A Novel Hybrid Modular Three-Level Shunt Active Power Filter

Shunt active power filters (SAPF) are employed to improve power quality by injecting compensating harmonic current. The modular SAPF offers many new capabilities that are otherwise unavailable by the conventional SAPF, such as high crest factor compensating current and fast dynamic response. However, there are still challenges that are needed to be addressed, such as resonance and stability issues associated with the modular SAPF. To investigate these issues, this paper first presents a mathematical model for conventional modular SAPF system. Based on the mathematical analysis, a new hybrid three-level modular SAPF is presented that is composed of two types of modules, each with different current carrying capacities, LCL filter parameters, and switching frequencies. The proposed hybrid system provides a wider current tracking bandwidth and fast dynamic response as compared to the present modular SAPF. A novel self-adaptive active damping strategy is proposed that effectively suppresses resonance and coupling between modules. Mathematical analysis and experimental results have been used to verify the proposed system.