Research On Stabilizing Technology Of Power Fluctuations For Micro Grid

With the development of social economy, the aggravation of the environmental pollution and the shortage of traditional energy and people’s growing demand for renewable energy, distributed generation technology has developed rapidly. But distributed generation is hard to access to the grid and uncontrollable, in this context,the micro grid emerged as the important way to solve the problem of the use of renewable energy. In the inverter parallel control system, the traditional droop control is usually adopted to distribute the load of the system, but because of the influence of the line impedance and the local load fluctuation, this method has the problem of uneven power distribution, and even cause the system to lose stability. With the continuous improvement of the reliability and power quality requirements of the user, the problem is to be solved urgently.This paper introduces the basic theory of two kinds of traditional droop control of P-V and P-f, and analyzes the stability, according to the topology and mathematical model of the traditional P-V droop control, a simulation model based on MATLAB/Simulink is established, and this paper also makes simulation experiments of this droop control strategy and analyzes their shortcomings. In order to solve the problem of power sharing and power supply quality of the system, the traditional droop control strategy for micro grid inverter is improved. Firstly, the concept of virtual impedance is introduced and a double loop control strategy of voltage and current in parallel inverter is presented. Secondly, based on the virtual impedance control strategy, a new type of droop control relationship is formed when the system load changes. A new type of sag control relationship is formed, and the slope of the droop control curve is changed with the output power of the micro power. In order to solve the problem of the power allocation in line impedance imbalance, the two time frequency modulation characteristics of traditional generator are integrated into the control strategy of inverter droop control.Through simulation experiments, the improved control algorithm can effectively reduce the system voltage deviation, and enhance the stability of the system, which has good feasibility.