Performance Of Unified Power Flow Controller Research Articles

Loss reduction of transmission lines using PSO-based optimum performance of UPFC

Transmission line losses are one of the essential topics and issues in power systems research. Several methods and techniques have been used to reduce these losses, and one of these modern techniques is flexible alternating current transmission systems (FACTS). In this paper, one of the most important types of this technology, the unified power flow controller (UPFC), was used to reduce losses in the Iraqi national grid (ING) 400 kV. This paper presents an efficient method for minimizing losses of transmission lines in the ING system (400 kV) 46-bus approach. A particle swarm optimization (PSO)-based optimum proportional-integral (PI) controller with UPFC was proposed to obtain the optimal location of UPFC and optimum parameters of the PI controller to achieve the objective function of the research. MATLAB coded the algorithm. The Newton-Raphson method was employed to perform load flow analysis. The results showed that the best place for UPFC is buses (14-17) named BGE4 (Baghdad)-AMN4 (Baghdad), and the total active power and reactive power losses decreased from 727.4593 to 579.3874 MW and from 5155.9 to 3971.1 MVAR, respectively and also led to voltage regulation.

Optimal allocation of UPFC based on healthy and stressed zones for critical power systems

A unified power flow controller (UPFC) is a versatile compensator providing multi-variable control for the critical power systems (CPS). In an attempt to reduce the search space for optimal allocation of UPFC thereby standardizing the deliberation over UPFC placement, zone-wise segregation of the network into weak and healthy zones is logically executed by an advanced network power stability indicator (NPSI). The UPFC performance is ascertained by a new line flow margin index (LFMI), power loss index and its economic benefit. The latter is derived by the cash outflow reduction (COR) and the internal rate of return (IRR), calculated by practical aspects like installation and maintenance cost, considering inflation and interest on amortization. For optimization, an improved version of the wind-driven optimization algorithm is proposed with finite-mass air parcels and intra-particle forces. An improved normalization technique is adopted for the multi-ranged, multi-objective problem. To simulate the CPS, the 57-bus test system with enhanced arbitrary load is considered. A significant reduction in power losses is observed when optimizing in reduced search space and the optimal location of G-UPFC is found to be in bus 13–15, which is also a part of the weaker zone. Several other results confirmatively approve the proposed approach of isolating the most appropriate zone for UPFC allocation based on the healthy and weak regions along with the proposed techno-economical evaluators.

Design Coordination of a Fuzzy-based Unified Power Flow Controller with Hybrid Energy Storage for Enriching Power System Dynamics

In power networks, operation planning has become necessary due to the continuously increased load demand. The Unified Power Flow Controller (UPFC) controls the power flow through the network and improves the dynamics of the power system. In this paper, the design application of the coordination of a fuzzy-based UPFC with hybrid energy storage has been proposed to enrich the system's dynamic performance during abnormal conditions and improve the hybrid energy storage performance during transients when the DC link voltage is insufficient to meet the converter voltage demand. The hybrid energy storage consists of a supercapacitor and a battery connected across the UPFC Vdc shunt capacitor. The proposed system to improve the UPFC performance during large disturbances on a multi-machine system was designed and tested in MATLAB/SIMULINK.

Evaluation of insulated gate bipolar transistor valve converter based unified power flow controller reliability and efficiency

The effectiveness and reliability of the unified power flow controller (UPFC) are determined by the insulated gate bipolar transistor (IGBT) valve. Thermal losses, conduction losses, and switching losses in the IGBT valve all affect the efficiency of UPFC. The failure rate of the converter valves is influenced by junction temperature, which has an impact on the converter's reliability. Piecewise linear electrical circuit simulation (PLECS) was used to simulate two IGBT valve-based converter legs working at 12000 Hz, part number GT30F123. By reference to the switching characteristics produced by PLECS, switching losses, conduction losses, and thermal losses are analyzed. Simulation results are corroborated with analytical measurements. The chance of achieving 100%, 50%, and 0% functioning modes are among the reliability indices that are analyzed. The chance of achieving a hundred percent, fifty percent, or zero percent functioning mode is assessed. The frequency of achieving the state probability and mean time to failures (MTTF) are obtained from probabilities using the Markov model. The thermal losses, failure rate, and lifetime of the UPFC are all quantified to give a complete picture of the UPFC's performance.

Fuzzy Sliding Mode based PI Controlled UPFC for Optimized WECS Dynamics during Fault Ride Through

With the enormous global growth in electrical power demand and the associated decrease in conventional power resources, electricity generation from renewable energy sources have been furiously sought worldwide, as they represent infinite and clean natural resources. Wind energy is one of the most efficient renewable energy sources. However, due to the fluctuating behaviour of wind energy and the need of electronic devices to link wind turbine generator with existing electricity grids, problems such as frequency oscillations, voltage instability and harmonic distortion may arise. Flexible alternative current transmission system (FACTS) devices, such as unified power flow controller (UPFC), can provide technical solutions to improve the overall performance of wind energy conversion systems (WECS). This paper presents a comparative study of transient stability and reactive power compensation issues in an autonomous wind energy conversion system (WECS) using robust fuzzy-sliding mode based unified power flow controller (UPFC). It is noted from the simulation results that the performance of UPFC is superior to static VAR compensator and static synchronous compensator in improving the voltage profile of the WECS. Further, fuzzy and fuzzy-sliding mode based UPFC controller is designed in order to improve the transient performance. Simulation results reflect the robustness of the proposed fuzzy-sliding mode controller for better reactive power management to improve the voltage stability in comparison with the conventional PI and fuzzy-PI controllers. In addition to this, system stability analysis is performed based on Eigen value, bode and Popov for supporting the robustness of the proposed controller.

Application of Differential Evolution Algorithm for Optimal Placement of UPFC for Improved Voltage Stability

The Unified Power Flow Controller (UPFC) is one of the versatile and most effective Flexible AC transmission System (FACTS) devices which can provide full dynamic control of a transmission line parameters, bus voltage, line impedance and phase angle for improved system security. However, the extent that performance of UPFC can be brought out; it’s greatly dependents upon the location of the device in the system. The present work is a Differential Evolution (DE) based algorithm for optimal placement of the UPFC device under steady state (normal, moderate and critical) conditions and is aimed at voltage profile enhancement of an interconnected power system. The proposed method is applied on an IEEE 14-bus power system which is demonstrated through MATPOWER simulation tool. The results obtained indicate that DE is robust based on the facts that the voltage profile was kept within the acceptable limit. Installing UPFC in the optimal location determined by DE can significantly enhance the security of power system through improvement of bus voltage limit violations.

Robust fuzzy‐sliding mode based UPFC controller for transient stability analysis in autonomous wind‐diesel‐PV hybrid system

This study presents a comparative study of transient stability and reactive power compensation issues in an autonomous wind–diesel-photovoltaic based hybrid system (HS) using robust fuzzy-sliding mode based unified power flow controller (UPFC). A linearised small-signal model of the different elements of the HS is considered for the transient stability analysis in the HS under varying loading conditions. An IEEE type 1 excitation system is considered for the synchronous generator in the HS, with negligible saturation characteristic, for detailed voltage stability analysis. It is noted from the simulation results that the performance of UPFC is superior to static VAR compensator and static synchronous compensator in improving the voltage profile of the HS. Further, fuzzy and fuzzy-sliding mode based UPFC controller is designed in order to improve the transient performance. Simulation results reflect the robustness of the proposed fuzzy-sliding mode controller for better reactive power management to improve the voltage stability in comparison with the conventional PI and fuzzy-PI controllers. In addition to this, system stability analysis is performed based on eigenvalue, bode and popov for supporting the robustness of the proposed controller.

Performance and Analysis of Reactive Power Compensation by Unified Power Flow Controller

The Unified Power Flow Controller (UPFC) is the most versatile of the FACTS controllers envisaged so far. The main function of the UPFC is to control the flow of real and reactive power by injection of a voltage in series with the transmission line. Both the magnitude and the phase angle of the voltage can be varied independently. Real and Reactive power flow control can allow for power flow in prescribed routes, loading of transmission lines close to their thermal limits and can be utilized for improving transient and small signal stability of the power system. In this paper UPFC is incorporated in a SMIB (Single Machine Infinite Bus) system and the response of SMIB system has been recorded with and without UPFC, thereafter the comparison of both the output has been done. When no UPFC is installed, real and reactive power through the transmission line cannot be controlled. This paper presents control and performance of UPFC intended for installation on that transmission line to control power flow. Installing the UPFC makes it possible to control amount of active power flowing through the line. Simulations are carried out using MATLAB software to validate the performance of the UPFC.

DYNAMIC STABILITY IMPROVEMENT AND REAL POWER LOSSES REDUCTION OF A MULTI MACHINE POWER SYSTEM USING UNIFIED POWER FLOW CONTROLLER

This paper focuses on three key issues of the power system that is stability enhancement, minimization of real power losses, and improving voltage profile of the buses by placing the Unified Power Flow Controller (UPFC) to the best location in WSCC 3 machine 9 bus system. The comparison between with and without UPFC is carried out to prove that UPFC enhances the stability of the multi machine power system. In this paper the best location of the UPFC is recognized by Power Flow Analysis. Eigen Value Analysis and Continuation Power Flow (CPF) is employed to show the performance of UPFC for stability enhancement. The analysis is carried out using Power System Analysis Toolbox (PSAT) software.

Investigation and Comparison of the Effect of Facts Devices, Capacitors and Lines Reactance Variations on Voltage Stability Improvement and Loadability Enhancement in Two Area Power System

This paper studies the important power system phenomenon and voltage stability by using continuation power flow method. Voltage collapse scenario is presented which can be a serious result of voltage instability and also the parameters that affected by voltage collapse are discussed. In analyzing power system voltage stability, continuation power flow method is utilized which consists of successive load flows. In this paper steady-state modeling of Static VAR Compensator (SVC) and Unified Power Flow Controller (UPFC) and effect of compensator and variation of line reactance on the voltage stability have been studied and Comparison between performance of UPFC and SVC and installation shunt capacitor and variation of line reactance for improve voltage stability has been done.Case studies are carried on 11 bus network in two areas. Simulation is done with PSAT in MATLAB. Continuation Power Flow was implemented using Newton Raphson method. Simulation results show the proper performance of UPFC, SVC, installation shunt capacitor and variation of line reactance to improve voltage control and significantly increase the loadability margin of power systems. Full Text: PDF

Investigation of UPFC performance under system uncertainties

This paper presents a systematic robustness analysis of unified power flow controller (UPFC) under system parametric uncertainties. The power system uncertainties are considered as different loading conditions. In order to deal with these uncertainties, robust control methods are handled to design UPFC controllers. The well known robust methods such as quantitative feedback theory (QFT) and mu-synthesis are carried out to design UPFC controller. Two test cases as single machine and multi machine are incorporated to evaluate the proposed methods. Also, the proposed methods are compared with conventional controller. The simulation results denote the ability and effectiveness of the proposed methods for tackle with uncertainties.

Real and Reactive Power Control by using 48-pulse Series Connected Three-level NPC Converter for UPFC

The equipments based on the power electronics have been improved under the name of Flexible Alternating Current Transmission Systems (FACTS) in the last years. Unified Power Flow Controller (UPFC) is the most widely used FACTS device to control the power flow and to optimize the system stability in the transmission line. UPFC is a FACTS devices that can control active and reactive power flow in transmission line by means of injection controllable series voltage to the transmission line. This paper proposes a new connection for a Unified Power Flow Controller (UPFC) to control the active and reactive power flow control in two sides of a transmission line independently and it regulates bus voltage in the same transmission line, furthermore it is possible to balance line current too. This connection of the UPFC will be called an center node UPFC (C_UPFC). It is one of the newest devices within the FACTS technology. The structure and capability of the C_UPFC is discussed and its control scheme is based on the d-q orthogonal coordinates. According to this, the performance of UPFC for several modes of operations using different control mechanisms based on Proportional-Integral (PI) and PID based controllers has been studied. The obtained simulation results from Matlab/simulink confirm the effective features.

Comparison of FACTS Devices for Power System Stability Enhancement

development of the modern power system has led to an increasing complexity in the study of power systems, and also presents new challenges to power system stability, and in particular, to the aspects of transient stability and small-signal stability. Transient stability control plays a significant role in ensuring the stable operation of power systems in the event of large disturbances and faults, and is thus a significant area of research. This paper investigates the improvement of transient stability of a two-area power system, using UPFC (Unified Power Flow Controller) which is an effective FACTS (Flexible AC Transmission System) device capable of controlling the active and reactive power flows in a transmission line by controlling appropriately its series and shunt parameters. Simulations are carried out in Matlab/Simulink environment for the two-area power system model with UPFC to analyze the effects of UPFC on transient stability performance of the system. The performance of UPFC is compared with other FACTS devices such as Static Synchronous Series Compensator (SSSC), Thyristor Controlled Series Capacitor (TCSC), and Static Var Compensator (SVC) respectively. The simulation results demonstrate the effectiveness and robustness of the proposed UPFC on transient stability improvement of the system.

UPFC for Enhancing Power System Reliability

This paper discusses various aspects of unified power flow controller (UPFC) control modes and settings and evaluates their impacts on the power system reliability. UPFC is the most versatile flexible ac transmission system device ever applied to improve the power system operation and delivery. It can control various power system parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the power system reliability has not been addressed sufficiently yet. A power injection model is used to represent UPFC and a comprehensive method is proposed to select the optimal UPFC control mode and settings. The proposed method applies the results of a contingency screening study to estimate the remedial action cost (RAC) associated with control modes and settings and finds the optimal control for improving the system reliability by solving a mixed-integer nonlinear optimization problem. The proposed method is applied to a test system in this paper and the UPFC performance is analyzed in detail.

Application and comparison of computational intelligence techniques for optimal location and parameter setting of UPFC

Unified power flow controller (UPFC) is one of the most effective flexible AC transmission systems (FACTS) devices for enhancing power system security. However, to what extent the performance of UPFC can be brought out, it highly depends upon the location and parameter setting of this device in the system. This paper presents a new approach based on computational intelligence (CI) techniques to find out the optimal placement and parameter setting of UPFC for enhancing power system security under single line contingencies ( N−1 contingency). Firstly, a contingency analysis and ranking process to determine the most severe line outage contingencies, considering lines overload and bus voltage limit violations as a performance index, is performed. Secondly, a relatively new evolutionary optimization technique, namely: differential evolution (DE) technique is applied to find out the optimal location and parameter setting of UPFC under the determined contingency scenarios. To verify our proposed approach and for comparison purposes, simulations are performed on an IEEE 14-bus and an IEEE 30-bus power systems. The results, we have obtained, indicate that DE is an easy to use, fast, robust and powerful optimization technique compared with genetic algorithm (GA) and particle swarm optimization (PSO). Installing UPFC in the optimal location determined by DE can significantly enhance the security of power system by eliminating or minimizing the number of overloaded lines and the bus voltage limit violations.

Adaptive particle swarm optimisation of unified power flow controller for synchronous generator stabilisation

The real and reactive power flow in a transmission line can be instantaneously controlled by a pair of back-to-back power electronic converters, called a Unified Power Flow Controller (UPFC). This paper presents a novel optimal PI controller for UPFC to enhance the dynamic performance of UPFC as well as for synchronous generator stabilisation. The optimal PI controller based on Particle Swarm Optimisation (PSO) is obtained for a wide range of operating conditions of the system as well as for a variety of disturbances. The operating constraints of the UPFC are considerably practical constraints during the operation of the UPFC in a real power system. The control strategy is based on dq-axis theory. Comprehensive computer simulations are carried out to verify the proposed control scheme.

Performance Analysis of Fuzzy Logic Based Unified Power Flow Controller

FACTS devices are used to control the power flow, to increase the transmission capacity and to optimize the stability of the power system. One of the most widely used FACTS devices is Unified Power Flow Controller (UPFC). The controller used in the control mechanism has a significantly effects on controlling of the power flow and enhancing the system stability of UPFC. According to this, the capability of UPFC is observed by using different control mechanisms based on P, PI, PID and fuzzy logic controllers (FLC) in this study. FLC was developed by taking consideration of TakagiSugeno inference system in the decision process and Sugeno’s weighted average method in the defuzzification process. Case studies with different operating conditions are applied to prove the ability of UPFC on controlling the power flow and the effectiveness of controllers on the performance of UPFC. PSCAD/EMTDC program is used to create the FLC and to simulate UPFC model. Keywords—FACTS, Fuzzy Logic Controller, UPFC.

Electromagnetic transient simulation studies of sinusoidal PWM unified power-flow controllers

This paper is concerned with the digital studies of the sinusoidal pulse-width modulation (SPWM) unified power-flow controller (UPFC). At first the SPWM scheme generation and the main factors affecting the functions and the control of the UPFC are discussed. Secondly, how the series part and shunt part of the SPWM UPFC are controlled and coordinated is analyzed. The paper then places the emphasis on the detailed electromagnetic transient program (EMTP) simulation of SPWM UPFC. Simulation results of SPWM UPFC regulation performance and open-loop control are presented. The simulator is further used to investigate the operating envelope and closed-loop control. The digital EMTP-based simulator of SPWM UPFC implemented in this paper provides a useful tool for further research. The information presented gives a deep insight into UPFC performance.

AEP unified power flow controller performance

The installation of the world's first unified power flow controller (UPFC) has been completed and a series of commissioning tests were conducted at the Inez Substation of American Electric Power (AEP) in eastern Kentucky. The project is a collaborative effort between AEP, the Westinghouse Electric Corporation, and the Electric Power Research Institute (EPRI). Comprising two /spl plusmn/160 MVA voltage-sourced GTO-thyristor-based inverters, this installation is the first large-scale practical demonstration of the UPFC concept, and its completion is a significant milestone in the progress of power electronics technology for flexible AC transmission system (FACTS). This paper briefly reviews the main features of the Inez installation and discusses the operation of the equipment. A collection of measured performance characteristics is presented to illustrate the unique capabilities of the UPFC. These dynamic measurements were made in the course of commissioning, and they graphically illustrate the ability of the UPFC to independently control the real and reactive power on a transmission line, while also regulating the local bus voltage. The results include a demonstration of the series inverter at Inez, operating in stand-alone mode. This test constitutes the first practical large-scale demonstration of the static synchronous series compensator (SSSC) concept.

Simulation of the unified power flow controller performance using PSCAD/EMTDC

This paper investigates the performance of a unified power flow controller (UPFC) constructed by a back to back connection of a hysteresis current forced (HCF) converter and a pulse width modulated (PWM) inverter. The UPFC has been modelled at the component level using PSCAD/EMTDC program and the simulation results of the UPFC applications in steady state power flow control and dynamic stability enhancement are demonstrated in a test system. The performance of the proposed switching schemes and associated controllers in providing the desired UPFC internal characteristics such as constant DC bus voltage and bi-directional power transfer capability is illustrated.