Enhancing Small Signal Stability and Reactive Power-sharing Accuracy in Autonomous Microgrids by a New Decentralized Reactive Power Controller

Load sharing without communication between voltage source converters is most important for reliable operation of microgrids. The common approach to achieve this is using the conventional droop technique. Although this method shares a common active load, reactive power sharing is strongly affected by system parameters. In addition, there is an inherent trade-off between the reactive power-sharing accuracy, voltage regulation, and small signal stability margin. This article presents a novel decentralized reactive power controller for parallel operation of voltage source converters in an autonomous microgrid, which leads to the proper reactive power sharing, voltage regulation, and small signal stability margin in microgrids. The proposed methodology and other reactive power-sharing controllers are simulated in IEEE 37-bus test system, and the multi-objective optimization method is used to optimum tuning of each controller and comparison against each other. Simulation results show better performance of the proposed technique in comparison to other reactive power controllers. Furthermore, since the frequency and magnitude of voltage source converters is changed when the demand is altered in the droop method, the conventional load flow cannot be employed to calculate the operation point; a novel method to calculate the operation point in a voltage source converter based microgrid is proposed in this article.