Design of an Adaptive Neurofuzzy Inference Control System for the Unified Power-Flow Controller

This paper presents a new approach to control the operation of the unified power-flow controller (UPFC) based on the adaptive neurofuzzy inference controller (ANFIC) concept. The training data for the controller are extracted from an analytical model of the transmission system incorporating a UPFC. The operating points' space is dynamically partitioned into two regions: 1) an inner region where the desired operating point can be achieved without violating any of the UPFC constraints and 2) an outer region where it is necessary to operate the UPFC beyond its limits. The controller is designed to achieve the most appropriate operating point based on the real power priority. In this study, the authors investigated and analyzed the effect of the system short-circuit level on the UPFC operating feasible region which defines the limitation of its parameters. In order to illustrate the effectiveness of the control algorithm, simulation and experimental studies have been conducted using the MATLAB/SIMULINK and dSPACE DS1103 data-acquisition board. The obtained results show a clear agreement between simulation and experimental results which verify the effective performance of the ANFIC controller

Fuzzy second order sliding mode control of a unified power flow controller

Purpose. This paper presents an advanced control scheme based on fuzzy logic and second order sliding mode of a unified power flow controller. This controller offers advantages in terms of static and dynamic operation of the power system such as the control law is synthesized using three types of controllers: proportional integral, and sliding mode controller and Fuzzy logic second order sliding mode controller. Their respective performances are compared in terms of reference tracking, sensitivity to perturbations and robustness. We have to study the problem of controlling power in electric system by UPFC. The simulation results show the effectiveness of the proposed method especiallyin chattering-free behavior, response to sudden load variations and robustness. All the simulations for the above work have been carried out using MATLAB / Simulink. Various simulations have given very satisfactory results and we have successfully improved the real and reactive power flows on a transmission lineas well as to regulate voltage at the bus where it is connected, the studies and illustrate the effectiveness and capability of UPFC in improving power.В настоящей статье представлена усовершенствованная схема управления, основанная на нечеткой логике и режиме скольжения второго порядка унифицированного контроллера потока мощности. Данный контроллер обладает преимуществами с точки зрения статической и динамической работы энергосистемы, например, закон управления синтезируется с использованием трех типов контроллеров: пропорционально-интегрального, контроллера скользящего режима и контроллера скользящего режима нечеткой логики второго порядка. Их соответствующие характеристики сравниваются с точки зрения отслеживания эталонов, чувствительности к возмущениям и надежности. Необходимо изучить проблему управления мощностью в энергосистеме с помощью унифицированного контроллера потока мощности (UPFC). Результаты моделирования показывают эффективность предложенного метода, особенно в отношении отсутствия вибрации, реакции на внезапные изменения нагрузки и устойчивости. Все расчеты для вышеуказанной работы были выполнены с использованием MATLAB/Simulink. Различные расчетные исследования дали весьма удовлетворительные результаты, и мы успешно улучшили потоки реальной и реактивной мощности на линии электропередачи, а также регулирование напряжения на шине, к которой она подключена, что позволяет изучить и проиллюстрировать эффективность и возможности UPFC для увеличения мощности

Modelling and control of united power flow controller for reinforcement of transmission systems

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The work involved in the thesis is concentrated on modelling and control of UPFC. The overall objective is to provide effective methods and tools for assessing the impact of UPFC in the reinforcement of transmission systems. The thesis clarifies modelling and control of UPFC into several subproblems, in which the associated models, algorithms and control strategies of UPFC have been systematically reviewed. An electromagnetic transient prototype model of the UPFC has been set up by using its detailed power electronic device as well as its internal closed-loop controller. The problems encountered in the process of building such a model and the way of handling them by EMTP have been discussed. This EMTP-based simulator of SPWM UPFC implemented has provided a useful tool to assist the development and validation of more detailed and practical model of the UPFC for further studies. The steady-state modelling and control for the UPFC has been developed, including: (i) The power injection model of the UPFC suitable for its implementation in an optimal multiplier power flow computation method has been derived in rectangular form. The effectiveness of the proposed algorithm has been compared with the user defined model method. (ii) A systematic method for deriving the control capabilities of the UPFC has been proposed based on predicting the feasibility limit of the system. Using an index derived from optimal multiplier, three dimensional diagrams describing the ranges have been obtained. The results are also verified through the singular value decomposition algorithm. (iii) A power injection model based control method (PIM) has been proposed and implemented to directly derive the UPFC parameters as so to achieve the control objectives. The assumptions, algorithmic process and validation of the PIM have been investigated in detail. Its pros and cons are also discussed. (iv) Five internal limits of the UPFC device have been derived as the constraints to its performance. A complete set of control rules considering these limits as well as their implementation in the PlM have been constructed to form the basis of optimal UPFC control strategies for its steady-state local control. All the above proposed methods are tested and validated on the IEEE 30-bus system, a practical 306-bus system and a meshed network. The thesis concludes by suggesting the future research areas in further UPFC studies

Application of Unified Power Flow Controller to Improve the Performance of Wind Energy Conversion System

This research introduces the unified power flow controller (UPFC) as a means to improve the overall performance of wind energy conversion system (WECS) through the development of an appropriate control algorithm. Also, application of the proposed UPFC control algorithm has been extended in this research to overcome some problems associated with the internal faults associated with WECS- voltage source converter (VSC), such as miss-fire, fire-through and dc-link faults

Enhancing the Performance of Power System under Abnormal Conditions Using Three Different FACTS Devices

In this paper, a comparison between Flexible Alternating Current Transmission System (FACTS) devices including Static Synchronous Compensator (STATCOM), Static Synchronous Series Compensator (SSSC) and Unified Power Flow Controller (UPFC) for providing a better adaptation to changing operating conditions and improving the usage of current systems. The power system using FACTS devices is presented under different conditions such as single phase fault and three phase fault. A digital simulation using Matlab/Simulink software package is carried out to demonstrate the better performance including the voltage and the current of the presented system using FACTS that located between buses B1 and B2 under different faults types. The results obtained investigate that the presented system gives better response with FACTS as compared to not using them under abnormal conditions besides, the UPFC gives better performance of power system under several faults as compared to STATCOM or SSSC as It can absorb reactive power in a manner which significantly reduced the fault current. It is demonstrated that UPFC can reduce the peak fault current at bus B1 ‎to 63.85% of its value without ‎using FACTS devices under line to ground fault and 79.18% under three line to ‎ground fault whereas STATCOM and SSSC reduce it ‎to (75.21, 94.35%) and (75.40, 94.68%), respectively

Comparison of Transient Stability Response for MMPS using UPFC with PI and Fuzzy Logic Controller

The increasing pressure on the power system increases the complexity that is becoming a concern for the stability of the power system and mainly for transitory stability. To operate the system in the event of faults, Flexible AC Transmission System (FACTS) devices are used that provide opportunities to control power and vibrations damping. This paper deals with the two control strategies of the Unified Power Flow Controller (UPFC) to damping the system oscillations stability. The stability of the Multi-Machine Power System (MMPS) was analysed with the presence of UPFC. The first strategy is the traditional PI controller (PI-C) with UPFC, and the second strategy is the proposed Fuzzy Logic controller (FL-C) proposed for UPFC device along with PI controller. The MATLAB R2014a was used in all simulations. Based on the results,  FL-C   for  UPFC device along with the PI controller has proven its superiority by has enhanced response to the system, thus minimized in the transitions overshoot and undershoot, and has lower ripple compared to traditional PI-C, both with and without UPFC

APPLICATION OF FACTS DEVICES IN POWER SYSTEMS

A reliable, stable and economically feasible electric power demand has been increasing rapidly in recent years. The complex interconnected power systems experience stability problems which lead to the overall system interruptions. FACTS (Flexible AC Transmission System) devices are being used to overcome power transmission problems such as power loss, over-loading, instability. This paper discusses the modeling and application of using FACTS (Flexible AC Transmission System) devices in power industry. The previous works ofHingorani, Gyugyi et al on FACTS in power transmission were studied and analyzed. The theory of power line transmission was studied. Two types ofF ACTS devices exist in power transmission; conventional thyristor based and fully controlled semiconductor based FACTS devices. The paper studies common devices like TCR, SVC, TCSC, VSC, STATCOM, SSSC and UPFC. Simple circuit diagrams and basic mathematical analysis of these devices are presented briefly. As a result the Matlab simulation of STATCOM, SVC and SSSC was run for further analysis of FACTS devices. Detailed analysis and comments on three FACTS devices that were simulated were given in the report

Stability improvement of power system using UPFC

Occurrence of a fault in a power system causes transients. To stabilize the system, Power System Stabilizer (PSS) and Automatic Voltage Regulator (AVR) are used. Load flow analysis is done to analyze the transients introduced in the system due to the occurrence of faults. The Flexible Alternating Current Transmission (FACTS) devices such as UPFC are becoming important in suppressing power system oscillations and improving system damping. The UPFC is a solid-state device, which can be used to control the active and reactive power. This thesis considers a typical three- machine nine-bus system as a case study for investigating the performance of UPFC is achieving stability. By using a UPFC the oscillation introduced by the faults, the rotor angle and speed deviations can be damped out quickly than a system without a UPFC. The effectiveness of UPFC in suppressing power system oscillation is investigated by analyzing their oscillation in rotor angle and change in speed occurred in the three machine system considered in this work. A proportional integral (PI) controller has been employed for the UPFC. It is also shown that a UPFC can control independently the real and reactive power flow in a transmission line. A MATLAB simulation has been carried out to demonstrate the performance of the UPFC in achieving transient stability of the three-machine nine-bus system

Load Flow Analysis with UPFC under Unsymmetrical Fault Condition

This paper addresses the comparative load flow analysis with and without Unified Power Flow Controller (UPFC) for six buses, three phase transmission line under unsymmetrical faults (L-G, L-L and L-L-G) in simulation model. Unified Power Flow Controller (UPFC) is a typical Flexible AC Transmission System (FACTS) device playing a vital role as a stability aid for large transient disturbances in an interconnected power system. The main objective of this paper is to improve transient stability of the six bus system. Here active and reactive power on load bus of the system considered has been determined under different fault conditions. UPFC has been connected to the system and its effects on power flow and voltage profile of test system has been determined with various line data and bus data for six buses, three lines power system and simulation model by using simulation toolbox has been developed. In this work a versatile model is presented for UPFC inherent order to improve the transient stability and damp oscillation. Index Terms – Unified Power Flow Controller (UPFC), Control, simulation, transients, line to ground fault (L-G), double line to ground fault (L-L-G), double line fault (L-L