A non-resonantly coupled parallel resonant converter for stand-alone applications

A non-resonantly coupled parallel resonant converter (PRC) is used for domestic UPS applications, achieving both high efficiency and high power density. In contrast with the conventional PRC, the non-resonantly coupled method results in modest ratings of the resonant components and smaller stresses on power electronic devices, which is important for high throughput power applications. With the hybrid control strategy, i.e. frequency control combined with phase shift control, the converter maintains zero-voltage-switching (ZVS) throughout the low-frequency cycle, which results in reduced switching losses and EMI. However, this control strategy exhibits disappointing performance for the light load operation. By contrast, the phase shift control strategy shows higher performance and better adaptability over a wide load range. A correction look-up table for the light load operation generated from the steady-state characteristics of the converter improves the shape of the output voltage. Results from both time-domain simulations and a 3 kW prototype are presented to demonstrate the converter as a strong candidate for stand-alone and utility-interfaced applications