The static VAr compensator (SVC), controllable series compensator (CSC) and phase shifter (PS) are three of the options of power electronic devices, referred to as FACTS (flexible AC transmission systems) devices. They are becoming of increasing importance in suppressing power system oscillations and improving system damping. In this paper, a unified model of a power system installed with these three FACTS devices is established. Their effectiveness in suppressing power system oscillations is investigated by analysing their damping torque contributions to the power system. The work in this paper relies on the theoretical analysis of a general single-machine infinite-bus power system where the objective is to present an insight into the operation of the damping control of the FACTS devices.

A unified model for the analysis of FACTS devices in damping power system oscillations. I. Single-machine infinite-bus power systems

A method is proposed in this paper to select the input signals for both single and multiple flexible ac transmission system (FACTS) devices in small and large power systems. Different input-output controllability analyses are used to assess the most appropriate input signals (stabilizing signal) for the static var compensator (SVC), the static synchronous compensator (SSSC), and the unified power-flow controller (UPFC) for achieving good damping of interarea oscillations. The study presented in this paper is carried out on one small system with one FACTS device at a time; and one large system equipped with the SVC, the SSSC, and the UPFC.

Choice of FACTS device control inputs for damping interarea oscillations

This paper proposes a new control strategy of shunt flexible ac transmission system (FACTS) devices to improve the first swing stability limit of a simple power system. It is shown that the speed based bang-bang control (BBC) is unable to use the entire decelerating area in maintaining stability. The proposed control strategy improves the stability limit first by maximizing the decelerating area and then fully utilizing it in counterbalancing the accelerating area. This requires to continue the operation of shunt FACTS devices at full capacitive rating until the machine speed reaches a reasonable negative value during the first return journey. Afterwards, the control can be switched to continuous type to improve system damping in subsequent swings. The proposed control strategy is then applied to both static var compensator and static synchronous compensators placed in a single machine infinite bus system. The same control strategy is also used for some faults in a multimachine system. In both the systems, it is found that the proposed control can provide significantly higher stability limit than that of the BBC. The mechanism of improving the stability limit is also described.

Improvement of first swing stability limit by utilizing full benefit of shunt FACTS devices

In recent years, power demand has increased substantially while the expansion of power generation and transmission has been severely limited due to limited resources and environmental restrictions. As a consequence, some transmission lines are heavily loaded and the system stability becomes a power transfer-limiting factor. Flexible AC transmission systems (FACTS) controllers have been mainly used for solving various power system steady state control problems. However, recent studies reveal that FACTS controllers could be employed to enhance power system stability in addition to their main function of power flow control. The literature shows an increasing interest in this subject for the last two decades, where the enhancement of system stability using FACTS controllers has been extensively investigated. This paper presents a comprehensive review on the research and developments in the power system stability enhancement using FACTS damping controllers. Several technical issues related to FACTS installations have been highlighted and performance comparison of different FACTS controllers has been discussed. In addition, some of the utility experience, real-world installations, and semiconductor technology development have been reviewed and summarized. Applications of FACTS to other power system studies have also been discussed. About two hundred twenty seven research publications have been classified and appended for a quick reference.

Power system stability enhancement using facts controllers: a review

This paper presents a method to seek the optimal location of several static Var compensators (SVCs) in a power system based on their primary function. Taking advantages of the flexible ac transmission system (FACTS) devices depends largely on how these devices are placed in the power system, namely, on their location and size. In addition to their primary function, the supplementary damping control action can be also added, and how to utilize their control capabilities effectively as stabilizing aids is becoming very important. In this paper, power system stability is used as an index for optimal allocation of the controllers. First, several SVCs are placed optimally based on modal analysis and genetic algorithm in a power system. After placing the SVCs based on their primary functions, the most appropriate input signal for supplementary controller is also selected. The frequency response characteristics of the system for all located SVCs are determined in selecting the best input signals.

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Placement of SVCs and Selection of Stabilizing Signals in Power Systems

A theory for analyzing power system damping enhancement by application of static VAr compensators (SVCs) has been developed using the equal area criterion. Some fundamental issues, such as the effect of SVCs on a power system, how to control an SVC to improve system damping, and the differences between continuous and discontinuous control of SVC reactive power to achieve the maximum damping improvement, are discussed. A discontinuous SVC reactive power output at discrete points is determined from the power deviation on a transmission line. Time-domain simulations of the application of this approach to a one-machine system to increase swing oscillation damping and to a four-machine system to increase the damping of an interarea oscillation mode demonstrate that the theory and method can be applied to solve practical power system damping problems. >

Application of static VAr compensators to increase power system damping

The simulation of power system electromechanical transient phenomena is highly dependent on the knowledge and model of special domain. For this reason, traditional parallelization of the simulation must be coupled with concrete algorithm and code. In this paper, a parallelized electromechanical transient simulation program is proposed based on the open-source simulation engine called InterPSS and general open object-oriented modelling framework. The correctness and effectiveness of this framework have been verified by a large-scale simulation case.

https://doi.org/10.1088/1742-6596/2195/1/012049

E.-Z. Zhou

Papers

Application of static VAr compensators to increase power system damping

Parallel Simulation of The Electromechanical Transient Phenomena of Power System via Modern Software Development Technique