Unified Power Flow Controller System Research Articles

Evaluating the performance of reaching laws in the sliding mode control of the Unified Power Flow Controller (UPFC)

This paper evaluates reaching laws in sliding mode control (SMC), encompassing constant rate, exponential, and power rate reaching laws. The performance of the proposed controller is assessed using a Unified Power Flow Controller (UPFC) as the test subject. The Unified Power Flow Controller system is in order to improve the stability of a power system hence providing security under increased power flow conditions. The sliding mode control, utilizing reaching laws, is designed to ensure the Unified Power Flow Controller system closely follows the reference power. Comparative simulation results with a traditional PID controller demonstrate superior performance with sliding mode control. Specifically, the sliding mode control Reaching law with power rate effectively controls the Unified Power Flow Controller system for active power, Various simulations have given very satisfactory results and we have successfully improved the active and reactive power flows on a line of transmission. achieving an overshoot of approximately 0.5411%, with a setting time of 0.1009 seconds and a rising time of 4.0720*10^-4 seconds.

Improvement of the Power System's Transient Stability Using the Unified Power Flow Controller with Fuzzy Logic Technique

By combining the functions of many FACTS (flexible alternative current transmission systems) devices into a single unit, the UPFC (unified power flow controller) is the most efficient FACTS device available. Two voltage converters work together to form the Unified Power Flow Controller, a flexible tool for enhancing voltage regulation, power flow management, and power system stability. Both converters rely heavily on their control methods. This article discusses the power flow mechanism in a transmission line, which is necessary for understanding the functioning of UPFC in a transmission line and using a standard PI controller with voltage references in the control circuit of both converters. This study aims to enhance the power system's dependability and stability by developing a smart support-based UPFC device. Fuzzy logic is a useful tool for controlling UPFC equipment in a variety of failure scenarios. The fuzzy logic controller contrasts power grid characteristics such as a rotor speed deviation to a reference value to create operational pulses for the voltage source converter in the UPFC system. The suggested model will be tested using MATLAB simulation. The success of the proposed model is shown by thoroughly comparing simulation results to those of previously established models. This research paper's original contribution is the creation of a smart support-based UPFC device with fuzzy logic control. By comparing power system parameters such as rotor speed deviation to a reference value and generating operational pulses for the voltage source converter in the UPFC system, this technique increases the electricity grid's dependability and stability. The effectiveness of the suggested model is proved by a comparison of simulation results obtained in a MATLAB environment with those obtained from previously developed models.

A Comparative Study of the UPFC System by Simulation with PI-D and (NEWELM and NIMC) Controllers Based on the Adaptive Control for the Compensation of Power

-Flexible Alternating Current Transmission System devices (FACTS) are power electronic components. Their fast response offers potential benefits for power system stability enhancement and allows utilities to operate their transmission systems even closer to their physical limitations, more efficiently, with improved reliability, greater stability and security than traditional mechanical switching technology. The unified Power Flow Controller (UPFC) is the most comprehensive multivariable device among the FACTS controllers. According to high importance of power flow control in transmission lines, new controllers are designed based on the Elman Recurrent Neural Network (NEWELM) and Neural Inverse Model Control (NIMC) with adaptive control. The Main purpose of this paper is to design a controller which enables a power system to track reference signals precisely and to be robust in the presence of uncertainty of system parameters and disturbances. The performances of the proposed controllers (NEWELM and NIMC) are based neural adaptive control and simulated on a two bus test system and compared with a conventional PI controller with decoupling (PI-D). The studies are performed based on well known software package MATLAB/Simulink tool box.

Robust control of a UPFC system with H~ control technique

<p>FACTS (Flexible AC Transmission Systems) technology has now been accepted as a potential solution to the stability problem and load flow. The Unified Power Flow Controller (UPFC) is considered to be the most powerful and versatile among all FACTS devices. This paper presents the control of a UPFC system using Hinf robust control technique. A simulation study using Matlab/Simulink is presented to the performance of this control strategy and the robustness with respect to variations of the system parameters such as the inductance of the transmission line.</p>

Unified Power Flow Controller Based on Autotransformer Structure

This paper proposes a new unified power flow controller (UPFC) topology. A single phase of them system with the proposed topology consists of an N:2 transformer with a center tap at the low-voltage side and a power converter module comprising full- and half-bridge converters. A three-phase system can be implemented with three devices. While the conventional UPFC topology uses two three-phase transformers, which are called series and parallel transformers, the proposed topology utilizes three single-phase transformers to implement a three-phase UPFC system. By using an autotransformer structure, the power rating of the transformers and the voltage rating of switches in the power converter module can be significantly decreased. As a result, it is possible to reduce the installation spaces and costs compared with the conventional UPFC topology. In addition, by adopting a full- and half-bridge converter structure, the proposed topology can be easily implemented with conventional power devices and control techniques. The techniques used to control the proposed topology are described in this paper. The results obtained from simulations and experiments verify the effectiveness of the proposed UPFC topology.

Robust stability power in the transmission line with the use of a UPFC system and neural controllers based adaptive control

The main purpose of this paper is to design a regulator which enables a power system to track reference signals precisely and to be robust in the presence of uncertainty of system parameters and disturbances. The performances of the proposed controllers (NEWELM and NIMC) are based neural adaptive control and simulated on a two-bus test system and compared with a conventional PI controller with decoupling (PI-D). The studies are performed based on well known software package MATLAB/Simulink tool box. Flexible Alternating Current Transmission System devices (FACTS) are power electronic components. Their fast response offers potential benefits for power system stability enhancement and allows utilities to operate their transmission systems even closer to their physical limitations, more efficiently, with improved reliability, greater stability and security than traditional mechanical switching technology. The most used component of FACTS systems is the Unified Power Flow Controller (UPFC). According to high importance of power flow control in transmission lines, new controllers are designed based on the Elman Recurrent Neural Network (NEWELM) and Neural Inverse Model Control (NIMC) with adaptive control.

Fault Diagnosis Technology of Intelligent Substation UPFC System Based on Abnormal Sub-module Port Voltage

Unified power flow controller (UPFC) combines the advantages of FACTS devices of series and parallel, which is an important direction for the development of intelligent substations in the future. However, a large number of MMC submodules have become potential fault points of UPFC system. The rapid judgment of fault state and accurate positioning of fault sub-modules are the primary conditions to ensure the safe and stable operation of UPFC system, which can effectively reduce the mobile operation and maintenance time of power engineering operation and maintenance personnel, and guarantee the safety of operation and maintenance. Therefore, this paper proposes a fault diagnosis technology of intelligent substation UPFC system based on abnormal sub-module port voltage (SPVE). Experimental results show that the SPVE method has advantages in identification accuracy and rapidity.

Design of an Improved Nonlinear H∞ Control for UPFC to Enhance Transient Stability of Power System

An improved nonlinear (IN) H∞ control of unified power flow controller (UPFC) is investigated and designed in the power system by using the Hamiltonian function method. First, the dissipative Hamiltonian structure of the UPFC system is established by means of variable transformation. Then, based on the obtained dissipative Hamiltonian structure, an IN H∞ control is put forward. Simulation results on the two-area four-machine power system demonstrate the effectiveness and robustness of the IN H∞ control in comparison with that of feedback linearization control (FLC) and add-on self-tuning (ST) control. The research results show that the IN H∞ control has better performance than the two other controls.

Time delay finite time control of unified power flow controller for power flow reference tracking

This paper presents a time delay finite time controller (TDFTC) applied to a unified power flow controller (UPFC) to achieve rapid and finite time reference signal tracking of power flow in presence of plant uncertainties. The TDFTC is a nonlinear control based on the time delay disturbance estimator and the Lyapunov's stability theory to estimate the disturbances and cancel them. The TDFTC overcomes the drawback of traditional linear PI control, which is typically tuned for one specific operating condition, and reduces chattering by using lower design gains. In this paper, first a state space complete dynamic model of UPFC is established based on Kirchhoff's equations and Park's transformation and then TDFTC law is developed for the UPFC system. The proposed control is validated via a detailed simulation on a two bus system. Simulation results show power, effectiveness, robustness and accuracy of the proposed controller.

Fault Detection & Classification in UPFC Integrated Transmission Line Using DWT

Fault detection and classification in UPFC (Unified Power Flow Controller) integrated transmission line using single terminal based DWT (Discrete Wavelet Transform) is proposed. The current is extracted from the sending end bus and processed through wavelet transform to evaluate the spectral energy (SE) using db4 mother wavelet. Three level decomposition is framed to extract the fundamental frequency component from non-stationary signal, considering sampling frequency of 2kHz system. The fundamental frequency component of respective phase currents are used to compute SE at sending end. The SE of individual phase current is the key factor for deciding the fault pattern detection and classification. The advantage of using this it requires less cost and protect entire transmission line with minimal fault detection time. The various types of fault (L-G, L-L, L-L-G, L-L-L) are simulated by considering the parameter like fault resistance, source impedance, fault inception angle, multi-location fault, reverse power flow and UPFC system parameter. The scheme works reliable and efficient to detect and classify the fault within a cycle of sample period 40 or a cycle of time period 20ms compared to other conventional relaying scheme.

Electromagnetic characteristic analysis of the series transformer in UPFC system

The operation conditions of series transformer in Unified Power Flow Controller (UPFC) system are analyzed, and a shell-type structural scheme is proposed in this paper. Taking into account the nonlinear characteristic and the eddy current effect of the ferromagnetic materials, the effective complex permeability is adopted to calculate the nonlinear reluctance of the core, and an electromagnetic transient model of the series transformer is presented based on the duality theory of electric circuit and magnetic circuit, which is one key part of the comprehensive simulation model of UPFC. Besides, the improved magnetic circuit method is coupled with the electric circuit to analyze the special three-phase asymmetrical DC bias phenomenon of series transformer. Some experiments about no-load switching and asymmetrical DC bias on a low-voltage series transformer prototype have been done to verify the transient model and the improved magnetic circuit method, respectively. Finally, the reactive power of the no-load series transformer prototype under asymmetrical DC bias is calculated, the results indicate that the variation of the reactive power of series transformer under asymmetrical DC bias becomes more complicated, which increases the difficulty of voltage regulation in UPFC system.

Adaptive Control with SSNN of UPFC System for the Compensation of Active and Reactive Power

The focus of this study is the effectiveness of the controller's Unified Power Flow Controller UPFC with the choice of a control strategy. This Unified Power Flow Controller (UPFC) is used to control the power flow in the transmission systems by controlling the impedance, voltage magnitude and phase angle. This controller offers advantages in terms of static and dynamic operation of the power system. It also brings in new challenges in power electronics and power system design. To evaluate the performance and robustness of the system, we proposed a hybrid control combining the concept of identification neural networks with conventional regulators and with the changes in characteristics of the transmission line in order to improve the stability of the electrical power network. With its unique capability to control simultaneously real and reactive power flows on a transmission line as well as to regulate voltage at the bus where it is connected, this device creates a tremendous quality impact on power system stability. The result which has been obtained from using MATLAB and SIMULINK software showed a good agreement with the simulation result.

The Simulation Study and Dynamic Analysis of Unified Power Flow Controller for Industrial and Educational Purposes

Unified Power Flow Controller (UPFC) is versatile and one of the advanced FACTS devices. In this study, dynamic analysis of UPFC is realized by MATLAB-Simulink simulation. For this purpose, a simulation model is presented that enable to be analysed of effects of device to power system in detail. Simulation model is a based on shunt current injection and series voltage injection. UPFC system dynamic model is based on a d-q synchronous reference frame. Developed simulation model enables to be analyzed effects of UPFC and the other converter based FACTS devices (STATCOM, SSSC,IPFC) to power system very simply. Besides, it can be used for education purpose in graduate studies which is about converter based FACTS devices. On the other hand, it can be used for industrial purpose in terms of power system engineers’ investigations of effects of UPFC to power system. Simulated UPFC system consists of a load, UPFC and a power system with two machines. In simulation studies, functions of UPFC such as terminal voltage regulation and automatic power flow control is analysed and results are presented in case of graphics. Ill. 17, bibl. 18 (in English; abstracts in English and Lithuanian).DOI: http://dx.doi.org/10.5755/j01.eee.121.5.1662

Digital Simulation of the Generalized Unified Power Flow Controller System with 60-Pulse GTO-Based Voltage Source Converter

The Generalized Unified Power Flow Controller (GUPFC) is a Voltage Source Converter (VSC) based Flexible AC Transmission System (FACTS) controller for shunt and series compensation among the multiline transmission systems of a substation. The paper proposes a full model comprising of 60-pulse Gate Turn-Off thyristor VSC that is constructed becomes the GUPFC in digital simulation system and investigates the dynamic operation of control scheme for shunt and two series VSC for active and reactive power compensation and voltage stabilization of the electric grid network. The complete digital simulation of the shunt VSC operating as a Static Synchronous Compensator (STATCOM) controlling voltage at bus and two series VSC operating as a Static Synchronous Series Capacitor (SSSC) controlling injected voltage, while keeping injected voltage in quadrature with current within the power system is performed in the MATLAB/Simulink environment using the Power System Block set (PSB). The GUPFC, control system scheme and the electric grid network are modelled by specific electric blocks from the power system block set. The controllers for the shunt VSC and two series VSCs are pre- sented in this paper based on the decoupled current control strategy. The performance of GUPFC scheme connected to the 500-kV grid is evaluated. The proposed GUPFC controller scheme is fully validated by digital simulation.

Voltage profile enhancement by fuzzy controlled MLI UPFC

A fuzzy logic controlled multi-level inverter based unified power flow controller system is used in a transmission line to maintain voltage profile and protect/compensate against over-voltages, under-voltages, sags and swells. The controller is designed as a stand-alone module and tested in PSCAD-EMTDC environment. The results show that the controller is robust and can rapidly maintain voltage stability under different load conditions.

Interactions and multivariable design of multiple control functions of a unified power flow controller

One of the most important features of a unified power flow controller (UPFC) is its multiple control function. These control functions have been suggested to be implemented by multiple controllers. However, study examples presented in the paper demonstrate the existence of the dynamic interactions among different UPFC controllers, i.e. power flow controller, AC voltage controller and DC voltage controller. Due to the interactions, it is demonstrated in the paper that there are cases where separately designed and individually implemented stable UPFC controllers may result in poor control performance and even the closed-loop system instability when they are in joint operation. Hence, it is suggested in this paper that the multiple functional UPFC is treated as a multi-input and multi-output (MIMO) control system such that a single multivariable controller can be designed for the UPFC to perform the multiple control functions, which takes full account of the control interactions in the MIMO UPFC system.

Flying capacitor multilevel PWM converter based UPFC

A unified power flow controller (UPFC) based on the flying capacitor (FC) multilevel voltage-source converter (VSC) topology with phase-shifted sinusoidal pulse-width modulation (PWM) control is presented. This converter allows higher power handling, potentially lower power loss, lower harmonic distortion and hence less filtering requirements when compared with the typical two-level counterpart. The series converter injects a voltage with controlled magnitude and phase, to control the active/reactive power flow in a transmission line. The shunt converter absorbs/ supplies active power demanded by the series converter to maintain a constant DC link voltage, also providing independent reactive support to the network. A complete model of the proposed UPFC system is shown and control circuits are described in the synchronous d-q frame. Finally, simulation results are provided to confirm the robustness of the proposed system.