Versatile model for power flow control using FACTS devices

In this paper, a new method to incorporating FACTS devices in optimal power flow (OPF) problem is presented. This method can provide an enhanced economic solution with the use of controllable FACTS devices. Two types of FACTS devices, thyristor controlled series compensators (TCSC) and thyristor controlled phase shifters (TCPS), are considered in this method. The specified power flow control constraints due to the use of FACTS devices are included in the OPF problem. The proposed method decomposes the solution of such modified OPF problem into two subproblems' iteration. The first subproblem is a power flow control problem and the second subproblem is a conventional OPF problem. The two subproblems are solved iteratively until convergence. Case studies are presented to show the effectiveness of the proposed method.

The Distributed Generator (DG) unit nowadays have become an integral part of any power system network. For the effective management of power flowing in a network, the size and position of the DG unit play the important role, but DG integration on the other side, also affects the operating characteristics of the system such as losses may be increased or decreased, variation in voltage and increases the cost for consumers or generators. To eliminate such effects, it is proposed that DG units can be integrated with FACTS devices, as these devices provide more reliability to the network. On the other side, load demand is also increasing day by day therefore, to fulfil the demand it is required to make use of these DG units at various locations. In this paper, an analytical approach with optimal power flow (OPF) method is used in MATLAB environment to identify the optimal location of DG and FACTS devices in maximum loading condition.

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.

Multi-objective adaptive clonal selection algorithm for solving optimal power flow considering multi-type FACTS devices and load uncertainty

FACTS devices have become significant tools for power flow study now-a-days. It has widely improved the power system reliability, operation capability and safety. It has also improved the robust control of power system. FACTS devices are generally made of power electronics devices and circuits. That’s why FACTS devices have appeared as the most outstanding innovation in the era of power electronics and power system. FACTS devices are of many types: TCSC, SVC, UPFC, IPFC, STATCOM etc. Among all the devices STATCOM has become one of the most important power system components for reactive compensation of power and Voltage stabilizing capability. In this paper we have a 6 BUS power system with a variable speed wind generator connected to a BUS. For the stochastic nature of the wind the BUS voltage becomes degraded. With the help of STATCOM, corresponding BUS voltage has been improved significantly which has been studied and simulated in our paper. We have simulated the whole system with MATLAB PSAT environment and analyzed the voltage response, rotor angle response, eigen values, participation factor etc.

The Optimal Power Flow (OPF) problem has been widely studied by researchers and electric industry practitioners for many years. Most of these studies use DC power flow equations to represent the transmission system. However, future power systems will have to deal with new challenges, including integration of renewable energy resources, HVDC links, FACTS devices, etc. The DC formulation may not be appropriate to comprehensively model the behaviour of the new system, for which AC formulations might be required. In this paper, the integration of point-to-point and multi-terminal VSC-HVDC in three nonlinear and DC OPF formulations is analysed using three different test systems. The Knitro and CPLEX solvers are used as optimisation tools. The results show that the generation dispatch resulting from the DC formulation could overload the VSC-HVDC and HVAC transmission branches in the real operation. Moreover, it is demonstrated that the nonlinear formulations can produce good quality solutions that preserve the secure operation of the transmission system.

In this paper a linear programming based optimal active power dispatch algorithm with coupled network model is presented that can take into account the effects of FACTS devices. The FACTS devices considered include the static representation of thyristor controlled series compensator, thyristor controlled phase shifter and unified power flow controller. The proposed algorithm combines the optimal active power flow problem and the specified power flow control problem into one algorithm and provides an enhanced economic solution with normal network constraints and specified power flow control constraints. Case studies are presented to show the effectiveness of the algorithm.

Power systems are transitioning toward renewable sources and electrification, introducing significant uncertainties in generation and demand that optimal power flow (OPF) methods must manage. Traditional deterministic methods struggle with these variabilities. Additionally, addressing uncertainty in OPF calculations incurs computational burdens due to the need for multiple evaluations across various scenarios. This necessitates the use of advanced surrogate models. However, these models require significant data for training, and surrogate-based optimization can yield unreliable results due to inaccuracies in constraint handling. To overcome these issues, this paper proposes a novel surrogate-based hybrid chance-constrained optimal power flow (HCC-OPF) methodology employing enhanced multi-fidelity graph neural networks (EMF-GNN) as power flow solver surrogates. This model integrates low-fidelity and high-fidelity simulations to significantly reduce training cost while maintaining high accuracy. We further enhance the robustness and accuracy of OPF solutions through a hybrid methodology that selectively uses exact power flow solver to correct surrogate inaccuracies near critical thresholds. Extensive testing on multiple IEEE systems under high-dimensional correlated uncertainty of load and generation shows the EMF-GNN model outperforms existing single-fidelity and multi-fidelity models. Furthermore, the proposed HCC-OPF methodology accurately solves OPF problems across various system sizes and conditions, exhibiting scalability and efficiency. Additionally, it effectively manages N-1 security constraints to further exhibit its robustness under operational challenges.

This paper develops an effective control framework for DC voltage control and power-sharing of Multi-Terminal DC (MTDC) grids based on an Optimal Power Flow (OPF) procedure and the voltage-droop control. In the proposed approach, an OPF algorithm is executed at the secondary level to find optimal reference of DC voltages and active powers of all voltage-regulating converters. Then, the voltage droop characteristics of voltage-regulating converters, at the primary level, are tuned based on the OPF results such that the operating point of the MTDC grid lies on the voltage droop characteristics. Consequently, the optimally-tuned voltage droop controller leads to the optimal operation of the MTDC grid. In case of variation in load or generation of the grid, a new stable operating point is achieved based on the voltage droop characteristics. By execution of a new OPF, the voltage droop characteristics are re-tuned for optimal operation of the MTDC grid after the occurrence of the load or generation variations. The results of simulation on a grid inspired by CIGRE B4 DC grid test system demonstrate efficient grid performance under the proposed control strategy.

This paper deals with the optimal location and parameters of Unified Power Flow Controllers (UPFCs) in electrical power systems. The UPFC is one of the most promising FACTS devices in terms of its ability to control power system quantities. Shunt FACTS devices are used for controlling transmission voltage, power flow, reducing reactive losses, and damping of power system oscillations for high power transfer levels. In this paper the optimal location of a shunt FACT device is investigated for an actual line model of a transmission line having series compensation at the center. As one of the most promising FACTS devices in terms of its ability to control power system quantities, UPFC Effect of change in degree of series compensation on the optimal placement of the shunt FACTS device to get the highest possible benefit is studied. The results obtained shown that optimal placement of the shunt FACTS device varies with the change in the level of series compensation.

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.

The paper develops a co-ordinated control scheme based on linear programming (LP) for the secondary control in a power system where it is required to restore system security in relation to voltages and power flows, and, simultaneously, minimize the network loss, following a system disturbance or contingency. The secondary control scheme proposed is more general than the classical secondary voltage control where only voltages are considered. The scheme automatically adjusts the reference settings of the power system controllers to achieve the objectives specified in the secondary control. The algorithm is derived on the basis of the linearized power system model the parameters of which are determined online using the information obtained from the phasor measurement units and/or state estimation. The LP-based scheme is suitable for online application in secondary control. Representative results based on a test power system with FACTS devices and subject to disturbance/contingency are included in the paper.

Summary form only given. This paper presents a computational approach for an offline measurement based design of an optimal damping controller using adaptive critics for a new type of FACTS device - the gate controlled series capacitor (GCSC). Remote measurements are provided to the controller to damp out system modes. The optimal controller is developed based on the heuristic dynamic programming (HDP) approach. Three multi-layer perceptron (MLP) neural networks are used in the design - the identifier/model network to identify the dynamics of the power system; the critic network to evaluate the performance of the damping controller; and the controller network to provide optimal damping. This measurement based technique provides an alternative to the classical linear model based optimal control design. The eigenvalue analysis of the closed loop system is performed with time domain responses using the Prony method. Analysis of the simulation results show potential of the HDP based optimal damping controller on a GCSC for enhancing the stability of the power system.

Interline power flow controller (IPFC) is a new concept of flexible AC transmission system (FACTS) controller with the unique capability for series compensation with the unique capability of power flow management among multi-line of a substation. Generally speaking, the IPFC employs a number of voltage sourced converters (VSCs) linked at the same DC terminal, each of which can provide series compensation for the selected line of the transmission system. Through common dc link, any inverters within the IPFC are able to transfer real power to any other and thereby facilitate real power transfer among the line. This paper, for simplicity, proposes the powerful tool applied on 3-machine 9-bus test system, basic test system with one loop, and optimal power flow (OPF) method. We can solve the OPF for the minimum cost and balance the entire power flow at the satisfied solution.

Voltage stability is an important issue in power system operation. Flexible AC transmission systems, so-called FACTS devices, help to improve voltage stability and minimize real power losses. The effectiveness of FACTS devices depend on their proper location and rating. This paper presents a method, based on line flow sensitivity factors such as bus voltage stability index and line voltage stability index, to find suitable locations of multi-type FACTS devices. Also this paper proposes an application of particle swarm optimization (PSO) and harmony search algorithm (HSA) in optimizing the rating of FACTS devices. The proposed approaches are evaluated with three different objective functions namely, minimization of real power loss, improvement of voltage profile and enhancement of voltage stability. The performance of proposed methods is analyzed on IEEE 14 bus system by implementing FACTS devices such as static var compensator (SVC), thyristor controlled series capacitor (TCSC) and unified power flow controller (UPFC).The analysis shows that there is a reduction in real power loss and improvement in voltage stability and voltage profile of the system after employing FACTS devices. It also shows that both real power loss and bus voltage stability index (BVSI) have been reduced more with FACTS ratings obtained from PSO than with that from HSA.