Dynamic Behavior Improvement of Control System in Inverter-Based Island Microgrid by Adding a Mixed Virtual Impedance Loop to Voltage Control Loop

Subject Areas : International Journal of Smart Electrical Engineering

Saeid Farhang ¹ , Ghazanfar Shahgholian ² , Bahador Fani ³

1 - Najafabad Branch, Islamic Azad University
2 - Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
3 - Najafabad Branch, Islamic Azad University, Najafabad, Iran

Received: 2021-09-01 Accepted : 2021-10-29 Published : 2022-03-01

Keywords: Stability, small signal analysis, Island microgrid, distributed generation sources, frequency and voltage droop strategy, power distribution, transient mode response,

Abstract :

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.