Optimal Placement and Sizing of Multi-type Facts Devices Using PSO and HSA

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)

The control of reactive power in any transmission network is important to ensure voltage stability of the entire power grid. Flexible AC Transmission Systems (FACTS) have proven to be efficient in providing controllability to reactive power for voltage stability management. However, the performance of the FACTs devices largely depends on the installation location. A fuzzy logic technique for finding the optimal location for the Thyristor Controlled Series Capacitor (TCSC) and Static Var Compensator (SVC) FACTS devices with specific security indices is proposed in this paper. The proposed indices for SVC placement are the Loss Sensitivity Factor (LSF) and critical voltage, while the considered indices for TCSC placement are the loss sensitivity factor (LSF) and line stability index (LSI). The indices are fuzzified to obtain a suitability index which determines the suitable line(s) and node(s) accordingly. The proposed approach is implemented on the IEEE 30 bus network. The SVC reduced the overall transmission loss by 1.6%, while the TCSC reduced the transmission loss by 4.94 %. The loading margin also improved by 24.87% and 2.92% using SVC and TCSC, respectively. The voltage profile also remained close to 1 p.u under varying load conditions. The results indicate the effectiveness of the proposed technique at reducing transmission loss, improving voltage stability and improving voltage profile simultaneously.

Voltage profile improvement and loss reduction is an important issue in power system especially under loaded condition. In this paper, two FACTS controllers like Static Var Compensator (SVC), and Thyristor Controlled Series Capacitor (TCSC) are considered for voltage profile improvement and loss reduction. The voltage profile improvement and loss reduction using FACTS devices is a problem of combinatorial non linear optimization. Small population based particle swarm optimization (SPPSO) has been used to solve this combinatorial non linear optimization problem. To enhance the diversity of particle in small population, mutation operator and concept of regeneration is used. The optimizations are performed on two parameters: the location and the values of SVC and TCSC. The proposed method is tested on modified IEEE 30 bus system for two operating conditions. To validate the accuracy of results a comparison with conventional particle swarm optimization (CPSO) has been made. The results show the effectiveness of SPPSO than CPSO in loss reduction and voltage profile improvement.

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 proposes a Symbiotic Organisms Search (SOS) algorithm based solution to optimize the control variables simultaneously to optimize the power system real power loss and voltage stability limit. This issue can be mathematically formulated as a problem of nonlinear equality and inequality limited optimization, with an objective function integrating real power loss and voltage stability limit. The problem formulation included transformers taps, unified power flow controller and its parameters as control variables. The efficacy of the proposed algorithm has been tested on Indian 24-bus system. The simulation results obtained with the proposed algorithm are compared with the real coded genetic algorithm (RCGA) for a single objective of minimizing real power loss and multi-objective minimization of real power loss and maximization of voltage stability. Results from simulation demonstrate the ability of the proposed algorithm in solving the optimization problem.

In this paper, a hybrid tabu search and simulated annealing (TS/SA) approach is proposed to minimize the generator fuel cost in optimal power flow (OPF) control with multi-type of flexible AC transmission systems (FACTS) devices. The problem is decomposed into the optimal setting of FACTS parameters subproblem that is searched by the hybrid TS/SA approach and the OPF with fixed FACTS parameters subproblem that is solved by the 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). Test results on the modified IEEE 30 bus system with multi-type of FACTS devices indicate that the proposed hybrid TS/SA approach can obtain better solutions and require less CPU times than genetic algorithm, SA, or TS alone. Using multi-type of FACTS devices results in less total generator fuel cost than using individual FACTS device.

The Thyristor Controlled Series Compensator (TCSC) and Static Var Compensator (SVC) are variable impedance Flexible AC Transmission Systems (FACTS) Controllers. A combination of the TCSC and the SVC installation is proposed to acquire superior performance for the power system. The coordination between the two pieces of equipment is designed with the SVC treated as the supplement of the TCSC. When operation of the TCSC is constrained by the inherent limitation of equipment, such as due to the firing-angle limitation of the thyristors, the adjustable SVC can supply the auxiliary support to improve the overall performance. The voltage and angle stability margins can be greatly improved with the compatible control schemes of the TCSC and the SVC.

Impact of FACTS devices on the voltage stability is usually determined with the power-flow calculations. Results, gained in this way, is sometimes difficult, if not impossible, to explain in qualitative way and to draw the general conclusions. Therefore analytical approach using simple basic models may submit more insight into basic features of tested device behavior in an electric power system (EPS) than numerical calculations at real-like system model. The paper presents such an approach for Unified Power-Flow Controller (UPFC), which may be considered a synonym for multi-parameter controlled FACTS device. The basic goal is to acquire impact of an UPFC on voltage stability enhancement and voltage control respectively. Therefore it is positioned into the standard model, widely used for voltage stability representation purposes. In the paper the mathematical solution of the problem is explained and the impact of the UPFC on voltage stability is shown.

This paper investigates the applicability of an integrated approach for the enhancement of voltage stability margin and there by the wind penetration of large wind integrated power systems. The proposed approach involves in two objectives; the identification of weak buses in the given power systems, enhancement of voltage stability margin of the weak buses and there by the wind penetration by optimal placement and tuning of Flexible AC Transmission System (FACTS) controllers. Multiple of one type of FACTS controller namely SVC is used in the current analysis for placement in suitable weak buses. Weak bus identification is carried out byconducting the tangentvectoranalysis. Voltage stability enhancement at high wind penetration is assessedby using the dynamic voltage security index, the index for accessing the proximity of voltage collapse under dynamic loadingconditions. Theoptimization of grid control parameters are carried out by using Particle Swarm Optimization (PSO) by incorporating FACTS Controllers. The developed algorithm have beentested on Wind integrated Kerala grid 25-bus practical system.

The demand of quality & reliable power by the consumers is increasing day by day in a tremendous manner. Everyone needs good quality of power with out any disturbances or interruptions. Also due to large no of present day consumers, the power system needs a boosting mechanism in order to capitalize the complexity of power system. So a reliable technology of FACTS(Flexible AC Transmission System) is introduced in the power system to enhance the flexibility of power grids. FACTS devices are power electronics based controllers & improve the system performance by shunt or series compensation. They injects or absorbs reactive power to/from the power system at the time of need. In this paper a shunt type of FACTS controller such as SVC(Static Var Compensator) is considered for stability enhancement & loss minimization in a nine bus power system. SVC consists of TCR(Thyristor Controlled Reactor), TSC(Thyristor Switched Capacitor), a fixed capacitor connected parallel to the line & filter elements for harmonic reduction. Here the enhancement of voltage stability & loss minimization is analyzed in terms of voltage magnitude variation & overall real & reactive power losses at each bus w.r.t the location of installation of SVC. Firstly Load flow study carried out for an uncompensated system & then for SVC compensated system by changing the location of installation of SVC from bus1 to bus9. And also thereby specifying the optimal location of SVC by analyzing the load flow data in terms of voltage magnitude variation & overall losses. All the performance analysis has been performed using MATLAB/SIMULINK software.

Enhancing voltage stability and LVRT capability of a wind-integrated power system using a fuzzy-based SVC

Gerilim kararlılığı, güç sistemlerinde incelenmesi gereken önemli bir konudur. Sürekli artan elektrik enerjisi talebi, artan talebi karşılamak için yeni elektrik üretim santrallerinin kurulumu ve güç sistem arızaları gerilim kararlılığını olumsuz yönde etkilemektedir. Günümüzde gerilim kararlılığını iyileştirmek için güç sistemlerinde Esnek Alternatif Akım İletim Sistemleri (FACTS cihazları) kullanılmakta olup, ayrıca enerji talebini karşılamak ve gerilim kararlılığını iyileştirmek için güç sistemlerine Dağıtık Üretim Kaynakları (DGs) entegre edilmektedir. Bu çalışmada, IEEE 30 baralı güç sistemi ile Kuzeybatı Anadolu (KBA) güç sistemi, gerilim kararlılığı bakımından temel (nominal), aşırı yüklenme ve hat kopması durumlarında incelenmiştir. İncelenen güç sistemlerine FACTS cihazlarından Statik Var Kompanzatör (SVC) ve Tristör Kontrollü Seri Kapasitör (TCSC), DGs’lerden ise Yakıt Hücresi (YH), Güneş Enerji Santrali (GES) ve Rüzgâr Enerji Santrali (RES) ayrı ayrı ve birlikte bağlanmıştır. Güç sistemlerinin bara gerilim değerlerinde ve yüklenme parametresinde meydana gelen değişimler analiz edilmiştir.

Voltage stability analysis is the major concern in order to operate any power system safely. In this context considerable research work has been carried out to improve the voltage stability. FACTS devices can used for controlling power flow, transmission voltage, improving voltage profile, and reducing reactive losses. In this paper two different FACTS devices have been selected to place in suitable location to improve voltage stability in power system. The mathematical model of the power system equipped with a Static VAR Compensator (SVC) and Static synchronous compensator (STATCOM) separately is systematically derived and the parameters of the shunt FACTS are modeled into the power flow equations and used in the control strategy. The two models of FACTS are developed for the IEEE 30-bus system and implemented in Newton-Raphson load flow algorithm in order to control the voltage of the bus to which the shunt FACTS is connected. In this study a MATLAB written program is used for the solution of power flow problems and calculate voltages, active and reactive power at each bus of IEEE 30-bus system.

In order to reduce power losses in a power system and to improve voltage profile, researchers have examined and studied optimizing Photovoltaic Power distributed generation (DG) which is location and size in a power system, but the results have some drawbacks. Several approaches developed to make this important issue more efficient, including coming up with new algorithms and improving those already in existence. Many of the proposed algorithms are only concerned with the real power loss, however. Voltage stability control is a critical factor in modern power systems, which makes incorporating reactive power losses in optimizing DG allocation for voltage profile improvement necessary. The goal of this work is to solve this issue by combining Genetic Algorithm and Improved Particle Swarm optimization to optimize DG size and location by considering both real and reactive power losses. Power loss sensitivity factors and real and reactive power flow factors used in identifying which buses will receive DGs. A MATLAB-based program was developed and tested on a test system using distributed generators, considering the proposed method. As compared to Genetic Algorithm, Particle Swarm optimization and Improved Particle Swarm optimization methods, the Hybrid Genetic Algorithm Improved Particle Swarm optimization method is better for reducing both real and reactive power losses.

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.