Simplified rail power conditioner based on a half-bridge indirect AC/DC/AC modular multilevel converter and a V/V power transformer

Abstract

This paper presents a comprehensive study about a Simplified Rail Power Conditioner (SRPC) based on a half bridge indirect AC/DC/AC Modular Multilevel Converter (MMC) and a V/V traction power transformer. The proposed system with a half bridge MMC can decrease the costs, reduce the control complexity, and require less hardware devices in comparison with the rail power conditioner based on a full bridge indirect AC/DC/AC MMC. Moreover, the SRPC with a half bridge MMC is able to compensate current harmonics, reactive power, and the Negative Sequence Components (NSCs) of currents, which are caused by the unbalance loads between power grid phases. This paper explains the system architecture and its control algorithms based on a pulse width modulation and a proportional integral controller, which is used to control the compensation currents. The simulation results of the SRPC show the submodule voltage balancing control and the DC bus voltage control in order to verify its effectiveness. The compensation strategy based on the NSCs detection is described and evaluated through simulation results.