Coordinated Control Strategy for Power Quality in Microgrids With Multiple Parallel Inverters

Abstract

To address the lack of coordination among frequency restoration, voltage restoration, reactive power sharing, and voltage unbalance compensation in islanded microgrids with multiple distributed generators (DGs) under unbalanced load conditions, this paper proposes a coordinated control strategy for DGs and a static var generator (SVG) based on a networked hierarchical control architecture. The proposed control framework consists of a local control layer and a distributed secondary control layer. In the local control layer, droop control, dual-loop voltage/current control, and selective virtual impedance are employed to ensure stable system operation and proper reactive power sharing. In the distributed secondary control layer, an event-triggered consensus-based control strategy is developed to achieve frequency restoration, voltage restoration, and coordinated reactive power regulation while reducing communication burden without compromising control performance. Furthermore, a coordinated DG–SVG compensation mechanism is proposed to dynamically allocate voltage unbalance and reactive power compensation according to the compensation capability of the DGs. When the compensation capability of the DGs becomes insufficient, the SVG is activated to provide supporting compensation, thereby avoiding excessive reliance on a single compensation device and improving the overall voltage quality and compensation capability of the microgrid. The simulation results show that the proposed control strategy can achieve the rapid recovery of frequency and voltage, and the effective suppression of voltage unbalance. Compared to the time-triggered control strategy, the communication times can be reduced by 77%, and the response speed in reactive power sharing can be reduced by 1.3 s. It can still maintain good performance in a nonideal communication environment.