Shunt Flexible AC Transmission Research Articles

Optimal Choice and Allocation of Shunt FACTS Devices Using Differential Search Algorithm

In this paper, new and efficient heuristic algorithm, Differential Search Algorithm (DSA), is used for optimal choice and allocation of shunt Flexible AC transmission systems (FACTS) devices, Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM). In the proposed optimal location method, SVC and STATCOM devices are located randomly and dynamically with objective of minimizing the real power loss, improving the voltage profile and enhancing the voltage stability. The best solution sets for objectives aforementioned are achieved by minimizing each objective functions by the proposed approach. In order to evaluate the proposed methodology, it has been tested on IEEE 30 bus system and compared to another widely used optimization algorithm, Artificial Bee Colony (ABC) algorithm. The validity of the proposed optimization algorithm is proven by the results and comparative analysis with other method.

Sizing and Sitting of Static VAR Compensator (SVC) Using Hybrid Optimization of Combined Cuckoo Search (CS) and Antlion Optimization (ALO) Algorithms

Worldwide, due to the abrupt growth of population, the load demand has been rising dramatically in the last few years. This led to an increase in branch overloads, voltage deviations, and power losses. These problems may result in line outages or the occurrence of blackouts. Flexible AC transmission system (FACTS) devices can be installed in the power system to ensure increased power flow capability and flexible voltage control to address these issues. In this paper, one of the most used FACTS is utilised. It is called Static VAR Compensator (SVC). This controller is one of the most commonly used shunt FACTS controllers due to its low cost in comparison to others, ease of operation, and integration into the power grid. Two Optimization algorithms are combined to form a hybrid optimization approach: Cuckoo Search (CS) and Antlion Optimization (ALO). This hybrid approach employs the exploration of ALO to adjust the optimum allocation and size for SVCs in the power system. This study proposes the IEEE 57 bus scheme as a fairly large structure, with the 50 and 41 branch outages considered the worst-case scenarios for line outages in this system. The simulation results show that the proposed methodology balances exploring the research space and exploiting the best existing solutions compared to some of the other introduced approaches in the literature.

Improvement of Static Voltage Stability of 16-Bus Bali System by Optimal Placement of SVC

In a power system, the reactive power imbalance is related to the stability of the static voltage because the injection of reactive power that the bus receives from the system determines the bus's capability in the system. Rapid increases in real and reactive power losses occur as the system approaches the voltage drop point or the maximum load point. It is necessary to support local and adequate reactive power to avoid system leading to be voltage collapse. This study analyzes the improvement of the margin of static voltage stability using one type of modern control equipment of shunt flexible AC transmission system (FACTS), namely the static var compensator (SVC). The controller's representations are used in the continuation power flow (CPF) process to study static voltage stability. The proposed method's effectiveness has been investigated using a practical test system, namely the Bali 16-bus system, to increase the system loading capacity. The simulation was carried out by installing a modern controller in the best location, namely on bus 07 ASARI; an increase in system margin loading closed to 2% compared to the base case condition, namely λmax = 1,879 p.u with the voltage profile not changing significantly.

Evolutionary Algorithm-Based Adaptive Robust Optimization for AC Security Constrained Unit Commitment Considering Renewable Energy Sources and Shunt FACTS Devices

An AC security constrained unit commitment (AC-SCUC) in the presence of the renewable energy sources (RESs) and shunt flexible AC transmission system (FACTS) devices is conventionally modeled as a deterministic optimization problem to minimize the operation cost of conventional generation units (CGUs) subject to AC optimal power flow (AC-OPF) equations, operation constraints of RESs, shunt FACTS devices, and CGUs. To cope with the uncertainties of load and RES generation, robust and stochastic optimization and linearized formulation have been used to achieve a sub-optimal solution. To arrive at a more optimal solution, an evolutionary algorithm-based adaptive robust optimization (EA-ARO) approach to solve the non-linear and non-convex optimization problem was proposed. A hybrid solver of grey wolf optimization (GWO) and teaching learning-based optimization (TLBO) was proposed to solve the AC-SCUC problem in the worst-case scenario to obtain robust and reliable optimal solution. Finally, the proposed method was simulated on standard IEEE test systems to demonstrate its capabilities, and the results showed the proposed hybrid solver obtained robust optimal solutions with reduced computation time and standard deviation. Moreover, the numerical results proved the proposed strategy’s capabilities of improving the economics of generation units, such as lower operational cost, and enhancing the performance of the transmission networks, such as improved voltage profile and reduced energy losses.

Demand response-integrated economic dispatch incorporating renewable energy sources using ameliorated dragonfly algorithm

This paper presents an integrated demand response (DR) and dynamic economic dispatch (DED) model consisting of renewable energy sources (RESs) and shunt FACTS (flexible AC transmission systems) devices with focus on reducing thermal energy consumption. RESs are environment friendly and can be located close to the load centers, which helps in reducing T&D losses as well as harmful emissions. DR helps in reducing peak power consumption and generation cost of thermal power plants. Shunt FACTS device, static synchronous compensator (STATCOM), helps in improving voltage profile of the network. Analyses are carried out using the proposed ameliorated dragonfly algorithm (ADFA). The efficiency of developed ADFA is proved by comparing the obtained results with many other methods. Static economic dispatch is carried out on 6-, 17- and 40-thermal generator test systems using ADFA, and the results are compared with other existing methods available in the literature. Further, DED is carried out on 6- and 17-thermal generator test systems. Later, a DED is performed on a real-time 17-thermal generator (South Indian 86-bus system) system for four seasons. Solar irradiance and wind speed are modeled using beta distribution and Weibull distribution functions by collecting the historical data of the test system. The developed demand response program is implemented on a real-time 17 thermal unit and 86-bus test system located in Tamil Nadu, southern part of India. The developed DR model alters time-independent loads so that burden on generating stations during the peak load is minimized. The effect of DR, RES and STATCOM in the test system is studied individually. Further, a comparative analysis considering DR, RES and STATCOM together is presented. The results obtained are promising, and it can be interpreted that by using the developed model there will be improvement in the penetration levels of RES which in turn reduces the demand for thermal energy.

Synchrophasors assisted protection scheme for the shunt‐compensated transmission line

This study presents synchrophasor assisted protection scheme for the protection of long transmission line compensated with shunt flexible AC transmission system (FACTS) device. With the advancement in synchrophasor technology, data communication medium, and wide area measurement system for transmission line protection, the differential protection scheme is a most suited scheme over the over-current, distance and directional protection schemes. The proposed scheme discriminate between internal and external fault using the time synchronised voltages and currents of both the terminal of the transmission line. The performance of proposed scheme has been evaluated on IEEE 12 bus FACTS benchmark power system model implemented in PSCAD/EMTDC. The measured voltage & current signals are pre-processed and phasors are estimated through DFT algorithm in MATLAB. The performance remains unaffected during wide variation in fault and system parameters including different line length and static var compensator rating. The test results confirm the selective, simplicity, high speed, sensitivity, and robustness of the proposed protection scheme. This scheme is also able to distinguish the faulty phase(s) from healthy phases, which enables the single-pole tripping option. Finally, comparative evaluation of the proposed technique with the existing protection schemes clearly shows its superiority.

ERF-based fault detection scheme for STATCOM-compensated line

Summary The shunt flexible AC transmission system devices affect the protection schemes because of reactive power injection. Therefore, robust protection schemes are required. This study presents a fault detection scheme, which is based on estimated reactive power factor (ERF) and differential current with modified setting. The ERF is defined as sine of phase difference between the static synchronous compensator tap voltage and differential current. The static synchronous compensator tap voltage can be estimated using local end voltage and current. The ERF is measured at both the relay ends. In capacitive mode, if both ERFs are more than upper threshold, the fault is external, and if any ERF is less than upper threshold, the fault is internal. In inductive mode, if ERF is between upper and lower threshold, fault is internal else, if differential current is more than modified differential current setting, the fault is internal, or else, the fault is external. The performance of presented scheme is investigated for various system configurations with PSCAD/EMTDC simulations. Further, the scheme is successfully validated in real-time digital simulator. It is found that the scheme is robust and selective for various faulty conditions, compensation level variations, and location variations.

Two‐level procedure based on HICAGA to determine optimal number, locations and operating points of SVCs in Isfahan–Khuzestan power system to maximise loadability and minimise losses, TVD and SVC installation cost

Increasing maximum power system loadability while maintaining bus voltages and line loadings constraints by flexible AC transmission system (FACTS) devices is one of the main issues in power system studies. One of the shunt FACTS devices widely used in power system is static var compensator (SVC). Its performance on power system is highly dependent on its number, location and operating point. This study presents a two-level procedure to find optimal number, locations, and operating points of SVCs in a power system. At the first level, the goal is to maximise loadability of the power system. At this level, by using a method based on iterative process, applying SVCs to the power system, and increasing load factor, the optimisation algorithm seeks to find locations and operating points of SVCs that fulfil bus voltages and line loading constraints. This process continues until the increase in the number of SVCs does not lead to an increase in loadability. At the second level and for a certain number of SVCs, power system losses, total voltage deviations (TVD), and SVC installation cost are minimised at specific loadability. In this study, hybrid imperialist competitive algorithm and genetic algorithm (HICAGA) have been used for optimisation.

A Supplementary Controller for Improvement of Small Signal Stability of Power System with Wind Power Penetration

Wind power penetration affects the dynamics and operational performance of a conventional power system. This article investigates the stability issues of a power system with the penetration of wind power from a doubly fed induction generator and direct drive synchronous generator. An approach to utilize an existing shunt flexible AC transmission system controller, static VAR compensator, for enhancing the small signal stability of a wind connected power system is discussed here. Supplementary stabilizing control for damping oscillatory modes is applied to static VAR compensator and suitable control input has been selected for the best damping performance of the proposed controller.

Robust Voltage/VAR Control Using PSO Based STATCOM: A Case Study in Turkey

In this paper, voltage stability assessment of a real power system subjected to a large disturbance is introduced by a combination of static and dynamic approaches. In the first part of the study, the system is analyzed for both normal operation and contingencies by using static analysis tool in which continuation power flow method (CPF) is performed. In order to improve static and dynamic voltage stability, a shunt flexible AC transmission system (FACTS) device, static synchronous compensator (STATCOM) is employed to the system as an additional voltage support device. However, action of the STATCOM is directly influenced by proper functioning of the controller. Poorly tuned STATCOM controller results in voltage oscillations. Main purpose of the paper is optimal parameter tuning of the STATCOM in order to improve the dynamic voltage control capability in the case of occurence of a severe disturbance in the power system. Therefore, in the second part of the study, the tuning problem of the STATCOM is converted to an optimization problem which minimizes the voltage deviations. Particle swarm optimization (PSO) technique is applied to the problem in search of the optimal control parameters of the STATCOM.

ATC enhancement by incorporating FACTS devices for deregulating scenario in present power market

The cost based monopolistic power market rules are new fangled by the word deregulation. Trepidations in its conceptualisation and integrated operation in the impending scenario are transmission pricing, congestion management and Available Transfer Capability (ATC). Of this intriguing technical challenge, ATC is the one that needs to be interrogated and dogged to make open access a feasible obsession for private entity participation which is deregulation’s intention. This research work aims at calculating ATC using non iterative, simple, Power Transfer Distribution Factors (PTDF) based methodology, enhancing them using Flexible AC Transmission system (FACTS) devices like Static compensator (STATCOM) and Unified Power Flow Controller (UPFC). A proven alternative to overcome extravagance by erecting new transmission facility is incorporation of FACTS devices in the existing structure that indulge in reactive power compensation. These FACTS devices are modelled using the power flow equations and is placed optimally based on the slope of sensitivity factors. The optimal settings of FACTS devices is obtained by a soft computing technique labelled as Particle Swarm Optimisation (PSO) to enhance the ATC for the assumed bilateral and multilateral power contracts. The voltage and angle of shunt and series FACTS devices are randomly generated as the population of PSO on sample 6 bus and standard IEEE 30 bus systems.

Optimal Location of Thyristor-Controlled Series Compensation and Static VAR Compensator to Enhance Steady-state Performance of Power System with Wind Penetration

Wind generation connection to power system affects steady-state and transient stability. Furthermore, this effect increases with the increase of wind penetration in generation capacity. In this article, optimal location of flexible AC transmission system devices is carried out to solve the steady-state problems of wind penetration using a genetic algorithm. Case study is carried out on modified IEEE 39-bus system with wind penetration increases by 50%; the system suffers from outage of one generator with load decrease in one of system buses by 15%. The system suffers from minimum voltage reduction, total loss increase, and violation of power and power angle limits. Series and shunt flexible AC transmission system devices are used in this article. Results showed that series flexible AC transmission system devices in certain range are able to solve these problems associated with wind penetration in power systems with acceptable cost saving.

Enhancement of Power Quality by an Application FACTS Devices

<p>The paper narrates widespread use of electrical energy by modern civilization has necessitated producing bulk electrical energy economically and efficiently. The Flexible AC Transmission system (FACTS) is a new technology based on power electronics, which offers an opportunity to enhance controllability, stability, and power transfer capability of AC transmission systems. Here SVC has been developed with the combination of TCSC and TCR. The paper contains simulation models of Thyristor controlled Series Capacitor (TCSC) and Thyristor controlled Reactor (TCR)-based Static VAR Compensator (SVC) which are the series and shunt Flexible AC Transmission Systems (FACTS) devices. The fact devices are designed by considering the line losses and their stability. The design and simulations of TCSC and TCR-based SVC shows the effectiveness of result using the MATLAB/Simulink. The designed system will try to reduce the voltage drops and electrical losses in the network without the possibility of transient especially in case of long transmission system. Student feedback indicates that this package is user-friendly and considerably effective for students and researchers to study theory of controlled reactor compensators, series capacitor compensator, and the reactive power control and voltage regulation.</p>

Transient Stability Enhancement of Multimachine Power System Using Robust and Novel Controller Based CSC-STATCOM

A current source converter (CSC) based static synchronous compensator (STATCOM) is a shunt flexible AC transmission system (FACTS) device, which has a vital role as a stability support for small and large transient instability in an interconnected power network. This paper investigates the impact of a novel and robust pole-shifting controller for CSC-STATCOM to improve the transient stability of the multimachine power system. The proposed algorithm utilizes CSC based STATCOM to supply reactive power to the test system to maintain the transient stability in the event of severe contingency. Firstly, modeling and pole-shifting controller design for CSC based STATCOM are stated. After that, we show the impact of the proposed method in the multimachine power system with different disturbances. Here, applicability of the proposed scheme is demonstrated through simulation in MATLAB and the simulation results show an improvement in the transient stability of multimachine power system with CSC-STATCOM. Also clearly shown, the robustness and effectiveness of CSC-STATCOM are better rather than other shunt FACTS devices (SVC and VSC-STATCOM) by comparing the results in this paper.

Transient Stability Assessment of Two-Area Power System with LQR based CSC-STATCOM

A current source converter (CSC) based static synchronous compensator (STATCOM) is a shunt flexible AC transmission system (FACTS) device, which has a vital role as a stability support for small and large transient instability in an interconnected power network. A robust linear quadratic regulator (LQR) based controller for CSC-STATCOM is proposed. In this paper, LQR based CSC-STATCOM is designed to enhance the transient stability of two-area two-machine power system. First of all, modeling & LQR based controller design for CSC-STATCOM are described. After that, the impact of the proposed scheme on the test system with different disturbances is demonstrated. The feasibility of the proposed scheme is demonstrated through simulation in MATLAB and the simulation results show an improvement in the transient stability of power system with CSC-STATCOM. Also, the robustness and effectiveness of CSC-STATCOM are better rather than other shunt FACTS devices (SVC & VSC-STATCOM) in this paper.

Advance Compensated Mho Relay Algorithm for a Transmission System with Shunt Flexible AC Transmission System Device

—The presence of shunt flexible AC transmission system devices adversely affect the performance of distance relay and create security and reliability issues. This article introduces a noble compensated Mho relay algorithm for the protection of transmission line employing shunt flexible AC transmission system devices, such as a static VAR compensator and static synchronous compensator. A detailed model of transmission system employing a shunt flexible AC transmission system device is explained. Then compensated impedance inserted by a shunt device in the transmission line is calculated, and finally, a compensated Mho relay algorithm is proposed to protect zone one of the transmission line. Simulation work is carried out in PSCAD/EMTP software. Results show that the proposed relay is secure, accurate, and reliable under the wide variation in power system parameters, such as load angle, fault resistance, fault location, and compensation level.

Fuzzy-Wavelet Based Double Line Transmission System Protection Scheme in the Presence of SVC

Increasing the power transfer capability and efficient utilization of available transmission lines, improving the power system controllability and stability, power oscillation damping and voltage compensation have made strides and created Flexible AC Transmission (FACTS) devices in recent decades. Shunt FACTS devices can have adverse effects on distance protection both in steady state and transient periods. Severe under reaching is the most important problem of relay which is caused by current injection at the point of connection to the system. Current absorption of compensator leads to overreach of relay. This work presents an efficient method based on wavelet transforms, fault detection, classification and location using Fuzzy logic technique which is almost independent of fault impedance, fault distance and fault inception angle. The proposed protection scheme is found to be fast, reliable and accurate for various types of faults on transmission lines with and without Static Var compensator at different locations and with various incidence angles.

Comparison of PSO and RCGA for Optimal Location of STATCOM for Improvement of Transient Stability of Power Systems

In electrical power systems, reactive power compensation plays an important role in transient stability. Shunt flexible AC transmission system (FACTS) devices are being used in controlling the reactive power flow to the power network and, hence, the system voltage fluctuations and stability. Static synchronous compensator (STATCOM) is one of the shunt connected FACTS devices. The primary purpose of STATCOM is to support bus voltage by injecting (or absorbing) reactive power, but it is also capable of improving the power system stability. In this paper, an interconnected two-area test system with actual transmission line model is used to show the effectiveness of Particle Swarm Optimisation (PSO) and Real Coded Genetic Algorithms (RCGA) algorithms for determining the optimal location for power system stability improvement.

Application of multiple FACTS devices of similar type for congestion mitigation

FACTS (flexible AC transmission system) devices can increase line loadability by altering transmission line parameters. Use of multiple FACTS devices can reduce congestion in heavily loaded lines, reduce system loss, improve stability and hence reduce cost of energy delivery. This paper examines the effect of multiple FACTS devices of similar type on congestion mitigation. The system has been tested with a series FACTS device (TCSC), a shunt FACTS device (STATCOM) and a combined series & shunt FACTS device (UPFC). The proposal has been demonstrated on IEEE-14 bus system.

UPFC with series and shunt FACTS controllers for the economic operation of a power system

This paper presents the application of Genetic Algorithm (GA) and Differential Evolution (DE) technique for the minimization of transmission loss and simultaneous reduction in the operating cost of the system using Flexible AC Transmission System (FACTS) devices. Three types of FACTS devices, Thyristor Controlled Series Compensator (TCSC), Static VAR Compensator (SVC) and Unified Power Flow Controller (UPFC) are considered for this purpose. Optimal placement of FACTS devices in the heavily loaded power system reduces transmission loss, control reactive power flow, improves voltage profile of all nodes and also reduces operating cost. The system is reactively loaded starting from base to 200% of base reactive load and the system performance is observed without and with FACTS devices. The proposed technique is applied on IEEE 30-bus system for the optimal setting of FACTS devices. Finally, how system performance is improved with the use of UPFC along with other series and shunt FACTS controller is illustrated.