Study on Minimization of Smoothing Capacitor by Increasing Response of Power Supply Converter

This paper describes a new capacitance reduction method of smoothing capacitors in AC-DC-AC type power converters. DC voltage fluctuations due to load fluctuations can be suppressed by the highly responsive control of the input converter, making it possible to reduce the capacity of the smoothing capacitor. To control the input converter with high response, next-generation semiconductor devices (SiC) capable of high-speed switching are used. The target reduction value for the smoothing capacitor in the DC voltage section is set to a value that enables the elimination of the inrush current prevention circuit. The target capacitor value can be determined with simple circuit calculations. By setting a response frequency difference of about 20 times between the input converter voltage control and the output motor control, it is possible to keep the DC voltage constant even with a small-capacity capacitor. The transient response of the DC voltage was observed by time-domain simulation and experiment, and the effectiveness of the proposed method was shown.