An ATC-SPWM Method to Solve the Soft-Switching Failure Problem of Resonant DC Link Inverter Based on FPGA

The auxiliary circuit of the resonant dc link (RDCL) inverter is likely to cause soft-switching failure and voltage loss problems when it operates frequently under small pulses. To solve those problems, this article proposes an FPGA-based sine pulsewidth modulation method (SPWM) with an auxiliary triangular carrier. This method can solve the operation problem of the auxiliary circuit under small pulses, and the method does not need to acquire the load current, but only judges the width of the small pulse based on the magnitude of the modulating waveforms, so as to restructure the driving signals inside the FPGA and avoid the soft switching failure problem. Compared with existing SPWM method, this method compensates the output voltage and improves the waveform quality. The method is experimentally verified to reduce the output current harmonics by 0.89% at 16 kHz switching frequency. When the switching frequency was increased to 40 kHz, the output current harmonics decreased by 1.44%.