Real-Time Validation of Power Control Using NSC Based Electric Spring in an Isolated Microgrid

In this work, a nine-switch converter-based electric spring topology has been proposed for the power control of a microgrid system. Generally, the control algorithms which are used for the control of isolated systems are based upon the ‘generation following load’ strategy, where the generation is varied according to the load demand. But in the case of the electric spring, the control algorithm is modified to a ‘load following generation’ strategy, where the load is adjusted according to the generation. Mostly in this article, emphasis is given to varying the load power according to the instantaneous power generation in the system so that the system voltage and frequency can be kept constant. To achieve that, the loads are first segregated into two types i.e., the critical load which is voltage sensitive, and the non-critical load which is voltage insensitive. In the electric spring concept, the voltage of the non-critical load is varied to vary the non-critical load power to keep the critical load voltage constant. Authors have also proposed a nine-switch converter (NSC) that enables the combined operation of series-shunt compensators, where one side of the NSC acts as an Electric spring and the other side acts as a shunt converter to integrate the PV system and controls its power flow. The isolated hybrid microgrid system comprises a 22 kw self-excited induction generator, an 18 Kw Photovoltaic system housing a Battery energy storage system, and loads. The entire system is simulated and modeled using Matlab/Simulink 2018(a) and verified using OPAL-RT 4510.