[Show abstract][Hide abstract] ABSTRACT: In the past few decades, restructuring has overtaken all possible domains including the electric supply industry. Restructuring has brought about considerable changes by the virtue of which electricity is now a commodity and has converted into deregulated one. Such a competitive market has paved way for innumerable participants. This has led to overloading and congestion of transmission lines. Moreover, open access transmission network has ingenerated a more intensified problem of congestion. Thus, congestion management in power systems is germane and of central importance to the power industry. In this paper a review work is carried out to unite all the publications in congestion management.
No preview · Article · Sep 2015 · International Journal of Electrical Power & Energy Systems
[Show abstract][Hide abstract] ABSTRACT: This paper presents best weight pattern evaluation approach to solve short-term multi-objective hydrothermal generation scheduling (HTGS) which determines the allocation of power demand among the committed generating units, to minimize operating cost and minimal impacts on environment subjected to physical and technological constraints. A multi-chain interconnected hydro system having non-linear relationship between water discharge rate and power generation is undertaken with due consideration of water transport delay between connected reservoirs. The best weights are computed by conventional statistical measures, which characterize the correlation coefficients matrix evolution. The solution methodology hybridizes global and local search techniques. Predator-prey optimization (PPO) is undertaken as a global search technique and Powell's pattern search (PPS) is exploited as a local search technique. The results among the competing objectives obtained by the proposed method are compared with various results reported in the literature. The sensitivity and robustness of the proposed technique are evaluated by performing statistical analysis of results obtained based on independent runs. The integration of PPO and PPS improves the quality of solution and convergence characteristics.
No preview · Article · Nov 2014 · International Journal of Electrical Power & Energy Systems
[Show abstract][Hide abstract] ABSTRACT: Paper presents predator–prey based optimization (PPO) technique to obtain optimal generation scheduling of short-term hydrothermal system. PPO is a part of the swarm intelligence family and is capable to solve large scale non-linear optimization problems. PPO based algorithm combines the idea of particle swarm optimization concept with predator effect that helps to, maintain diversity in the swarm and preventing premature convergence to local sub-optimal. In this paper first of all feasible solution is obtained through random heuristic search and then thermal and hydro power generations are searched for optimum hydrothermal scheduling problem using PPO. Variable elimination method is implemented to handle the equality constraint by eliminating variable explicitly. These eliminated variables are considered by penalty method restricts slack units with in limits. Slack thermal generating unit for each sub-interval handles power balance equality constraint and slack hydro units handle water equality constraint. The performance of the proposed approach is illustrated on, fixed-head and variable-head hydrothermal power systems. The results obtained from the proposed technique are compared with the existing technique. From the numerical results, it is experienced that the PPO based approach is able to provide a better solution.
No preview · Article · Aug 2014 · Applied Soft Computing
[Show abstract][Hide abstract] ABSTRACT: In this paper, different Distribution Static Compensators (DSTATCOMs) topologies, state of the art, their performance, design considerations, future developments, and potential applications are investigated for power quality improvement. These DSTATCOMs for three-phase three-wire systems and three-phase four-wire systems are developed and installed in the distribution system for many functions, such as reactive power compensation, harmonics elimination, load balancing, and neutral current compensation. This paper is aimed to explore a broad perspective on DSTATCOMs to researchers, engineers, and the community dealing with the power quality improvement. A classified list of some latest research publications is also provided for quick reference.
No preview · Article · May 2014 · IEEE Transactions on Industrial Informatics
[Show abstract][Hide abstract] ABSTRACT: This paper presents a solution technique for combined emission constrained unit commitment problem (UCP) . The emission level is taken as a constraint in both the selection of units for generation and also in dispatching the real power among the committed units. The multi objective problem is converted into a single objective using max price penalty factor method. Since unit commitment problem is highly constrained and complex, we need a solution technique capable of solving such complex problems. Improved Shuffled Frog Leaping Algorithm (SFLA) is a memetic algorithm which deals with the behaviour of group of frogs searching for the location that has the maximum amount of available food. Leaping of the frog is improved by the introduction of cognitive component. This ensures the faster convergence and global optimal solution. The integer coded UC is used which avoids any extra penalty function for satisfying the minimum up/down constraint. The SFLA is used in two stages in this proposed method. This proposed algorithm has been implemented in Matlab 2011 environment. IEEE 14 bus system, IEEE 30 bus system, IEEE 56 bus system and IEEE 118 bus system are taken as the test system. We have taken 3 cases such as purely economical case, purely emission case and combined emission and economic case by varying the weighting factors for the constraints. The results of these cases are discussed to explain the effect of emission in selecting units and in economic dispatch.
[Show abstract][Hide abstract] ABSTRACT: In power system studies, congestion in transmission lines and utilization of flexible alternating current transmission system (FACTS) devices are closely associated. These devices are very important due to their role in power delivery system enhancement. It is to be noted that the generation companies can exercise their market power which depends on the line flows, line constraints, generators’ location and its share to the individual loads. This issue cannot be overlooked as it creates monopoliness which is against the deregulated market policy. The objective of this paper is to study the impact of market power when FACTS devices like thyristor controlled switching capacitor (TCSC) and thyristor controlled phase angle regulator (TCPAR) are used under steady state operation. The market power is determined using nodal must-run share (NMRS) index for the standard IEEE 14-bus system with and without the above FACTS devices and the results obtained are compared. All the above simulations are conducted in a MATLAB 7.9-R2009b environment.
No preview · Article · Dec 2013 · Frontiers in Energy
[Show abstract][Hide abstract] ABSTRACT: Major objective for the Thermal power generation is to minimize fuel consumption by allocating optimal power generation from each unit and to maintain emissions within the environmental license limit subject to equality and inequality constraints. The objectives considered in this paper for minimization i.e. cost and emission are of conflicting nature, therefore weighting method has been applied to convert multiobjective optimization problem to a scalar optimization. The weighting method assigns different weights to each objective function based upon their importance. The Particle Swarm Optimization (PSO) technique has been applied to find the best comprised solution. The equality constraints have been handled by exterior penalty method. Fuzzy cardinal approach has been used for the evaluation of the best solution. In order to show the effectiveness, the proposed approach has been tested on three test systems. Numerical results obtained from the proposed approach are compared with different techniques.
[Show abstract][Hide abstract] ABSTRACT: This paper proposes the effective utilization of unified power quality conditioner (UPQC) for interconnecting the PV modules to the grid using power angle control (PAC) method. A shunt active power filter (APF) is used to evacuate the power from the photovoltaic module in addition to compensating the current harmonics, load unbalance and reactive power. To accomplish this the series APF in the UPQC is used for supplying a part or whole reactive power required by the load in addition to compensating the sag, swell, supply voltage unbalance and distortions. This is made possible by controlling the phase angle and magnitude of series injected voltage called power angle control method. The reactive power and voltage compensation technique introduces a phase shift between the load terminal voltage and source voltage. The transient due to sudden phase shift is minimized using step by step introduction of series compensation voltage. The proposed method effectively utilizes the shunt APF and series APF in the UPQC for interconnecting the PV module to the grid. The simulation results from MATLAB/SIMULINK are discussed to validate the developed method.
No preview · Article · Jun 2013 · International Journal of Electrical Power & Energy Systems
[Show abstract][Hide abstract] ABSTRACT: The concept of market power has gained its importance after the electric power industry started a process of transition and restructuring since early 1990s or so. In this competitive electricity market, the operational and the physical constraints of the network possess major threat to the market by the generation companies in exercising its market power. This paper presents a comprehensive review on market power with various indices which were used in market power analysis and the evolution of research and development in the field of market power. The literature work presented in this paper has been divided into various sections to facilitate the upcoming researchers who carry out their research in the area of market power under various environments.
No preview · Article · Jun 2013 · International Journal of Electrical Power & Energy Systems
[Show abstract][Hide abstract] ABSTRACT: In the deregulated electricity market, it has become very important to determine the complete information about the participants who are utilizing the transmission network. Transmission line usage computation requires information of generator to load contributions and the path used by various generators to meet loads and losses. In the present restructured electricity market, it is necessary to develop appropriate pricing techniques that can provide the useful economic information to market participants. In this paper, the three existing techniques namely Zbus method, Zbusavg method and Relative Electrical Distance (RED) method for the network cost allocation is compared. It has been successfully applied on an IEEE 24 bus-Reliability Test System (RTS) and the results obtained are compared. The results obtained are quite encouraging and useful for the deregulated electricity market related issues. The simulation is carried out using MATLAB 7.8.0 (R 2009a).
[Show abstract][Hide abstract] ABSTRACT: This paper presents the unified power quality conditioner (UPQC) performance while interconnecting with photovoltaic (PV) modules in unbalanced and distorted distribution systems. The proposed configuration consists of UPQC and PV modules connected to a DC-link capacitor. The PV modules evacuated power without losing the UPQC fimctions of compensating reactive power, load current harmonics, unbalanced load current and voltage sag/swell. The uncontrollable switching states in the conventional hysteresis control method are mitigated using fixed switching frequency of neutral current control. The performance of the proposed interconnected system is analysed using simulations with MATLAB/Simulink.
[Show abstract][Hide abstract] ABSTRACT: In the deregulated environment, the economic related problems like generation dispatch, unit commitment, network cost allocation, congestion management, market clearing prices etc. are all associated with the geographical location of the generation companies and the consumers. The number of transmission lines, the distance and the voltage levels are some of the predominant factors in deciding the solution for the above problems for which electrical distance between the utilities is widely used as a tool by the power system researchers. In this paper, a complete analysis has been made on the concept of electrical distance and on the various factors affecting it. A sample five bus system is taken for analysis. The results are quite encouraging and help the researchers to extend the application of electrical distance in various domains.
No preview · Article · Jan 2013 · Lecture Notes in Electrical Engineering
[Show abstract][Hide abstract] ABSTRACT: In this paper, an IcosΦ algorithm based new DSTATCOM (Distribution Static Compensator) using three-leg VSC (voltage source converter) integrated with a zig-zag transformer is investigated for the power quality improvement in three-phase four-wire distribution systems. The zig-zag transformer is used for providing a path to the zero sequence fundamental as well as harmonics currents. In order to optimize the voltage rating of the VSCs, the zig-zag transformer is designed to have a tertiary winding for integrating the VSC. This new DSTATCOM provides the voltage regulation or power factor correction by reactive power compensation, harmonics compensation, load balancing and neutral current compensation in three-phase four-wire distribution system. The reference currents for the DSTATCOM is estimated using the IcosΦ algorithm and this is simple and with reduced computations. The performance of the proposed DSTATCOM system is demonstrated under linear and nonlinear balanced and unbalanced loads by simulation using MATLAB with its Simulink and simpower systems (SPS) tool boxes.
[Show abstract][Hide abstract] ABSTRACT: In power system studies, congestion in transmission lines and utilization of Flexible Alternating Current Transmission System (FACTS) devices are closely associated and it is very important due to their role in power delivery system enhancement. It is to be noted that the generation companies can exercise their market power which depends on the line flows and the line constraints, generators' location and its share to the individual loads. This issue cannot be overlooked as it creates monopoliness which is a threat to the deregulated market policy. The objective of this paper is to show how the generation companies' market power gets enhanced due the FACTS devices. FACTS devices like Thyristor Controlled Switching Capacitor (TCSC) and Thyristor Controlled Phase Angle Regulator (TCPAR) are taken and used under steady state operation. The market power is determined using Nodal Must Run Share (NMRS) index for the standard IEEE 14bus system with and without the above FACTS devices and the results obtained are compared. All the above simulations are carried out in MATLAB 7.9R2009b environment.
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Nov 2012 · International Journal of Electrical Power & Energy Systems
[Show abstract][Hide abstract] ABSTRACT: This paper describes an algorithm for optimum modifications for failure rate and repair time for a radial electrical distribution system. The modifications are with respect to a penalty cost function minimization. The cost function has been minimized subject to the energy based and customer oriented indices, i.e. AENS, SAIFI, SAIDI and CAIDI. Coordinated aggregation based particle swarm optimization (CAPSO) has been used for optimization. The algorithm has been implemented on a sample radial distribution system. The results obtained have been compared with those obtained using PSO.
No preview · Article · Nov 2012 · Applied Soft Computing
[Show abstract][Hide abstract] ABSTRACT: An integrated methodology that embeds global and local search technique is explored for solving multiobjective hydrothermal scheduling. Predator-prey optimization (PPO) is used as a base level search in the global search space and Powell's method as a local search technique. Predator-prey model is based on particle swarm optimization (PSO). In spite of several advantages of PSO as compared to other evolutionary methods, it has some major drawbacks such as local optimal trapping and lack of efficient capability to treat the constraints. PPO model includes predator and prey particles in population. The prey objective is to escape from the predators reaching to its lair, while predator's goal is to capture the prey that increase exploration and exploitation capability of PSO. Powell's method aims to fine tune the solution obtained from PPO and to enhance the search capability of proposed method. In addition, a penalty less constraint handling method is employed for considering equality and inequality constraints. Fuzzy methodology has also been exploited to find the best compromised solution. The proposed integrated technique is applied to three hydrothermal scheduling problems with valve-point effect of thermal generators and transmission losses. The proposed method yields high quality solution while satisfying all constraints.
[Show abstract][Hide abstract] ABSTRACT: Unit commitment (UC) problem is one of the medium term decision problems in power system and it is used to determine the mix/ combination of generators to be operated or to be idle. By solving the UC problem, once the binary data is obtained the next level is to find the optimum level of dispatch of each generators in the mix. For a large generating system UC program is a large scale, non linear mixed integer programming (MIP). This paper proposes a hybrid algorithm to solve UC problem by considering equality and inequality constraints. The objective of the algorithm is to minimize the fuel cost after meeting all the possible constraints. The proposed algorithm initially solved the UC problem by modified LR method. LR method most often gives sub optimal solution, so once the problem is solved by LR and if some of the output is infeasible then by solving it by heuristic technique such as priority list method, we can modify LR. The generation output level is determined by particle swarm optimization method. The algorithm was tested in four unit eight hour systems and ten unit twenty four hour system. The simulation output shows that the developed algorithm performed well and also applicable for large systems.
No preview · Article · Oct 2012 · International Review on Modelling and Simulations
[Show abstract][Hide abstract] ABSTRACT: In this article, a predator–prey-based optimization technique is applied to obtain the scheduling of a hydrothermal system with cascaded reservoirs, minimizing economic and gaseous pollutants and emission objectives. These objectives are mutually conflicting and are equally important. Predator–prey optimization is a stochastic optimization technique based on the particle swarm optimization concept having an additional predator effect that helps to explore the search area more efficiently due to the fear created by the predator. A heuristic search technique is applied for generating an initial feasible solution. The direct substitution method is implemented to handle the equality constraints, whereby dependent variables are determined from the equality constraint. Inequality constraints of dependent variables are taken care by incorporating an additional objective function represented by the fuzzy membership index, and other variables are set to their limits on violation. Fuzzy methodology has been exploited for solving a decision-making problem involving the multiplicity of objectives and selection criterion for the best compromised solution. The solutions obtained from the proposed technique are compared with other existing techniques, and results are found to be satisfactory. The proposed method has the capability to escape from local optimum solutions due to its predator effect, and it is easy to implement.
No preview · Article · Oct 2012 · Electric Power Components and Systems
[Show abstract][Hide abstract] ABSTRACT: In this paper, a new topology of DSTATCOM using three single-phase VSCs (voltage source converters) integrated with a zig-zag transformer is employed for the power quality improvement in three-phase four-wire distribution systems. The zig-zag transformer is used for providing a path to the zero sequence fundamental as well as harmonics currents. In order to optimize the voltage rating of the VSCs, the zig-zag transformer is designed to have a tertiary winding for integrating the VSCs. This new topology of DSTATCOM (Distribution Static Compensator) provides the voltage regulation or power factor correction by reactive power compensation, harmonics compensation, load balancing and neutral current compensation in three-phase four-wire distribution system. This topology has the advantages of the use of ‘off the shelf’ VSC, reduced kVA rating, optimum voltage rating of VSCs and hence less cost. The VSCs are integrated with a zig-zag transformer to realise a single unit by designing a set of third winding in the transformer. The performance of the proposed DSTATCOM system is demonstrated under linear and nonlinear balanced and unbalanced loads by simulation using MATLAB with its Simulink and simpower systems (SPS) tool boxes