Medium frequency soft switching DC/DC converter for HVDC transmission system

An isolated medium frequency zero voltage zero current switching (ZVZCS) DC/DC converter for HVDC transmission system is proposed. Soft switching is achieved over the entire load range, via resonance between transformer leakage inductance and capacitance across primary switches. Since transformer leakage inductance is utilized in the resonant circuit, its design procedure is elaborated as well. Finite element simulation aided iterative design ensures transformer has leakage inductance close enough to desired value. Controller design is completed and the closed-loop system is simulated in PLECS^®. Converters series connected at the output are also simulated to show scalability.

I. Introduction

Though many DC/DC converters have been proposed, few are suitable for high power levels. With the development of HVDC transmission and energy storage system, kV/MW sized DC/DC converters have become a focus of power electronics research efforts. Soft switching is desired to allow higher switching frequency without suffering from high switching losses.