Flexible AC Transmission System Devices Research Articles

Linear modelling of series FACTS devices in power system operation models

This paper presents injection-shift-factor-based linear modelling for various types of series flexible ac transmission system (FACTS) devices within the DC power flow framework. The presented models allow FACTS devices to be properly integrated in current operation and planning software tools, which is key to harnessing the power flow capabilities provided by FACTS technology. Although recent literature has attempted to develop linear models for FACTS devices, the existing models do not accurately reflect the actual operating range for many FACTS devices. Compared to the existing models, the modelling approach presented here reflects the principle of operation of each type of series FACTS device in adjusting transmission line reactance. Through mathematical derivation, linear constraints for FACTS operation are formulated, which are used to formulate power system operation models. The formulated problems are then analysed through simulation studies on various test systems. The results highlight the significant computational efficiency improvements provided by linear FACTS modelling in DC-based operation models.

Techno-economic strategy for reactive power planning using Series-shunt compensation in power transmission network

This research article proposes an optimization oriented planning strategy of reactive power (VAR) in power transmission system. Basically it is a qualitative effort to understand the mathematical principles, technical facets and economic aspects with their utility in reactive power planning (RPP) prior to execute the proposed strategy through a unique solution model. Initially, the objective is formulated by measuring different cost components such as VAR generation cost, line charging cost, FACTS (Flexible AC Transmission System) device operation cost and cost due to real power loss. The vulnerable positions in the system are defined for the placement of FACTS devices after computing a set of mathematical methods. The installation bottlenecks of these devices are wiped out depending upon some technical considerations and performances. Thereafter, differential evolutionary algorithm is hybridized with crow search algorithm to determine an optimal set of controlling variables. The code profiling of the proposed approach has been rendered on two inter-regional practical power networks (India’s 62 and 191 bus power network). Finally, the responses of the bench-mark functions and statistical outcomes are analyzed extensively to justify the efficiency and efficacy of the proposed solution model.

Research progress and research prospects for configuration method of flexible AC transmission system device

Flexible AC transmission system (FACTS) has become the main development direction of power system in the future, so scientific configuration method of FACTS device is very important. At present, the configuration method of FACTS device has been explored to some extent, but there is still a lack of comprehensive summary of FACTS device configuration method and scientific configuration methods of FACTS device adapting to various application scenes in power system. To this end, this paper summarizes research progress and research prospects of configuration methods of FACTS device. Firstly, starting from the single device configuration within three types of FACTS devices and the multiple device configuration of several types of FACTS devices, research progress of the configuration methods is summarized. Then, from four perspectives which are multiple targets, multiple types, power-supply planning and power grid planning, realization ideas of configuration methods with multiple targets or with multiple types, and the configuration methods considering power-supply planning or considering power grid planning are all are proposed in this paper, which can meet the development needs of power system in the future. The summary of research progress and the four proposed adaptive configuration methods done in this paper aims to provide a reference for the subsequent research on configuration method of FACTS devices.

Moving-Target Defense Against Cyber-Physical Attacks in Power Grids via Game Theory

This work proposes a moving target defense (MTD) strategy to detect coordinated cyber-physical attacks (CCPAs) against power grids. The main idea of the proposed approach is to invalidate the knowledge that the attackers use to mask the effects of their physical attack by actively perturbing the grid’s transmission line reactances via distributed flexible AC transmission system (D-FACTS) devices. The proposed MTD design consists of two parts. First, we identify the subset of links for D-FACTS device deployment that enables the defender to detect CCPAs against any link in the system. Then, in order to minimize the defense cost during the system’s operational time, we formulate a zero-sum game to identify the best subset of links to perturb (which will provide adequate protection) against a strategic attacker. The Nash equilibrium robust solution is computed via exponential weights, which does not require complete knowledge of the game but only the observed payoff at each iteration. Extensive simulations performed using the MATPOWER simulator on IEEE bus systems verify the effectiveness of our approach in detecting CCPAs and reducing the operator’s defense cost.

Reducing Fault Current by Using FACTS Devices to Improve Electrical Power Flow

Today, there is a large increase in the demand for electricity. The transmission and distribution networks, however, cannot fulfill unbound demands due to the scarcity of resources. Power lines have losses which make the situation more unfavorable for maximum power transfer. Implementing a flexible AC transmission system (FACTS) is one of the best ways to reduce line losses. This paper proposes a FACTS-based method for minimizing the fault current in the system. Switchgear and protection equipment also perform better when this is done. Moreover, due to the reduced fault current of the switched system, a larger amount of power can be transmitted. Static synchronous series compensator (SSSC), static synchronous compensator (STATCOM), and unified power flow controller (UPFC) are evaluated in this case. With STATCOM and UPFC, fault currents are significantly reduced. Furthermore, STATCOM and UPFC can also reduce the fault currents in the power system in addition to voltage regulation and power flow control. A MATLAB/Simulink model is used to evaluate the model’s feasibility.

Optimal Planning and Operation of Hidden Moving Target Defense for Maximal Detection Effectiveness

Moving target defense (MTD) in the power system is a promising defense strategy to detect false data injection (FDI) attacks against state estimation using distributed flexible AC transmission system (D-FACTS) devices. A hidden MTD (HMTD) is a superior MTD method, as it is stealthy to sophisticated attackers. However, the optimal planning and operation of D-FACTS devices that ensure the MTD hiddenness and maximal detection effectiveness are challenging yet unresolved issues. In this paper, we tackle these challenges by first deriving a novel hiddenness operation condition. Then, we propose an analytical sufficient condition on the D-FACTS placement for HMTDs using a graph-theory-based topology analysis. A depth-first-search-based D-FACTS placement algorithm is proposed to guarantee the MTD hiddenness while maximizing the rank of its composite matrix, i.e., an indicator of the MTD effectiveness, and covering all necessary buses. Additionally, we propose DC- and AC-HMTD operation models to determine the setpoints of D-FACTS devices. The optimization-based DC-HMTD model overcomes the drawbacks of the existing HMTD operation. The ACOPF-based HMTD operation model minimizes the generation cost to utilize the economic benefit of D-FACTS devices. Comparative numerical results on the IEEE 14-bus and IEEE 57-bus systems show the efficacy of the proposed planning and operation approaches.

Multi-objective Moth Flame Optimizer: A Fundamental Visions for Wind Power Integrated Optimal Power Flow with FACTS Devices

ABSTRACT Optimal power flow (OPF) is one of the complex optimization problems in the power system domain. The OPF problem becomes much more challenging when renewable energy sources are added to the power system grid, which is unpredictable and volatile. Also, FACTS (flexible AC transmission system) devices are becoming more common in modern power systems to help ease network congestion and minimize demand. This paper aims to solve the single and multi-objective OPF by combining stochastic wind power with various types of FACTS devices such as static VAR compensator, thyristor-controlled series compensator, and thyristor-controlled phase shifter. To model stochastic wind energy, Weibull probability density functions have been used. The locations and ratings of the FACTS devices are also designed to reduce the system’s total generation cost. A non-dominated multi-objective moth flame optimization technique is used for the optimization issue. The fuzzy decision-making approach is applied to the best compromise solution. The results are validated through a modified IEEE-30 bus test system and compared with three newly developed algorithms.

Optimal placement ofFACTSdevices and power‐flow solutions for a power network system integrated with stochastic renewable energy resources using new metaheuristic optimization techniques

Flexible AC transmission systems (FACTS) and optimal power-flow (OPF) solutions play an important role in solving power operation problems. The volatile nature of the power generation profiles from renewable energy sources, solar and wind systems, and determining the optimal locations and sizes of FACTS devices increase the complexity of the OPF problems in modern power network models, such as transmission power loss, power generation operation cost and voltage deviation, as a highly nonlinear-nonconvex optimization problem. Therefore, this article introduces and employs four new independent, reliable and efficient optimization algorithms inspired by nature and biological nature, namely: Slime Mould Algorithm (SMA), Artificial Ecosystem-based Optimization (AEO), Marine Predators Algorithm (MPA) and Jellyfish Search (JS), for solving both multi- and single-OPF objective problems for a power network incorporating FACTS and stochastic renewable energy sources. The proposed new metaheuristic optimization techniques are compared to the common and available alternatives in the literature, Particle Swarm Optimization (PSO), Moth Flame Optimization (MFO) and Grey Wolf Optimizer (GWO), using IEEE 30-bus test system. To consider and address the challenges of the OPF in modern power network models, the proposed optimization techniques tested under different operation cases such as an increasing in the load, with and without FCTAS and renewable energy sources, different renewable energy sources locations on the network. The result showed that the MPA, SMA, JS and AEO algorithms are more effective solvers for the OPF problems cases compared to the PSO, GWO and MFO algorithms. For example, the AEO obtained 0.0844 p.u. in case of minimizing the voltage deviation compared to 0.1155 p.u. for PSO, which means that the AEO algorithm improved the voltage deviation term by 27% compared to the PSO algorithm.

Performance enhancement of modified SVC as a thyristor binary switched capacitor and reactor banks by using different adaptive controllers

In this paper, a new topology with two shunts flexible AC transmission system (FACTs) devices, thyristor binary switched capacitors (TBSC), and thyristor binary switched reactors (TBSR) based SVC has been developed, which are working in parallel. Both TBSC and TBSR are designed, and simulation results are obtained for the dynamic loading condition. Switching of capacitor and reactor banks with thyristor as a switch is obtained at transient-free conditions so that the significant problem of switching harmonics is eliminated. The coarse control of reactive power is obtained by selecting switchable capacitor banks in binary mode. For fine control, the TBSR bank is designed with a total value equal to the lowest step value of the TBSC bank. It is discrete stepwise compensation at a period of one cycle, and this reactive power compensation is almost continuous as per requirement. It has near-to-zero switchings and zero steady-state harmonics. The mathematical model of TBSC + TBSR has been identified with the system identification toolbox. Different control strategies are implemented as PID controller, Model predictive control, and Model reference adaptive control. The proposed SVC topology performance is discussed based on the performance parameters such as rise time, settling time, and peak overshoot using adaptive controllers.

Fault Ride Through in Grid Integrated Hybrid System Using FACTS Device and Electric Vehicle Charging Station

Adopting eco-friendly solutions is the need of the hour in order to downscale carbon emissions and the fast depletion of fossil fuels. Hybrid energy systems provide one such optimistic sustainable solution for power generation in a grid integrated system as well as for stand-alone applications. With grid integrated systems, there are many grid codes to be maintained such as voltage stability, frequency deviation and Fault Ride Through Capability (FRT). In a hybrid system, the propensity of the PV/Wind system to remain connected at the moment of short electric fault is identified as FRT. This paper elucidates the voltage compensation using an Electric Vehicle (EV) charging station or a Flexible AC Transmission System (FACTS) device depending on the intensity of fault that occurs at the Point of Common Coupling (PCC) in grid integrated hybrid systems. When a fault occurs at the PCC, depending on the intensity of the voltage sag either the EV charging station or a FACTS device, namely a Dynamic Voltage Restore (DVR), provides the voltage compensation. The voltage obtained from an EV charging station or DVR is conditioned using power converters and fed to the PCC to even out the discrepancy in the voltage that is effected due to the fault. Even though charges electric vehicles continuously, the EV charging station gives priority to supply voltage for compensation whenever a fault occurs at the grid. If the intensity of voltage sag due to fault is between 0.9 to 0.51 p.u, the EV charging station provides voltage compensation, and for voltage sag between 0.5 to 0.2 p.u, DVR takes over to provide voltage compensation for the continuous sustainability of the grid. The proposed system makes use of an existing source such as an EV charging station as a supplementary device to provide compensation, and also has a backup supplementary device DVR in case of any non-availability of the EV charging station. Thus, the voltage compensation in turn facilitates the parameters such as DC link voltage and the grid voltage to stay within the pertinent limits in the event of a fault at the grid. The system was simulated using MATLAB Simulink and the results were verified.

Reliability Evaluation of Bulk Power Systems Incorporating UPFC

Unified power flow controller (UPFC) is one of the most advanced flexible AC transmission system (FACTS) devices that can simultaneously and independently control both the real and reactive power flow in a transmission line. The utilization of UPFC can result in significant reliability benefits in modern power systems. This paper proposes a novel reliability network model for a UPFC, which incorporates the logical structure and the distinct operating modes of a UPFC. Two-state or three-state models have been used for UPFC by previous researchers. The proposed model divides the UPFC operating modes into four states, namely the UPFC up state, STATCOM state, SSSC state and UPFC down state, in order to improve the accuracy of the model by recognizing the practical operating states of a UPFC. The new model also incorporates an AC flow-based optimal load shedding approach to assess the impact of bus voltages and reactive power flow on UPFC in order to decide appropriate load curtailment in the reliability evaluation process. The performance of the proposed model is verified using a test system, and compared with different reliability models of UPFC. Various operating schemes, such as different placement locations of UPFC, and different capacities of UPFC are used to illustrate the advantages of the developed models, and to examine the impacts of UPFC on the system reliability.

Magnetically controllable reactor based multi-FACTS coordination control strategy

Traditional devices in flexible AC transmission system (FACTS) like magnetically controllable reactor (MCR), and fixed capacitors (FC) are less expensive and have medium or low response speed that can only provide excessive inductive or capacitive reactive power compensation. However, modern FACTS devices like static var compensators (SVC) are expensive and have high response speed which can provide limited inductive to capacitive reactive power compensation as compared to the MCR and FC. In addition, if there is no proper coordination between these traditional and modern FACTS devices they absorb each other's reactive power and may results in the decrease of compensation margin and wastage of the resources. Therefore, to make an effective use of these categories of FACTS devices in the existing power system, the coordination control that shares high speed and excessive compensation ability without wastage of resources is essential. This paper presents coordinated control of multi-FACTS devices to provide efficient reactive power compensation based voltage regulation. At first, the characteristics of various categorical FACTS devices are presented in relation to response speed by incorporating high speed response FACTS (HSRF), medium speed response FACTS (MSRF) and low speed response compensator (LSRC). Finally, the MCR with SVC and MCR with FC coordination controls have been developed sequentially with minimal efforts of compatibility issues and compensation speed while ensuring an increase in the reactive power reserves for the SVC. The simulation is carried out on PSCAD/EMTDC to test the coordination control efficiency of several three phase multi-FACTS devices with series and parallel configurations and validated on a modified IEEE 30 bus power system. The results show that multi-FACTS coordination control increases the SVC reserves and is promising in providing voltage regulation for the power system under various scenarios.

Improvement of Power Quality in Distribution System using Photovoltaic based DPFC

In Modern Power System power quality is the main issue of the power companies. Improvement of power quality in distribution system using photovoltaic based DPFC is declared in this paper. Flexible AC Transmission System (FACTS) device which is known as distributed power flow controller (DPFC)is used. DPFC is derived from UPFC by eliminating common dc link between series and shunt converter. Unified power flow controller (UPFC) is widely used and control all parameters of the system. The UPFC handle the current and voltage with high rating; therefore, the cost of system is high. Therefore, distributed power flow controller (DPFC) is used due to high control capability, high Reliability & low cost. DPFC also measures the transmission angle, line impedance and bus voltage. In distribution system problems occur like voltage sag/swell, Harmonics etc. Photovoltaic system is used as source for DPFC.

GREY WOLF OPTIMIZER BASED OPTIMAL PLACEMENT OF MULTIPLE FACTS DEVICES IN THE TRANSMISSION SYSTEM UNDER DYNAMIC LOADING SYSTEM

The application of grey wolf optimization technique for multiple FACTS placement is presented in this paper for the reduction of total system losses and minimization of voltage deviation via optimal placement of Flexible AC Transmission System (FACTS) device. Grey wolf optimization (GWO) technique is inspired by social hierarchy and hunting behaviour of wolves and offers a right balance between exploration and exploitation during the search for global optimal. Series-shunt FACTS device; unified power flow controller (UPFC) is considered as a formidable device that can provides an alternative option for the flexible controllability and improvement of power transfer capability of a transmission lines. The analyses were conducted by increasing the number of UPFC in the network in order to evaluate the optimal number of FACTS devices that would give the least loss under maximum loading and contingency conditions. The efficacy of this proposed technique is demonstrated on 31-bus, 330 kV Nigeria National Grid (NNG) using MATLAB environment. The results show that optimal placement of FACTS device along with optimization technique provides a promising solution to the high power loss and voltage deviation bedevilling Nigeria National Grid.

A Comparative performance evaluation of a set of swarm intelligence based optimization algorithms for economic operation with FACTS devices in Power system

In this article an effective Reactive Power Management (RPM) method by using Flexible AC Transmission System (FACTS) has been proposed which minimizes the loss of energy, improve the power transfer capacity and reduce the overall cost of transmission network lines. The position of FACTS is optimized by two recently proposed heuristic optimization techniques, i.e., Gravitational Search Algorithm (GSA) and Teaching Learning Based Optimization (TLBO). The optimal positions of these FACTS are found by utilizing these GSA and TLBO algorithms. It is observed that by installing the FACTS in this optimal position improves the voltage profile with minimum installation cost. The overall performance of the proposed approaches is investigated by implementing it on IEEE 30-bus network.

Techno‐Economic Model for Reactive Power Planning Using Series‐Shunt Compensation Devices Under Load Demand in Power Transmission Network

This research article proposes a planning strategy of reactive power (VAR) in a power transmission system, because reactive power planning (RPP) is a topical issue in the energy sector. Basically, it is a qualitative effort to understand the mathematical principles, technical facets, and economic aspects with their utility in RPP prior to executing the proposed strategy through a unique solution model. Initially, the objective is formulated by measuring different cost components, such as VAR generation cost, line charging cost, flexible AC transmission system (FACTS) device operation cost, and cost due to real power loss. The vulnerable positions in the system are defined for the placement of FACTS devices after computing a set of mathematical methods. The installation bottlenecks of these devices are wiped out depending on some technical considerations and performances. Thereafter, a hybrid intelligence approach along with fundamental algorithms is applied to determine an optimal set of controlling variables in conjunction with active and VAR demand. The code profiling of the proposed approach is rendered on two interregional practical power networks. Finally, the responses of the benchmark functions and statistical outcomes are analyzed extensively to justify the trustworthiness of the proposed solution model.

An efficient NSCE algorithm for multi-objective reactive power system compensation with UPFC

<span id="docs-internal-guid-a50ef6a8-7fff-b6d7-8e58-d434be6097d4"><span>This paper proposes a novel approach based on the NSCE (elitist non dominated sorting cross entropy), for the optimization of the location and the size of a flexible AC transmission system device (FACTS) namely: unified power flow controller (UPFC) to achieve the optimal reactive power flow (ORPF). In the present work, the main objective is to minimize the real power losses, the cost investment of several UPFC and the deviation voltages using intelligent algorithms. The proposed study is multiobjective, in which, the power generator buses, the control voltages, the ratio tap changer of transformers and the reactive power injections from installed UPFC are considered as control variables. The proposed NSCE algorithm is validated on IEEE 30-bus test system. A comparison with elitist non dominated sorting genetic algorithm (NSGA-II) and a regularity model-based multiobjective estimation of distribution algorithm (RM-MEDA) is done and completed with hybridization of them.</span></span>

Design and Implementation of a Solar Panel Inverter as STATCOM Compensator

A power system suffers from different losses, which can cause tragic consequences. Reactive power presence in the power system increases system losses delivered power quality and distorts the voltage. As a result, many researches are concerned with reactive power compensation. Moreover, reactive power should not be transmitted through a transmission line to a longer distance. Thus, Flexible AC Transmission Systems (FACTS) devices such as static synchronous compensator (STATCOM), static volt-ampere compensator (SVC), and unified power flow controller (UPFC) are utilized to overcome these issues. The necessity of balancing resistive power generation and absorption throughout a power system becomes a big concern in the electrical systems for reactive power compensation. Static synchronous compensator STATCOM is a shunt device used for the generation or absorption of reactive power as desired. STATCOM provides smooth and fast compensation and power factor correction. In this thesis, a solar Static synchronous compensator takes the DC input from the solar panel and inverted utilizing an H-bridge inverter. This topology is used for reactive power compensation and power factor correction at the load side. The simulation was done using MATLAB Simulink simulation tools. The system model was built using a single solar array for DC input and controlled using perturbation and observe method to maximize its power output. The STATCOM model was built using for high power MOSFETs to perform H- bridge inverter. The STATCOM was controlled using a hysteresis band current control using a PI controller to inject the current into the system. A hardware prototype of STATCOM was built and controlled using an Arduino microcontroller. The simulation results have demonstrated the STATCOM model of reactive power compensation and correcting the power factor under different loads of conditions. It also highlighted the proportional relation between reactive power presence and the increased cost of electricity bills. The proposed smart meter of STATCOM gives accurate reading and measurement. Overall, the simulated results showed a satisfactory level of compensation of reactive power and power factor correction. The system contained three significant parts; solar array, H- bridge inverter, and the PI controller. The smart meter circuit was capable of displaying readings regarding input solar voltage, current, and power factor on the LCD screen.

Differential DC Component-Based Relaying Scheme for Transmission Lines

ABSTRACT Protection engineers and academicians are continuously working towards better relaying for modern transmission structures. This has become a requirement because transmission structure, nowadays, is being updated with new technologies, e.g. flexible AC transmission system devices. In this paper, it has been observed that the differential DC plays an important role in distinguishing the internal and external faults. A criterion is then developed based on this unique feature of the differential DC for the identification of faults in modern transmission lines. The performance of the proposed criterion has been tested with the help of simulation study carried out using EMTDC/PSCAD software for a variety of fault types with variations in fault location, fault resistance, fault inception angle, and compensation level. Furthermore, the performance of the proposed algorithm is also investigated for several rare conditions such as evolving faults, cross-country faults, noise in measurement, and measurement error. The results prove that the scheme is selective, accurate, and robust for uncompensated and series-compensated lines while it is accurate for low resistance faults in the case of a shunt-compensated line.

Investigation with UPFC-Fuel Cellof Steady and Transient Voltage Stability in Power Systems

Güç sistemlerinin sürekli ve geçici durum çalışmalarında Esnek AC İletim Sistemi (FACTS) cihazları tercih edilmektedir. FACTS cihazları içerisinde kontrol etme yeteneği en güçlü olan Birleştirilmiş Güç Akışı Kontrolü (UPFC)’dir. UPFC bara gerilimlerini reaktif güce bağlı olarak kontrol ederken, iletim hattını empedans ve akıma göre kontrol etmektedir. Bu çalışmada, Uluslararası Elektrik Elektronik Mühendisliği (IEEE) 14 baralı güç sisteminde UPFC’nin statik ve dinamik gerilim kararlılığı analizleri gerçekleştirilmiştir. Sürekli ve geçici durum için gerilim kararlılığı çalışma limitlerinin geliştirilmesi ve sistemin kararlı bölgede kalması için UPFC ile birlikte Enerji Depolama Sistemi (EDS) elemanlarından yakıt hücresi kullanılmıştır. UPFC-EDS ile sistemin gerilim-maksimum yüklenme parametre değerlerinin yanı sıra bara gerilim profilleri analiz edilmiştir. UPFC ile yakıt hücresinin birlikte kullanılması durumunda sistemin yüklenme parametre değerinin arttığı ve bara gerilim profillerinin iyileştiği görülmüştür.