Comparison of zero‐sequence injection methods in cascaded H‐bridge multilevel converters for large‐scale photovoltaic integration

Photovoltaic (PV) power generation levels in the three phases of a multilevel cascaded H‐bridge (CHB) converter can be significantly unbalanced, owing to different irradiance levels and ambient temperatures over a large‐scale solar PV power plant. Injection of a zero‐sequence voltage is required to maintain three‐phase balanced grid currents with unbalanced power generation. This study theoretically compares power balance capabilities of various zero‐sequence injection methods based on two metrics which can be easily generalised for all CHB applications to PV systems. Experimental results based on a 430 V, 10 kW, three‐phase, seven‐level cascaded H‐bridge converter prototype confirm superior performance of the optimal zero‐sequence injection technique.