Effects of various power system stabilizers on improving power system dynamic performance Ping He a,b , Fushuan Wen c,d,⇑ , Gerard Ledwich c , Yusheng Xue e , Kewen Wang f a School of Electrical Engineering, South China University of Technology, Guangzhou 510640, China b College of Electrical and Information Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China c School of Electrical Engineering and Computer Science, Queensland University of Technology, Brisbane, Queensland 4001, Australia d School of Electrical Engineering, Zhejiang University, Hangzhou 310027, China e State Grid Electric Power Research Institute, Nanjing 210003, China f School of Electrical Engineering, Zhengzhou University, Zhengzhou 450001, China article info Article history: Received 14 June 2012 Received in revised form 27 September 2012 Accepted 9 October 2012 Available online 23 November 2012 Keywords: Power system stabilizer Eigenvalue analysis Small/large-signal stability Electromechanical modes abstract To ensure the small-signal stability of a power system, power system stabilizers (PSSs) are extensively applied for damping low frequency power oscillations through modulating the excitation supplied to synchronous machines, and increasing interest has been focused on developing different PSS schemes to tackle the threat of damping oscillations to power system stability. This paper examines four different PSS models and investigates their performances on damping power system dynamics using both small- signal eigenvalue analysis and large-signal dynamic simulations. The four kinds of PSSs examined include the Conventional PSS (CPSS), Single Neuron based PSS (SNPSS), Adaptive PSS (APSS) and Multi-band PSS (MBPSS). A steep descent parameter optimization algorithm is employed to seek the optimal PSS design parameters. To evaluate the effects of these PSSs on improving power system dynamic behaviors, case studies are carried out on an 8-unit 24-bus power system through both small-signal eigenvalue analysis and large-signal time-domain simulations. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Power systems worldwide have been continuously expanding in scale and evolving into more complicated structures in past dec- ades, and have to operate more frequently close to their limits as the results of geographical and physical limitations as well as the power industry restructuring. The secure operation of power sys- tems, therefore, has become a major concern, and the applications of power system stabilizers (PSSs) for dynamic stability enhance- ment have drawn more attention than ever before [1–10]. Conven- tional lead-lag PSSs (CPSSs) have been widely used by electric utilities for this purpose. A PSS is used to provide some supplemen- tal damping to rotor oscillations via an electric torque which is in phase with the speed deviation [1]. In view of the fact that power systems are highly nonlinear and operating conditions can vary over a wide range, various kinds of PSSs have been developed in the past decades, such as the fixed parameter decentralized PSS, the adaptive PSS, and the fuzzy logic based PSS, to name a few [2–6]. In order to take into account more system operating conditions, the probabilistic eigenvalue analysis method was proposed for designing power system damping controllers [11–13]. With this approach, the system stability is reinforced by shifting the distribu- tion ranges of the critical eigenvalues toward the left side of the complex plane. Coordination of the controller parameters was achieved through solving a non-linear programming problem, in which the objective function is composed of all unsatisfactory eigenvalues. The objective function is minimized by using optimi- zation approaches such as the steepest descent (SD) method so that the overall performance of the controller could be optimized under the given system states. Up to now, various PSS design methods have been proposed and some applied to different degrees in actual power systems [3– 8,11,12]. CPSSs are generally based on fixed parameters, and it is hence not yet possible to achieve the optimal behavior for various operating conditions of a power system. The adaptive power sys- tem stabilizers, as reported in [3–6], could track the changes of sys- tem dynamics in real time, and hence could perform well for various operating conditions in principle. In 2003, a novel PSS architecture was proposed in [7] and later included in the revised IEEE Std-421.5 as PSS4B in [15]. Up to now, several kinds of PSSs have been proposed, and it is not clear about their relative perfor- mances. With the development of large-scale power systems, a 0142-0615/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijepes.2012.10.026 ⇑ Corresponding author at: School of Electrical Engineering, Zhejiang University, Hangzhou 310027, China. Mobile: +86 13968105384; fax: +86 571 87952014. E-mail address: fushuan.wen@gmail.com (F. Wen). Electrical Power and Energy Systems 46 (2013) 175–183 Contents lists available at SciVerse ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes