Step-Up/Down Partial Power Converter with Enhanced MPPT Efficiency Around Zero Partiality

The literature demonstrates that step-up/down partial power converters (PPCs) provide improved efficiency and reduced partiality. However, their operation at the crucial point of equal port voltages is disregarded. This paper investigates the operation of step-up/down PPCs near zero partiality in PV applications. The given PPC has a dc-dc stage capable of operation in all four quadrants. However, two modulation schemes are applied to the converter to implement unidirectional power flow. In addition, this paper also addressed a problem of reduction in maximum power point tracking efficiency that occurs near zero partiality. The current and voltage in the step-up mode of the dc-dc stage are controlled by the phase shift modulation (PSM). The step-down function is extended with reverse power flow (hybrid) modulation. This case study is verified through both simulation and experiment. The experiment is conducted with PPC prototype rated at2.5kW and connected to a 350 V dc bus.