CN-121710435-B - Virtual impedance control method, device and equipment for grid-formed inverter

CN121710435BCN 121710435 BCN121710435 BCN 121710435BCN-121710435-B

Abstract

The invention discloses a method, a device and equipment for controlling virtual impedance of a grid-formed inverter, wherein the method comprises the steps of obtaining an external voltage signal and an external current signal of an output inductance branch of the grid-formed inverter; the method comprises the steps of obtaining an instantaneous value reference signal of an internal potential of a mesh inverter target through a preset mesh control algorithm without virtual impedance based on an external voltage signal, an external current signal and power reference information of the mesh inverter, obtaining a phase voltage instantaneous value reference signal of an equivalent controlled voltage source at an alternating side of a power module of the mesh inverter through a virtual impedance construction algorithm based on the instantaneous value reference signal of the internal potential of the target, the external voltage signal, the external current signal, a preset virtual impedance parameter and a preset real impedance parameter estimated value, generating a pulse width modulation signal according to the phase voltage instantaneous value reference signal of the equivalent controlled voltage source, and driving the power module of the mesh inverter through the pulse width modulation signal so as to improve virtual impedance control precision.

Inventors

ZHOU HONGLIN
ZHANG CHUAN
YAN ZHIGUO
LIU JINGBO
WANG ZHIMIN

Assignees

东方电气自动控制工程有限公司

Dates

Publication Date: 20260508
Application Date: 20260213

Claims (8)

1. A method for controlling virtual impedance of a grid-tied inverter, comprising: obtaining an external voltage signal and an external current signal of an output inductance branch of the grid-formed inverter; based on the external voltage signal, the external current signal and the power reference information of the grid-formed inverter, obtaining an instantaneous value reference signal of the potential in the grid-formed inverter target through a preset grid-formed control algorithm without virtual impedance; Based on the instantaneous value reference signal of the target internal potential, the external voltage signal, the external current signal, a preset virtual impedance parameter and a preset real impedance parameter estimated value, obtaining a phase voltage instantaneous value reference signal of an equivalent controlled voltage source on the alternating current side of a power module of the grid-built inverter through a virtual impedance construction algorithm; generating a pulse width modulation signal according to the phase voltage instantaneous value reference signal of the equivalent controlled voltage source, and driving a power module of the grid-formed inverter by utilizing the pulse width modulation signal; The virtual impedance construction algorithm is obtained through the following steps: Constructing a physical circuit equation of an inverter output branch comprising the real impedance parameter; Constructing a target equivalent circuit equation comprising the real impedance parameter and the virtual impedance parameter, wherein the internal potential of the target equivalent circuit is an instantaneous value reference signal of the target internal potential; According to the equivalence of the relation between the voltage and the current in the physical circuit equation and the target equivalent circuit equation, the controlled voltage source in the physical circuit equation is equivalently replaced by the internal potential of the target equivalent circuit, and the virtual impedance construction algorithm is obtained; The phase voltage instantaneous value reference signal is obtained by the following formula: ; Wherein, the For the phase voltage instantaneous value reference signal, As a parameter of the virtual inductance, As a parameter of the virtual resistance, As an estimate of the actual inductance parameter, As an estimate of the actual resistance parameter, As a signal of the external current, As a signal of the external voltage, the voltage signal, Is an instantaneous value of the potential in the target.
2. The method for controlling virtual impedance of a mesh inverter according to claim 1, wherein the step of obtaining the external voltage signal and the external current signal of the output inductance branch of the mesh inverter comprises: obtaining an external voltage measured value and an external current measured value of an output inductance branch of the grid-formed inverter; and carrying out signal conditioning and filtering processing on the external voltage measured value and the external current measured value to obtain the external voltage signal and the external current signal.
3. The method for controlling virtual impedance of a grid-formed inverter according to claim 1, wherein the alternating current side of the power module of the grid-formed inverter is constructed as an equivalent controlled voltage source with a target internal potential, the internal impedance being a series connection of a virtual inductance and a virtual resistance, and an output end of the equivalent controlled voltage source is connected to an output inductance branch; the virtual impedance parameters comprise virtual inductance parameters of the virtual inductor and virtual resistance parameters of the virtual resistor; The real impedance parameter estimation value comprises a real inductance parameter estimation value of all the inductances in the output inductance branch and a real resistance parameter estimation value of all the resistances in the output inductance branch.
4. A method of controlling virtual impedance of a grid-tied inverter according to any one of claims 1 to 3, wherein the virtual impedance parameter comprises a positive value, a zero value or a negative value, and wherein the virtual impedance parameter is configured to increase the total impedance of the output branch of the grid-tied inverter when the virtual impedance parameter is positive, and wherein the virtual impedance parameter is configured to decrease the total impedance of the output branch of the grid-tied inverter when the virtual impedance parameter is negative.
5. The method of controlling virtual impedance of a grid-tied inverter according to claim 1, wherein the grid-tied inverter comprises any one of a single-phase current transformer, a three-phase current transformer, and a multi-phase current transformer.
6. A network inverter virtual impedance control device, comprising: The acquisition unit is used for acquiring an external voltage signal and an external current signal of an output inductance branch of the grid-type inverter; the network formation control unit is used for obtaining an instantaneous value reference signal of the internal potential of the network formation inverter target through a preset network formation control algorithm without virtual impedance based on the external voltage signal, the external current signal and the power reference information of the network formation inverter; The virtual impedance unit is used for obtaining a phase voltage instantaneous value reference signal of an equivalent controlled voltage source at the alternating-current side of a power module of the grid-built inverter through a virtual impedance construction algorithm based on the instantaneous value reference signal of the target internal potential, the external voltage signal, the external current signal, a preset virtual impedance parameter and a preset real impedance parameter estimated value; The driving control unit is used for generating a pulse width modulation signal according to the phase voltage instantaneous value reference signal of the equivalent controlled voltage source and driving a power module of the grid-formed inverter by utilizing the pulse width modulation signal; a virtual impedance construction module for: Constructing a physical circuit equation of an inverter output branch comprising the real impedance parameter; Constructing a target equivalent circuit equation comprising the real impedance parameter and the virtual impedance parameter, wherein the internal potential of the target equivalent circuit is an instantaneous value reference signal of the target internal potential; According to the equivalence of the relation between the voltage and the current in the physical circuit equation and the target equivalent circuit equation, the controlled voltage source in the physical circuit equation is equivalently replaced by the internal potential of the target equivalent circuit, and the virtual impedance construction algorithm is obtained; The phase voltage instantaneous value reference signal is obtained by the following formula: ; Wherein, the For the phase voltage instantaneous value reference signal, As a parameter of the virtual inductance, As a parameter of the virtual resistance, As an estimate of the actual inductance parameter, As an estimate of the actual resistance parameter, As a signal of the external current, As a signal of the external voltage, the voltage signal, Is an instantaneous value of the potential in the target.
7. The grid-tied inverter virtual impedance control device of claim 6 wherein said acquisition unit comprises a current acquisition circuit, a voltage acquisition circuit, a filter circuit, and a signal conditioning circuit.
8. An electronic device, comprising: A processor; a memory for storing the processor-executable instructions; wherein the processor is configured to execute to implement a method of controlling virtual impedance of a grid-tied inverter as claimed in any one of claims 1 to 5.

Description

Virtual impedance control method, device and equipment for grid-formed inverter Technical Field The present invention relates to the field of inverter control technologies, and in particular, to a method, an apparatus, and a device for controlling virtual impedance of a grid-tied inverter. Background Along with the continuous improvement of the power generation proportion of new energy, the rapid development of a new energy system causes a series of technical challenges, the system stability is reduced due to the weak grid access of a large new energy base in a remote area, the support capacity of a power transmission end and a power receiving end of a remote and large-capacity power transmission project is higher, the traditional power source is moved outwards due to the fact that a large number of distributed power sources are accessed in a load center, the power grid structure presents a hollow trend, and the dynamic support capacity is obviously weakened. Under the background, the grid-built inverter is a key technical path for solving the problems by means of the key advantages of autonomously establishing voltage, providing inertia and short-circuit capacity support and enhancing system stability, and is widely focused by academia and industry in aspects of theoretical research, control strategies, engineering application and the like. The grid-built inverter usually operates in a virtual synchronous machine mode, a voltage source operation mode is maintained in the steady state and transient state processes of the grid-built inverter to support a power grid, the internal impedance of the grid-built inverter mainly depends on the output reactance of a power component of the converter and the internal impedance of the grid-connected boost transformer, once hardware design is shaped, the internal impedance is fixed, and flexible adjustment requirements in practical application are difficult to meet. In an actual scene, when the island operates, the internal impedance needs to be reduced to strengthen the networking capability, when the frequency of the power system oscillates, the internal impedance needs to be adjusted to inhibit oscillation, and when the fault passes through, the internal impedance needs to be increased to limit the short-circuit current protection equipment, so that flexible adjustment of the internal impedance becomes an important requirement. In the prior art, for example, chinese patent CN117856188A, CN117117884 proposes that the internal impedance of a grid-built inverter can be adjusted by means of virtual impedance, which is mainly achieved by multiplying the feedback current by a steady-state virtual impedance matrix under a rotating coordinate system to obtain a voltage set on the virtual impedance, and then superimposing it on the original internal potential set. However, this method uses fundamental frequency and steady-state virtual impedance matrix to replace real virtual impedance, so that accuracy can be maintained only for fundamental component at rated frequency, but accuracy can not be ensured for other frequency components, which results in that the characteristics of virtual impedance can not be accurately simulated in fast dynamic process (such as fault crossing). Another solution directly constructs virtual impedance by using current differential (or equivalent differential) expression, but this method is difficult to be practical in engineering implementation due to the introduction of a large amount of high-frequency noise in the differential (or equivalent differential) link. In addition, as in the mode of CN116015081B, the state observer is used in combination with PI control to replace the differential link so as to maintain the high-frequency characteristic of the virtual impedance, but a more complex state observer design and an internal potential PI controller design are introduced in the design process, so that the parameters to be adjusted become more, and the complexity of the design and the difficulty of implementation are increased. Therefore, the existing virtual impedance control scheme has the defects of limited adaptive frequency range, easiness in introducing high-frequency noise, complex structure, difficulty in realization and the like. In view of this, the present application has been proposed. Disclosure of Invention The embodiment of the application solves the technical problem of inaccurate virtual impedance control of the grid-formed inverter in the prior art by providing the virtual impedance control method, the device and the equipment of the grid-formed inverter, and achieves the technical effect of the virtual impedance control accuracy of the grid-formed inverter. In a first aspect, the present application provides a method for controlling virtual impedance of a grid-tied inverter, including: obtaining an external voltage signal and an external current signal of an output inductance branch of the grid-formed inverter; Based on the ex