Title :
Generalized Closed-Loop Control Schemes with Embedded Virtual Impedances for Voltage Source Converters with LC or LCL Filters
Author :
He, Jinwei ; Li, Yun Wei
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of Alberta, Edmonton, AB, Canada
fDate :
4/1/2012 12:00:00 AM
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 each term in the GCC scheme can be controlled independently, the proposed GCC scheme has great flexibility and can easily realize and explain the performances of the traditional single- and multiloop control schemes and their different variations. Moreover, the GCC scheme provides a distinct physical meaning of each control term, which makes the control parameter tuning more straightforward and robust. Additionally, as shown in this paper, the proposed GCC scheme can tackle some traditionally challenging control objectives by avoiding the harmonics filtering or derivative terms. Experimental results from laboratory VSC prototypes are obtained to validate the proposed GCC scheme.
Keywords :
closed loop systems; damping; electric impedance; power convertors; power filters; GCC scheme; LC filter; LCL filter; converter system closed-loop output impedance; distinct physical meaning; embedded virtual impedance; feedback variable selection; filter circuit; generalized closed-loop control scheme; harmonics filtering; internal impedance term; inverter output; multiloop control scheme; parallel virtual impedance; single-loop control; voltage source converter; Active filters; Capacitors; Impedance; Power conversion; Power filters; Power harmonic filters; Active damping; LC filter; LCL filter; generalized closed-loop control (GCC); multiloop control; single-loop control; virtual impedance; voltage source converter (VSC);
Journal_Title :
Power Electronics, IEEE Transactions on
DOI :
10.1109/TPEL.2011.2168427