Model-Based Design and Optimization of Hybrid DC-Link Capacitor Banks

Abstract

For the applications where a single capacitor is incapable to meet the needs, multiple capacitors are connected in series or in parallel as a bank to fulfill the capacitance and voltage rating requirements. Even though some commercial products have already existed in the market, most of the designs use the same capacitors or combine different types of capacitors by experience, so that the volume, cost, reliability, and power loss are not optimized. To the best knowledge, no quantitative design considering all these design aspects is available for capacitor banks. This article proposes a model-based optimal design method for hybrid capacitor banks consisting of both electrolytic capacitors and film capacitors. Performance factors, such as impedance characteristics, lifetime, power loss, cost, and volume, are modeled and considered in the optimization process. The selection of the capacitance ratio between the two types of capacitors and the number of capacitors connected in parallel are analyzed based on specific design constraints. A case study of the dc-link capacitor bank design for a 5.5-kW inverter is presented to demonstrate the modeling and optimal design process.