Distributed Control Method for Power Conversion System With Series-Connected Autonomous Modular Converters

This article proposes a current droop control for series-connected current source converters in a universal smart power module (USPM) concept. In this concept, power conversion systems are constructed by USPMs, which have a high-speed controller and autonomous distributed control. USPM enhances versatility by its high flexibility and usability compared to power electronics building blocks, which is a similar concept. In this system, noninterference control is required because these USPMs are operated independently without sharing information with each other. Droop control for the voltage source converter is a common solution for parallel-connected converters. Likewise, a stabilization method for the current-source-type converter connected in series is necessary for the USPM system. The proposed method in this article solves these problems. In particular, the configuration of the current controller and its gain design method is verified in order to achieve a stable condition and high-speed response. The experimental results for the 500-W system reveal that the stability limit of the PI control adopting the proposed current droop control agrees with the analytical results with an error of 1.3%. Furthermore, this article demonstrates that the current deviation agrees with that of the design value with an error of 3.0% or less.