A New Enhanced-Phase-Shift Modulation Strategy of Semi-Dual-Active-Bridge Converter for EV Application

Abstract

This paper proposes a new modulation strategy for a bidirectional converter which is used to connect two ultra-capacitors and a traction battery in a hybrid energy storage system of an electric vehicle. Since the voltage across the ultra-capacitors varies in a very wide range, the isolated-semi-dual-active-bridge will be investigated instead of the non-isolated version. In order to save more energy, the system efficiency is enhanced by depressing the circulating current with the converter. This is done in this paper in a direct manner by estimating the load angle between the current and output voltage of one inverter then modifying the modulation parameters. A new technique based on second-order-generalized-integrator is develop to estimate such angle. Simulation study on a 10 kW converter shows that the system efficiency is enhanced about 9% in the forward and 7.4% in backward power transmission respectively by using the proposed modulation strategy instead of the conventional one.