A Small Photovoltaic Inverter Design Based on STM32 Controller and Soft Switching Method

A small photovoltaic (PV) inverter design with a 500W output power rating that is based on an STM32 micro-controller together with soft-switching is proposed in this study. Aiming at the current issues with small PV inverters for home regarding output voltage harmonics and low output power efficiency, the soft switching method is applied to improve power transfer efficiency as well as to reduce harmonic factors. Applying a two-stage transfer circuit structure with DC-DC and DC-AC, the proposed design takes two pulse width modulation (PWM) waveforms which are a complement to each other with higher resolution that is generated by the STM32 microcontroller. The first DC-DC stage is driven by one PWM signal and the second DC-AC stage is driven by the complementary PWM signals. Also, there are a sampling circuit, a protection circuit which is to prevent over-voltage, overcurrent, and over-heat, and an LC filter circuit which is to remove higherorder harmonics. Through the simulation, the proposed PV inverter design has a better dynamic performance with a stable output voltage level due to excellent filtering that is suitable for family house applications.