Micro-grid stabilizer design using sliding mode controller

Future of the network stability is endangered by increasing the number of Distributed Generation (DG) and Renewable Energy Source (RES) units. The idea of the Virtual Synchronous Machine (VSM) has been raised to control the power electronic-based DG/RES converters in order to have better integration with the grid. This paper introduces a new stabilizer design for VSM-based converters to guarantee the stability of the micro-grid (MG). In this regard, the Sliding Mode Control (SMC) theory, which is robust against the disturbances and uncertainties, is employed to cope with the intermittent and nonlinear nature of DGs. The mutual operation of the proposed inverter and MG stabilizer has the following advantages: (1) It provides a seamless and robust transition from the grid-connected to the islanded mode. (2) It is universal, sharing the real and reactive power during islanded mode and acting as a grid-supporting inverter in the grid-connected mode. (3) It mimics the behavior of the conventional synchronous generator resulting in better integration of DGs into the grid. (4) It can be used both in the voltage-controlled and the current-controlled Voltage Source Converters (VSC). (5) It obviates the need for the communication links, Phase Locked Loop (PLL) and islanding detection process. The mathematical model of the whole system has been investigated. The simulation results, conducted in the PSCAD/EMTDC environment, confirm the effectiveness of the proposed controller.