Prony analysis and modeling of a TCSC under modulation control

The control of reactive power in any transmission network is important to ensure voltage stability of the entire power grid. Flexible AC Transmission Systems (FACTS) have proven to be efficient in providing controllability to reactive power for voltage stability management. However, the performance of the FACTs devices largely depends on the installation location. A fuzzy logic technique for finding the optimal location for the Thyristor Controlled Series Capacitor (TCSC) and Static Var Compensator (SVC) FACTS devices with specific security indices is proposed in this paper. The proposed indices for SVC placement are the Loss Sensitivity Factor (LSF) and critical voltage, while the considered indices for TCSC placement are the loss sensitivity factor (LSF) and line stability index (LSI). The indices are fuzzified to obtain a suitability index which determines the suitable line(s) and node(s) accordingly. The proposed approach is implemented on the IEEE 30 bus network. The SVC reduced the overall transmission loss by 1.6%, while the TCSC reduced the transmission loss by 4.94 %. The loading margin also improved by 24.87% and 2.92% using SVC and TCSC, respectively. The voltage profile also remained close to 1 p.u under varying load conditions. The results indicate the effectiveness of the proposed technique at reducing transmission loss, improving voltage stability and improving voltage profile simultaneously.

Adaptive RTRL based neurocontroller for damping subsynchronous oscillations using TCSC

This paper deals with optimal location of Flexible AC Transmission system (FACTS) device like Thyristor Controlled Series Capacitor (TCSC) by performing Optimal Power Flow (OPF) and sensitivity based methods. The OPF is performed on IEEE-14 bus system by minimizing the total system cost with an iterative procedure. As the number of buses increases the evaluation of the optimal location of TCSC becomes difficult because the complexity of the method based on OPF increases. Whereas the sensitivity based method may be easy to use even for the complex system. The above methods are performed in MATLAB and the required optimization is done in GAMS.

In this paper, multi – type Flexible AC Transmission System (FACTS) devices are optimally located for enhancing the loadability of an existing power network within the security margins. Line Stability Index is used to determine the critical lines of the system in increased loading of transmission lines and is used to determine the optimal location of FACTS devices. Differential Evolution Algorithm (DE) is used to determine the optimal location and control parameter settings of the FACTS devices. Among the various FACTS devices, Unified Power Flow Controller (UPFC) and Thyristor Controlled Series Capacitor (TCSC) are chosen and modeled for steady state studies. IEEE- 30 bus test system is used for simulation studies and the results are compared with Genetic Algorithm (GA) to show the advantage and feasibility of the DE approach. Further the results demonstrate that the system loadability can be increased by optimal location and control parameter settings of the multi – type FACTS devices.

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

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 systems are generally required to operate near their maximum capacity. Thus, there is an increased focus on improving real power system capacities through the installation of novel devices, including the Flexible AC Transmission Systems (FACTs). This paper discusses the optimal incorporation of thyristor-controlled series capacitor (TCSC) in the 400 kV Baghdad grid of the Iraqi network as a suggested method to control the power transfer of a transmission line (TL) and suppress Sub-Synchronous Resonance (SSR). The MATLAB 2019 simulation is executed utilizing the phase angle as an index to select an appropriate TCSC location. Nine places were chosen based on eigenvalues, and three suitable places were determined, where 0.5< Xc/Xl <2. The Baghdad city 400 kV is examined by applying PSS/E 34 software with the series TCSC connected at each of the three selected locations, thus three distinct cases are studied. The results reveal that the TCSC connection between 16428 4BGE and 16419 4BGS, where the value of (Xc/Xl) =1.46, was the optimal place where the series TCSC connection is conducted. From the results, it can be concluded that the least Xc/Xl value indicates the better the control of frequency and voltage, as well as the power losses in TLs reduction are higher.

ABSTRACTIn the present work, symbiotic organism search (SOS) algorithm is applied for the solution of optimal reactive power dispatch (ORPD) problem of power system considering flexible AC transmission system (FACTS) devices. The proposed method is tested and examined on modified IEEE 30 bus test system with two types of FACTS devices namely thyristor-controlled series capacitor (TCSC) and thyristor-controlled phase shifter (TCPS), placed at some strategic locations. In this study, ORPD problem has been formulated as single objective, constrained optimization problem that aims to reduce active power loss or total absolute voltage deviation individually. The formulation for conventional OPRD problem is evaluated by considering the settings of control parameters and maintaining the constraints of the FACTS devices as an additional entity. The effectiveness of the proposed method is analysed and compared to the results offered by some other optimization methods. The outcomes of the present work prove the potential of the SOS algorithm in solving ORPD problems of the power system incorporating FACTS devices.

The Thyristor Controlled Series Compensator (TCSC) and Static Var Compensator (SVC) are variable impedance Flexible AC Transmission Systems (FACTS) Controllers. A combination of the TCSC and the SVC installation is proposed to acquire superior performance for the power system. The coordination between the two pieces of equipment is designed with the SVC treated as the supplement of the TCSC. When operation of the TCSC is constrained by the inherent limitation of equipment, such as due to the firing-angle limitation of the thyristors, the adjustable SVC can supply the auxiliary support to improve the overall performance. The voltage and angle stability margins can be greatly improved with the compatible control schemes of the TCSC and the SVC.

Fractional order phase lead-lag controller (FOPLC) is a generalization of classical phase lead-lag controller (CPLC) using fractional calculus. Nowadays, fractional order controllers (FOC) have found wide applications in various aspects of power system control and operation. In this paper, FOPLC are used in structure of flexible ac transmission system (FACTS) based frequency stabilizer to enhance the dynamic performance of automatic generation control (AGC) system. So, Thyristor controlled series capacitor (TCSC) based damping controller with FOPLC structure is proposed in coordination with secondary integral load frequency controller (LFC). The controller is optimized via an improved particle swarm optimization (IPSO) algorithm. The dynamic performance of the proposed controller is compared with CPLC using eigenvalue analysis and time domain simulations. An interconnected multi-source realistic power system with TCSC in series with the tie-line is investigated considering the nonlinearity effects of generation rate constraint (GRC) and governor dead band (GDB). Simulation results reveal that FOPLC based TCSC damping controller achieves superior dynamic performance under various load perturbation patterns in terms of decreased performance index, settling time and amplitude of oscillations. Furthermore, the robustness of the proposed controller has been tested for large uncertainties in system parameter and loading condition.

Flexible AC Transmission Systems (FACTS) play a vital role in enhancing the stability, efficiency, and reliability of modern power systems. With the increasing complexity of power grids due to the integration of renewable energy sources, effective control of power flow, voltage regulation, and stability improvement are critical challenges. FACTS devices, such as Static Synchronous Compensator (STATCOM), Unified Power Flow Controller (UPFC), and Thyristor- Controlled Series Capacitor (TCSC), offer advanced solutions to mitigate these challenges by providing dynamic voltage control, reactive power compensation, and congestion management. This paper presents a comprehensive analysis of various FACTS devices, focusing on their control strategies, applications, and impact on improving power system performance. Simulation results demonstrate the effectiveness of FACTS devices in maintaining voltage stability, optimizing power flow, and minimizing transmission losses, ultimately contributing to a more efficient and resilient power grid.

The transmission of electrical energy using AC started at the end of the 19th century and replaced smaller existing local DC distribution systems. By extending local supply areas and providing energy transfer over longer distances various problems regarding mainly voltage control and stability were observed caused mainly by reactive power unbalances in the systems. Switched reactive power compensation (shunt capacitors, shunt reactors) were primarily used to control the steady state system voltages. Dynamic reactive compensation were based on rotating machines, eg synchronous condensors. In the mid 60's of the 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> century first static compensation devices, ie DC controlled reactors (mercury arc bulbs) and thyristor controlled devices (thyristor switched capacitors-TSC, thyristor controlled reactors-TCR) came up. Fast response times, lower losses and less maintenance requirements of thyristor controlled devices resolved the limitations of rotating machines and DC controlled devices. Evaluation of operating losses resulted more and more in the use of Static Var Compensators (SVC) which were built up by combinations of TCR and TSC branches. These shunt devices together with series connected devices TCSC (thyristor controlled series capacitors) provided a base for FACTS (Flexible AC transmission systems). FACTS allows transmission systems to be more efficiently used with regard to improved dynamic system voltage control on one side and higher power transfer capabilities on the other side. In AC transmission systems SVCs are installed presently with a total size of more than 100000 MVA. New power electronic devices (GTOs, IGCT, IGBT) were introduced to the FACTS market and allowed the use of current and voltage source converters (VSC) for providing fast reactive power compensation. With further improvement of controls, development of semiconductors and new arrangements of VSC technology to-days reactive power compensation is a key method to establish a reliable AC power transmission. The paper gives an overview from the early days of reactive power compensation towards the present transmission system situation. It compares early solutions with to-days devices, provides decisive factors for the steps in development of arrangements and discusses advantages of the present devices.

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

This paper investigates potential of modified differential evolution (MDE) algorithm, to find solution for optimal power flow (OPF) problem of power system. The performance of the proposed MDE algorithm is experienced on the modified IEEE-30 bus test systems integrating flexible ac transmission systems (FACTS) devices, that is, thyristor controlled phase shifter (TCPS) and thyristor controlled series capacitor (TCSC) at preset locations. The OPF problem of the present work is formulated with five different objective functions viz. (a) fuel cost (with valve point effect) minimization, (b) power transmission losses minimization, (c) emission reduction (d) fuel cost (without valve point effect) minimization and (e) minimization of combined economic and environmental cost. The proposed implementation exploits MDE, resulting in a much shorter execution time while retaining the best possible solution of OPF problem.