Control Strategy of Non-Grid-Side-Converter-Based Varibale Frequency Transformer Under Dual-Side Harmonic Distorted Grid Voltages

Variable frequency transformer (VFT), a new type of flexible alternating current transmission equipment, is easier to operate under dual-side harmonic distorted grid voltages for its windings are directly connected to two power grids. This paper presents a novel topology of non-grid-side-converter-based VFT (NGSC-VFT). Operations of proposed NGSC-VFT under ideal and harmonically polluted grid voltages are detailed. Control strategy for two series converters is proposed to eliminate the torque and power fluctuations at different frequencies. The effectiveness of proposed topology of NGSC-VFT and corresponding control strategy is verified via simulation studies.