Analysis of microgrid power frequency oscillation and damping joint control strategy
To address the problem of power and frequency oscillation during parallel operation of multiple virtual synchronous generators(n-VSGs)in microgrids,a combined transient self-damping and mutual damping control strategy is proposed.In this paper,firstly,the single VSG mathematical model is investigated,and it is deduced that the low damping ratio is the main factor of self-oscillation;secondly,the dual VSG mathematical model is investigated,and it is deduced that the inter-oscillatory circulating power is the main factor of the inter-oscillation;the self-damping control strategy is proposed to increase the equivalent damping in the transient case,and to make up for the under-damping in the system due to the coupling of the sag coefficients and damping coefficients;and the mutual-damping control strategy is proposed to utilize the virtual impedance characteristics to reduce the multi-machine power frequency oscillation to achieve mutual damping;finally,the damping joint control strategy is proposed to improve the system self-damping through the design of power feed-forward,and frequency feed-forward is designed to adjust the mutual damping of the system,the joint control of the multi-VSG frequency-power is realized without affecting the steady state power allocation at the same time.The proposed control strategy is verified by constructing a 4VSG simulation model in MATLAB/Simulink.Compared with the traditional sagging VSG control,the damping joint control strategy is able to suppress the system power frequency oscillation in a cooperative manner,and shorten the power-frequency transient performance indexes while guaranteeing the stability of the system power-frequency,with the frequency transient time reduced from 3.5 s to 0.7 s,and power overshooting amount suppressed from 11.11％to 3.70％.
multiple virtual synchronous generatorpower frequency oscillationself-damping controlmutual damping controldamping joint control
万方数据
维普
