Thyristor Controlled Series Compensator Research Articles

Multi-Type FACTS Controllers for Power System Compensation: A Case Study of the Nigerian 48-Bus, 330 kV System

Flexible alternating current transmission system (FACTS) devices have provided proficient answers to power system instabilities faced in the systems operations today with very little infrastructural investment fund. This paper investigates the effects of the installation of the combination of two kinds of FACTS controllers; static VAR compensator (SVC) and thyristor controlled series compensator (TCSC) compared with the installation of SVC or TCSC alone in the system. Voltage magnitude profile, active and reactive power losses of the three scenarios were achieved in the Nigerian 48-bus power system network using power system analysis toolbox (PSAT) in MATLAB environment. Simulation results obtained without and with FACTS devices optimally placed using voltage stability sensitivity factor (VSSF), revealed that the percentage decrease of the net real and reactive power losses of the combined SVC and TCSC was the highest at 31.917% whereas that of the standalone SVC and TCSC stood at 19.769% and 30.863% respectively. This shows that in addition to their capabilities to maintain acceptable voltage profile, the combination of SVC and TCSC has better compensating effect as they mitigate against power losses which was observed in their high percentage decrease in power losses compared to the standalone FACTS devices.
 Keywords: FACTS, optimum location, PSAT, SVC, TCSC, VSSF

Adaptive Configuration Method of Low-Frequency Electromechanical Sampling Information in Building Electrical System

In order to enhance the reliability of the electrical systems in low frequency, an adaptive configuration method of low-frequency electromechanical sampling information based on thyristor controlled series compensation (TCSC) is designed. The electrical system is simplified to a linear invariant system, and a stochastic subspace identification (SSI) method is established by using the singular value decomposition principle to collect low-frequency electromechanical sampling information. The reference channel technology is introduced to design the reference channel covariance matrix to judge whether low-frequency information is generated and improve the efficiency of sampling information acquisition. The architecture and working principle of the controllable series compensation device are analyzed, and the test signal method is used to evaluate the low-frequency modes and the information required by the device among the electrical system regions of buildings. The alternative input signals are selected by comparing different input signal residue ratios. The TCSC device parameters are adjusted by the compensation residue phase method, so as to realize the adaptive configuration of different low-frequency electromechanical sampling information and ensure the stable operation of the electrical system. The experimental results show that the proposed configuration scheme can effectively improve the damping ratio of the system and has an excellent effect on suppressing the continuous oscillation under a low-frequency fault.

PERFORMANCE OF HIGH VOLTAGE TRANSMISSION LINE BASED ON THYRISTOR-CONTROL SERIES COMPENSATOR

This research aims to improve the steady-state performance of high-voltage power transmission lines, which is a significant challenge for the power system grid's safe and reliable operation. The research adopted Flexible Alternating Current Transmission System for electronic devices. The flexible alternating current transmission system technology will be used in this specific work as Thyristor-Controlled Series Compensators. Thyristor-controlled series compensator devices increase transmission systems' capacity and enhance the voltage profile by regulating transmission line reactance. Gravitational Search Algorithm is a meta-heuristic approach applied to find the optimum size and optimal location of thyristor-controlled series compensators in power systems. The gravitational search algorithm is used to solve the multi-objective and integrated optimum power flow problem in reactive energy management during normal and contingency operations. The results showed reduced voltage deviation, reduced active/reactive power losses, and increased transmission line reserves above thermal limits, in addition to reducing the installed cost and number of thyristor series compensators devices. The simulation part was created with MATLAB programming language and validated with MATPOWER software. Applied to IEEE 30 bus system and 400kV super high voltage grid system.

An adaptive cumulative sum based method for unblocking distance relays in TCSC compensated transmission lines

Fault detection in transmission lines with thyristor controlled series compensators (TCSC) can be challenging, in particular during power swing conditions. A reliable unblocking method based on the adaptive cumulative Sum (ACUSUM) is presented in this paper. This method alleviates the limitations of conventional methods and has the capability to detect all asymmetric and symmetric faults with high accuracy and speed. The proposed method measures the negative sequence of the current signal for fault detection. Two simulation case studies consisted of the single machine and infinite bus (SMIB) and the IEEE standard 9-bus and three machine systems are simulated in PSCAD/EMTDC to evaluate the proposed method. It is shown that the non-linear behavior of TCSC will not impact the accurate performance of this method.

Dynamic clustering-based model reduction scheme for damping control of large power systems using series compensators from wide area signals

This paper presents a new scheme of thyristor controlled series compensators (TCSC)-based damping controller for damping inter-area oscillations in bulk power systems based on a wide area measurement system (WAMS). In this regard, the proposed scheme provides an adaptive three-phase step through real-time working mode. In the first step, by proposing dynamic clustering-based technique, wide area signals evaluate the inter-area oscillations of the system which in a real-time procedure identify the corresponding oscillating areas. In the case of reducing the order of power systems through a set of aggregated coherent areas, the proposed scheme implements through the second step which utilizes as a damping controller for damping the inter-area oscillations. In this step, the wide area electromechanical signals use as input data through the proposed TCSC-based damping controller. The corresponding controlling signals consist of inter-area rotor angle (ΔδCOI) and inter-area speed deviation (ΔωCOI) evaluated through center of inertia (COI) frame. In the third step, at each time window (ΔT) through real-time working mode, the proposed scheme examines through a set of fault occurrences which based on online evaluations of the system dynamic responses, the controller parameters adjust adaptively. The proposed controller is an online and non-model-based scheme which properly reduces the system order through a set of coherent areas to provide proper damping performances of inter-area oscillations. The effectiveness of the proposed scheme evaluates through the Iran National Power Grid with the potential of two oscillating areas with proper damping performances for damping the unstable inter-area oscillations.

Ensuring Reliable Operation of Electricity Grid by Placement of FACTS Devices for Developing Countries

Flexible AC Transmission Systems (FACTS) are essential devices used for the efficient performance of modern power systems and many developing countries lack these devices. Due to the non-existence of these advanced technologies, the national grid remains weak and vulnerable to power stability issues that can jeopardize system stability. This study proposes novel research to solve issues of an evolving national grid through the installation of FACTS devices. FACTS devices play a crucial role in minimizing active power losses while managing reactive power flows to keep the voltages within their respective limits. Due to the high costs of FACTS, optimization must be done to discover optimal locations as well as ratings of these devices. However, due to the nonlinearity, it is a challenging task to find the optimal locations and appropriate sizes of these devices. Shunt VARs Compensators (SVCs) and Thyristor-Controlled Series Compensators (TCSCs) are the two FACTS devices considered for the study. Optimal locations for SVCs and TCSCs are determined by Voltage Collapse Proximity Index (VCPI) and Line Stability Index (Lmn), respectively. Particle Swarm Optimization (PSO) is employed to find the ideal rating for FACTS devices to minimize the system operating cost (cost due to active power loss and capital cost of FACTS devices). This technique is applied to IEEE (14 and 30) bus systems. Moreover, reliable operation of the electricity grid through the placement of FACTS for developing countries has also been analysed; Pakistan being a developing country has been selected as a case study. The planning problem has been solved for the present as well as for the forecasted power system. Consequently, in the current national network, 6.21% and 6.71% reduction in active and reactive power losses have been observed, respectively. Moreover, voltage profiles have been improved significantly. A detailed financial analysis covering the calculation of Operation Cost (OC) of the national grid before and after the placement of FACTS devices is carried out.

A magnetically controlled series compensation-fault current limiter

This paper presents a magnetically controlled series compensation-fault current limiter (MCSC-FCL) which is composed of a magnetically controlled reactor (MCR) and a compensation capacitor. The device is improved from the traditional thyristor-controlled series compensation (TCSC), which has the characteristics of small output harmonics and simple control. The traditional saturated iron-core reactor is improved to increase the adjustable range of output reactance. During the fault, the MCR is connected to the grid alone to limit fault current; when the grid is normal, MCR and capacitor are used in series compensation mode. It effectively improves the utilization rate of the traditional current limiter MCR. In order to verify the effectiveness of the proposed MCSC-FCL, this paper analyzes the control characteristics of reactor models with different air gap structures by JMAG finite element analysis software, and verifies the voltage regulation characteristics and fault current limitation capabilities on MATLAB/Simulink platform.

Optimal coordination of thyristor controlled series compensation and transmission expansion planning: Distributionally robust optimization approach

This paper proposes a distributionally robust optimization method for assessing economic benefits of transmission expansions with thyristor controlled series compensation devices. To accommodate the uncertainty of wind generations and electrical vehicle loads, a distributionally robust optimization method is proposed to use historical data instead of predefined distribution probabilities. In the proposed framework, firstly, a confidence set for unknown distributions are constructed based on the historical data. Then, based on worst-case distributions within a constructed confidence set, the optimal results of transmission expansion planning and allocation of thyristor controlled series compensation device are obtained. In order to take advantage of the flexible alternative current transmission devices (FACTS) in both economic and technical considerations, the optimal allocation of thyristor controlled series compensation is integrated into the transmission expansion planning. This requires AC-based transmission expansion planning model. AC power flow suffers from high computational complexity. To tackle this issue, the linearized AC power flow model is utilized. Furthermore, to solve the optimization problem, the combined technique including Bender's decomposition and cut-and-column are utilized. The numerical results on the Garver 6-bus and IEEE 118-bus systems demonstrate the effectiveness of the proposed method in comparison with scenario-based stochastic and robust optimization methods. Besides, the impacts of the thyristor controlled series compensation on total cost reduction has been investigated.

Generalized voltage estimation of TCSC-compensated transmission lines for adaptive distance protection

The variable performance of the thyristor-controlled series compensator (TCSC) system represents a vital challenge for conventional distance relays. Most existing algorithms are based on the measured data at two ends of the TCSC-compensated lines. However, some of single-end algorithms need to modify the distance relay for the series capacitor (SC) only. This paper introduces a generalized algorithm to estimate the voltage drop across the TCSC. The distance relay uses the estimated TCSC voltage drop for terminal voltage compensation. The second objective of the proposed algorithm is to estimate the conduction angle of the thyristor-controlled reactor (TCR) branch under different modes of operation. This algorithm is effective for different TCSC modes such as the capacitive or the inductive modes, in addition to the method of firing angle of synchronization current or voltage synchronization modes. The main benefit of the proposed algorithm is presenting a parameter-less distance scheme for TCSC-compensated transmission line. A 400-kV overhead transmission line test system is simulated in MATLAB/SIMULINK package® and the numerical modeling is implemented in the MATLAB® script in order to evaluate the proposed algorithm effectiveness. The proposed technique is tested under several stress conditions that may face the conventional distance relay. The results illustrate the effective performance of the proposed algorithm.

Improvement the voltage stability margin of Iraqi power system using the optimal values of FACTS devices

The detection of potential voltage collapse in power systems is essential to maintain the voltage stability in heavy load demand. This paper proposes a method to detect weak buses in power systems using two stability indices: the voltage stability margin factor (dS/dY) and the voltage collapse prediction index (VCPI). Hence, the paper aims to improve the voltage stability of Iraqi transmission grid by allocating FACTS devices in the optimal locations and optimal sizes. Two types of FACTS are used in this paper which are Thyristor controlled series compensator (TCSC) and static var compensator (SVC). The objective function of the problem is fitted using particle swarm optimization (PSO). The proposed method is verified using simulation test on Diyala-132 kV network which is a part of the Iraqi power system. The results observed that improvement the voltage stability margin, the voltage profile of Diyala-132 kV is increased and the power losses is decreased.

The estimation of transmission line loadability Based on Artificial Intelligence Algorithm & Voltage Stability Index

The continuous changes in electricity demand and supply are contributing to the disparity in quantities of power transferred between transmission networks, i.e. some lines are lightly loaded and others are overloaded. This presents a significant challenge to the secure and reliable operation of the power system. The current research is concerned with enhancing the loadability of electric transmission lines, that secure the increase in load demand through Flexible AC Transmission System (FACTS) injection. This paper is focused on the -Thyristor Controlled Series Compensator (TCSC), the optimum location of the TCSC was determined by applying two different techniques. The first technique was based on an artificial intelligence algorithm while the second technique was based on the level of voltage stability indices for all system lines. The optimal location is based on the fulfillment of multi-objective functions represented by an increase in the load capacity, reduce levels of the voltage stability index, the cost of installing the TCSC, and the voltage deviation. The IEEE-9 bus standard test system as a study case and MATLAB-programmes has been used for the analysis of the optimal power flow, and estimating the loadability of transmission lines without and with TCSC.

Application of multi-objective hybrid artificial bee colony with differential evolution algorithm for optimal placement of microprocessor based FACTS controllers

Increasing electricity demand, financial concerns for building new power stations have resulted in overloading, extreme power transfer, huge losses, reduced power eminence, consistency issues and voltage contour issues. To overcome these issues Flexible AC Transmission System (FACTS) controllers can be integrated into the transmission systems. Subsequently, it improves stagnant and vigorous enactment. Conversely, site, type and capacity of FACTS controllers have to be optimized to attain the aforesaid objectives. In this study, multiple objectives such as minimization of voltage deviation, losses, cost, and line loading index have been optimized using hybrid Artificial Bee Colony-Differential Evolution (ABC-DE). Three microprocessor controlled FACTS controllers for instance thyristor controlled series compensator (TCSC), static VAR compensator (SVC) and unified power flow controller (UPFC) have been placed optimally on IEEE 30 bus system. The outcomes of hybrid ABC-DE have been validated with the outcomes of particle swarm optimization (PSO). It implies that hybrid ABC/DE outperformed PSO for allocating FACTS controllers by optimizing multiple objectives concurrently.

Fault-tolerant finite-time fuzzy control for nonlinear power systems with time delays and actuator faults

To ensure the stability of nonlinear power systems with actuator faults and time delays, this study aims to design an adaptive fuzzy finite-time control scheme. To deal with this control issue, firstly, we propose an adaptive fault-tolerant finite-time controller using backstepping technique. To aid the controller design, fuzzy logic systems are applied to approximate the uncertain nonlinear terms without the prior information. Then, it is proved that the designed controller can ensure the stability in a finite time for the nonlinear power systems with actuator faults and time delays using Lyapunov–Krasovskii method. Finally, numerical simulations of a 4-machine power system with Thyristor Controlled Series Compensation (TCSC) illustrate the applicability of the proposed control methodology.

Online estimation of control parameters of FACTS devices for ATC enhancement using artificial neural network

The deregulated electricity sector needs an improvement in the Available Transfer Capability (ATC) towards the maintenance of power network at balanced condition and to utilize the system in effective manner. Independent System Operator (ISO) maintains the ancillary services by ensuring the reliability of the power system. One of the major functions of ancillary service provider is to maintain the voltage and power flow at stable level. To improve the ATC, both the line power flow and bus voltage profile have to be modified and it is taken care by the ISO. The major limiting criterion for ATC is bus voltage profile. It is well known that the device Thyristor Controlled Series Compensation TCSC which is one of the Flexible AC Transmission System (FACTS) devices can modify the line flow by adjusting the line reactance and Static VAR compensator (SVC) can improve the bus voltage profile by injecting reactive power to the bus. In this research, an Artificial Neural Network (ANN) based estimation of control parameter of FACTS devices such as TCSC and SVC for ATC enhancement is used. The proposed approach uses two different ANN network to find the different TCSC and SVC control parameters to improve the ATC values without violating its voltage constraints for real time transactions. The ANN algorithms such as Radial Basis Function (RBF) as well as Back Propagation Algorithm (BPA) were used to find the TCSC and SVC Parameters and the results are compared. The proposed methods are demonstrated through Reliability Test System (RTS) of IEEE 24 bus. The simulation output represents the suitability of the anticipated method for Real Time estimation of FACTS devices control parameter settings for ATC Enhancement.

Design of fractional evolutionary processing for reactive power planning with FACTS devices

Reactive power dispatch is a vital problem in the operation, planning and control of power system for obtaining a fixed economic load expedition. An optimal dispatch reduces the grid congestion through the minimization of the active power loss. This strategy involves adjusting the transformer tap settings, generator voltages and reactive power sources, such as flexible alternating current transmission systems (FACTS). The optimal dispatch improves the system security, voltage profile, power transfer capability and overall network efficiency. In the present work, a fractional evolutionary approach achieves the desired objectives of reactive power planning by incorporating FACTS devices. Two compensation arrangements are possible: the shunt type compensation, through Static Var compensator (SVC) and the series compensation through the Thyristor controlled series compensator (TCSC). The fractional order Darwinian Particle Swarm Optimization (FO-DPSO) is implemented on the standard IEEE 30, IEEE 57 and IEEE 118 bus test systems. The power flow analysis is used for determining the location of TCSC, while the voltage collapse proximity indication (VCPI) method identifies the location of the SVC. The superiority of the FO-DPSO is demonstrated by comparing the results with those obtained by other techniques in terms of measure of central tendency, variation indices and time complexity.

Study on the characteristics of secondary arc current of UHV high compensation degree TCSC line under the fine-tuning mode

Abstract In the transmission line, the series compensation device is often used to improve the transmission capacity. However, when the fixed series capacitor (FSC) is used in high compensation series compensation device, the stability margin cannot meet the requirements. Therefore, thyristor controlled series compensator (TCSC) is often installed in transmission lines to improve the transmission capacity of the line and the stability of the system. For cost considerations, the hybrid compensation mode of FSC and TCSC is often adopted. However, when a single-phase grounding fault occurs in a transmission line with increased series compensation degree, the unreasonable distribution of FSC and TCSC will lead to the excessive amplitude of secondary arc current, which is not conducive to rapid arc extinguishing. To solve this problem, this paper is based on 1000 kV Changzhi-Nanyang-Jingmen UHV series compensation transmission system, using PSCAD simulation program to established UHV series compensation simulation model, The variation law of secondary arc current and recovery voltage during operation in fine tuning mode after adding TCSC to UHV transmission line is analyzed, and the effect of increasing series compensation degree on secondary arc current and recovery voltage characteristics is studied. And analyze the secondary arc current and recovery voltage when using different FSC and TCSC series compensation degree schemes, and get the most reasonable series compensation configuration scheme. The results show that TCSC compensation is more beneficial to arc extinguishing under the same series compensation. Compared with several series compensation schemes, it is found that with the increase of the proportion of TCSC, the amplitude of secondary arc current and recovery voltage vary greatly. Considering various factors, the scheme that is more conducive to accelerating arc extinguishing is chosen.

THE IMPACT OF THE UNIFIED POWER FLOW CONTROLLER ON MAXIMIZATION OF LOADABILITY OF ELECTRIC POWER GRID

The building of additional transmission network to meet the demand of the ever-increasing load is expensive, and time consuming. An alternative to constructing new lines is the incorporation of the Flexible Alternating Current Transmission System (FACTS); in which a Unified Power Flow Controller (UPFC) is a member of the ménage, which can be modelled as a combination of Static Var Compensator and Thyristor Control Series Compensator. This study determines the optimal location of the UPFC by randomly adding loads to the existing transmission network until the Fast Voltage Stability Index of one of the lines is at a critical point. This is the vital line in which UPFC components are added. The sizing of the components of the UPFC is determined using Artificial Bee Colony algorithm. The IEEE 30-bus network is exploited as the test bed. The results obtained reveal that the optimal positioning and sizing of the UPFC for the purpose of maximizing loadability of the grid when load angles are assumed to be negligible are the same as when the load angles are considered. The loadability of the test bed when UPFC is not injected in the grid is 440.376 MW, whereas, it is 837.915 MW when the UPFC is optimally located and sized; and this represents 90.27 %. The sizes of the shunt and series components of the UPFC that assist in realizing this maximization are -0.2780 pu and 0.1000 pu respectively.

Enhancing Distance Protection of Long Transmission Lines Compensated With TCSC and Connected With Wind Power

Thyristor controlled series compensation (TCSC) is widely used in long transmission lines to mainly improve power transfer capability. However, TCSC produces complicated impedance that negatively affects distance protection operation. The wind energy generation system produces additional complexity to the distance protection performance due to the variation of wind speed and fault current level. This paper proposes an integrated scheme to change adaptively the settings of the Mho distance protection by shifting the relay characteristics considering the bad impacts of TCSC, wind power and fault resistance. The proposed scheme achieves its main stages starting from fault detection, until relay tripping decision procedure including online estimation for preliminary fault location, impedance of TCSC and fault resistance using limited communication requirements. By extensive MATLAB simulations, the performance of the proposed scheme is examined compared with the conventional Mho relays under different fault locations, fault inception angle, fault resistance, different wind power penetration, different wind speeds and different TCSC firing angles. The achieved results ensured that the proposed scheme improves significantly Mho distance relay operation and avoids under-reaching and over-reaching problems irrespective of the large shunt capacitance along the transmission line, and also without identifying the parameters of TCSC such as the capacitance, the inductance or the firing angle.

Congestion management with improved real power transfer using TCSC in 30 bus system

Secure operation and reliable utilisation of transmission lines is a challenging issue in deregulated power system. The scheduled power transactions are difficult due to the overloading of transmission lines in restructured power system as the electricity market has become more competitive. Due to congestion of transmission lines, the transfer of real power and the power system voltage profile are greatly affected in the power system. The aim of this research work is to increase the real power and the reactive power flowing in the lines of multibus system using thyristor controlled series compensator (TCSC). Real power transfer with reduced losses and improved voltage stability is an important factor in the present global scenario. This paper deals with the improvement of power flow in power transmission lines by series compensation device in 30 bus system with reduced congestion. The 30 bus system without and with thyristor controlled series compensation device (TCSC) is modelled and simulated and the results are presented. The simulation studies indicate a significant improvement in the real and the reactive power flow with the introduction of TCSC. The advantages of the proposed system include the smooth variations of the real and the reactive powers.

Sensitivity Based Congestion Management in a Deregulated Power System by Optimal Allocation & Parameter Setting of TCSC using Grey Wolf Optimization

In a deregulated power system as the power demand is increasing rapidly, with a limited power system framework, it is very difficult to transmit bulk power. This limitation is due to the thermal constraints of the transmission line. There is a need to increase the loadability of the line without hitting the thermal limits of the system. Thyristor Controlled Series Compensator (TCSC) is used in this paper to reduce congestion in the system by reducing losses and increasing the loadability of the lines. The sensitivity factor applied to optimally allocate TCSC is Disparity Line Utilization Factor (DLUF) and parameter setting is optimized using Grey Wolf Optimisation (GWO). The lines are sorted in terms of the degree of congestion with the help of LUF and then optimal location of TCSC is obtained using DLUF to minimize congestion. TCSC parameters are optimally calculated by the multivariable objective function applying GWO. The method is validated on IEEE 30 bus system. The congestion is reduced and the loadability of a line is increased by the algorithm used in this paper. Effects of congestion alleviation by proposed method are suitably demonstrated in this paper for reduced real and reactive power loss, reduced voltage deviation and incremented security margin of the test system. Results obtained by the proposed algorithm is establishing an upper hand over other state of art algorithms in terms of solution of problem formulated for congestion alleviation.