Output Feedback Control of Single-Phase UPQC Based on a Novel Model

• Published in: IEEE transactions on power delivery Vol. 24; no. 3; pp. 1586 - 1597
• Main Authors: Rong, Yuanjie, Li, Chunwen, Tang, Honghai, Zheng, Xuesheng
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Control systems; Controllers; Discrete systems; Discrete transforms; Disturbances. Regulation. Protection; Electric potential; Electrical engineering. Electrical power engineering; Electrical machines; Electrical power engineering; Equilibrium manifold; Exact sciences and technology; Feedback control systems; harmonic detection; Inverters; Lighting control; Linear systems; Mathematical models; Operation. Load control. Reliability; Output feedback; Pi control; Power electronics, power supplies; Power networks and lines; Power quality; Power system modeling; Regulation and control; Studies; unified power-quality conditioner (UPQC); Voltage; Performance evaluation; Control synthesis; Discrete system; Equilibrium manifold; harmonic detection; Control constraint; Switching conditions; Closed loop systems; Linearization; Pulse width; Dynamic characteristic; Adaptive detection; Series inverter; Flexible AC transmission systems; Control system; Power electronics; unified power-quality conditioner (UPQC); Constrained optimization; Linear system; Power control; Quality control; Equivalent circuit; Pulse duration modulation; Output feedback; Comparative study
• ISSN: 0885-8977; 1937-4208
• DOI: 10.1109/TPWRD.2009.2016802

The single-phase unified power-quality conditioner can be treated as a typical switched linear system due to its typical switching dynamic characteristics. However, because the switched model is difficult for controller design, we first transform it to an equivalent discrete system model (EDSM) in light of the pulsewidth-modulation principle. The EDSM is further transformed to a linear equivalent discrete system model (LEDSM) by states reconstruction and linearization at some neighborhood of the equilibrium manifold. The LEDSM, where the pulsewidths are adopted as the controller variables, is a periodical discrete linear system with the constrained control. Since some states cannot be available, the output feedback periodical-switched controller is designed to meet suboptimal performance and stabilize the closed-loop system. Compared with the proportional-integral controller, the output feedback control strategy features better characteristics. The voltage reference for the series inverter is obtained by using an adaptive voltage detection method. Simultaneously based on the detected phase of the system voltage, the instantaneous reactive power theory is adopted to calculate the reference current for the shunt inverter. Additionally, the power flow and power consumption are described and analyzed. Simulation results demonstrate the effectiveness and reliability of the proposed control strategy.