A Magnetic Saturation Suppression Scheme of The Output Line-Frequency Transformer in Photovoltaic Inverter

Affected by dead time, the asymmetric action of power switches and the offset sampling of current sensor, there is a certain DC component in output waveforms of photovoltaic inverter, which leads to a magnetic core saturation of the output line-frequency (LF) transformer. This paper proposes a magnetic saturation suppression scheme for the output LF transformer, and deeply analyzes its suppression principle and the regulator design in detail. The proposed suppression scheme detects the primary current of the output LF transformer as the feedback signal of the core’s working state and adds a DC bias correction loop outside the output voltage loop (the grid current loop) to correct the DC bias for each LF output cycle, thus avoiding the magnetic saturation of the output LF transformer. In addition, this scheme also eliminates the influence of the current sensor’s offset sampling. Experimental results verify the correctness and feasibility of the theoretical analysis.