Transformerless Minimum Phase Interleaved Hybrid Converter with Low Leakage Current

Abstract

Hybrid converters are predominantly used in modern residential distribution systems, as they are capable of supplying DC and AC loads simultaneously. But, the main concern in conventional transformerless hybrid converter is the common mode leakage current for photovoltaic applications, when they are connected to grid or their neutral point is grounded. Because of the flow of leakage current, the system losses increase, power quality decreases, and the nearby systems get affected from electromagnetic interferences. The other issues are non-minimum phase behavior due to presence of right hand plane zero in the transfer function of control to dc output voltage and narrow ranges of modulation index (M i ) and duty ratio (D) (i.e. D+M i ≤ 1). Due to narrow range of modulation index (M i ) and duty ratio (D), there is a compromise between DC voltage gain and quality of AC output. A transformerless minimum phase interleaved hybrid converter is proposed in this paper to eliminate the above difficulties. A hybrid PWM technique is proposed for the proposed converter which helps not only to minimize the leakage current but also to obtain both AC and DC outputs simultaneously. Moreover, the proposed hybrid converter is operated both in D + M i ≥ 1 and D+M i ≤ 1 as well as it maintains the minimum phase behavior. A 210 W scaled down laboratory prototype of proposed converter is developed and verified in this work.