Decoupling Control and Optimization Design for the Buck Converter Feeding Uncertain Load

Buck converter applications are rapidly expanding. A buck converter may feed resistance loads and/or constant power loads (CPLs), or may be connected to direct current (DC grid) as a power source. This requires the buck converter to operate well under various load conditions. Based on the averaged state space model of buck converter in a continues conduction model (CCM), a new control method independent of the load parameters is obtained. Unlike commonly used controllers, the control law is no longer cascaded, but a sum of three parallel controllers, each has clear and enlightening physical meanings. The output voltage is not affected by the supply voltage and the load current. The inductor current can follow the load current immediately. Robust analysis proves that the proposed controller can work steadily over a wide range of loads. This paper also discusses the saturation caused by large load-step, and proposes an optimized design scheme to reduce the voltage fluctuation and minimize the recovery time, or even avoid saturation completely. Simulation and experimental results show that the proposed buck converter has excellent performances whether it feeds resistance loads or CPLs. The decoupling method can be easily extended for other converters or inverters.