Transient stability improvement using Thyristor Switched Series Capacitor (TSSC) FACTS device

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.

Power consumption has risen dramatically in the last two decades, yet power generation and transmission have been severely hampered due to limited resources and environmental restrictions. Some transmission lines are essentially charged, and system stability becomes a limiting issue in energy transmission. A range of steady-state control problems has been addressed by flexible AC transmission system (FACTS) controllers. A FACTS is a system made up of static equipment used to transmit electrical energy via AC lines. Since the 1970s, FACTS devices have been utilized to create and improve the dynamic performance of modern power systems. This paper examines different techniques and tactics for coordinating control across FACTS controllers in multi-machine power systems in depth. The authors are certain that academics will find this survey study to identify important references in FACTS controller coordination.KeywordsFlexible alternating current transmission systemPower transfer limitingUnified power flow controllerOptimization methods

FACTS (flexible AC transmission systems) controllers are now widely available and they demonstrate many years of service experience. Their contribution to the control of a transmission system will become more valuable as the demands and varying applications of the system increase. Of the FACTS controllers in service today, the majority are static VAr compensators (SVCs), of which over 1000 give satisfactory service worldwide. Reviewing the available control packages and the experience of refurbishing an SVC, this paper offers some guidelines on the principles of design for replaceable control components that can deliver a renewable, and therefore ongoing, performance for a FACTS controller.

Voltage instability and voltage collapse have been considered as a major threat to present power system networks due to their stressed operation. It is very important to do the power system analysis with respect to voltage stability. Flexible AC Transmission System (FACTS) is an alternating current transmission system incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability. A FACTS device in a power system improves the voltage stability, reduces the power loss and also improves the load ability of the system. FACTS have made the power systems operation more flexible and secure. Amongst the several FACTS controllers, the Unified Power Flow Controller (UPFC) is most effective to improve the enhancement of voltage stability and reduces the power loss. This study investigates the application of Particle Swarm Optimization (PSO) to find sizing of Unified Power Flow Controller (UPFC) device to minimize the voltage stability index, total power loss, load voltage deviation, and cost of FACTS devices to improve voltage stability in the power system. A new model is proposed in this thesis to improve existing power-based model by using the Norton Equivalent Theorem. The proposed model can be integrated with the Equivalent Current Injection (ECI) power flow model easily. By ECI algorithm, it is much quickly and precisely to implement power flow calculations. Finally It is observed from the results that the voltage stability margin is improved, the voltage profile of the power system is increased and real power losses also reduced by optimally sizing UPFC device in the power system. Index Terms: Voltage stability, Unified Power Flow Controller (UPFC), Equivalent -Current Injection (ECI), Modified particle swarm optimization (MPSO)

This paper investigates the applicability of an integrated approach for the enhancement of voltage stability margin and there by the wind penetration of large wind integrated power systems. The proposed approach involves in two objectives; the identification of weak buses in the given power systems, enhancement of voltage stability margin of the weak buses and there by the wind penetration by optimal placement and tuning of Flexible AC Transmission System (FACTS) controllers. Multiple of one type of FACTS controller namely SVC is used in the current analysis for placement in suitable weak buses. Weak bus identification is carried out byconducting the tangentvectoranalysis. Voltage stability enhancement at high wind penetration is assessedby using the dynamic voltage security index, the index for accessing the proximity of voltage collapse under dynamic loadingconditions. Theoptimization of grid control parameters are carried out by using Particle Swarm Optimization (PSO) by incorporating FACTS Controllers. The developed algorithm have beentested on Wind integrated Kerala grid 25-bus practical system.

This paper presents a systematic procedure to design a decentralized wide area damping controller for the wind farms and Flexible AC Transmission System (FACTS) controllers in a smart grid considering uncertainties in the load parameters. The effect of uncertainties in load parameters on damping of inter-area modes of oscillations is investigated through the probability collocation method. A robust H1 output feedback controller is, then, designed for the uncertain fuzzy system by satisfying Linear Matrix Inequalities (LMIs), which are obtained from the original Bilinear Matrix Inequalities (BMIs), derived from the Lyapunov based stability criterion. The input and output signals for the proposed controller are selected based on a joint observability/controllability index. The input signals are wide area signals obtained from the Phasor Measurement Units (PMUs) and the output signals are fed to wind farm generators and the FACTS controllers. The input signal delay compensation is addressed in this work. The performance of the controller has been tested on New England 39 bus system developed on Real Time Digital Simulator (RTDS) and on a practical large Indian power system, under various operating scenarios and faults. Its effectiveness is also compared with a conventional power system stabilizer, local damping controllers, and an existing robust centralized wide area controller designed based on mixed H2/ H1 output feedback synthesis.

Adaptive algorithm for transmission line protection in the presence of UPFC

Impact of FACTS Controllers on the Dynamic Stability of Power Systems Connected with Wind Farms

Design and real-time implementation of a self-tuning flexible ac transmission system (FACTS) controller is illustrated for power oscillation damping. Although the system model is not required for self-tuning control design, it is shown to perform similar to a model-based design. For parameter estimation, the classical recursive least square (RLS) is supplemented by a random walk (RW) with a switched structure and compared to standard variable forgetting factor (VFF) approach. It is shown that the RW improves the accuracy and convergence of the estimated system parameters, which is critical to self-tuning control following large disturbances. The performance is validated in real time using a commercial real-time simulation platform. The control computation time is shown to be considerably less than the typical sampling time used for power oscillation damping applications demonstrating the feasibility of self-tuning FACTS controllers in practice.

This paper presents the modelling and simulation of Centurion electric power system using MATLAB/SIMULINK package. The basic system is tested under large and small disturbances to study the dynamic behaviour of the system and the stability margins associated with the different configurations of the system. The single-machine infinite bus (SMIB) power system model is considered, with the synchronous generator being represented by model 1 with both the generator main field winding and the damper winding in q-axis, and developed to evaluate the impact of power system stabilizer (PSS) with automatic voltage regulator (AVR) and flexible ac transmission system (FACTS) based controllers on power system stability. As a suggested solution to increase stability margins of the system, PSS with AVR are installed in the network. FACTS controllers are added, modelled and tested to validate the effectiveness on the different stability margins under both large and small disturbances.

The static synchronous compensator (STATCOM) is one of the flexible AC transmission system (FACTS) devices. The STATCOM and wide area measurement system (WAMS) are used in power systems. This paper describes the coordinated design of the wide area controllers and STATCOM controllers using a bacterial foraging algorithm (BFA). BFA is a new type of global optimization algorithm. The parameters of the controllers are optimized simultaneously by using the BFA to minimize the fitness function. The fitness function is the performance of the integral of the time-weighted squared error (ITSE). The fitness function is calculated by solving the differential equations. A 10-machine 39-bus new England system is a complex power system and is used to test the method of the coordinated design. The results show that the coordinated design of these controllers can improve the damping of the interconnected power system.

The impact of the wind generation on the power systems is no longer negligible if high penetration levels are going to be achieved. It is very important to boost the transfer capability of the transmission system while improving the utilisation of transmission assets to accommodate high penetration of wind power on the network. Hence, more sophisticated control schemes using advanced power electronic-based flexible AC transmission system (FACTS) controllers are required which will enhance voltage security and voltage stability control. This paper presents the impact of FACTS controllers on the dynamic stability of power systems connected with wind energy conversion systems. The wind farm model considered is a variable speed doubly-fed induction generator model. The dynamic simulation results yield information on 1 the impact of faults and wind speed changes on the performance of DFIG-based induction generators 2 the change in controllable parameters of the FACTS controllers following the faults and wind speed changes 3 transient rating of the FACTS controllers for enhancement of rotor speed stability of induction generators and angle stability of synchronous generators.

Voltage stability is an issue of prime importance in the present power system scenario since the demand for electric power is increasing drastically. Voltage instability may be due to a disturbance occurring at some location in the power system. The increase in active and reactive power loss along the heavily loaded transmission network is another undesirable effect of the same. In this paper a solution to this problem is put forward by using series connected flexible AC transmission system (FACTS) controllers, namely thyristor controlled series capacitor(TCSC) and static synchronous series compensator(SSSC). The main objective of this paper is to provide adequate compensation to reduce system losses and to improve the voltage profile of the system. The optimal location for installation of the FACTS device is found out using the line stability index Lmn and validated using power flow studies. The performance of the controllers are compared to find out the best one in terms of voltage stability enhancement and loss reduction. The test has been conducted in MATLAB/PSAT environment and the test system considered is the WSCC 9 bus system.

Chaotic krill herd algorithm for optimal reactive power dispatch considering FACTS devices

State estimation of power systems containing facts controllers