Design of parallel resonant DC-link soft-switching inverter based on DSP

A novel digital-controlled soft-switching pulse width modulation (PWM) inverter is presented by using a new kind of parallel resonant dc-link (PRDCL). The new PRDCL provides variable link pulse width, which is superior to other resonant de-links, and thus the PWM capability can be remarkably increased. The SPWM modulation strategy and digital PID control based on digital signal processor (DSP) can also enhance the PWM capability of the inverter. The applied algorithm is able to eliminate narrow PWM pulses, which impede de-link operation. Operational principles, analysis and the realization of a digital controlled PRDCL inverter are presented. A 500 W single-phase resonant soft-switching inverter prototype is set up based on DSP. The experiment results verify the control method and the soft-switching effects. At the same time, the THD is decreased greatly, which makes the output waveform improved.