Thyristor Controlled Phase Shifter Research Articles

Multi-objective optimal power flow with FACTS devices

This paper presents multi-objective differential evolution to optimize cost of generation, emission and active power transmission loss of flexible ac transmission systems (FACTS) device-equipped power systems. In the proposed approach, optimal power flow problem is formulated as a multi-objective optimization problem. FACTS devices considered include thyristor controlled series capacitor (TCSC) and thyristor controlled phase shifter (TCPS). The proposed approach has been examined and tested on the modified IEEE 30-bus and 57-bus test systems. The results obtained from the proposed approach have been compared with those obtained from nondominated sorting genetic algorithm-II, strength pareto evolutionary algorithm 2 and pareto differential evolution.

Load frequency stabilization by coordinated control of Thyristor Controlled Phase Shifters and superconducting magnetic energy storage for three types of interconnected two-area power systems

In this paper, automatic generation control with interconnected two-area multi-unit all-hydro power system and two more test systems as all-thermal and thermal-hydro mixed haves been investigated. The transfer function of hydro turbine having non-minimum phase characteristics makes it different from the steam turbine. Upon application of small load perturbation to such all-hydro system, the frequency is severely disturbed and the system eventually becomes unstable. To stabilize the system for such load disturbance, comparative transient performance of two cases as (a) Thyristor Controlled Phase Shifter (TCPS) installed in series with the tie-line in coordination with Superconducting Magnetic Energy Storage (SMES) and (b) SMES located at each terminal of both areas are analyzed. It is observed that the case (b) i.e. SMES located at each terminal of both areas suppresses the frequency oscillations more effectively in integral controller assisted AGC of two-area multi-unit all-hydro system and the other two systems as well. In addition, the effectiveness of proposed frequency stabilizers is guaranteed by analyzing the transient responses of the system with different system parameters, various load patterns and in the event of temporary and permanent tie-line outage. Gains of the integral controller in AGC loop and parameters of TCPS and SMES are optimized with the help of a relatively novel particle swarm optimization, developed by the authors, called as craziness-based particle swarm optimization (CRPSO). The optimizing performance has been compared to that of real-coded genetic algorithm (RGA) to establish its superiority.

Damping of Power Systems Oscillations by using Genetic Algorithm-Based Optimal Controller

In this paper, the power system stabilizer (PSS) and Thyristor controlled phase shifter (TCPS) interaction is investigated. The objective of this work is to study and design a controller capable of doing the task of damping in less economical control effort, and to globally link all controllers of national network in an optimal manner, toward smarter grids. This can be well done if a specific coordination between PSS and FACTS devices is accomplished. Firstly, a genetic algorithm-based controller is used. Genetic Algorithm (GA) is utilized to search for optimum controller parameter settings that optimize a given eigenvalue based objective function. Secondly, an optimal pole shifting, based on modern control theory for multi-input multi-output systems, is used. It requires solving first order or second order linear matrix Lyapunov equation for shifting dominant poles to much better location that guaranteed less overshoot and less settling time of system transient response following a disturbance.

GA/particle swarm intelligence based optimization of two specific varieties of controller devices applied to two-area multi-units automatic generation control

This paper presents the comparative performance analysis of the two specific varieties of controller devices for optimal transient performance of automatic generation control (AGC) of an interconnected two-area power system, having multiple thermal–hydro–diesels mixed generating units. The significant improvement of optimal transient performance is observed with the addition of a thyristor-controlled phase shifter (TCPS) in the tie-line or capacitive energy storage (CES) units fitted in both the areas. Three different optimization algorithms are adopted for the sake of comparison of optimal performances and obtaining the optimal values of the gain settings of the devices independently. Craziness based particle swarm optimization (CRPSO) proves to be moderately fast algorithm and yields true optimal gains and minimum overshoot, minimum undershoot and minimum settling time of the transient response for any system. Comparative studies of TCPS and CES by any algorithm reveals that the CES units fitted in both the areas improve the transient performance to a greater extent following small load disturbance(s) in both the areas.

Automatic generation control of TCPS based hydrothermal system under open market scenario: A fuzzy logic approach

This paper presents the analysis of automatic generation control of a two-area interconnected thyristor controlled phase shifter based hydrothermal system in the continuous mode using fuzzy logic controller under open market scenario. Open transmission access and the evolving of more socialized companies for generation, transmission and distribution affects the formulation of AGC problem. So the traditional AGC two-area system is modified to take into account the effect of bilateral contracts on the dynamics. It is possible to stabilize the system frequency and tie-power oscillations by controlling the phase angle of TCPS which is expected to provide a new ancillary service for the future power systems. A control strategy using TCPS is proposed to provide active control of system frequency. Further dynamic responses for small perturbation considering fuzzy logic controller and PI controller (dual mode controller) have been observed and the superior performance of fuzzy logic controller has been reported analytically and also through simulation.

AGC study of a hydrothermal system with SMES and TCPS

AbstractFrequency deviations and inter‐area tie‐power fluctuations from their respective scheduled values following a local load disturbance are a source of great concern in interconnected power system operation and control. In this paper, a new method is proposed to minimise such deviations and thereby enhance the performance of Automatic Generation Control (AGC) of an interconnected hydrothermal power system with the coordinated operation of a Superconducting Magnetic Energy Storage (SMES) unit in thermal area and a Thyristor Controlled Phase Shifter (TCPS) in series with the tie‐line. Generation Rate Constraints (GRCs) are also considered for the thermal and hydro systems. The integral controller gain settings are obtained by optimising a quadratic performance index using the Integral Squared Error technique. Comparison of the dynamic responses demonstrates the effectiveness and efficiency of the suggested SMES–TCPS combination in suppressing and stabilising the oscillations of frequency and tie‐power deviations as well as in reducing the settling time. Copyright © 2008 John Wiley & Sons, Ltd.

Optimal power flow with FACTS devices using differential evolution

This paper presents differential evolution to minimize the generator fuel cost in optimal power flow control with flexible ac transmission systems (FACTS) devices. The FACTS devices considered here include thyristor-controlled series capacitor (TCSC) and thyristor-controlled phase shifter (TCPS). The proposed approach has been examined and tested on the modified IEEE 30-bus system. Test results indicate that the proposed approach can obtain better solution and requires less CPU time than evolutionary programming and genetic algorithm.

Effect of TCPS on oscillations in tie-power and area frequencies in an interconnected hydrothermal power system

The analysis of automatic generation control of a two-area interconnected hydrothermal power system considering a thyristor-controlled phase shifter (TCPS) in series with the tie-line is presented. It is possible to damp the system frequency and tie-power oscillations by controlling the phase angle of TCPS. A control strategy using TCPS is proposed to provide active control of system frequency. Gain settings of the integral controllers with and without considering TCPS are optimised using integral squared error technique following a step load disturbance in each of the areas by minimising a quadratic performance index. Analysis reveals that a TCPS is quite capable of suppressing the frequency and tie-power oscillations effectively under the occurrence of sudden load changes in any of the areas when compared with that obtained without TCPS.

Multi-objective optimal placement with multi-type FACTS devices by hybrid TS/SA approach

In this paper, a hybrid Tabu Search and Simulated Annealing (TS/SA) approach is proposed to find the optimal placement of multi-type FACTS devices to simultaneously minimise the total generator fuel cost and violation function. The problem is decomposed into the Multi-Objective Optimal Placement (MOOP) of multi-type FACTS devices subproblem that is searched by the hybrid TS/SA approach and the Multi-Objective Optimal Power Flow (MOOPF) with multi-type FACTS devices subproblem that is also solved by the earlier hybrid TS/SA approach and Quadratic Programming (QP). Four types of FACTS devices are used: Thyristor-Controlled Series Capacitor (TCSC), Thyristor-Controlled Phase Shifter (TCPS), Unified Power Flow Controller (UPFC), and Static Var Compensator (SVC). The solution includes optimal locations of multi-type of FACTS devices. Test results on the modified IEEE 30 bus indicate that the proposed hybrid TS/SA approach obtains less combined total generator fuel cost and violation function and requires less computing time than Genetic Algorithm (GA), SA, or TS alone. Furthermore, the maximum load factor of the MOOPF with multi-type FACTS devices placed by hybrid TS/SA on the modified IEEE 30-, 57-, and 118-bus systems is higher than those placed by the sensitivity method.

Selection of optimal number and location of thyristor-controlled phase shifters using genetic based algorithms

In recent years, major structural changes were introduced to the power sector all over the world. As a consequence, transmission expansion activities must be implemented to upgrade the utilities' power delivery systems. Some application of flexible AC transmission system (FACTS) technologies to existing high-voltage power systems has proved that the use of FACTS technology may be a cost-effective option for power delivery system enhancements. Undoubtedly, FACTS devices can minimise costly capital investments, but selecting the appropriate number and placement of these devices can be a challenge. To face this challenge, the paper deals with a methodology, based on a genetic algorithm, to identify the optimal number and location of FACTS devices in an assigned power-system network for maximising system capabilities, the social surplus and to satisfy contractual requirements in an open power market. In order to validate the usefulness of the approach suggested herein, a case study using the IEEE 30-busbar power system is presented and discussed.

Phase shifter placement in large-scale systems via mixed integer linear programming

This paper makes use of advances in mixed integer linear programming (MILP) to conduct a preliminary design study on the combinatorial optimal placement of thyristor controlled phase shifter transformers (TCPSTs) in large-scale power systems. The procedure finds the number, network location, and settings of phase shifters that maximize system loadability under the DC load flow model, subject to limits on the installation investment or total number of TCPSTs. It also accounts for active flow and generation limits, and phase shifter constraints. Simulation results are presented for the IEEE 24-, 118-, and 300-bus systems, as well as a 904-bus network. The principal characteristics of our approach are compared with those of other published flexible AC system transmission (FACTS) allocation methods.

Enhancement of power system transient stability using a nonlinear coordinated excitation and TCPS controller

A robust nonlinear coordinated generator excitation and thyristor-controlled phase shifter (TCPS) controller is proposed to enhance the transient stability of a multimachine power system. To eliminate the nonlinearities and interconnections of the multimachine power system, a direct feedback linearization (DFL) compensator through the excitation loop is designed. Considering the effects of plant parametric uncertainties and remaining nonlinear interconnections, a robust decentralized generator excitation controller is proposed to ensure the stability of the DFL compensated system. Only the bounds of the generator parameters are necessary to be known in the design of the proposed controller, while the transmission network parameters, system operating points or the fault locations need not be known. Since the proposed controller can ensure the stability of large-scale power system within the whole operating region for all admissible parameters, the transient stability of the overall system can be enhanced significantly. Digital simulation studies were conducted on a three-machine power system to show the effectiveness of the proposed control scheme in enhancing the transient stability of the system regardless of the network parameters, operating points and fault locations.

Nonlinear co-ordinated excitation and TCPS controller for multimachine power system transient stability enhancement

A robust nonlinear co-ordinated generator excitation and thyristor-controlled phase shifter controller is proposed to enhance the transient stability of a multimachine power system. To eliminate the nonlinearities and interconnections of the multimachine power system, a direct feedback linearisation (DFL) compensator through the excitation loop is designed. Considering the effects of plant parametric uncertainties and remaining nonlinear interconnections, a robust decentralised generator excitation controller is proposed to ensure the stability of the DFL compensated system. Only the bounds of the generator parameters need to be known in the design of the proposed controller, while the transmission network parameters, system operating points or the fault locations do not need to be known. As the proposed controller can ensure the stability of a large-scale power system within the whole operating region for all admissible parameters, the transient stability of the overall system can be enhanced significantly. Digital simulation studies were conducted on a three-machine power system to show that the proposed control scheme can enhance the transient stability of the system significantly, regardless of the network parameters, operating points and fault locations.

Smoking and the Need for Vaccination

Modern power system faces excessive frequency aberrations due to the intermittent renewable generations and persistently changing load demands. To avoid any possible blackout, an efficient and robust control strategy is obligatory to minimize deviations in the system frequency and tie-line. Hence, to achieve this target, a new two-degree of freedom-tilted integral derivative with filter (2DOF–TIDN) controller is proposed in this work for a two-area wind-hydro-diesel power system. To enhance the outcome of the proposed 2DOF–TIDN controller, its gain parameters are optimized with the use of a newly designed hybrid bat algorithm-harmony search algorithm (hybrid BA–HSA) technique. The effectiveness and superiority of hybrid BA–HSA tuned 2DOF–TIDN is validated over various existing optimization techniques like cuckoo search (CS), particle swarm optimization (PSO), HSA, BA and teaching learning-based optimization (TLBO). To further refine the system outcome in the dynamic conditions, several flexible AC transmission systems (FACTS) and superconducting magnetic energy storage (SMES) units are adopted for enriching the frequency and tie-line responses. The FACTS controllers like static synchronous series compensator (SSSC), thyristor-controlled phase shifter (TCPS), unified power flow controller (UPFC) and interline power flow controller (IPFC) are employed with SMES simultaneously. The simulation results disclose that the hybrid BA–HSA based 2DOF–TIDN shows superior dynamic performance with IPFC–SMES than other studied approaches. A sensitivity analysis is examined to verify the robustness of proposed controller under ±25% changes in loading and system parameters.

サイリスタ制御位相調整器の制御パターンと位相調整動作

サイリスタ制御位相調整器の制御パターンと位相調整動作

Optimal active power flow incorporating power flow control needs in flexible AC transmission systems

This paper presents a new method to incorporate the power flow control needs of flexible AC transmission system (FACTS) in studying the optimal active power flow problem. The linearized (DC) network model is used in this paper. Three main types of FACTS devices, namely thyristor controlled series compensators (TCSC), thyristor controlled phase shifters (TCPS) and unified power flow controllers (UPFC), are considered. The proposed method decomposes the solution of such modified OPF problem into two problems' iteration. The first problem is a power flow control subproblem while the second problem is a normal OPF problem. It is shown that the modified active power OFF can be solved by a new iterative strategy where a conventional LP-based technique may be used. Digital simulation studies on the IEEE 30 bus test system are presented to show the effectiveness of the proposed method.

Fuzzy-logic method for adjustment of variable parameters in load-flow calculation

The paper presents a new approach using fuzzy logic to adjust variable parameters so as to meet constraints during load-flow study. Parameters to be adjusted include transmission-line impedance, phase angle and transformer tap position, and the constraints are transmission-line power flow and bus-voltage magnitude. Versatile apparatus which are used to tune these parameters include the thyristor-controlled series compensator, thyristor-controlled phase shifter, unified power-flow controller and on-load tap changer. The proposed approach is particularly aimed at assisting convergence in load flow programs. The parameters to be adjusted are decoupled from the main body of the load-flow formulation. The methodology for parameter adjustment is conducted by using fuzzy logic.

98/01300 Carbon dioxide capture in molten carbonate fuel cell power plants fueled with coal and natural gas: Reimer, P. et al. Proc. Intersoc. Energy Convers. Eng. Conf., 1997, 32, 805–810

A robust nonlinear coordinated generator excitation and thyristor-controlled phase shifter (TCPS) controller is proposed to enhance the transient stability of a multimachine power system. To eliminate the nonlinearities and interconnections of the multimachine power system, a direct feedback linearization (DFL) compensator through the excitation loop is designed. Considering the effects of plant parametric uncertainties and remaining nonlinear interconnections, a robust decentralized generator excitation controller is proposed to ensure the stability of the DFL compensated system. Only the bounds of the generator parameters are necessary to be known in the design of the proposed controller, while the transmission network parameters, system operating points or the fault locations need not be known. Since the proposed controller can ensure the stability of large-scale power system within the whole operating region for all admissible parameters, the transient stability of the overall system can be enhanced significantly. Digital simulation studies were conducted on a three-machine power system to show the effectiveness of the proposed control scheme in enhancing the transient stability of the system regardless of the network parameters, operating points and fault locations.

98/01294 Analysis of thyristor-controlled phase shifter applied in damping power system oscillations: Wang, H. F. et al. Electrical Power and Energy Systems, 1997, 19, (1), 1–9

98/01294 Analysis of thyristor-controlled phase shifter applied in damping power system oscillations: Wang, H. F. et al. Electrical Power and Energy Systems, 1997, 19, (1), 1–9

A hybrid solid state phase shifter using PWM AC converters

Active power flow in transmission lines can be varied using a conventional or thyristor controlled phase shifter in series with the line, which introduces a phase shift between sending and receiving end voltages. However, the control of the phase shift can be executed only in steps depending on the taps available in the phase shifting transformer. An approach to obtain continuous control of the phase shift using a conventional tap changing transformer and a pulse width modulated buck AC-AC converter is presented in this paper. Operating principles, design considerations and other practical issues are discussed. Detailed computer simulation results are presented in the paper. The advantages and disadvantages of the proposed approach in relation to the conventional approaches are discussed.