Leakage current minimisation in transformerless wide operating range interleaved minimum phase hybrid converter with improved ac output quality

Abstract

This study proposes a transformer-less interleaved minimum phase hybrid converter, which is capable of delivering both AC and DC outputs, with reduced leakage current for photovoltaic applications. As the conventional transformer-less hybrid converters have the limitation of strong common-mode leakage current, when they are connected to the grid or their neutral point is grounded, a hybrid unipolar-based sinusoidal pulse-width modulation technique is used in the proposed hybrid converter to minimise the total common-mode voltage during its operation. Moreover, the proposed hybrid converter has a wide operating range of duty ratio (D) and modulation index (Mi), i.e. it can operate at both the conditions D+Mi≥1andD+Mi≤1, unlike the conventional hybrid converters. Furthermore, the proposed hybrid converter exhibits minimum phase behaviour; which results in simpler controller design, high loading capability and fast dynamic response. In addition, it has improved output AC voltage quality because of operation at high MiMi values. The proposed hybrid converter also exhibits superior cross-regulation during dynamic load change conditions. The performance of the proposed converter is compared with other similar topologies to bring out its advantages. Detailed mathematical modelling is carried out and a 900 W laboratory prototype is developed to verify its performance. © The Institution of Engineering and Technology 2020.