抄録
Islanding of the utility interconnected photovoltaic (PV) systems mainly installed in residential houses is a most serious problem for safety of utility distribution lines. Output power variation method is one of the recommended measures in the Japanese guidelines on utility interconnection. However, the effectiveness of the measure decreases in the case of parallel operation of PV systems because of a counteraction of output power variation from each system. A new output power variation method applicable to parallel operation of PV systems was examined in this paper through simulation studies, using the simulation method developed based on demonstration tests in Rokko Island. The major results of the study are follows:
- A new output power variation method was proposed in order to match frequency and phase of power variation among PV systems. In the method, phase angle of inverter output current is continuously modulated with instantaneous voltage signal of distribution line.
- The simulation results on the proposed method shows that even when a number of PV systems are operated, islanding can be prevented securely while maintaining power quality of inverter output in nomal operation. This suggests that proposed output power variation method can be applied to actual field.
