchronously rotating coordinate axis.

[0008] Optionally, the initial reference voltage can be calculated using droop control. U r0 ,include: Based on the output voltage of the fractional-order single-phase inverter Output current i 0 Rated active power and rated reactive power The active power deviation and reactive power deviation are obtained. The active power deviation is added to the given angular frequency through the active power-frequency droop coefficient m. The angular frequency setting value is obtained above. The reactive power deviation is then added to the given voltage amplitude through a reactive power-voltage droop coefficient n. The voltage amplitude setpoint is obtained. ; According to the angular frequency setting value and the voltage amplitude setting value Determine the initial reference voltage U r0 .

[0009] Optionally, based on the output voltage of the fractional-order single-phase inverter Output current i 0 Rated active power and rated reactive power The active power deviation and reactive power deviation are obtained, including: Based on the output voltage of the fractional-order single-phase inverter and output current i 0 The output voltage signal in the synchronous rotating coordinate system is obtained. , and output current signal , ; Based on the output voltage signal in the synchronous rotating coordinate system , and output current signal , The active power is obtained through formula (1). P and reactive power Q Formula (1) is as follows: ; Rated active power With the active power P The difference is used to obtain the active power deviation, and the rated reactive power is then calculated. With the reactive power Q The reactive power deviation is obtained by subtracting the reactive power.

[0010] Optionally, based on the droop coefficient of the fractional-order single-phase inverter and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ,include: Based on the droop coefficient of the i-th fractional-order single-phase inverter and reactive power The virtual impedance correction term is obtained. ; Based on the virtual impedance correction term The adaptive virtual inductance of the i-th fractional single-phase inverter is obtained through formula (2). and adaptive virtual resistance Formula (2) is as follows: ; in, The base value of the virtual inductance designed to protect the circuit impedance from inductive behavior. The base value of the virtual resistor is designed to protect the circuit impedance from being inductive. It is the adaptive inductor for adjusting the i-th fractional-order single-phase inverter. It is the proportional gain of the adaptive resistor of the i-th fractional-order single-phase inverter.

[0011] Optionally, based on the droop coefficient of the i-th fractional-order single-phase inverter. and reactive power The virtual impedance correction term is obtained. ,include: Based on the droop coefficient of the i-th fractional-order single-phase inverter and reactive power The product of, and the droop coefficient of the j-th fractional-order single-phase inverter. and reactive power The product of is calculated to obtain ;in, It is the control gain of the i-th fractional-order single-phase inverter; e qi It is the reactive power distribution error of the i-th fractional-order single-phase inverter; ; based on After passing through a fractional-order proportional-integral controller, the virtual impedance correction term is obtained through formula (3). Formula (3) is as follows: ; It is the proportional control coefficient of the i-th fractional-order single-phase inverter. It is the integral control coefficient of the i-th fractional-order single-phase inverter. For fractional order, s It is a complex frequency.

[0012] Optionally, an adaptive virtual inductance based on the fractional-order single-phase inverter. and adaptive virtual resistance Calculate the voltage drop that should be generated by the virtual impedance. ,include: Based on the adaptive virtual inductor of the fractional-order single-phase inverter and adaptive virtual resistance The voltage drop that the virtual impedance should produce is calculated using formula (3). Formula (4) is as follows: ;in, Let be the output current of the i-th fractional-order single-phase inverter.

[0013] Optionally, a dual closed-loop control loop based on a fractional-order controller is constructed based on the mathematical model, including: A current control loop employing fractional-order current loop control is constructed; the transfer function of the current control loop is as follows: ;in, This is the proportionality coefficient; A voltage control loop employing fractional-order current loop control is constructed; the transfer function of the voltage control loop is as follows: ;in, This is the proportionality coefficient. The integral coefficient is... For the fractional order of the voltage controller, s It is a complex frequency.

[0014] Secondly, the present invention provides a parallel circulating current suppression device for a fractional-order single-phase inverter, comprising: The mathematical model building module is used to build a mathematical model of a fractional-order single-phase inverter; the mathematical model includes fractional-order inductors and fractional-order capacitors. The voltage control module is used to construct a dual closed-loop control loop based on the mathematical model and a fractional-order controller, and to control the output voltage of the parallel fractional-order single-phase inverters. and output current i 0 Perform tracking and control; The initial reference voltage calculation module is used to calculate the initial reference voltage through droop control. U r0 ; An adaptive virtual resistance calculation module is used to calculate the droop coefficient based on the fractional-order single-phase inverter. and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ; The voltage drop calculation module is used to calculate the adaptive virtual inductance based on the fractional-order single-phase inverter. and adaptive virtual resistance Calculate the voltage drop that the adaptive virtual impedance should produce. ; The controller reference voltage calculation module is used to calculate the reference voltage based on the initial reference voltage. U r0 and the voltage drop that the virtual impedance should produce. The controller reference voltage is obtained. U r ; The control module is used to set the controller reference voltage. U rA As input to the dual closed-loop control loop based on a fractional-order controller, the fractional-order single-phase inverter is controlled to operate.

[0015] Thirdly, the present invention provides a parallel system of fractional-order single-phase inverters, comprising: The controller is capable of executing the parallel circulating current suppression method for fractional-order single-phase inverters described in any of the preceding claims.

[0016] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a processor to execute and implement the parallel circulating current suppression method for a fractional-order single-phase inverter as described in any of the preceding claims.

[0017] This invention establishes a mathematical model of a fractional-order single-phase inverter, including fractional-order inductors and fractional-order capacitors. Based on this mathematical model, a dual-closed-loop control loop based on a fractional-order controller is constructed, and the output voltage of the parallel-connected fractional-order single-phase inverters is controlled. and output current i 0 Tracking control is performed, and the initial reference voltage is calculated through droop control. U r0 Meanwhile, based on the droop coefficient of the fractional-order single-phase inverter and reactive power Calculate the adaptive virtual inductance of a fractional-order single-phase inverter. and adaptive virtual resistance And based on the adaptive virtual inductance of the fractional-order single-phase inverter and adaptive virtual resistance Calculate the voltage drop that should be generated by the adaptive virtual impedance. Then based on the initial reference voltage U r0 and the voltage drop that should be generated by virtual impedance The controller reference voltage is obtained. U r Finally, the controller reference voltage U rThis serves as the input to the dual closed-loop control loop of a fractional-order controller to control the operation of the fractional-order single-phase inverter. Thus, by designing the adaptive virtual impedance of the fractional-order single-phase inverter, reactive power can be precisely distributed without changing the actual line parameters, thereby ensuring that the output voltages of parallel fractional-order single-phase inverters are equal, effectively suppressing circulating current.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a parallel circulating current suppression method for a fractional-order single-phase inverter provided in Embodiment 1 of the present invention; Figure 2 The main circuit topology of the parallel system of fractional-order single-phase inverters provided in the embodiments of the present invention; Figure 3 This is a flowchart of the parallel circulating current suppression method for a fractional-order single-phase inverter provided in Embodiment 2 of the present invention; Figure 4 This is a control block diagram of a parallel circulating current suppression method for a fractional-order single-phase inverter provided in an embodiment of the present invention. Figure 5 This is a control block diagram of the dual closed-loop control section of a fractional-order single-phase inverter provided in an embodiment of the present invention; Figure 6 This is a circulating current diagram of an embodiment of the present invention without an adaptive virtual impedance. Figure 7 The circulating current diagram of the adaptive virtual impedance provided in this embodiment of the invention; Figure 8 This is a schematic diagram of the parallel circulating current suppression device for a fractional-order single-phase inverter provided in Embodiment 3 of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] Figure 1 This is a flowchart of a parallel circulating current suppression method for a fractional-order single-phase inverter provided in Embodiment 1 of the present invention. This embodiment is applicable to suppressing circulating current in a parallel system of fractional-order single-phase inverters. The method is executed by a parallel circulating current suppression device of the fractional-order single-phase inverter, which can be implemented in hardware and / or software and can be configured in electronic equipment. Figure 1 As shown, the parallel circulating current suppression method for this fractional-order single-phase inverter includes: S110. Establish the mathematical model of the fractional-order single-phase inverter.

[0024] The mathematical model includes fractional-order inductors and fractional-order capacitors.

[0025] Figure 2 This embodiment of the invention provides the main circuit topology of a parallel system of fractional-order single-phase inverters. The parallel system of fractional-order single-phase inverters provided in this embodiment is a system in which at least two fractional-order single-phase inverters are connected in parallel to convert DC power to AC power. (Refer to...) Figure 2 As shown, each inverter includes electronic switches T1, T2, T3, and T4. The DC-side voltage at the input of each fractional-order single-phase inverter is... U dc The DC side voltage U dcThis can be the voltage output from an energy storage device or a photovoltaic device. To stabilize the DC-side voltage, a large capacitor C is typically connected in parallel on the DC side. The inverter's output voltage is u. L The output voltage after passing through a fractional-order LC filter The filter inductor is a fractional-order inductor. This indicates that the equivalent resistance value is The current per phase after passing through the filter inductor is The filter capacitors are all fractional-order capacitors. This indicates that, due to the random distribution of inverter locations in practical applications, the line impedance of the inverter connected to the microgrid PCC cannot be ignored. The inductance and resistance values ​​in the inverter line impedance are respectively... and The currents flowing through the line impedance are respectively . For load resistance, and For another type of load, consider the inductance and resistance.

[0026] A fractional inductor is an inductor with non-integer-order calculus characteristics. Its response is proportional to the non-integer derivative of the input signal. A fractional capacitor is a capacitor model based on fractional calculus theory. Its capacitance value has fractional-order power characteristics, which are significantly different from traditional integer-order capacitors in terms of frequency response and impedance characteristics. A fractional inverter is a new type of inverter that combines fractional calculus theory with power electronics technology. Its core lies in using fractional-order components (such as fractional inductors and capacitors) and fractional-order control algorithms to improve system performance.

[0027] The mathematical model of a fractional inverter can be based on fractional calculus theory, using non-integer order differential equations to describe its dynamic characteristics. Specifically, in this embodiment, it can first be based on Kirchhoff's laws... Figure 2 The circuit topology of a parallel system of fractional single-phase inverters, including fractional inductors and capacitors, is analyzed to determine the state equations of the fractional inductors and capacitors in a single fractional single-phase inverter. Then, the AC signal in the stationary coordinate system is converted into the dq DC component in the synchronous rotating coordinate system through the Park transformation matrix, and the state equations of the fractional inductors and capacitors in the synchronous rotating coordinate system are obtained.

[0028] S120. Based on a mathematical model, a dual closed-loop control loop based on a fractional-order controller is constructed, and the output voltage of the parallel fractional-order single-phase inverter is controlled. u 0 and output current i 0To implement tracking and control.

[0029] This embodiment employs a voltage and current dual control loop based on a fractional-order controller. This dual control loop is an advanced control method that combines fractional-order control theory with a dual closed-loop control strategy. The inner current loop uses fractional-order current loop control to track changes in the inverter's output current, quickly respond to harmonic disturbances, and improve filtering performance. The outer voltage loop uses fractional-order current loop control to regulate the stability of the DC-side voltage, ensuring that the output voltage remains constant during load changes or voltage fluctuations.

[0030] In this embodiment, a voltage and current dual control loop based on a fractional-order controller can be constructed based on the above mathematical model. Optionally, a current control loop using fractional-order current loop control can be constructed, with the open-loop transfer function of the current loop control having at least fractional-order inductance and equivalent impedance as variables. Similarly, a voltage control loop using fractional-order current loop control can be constructed, with the open-loop transfer function of the current loop control having at least fractional-order inductance and equivalent impedance as variables. After constructing the voltage and current dual control loop based on a fractional-order controller, the output voltage and current of the parallel fractional-order single-phase inverters can be tracked and controlled through the voltage and current dual control loop to ensure that the output voltage of each parallel fractional-order single-phase inverter is equal, thereby reducing the voltage difference.

[0031] S130, Calculate the initial reference voltage using droop control. U r0 .

[0032] Droop control is a control strategy widely used in microgrids and parallel inverter systems. It establishes a linear relationship between output power and voltage amplitude / frequency, enabling the inverter to automatically adjust its output characteristics when the load changes. Specifically, in this embodiment, the output voltage and current of the fractional-order single-phase inverter are detected, and the active power of the fractional-order single-phase inverter is calculated using Park transformation. P and reactive power Q And based on active power P reactive power Q Rated active power P 0 and rated reactive power Q 0 The angular frequency setpoint is determined by the droop equation. and voltage amplitude setting value E Finally, based on the angular frequency setting value The phase angle is obtained and used to synthesize the phase component of the initial reference voltage, and then combined with the voltage amplitude E to synthesize the initial reference voltage. U r0 .

[0033] S140, Droop coefficient based on fractional-order single-phase inverter n i and reactive power Q i Calculate the adaptive virtual inductance of a fractional-order single-phase inverter. L vi and adaptive virtual resistance R vi .

[0034] Among them, the droop factor of the fractional-order single-phase inverter is the core parameter in droop control, defining the linear proportional relationship between the output power of the fractional-order single-phase inverter and the system frequency or voltage amplitude. Specifically, in this embodiment, based on the i-th and j-th fractional-order single-phase inverters... and Calculated ,in, Let be the reactive power-frequency droop coefficient of the i-th fractional-order single-phase inverter. Let be the reactive power-frequency droop coefficient of the j-th fractional-order single-phase inverter. The reactive power of the i-th fractional-order single-phase inverter, and Let be the reactive power of the j-th fractional-order single-phase inverter. It is the first i Control gain of a fractional-order single-phase inverter This is the synchronization error, i.e., the reactive power distribution error. Then, based on the above... via a fractional proportional-integral controller (PI) λ (Control), to obtain the value of the virtual impedance correction term. Synchronization error is established by controlling the gain and using a fractional-order proportional-integral controller. and virtual impedance correction term The connection ensures the stability of the parallel system of fractional-order single-phase inverters. Finally, the virtual impedance correction term... Obtain the adaptive virtual inductance of the i-th fractional single-phase inverter. and adaptive virtual resistance .

[0035] S150, Adaptive Virtual Inductor Based on Fractional Single-Phase Inverter L vi and adaptive virtual resistance R vi Calculate the voltage drop that should be generated by the adaptive virtual impedance. V i .

[0036] Specifically, based on the adaptive virtual inductance and adaptive virtual resistance obtained from S140 According to the formula: Calculate the voltage drop that should be generated by the adaptive virtual impedance of the i-th fractional-order single-phase inverter. .in, Let be the output current of the i-th fractional-order single-phase inverter.

[0037] S160, Based on the initial reference voltage U r0 and the voltage drop that should be generated by virtual impedance V i The controller reference voltage is obtained. U r .

[0038] Specifically, the initial reference voltage obtained through droop control... U r0 The voltage drop calculated above The difference is calculated to obtain a new reference voltage, which is then used as the controller reference voltage. U r Enter the fractional-order controller.

[0039] S170, Set the controller reference voltage U r It serves as the input to the dual closed-loop control loop of a fractional-order controller to control the operation of the inverter.

[0040] In this embodiment, a mathematical model of a fractional-order single-phase inverter, including fractional-order inductors and capacitors, is established. Based on this mathematical model, a dual-closed-loop control loop based on a fractional-order controller is constructed, and the output voltage of the parallel fractional-order single-phase inverters is controlled. and output current i 0 Tracking control is performed, and the initial reference voltage is calculated through droop control. U r0 Meanwhile, based on the droop coefficient of the fractional-order single-phase inverter and reactive power Calculate the adaptive virtual inductance of a fractional-order single-phase inverter. and adaptive virtual resistance And based on the adaptive virtual inductance of the fractional-order single-phase inverter and adaptive virtual resistance Calculate the voltage drop that should be generated by the adaptive virtual impedance. Then based on the initial reference voltage U r0 and the voltage drop that should be generated by virtual impedance The controller reference voltage is obtained. Ur Finally, the controller reference voltage U r This serves as the input to the dual closed-loop control loop of a fractional-order controller to control the operation of the fractional-order single-phase inverter. Thus, by designing the adaptive virtual impedance of the fractional-order single-phase inverter, reactive power can be precisely distributed without changing the actual line parameters, thereby ensuring that the output voltages of parallel fractional-order single-phase inverters are equal, effectively suppressing circulating current.

[0041] Example 2 Figure 3 This is a flowchart of the parallel circulating current suppression method for a fractional-order single-phase inverter provided in Embodiment 2 of the present invention. Figure 4 This is a control block diagram of a parallel circulating current suppression method for a fractional-order single-phase inverter provided in an embodiment of the present invention. This embodiment is a further optimization based on the above embodiment. (See reference...) Figure 3 and Figure 4 As shown, the parallel circulating current suppression method for this fractional-order single-phase inverter includes: S210. Based on Kirchhoff's laws, perform circuit topology analysis on a parallel system of fractional-order single-phase inverters, including fractional-order inductors and fractional-order capacitors, and determine the state equations of fractional-order inductors and fractional-order capacitors in a single fractional-order single-phase inverter.

[0042] The state equations for the fractional-order inductor and the fractional-order capacitor in a single fractional-order single-phase inverter are as follows: ; in, The order of the fractional inductor. The order of the fractional capacitor is given by [the order of the capacitor]. t It is a time variable.

[0043] S220, Output voltage based on fractional-order single-phase inverter u 0 The two-phase stationary coordinate system is obtained. α、β The mathematical expression of the component in the time domain.

[0044] Specifically, the output voltage of the fractional-order single-phase inverter Considered as a two-phase stationary coordinate system Components, by constructing their orthogonal signals Thus forming a complete - The specific process for the two-phase stationary coordinate system is as follows: The output voltage of the fractional-order single-phase inverter The output signal obtained after passing through the second-order generalized integrator (SOGI) is used as a two-phase stationary coordinate system. The transfer functions of the two signals, SOGI and SOGI, are: ; in, It is the fundamental angular frequency. It is a proportionality coefficient. s is the SOGI input signal, and s is the complex frequency.

[0045] but , The mathematical expression for the component in the time domain is as follows: .

[0046] S230, will α、β After Park transformation, the components yield the state equations of fractional inductance and fractional capacitance on the synchronously rotating coordinate axis.

[0047] Specifically, the S220 obtained , The signal is transformed by Park to obtain the synchronous rotating coordinate axis d / q signal, where the Park transformation uses an on-axis delay. Calculation method: ; The mathematical model of a fractional-order single-phase inverter in a two-phase stationary coordinate system is as follows: ; The mathematical expression for the fractional-order single-phase inverter on the synchronous rotating coordinate axis d / q, obtained after Park transformation, is as follows: ; in, , These are the capacitor voltages of a fractional-order single-phase inverter. In the synchronous rotating coordinate system, the components of the d / q axes, , Let represent the components of the output current of the fractional-order single-phase inverter along the d / q axes in the synchronous rotating coordinate system. , These are the components of the inductor current of a fractional-order single-phase inverter along the d / q axes of the synchronous rotating coordinate system.

[0048] S240, Output voltage of parallel fractional-order single-phase inverters u0 and output current i 0 To implement tracking and control.

[0049] Figure 5 The control block diagram of the dual closed-loop control section of the fractional-order single-phase inverter provided in this embodiment of the invention is shown below. Figure 5 As shown, taking the d-axis as an example, G1(s) is the transfer function of the current loop controller, and G2(s) is the transfer function of the voltage loop controller. For the fractional order of the voltage controller, s It is a complex frequency. This represents the time coefficient for the inertial element. For filtering inductors, Parasitic resistance, This is a filter capacitor.

[0050] In this embodiment, by constructing a current control loop using fractional-order current loop control, the current control loop can give the voltage control loop better anti-interference performance; the transfer function of the current control loop is as follows: .in, This is the proportionality coefficient.

[0051] A voltage control loop using fractional-order current loop control is constructed; the transfer function of the voltage control loop is as follows: .in, This is the proportionality coefficient. The integral coefficient is... This represents the fractional order of the voltage loop controller.

[0052] S250, Output voltage based on fractional-order single-phase inverter u 0 Output current i 0 Rated active power P 0 and rated reactive power Q 0 The active power deviation and reactive power deviation are obtained.

[0053] Specifically, the output voltage of a fractional-order single-phase inverter and output current i 0 Generate two-phase stationary coordinate systems using a second-order generalized integrator. The signal, and then the output voltage and output current i 0 of The signal is generated in a synchronous rotating coordinate system through Park transformation. Signal , , , ,based on , , , Generating active power and reactive power Subsequently, the active power With rated active power The difference is used to obtain the active power deviation, and the reactive power deviation is calculated accordingly. With rated reactive power The reactive power deviation is obtained by subtracting the reactive power.

[0054] In an alternative embodiment, the output voltage based on a fractional-order single-phase inverter Output current i 0 Rated active power and rated reactive power The active power deviation and reactive power deviation are obtained, including: Output voltage based on fractional-order single-phase inverter and output current i 0 The output voltage signal in the synchronous rotating coordinate system is obtained. , and output current signal , ; Based on the output voltage signal in the synchronous rotating coordinate system , and output current signal , The active power is obtained through formula (1). P and reactive power Q ; Formula (1) is as follows: ; S260. The active power deviation is added to the given angular frequency through the active power-frequency droop coefficient m. The angular frequency setting value is obtained above. ω The reactive power-power deviation is then added to the given voltage amplitude through the reactive power-voltage droop coefficient n. E n The voltage amplitude setpoint is obtained. E .

[0055] Specifically, the active power deviation is added to the given angular frequency through the active power-frequency droop coefficient m. The angular frequency setting value is obtained above. This achieves active power-frequency regulation. Reactive power deviation is added to the given voltage amplitude through a reactive power-voltage droop coefficient n. The voltage amplitude setting value is obtained above. This enables reactive power-voltage regulation.

[0056] S270, Based on the angular frequency setting value ω and voltage amplitude setting value E Determine the initial reference voltage U r0 .

[0057] In an optional embodiment, the angular frequency setting value The phase angle is obtained by integration and used to synthesize the phase part of the reference voltage, which is then combined with the voltage amplitude E to synthesize the initial reference voltage. U r0 .

[0058] S280, droop coefficient based on the i-th fractional-order single-phase inverter n i and reactive power Q i The virtual impedance correction term is obtained. δQ i .

[0059] Specifically, the droop coefficient based on the i-th fractional-order single-phase inverter. and reactive power And the droop coefficient of the j-th fractional-order single-phase inverter. and reactive power ,get ;in, It is the control gain of the i-th fractional-order single-phase inverter; e qi It is the reactive power distribution error of the i-th fractional-order single-phase inverter; Based on the above... The value of the virtual impedance correction term is obtained through formula (3) using a fractional-order proportional-integral controller. Formula (3) is as follows: ; in, It is the proportional control coefficient of the i-th inverter. These are the integral control coefficients of the i-th fractional-order single-phase inverter. For fractional order, s It is a complex frequency, thus establishing synchronization error by controlling the gain and a fractional-order proportional-integral controller. and virtual impedance correction term The connections ensure the system remains stable.

[0060] In an alternative embodiment, the droop coefficient is based on the i-th fractional-order single-phase inverter. and reactive power And the droop coefficient of the j-th fractional-order single-phase inverter. and reactive power ,get Including: the droop coefficient based on the i-th fractional-order single-phase inverter and reactive power The product of, and the droop coefficient of the j-th fractional-order single-phase inverter. and reactive power The product is calculated to obtain .

[0061] S290, Based on virtual impedance correction term δQ i The adaptive virtual inductance of the i-th fractional-order single-phase inverter is obtained through formula (2). L vi and adaptive virtual resistance R vi .

[0062] Formula (2) is as follows: ; in, The base value of the virtual inductance designed to protect the circuit impedance from inductive behavior. The base value of the virtual resistor is designed to protect the circuit impedance from being inductive. It is the adaptive inductor for regulating the i-th fractional-order single-phase inverter. It is the proportional gain of the adaptive resistor of the i-th fractional-order single-phase inverter.

[0063] S2100, Adaptive Virtual Inductor Based on Fractional Single-Phase Inverter L vi and adaptive virtual resistance R vi Calculate the voltage drop that should be generated by the adaptive virtual impedance. V i .

[0064] Specifically, adaptive virtual inductance based on fractional-order single-phase inverters and adaptive virtual resistance The voltage drop that should be generated by the virtual impedance is calculated using formula (4). ; Formula (4) is as follows: ; in, Let be the output current of the i-th fractional-order single-phase inverter.

[0065] S2110, Based on the initial reference voltage U r0 and the voltage drop that should be generated by virtual impedance V i The controller reference voltage is obtained. U r .

[0066] S2120, Set the controller reference voltage U r It serves as the input to the dual closed-loop control loop of a fractional-order controller to control the operation of a fractional-order single-phase inverter.

[0067] In this embodiment, after designing the adaptive fractional-order virtual impedance, the initial reference voltage obtained from the droop control is... U r0 The voltage drop obtained by subtracting the voltage drop from the adaptive fractional-order virtual impedance part is used to obtain the controller reference voltage input to the fractional-order controller to adjust the voltage and output power of the fractional-order single-phase inverter, so that the voltage of each inverter in the fractional-order single-phase inverter parallel system is consistent, achieving power distribution and thus suppressing parallel circulating current.

[0068] To verify the effectiveness of the proposed circulating current suppression strategy, a microgrid simulation system consisting of two inverters was built on MATLAB / Simulink. The simulation parameters are as follows: Table 1 Simulation parameters of a microgrid consisting of two inverters To verify the effectiveness of the adaptive virtual impedance provided by this scheme, parallel control simulations were performed on two fractional-order single-phase inverters connected to the adaptive virtual impedance and two fractional-order single-phase inverters not connected to the adaptive virtual impedance. Figure 6 This is a circulating current diagram of an embodiment of the present invention without an adaptive virtual impedance. Figure 7 The circulating current diagram of the adaptive virtual impedance provided in this embodiment of the invention is shown in the reference diagram. Figure 6 and Figure 7 It is evident that without the adaptive virtual impedance circuit, circulating current occurs between the two fractional-order single-phase inverters due to the difference in line impedance. After the adaptive virtual impedance is connected, the circulating current is significantly suppressed.

[0069] Example 3 This embodiment provides a parallel circulating current suppression device for a fractional-order single-phase inverter. This device can be implemented in hardware and / or software and can be integrated into electronic devices. Figure 8This is a schematic diagram of the parallel circulating current suppression device for a fractional-order single-phase inverter provided in Embodiment 3 of the present invention, as shown below. Figure 8 As shown, the device includes: Mathematical model building module 310 is used to build a mathematical model of a fractional-order single-phase inverter; the mathematical model includes fractional-order inductors and fractional-order capacitors. The voltage control module 320 is used to construct a dual closed-loop control loop based on the mathematical model and a fractional-order controller, and to control the output voltage of the parallel fractional-order single-phase inverter. and output current i 0 Perform tracking and control; Initial reference voltage calculation module 330 is used to calculate the initial reference voltage through droop control. U r0 ; The adaptive virtual resistance calculation module 340 is used to calculate the droop coefficient of the fractional-order single-phase inverter. and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ; Voltage drop calculation module 350 is used for adaptive virtual inductance based on the fractional-order single-phase inverter. and adaptive virtual resistance Calculate the voltage drop that the adaptive virtual impedance should produce. ; The controller reference voltage calculation module 360 ​​is used to calculate the reference voltage based on the initial reference voltage. U r0 and the voltage drop that the virtual impedance should produce. The controller reference voltage is obtained. U r ; Control module 370 is used to set the controller reference voltage U rA As input to the dual closed-loop control loop based on a fractional-order controller, the fractional-order single-phase inverter is controlled to operate.

[0070] The parallel circulating current suppression device for a fractional-order single-phase inverter provided in this embodiment of the invention can execute the parallel circulating current suppression method for a fractional-order single-phase inverter provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the execution method. The similarities can be referred to the description above.

[0071] Example 4 This embodiment provides a parallel system of a fractional-order single-phase inverter. The parallel system of the fractional-order single-phase inverter includes a controller. The controller can execute the parallel circulating current suppression method of the fractional-order single-phase inverter provided in any of the above embodiments. Therefore, it can have the corresponding structure and features of the parallel circulating current suppression method of the fractional-order single-phase inverter provided in the embodiments of the present invention, and can achieve the beneficial effects of the parallel circulating current suppression method of the fractional-order single-phase inverter provided in the embodiments of the present invention. The similarities can be referred to the description above.

[0072] Example 5 Based on the same concept, embodiments of the present invention also provide a computer-readable storage medium storing computer instructions for causing a processor to execute and implement the parallel circulating current suppression method for a fractional-order single-phase inverter provided in any of the above embodiments.

[0073] In the context of this invention, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0074] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for suppressing parallel circulating current in a fractional-order single-phase inverter, characterized in that, include: A mathematical model of a fractional-order single-phase inverter is established; the mathematical model includes fractional-order inductors and fractional-order capacitors. Based on the mathematical model, a dual closed-loop control loop based on a fractional-order controller is constructed, and the output voltage of the parallel fractional-order single-phase inverter is controlled. and output current i 0 Perform tracking and control; The initial reference voltage is calculated using droop control. U r0 ; Based on the droop coefficient of the fractional-order single-phase inverter and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ; Based on the adaptive virtual inductor of the fractional-order single-phase inverter and adaptive virtual resistance Calculate the voltage drop that the adaptive virtual impedance should produce. ; According to the initial reference voltage U r0 and the voltage drop that the virtual impedance should produce. The controller reference voltage is obtained. U r ; The controller reference voltage U r This serves as the input to the dual closed-loop control loop based on the fractional-order controller to control the operation of the fractional-order single-phase inverter.

2. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 1, characterized in that, Establish a mathematical model for a fractional-order single-phase inverter, including: Based on Kirchhoff's laws, a circuit topology analysis is performed on the parallel system of fractional single-phase inverters, which includes fractional inductors and fractional capacitors, to determine the state equations of the fractional inductors and fractional capacitors in a single fractional single-phase inverter. Based on the output voltage of the fractional-order single-phase inverter The two-phase stationary coordinate system is obtained. , The mathematical expression of the component in the time domain; Will , The components are transformed by Park to obtain the state equations of the fractional inductor and the fractional capacitor on the synchronously rotating coordinate axis.

3. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 1, characterized in that, The initial reference voltage is calculated using droop control. U r0 ,include: Based on the output voltage of the fractional-order single-phase inverter Output current i 0 Rated active power and rated reactive power The active power deviation and reactive power deviation are obtained. The active power deviation is added to the given angular frequency through the active power-frequency droop coefficient m. The angular frequency setting value is obtained above. The reactive power deviation is then added to the given voltage amplitude through a reactive power-voltage droop coefficient n. The voltage amplitude setpoint is obtained. ; According to the angular frequency setting value and the voltage amplitude setting value Determine the initial reference voltage U r0 .

4. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 3, characterized in that, Based on the output voltage of the fractional-order single-phase inverter Output current i 0 Rated active power and rated reactive power The active power deviation and reactive power deviation are obtained, including: Based on the output voltage of the fractional-order single-phase inverter and output current i 0 The output voltage signal in the synchronous rotating coordinate system is obtained. , and output current signal , ; Based on the output voltage signal in the synchronous rotating coordinate system , and output current signal , The active power is obtained through formula (1). P and reactive power Q Formula (1) is as follows: ; Rated active power With the active power P The difference is used to obtain the active power deviation, and the rated reactive power is then calculated. With the reactive power Q The reactive power deviation is obtained by subtracting the reactive power.

5. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 1, characterized in that, Based on the droop coefficient of the fractional-order single-phase inverter and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ,include: Based on the droop coefficient of the i-th fractional-order single-phase inverter and reactive power The virtual impedance correction term is obtained. ; Based on the virtual impedance correction term The adaptive virtual inductance of the i-th fractional single-phase inverter is obtained through formula (2). and adaptive virtual resistance Formula (2) is as follows: ； in, The base value of the virtual inductance designed to protect the circuit impedance from inductive behavior. The base value of the virtual resistor is designed to protect the circuit impedance from being inductive. It is the adaptive inductor for adjusting the i-th fractional-order single-phase inverter. It is the proportional gain of the adaptive resistor of the i-th fractional-order single-phase inverter.

6. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 5, characterized in that, Based on the droop coefficient of the i-th fractional-order single-phase inverter and reactive power The virtual impedance correction term is obtained. ,include: Based on the droop coefficient of the i-th fractional-order single-phase inverter and reactive power The product of, and the droop coefficient of the j-th fractional-order single-phase inverter. and reactive power The product of is calculated to obtain ;in, It is the control gain of the i-th fractional-order single-phase inverter; e qi It is the reactive power distribution error of the i-th fractional-order single-phase inverter; ; based on After passing through a fractional-order proportional-integral controller, the virtual impedance correction term is obtained through formula (3). Formula (3) is as follows: ； It is the proportional control coefficient of the i-th fractional-order single-phase inverter. It is the integral control coefficient of the i-th fractional-order single-phase inverter. For fractional order, s It is a complex frequency.

7. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 1, characterized in that, Based on the adaptive virtual inductor of the fractional-order single-phase inverter and adaptive virtual resistance Calculate the voltage drop that should be generated by the virtual impedance. ,include: Based on the adaptive virtual inductor of the fractional-order single-phase inverter and adaptive virtual resistance The voltage drop that the virtual impedance should produce is calculated using formula (3). Formula (4) is as follows: ;in, Let be the output current of the i-th fractional-order single-phase inverter.

8. The parallel circulating current suppression method for a fractional-order single-phase inverter according to claim 1, characterized in that, Based on the mathematical model, a dual closed-loop control loop based on a fractional-order controller is constructed, including: A current control loop employing fractional-order current loop control is constructed; the transfer function of the current control loop is as follows: ;in, This is the proportionality coefficient; A voltage control loop employing fractional-order current loop control is constructed; the transfer function of the voltage control loop is as follows: ;in, This is the proportionality coefficient. The integral coefficient is... For the fractional order of the voltage controller, s It is a complex frequency.

9. A parallel circulating current suppression device for a fractional-order single-phase inverter, characterized in that, include: The mathematical model building module is used to build a mathematical model of a fractional-order single-phase inverter; the mathematical model includes fractional-order inductors and fractional-order capacitors. The voltage control module is used to construct a dual closed-loop control loop based on the mathematical model and a fractional-order controller, and to control the output voltage of the parallel fractional-order single-phase inverters. and output current i 0 Perform tracking and control; The initial reference voltage calculation module is used to calculate the initial reference voltage through droop control. U r0 ; An adaptive virtual resistance calculation module is used to calculate the droop coefficient based on the fractional-order single-phase inverter. and reactive power Calculate the adaptive virtual inductance of the fractional-order single-phase inverter. and adaptive virtual resistance ; The voltage drop calculation module is used to calculate the adaptive virtual inductance based on the fractional-order single-phase inverter. and adaptive virtual resistance Calculate the voltage drop that the adaptive virtual impedance should produce. ; The controller reference voltage calculation module is used to calculate the reference voltage based on the initial reference voltage. U r0 and the voltage drop that the virtual impedance should produce. The controller reference voltage is obtained. U r ; The control module is used to set the controller reference voltage. U rA As input to the dual closed-loop control loop based on a fractional-order controller, the fractional-order single-phase inverter is controlled to operate.

10. A parallel system of fractional-order single-phase inverters, characterized in that, include: Controller; The controller is capable of executing the parallel circulating current suppression method for the fractional-order single-phase inverter as described in any one of claims 1-8.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed by a processor, implement the parallel circulating current suppression method for the fractional-order single-phase inverter as described in any one of claims 1-8.

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