A grid-connected system short circuit ratio measurement method and device based on fundamental wave impedance identification

Abstract

The invention discloses a grid-connected system short circuit ratio measurement method and device based on fundamental wave impedance identification. The grid-connected system short-circuit ratio measuring device based on fundamental wave impedance identification comprises a master grid-connected inverter, a short-circuit ratio calculating unit, a slave grid-connected inverter and a weak power grid. Specific operation process of the experimental device for measuring the short circuit ratio of the grid-connected system is as follows: the disturbance injection unit injects disturbance signals into the grid-connected inverter, current response signals and voltage response signals of a common coupling point PCC are collected through the grid-connected current sensor Hig and the grid-connectedvoltage sensor Hug respectively, fundamental wave impedance is obtained through the fundamental wave impedance identification unit, and then the short-circuit ratio of the system is obtained through calculation. The experimental device can accurately and reliably calculate the short circuit ratio of the grid-connected system, so that the experimental device is applied to stability judgment and self-adaptive control of the grid-connected system, and the stability of the grid-connected system is improved.

Description

technical field [0001] The invention belongs to the field of power quality analysis and control, and in particular relates to a method and device for measuring the short-circuit ratio of a grid-connected system based on fundamental wave impedance identification. technical background [0002] With the continuous consumption of fossil energy and the increasing environmental crisis, the proportion of new energy sources such as photovoltaics and wind power in the power structure is increasing. It is inevitable that multiple grid-connected inverters will be connected to the same AC grid. The energy source and the AC grid together form a multi-inverter grid-connected system. [0003] When the number of grid-connected inverters in the multi-connected inverter grid-connected system continues to increase and the capacity increases, the supporting capacity of the AC power grid will weaken, resulting in intensified coupling between equipment and equipment, and between equipment and the...

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Problems solved by technology

[0010] 1. At present, the impedance stability criterion is usually used to analyze the stability of the system. It is necessary to measure the broadband impedance, which takes a long time. The short-circuit ratio is an important factor to measure the stability of the grid connection. There are few existing short-circuit ratio measurement schemes. To better study the stability of the grid-connected system, it is necessary to study the short-circuit ratio measurement scheme;

[0011] 2. Most of the existing short-circuit ratio measurement schemes are calculated from the perspective of the grid-connected system, based on the known power electronic equipment capacity and the short-circuit capacity of the grid, without considering how the grid-connected inverter unit in the system measures the power of the system it is in. Short circuit ratio;

[0012] 3. Under actual working conditions, the grid impedance changes with the operating time and operating status, and the grid impedance change will have an impact on the short-circuit ratio measurement. The existing scheme lacks measures to reduce its impact

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