Dynamic stability enhancement of a multimachine electric power system using STATCOM

Flexible AC Transmission System (FACTS) controllers are advanced power electronic devices employed in electrical power systems to enhance system stability, reliability, and power transfer capabilities. These controllers enable dynamic and flexible control of various transmission parameters such as voltage, current, impedance, and phase angle, thereby improving the overall power system performance. FACTS devices are broadly classified into series, shunt, series- series, and series-shunt configurations, each designed to manage reactive power and regulate voltage either by injecting voltage in series or current in shunt with the transmission line. Well-known FACTS devices include Static Var Compensators (SVC), Static Synchronous Compensators (STATCOM), Thyristor Controlled Series Capacitors (TCSC), Static Synchronous Series Compensators (SSSC), and Unified Power Flow Controllers (UPFC), each serving specific roles in power flow control, voltage regulation, and transient stability enhancement. The integration of these controllers provides significant benefits such as increased transmission line capacity, improved voltage stability, minimized transmission losses, and damping of power system oscillations. They are capable of rapid response during transient disturbances, effectively mitigating voltage collapses and enhancing system resilience against faults and contingencies. FACTS controllers not only improve steady-state operational parameters but also address dynamic stability and transient conditions, enabling power systems to operate closer to their stability limits while maintaining security. Their deployment helps avoid costly infrastructural expansions by optimizing existing transmission assets, which is critical given environmental and economic constraints. Recent advances in semiconductor technologies and control algorithms have made FACTS devices more reliable, efficient, and adaptable to modern grids, including renewable integration and deregulated power markets. In summary, FACTS controllers play a vital role in modern power systems by providing flexible, efficient, and reliable solutions for power flow management, voltage control, and system stability enhancement, thereby supporting the evolving demands of today's complex electrical networks.

One of the technical solutions for improving the stability of power system is incorporation of Static Synchronous Compensators (STATCOM) and Static Synchronous Series Compensator (SSSC) controllers. However, the impact of hybridized STATCOM and SSSC on the generator damping stability of the power system to improve the post disturbance recovery voltages of the generator is necessary. Thus, in this study, hybridized model of STATCOM and SSSC controllers were incorporated on the Nigerian 31-bus power system to improve the system generator damping stability during disturbance. Transient stability of electrical power system with contingency was performed using swing equations technique. Line-Voltage Stability Index (L-VSI) technique was employed to determine the critical load bus for the placement of the controllers. Hybridized model of the STATCOM and SSSC was developed and incorporate into the selected load buses and its impact on stability of the generator oscillation damping was examined. Simulation was done in MATLAB R2023a. The generator damping ratio, total active power losses and total cost of controllers were determined. Results verified the effectiveness of hybridized model of STATCOM and SSSC controllers in improving the stability of power generator oscillation damping. Keywords : STATCOM, SSSC, Line-Voltage Stability Index, Contingency, Generator Oscillation Damping, Power Loss. DOI: 10.7176/NCS/15-04 Publication date: February 28 th 2025

This paper represents, the enhancement of power system stability by coordinating control design of power system stabilizer (PSS) and static synchronous series compensator (SSSC). The coordinated controller's parameters are formulated as an optimization problem and to search for such optimal parameters firefly (FF) algorithm is used in both cases of single machine infinite bus and multi machine power system(MMPS). The coordinately control design of power system stabilizer and PID based SSSC based controller uses speed deviation as input signal. The dynamic performance of the proposed technique is obtained under different loading conditions and different position of fault conditions. The effectiveness and robustness of coordinated design approach is discussed to improve the damping of power system oscillation and hence stability of power system.

Inter Area Oscillations amounting to a major portion of the class of low frequency oscillations, are detrimental to the dynamic stability of the present day power system. Power system stabilizer (PSS) installed throughout the system aids in mitigating such oscillations. Static synchronous compensator (STATCOM) based damping controllers installed in the system also provide oscillation damping apart from their intended purpose of reactive power compensation. Hence to improve the overall performance coordinated design of PSS and STATCOM is essential. The coordinated design of power system stabilizer (PSS) and static synchronous compensator (STATCOM) for mitigation of inter area oscillations is presented in this paper. The coordinated design is formulated as an optimization problem and particle swarm optimization (PSO) is employed for this design. Then the designed PSS and STATCOM are implemented in the test system and the response is analysed. The test system is simulated with and without Power system stabilizer and static synchronous compensator. The simulation results show that the coordinated design mitigates the inter area oscillations in an effective way.

An efficient and most famous tool to enhance damping of the power system low frequency oscillations is the conventional widely used lead-lag Power System Stabilizer (PSS). To achieve the desired level of robust performance under transient situation, selecting a suitable design method for optimal tuning of PSS parameters is very important in multi-machine power system. Because, it is a multimodal and difficult combinatorial optimization problem, this paper presents a novel parameter automation strategy for Particle Swarm Optimization (PSO) called PSO with Time-Varying Acceleration Coefficients (PSO-TVAC). This optimization method has a strong ability to successfully control both global and local search in each iteration process for considerably increasing the probability of finding the global optimum solution. The PSO-TVAC algorithm is applied to optimal tuning PSS parameters problem in order to reduce the PSS design effort and find the best possible solution within a reasonable computation time. For this reason, the robustly selection of PSSs parameters is converted as an optimization problem based on the time domain-based objective function under different operating conditions. The robustness of the proposed method is demonstrated on a multi-machine power system in comparison with the classical PSO and conventional method based designed PSSs. It is shown through the nonlinear time domain simulation and some performance indices for a wide range of loading condition. The analysis of the results shows that the improved PSO-TVAC is not only very effective but also provides an excellent ability for damping low frequency oscillations and greatly enhance the dynamic stability of the power system. Moreover, the proposed PSO-TVAC algorithm is superior than that of the classical PSO one in terms of accuracy, convergence and computational effort. Key words: Power system stabilizer (PSS) design, particle swarm optimization, power system dynamics, time-varying acceleration coefficients.

In electromechanical oscillation damping within power system, power system stabilizers (PSSs) are often deployed. However, a PSS is less effective in damping interarea oscillation and is limited by changes in network configuration due to weak tie-lines and load variations. Consequently, this paper presents a wide-area coordination approach that damps interarea oscillations using FACTS devices and phasor measurement units. We selected a static synchronous compensator (STATCOM) and static series synchronous compensator (SSSC) for realistic power system interarea oscillation damping. The performance of the coordinated FACTS installed in a power system depends on their suitable locations, sizes, tuned parameters, and remote input signal selection. Hence, we formulated a multiobjective problem to provide the STATCOM and SSSC's optimal solutions using multiobjective particle swarm optimization. In addition, we employed a participation factor to select suitable generator speed deviations as the wide area stabilizing signal. The proposed approach was tested on different configurations of the Kundur $2$-area $4$-machine test system within MATLAB and Psat environments. The outcome of the nonlinear simulation proved that the multimachine power system stability was enhanced.

In this paper, a novel method is developed for designing the output feedback controller for Static Synchronous Series Compensator (SSSC). In the proposed method, the problem of selecting the output feedback gains for the SSSC controllers is changed into an optimization problem with a time domain-based objective function.Then, it is solved by using the particle swarm optimization (PSO) algorithm that has a strong ability to find the most optimistic results. Only local and available state variables are used as the input signals of each controller for the decentralized design. Therefore, the designed SSSC controller has a simple and easy-to-implement structure. The performance of the proposed controllers is evaluated for both single-machine infinite-bus (SMIB) power system and multi-machine power system. Then, to show the robustness and effectiveness of proposed design approach, the results are presented over a wide variety of system configurations, loading conditions, and disturbances. Analyzing the results reveals that the designed PSO-based output feedback SSSC damping controller has a strong ability in damping power system oscillations. Furthermore, analyzing system performance under different operating conditions shows that the ψ-based controller is superior to the m-based controllers.

El aumento de la demanda en los distintos sistemas eléctricos de potencia (SEP) tiene un impacto negativo en la estabilidad de la tensión, la confiabilidad y la calidad del suministro eléctrico. El perfil de tensión disminuye cuando las unidades de generación no son capaces de suministrar potencia reactiva al sistema eléctrico en los momentos que se requiere. Con el desarrollo de la electrónica de potencia y los complejos sistemas de control, se han podido introducir dispositivos de sistemas flexibles de transmisión de corriente alterna (FACTS, del inglés Flexible Alternating Current Transmission System). En este artículo se analiza en detalle el impacto que genera la introducción de un tipo de FACTS que permite la compensación de potencia reactiva en el SEP. Además, se analizará una metodología para decidir la capacidad del compensador síncrono estático (STATCOM, del inglés Static Synchronous Compensator) y su ubicación óptima con la ejecución de flujos de potencia continuos (FPC). Finalmente, se estudiará el impacto positivo de la instalación de un control estabilizador de potencia (PSS, del inglés Power System Stabilizer) para asegurar la estabilidad de tensión en el SEP. Este artículo se desarrolla utilizando el sistema base IEEE de 14 barras bajo dos modelos matemáticos para el cálculo del flujo de potencia desarrollados en el software Matlab, que son: i) utilizando las ecuaciones de balance de potencia y ii) Newton Raphson con el toolbox de MATLAB (PSAT, del inglés Power System Analysis Toolbox).

One of the key aspects in the development of power engineering all over the world is the use of distributed small-scale generation. This is both based on fuel carbon resources with a synchronized connection between sources when they are connected to the electric power grids and renewable energy sources operated in the electrical grid via frequency converters (electronic generation). The latter brings an inevitable broad use of inverters in available AC power systems. The objectives of this paper are numerous. First is the desire to study the effect of electronic generation on modes and stability of current electrical grids and electrical power systems. Another objective is to establish requirements for electronic generation control that lets us minimize actions on relay protection coordination and automation upon the integration of electronic generation in power grids. A final objective is to increase the reliability of general electrical modes. This article shows the outcomes of the study on the statical aperiodic stability of the electrical power system upon the integration of electronic generation, requirements for its statical characteristics, and the control when operated within the electrical power system.

This paper presents the application of Fuzzy Logic Controller (FLC) for Thyristor Controlled Series Capacitor (TCSC) to enhance over all stability of electric power systems. The proposed hybrid controller combines the advantages of FLC and a conventional PI controller. In this work, we consider Single Machine Infinite Bus (SMIB) system installed with Power System Stabilizer (PSS) and Fuzzy-PI based TCSC Controller. In order to test effectiveness of these controllers, simulations are carried out in different loading conditions under a symmetrical three-phase short circuit fault at generator terminals. The response of Fuzzy-PI controller is compared with that of the PI controller. The simulation result shows that the Fuzzy-PI controller has outstanding operation in fast damping of power system oscillations.

In this study, a static synchronous series compensator (SSSC) is used to investigate the effect of this device in controlling active and reactive powers as well as damping power system oscillations in transient mode. The SSSC equipped with a source of energy in the DC link can supply or absorb the reactive and active power to or from the line. Simulations have been done in MATLAB/SIMULINK environment. Simulation results obtained for selected bus-2 in two machine power system shows the efficacy of this compensator as one of the FACTS devices member in controlling power flows, achieving the desired value for active and reactive powers, and damping oscillations appropriately.

Static synchronous compensators (STATCOMs) have been widely used for voltage support over the past decade, to improve power quality and voltage stability. However, STATCOMs are limited in their ability to improve the system stability margin due to their restricted capability for delivering real power. Super capacitors are devices which can store significant amounts of energy, and are able to quickly release it. With the application and development of the super capacitor energy storage system (SCESS), energy storage technology has been greatly improved in modern power systems. The SCESS plays an important role in improving the operation stability of a power system. The aim of this work is to investigate how super capacitor based energy storage technology can be used to enhance the capability of STATCOM units to maintain a high quality of distribution voltage and improve the system stability of a grid connected photovoltaic system with a super capacitor as the energy storage device. In particular, a grid connected photovoltaic system constituted by photovoltaic and super capacitor sources and STATCOM is simulated in SIMULINK along with a DC to DC buck boost converter using MPPT. The simulation results reflect that system stability was enhanced by the use of the proposed strategy when the system gets affected by different types of fault. The designed system offers a preferable reference for applications of the STATCOM with SCESS in the field of regeneration energy and stability enhancement of power system.

A number of techniques have been proposed to dampen the power system oscillations in the electric power systems. Flexible alternating current transmission system (FACTS) devices are becoming one of them. Among the FACTS family, the static synchronous compensator (STATCOM), a shunt connected FACTS device, has been widely used to provide smooth and rapid steady state, limit transient voltage, and improve the power system stability and performance by absorbing or injecting reactive power. However, the influence ability depends on its placement, control signal, and place of receiving-signal in the network. In order to satisfy these issues, this paper proposes a method for optimal setting and signal position of the STATCOM into the multi-machine power systems with the aim for damping the electromechanical oscillations. This method is developed from the energy approach based on Gramian matrices considering multiple tasks on the Lyapunov equation, in which the observability Gramian matrix is used to seek an optimal location for STATCOM placement. The another is the controllability one used to determine the best local input signal placement that is chosen as a feedback signal for the power oscillation damping (POD) of STATCOM. In addition, the Krylov-based model reduction method is introduced to shorten the calculation time. The proposed method has been verified on the IEEE 24-bus system by analyzing the small-signal stability to search several feasible placements, and then the transient stability is analyzed to compare and determine an optimal placement through testing various cases. The obtained result is also compared with other optimal method.

Guest Editorial: Situational awareness of integrated energy systems

Comparing strategies to damp electromechanical oscillations through STATCOM with multi-band controller