An Improved Down-Scale Evaluation System for Capacitors Utilized in High-Power Three-Phase Inverters under Balanced and Unbalanced Load Conditions

Abstract

The DC-link capacitors in an electronic power system are the main constraint of the power density and lifespan of the power converters. Evaluating the load life of capacitors working in severely adverse circumstances plays an important role in the design stages of the next-generation power converters. In this article, an improved evaluation system for the capacitors utilized in high-power three-phase voltage source inverters is proposed. The purpose of this article is to reproduce the same encountered stresses when a DC-link capacitor is used in a high-power inverter with pulse-width modulation. Hence, an improved down-scale evaluation system for the DC-link capacitors used in high-power three-phase inverter systems under balanced and unbalanced load conditions is proposed. Moreover, AC and DC analyses in the proposed evaluation system are conducted. The equivalent circuit and transfer functions are derived to verify the proposed evaluation system. Finally, a prototype system is constructed to facilitate the theoretical results as the verification.

Keywords

• DC-link capacitors
• three-phase inverters
• down-scale evaluation system
• unbalanced load condition
• life of capacitors