Development of Optimal PI Controllers for a Grid-Tied Photovoltaic Inverter

Power electronic interfaces (PEIs) play a significant role in integrating distributed energy sources (DER) into the electric power grid. In fact, as solution to grid integration of photovoltaic arrays, voltage source inverters (VSI) are widely utilized as the PEI entity. The VSI is controlled by a set of proportional-integral (PI) controllers, which require optimal tuning in order to guarantee smooth operation of PV-system especially when exposed to severe meteorological conditions e.g. sudden cloud covers. Hence, developing a practical robust tuning method for optimizing the PV-inverter set of controllers i.e. the DC-link voltage controller, the reactive power controller, and the decoupled current controller becomes of paramount importance. This paper employs a particle swarm optimization (PSO) approach to optimally tune these controllers based on online operation performance of the PV-system. The PSO approach is integrated into a real-time digital simulator (RTDS) for searching the inverter PI controllers parameters. The simulation results conclude the superiority of this approach in comparison to conventional inverter PI controller tuning methods; enhancing the PV-system transient and steady-state step-response over a wide operating range of irradiance.