iecon-statcom - 1 System Modeling and Control Design for...

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1 Abstract —Static compensators can be used for voltage regulation in the presence of flicker or transients on parallel connected loads in a distribution system. This paper presents a general modeling strategy that allows design of a fast voltage magnitude controller accounting for system parameters. The co- ordinate transform used in modeling the system facilitates extraction of linearized system dynamics with the help of circuit simulators. It is also shown that the problem of voltage regulation using instantaneous reactive current is non-minimum phase for certain operating conditions, thereby limiting its dynamic response irrespective of the control design method. Simulation results with a controller designed using input output bode plot are presented to prove the efficacy of the proposed method. Index Terms —Flicker mitigation, Modeling, STATCOM, STATCOM control, Voltage regulation. I. INTRODUCTION ast load voltage regulation is required to compensate for time varying loads such as electric arc furnaces, fluctuating output power of wind generation systems, and transients on parallel connected loads (e.g. line start of induction motors) [1]-[3]. Reactive power compensation is commonly used for flicker mitigation and load voltage regulation. Due to their high control bandwidth, Static Compensators (STATCOMs) based on three phase pulse width modulated converters, have been proposed in [1], [4]- [8] for this application. For effecting fast control, the STATCOM is usually modeled using the dq axis theory for balanced three phase systems, which allows definition of instantaneous reactive current [9]. Most literature on STATCOM control concentrates on control of STATCOM output current and dc bus voltage regulation for a given reactive current reference. Regulation of load voltage is achieved using a PID controller that generates the reactive current reference (e.g. [10]). For this paper it is assumed that the STATCOM can be modeled as a controlled current source. The problem addressed here is to design a voltage magnitude controller that will generate the reactive current reference for the STATCOM. Other than experimental procedures like Zeigler and Nichols [11], to the A. K. Jain and N. Mohan are with the Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455. (phone: 612-624-7309, fax: 612-625-4583 E-mail: akj@ece.umn.edu, mohan@ece.umn.edu). A. Behal is with the Department of Bioengineering, Clemson University, Clemson, SC 29634-0915. (E-mail: abehal@ces.clemson.edu). authors’ knowledge, there is no standard procedure for designing a load voltage controller that ensures the required bandwidth and robustness to system variations. In [4], a small signal model of the system was derived by transforming the equivalent impedance of the ac system to the dq frame.
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This note was uploaded on 07/30/2011 for the course EEL 3657 taught by Professor Staff during the Spring '08 term at University of Central Florida.

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iecon-statcom - 1 System Modeling and Control Design for...

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