Abstract
Parallel hybrid converters utilise partially rated Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) based converters as active filters or partial power transfer for slower switching Silicon (Si) Insulated-Gate Bipolar Transistor (IGBT) based converters. This allows the effective SiC MOSFET switching frequency of the overall converter to be significantly increased, reducing the requirement for external filters and increasing the converter’s current control bandwidth, without relying on a wholly SiC MOSFET-based approach in the same topology. In the practical network system, the transformer and capacitor are usually adopted as Inductor-Capacitor-Inductor (LCL) filters after the converter. This paper investigated the potential performance of Parallel Hybrid Converter (PHC) topology with the LCL filter and also designed the component parameters for this topology, including the IGBT and SiC impedance. The parallel direct current supply for both converters also opens up the potential for partial-load efficiency improvements. A long-horizon finite step model predictive current controller is implemented as the control system, which allows significant flexibility in the converter’s operation, compared with direct space vector control and fractional power control. The results validate that the parallel hybrid converter with an LCL filter could achieve the grid-current total harmonic distortion (THD) below 3% with IGBT bridge frequencies in 2 kHz. The stability performance in dynamic situations, including system fault and harmonic injection, is also verified.
