Grid-connected stability control method of multi-inverter system based on power detection under weak grid

Abstract

The invention discloses a multi-inverter system grid connection stability control method based on power detection under a weak power grid. In order to solve the stability problem of multi-inverter grid connection under a weak power grid, the multi-inverter system grid connection stability control method based on power detection under weak power grid is provided. According to the method, the output active power of each grid connected inverter is detected, the inverters, of which the ratio of output active power to the rated active power is smaller than a set boundary value, in a multi-inverter system are obtained, and the proportion and integral control parameter of the current regulator of the inverters are reduced, so that the grid connection stability of the entire multi-inverter system is improved. The implementation is easy, the stability margin of the multi-inverter system under the weak power grid is greatly increased, and the power grid adaptability of the multi-inverter system is improved.

Description

technical field [0001] The invention relates to a control method for grid connection of a multi-inverter system, in particular to a power detection-based grid-connected stability control method for a multi-inverter system in a weak grid. Background technique [0002] With the rapid development of distributed power generation systems, grid-connected inverters are widely used. Due to the existence of long-distance transmission lines and a large number of transformer devices in remote distributed power generation systems, the grid presents a non-negligible equivalent impedance, which makes the grid present a weak grid characteristic. At this time, a dynamic interconnection system will be formed between the multi-inverter system and the grid, and the grid impedance of the system at its point of common coupling (PCC) will lead to the stability of the grid-connected multi-inverter system The performance drops, causing the output grid-connected current to resonate. [0003] At pr...

AI Technical Summary

Problems solved by technology

However, both documents consider the problem of stability degradation caused by the LCL output filter of the multi-inverter system itself, and do not involve the multi-inverter system caused by the presence of grid impedance when the multi-inverter system is connected to a weak grid. system resonance, and because the schemes proposed in the two literatures require additional resonance suppression devices, there are problems of high cost and large space occupation

[0006] 3) Chinese patent document CN 106026194 A published on October 12, 2016 "Methods for Improving the Robustness of Grid-connected Systems with Multi-Inverter Parallel Grid-connected Systems" is based on a passive network method, that is, switching capacitors method and parallel capacitor-resistance method to improve the robustness of the grid-connected inverter to the grid impedance, however, the scheme proposed in this paper needs to add additional passive devices such as capacitors and resistors, which also has the problems of high cost and large space occupation , and also introduces unnecessary loss

[0007] 4) Chinese patent document CN 105207219 A published on December 30, 2015 "Multiple Resonance Suppression Method for Multiple Inverters Connected to Weak Power Grid in Parallel", is an active trap filter with capacitor voltage feedback to realize multi-inverter The suppression of the resonance peak of the inverter system under the weak power grid, but this paper only considers the suppression of the resonance of the current control loop of a single inverter, but it cannot guarantee that the resonance of the multi-inverter system is suppressed, that is, it does not consider the proposed Can the scheme suppress the resonance problem caused by the weak grid in the entire multi-inverter system; and the scheme proposed in this paper needs to add a corresponding control algorithm for each inverter, which increases the complexity of the multi-inverter control system

[0009] (1) Aiming at the multi-inverter system resonance problem under the condition of weak power grid, the existing literature uses methods such as installing a resonance suppression device in the system or connecting passive devices in series to suppress the resonance of the multi-inverter system, which increases the system The cost and volume, and increase the loss of the system;

[0010] (2) The existing literature focuses on the active damping suppression method of the multi-inverter system under the weak grid, only considering the method of suppressing the resonance of each inverter to achieve the purpose of system resonance suppression, which cannot guarantee the multi-inverter The suppression of resonance at the system level of the inverter, and the corresponding control algorithm needs to be added to each inverter, which increases the complexity of the multi-inverter control system;

[0011] (3) None of the existing literature involves detecting the output active power of each grid-connected inverter to obtain the inverse method that the ratio of the output active power to the rated active power of the inverter in the multi-inverter grid-connected system is less than the set boundary value. Inverter, and then reduce the proportional and integral control parameters of the inverter current regulator, thereby improving the grid-connected stability of the multi-inverter system

Images