Single-phase Modular-Multilevel Converter Based on Concept of Universal Smart Power Module (USPM)

Abstract

This paper proposes control method for a power conversion system constructed by combining power conversion modules based on a new concept called Universal Smart Power Module (USPM). The USPM consists of a H-bridge including the controller, and a power converter is realized by using multiple modules. The proposed method avoids interference between the controllers installed in each module due to series or parallel connection of modules. In addition, the main controller sends the signals to suppress the deviation occurred in the operation of the module controller. These signals are updated through low-speed wireless communication. Therefore, it is necessary to verify low frequency communication and communication blackout. The main controller generates effective command values instead of instantaneous command values to overcome the communication problems. The module controller converts the effective value into an instantaneous value to realize normal operation. With this control method, the power conversion system can be operated even in the event of communication delay, infrequent communication, or communication blackout. In this paper, a single-phase Modular Multilevel Converters (MMC) with four modules was used in experiment for the purpose of effectiveness of the proposed method. As a result, the proposed control method was experimentally confirmed achieving an input current THD 2.63% and an input power factor of 0.99 on steady-state and operating stable even in the event of communication delay, infrequent communication, or communication blackout.