Electrolytic Capacitorless Pulsating DC Link Three-Phase Inverter for Low Voltage Battery EVs-Video

Abstract: Sinusoidal Pulse Width Modulation (SPWM) and space vector modulation (SVM) have been widely adopted for three-phase sine AC output from a fixed dc-link if the dc-link voltage is much higher than desired three-phase output. However, if the source/dc-link voltage is lower than the load voltage, then frond-end dc/dc converters becomes necessary leading to the design of the multistage power conversion system. This is the case with the 48 V electrical vehicles (EVs). To implement the propulsion drive system with existing SVM or carrier-based modulation, a large costly unreliable electrolytic capacitor is employed to develop a high voltage intermediate dc link. Novel Single-reference-Six-Pulse Modulation (SRSPM) eliminates the dc-link electrolytic capacitor allowing pulsating dc-link voltage waveform at the inverter input. It substantially reduces the cost, size, and weight and improves the reliability of the system. This novel SRSPM is simple and results in a saving of 87% switching losses. The concept has been experimentally demonstrated with closed-loop control to achieve 97% efficiency in the lab.