Current Control System of Hybrid Converter for Suppressing Current Harmonics

The driving electric machine of high-power flywheel energy storage system (FESS) has the characteristics of high fundamental frequency and low inductance, which lead to high current harmonic content and increases the loss of FESS. To suppress the current harmonics, a compound control scheme is proposed for an innovative hybrid converter in this paper. The mathematical model of the hybrid converter is analyzed and divided into two parts: main voltage source converter (MVSC) and filtering voltage source converter (FVSC). According to the characteristics of MVSC and FVSC in output power and switching frequency, two different regular sampling strategies are described and applied. On this basis, the exact MVSC model in discrete time-domain is established, and the current controller with complex vector decoupling is designed. Similarly, a current controller with feedback decoupling is designed for FVSC in the continuous time-domain. Both the current controllers have excellent robustness and dynamic response ability. Finally, the proposed control strategy in this paper is verified by simulation results.