Coordinated design of PSS and TCSC controller for power system stability improvement

In this paper an Optimization based linear control design method is used to achieve a coordinated design of Power System Stabilizer (PSS) and Thyristor Controlled Series Capacitor (TCSC) for power system damping improvement with pre specified control design requirements. The settling time is considered as main performance criteria in time domain specification and gain and phase margins for frequency domain specifications. The main objective of the coordination of controllers is to improve the global stability through damping of oscillations by improving the damping ratio of the system and minimizing the settling time of the system response. Thus coordination increases the reliability of the system and maintains the required damping even one or more controllers are out of service and hence reduces the need for additional controller. Optimization based linear control design is used to determine the optimal gain and time constant setting of lead-lag controller parameters for PSS and TCSC. The coordinated PSS and TCSC controller is tested in the Single Machine Infinite Bus Power System (SMIB). Simulation is carried out using Matlab2011b. From the time domain simulation results it is observed that oscillations are damped out, settling time is reduced and damping ratio is improved. From bode plot it is inferred that gain and phase margin of the system is further improved to satisfy the system requirements. In the overall analysis, optimization based linear control design implemented for the coordination of PSS and TCSC controller satisfies the practical requirements of the power system oscillation damping problem, also shift the eigen values to the left half of the s-plane as far as possible and hence enhances the overall system stability

A single machine-infinite-bus (SMIB) system including the interline power flow controllers (IPFCs) and the power system stabilizer (PSS) controller is addressed. The linearized system model is considered for investigating the interactions among IPFC and PSS controllers. To improve the stability of whole system again different disturbances, a lead-lag controller is considered to produce supplementary signal. The proposed supplementary controller is implemented to improve the damping of the power system low frequency oscillations (LFOs). Imperialist optimization algorithm (ICA) and shuffled frog leaping algorithm (SFLA) are implemented to search for optimal supplementary controllers and PSS parameters. Moreover, singular value decomposition (SVD) method is utilized to select the most effective damping control signal of IPFC lead-lag controllers. To evaluate the system performance, different operating conditions are considered. Reponses of system in five modes including uncoordinated and coordinated modes of IPFC and PSS using ICA and SFLA are studied and compared. Considering the results, response of system without controller shows the highest overshoot and the longest settling time for rotor angel at the different operating conditions. In this mode of system, rotor speed has the highest overshoot. Rotor angel in the system with only PSS includes lower overshoot and oscillation than system without controller. When PSS is only implemented, rotor speed deviation has the longest settling time. Rotor speed deviation in the uncoordinated mode of IPFC and PSS shows lower overshoot than system with only PSS and without controller. It is noticeable that in this mode, rotor angel has higher overshoot than system with only PSS. The superiority of the suggested ICA-based coordinated controllers is obvious compared with SFLA-based coordinated controllers and other system modes. Responses of coordinated PSS and IPFC SFLA-based supplementary controllers include higher peak amplitude and longer settling time compared with coordinated IPFC and PSS ICA-based controllers. This comparison shows that overshoots, undershoots and the settling times are reduced considerably in coordinated mode of IPFC based controller and PSS using ICA. Analysis of the system performance shows that the proposed method has excellent response to different faults in power system.

In this paper, the coordinated operation of conventional power system stabilizer (CPSS) and thyristor controlled series capacitor (TCSC) is studied. The analysis of mode controllability is used to select the effective location for TCSC. The performance of TCSC equipped with a phase lead-lag controller is investigated. The controllers design problem is formulated as an optimization problem. The genetic algorithm (GA) is used to search for optimal settings of controller parameters. A coordinated control scheme is applied to a three machine nine bus power system. The proposed control scheme is tested under different loading conditions and analysis reveals that the coordinated control of CPSS and TCSC equipped with lead-lag controller gives better dynamic performances as compared to with only CPSSs.

In this paper, the Authors present the designing of power system stabilizer (PSS) and static var compensator (SVC) based on chaos, particle swarm optimization (PSO) and shuffled frog leaping (SFL) Algorithms has been presented to improve the power system stability. Single machine infinite bus (SMIB) system with SVC located at the terminal of generator has been considered to evaluate the proposed SVC and PSS controllers. The coefficients of PSS and SVC controller have been optimized by Chaos, PSO and SFL algorithms. Fi-nally the system with proposed controllers is simulated for the special disturbance in input power of genera-tor, and then the dynamic responses of generator have been presented. The simulation results show that the system composed with recommended controller has outstanding operation in fast damping of oscillations of power system and describes an application of Chaos, PSO and SFL algorithms to the problem of designing a Lead-Lag controller used in PSS and SVC in power system.

The stochastic nature of wind speed and nonlinear wind power behavior complicates stability, particularly under severe disturbances, where traditional controller designs are insufficient and lead to transient stability. This paper proposes a Power System Stabilizers (PSS), Power Oscillation Dampers (POD), and Thyristor Controlled Series Capacitors (TCSC) control strategy to enhance stability. Further, this study analyzed the intermittent nature of wind speed and the replacement of Synchronous Generators (SG) with Wind Farm (WF). The results show that the system is unstable and stable weekly without and with the control of PSS, POD, and TCSC. A coordinated controller of TCSC with POD is proposed to enhance the stability effectively and mitigate undamped fluctuations even under extreme conditions. The proposed coordinated controller demonstrates superior performance, robustness and reliability compared to standalone controllers. It has been validated and shown to be effective using the IEEE-11 bus model on the MATLAB/SIMULINK platform across diverse scenarios. This research presents a cohesive framework for addressing stability issues in WF-integrated power systems by streamlining methodologies and results.

Coordinated tuning of PSS and TCSC to improve Hopf Bifurcation margin in multimachine power system by a modified Bacteria Foraging Algorithm

In this paper, a hybrid method is proposed to damp frequency and power oscillations in the power system equipped with unified power flow controller (UPFC) and power system stabilizer (PSS) controllers. The method is robust with respect to operating point’s changes. This hybrid method consists of two stages: offline and online. In the offline stage, the coefficients of PSS and UPFC controllers for different operating points have been found by PSO algorithm; then in the second stage, online new fuzzy controller is proposed to select the best PSS and UPFC coefficients according to operating point. The proposed method is simulated for single machine infinite bus system-associated PSS and UPFC for three different operating points in MATLAB software, and results of proposed method simulation are investigated and compared with conventional PSS (CPSS) + UPFC, CPSS controllers. Simulation results show that the proposed method has a better performance.

This article investigates the impacts of dominant electromechanical oscillations on power systems with the participation of large inverter-connected power source systems. From first principles, new formulas are derived to estimate the contribution of synchronizing and damping torques as functions of the current power system operating condition. An extended Heffron–Phillips model accounting for these effects is then proposed and further simplified to be used for designing damping controllers in power systems having a large inverter-connected power source. A clear interpretation of the influence of inverter-connected power source generators on the synchronizing and damping torque is provided. By using the developed system model, the performance degradation of a power system stabilizer damping controller is assessed for a wide range of operating conditions. The results of computational studies performed on a test system show that the damping torque is adversely affected as the level of active power generation of the large inverter-connected power source is increased. Furthermore, the simulation results obtained indicate that there is an increased potential for amplifying adverse interacting effects between power system stabilizer controllers and other control system devices responding in the frequency range of the dominant electromechanical modes.

The dynamic effects of Static Var Compensator (SVC) and Thyristor-controlled Series Capacitor (TCSC) controllers on preventing voltage collapse are analyzed comprehensively by the small signal method. Hopf bifurcations caused by the interaction between SVC and dynamic load are investigated. The effects of the time constant selections for SVC and TCSC on voltage stability are also discussed. The authors show that TCSC is more effective than SVC in preventing voltage collapse. The steady-state stability limit of system is increased when SVC or TCSC is installed.

ABSTRACTReduction in fossil fuels and environmental aspect of them has led to the increasing need to the renewable energies such as wind power systems and other distributed generators (DGs) all over the world. With growing usage of wind energy in power systems, impact of wind generators on power system stability becomes more important than before. Since flexible alternating current transmission system (FACTS) devices have significant influence on system performance, especially series one to increase the stability of the system, in this work, thyristor-controlled series capacitor (TCSC) has been used. In this paper, also wind and other DGs as a hybrid energy production system are used and stabilization of power system using TCSC is investigated. Finally, it has been shown that, in addition to TCSC, other DGs are also used in maintaining the quality of supply, power system security and stability.

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.

Flexible Alternating Current Transmission Systems (FACTS) got in the recent years a well known term for higher controllability in power systems by means of power electronic devices. FACTS devices can effectively control the load flow distribution, improve the usage of existing system installations by increasing transmission capability, compensate reactive power, improve power quality, and improve stabilities of the power network. However, the location and settings of these devices in the system plays a significant role to achieve such benefits. This work presents the application of Real Coded Genetic Algorithm (RGA) and Particle Swarm Optimisation (PSO) for finding out the optimal locations, and the optimal parameter settings of multi type FACTS devices to achieve maximum system loadability (MSL) in the power system. The FACTS devices used are Thyristor Controlled Series Capacitor (TCSC) and Unified Power Flow Controller (UPFC). The reactance model of TCSC and the decoupled model of UPFC are considered in this work. The thermal limits of the line and voltage limits of the buses are taken as constraints during the optimization. Simulated Binary Crossover (SBX) and Non-uniform polynomial mutation are employed to improve the performance of the Genetic Algorithm used. Simulations are performed on IEEE 6 bus and 30 bus power systems. The obtained results are encouraging and show the effectiveness of RGA over PSO algorithm

Pole placement technique for PSS and TCSC-based stabilizer design using simulated annealing

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.

In this paper a robust method is presented for the combined design of STATCOM and Power System Stabilizer (PSS) controllers in order to enhance the damping of the low frequency oscillations in power systems. The combined design problems among PSS and STATCOM internal ac and dc voltage controllers has been taken into consideration. The equations that describe the proposed system have been linearized and a Fuzzy Logic Controller (FLC) has been designed for the PSS. Then, the Particle Swarm Optimization technique (PSO) which has a strong ability to find the most optimistic results is employed to search for the optimal STATCOM controller parameters. The proposed controllers are evaluated on a single machine infinite bus power system with the STATCOM installed in the midpoint of the transmission line. The results analysis reveals that the combined design has an excellent capability in damping a power system's low frequency oscillations, and that it greatly enhances the dynamic stability of power systems. Moreover, a system performance analysis under different operating conditions and some performance indices studies show the effectiveness of the combined design.