Stability analysis method, device and system for grid-connected voltage source converter system considering phase-locked loop effect

Abstract

The invention discloses a voltage source converter grid-connected system stability analysis method considering the influence of a phase locked loop, The device and the system comprise: acquiring smalldisturbance state equations of an electric main loop unit of an equivalent power network and a grid-connected converter, and small disturbance state equations of a current inner loop, a feedforward link and a converter pulse width modulation link in the control unit; Based on the relationship between the variable increment of synchronous coordinate system of control unit and the variable increment of corresponding actual synchronous coordinate system caused by phase-locked loop detection error under small disturbance, the specific variable relation involving shaft system transformation is obtained. Obtaining a small disturbance state equation of a phase-locked loop in the control unit; Finally, the stability analysis of the grid-connected VSC system is completed by simultaneously establishing the above state equations, substituting the relevant parameters and solving the eigenvalues of the system. The invention can simply and efficiently judge the stability and oscillation characteristics of the grid-connected system of the voltage source converter.

Description

technical field [0001] The invention specifically relates to a method, device and system for analyzing the stability of a grid-connected system of a voltage source converter considering the influence of a phase-locked loop. Background technique [0002] my country's wind energy resources and loads are distributed inversely. With the increase in the proportion of power electronic devices and renewable energy connected to the grid, the unique multi-scale control mechanism and low-inertia broadband response characteristics of power electronic conversion technology have significantly changed the dynamic characteristics of the power system. Large-scale new energy is connected to the power grid through long-distance lines, or is transmitted over long distances through UHV DC, which weakens its connection with the AC power grid. Under weak connection conditions, the fast feedback control of the converter and improper control links and parameter settings may cause it to exhibit nega...

AI Technical Summary

Problems solved by technology

Under weak connection conditions, the fast feedback control of the converter and improper control links and parameter settings may cause it to exhibit negative resistance characteristics to the outside, and changes in the dynamic characteristics of the voltage source converter system may cause system oscillation problems, thereby threatening new Safe and stable operation of energy grid connection and direct current transmission system

In July 2015, a large-scale power oscillation accident occurred in the Hami area of ​​Xinjiang, my country. The accident caused the torsional vibration protection of three thermal power units in a thermal power plant 300km away from the wind farm to operate one after another, resulting in a power loss of 1280MW

At present, most of the analysis methods for the stability problems brought about by the power electronics of the power system follow the traditional electromagnetic transient simulation, eigenvalue analysis or impedance analysis, but these methods cannot comprehensively and accurately analyze the voltage source variation. The problem of the stability of the connection between the converter and the weak grid

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