A family of high step-up bipolar-output DC-DC converters with perfect parasitical parameters self-balance for AC module applications

Purpose The purpose of this paper is to propose the converter implemented in AC module applications to convert the output low-voltage of the photovoltaic panel to the high-voltage of the grid bus. Design/methodology/approach Two novel bipolar step-up cells (BSCs) are proposed, and from these, a family of high step-up bipolar DC-DC converters (HSBDCs) is also presented. Then, based on a two-winding coupled inductor and an active clamped circuit, the novel HSBDC with BSC-I is studied in detail as an example. Besides, an active clamped circuit is used to transfer the energy stored in the leakage inductor to avoid the voltage imbalance between the bipolar outputs. The three-winding coupled inductor is replaced with a two-winding coupled inductor and having it shared by the bipolar outputs. Findings A family of DC-DC converters is proposed to realize high voltage gain and bipolar outputs. The proposed converter is analyzed in detail and the experiment results efficiently validate its performance. Originality/value The prominent characteristics of the proposed converter include the voltage stress on all diodes and output capacitors being half of its output voltage, high voltage gain, low output voltage ripple, soft switching for all switches, zero-current switching for all diodes, bipolar outputs and a common ground shared between the input power source and the neutral point of the bipolar outputs to suppress leakage current. The bipolar output voltages achieve absolute self-balance and eliminate the effect of the parasitical parameters from all semiconductor components, input source and coupled inductor.