STATCOM-Based Indirect Torque Control of Induction Machines During Voltage Recovery After Grid Faults

• Published in: IEEE transactions on power electronics Vol. 25; no. 5; pp. 1240 - 1250
• Main Authors: Suul, Jon Are, Molinas, Marta, Undeland, Tore
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: A.c. Machines; Applied sciences; Automatic voltage control; Circuit faults; Constraining; Control systems; Electric currents; Electric potential; Electric power; Electrical engineering. Electrical power engineering; Electrical machines; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; Faults; Grid voltage recovery; Induction generators; induction machine stability; induction machine torque; Induction machines; low-voltage ride through (LVRT); Mathematical models; Power system modeling; Power system simulation; Power system transients; Recovery; Regulation and control; static synchronous compensator (STATCOM); Testing. Reliability. Quality control; Torque; Torque control; Voltage; Voltage control; Deregulation; Asynchronous generators; Power system economics; Electric utility; Transient stability; static synchronous compensator (STATCOM); Low voltage; induction machine torque; low-voltage ride through (LVRT); Wind energy; Static reactive compensator; Static synchronous compensator; Asynchronous machine; Control method; Recovery (properties); Flexible AC transmission systems; Cage induction machine; Control system; induction machine stability; Grid voltage recovery; Time domain method; Voltage standard; Electrical network; Torque control; Equivalent circuit; Electric power production; Machine torque
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2009.2036619

This paper proposes a control method for limiting the torque of grid-connected cage induction machines during the recovery process after grid faults, by using a static synchronous compensator (STATCOM) connected at the machine terminals. When a STATCOM is used for transient stability improvement, common practice is to design the control system to keep reactive current at maximum level until the voltage has returned to its initial value. This will result in high torques during the recovery process after grid faults. The control method proposed in this paper is intended to limit such torque transients by temporarily defining a new voltage reference for the STATCOM control system. As torque is controlled through the voltage reference of the STATCOM, the method is labeled indirect torque control (ITC). The presented concept is a model-based approach derived from a quasi-static equivalent circuit of the induction machine, the STATCOM and a The¿venin representation of the power system. For illustration and verification, time-domain simulations of a wind power generation system with a STATCOM at the terminals of an induction generator, are provided. As the objective of limiting the torque of the induction machine is achieved, the derivation of the concept proves to be reasonable. The approach is presented in its most general form, oriented to torque limitation of induction machines both in generating and motoring mode, and is not restricted to the presented example.