Parasitic ringing and design issues of digitally controlled high power interleaved boost converters

High power boost converter has become the essential part of the distributed power system that enables energy to be fully utilized in fuel cell powered electric vehicles and stationary power systems. This paper presents analysis and design of a high-power multileg interleaved boost converter with a digital signal processor (DSP) based controller. A 20-kW converter was designed with coupled inductors to allow core-loss reduction and designed with high frequency switching to minimize the component size and eliminate the switching losses under discontinuous conducting mode operation. A dual-loop average current mode current control method implemented in DSP is employed to achieve the fast transient response. It was found through circuit analysis, simulation and experiment that the boost inductor interacted with the device parasitic capacitor and created unnecessary oscillating current whenever it reached zero current. Two high-power devices were used in both simulation and experiment to verify the analysis and design for a wide load range. Simulation and experiment results of the 20-kW boost converter under startup condition and load transient condition are also presented. Different anti-windup schemes for a typical PI-controller are evaluated. The results show that this typical controller with proper anti-windup scheme achieves better transient performance than without anti-windup scheme.

I. Introduction

A DISTRIBUTED energy resource consisting of a fuel cell, battery and possibly other energy storage components can be used in electric vehicles and stationary power system applications, which normally require a high-power boost converter for energy management that employs an energy storage component to assist the slow-responding fuel cell [1]. The high power boost converter is an essential interface between the fuel cell or battery source and the dc bus that serves as the inverter input. Multiphase structure with interleaved control is essential for the high-power boost converter in order to reduce the ripple current and to reduce the size of passive component. It is possible to adopt the interleaved multi-leg boost structure operating in discontinuous conducting mode (DCM). In low power applications, the concept has been proven working properly [2]. However, in high power applications, the boost inductor design and parasitic ringing become major problems in DCM operation. It is one of the intentions of this paper to explore the design of interleaved DCM boost converter and their parasitic ringing effects.