Reference model based power smoothening for hybrid PV parks

More and more distributed generation units are connected to the grid by DC-AC inverters as replacement of conventional generators. The inverters are usually controlled by Phase Lock Loop to sync its output frequency with the grid frequency. As a result, the grid inertia that used to be provided by conventional generators decreases and the grid becomes more vulnerable to disturbances. Prior articles have proposed several approaches to emulate the inertia characteristics of a synchronous generator by using energy storage systems (ESS) such as batteries. Inverter is controlled in such way that the ESS performs the function of a virtual synchronous generator (VSG). In this paper, a new control method for the ESS that smoothens the active power disturbances of the microgrid is proposed based on the existing VSG topologies. The new control is modeled as a part of the multilevel active power control system of the microgrid. In the examined case the microgrid is comprised of diesel generators, Photovoltaic (PV) generators, loads and proposed battery storage systems. This microgrid is tested for various active power disturbances, and the results show how the control method can enhances the grid stability.