An ETO Thyristor and Modular H-bridge PWM Converter-based 4.5MVA STATCOM: 480V/500A Transformerless Grid-Connected Experimentation

Static synchronous compensator (STATCOM), providing quick and robust voltage support, is an "enabling infrastructure technology" for the electric power system today. Based on the emerging emitter turn-off (ETO) thyristor and cascaded-multilevel converter (CMC) comprising modular H-bridge voltage source converters (VSCs), a 4.5MVA prototype STATCOM system is developed. In this paper, the 480V/500A transformerless grid-connected experimentation of the STATCOM prototype is presented. The system design with emphasis on the passive component selection and digital controller is described. An AC-side energization and de-energization method of the STATCOM is proposed and experimentally verified. The experimental results of steady-state and dynamic performance, as well as the DC bus voltage balancing, are shown. The system loss and cooling performance are given. Through such experimentation, the prospect of a state-of-the-art STATCOM system with high performance and low cost is demonstrated