A coordinated control method for leveling output power fluctuations of multiple PV systems

A Photovoltaic (PV) system’s power output fluctuates with the change of weather conditions. Frequency deviations, tie line voltage fluctuations etc. are caused by fluctuating PV power when large PV power from several PV systems is penetrated in the utility. In this paper, to overcome these problems, a simple coordinated control method for leveling the fluctuations of combined PV power from multiple PV systems is proposed. Here, output power command is generated in two steps: central and local. Fuzzy control is used to generate the central leveling output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is maintained between central power command and local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV system’s power output. Simulation results show that the proposed method is effective for leveling output power fluctuations and feasible to reduce the frequency deviations of the power utility.