Power Flow Controller Research Articles

A robust single ended disturbance detection scheme for superconducting fault current limiter integrated UPFC compensated line

The occurrence of short circuit events in a high voltage or extra high voltage transmission system may result in a fault current with high magnitudes. Additionally, the inclusion of Unified Power Flow Control (UPFC) contributes to fault current. In such a scenario, the use of Superconducting Fault Current Limiters (SFCLs) is very vital because of their better technical performance to limit fault currents. However, inclusion of SFCL may cause difficulties for existing disturbance detection units. To overcome such an issue, this manuscript aims for a new disturbance detection approach based on sliding window Singular Spectrum Analysis (SSA). The proposed method begins with the reconstruction of the fault signal using SSA and then computes the transient error by subtracting the reconstructed fault signal from the original signal. This transient error is used as a fault detection index (FDI) which is also used to classify the faulty section. The superiority of the presented technique is tested for two different UPFC compensated power networks equipped with two different SFCLs, modeled using EMTDC/PSCAD 5.0. The obtained results show the effectiveness of the addressed method, obtained by simulating different adverse scenarios (fault and non-fault) which justify the real-time application of the proposed protection method.

A constrained sequential power flow algorithm for VSC-high voltage DC grids compensated by PFCs

Upcoming HVDC systems will include multiple power flow controllers (PFCs). Frequent activation/deactivation of the PFCs will complicate the implementation of unified DC power flow (PF) algorithms; because, the DC system equations, variables, and the Jacobian matrix would be changed. To address these challenges, decoupled sets of equations are developed for the uncompensated HVDC grid and PFCs, and a sequential DC PF algorithm is proposed. The PF equations of the uncompensated HVDC grid are solved using the Newton-Raphson (N-R) method and the grid voltages are computed over the first sequence. The impacts of PFCs are proposed to be modeled through constant and artificially injected powers (AIPs) to the grid's buses. The computed system voltages are transferred to the second sequence to solve equations of each PFC, compute their variables (duty cycle and voltage of their intermediary capacitor), and update their associated AIPs. A modular method is also proposed to handle the system's technical limits by properly activating PFCs and altering system references. Several static and dynamic simulations are conducted to verify the accuracy, efficiency, and computational burden of the newly proposed AIPs, sequential algorithm, and handling method.

Multi-Objective Optimal Power Flow Incorporating Flexible Alternating Current Transmission Systems: Application of a Wavelet-Oriented Evolutionary Algorithm

This article presents a meta-heuristic hybrid algorithm to solve multi-objective optimal power flow (MOOPF) taking into account multi-fuel constraint. Four different objective functions, which comprise total generation cost, emission, real power transmission losses, and voltage deviation, are simultaneously considered in the proposed MOOPF. Furthermore, two types of flexible alternating current transmission system (FACTS) devices are utilized including thyristor controlled series compensator (TCSC) and unified power flow controller (UPFC). Considering all of the aspects referred to above makes the traditional OPF problem more complicated; hence, it is necessary to approach the problem by a powerful optimization algorithm. Toward this end, this article develops a hybrid algorithm oriented to shuffled frog leaping algorithm (SFLA) and particle swarm optimization (PSO), called hybrid wavelet mutation (WM) based SFLA-wavelet mutation based PSO (HWM2SFLA-PSO). Obtained results validate the effectiveness of the proposed hybrid algorithm in solving different forms of the OPF problem on IEEE test systems compared to those available in the literature. Moreover, the comparison substantiates the superiority of the proposed HWM2SFLA-PSO algorithm in terms of execution time, quality of solution as well as preventing from convergence to local optima, to name but three.

Sensitivity analysis index to determine the optimal location of multi-objective UPFC for improvement of power quality parameters

Today, advanced technologies are used for the reliable operation of power systems. In order to access a reliable and practical function in the systems, it is necessary to use precise control systems with higher efficiency in the systems to minimize the problems of the distribution system. Devices that are made on the basis of power electronics have wide applications in power systems today. These devices, which are called FACTS devices, provide the possibility of improving energy transmission with the least investment cost, as well as quick control of power system problems. FACTS devices are placed in series, parallel or series-parallel transmission lines and control the operation of distribution systems in permanent states as well as the dynamic behavior of the system in transient states. FACTS devices are an effective method to solve the problems and limitations of lines. Transmission and replacement networks are used to create new lines in the network. From the point of view of power distribution control, FACTS controllers can be placed anywhere in the transmission line, but the elements are most effectively used when they are placed at the most critical point. Unified Power Flow Controller (UPFC) is one of the most important FACTS devices that can improve parameters. The quality of power used in the power system depends on the effect of this controller in improving the loss reduction, reducing the total harmonic distortion (THD), and removing the clogged lines to their proper location in the power system. This device is capable of all different effective parameters at a time. These parameters usually include voltage, impedance, and phase. This paper uses a new sensitivity analysis index to determine the optimal size and location of the UPFC to improve the power quality parameters of the distribution system. The proposed method is evaluated on the IEEE 14-bus network in the Simulink environment of MATLAB software. Finally, according to the simulation results and the results obtained from the base network, it is determined that using the proposed sensitivity analysis index in UPFC location, losses Network, total harmonic distortions (THD) and eclipses Network lines are much improved. The results indicate that the proposed method has provided a good answer to determine the optimal size and location of UPFC to improve power quality parameters. Using the results of the sensitivity analysis method, the best place to install UPFC in the power grid, mode number 6 between buses 2 and 11 is obtained. and The amount of network power losses after sensitivity analysis, compared to the base network Active losses of about 55% and reactive losses of about 11% deceased, Due to the circular structure of the network, the current passing through the lines is different depending on the amount of load in the bases near that line, and with the presence of UPFC, the network is optimized and the current passing through the lines is also reduced. 4) Percentage of total harmonic distortion (THD) mains voltage before the presence of UPFC is about 27.12%, which after installation in the 6th place with a maximum size has been reduced to about 11.11%.

HVDC grids stability enhancement through the integration of battery energy storage systems

AbstractIn high voltage direct current (HVDC) grids, the reference values of power controllers are normally adjusted based on the DC‐link voltage as the DC voltage is regulated by the droop controllers. As a matter of fact, except for the DC slack bus, there is a trade‐off between power‐sharing and voltage regulation of all the remaining HVDC buses. The main issue with this control strategy is that in case of contingencies, significant voltage and power oscillations throughout HVDC grids can be expected. To address such issues, the integration of a battery energy storage system into HVDC grids through a multi‐port DC/DC power converter is investigated in this paper. The DC/DC converter used in this paper consists of three ports: (1) two ports are connected in cascade with the intended DC transmission line, formerly named cascaded power flow controller, and (2) the third port is for the integration of the battery energy storage system to form a multi‐functional device. Therefore, the proposed framework can potentially achieve small‐signal stability enhancement and regulate/adjust the power throughout the HVDC grids.

Unified Power Flow Controller: A Brief Review on Tuning and Allocation for Power System Stability

The Power System can become unstable due to disturbances. To enhance system stability the Unified Power Flow Controller (UPFC) is tuned and allocated in the System. In this paper, a brief review of UPFC tuning and allocation studies for power systems stability is presented. The databases consulted for literature are the IEEE Xplore, ScienceDirect, Google Scholar and IOP Publications. The search terms used are Allocation, Tuning, UPFC, Power System and Stability to find the literature used in this review. A total of 26 Journal articles and conference papers were found and reviewed based on tuning and allocation studies. The Researchers applied Fuzzy coordination, Genetic Algorithm (GA), Particles Swarm Optimization (PSO), Grey Wolf Optimization (GWO) and Linear Quadratic Tracker (LQT) to tune the UPFC for enhancing power system stability. For studies on UPFC allocation in power systems, the Researchers applied frequency response of power system transfer function, power flow, Tabu Search (TS), PSO and GA. For allocation based on optimization, the Researchers minimized power losses, voltage index and investment costs considering equality and inequality constraints.

Robust Regulation of a Power Flow Controller via Nonlinear Integral Action

This article considers a robust output set-point tracking problem for an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$</tex-math> </inline-formula> -terminal power flow controller (PFC) for meshed dc micro-grids. The PFC is a power electronics device used to control the power flow at a node in the meshed grid and may act as a dc circuit breaker. The system is modeled by state-space bilinear dynamics coupled with a polynomial output. In the proposed design, the plant is first extended with an integral action processing the regulation error. The cascaded model composed of the plant and the integrator is then stabilized using a saturated state-feedback law, designed with a forwarding approach. An anti-windup function is added to cope with transient saturations. A tuning method is proposed to set the controller gains along the available degrees of freedom with respect to a cost function. The stability of the closed loop is guaranteed for any compact set of initial conditions and for small parametric variations around the nominal set point. Experiments have been carried out and these properties are successfully assessed on a tenth-scale experimental setup.

Power flow control: Solutions for a modern smart grid [Book review

Power flow control: Solutions for a modern smart grid [Book review

Isolated UIPC-intertied AC-DC microgrids operation with novel dynamic flexible loads model

This work discusses the islanding operation of hybrid microgrids (HµGs) interconnected by a unified interphase power controller (UIPC). It is illustrated that considering islanding operation of HµG, the problem of power dispatch among intertied AC and DC µGs, as well as voltage and frequency control, can be handled by UIPC. The power dispatch among various AC and DC µGs using UIPC is analyzed and formulated through defining a simple demand condition function (DCF). A new control structure is proposed for the series power converter of the UIPC which enjoys the robustness of sliding mode control (SMC) concept and adopts a new energy management system (EMS) with embedded decision-making. This provides a fast, robust, and simple power flow control unit which acts as a general supervisory system for the UIPC and islanding operation of HµG. Also, a novel generalized dynamic model for flexible loads has been proposed. These loads have been directly controlled through UIPC supervisory system here. The analytical response of the proposed flexible load model is discussed and further developed using the nonlinear autoregressive-moving-average artificial neural network (ANN) model. The Levenberg-Marquardt learning algorithm is used to train the network based on the model estimation error. Besides, a new model predictive-based optimal control scheme is proposed for the flexible load. Simulation results using MATLAB support the usefulness of the proposed UIPC-based islanded HµG platform.

A Multi-Port DC Power Flow Controller Integrated With MMC Stations for Offshore Meshed Multi-Terminal HVDC Grids

Multi-terminal dc (MTDC) systems have the potential to facilitate the integration of offshore wind farms. A dc power flow controller (DPFC) is necessary for meshed multi-terminal high voltage dc (HVDC) grids to regulate the power flow in dc lines. However, DPFCs based on modular multilevel converters (MMCs) require two dc-ac conversion stages and an extra ac transformer, which increases the cost and loss for offshore platforms. This paper proposes a multi-port DPFC that is integrated internally into the offshore MMC station, eliminating the need for an extra transformer and reducing dc voltage ripple. Additionally, the full bridge submodules (FBSMs) in the DPFC can further reduce the number of FBSMs required in the MMC station for dc fault blocking. The proposed DPFC is composed only of cascaded FBSMs connected to the arms of the offshore MMC station, which can exchange power directly with the MMC valve to achieve power balance. By using the MMC station, the proposed DPFC requires a small kVA rating, approximately 1%-5% of the total system power rating. The performance of the proposed DPFC is validated through simulation of a hybrid system of the IEEE 39 bus and the Cigre HVDC benchmark, and also through down-scale experimental testing.

Hierarchical Energy Management of Networked Flexible Traction Substations for Efficient RBE and PV Energy Utilization Within ERs

The particular split-phase traction power system of AC electrified railways (ERs) restricts its regenerative braking energy (RBE) utilization and photovoltaic (PV) penetration. Networked flexible traction substation (FTSS) operation is a promising paradigm to address this restriction. Therefore, this paper proposes a networked FTSS system architecture that ties adjacent FTSSs via unified power flow controllers (UPFC) at sectioning posts (SPs), which matches the technical characteristics of split-phase ERs obtaining the lower capacity requirement. Correspondingly, a real-time hierarchical energy management strategy is designed. The networked FTSS management level optimizes the energy cooperation among FTSSs, i.e., the exchange power at SPs. It aims at maximizing the global RBE and PV energy utilization and shaving the maximum demand of each FTSS. At the individual FTSS management level, each FTSS autonomously regulates the power outputs of the local back-to-back converter and energy storage system to maximize the local RBE and PV energy utilization and improve the local power quality issues. These two energy management levels operate independently with different time scales, making the networked FTSS system have good extensibility and reliability. Finally, the performance of the proposed scheme is verified via hardware-in-the-loop tests.

Implementation of Grid-Connected Wind Energy during Fault Analysis Using Moth Flame Optimization with Firebug Swarm Optimization

In modern trends, the voltage profile has become increasingly critical when incorporating wind turbine energy sources because of changes in fault ride-through capabilities throughout voltage reaction. Ripple, voltage magnitude changes, and injected harmonics due to conversion switches are power quality issues for grid-integrated doubly fed induction generators (DFIG) wind sources. In this study, FACTS (flexible alternating current transmission system) devices like the static VAR compensator (SVC), thyristor controlled series compensator (TCSC), unified power flow controllers (UPFC), and static synchronous compensators (STATCOM) are used to stabilise wind energy with DFIGs. The simulation test cases using MATLAB also analyse three lines to ground fault (LLL-G) of fault measures, which showed a 9 MW that transferred to utility grid. Therefore, it is suggested to inject or absorb reactive power to stabilise the system using moth flame optimization with firebug swarm optimization (MFO-FSO). The simulation results clearly demonstrate that the proposed MFOFSO based STATCOM devices outperform the current nonlinear generalized predictive control based STATCOM, which only achieves 0.9815 per unit voltage stability, by achieving a higher voltage profile of 0.9925 per unit voltage stability with a reactive power injection of 1.82 MVAR.

Reliability Improvement of Composite Power System using UPFC

Together with quality power supply criteria, Composite Power System (CPS) reliability is also one of the important aspects of deciding the security of the CPS for a given load demand. In the current paper, the reliability of CPS is evaluated. The Newton Raphson (NR) approach is implemented in Power System Simulation for Engineering (PSSE) software to take into account, the load flows, then the power available to the load points, to evaluate the reliability of CPS. Newton Raphson NR Method was implemented by considering different contingencies of the CPS. Power available to the load points obtained by the NR method is critical in identifying the successful operating state of the CPS. Expected Load Curtailment (ELC), Number of Load Curtailment (NLC), Expected Energy Not Supplied (EENS), and Severity Index (SI) are the crucial dependability indices that are assessed. The main objective of the Reliability evaluation of the CPS is to investigate the scope for the improvement of reliability and explore the possible schemes to improve CPS reliability. The Unified Power Flow Controller (UPFC) one of the Flexible AC Transmission Systems is incorporated into the CPS to analyze the improvement in the reliability of the system. Further, the effect of UPFC on the power-carrying capacity of the lines under contingency conditions, resulting in the failure mode of CPS operation is examined. Improvement in the reliability indices of the system is observed due to UPFC incorporation.

Enhancing power system security using soft computing and machine learning

Purpose. To guarantee proper operation of the system, the suggested method infers the loss of a single transmission line in order to calculate a contingency rating. Methods. The proposed mathematical model with the machine learning with particle swarm optimization algorithm has been used to observe the stability analysis with and without the unified power flow controller and interline power flow controller, as well as the associated costs. This allows for rapid prediction of the most affected transmission line and the location for compensation. Results. Many contingency conditions, such as the failure of a single transmission line and change in the load, are built into the power system. The single transmission line outage and load fluctuation used to determine the contingency ranking are the primary emphasis of this work. Practical value. In order to set up a safe transmission power system, the suggested stability analysis has been quite helpful.

An accurate power control strategy for electromagnetic rotary power controllers

AbstractWith the rapid development of active distribution networks, the “petal”‐type distribution network has become the mainstream power supply structure. Power control methods for active distribution networks should be further studied to ensure the safe and reliable power supply of a distribution system. An electromagnetic rotary power flow controller (RPFC) is a feasible solution for controlling power in active distribution networks. However, when testing the effectiveness of the PQ decoupled control method for RPFC based on instantaneous reactive power theory, difficulties were encountered with the synchronous control of the rotor position angle of two rotating‐phase transformers, and the accuracy of power control was unsatisfactory. Given this condition, PQ control is improved in three ways. First, the system's periodic oscillation problem is solved via variable speed control. Second, the servo motor‐rotary phase‐shifting transformer synchronous rotation scheme, which reduces power control error and improves stability, is designed. Third, the overshoot phenomenon in power control is improved using the variable‐domain fuzzy proportional‐integral adaptive method. Experimental results show that the proposed advanced control scheme exhibits good dynamic and static performance in power control scenarios and achieves effective improvement in RPFC.

Power quality enhancement of solar–wind grid connected system employing genetic-based ANFIS controller

Abstract The demand for electricity globally has led to the search for renewable energy resources for power generation and attaining it in an eco-friendly manner. The solar photovoltaic systems and wind-based generators of power are regarded as primary resources of renewable energy and are called Distributed Generation units as they are scattered in nature. These are operated with bidirectional converters by providing auxiliary services at grid side and load side in either mode of microgrid operation. Besides, the DC power generation units’ integration gets converted into AC system by means of inverters. These types of systems not only increase voltage and current harmonics and power frequency deviations but also drive the distribution system to risky operating zone. This emphasizes the stipulation of advanced control schemes for microgrid architecture. Consequently, power electronic converters introduce harmonics in the system and affect system performance. To report these expanded issues, the authors recognized an advanced custom power device entitled Distributed Power Flow Controller (DPFC). In this study, the proposed system on solar–wind-based hybrid energy approach has been examined primarily through the strategy of DPFC mechanism. Later, the system has been examined with Genetic Algorithm (GA)-based fuzzy logic controller and GA-based adaptive neuro fuzzy inference system controller for shunt control of context built with DPFC mechanism. Furthermore, the validated results are verified using MATLAB/Simulink software.

DER integrated BTB-VSI based DSTATCOM for PQ enhancement

ABSTRACT This article demonstrates the performance of back-to-back connected voltage source inverter (BTB-VSI)-based distribution static compensator (DSTATCOM). In the proposed system, a three-phase three wire electrical utility system (EUS) is integrated with distributed energy resources (DER) through BTB-VSI. It has drawn more attention due to enhanced active power filtering, simple design procedure and performs reliable operation. The objectives of the research work is to provide clean power for weak EUS with improved power quality (PQ) such as, better voltage regulation, improved power factor (P.F), reduced total harmonic distortion (THD), balanced voltage at point of common coupling (PCC) and better optimal active power flow control (OAPFC), and so on. An artificial neurocontrol technique Kernel Hebbian Least Mean Square (KHLMS) is chosen to determine the accurate reference source current for operation of voltage source inverter (VSI). The BTB-VSI performance is investigated on both shunt compensation and OAPFC. The proposed system is converted to a simulation model and hardware unit using MATLAB/Simulink software and SPARTAN−6 field programmable gate arrays (FPGA) controller. Finally, the Simulation and experimental results illustrate that the shunt compensating ability with OAPFC of BTB-VSI performs better over VSI as per IEEE Std 1159–2019 grid code.

An intelligent fault detection and classification technique based on variational mode decomposition-CNN for transmission lines installed with UPFC and wind farm

The output voltage and current signals of grid-connected doubly-fed induction generator (DFIG)-based wind turbine generators (WTGs) are significantly modulated during grid disturbances. Consequently, the performance of conventionally used distance relaying-based transmission line (TL) protection schemes are affected. The problem becomes further complicated when the interconnected TLs are compensated with unified power flow controller (UPFC). In this paper, an intelligent relaying scheme is proposed for efficient detection and classification of faults in such crucial TLs. In the proposed method, the suitable features are extracted from the locally measured current signals using variational mode decomposition (VMD). The main advantage of VMD is that it can extract the different frequency components of a faulted current signal adaptively with fast convergence. The extracted gray-scale images through VMD are utilized further by the deep convolution neural network (CNN) classifier for effective classification of faults. The efficacy of the proposed relaying algorithm is evaluated on 12000 fault and 120 non-fault cases generated on a system comprising of DFIG-wind farm and UPFC compensation using MATLAB/Simulink® and real time digital simulation platform (OP4510). The fast fault detection time (¡10 ms), high accuracies in the fault detection and classification (100% and 99.86%) justify the merits of the proposed relaying scheme.

Design and simulation of monarch butterfly optimized SP-UPFC for power quality compensation

The super smart gridsare a kind of broad-area transmission network, which makes use of Flexible AC transmission system (FACTS)and helps to reduce greenhouse gas emissions while also maintaining the electricity infrastructure of various nations. The six-phase unified power flow controller (SP-UPFC) is a FACTS device that offers total stability to power system networks in the form of series and shunt compensations. The power quality compensation (PQC) operation using SP-UPFC is achieved by adopting the monarch butterfly optimization (MBO) algorithm. Here, shunt converters and series converters of parallel and series connection units are kept in sync with the help of master-slave synchronization. In addition, a coordination strategy is created for the SP-UPFC control protection system and the power grid protection, which improves the ride-through capability during a failure. In comparison to state-of-the-art methods, the simulation results reveal that the proposed MBO-optimizedSP-UPFC decreases total harmonic distortion (THD) and increases power factor.

Optimized Power Flow Control to Minimize Congestion in a Modern Power System

The growing integration of renewable energy sources (RES) into the power system causes congestion to occur more frequently. In order to reduce congestion in the short term and to make the utilization of the power system more efficient in the long term, power flow control (PFC) in the transmission system has been proposed. However, exemplary studies show that congestion will increase also in the distribution system if the transmission system is expanded. For this reason, the potential of PFC to reduce congestion in a model of a real 110 kV distribution system is investigated. Several Unified Power Flow Controller (UPFC) devices are optimized in terms of their number and placement in the power system, their size, control parameters, and costs, by using a Parallel Tempering approach as well as a greedy algorithm. Two optimization variants are considered, one reducing the number of degrees of freedom by integrating system knowledge while the other does not. It is found that near a critical grid state and disregarding costs, PFC can reduce congestion significantly (99.13%). When costs of the UPFCs are taken into account, PFC can reduce congestion by 73.2%. A basic economic analysis of the costs reveals that the usage of UPFCs is profitable. Furthermore, it is found that the reduction in the solution space of the optimization problem leads to better results faster and that, contrary to expectations, the optimization problem is simple to solve. The developed methods allow not only for the determination of the optimal use of UPFCs to minimize congestion, but also to estimate their profitability.