阅读说明：本技术 基于二阶广义积分器的单相逆变器振荡抑制策略和装置 (Single-phase inverter oscillation suppression strategy and device based on second-order generalized integrator ) 是由 黄阮明 朱淼 陈阳 陈哲 侯川川 李灏恩 郭明星 庞爱莉 张梦瑶 赵鹏飞 于 2020-08-05 设计创作，主要内容包括：本发明涉及一种基于二阶广义积分器的单相逆变器振荡抑制策略和装置,所述单相逆变器设有基于二阶广义积分器的锁相环,所述单相逆变器振荡抑制策略为,通过减小所述二阶广义积分器的带宽,对所述单相逆变器进行振荡抑制。与现有技术相比,本发明只改变SOGI的带宽参数,即二阶广义积分器的参数k,即可对并网逆变器的振荡进行抑制,无需调整其他参数,方便可靠,且不影响逆变器的控制特性。(The invention relates to a single-phase inverter oscillation suppression strategy and a single-phase inverter oscillation suppression device based on a second-order generalized integrator, wherein the single-phase inverter is provided with a phase-locked loop based on the second-order generalized integrator, and the single-phase inverter oscillation suppression strategy is that the single-phase inverter is subjected to oscillation suppression by reducing the bandwidth of the second-order generalized integrator. Compared with the prior art, the method can inhibit the oscillation of the grid-connected inverter by only changing the bandwidth parameter of the SOGI, namely the parameter k of the second-order generalized integrator, does not need to adjust other parameters, is convenient and reliable, and does not influence the control characteristic of the inverter.)

1. The single-phase inverter oscillation suppression strategy is characterized in that the single-phase inverter is subjected to oscillation suppression by reducing the bandwidth of the second-order generalized integrator.

2. The second-order generalized integrator-based single-phase inverter oscillation suppression strategy according to claim 1, wherein the transfer function of the second-order generalized integrator is expressed as:

wherein s is Laplace operator, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, ω₁Is the fundamental frequency, and k is the control parameter of the second-order generalized integrator;

the single-phase inverter oscillation suppression strategy is specifically that oscillation suppression is performed on the single-phase inverter by reducing a parameter k of the second-order generalized integrator.

3. The single-phase inverter oscillation suppression strategy based on the second-order generalized integrator as claimed in claim 1, wherein the single-phase inverter oscillation suppression strategy is specifically characterized in that after the single-phase inverter is connected to the grid, the impedance of the single-phase inverter is calculated according to a single-phase inverter impedance model so as to judge the stability of the single-phase inverter, and if the single-phase inverter is in an unstable state, the single-phase inverter is subjected to oscillation suppression by reducing the bandwidth of the second-order generalized integrator.

4. The second-order generalized integrator-based single-phase inverter oscillation suppression strategy according to claim 3, wherein the single-phase inverter is an LCL type single-phase inverter, the LCL type single-phase inverter comprises an LCL filter, and the expression of the impedance model of the single-phase inverter is as follows:

T＝G_X1G_X2

Z_L1＝sL₁

Z_L2＝sL₂

Z_c＝1/sC_f+R_d

in the formula, Z_pImpedance of single-phase inverter, G_SOGI-PLLIs a transfer function of a phase-locked loop based on a second-order generalized integrator, s is a Laplace operator, L₁Is the first inductance, L, of the LCL filter₂Is the second inductance of the LCL filter, C_fIs the capacitance of the LCL filter, R_dIs the resistance of the LCL filter, I_mFor the inverter output current amplitude, K_PWMIs the pulse width modulation factor, H_iAs a current loop transfer function.

5. The second-order generalized integrator-based single-phase inverter oscillation suppression strategy according to claim 4, wherein the expression of the transfer function of the second-order generalized integrator-based phase-locked loop is as follows:

in the formula, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, U₁Is the fundamental frequency f₁Amplitude of the voltage, ω₁At a fundamental angular frequency of and₁＝2πf₁k is a second-order generalized integrator control parameter, H_PLL(s) is the phase-locked loop open loop transfer function.

6. The single-phase inverter oscillation suppression device is characterized by comprising a memory and a processor, wherein the memory stores a computer program, and the processor calls the computer program to execute a single-phase inverter oscillation suppression strategy, wherein the single-phase inverter oscillation suppression strategy is to perform oscillation suppression on the single-phase inverter by reducing the bandwidth of the second-order generalized integrator.

7. The second-order generalized integrator-based single-phase inverter oscillation suppression device according to claim 6, wherein the transfer function of the second-order generalized integrator is expressed as:

wherein s is Laplace operator, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, ω₁Is the fundamental frequency, and k is the control parameter of the second-order generalized integrator;

the single-phase inverter oscillation suppression strategy is specifically that oscillation suppression is performed on the single-phase inverter by reducing a parameter k of the second-order generalized integrator.

8. The single-phase inverter oscillation suppression device based on the second-order generalized integrator according to claim 6, wherein the single-phase inverter oscillation suppression strategy is specifically that after the single-phase inverter is connected to the grid, the impedance of the single-phase inverter is calculated according to a single-phase inverter impedance model to judge the stability of the single-phase inverter, and if the single-phase inverter is in an unstable state, the single-phase inverter is suppressed in oscillation by reducing the bandwidth of the second-order generalized integrator.

9. The oscillation suppression device of a single-phase inverter based on a second-order generalized integrator as claimed in claim 8, wherein the expression of the impedance model of the single-phase inverter is:

Z_L1＝sL₁

Z_L2＝sL₂

Z_c＝1/sC_f+R_d

in the formula, Z_pImpedance of single-phase inverter, G_SOGI-PLLIs a transfer function of a phase-locked loop based on a second-order generalized integrator, s is a Laplace operator, L₁Is the first inductance, L, of the LCL filter₂Is the second inductance of the LCL filter, C_fIs the capacitance of the LCL filter, R_dIs the resistance of the LCL filter, I_mFor the inverter output current amplitude, K_PWMIs the pulse width modulation factor, H_iAs a current loop transfer function.

10. The apparatus according to claim 9, wherein the expression of the transfer function of the second-order generalized integrator-based phase-locked loop is:

in the formula, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, U₁Is the fundamental frequency f₁Amplitude of the voltage, ω₁Is the fundamental frequency, k is the second-order generalized integrator control parameter, H_PLL(s) is the phase-locked loop open loop transfer function.

Technical Field

The invention relates to the field of single-phase inverter oscillation suppression, in particular to a single-phase inverter oscillation suppression strategy and device based on a second-order generalized integrator.

Background

In recent years, with the increasing of the grid-connected capacity of renewable energy, power electronic devices such as Voltage Source Converters (VSCs) are used as connectors between a renewable energy power generation system and a power grid, and interact with a weak power grid in the process of connecting renewable energy to the power grid, so that sub-super-synchronous oscillation is generated, and the stability of the system is reduced.

In actual operation, the output impedance of the inverter is affected by a Phase Locked Loop (PLL). In order to control the power generated by the grid-connected inverter, a phase-locked loop is used to acquire the phase of the grid voltage and generate a synchronous current reference signal. A second order generalized integrator-based phase-locked loop (SOGI-PLL) is common in a single-phase system due to its characteristics of simple structure and high detection accuracy.

The existing research shows that the phase-locked loop has a large influence on the grid-connected stability of the inverter, and the influence depends on the factors such as load conditions, the power factor of the inverter, the parameters of the phase-locked loop and the like. Aiming at unstable phenomena such as subsynchronous oscillation and supersynchronous oscillation in the grid connection process of the inverter, the conventional measures comprise changing the bandwidth of a phase-locked loop, adjusting the parameters of a current loop, reducing the output power of the inverter and the like. However, these methods modify the control structure and the control target of the inverter, and affect the control characteristics of the inverter.

Disclosure of Invention

The invention aims to overcome the defects of the prior art that the control characteristics of an inverter are influenced, and provides a single-phase inverter oscillation suppression strategy and device based on a second-order generalized integrator.

The purpose of the invention can be realized by the following technical scheme:

the single-phase inverter oscillation suppression strategy is characterized in that a second-order generalized integrator is based on, a phase-locked loop based on the second-order generalized integrator is arranged in the single-phase inverter, and the single-phase inverter oscillation suppression strategy is that oscillation suppression is carried out on the single-phase inverter by reducing the bandwidth of the second-order generalized integrator.

Further, the expression of the transfer function of the second-order generalized integrator is:

wherein s is Laplace operator, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, ω₁Is the fundamental frequency, and k is the control parameter of the second-order generalized integrator;

the single-phase inverter oscillation suppression strategy is specifically that oscillation suppression is performed on the single-phase inverter by reducing a parameter k of the second-order generalized integrator.

Further, the single-phase inverter oscillation suppression strategy is specifically that after the single-phase inverter is connected to the grid, the impedance of the single-phase inverter is calculated according to a single-phase inverter impedance model, so that the stability of the single-phase inverter is judged, and if the single-phase inverter is in an unstable state, the single-phase inverter is subjected to oscillation suppression by reducing the bandwidth of the second-order generalized integrator.

Further, the single-phase inverter is an LCL type single-phase inverter, the LCL type single-phase inverter includes an LCL filter, and the expression of the impedance model of the single-phase inverter is:

T＝G_X1G_X2

Z_L1＝sL₁

Z_L2＝sL₂

Z_c＝1/sC_f+R_d

in the formula, Z_pImpedance of single-phase inverter, G_SOGI-PLLIs a transfer function of a phase-locked loop based on a second-order generalized integrator, s is a Laplace operator, L₁Is the first inductance, L, of the LCL filter₂Is the second inductance of the LCL filter, C_fIs the capacitance of the LCL filter, R_dIs the resistance of the LCL filter, I_mFor the inverter output current amplitude, K_PWMIs the pulse width modulation factor, H_iAs a current loop transfer function.

Further, the expression of the transfer function of the second-order generalized integrator-based phase-locked loop is as follows:

in the formula, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, U₁Is the fundamental frequency f₁Amplitude of the voltage, ω₁At a fundamental angular frequency of and₁＝2πf₁k is a second-order generalized integrator control parameter, H_PLL(s) is the phase-locked loop open loop transfer function.

The invention also provides a single-phase inverter oscillation suppression device based on the second-order generalized integrator, wherein the single-phase inverter is provided with a phase-locked loop based on the second-order generalized integrator, the single-phase inverter oscillation suppression device comprises a memory and a processor, the memory stores a computer program, and the processor calls the computer program to execute a single-phase inverter oscillation suppression strategy, wherein the single-phase inverter oscillation suppression strategy is that the single-phase inverter is suppressed in oscillation by reducing the bandwidth of the second-order generalized integrator.

Further, the expression of the transfer function of the second-order generalized integrator is:

wherein s is Laplace operator, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, ω₁Is the fundamental frequency, and k is the control parameter of the second-order generalized integrator;

the single-phase inverter oscillation suppression strategy is specifically that oscillation suppression is performed on the single-phase inverter by reducing a parameter k of the second-order generalized integrator.

Further, the single-phase inverter oscillation suppression strategy is specifically that after the single-phase inverter is connected to the grid, the impedance of the single-phase inverter is calculated according to a single-phase inverter impedance model, so that the stability of the single-phase inverter is judged, and if the single-phase inverter is in an unstable state, the single-phase inverter is subjected to oscillation suppression by reducing the bandwidth of the second-order generalized integrator.

Further, the expression of the impedance model of the single-phase inverter is as follows:

Z_L1＝sL₁

Z_L2＝sL₂

Z_c＝1/sC_f+R_d

in the formula, Z_pImpedance of single-phase inverter, G_SOGI-PLLIs a transfer function of a phase-locked loop based on a second-order generalized integrator, s is a Laplace operator, L₁Is the first inductance, L, of the LCL filter₂Is the second inductance of the LCL filter, C_fIs the capacitance of the LCL filter, R_dIs the resistance of the LCL filter, I_mFor the inverter output current amplitude, K_PWMIs the pulse width modulation factor, H_iAs a current loop transfer function.

Further, the expression of the transfer function of the second-order generalized integrator-based phase-locked loop is as follows:

in the formula, H_α(s) is the α axis component transfer function, H_β(s) is the β axis component transfer function, U₁Is the fundamental frequency f₁Amplitude of the voltage, ω₁Is the fundamental frequency, k is the second-order generalized integrator control parameter, H_PLL(s) is the phase-locked loop open loop transfer function.

Compared with the prior art, the invention has the following advantages:

(1) the Quadrature Signal Generator (QSG) is realized through a second-order generalized integrator, so that the overall performance and the precision of the single-phase-locked loop are improved, the oscillation of the grid-connected inverter can be inhibited only by changing the bandwidth parameter of the SOGI, namely the parameter k of the second-order generalized integrator, and the grid-connected inverter is convenient and reliable without adjusting other parameters; meanwhile, the existing method realizes oscillation suppression by means of adjustment of parameters of a current loop and a phase-locked loop, and the process inevitably changes the original optimal control parameters;

(2) by adopting a method combining impedance analysis and SOGI bandwidth, frequency characteristic modeling of a grid-connected inverter system can be conveniently realized, and the complexity of interactive system stability analysis is effectively simplified;

(3) the harmonic linearization method is adopted to analyze the single-phase inverter, the fundamental component of the output signal of the nonlinear link is used for approximately replacing the actual output under the action of the sine signal, and the nonlinear system can be well described.

Drawings

Fig. 1 is a structural diagram of an LCL type single-phase grid-connected inverter of the present invention;

FIG. 2 is a schematic diagram of the SOGI-PLL structure of the present invention;

FIG. 3 is a block diagram of the SOGI control scheme of the present invention;

FIG. 4 shows H under different k parameters according to the present invention_α(s) bode diagram;

FIG. 5 shows H under different k parameters according to the present invention_β(s) bode diagram;

FIG. 6 is a block diagram of grid-connected inverter control according to the present invention;

FIG. 7 is a simplified diagram of grid-connected inverter control according to the present invention;

FIG. 8 is an equivalent circuit diagram of the LCL type grid-connected inverter of the invention;

FIG. 9 shows the theoretical results and Z of the present invention_P2The simulation result of (2);

FIG. 10 shows Z of the present invention_P1,Z_P2And Z_gAn impedance curve;

fig. 11 is a diagram illustrating an analysis of the oscillation state of the inverter of the present invention, in fig. 11, 11(a) is a waveform of the oscillation of the inverter of the present invention, and 11(b) is a fast fourier analysis of the oscillation current;

fig. 12 is a diagram illustrating steady state analysis of the inverter of the present invention, in fig. 12, 12(a) is a steady state waveform of the inverter of the present invention, and 12(b) is a fast fourier analysis of a steady state current waveform;

fig. 13 is a schematic flow chart of the oscillation suppression strategy of the single-phase inverter according to the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.