A Quasi-Steady-State Observer-Based Control Strategy for Grid-Friendly Repetitive Bipolar Pulse Generator

This work presents a variable frequency phase-shift modulation quasi-steady-state observer-based control (VFPSM-QSSOBC) strategy for series parallel resonant converters (LCC) employed in grid-friendly repetitive bipolar pulse generator (RBPG), which has advantages of high efficiency and low interharmonics injection. To reduce interharmonics, constant power (CP) charging is well achieved by using quasi-steady-state observer to accurately obtain the averaged charging power. The VFPSM strategy is applied to improve the efficiency and narrow down the switching frequency range. In order to validate the feasibility of the proposed design, a 2.8 kW/1.2 kV prototype is constructed. Experimental results show that the prototype has an efficiency of 95.4% and a lower total interharmonic distortion (TIHD) under the rated operation, which proves that VFPSM-QSSOBC has advantages over conventional variable frequency modulation proportion-integration control (VFM-PIC) and frequency trajectory control (VFM-FTC) in the efficiency and the input current quality.