Power System Environment Research Articles

Enhancement of ATC by Optimal Allocation of TCSC and SVC by Using Genetic Algorithm

This paper proposes Improving of ATC is an important issue in the current de-regulated environment of power systems. The Available Transfer Capability (ATC) of a transmission network is the unutilized transfer capabilities of a transmission network for the transfer of power for further commercial activity, over and above already committed usage. Power transactions between a specific seller bus/area and a buyer bus/area can be committed only when sufficient ATC is available. Transmission system operators (TSOs) are encouraged to use the existing facilities more effectively to enhance the ATC margin. Heavily loaded circuits and buses with relatively low voltages can limit ATC usually. It is well known that FACTS technology can control voltage magnitude, phase angle and circuit reactance. Using these devices may redistribute the load flow, regulating bus voltages. Therefore, it is worthwhile to investigate the impact of FACTS controllers on the ATC. In this thesis focuses on the evaluation of the impact of TCSC and SVC as FACTS devices on ATC and its enhancement during with and without line outage cases. In a competitive (deregulated) power market, optimal the location of these devices and their control can significantly affect the operation of the system and will be very important for ISO.

Mitigation of Power Quality Problems Using FACTS Controllers in an Integrated Power System Environment: A Comprehensive Survey

Mitigation of Power Quality Problems Using FACTS Controllers in an Integrated Power System Environment: A Comprehensive Survey

Adaptive error control in wireless sensor networks under harsh smart grid environments

PurposeHigh packet error rates and variable link capacity due to harsh electric power system environments make reliable communication a challenging task for WSN in smart grid. Therefore, to increase network reliability and hence, to improve smart grid system performance, there is an urgent need for reliable communication protocols. The purpose of this paper is to propose an Adaptive Forward Error Correction (AFEC) mechanism for different smart grid environments, including 500 kV outdoor substation and underground transformer vaults, to address these challenges.Design/methodology/approachThis paper presents the comparative performance evaluations of proposed AFEC mechanism for different smart grid environments. Simulation experiments have been performed by extending the ns‐2 network simulator. It also introduces existing and potential smart grid applications, research challenges, and opportunities of smart grid.FindingsComparative performance evaluations show that the proposed AFEC mechanism achieves high communications reliability without causing unnecessary network overhead. Also the advantages of existing smart grid applications have been presented.Originality/valueThe paper shows that high communications reliability without causing unnecessary network overhead has been achieved. Also comprehensive reviews of WSN smart grid applications have been presented.

Load frequency control of a realistic power system with multi-source power generation

In this paper, load frequency control (LFC) of a realistic power system with multi-source power generation is presented. The single area power system includes dynamics of thermal with reheat turbine, hydro and gas power plants. Appropriate generation rate constraints (GRCs) are considered for the thermal and hydro plants. In practice, access to all the state variables of a system is not possible and also their measurement is costly and difficult. Usually only a reduced number of state variables or linear combinations thereof, are available. To resolve this difficulty, optimal output feedback controller which uses only the output state variables is proposed. The performances of the proposed controller are compared with the full state feedback controller. The action of this proposed controller provides satisfactory balance between frequency overshoot and transient oscillations with zero steady state error in the multi-source power system environment. The effect of regulation parameter (R) on the frequency deviation response is examined. The sensitivity analysis reveals that the proposed controller is quite robust and optimum controller gains once set for nominal condition need not to be changed for ±25% variations in the system parameters and operating load condition from their nominal values. To show the effectiveness of the proposed controller on the actual power system, the LFC of hydro power plants operational in KHOZESTAN (a province in southwest of Iran) has also been presented.

An implementation of modified scatter search algorithm to transmission expansion planning

Transmission network expansion planning (TNEP) is one of the most important tasks in the field of power systems, especially in deregulated power system environments. TNEP is a nonlinear mixed integer programming problem that can be solved via hybrid heuristic algorithms. This paper presents a modified scatter search algorithm (MSSA) to reinforce the ordinary scatter search algorithm (SSA) to be equipped for handling large scale transmission expansion planning (TEP) problems. The proposed methodology is based on the SSA, incorporating some improved strategies so as to decrease the number of linear programming problems required to be solved iteratively. In this study, it is shown that the MSSA can handle TEP problems faster than the ordinary SSA, as well as other implemented algorithms. Case studies and simulation results show the significant performance of the proposed method in comparison with some studies addressed in common literature.

Solving Bilevel Programming Problems Using a Neural Network Approach and Its Application to Power System Environment

In this paper, a hybrid neural network approach to solve mixed integer quadratic bilevel programming problems is proposed. Bilevel programming problems arise when one optimization problem, the uppe...

Application of bifurcation theory in dynamic security constrained optimal dispatch in deregulated power system

In a deregulated environment of power systems, the transmission networks are often operated close to their maximum capacity. Besides, the independent system operator must operate the system to satisfy its dynamic stability constraints under credible contingencies. In this paper, a novel technique based on iterative stability constrained Optimum Power Flow is proposed. Particle Swarm Optimization methodology is employed to maximize the social welfare with consideration of static and dynamic functional operating constraints and Dynamic Loading Margin (DLM) requirements with respect to normal condition and contingencies. New linear Hopf bifurcation (HB) index is used for fast detection of the DLM. Furthermore, since the pattern of load increase is difficult to be predicted in the new market environment, a method for determining sensitive loading direction associated with DLM is proposed. IEEE14 bus test system with both supply and demand bidding are used to illustrate and test the proposed technique.

Genetically Optimized FACTS Controllers for Available Transfer Capability Enhancement

Improving of Available Transfer Capability (ATC) is an important issue in the current de-regulated environment of power systems. Power transactions between a specific seller bus/area and a buyer bus/area can be committed only when sufficient ATC is available. It is well known that Flexible AC Transmission Systems (FACTS) technology can control voltage magnitude, phase angle and circuit reactance. Using these devices may redistribute the load flow, regulating bus voltages. Therefore, it is worthwhile to investigate the impact of FACTS controllers on the ATC. In this paper focuses on the evaluation of the impact of Thyristor Controlled Series Capacitor (TCSC) and Static Var Compensator (SVC) as FACTS devices on ATC and its enhancement during with and without line outage cases. Real-code Genetic Algorithm (RGA) is used as the optimization tool to determine the location as well as the controlling parameter of TCSC or SVC simultaneously. The performance of the Real-code Genetic Algorithm has been tested on IEEE 24Bus Reliability Test System.

Multi-area economic dispatch with tie-line constraints employing evolutionary approach

Economic dispatch (ED) has the objective of generation allocation to the power generators in such a manner that the total fuel cost is minimized while all operating constraints are satisfied. For the sake of simplicity, ED is generally solved without accounting for transmission constraints. However, in deregulated power system environment it is essential to model the ED problem for practical multi-area cases with tie line constraints. Most of the conventional gradient based methods are time consuming, suffer from dimensionality problem and assume the fuel cost curves of generating units to be piecewise linear, monotonically increasing in nature. The resulting dispatch solutions are therefore inaccurate; sometimes producing infeasible solutions for modern generating units having non convex cost curves. On the other hand evolutionary methods do not suffer from convexity assumptions and achieve fast solutions even for complex non-linear, non-convex, multi-modal optimization problems. This paper reviews and compares some evolutionary techniques for multi-area economic dispatch (MAED). The paper presents an extensive comparison of the search capability and convergence behavior of i) Classical differential evolution (DE) and its various strategies ii) Classical particle swarm optimization (PSO) and iii) An improved PSO with a parameter automation strategy having time varying acceleration coefficients (PSO_TVAC) for solving MAED problems for two area and three area test power systems with 4, 10 and 40- generating units. The results are found to be superior compared to some recently published results. Keywords: Differential evolution, Multi-area economic dispatch, multiple fuel options, particle swarm optimization, transmission capacity constraints. Time varying acceleration coefficients (TVAC), Valve point loading effects.

A Comprehensive Survey of Optimal Placement and Coordinated Control Techniques of FACTS Controllers in Multi-Machine Power System Environments

This paper presents exhaustive review of various methods/techniques for coordinated control between FACTS controllers in multi-machine power systems. It also reviews various techniques/methods for optimal choice and allocation of FACTS controllers. Authors strongly believe that this survey article will be very much useful to the researchers for finding out the relevant references in the field of placement and coordination of FACTS Controllers.

Power Transformer Protection by Using Fuzzy Logic

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. Recently, the frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. And then, traditional approaches will likely be maloperated in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with MATLAB simulation software and showed a fast and accurate trip operation.

Application of dynamic rating to increase the available transfer capability

AbstractAs the deregulated environment of power systems has spread worldwide, it is essential to operate power systems efficiently and economically. With the advance of communication technologies and sensors, so‐called dynamic rating is now to be realized. Dynamic rating is a method which determines accurate ratings by utilizing real‐time information such as conductor temperatures, ambient temperatures, and wind speeds. The dynamic rating is considered to increase the thermal capacities of overhead transmission lines and therefore take on importance in the deregulated electric power industry. The importance of the dynamic rating lies mainly in the area of Available Transfer Capability (ATC) improvement. In this paper, the validity of the proposed dynamic rating application is shown from the viewpoint of ATC, especially ATC with thermal constraints. In addition, the possibilities of ATC estimations using sensitivities are verified for the purpose of reducing calculation time, considering the importance of real‐time simulation of ATC. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 40–47, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20537

Intelligent Agent Approach to the Control of Critical Infrastructure Networks

In this paper we propose an intelligent agent approach to control the electric power grid at a smaller granularity in order to give it self-healing capabilities. We develop a method using the influence model to transform transmission substations into information processing, analyzing and decision making (intelligent behavior) units. We also develop a wireless communication method to deliver real-time uncorrupted information to an intelligent controller in a power system environment. A combined networking and information theoretic approach is adopted in meeting both the delay and error probability requirements. We use a mobile agent approach in optimizing the achievable information rate vector and in the distribution of rates to users (sensors). We developed the concept and the quantitative tools require in the creation of cooperating semiautonomous subsystems which puts the electric grid on the path towards intelligent and self-healing system. Keywords—Mobile agent, power system operation and control, real time, wireless communication.

Congestion management utilizing concentric relaxation

In the market-oriented power system environment, congestion management is a novel term connoting the power system steady state security functions. A large number of transmission transactions are dispatched in the regional day-ahead market and traverse the network adding to the power flow loading of the grid elements. Congestion is defined as a network security limit violation prospective due to transactions. Congestion management is a set of measures aimed at solving the congestion problem. This paper devises the concentric relaxation assisted approach to open access transmission network congestion management. The DC load flow symbolic simulator generates line power transfer functions. Congestion management is a systematic procedure based on linear programming. The DC load flow symbolic simulator generates all constraints and the black-box optimization library function is used to solve the problem of congestion on a sample IEEE RTS power system.

A NEURO-FUZZY TECHNIQUE FOR DISCRIMINATION BETWEEN INTERNAL FAULTS AND MAGNETIZING INRUSH CURRENTS IN TRANSFORMERS

This paper presents the application of the fuzzy-neuro method to investigate transformer inrush current. Recently, the frequency environment of power systems has been made more complicated and the magnitude of the second harmonic in inrush current has been decreased because of the improvement of cast steel. Therefore, traditional approaches will likely mal-operate in the case of magnetizing inrush with low second component and internal faults with high second harmonic. The proposed scheme enhances the inrush detection sensitivity of conventional techniques by using a fuzzy-neuro approach. Details of the design procedure and the results of performance studies with the proposed detector are given in the paper. The results of performance studies show that the proposed algorithm is fast and accurate.

Power system deregulation and SMD: status and future projections

This paper discusses the structure of the electricity utility industry in California, United States. The State continues to regulate vertically integrated utilities that have reconstructed and regulates only the portion of the utility that distributes the electricity. Therefore in restructured states, generation and transmission entities are no longer regulated. Depending on the deregulated State, the distribution entity may or may not be a provider of electricity. In the deregulated power system environment, a complete and effective plan is needed to meet the challenges of a new energy market.

Derivation of UPFC DC load flow model with examples of its use in restructured power systems

The unified power flow controller (UPFC) integrates properties of both shunt and series compensations and can effectively alter power system parameters in a way that increases power transfer capability and stabilizes the system. This paper presents an approximate model for power flow studies that takes into consideration modeling of lossless UPFC-embedded transmission lines including the effect of line charging susceptance. The approximate model is then simplified to a dc load flow model that takes into account the modeling of the UPFC. The equations derived in this paper are applied to an optimal power flow of a small test system, where the results obtained by approximate load flow method are compared to those of dc load flow method. The results presented in the paper show valuable impacts of putting UPFC in service on out-of-merit costs and locational marginal prices (LMPs) in a restructured power system environment. The results show that the dc load flow relations can be modified to reflect the effects of the UPFC. In addition, results show that UPFC may reduce generation out-of-merit costs and let LMPs regain uniformity.

Fuzzy logic-based relaying for large power transformer protection

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. The frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. Then, traditional approaches will likely be maloperated in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.

Training and optimization of an artificial neural network controlling a hybrid power filter

A hybrid power compensator (HPC) consisting of a static VAr compensator and a dynamic compensator needs to be optimally controlled during the compensation of nonlinear loads. The HPC must be controlled to meet minimum requirements in terms of power factor and harmonic distortion, while at the same time minimizing its total cost. An artificial neural network (ANN) is used to control the HPC amidst a very dynamic power system environment. The performance of a reference ANN is evaluated while controlling an HPC connected to a typical nonlinear industrial load. The training and performance of the ANN is then optimized in terms of training set size, training set packing and ANN topology and the performance compared to the reference ANN. This paper highlights the importance of optimising the mentioned ANN parameters to achieve optimum ANN training and modeling accuracy. The results obtained reveals that the application of an ANN in controlling an HPC is feasible given that the ANN parameters are chosen appropriately.

Risk assessment in energy trading

This paper provides a state-of-the-art summary of risk assessment in energy trading. Techniques from financial engineering are needed by electric energy companies to manage price risk. These tools are needed by suppliers, distributors, and traders in a competitive electric power marketplace. Tools that have been adapted to the specific environment of the electric power system include portfolio analysis and hedging instruments. This paper provides a comprehensive critical literature survey of what has been applied to date in the power markets and which areas continue to need additional research. One example market scenario is used throughout the paper to demonstrate the usefulness of the risk assessment methods.