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Method for judging small-interference stability of converter grid-connected system under polar coordinates

A technology of converters and polar coordinates, applied in the direction of single-network parallel feeding arrangement, reducing/preventing power oscillation, etc., can solve problems such as unfavorable calculation stability margin, complicated judgment process, etc., and achieve the goal of simplifying small disturbance stability judgment process, the effect of avoiding instability problems

Inactive Publication Date: 2020-05-12
ZHEJIANG UNIV +2
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Problems solved by technology

In the existing impedance analysis method, the impedance matrix of the converter and the power grid is asymmetrical and full, resulting in a closed-loop system formed as a multiple-input multiple-output system, which needs to use the generalized Nyquist criterion to analyze the stability, and the judgment process is complicated And it is not conducive to the calculation of stability margin

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  • Method for judging small-interference stability of converter grid-connected system under polar coordinates
  • Method for judging small-interference stability of converter grid-connected system under polar coordinates
  • Method for judging small-interference stability of converter grid-connected system under polar coordinates

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specific Embodiment

[0057] The specific embodiment that implements according to the complete method of content of the present invention is as follows:

[0058] Established in Matlab / Simulink software such as figure 1The grid-connected model of the converter shown is used for simulation experiments, and the converter controller considers phase-locked loop and current inner loop control. Among them, the control parameters of the converter and the main parameters of the system parameters are shown in Table 1:

[0059] Table 1 Main parameters of photovoltaic inverter

[0060] Line inductance L g / p.u.

0.35 Filter inductance L f / p.u.

0.05 filter capacitor C f / p.u.

0.05 Current inner loop ratio, integral coefficient 0.25、20 Voltage feed-forward filter time constant 0.002

[0061] figure 1 The converter grid-connected system shown is divided into the converter side and the grid side, and the admittance models of the converter and the grid can be es...

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Abstract

The invention discloses a method for judging the small-interference stability of a converter grid-connected system under polar coordinates. The method comprises the steps: acquiring an admittance model of a converter and a power grid under coordinates by linearly processing a dynamic equation of the converter grid-connected system, and then establishing an admittance model of the converter and anadmittance model of the power grid; performing coordinate transformation on the admittance model of the converter and the admittance model of the power grid under the dq coordinates to obtain a converter admittance model and a power grid admittance model under the polar coordinates; obtaining a single-input single-output closed-loop system model and a closed-loop characteristic equation, and performing judging by using a Nyquist curve according to the closed-loop characteristic equation or calculating the stability margin of the system according to the closed-loop characteristic equation to obtain a result whether the current control parameter of the converter can enable the converter to operate stably or not. According to the method, the stability margin of the converter grid-connected system can be effectively calculated, the influence of the control parameters of the converter on the stability of the grid-connected system is judged, and the instability problem caused by improper setting of the control parameters of the converter is avoided.

Description

technical field [0001] The invention relates to a method for judging the small disturbance stability of a converter grid-connected system under polar coordinates, which is used for calculating the stability margin of the converter grid-connected system and analyzing the influence of converter control parameters on the stability. Background technique [0002] The capacity of renewable energy connected to the power system through converters is increasing, the AC system is relatively gradually weakened, and the system stability problem is gradually becoming prominent. Impedance analysis method is a commonly used analysis method to analyze the small disturbance stability of converter grid-connected system. In the existing impedance analysis method, the impedance matrix of the converter and the power grid is asymmetrical and full, resulting in a closed-loop system formed as a multiple-input multiple-output system, which needs to use the generalized Nyquist criterion to analyze th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/38H02J3/24
CPCH02J3/24H02J3/38
Inventor 王冠中辛焕海徐路遥蒙志全董炜朱承治
Owner ZHEJIANG UNIV
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