PAT: a power analysis toolbox for MATLAB/simulink

Flexible AC Transmission System (FACTS) controllers are advanced power electronic devices employed in electrical power systems to enhance system stability, reliability, and power transfer capabilities. These controllers enable dynamic and flexible control of various transmission parameters such as voltage, current, impedance, and phase angle, thereby improving the overall power system performance. FACTS devices are broadly classified into series, shunt, series- series, and series-shunt configurations, each designed to manage reactive power and regulate voltage either by injecting voltage in series or current in shunt with the transmission line. Well-known FACTS devices include Static Var Compensators (SVC), Static Synchronous Compensators (STATCOM), Thyristor Controlled Series Capacitors (TCSC), Static Synchronous Series Compensators (SSSC), and Unified Power Flow Controllers (UPFC), each serving specific roles in power flow control, voltage regulation, and transient stability enhancement. The integration of these controllers provides significant benefits such as increased transmission line capacity, improved voltage stability, minimized transmission losses, and damping of power system oscillations. They are capable of rapid response during transient disturbances, effectively mitigating voltage collapses and enhancing system resilience against faults and contingencies. FACTS controllers not only improve steady-state operational parameters but also address dynamic stability and transient conditions, enabling power systems to operate closer to their stability limits while maintaining security. Their deployment helps avoid costly infrastructural expansions by optimizing existing transmission assets, which is critical given environmental and economic constraints. Recent advances in semiconductor technologies and control algorithms have made FACTS devices more reliable, efficient, and adaptable to modern grids, including renewable integration and deregulated power markets. In summary, FACTS controllers play a vital role in modern power systems by providing flexible, efficient, and reliable solutions for power flow management, voltage control, and system stability enhancement, thereby supporting the evolving demands of today's complex electrical networks.

This paper deals with a new operation strategy of FACTS (flexible AC transmission system) device, especially the series compensating device like TCSC (thyristor controlled series compensator) using the linearized sensitivity derived in this paper. In case of a line overflow under contingency state or line congestion at normal state, the FACTS device must change its operating point to relieve the flow congestion and eventually to increase the system security level. In this paper, line flow sensitivity to FACTS device is derived analytically. The sensitivity derivation is based on the DC flow model under the assumption that the generator dispatch is maintained. The power flow control algorithm based on the sensitivity analysis proposed in this paper has several advantages; it is easy to compute, its computation time is short, and its form is very simple etc. Each FACTS device installed in the power system changes its reactance according to the dynamic algorithm proposed in this paper. Its direction and the amount of reactance change depend on the sensitivity of each device. The proposed algorithm in this paper is tested and verified on the IEEE 39 system.

Chaotic krill herd algorithm for optimal reactive power dispatch considering FACTS devices

Voltage instability and voltage collapse have been considered as a major threat to present power system networks due to their stressed operation. It is very important to do the power system analysis with respect to voltage stability. Flexible AC Transmission System (FACTS) is an alternating current transmission system incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability. A FACTS device in a power system improves the voltage stability, reduces the power loss and also improves the load ability of the system. FACTS have made the power systems operation more flexible and secure. Amongst the several FACTS controllers, the Unified Power Flow Controller (UPFC) is most effective to improve the enhancement of voltage stability and reduces the power loss. This study investigates the application of Particle Swarm Optimization (PSO) to find sizing of Unified Power Flow Controller (UPFC) device to minimize the voltage stability index, total power loss, load voltage deviation, and cost of FACTS devices to improve voltage stability in the power system. A new model is proposed in this thesis to improve existing power-based model by using the Norton Equivalent Theorem. The proposed model can be integrated with the Equivalent Current Injection (ECI) power flow model easily. By ECI algorithm, it is much quickly and precisely to implement power flow calculations. Finally It is observed from the results that the voltage stability margin is improved, the voltage profile of the power system is increased and real power losses also reduced by optimally sizing UPFC device in the power system. Index Terms: Voltage stability, Unified Power Flow Controller (UPFC), Equivalent -Current Injection (ECI), Modified particle swarm optimization (MPSO)

Growing number of wind turbines is changing electricity generation profile all over the world. This brings challenges for power system operation, which was designed and developed around conventional power plants with directly coupled synchronous generators. In result, safety and stability of the electrical network with high wind energy penetration might be compromised. For this reason transmission system operators (TSO) impose more stringent connection requirements on the wind power plant (WPP) owners. On the other hand flexible AC transmission systems (FACTS) devices offer enhancement of grid stability and can facilitate grid code compliance for WPP. In this paper state-of-the-art in FACTS for WPPs with AC connection is given. FACTS devices with their properties are described. HVDC, which in literature is also often recognized as FACTS device, is out of this paper scope. Academic and industrial research in FACTS applicability for WPPs is summarized. Examples of few existing FACTS applications for wind farms are given.

High electricity growth in Nigeria coupled with an obsolete transmission network has necessitated novel approaches to power grid optimization. This paper compares the two technologies- Solar Photovoltaic (PV) system and Flexible AC Transmission System (FACTS) devices, in particular Static Synchronous Compensator (STATCOM), individually embedded to the 330 kV Nigeria 48-bus transmission grid in a simulation-based study. With the assistance of Power System Analysis Toolbox (PSAT) in MATLAB, this paper summarizes how these are the technologies that developed to increase Available Transfer Capability(ATC), gain better voltage stability and change power flow under normal as well as under Single Line Contingency. Five weak buses were used for the simulation featuring poor voltage performance and three deployment confirmations were studied (FACTS, PV, and the the base case without any enhancement). The results prove that solar PV and FACTS devices can independently be used to enhance the performance. ATC enhancement of FACTS deployment are almost 35.7% in ATC whereas solar PV gave an ATC enhancement of 29.6%. Voltage variation was decreased by 24.6% and 29.4% in the FACTS-only and PV-only case respectively, over the base case. These findings imply that FACTS has more transfer capacity, while PV systems have more voltage support. The results of this study offer valuable knowledge for power system planners and decision makers in developing countries where additional infrastructure development may not be feasible or immediate, but a need to reinforce the transmission network using flexible and low-cost solutions exists.

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

This paper presents the solution of optimal power flow (OPF) of power system with flexible AC transmission systems (FACTS) devices by using opposition-based gravitational search algorithm (OGSA). OPF problem with FACTS is solved by the way of minimizing an objective function which reflects cost of generation, emission and active power transmission loss. FACTS devices considered include thyristor controlled series capacitor and thyristor controlled phase shifter. The proposed approach has been examined and tested on the IEEE 57-bus test power system. The obtained results are compared with those reported in the literature. Simulation results demonstrate the superiority and accuracy of the proposed algorithm. Considering the quality of the solution obtained, the proposed algorithm seems to be effective and robust to solve the studied problem.

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

Transmission systems are under stress and need to be upgraded. Better utilization of the existing grid provides a fast and cheap alternative to building new transmission. One way to improve the utilization of the transmission network is power flow control via flexible ac transmission system (FACTS) devices. While FACTS devices are used today, the utilization of these devices is limited; traditional dispatch models (e.g., security constrained economic dispatch) assume a fixed, static transmission grid even though it is rather flexible. The primary barrier is the complexity that is added to the power flow problem. The mathematical representation of the DC optimal power flow, with the added modeling of FACTS devices, is a nonlinear program (NLP). This paper presents a method to convert this NLP into a mixed-integer linear program (MILP). The MILP is reformulated as a two-stage linear program, which enforces the same sign for the voltage angle differences for the lines equipped with FACTS. While this approximation does not guarantee optimality, more than 98% of the presented empirical results, based on the IEEE 118-bus and Polish systems, achieved global optimality. In the case of suboptimal solutions, the savings were still significant and the solution time was dramatically reduced.

Optimal allocation of FACTS devices for static security enhancement in power systems via imperialistic competitive algorithm (ICA)

A generalized approach for determination of optimal location and performance analysis of FACTs devices

Flexible AC transmission system (FACTS) has the control characteristics of efficiency, flexibility and reliability. The introduction of FACTS in power system is superior to any other control methods, and different FACTS devices have different features. In this paper, a comprehensive evaluation index system is developed to study a variety of comparisons on different FACTS devices. The proposed index takes power flow controllability as its main indicator, and loss reduction, static voltage stability improvement and load shedding reduction as complementary indicators. Finally, the peak load case in 2016 of a province is adopted for case studies. The results not only show that the proposed comprehensive evaluation index is systematic, scientific, practical, but also show the superiority of unified power flow controller (UPFC).

In this paper, a fully fledged optimal power flow (OPF) algorithm with flexible AC transmission systems (FACTS) devices has been developed and presented aiming at the advancement of how FACTS equipment impacts on the security and economy of the wider power network. The proposed modelling uses Newton’s method along with Lagrangian multipliers, leading to an ecient algorithm that can handle practical power networks independence of initial settings of FACT controllers parameters. Newton’s method provides a suitable vehicle for incorporating the newly developed nonlinear, linearized FACTS models. In this paper, mainly a firing angle-based thyristor controlled series compensators (TCSC) model, a coordinated two-voltage source unified power flow controller (UPFC) model have been developed and presented in details and can easily be extended to other modern FACTS devices such as interline power flow controller (IPFC) and generalized unified power flow controller (GUPFC). The proposed model has capability of converting multi-objective functions into single objective and also can be extended to multiple multi-type FACTS devices. The performance of the proposed model has been validated for IEEE 30 bus system and the solutions so obtained are presented in detail.

This paper proposes a reactive power planning model, which incorporates flexible AC transmission system (FACTS) devices. The optimal location of multi-type FACTS devices and their control parameters are optimized by a novel bacterial swarming algorithm (BSA) to minimize the real power losses and also to improve voltage profile. The simulation studies have been undertaken on both IEEE 30-bus and 118-bus test systems. Simulation results show that the performance of the power system is improved with multi-type FACTS placed optimally in the reactive power planning model. The advantage of using BSA to determine the location of FACTS devices is demonstrated, in comparison with two other evolutionary algorithms (EAs), i.e., genetic algorithm (GA) and particle swarm optimizer (PSO).