Generalized closed-loop control (GCC) schemes with embedded virtual imepdances for voltage source converters

Abstract

In this paper, a generalized closed-loop control (GCC) scheme is proposed for voltage source converters (VSCs) with LC or LCL output filters. The proposed GCC scheme has a single-loop control of inverter output (voltage or current) and two parallel virtual impedance terms using additional measurements. The virtual impedance can be the equivalent internal impedance or external impedance (or both) depending on their control term and feedback variable selection. The internal impedance term is mainly responsible for providing desired damping to the filter circuit, and the external virtual impedance term can effectively adjust the converter system closed-loop output impedance. As the GCC scheme provides distinct physical meaning of each control term, it can make the parameter tuning more straightforward and robust. Additionally, the proposed GCC scheme can tackle some challenging control objectives by avoiding the harmonics filtering or derivative terms. Experimental results validate the proposed GCC scheme.