Analysis and evaluation of current distortion for photovoltaic system with isolation transformer

This study describes the study on current distortion of photovoltaic (PV) power generation systems (PVGS) with isolation transformer and includes its reducing methods. The output current of PVGS can be attributed as the difference between fundamental wave and peak harmonic current. When the existing medium voltage distribution network is injected with large capacity of PV power, the voltage increase at the point of common coupling may be caused. Isolation transformer overvoltage will occur in case that the voltage increase is large. The peak harmonic component will appear with the saturation of the isolation transformer. The equivalent model is analysed mathematically. Based on the control strategy of the PV inverter, two methods are presented to decrease the PVGS output current distortion by completely utilising of the available reactive power of the inverter. The theoretical analysis is demonstrated by using the simulation and experimental results in this paper.