Automatic tuning of the switching frequency for efficiency maximization in an ESS-PV hybrid PCS

Abstract

An automatic switching frequency tuning algorithm (ASTA) for a real-time condition is proposed. The primary aim is to maximize the power efficiency of a power electronic system. The power loss of a hard-switched power converter is determined by the power loss in power semiconductor devices, magnetic devices, capacitors, etc. Switching frequency of a power converter is one of the parameters which influence the power loss. The parameters which determine the maximum-efficiency point can vary with the ageing of devices and the change in environmental conditions. In this paper, a PWM-carrier frequency is utilized for efficiency maximization of a power conversion system. By varying the PWM-carrier frequency from the minimum to maximum value to search for the switching frequency associated with the point of maximum efficiency, this algorithm is designed for a hybrid-energy power conversion system which consists of DC/DC converters and a DC/AC inverter. For the realization of this algorithm, real-time power metering for efficiency calculations is realized by software, which requires no cost increase as the method shares the voltage-and-current sensing circuits with the converter control unit. The metering algorithm has tolerance of less than 1% over a wide load range. The experimental results present efficiency data captured during the operation of the ASTA algorithm in wide ranges of switching frequencies.