The Wide Multiplexed Period Three-Phase Multiplexing Arm Modular Multilevel Converter

Three-phase multiplexing arm modular multilevel converter (TPMA-MMC) possesses cost-efficiency advantage by employing a pair of multiplexing arms. However, the narrow multiplexing arm energy regulation period results in the limited modulation range [0.82, 1]. This article proposes a wide multiplexed period operation principle with the multiplexing arm energy regulation period being extended to one-fundamental period, and with which, it realizes to expand the modulation range to [0, 1]. Besides, based on it, the existing “overlap” period could also contribute to realize the multiplexing arm energy balance in one-third fundamental period. Therefore, the analysis of this new principle indicates that TPMA-MMC demonstrates some improved advantages. Compared to MMC, it reduces by 21.8% in submodule (SM) count, 28.9% in operation loss, and 39.9% in energy storage, which could result in lower construction cost, footprint, and higher efficiency and power density, and the proposed principle also permits TPMA-MMC to possess higher efficiency than that with the narrow range principle. Finally, the proposed wide multiplexed period operation principle and control scheme are verified by simulation and scale-down prototype experimental results.

I. Introduction

The modular multilevel converter (MMC) has been the main converter in medium-voltage (MV), high-voltage (HV), and high-power applications with many excellent properties, such as high modularity, scalability, and less harmonics performance [1], [2], [3]. However, just like cascaded H-bridge (CHB) converter [4], MMC consumes abundant semiconductor devices and capacitors whether the submodule (SM) is half-bridge (HB) SM or full-bridge (FB) SM, where the capacitor volume occupies the main volume and weight of MMC [5], [6], [7], which leads to high cost, conduction loss, and bulky footprint. Therefore, in order to settle these challenges, many innovative works have been carried out.