A new method for smoothing output power fluctuations of PV system connected to small power utility

摘要

A Photovoltaic (PV) system’s power output is not constant and fluctuates depending on weather conditions. Fluctuating power causes frequency deviations in the power utilities when PV power penetration is large. Using a battery is one feasible measure to stabilize a PV system’s power output, but it requires additional costs and results in additional waste of used batteries. In this paper, to overcome these problems, we propose a new method for leveling the fluctuations in a PV system’s power output. By means of the proposed method, output power control of PV system considering the conditions of power utilities becomes possible and the conflicting objective of output power leveling and maximizing energy capture are achieved. Here, fuzzy reasoning is used to generate the output leveling power command. This fuzzy reasoning has three inputs of average insolation, variance of insolation, and absolute average of frequency deviation. Power converter is used to achieve output power same as command power employing PI control law. The proposed method is compared with the method where extracted maximum power is given to the utility without leveling. The simulation results show that proposed method is effective for leveling output fluctuations and feasible to reduce the frequency deviation of the small power utility.