Method for evaluating stability of multi-inverter grid-connected system in two dimensions

Abstract

The invention discloses a method for evaluating the stability of a multi-inverter grid-connected system in two dimensions, which comprises the steps of (1) loading parameters of the grid-connected system for system modeling; (2) establishing a full admittance form equivalent circuit of the grid-connected system; (3) deriving a grid-connected current expression of inverters in the grid-connected system and a transfer function of global admittance in s domain; (4) dividing the global admittance into a real part dimension and an imaginary part dimension, and analyzing the stability of the grid-connected system in the two dimensions. According to the stability evaluating method provided by the invention, whether the real part is greater than 0 or not at the part where the virtual part of the global admittance is 0 is analyzed, thereby not only being capable of clearly judging the stability of the grid-connected system, but also being capable of obtaining accurate resonance point information, acquiring essential factors affecting the stability of the parallel operation system, indicating the direction of resonance suppression, and having excellent feasibility and practical values.

Description

technical field [0001] The invention relates to an inverter grid-connected system, in particular to a method for evaluating the stability of a multi-inverter grid-connected system in two dimensions. Background technique [0002] At present, distributed power generation is the main way to develop and utilize renewable energy on a large scale. Renewable energy usually cannot directly meet the grid-connected power quality requirements. As an energy conversion interface, the grid-connected inverter is responsible for converting the energy output by renewable energy into AC power acceptable to the grid. With the development of distributed power generation, the scale of renewable energy to be consumed and utilized is increasing, and the capacity of inverters required is also increasing; limited by factors such as power device capacity and switching frequency, large-scale photovoltaic The grid-connected converters of power stations or wind farms often adopt the idea of ​​modular p...

AI Technical Summary

Problems solved by technology

[0003] The design idea of ​​multi-converter parallel connection has promoted the rapid development of distributed power generation technology, but it has also created new stability problems: each grid-connected inverter is stable when running independently, and resonance occurs when running in parallel, and the grid-connected current is severely distorted and divergent

However, this method has some limitations, such as: it is difficult to obtain the exact frequency of the resonance point, it is impossible to reveal the nature of the resonance instability of the system, and it is difficult to analyze the interaction phenomenon

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