A Single-Stage Constant Power Capacitor Charging Architecture for Flicker Mitigation for High-Power Pulsed Loads

Capacitor chargers for pulsed power loads are typically realized as two-stage systems consisting of a front-end rectifier and a dclink filter followed by a dc/dc converter. Whereas such systems generally operate in constant current charging mode, it has recently been demonstrated that constant power charging may be achieved and can effectively eliminate line-side flicker. In this article, these ideas are extended to a single-stage capacitor charger architecture in which the modulation index of a three-phase voltage source converter is controlled to both actively shape the line current waveforms, eliminating reactive power and current harmonics, as well as to provide constant power capacitor charging, thereby eliminating flicker. A detailed description of the control scheme is presented, and a method for controller design is proposed. Finally, the performance of the proposed method is assessed in a case study based on European Spallation Source klystron modulator requirements (pulse amplitude 115 kV/100 A, pulselength 3.5 ms, pulse repetition rate 14 Hz). The designed capacitor charger is validated through circuit simulation and compared to the existing capacitor charger solution.