Multimode Modulation With ZVS for a Single-Phase Single-Stage Inverter

Abstract

This article presents a modulation with zero-voltage switching (ZVS) for a single-phase, single-stage inverter intended for photovoltaic applications. In single-stage inverters, the dc-ac conversion stage is merged with the active power pulsation buffer stage. The proposed architecture uses a flying capacitor to handle the difference between the instantaneous input and output power, instead of the traditional bulky input capacitor. In this single-stage inverter, both the input current and the output voltage are controlled by the current of a single inductor. The inductor is operated in variable frequency boundary conduction mode. Multiple operation modes are used along the line cycle, all of them with ZVS in all transitions. The operation mode and control times are determined by the target input current, target inductor current, input voltage, output voltage, and flying capacitor voltage through equations that model the inductor waveform. These equations are solved with a fixed-point iteration method in a field-programmable gate array (FPGA). The modulation and control are validated in a 1 kVA prototype with 400 V input and 240 Vrms, 60 Hz output.