Reactive Power Control Method for Reducing Voltage Fluctuation in Large-scale Photovoltaic Systems

For large-scale photovoltaic (PV) systems, we have developed a large capacity power conditioning system (PCS) with three functions: fault ride through function, harmonic reduction function and voltage control function. This paper deals with our new reactive power control method of the PCS for reducing voltage fluctuation in large-scale photovoltaic systems. The proposed method reduces the voltage fluctuation caused by the active power of PV by adjusting the power factor of the PCS automatically to the optimal value according to the conditions of power systems. In this paper, the control operation and the control effect of our proposed method were examined by numerical analysis and an experiment using small PCS models. We verified that the voltage fluctuation caused by output of PV at interconnecting point could be reducing by controlling reactive power at the optimal value according to the power system conditions. Then, we confirmed that there is no need to increase the PCS capacity by the adjusting the offset of the reactive power properly. Finally, we confirmed the voltage fluctuation could be reduced without biasing the reactive power to a specific PCS even if there is difference between outputs of plural PCSs operating in parallel.