Three-level single-ended primary-inductor converter for photovoltaic power conditioning systems

The two-level single-ended primary-inductor converter (SEPIC) has been used for photovoltaic (PV) power conversion. The two-level SEPIC, however, has high switching losses because of high switch voltage stress. To reduce the switching losses, a three-level SEPIC is proposed. The three-level SEPIC has low switching losses by reducing the switch voltage stress. It improves power efficiency by using a lower-voltage-rated switch, which has better switching performance compared to the switch in the two-level SEPIC. In this paper, the operation of the three-level SEPIC is explained. The control strategy is described to perform the maximum power point tracking (MPPT). The capacitor voltage balance control is also addressed. The experimental results for a 1.0. kW prototype system are discussed for a PV power conditioning system. The three-level SEPIC achieves high efficiency of 96.2% for a 1.0. kW output power, improving power efficiency by 1.3% compared to the two-level SEPIC.