M. Sailaja Kumari

Congestion management in deregulated power system by optimal choice and allocation of FACTS controllers using multi-objective genetic algorithm

Congestion management is one of the technical challenges in power system deregulation. This paper presents single objective and multi-objective optimization approaches for optimal choice, location and size of Static Var Compensators (SVC) and Thyristor Controlled Series Capacitors (TCSC) in deregulated power system to improve branch loading (minimize congestion), improve voltage stability and reduce line losses. Though FACTS controllers offer many advantages, their installation cost is very high. Hence Independent System Operator (ISO) has to locate them optimally to satisfy a desired objective. Genetic Algorithms (GA) are best suitable for solution of combinatorial optimization and multi-objective optimization problems. This paper presents optimal location of FACTS controllers considering branch loading (BL), voltage stability (VS) and loss minimization (LM) as objectives at once using GA. It is observed that the locations that are most favorable with respect to one objective are not suitable locations with respect to other two objectives. Later these competing objectives are optimized simultaneously considering two and three objectives at a time using multi-objective Strength Pareto Evolutionary Algorithms (SPEA). The developed algorithms are tested on IEEE 30 bus system. Various cases like i) uniform line loading ii) line outage iii) bilateral and multilateral transactions between source and sink nodes have been considered to create congestion in the system. The developed algorithms show effective locations for all the cases considered for both single and multi-objective optimization studies.

Comparison of Genetic Algorithms and Particle Swarm Optimization for Optimal Power Flow Including FACTS devices

This paper describes the performance of two population based search algorithms (Genetic Algorithms and Particle Swarm Optimization) when applied to Optimal Power Flow (OPF) including Static VAR Compensator (SVC) and Thyristor Controlled Series Compensator (TCSC) devices. The OPF optimizes a power system operating objective function, while satisfying a set of system operating constraints. The basic OPF solution is obtained with fuel cost minimization as the objective function and the optimal settings of the power system are determined. OPF can also be formulated for reactive power optimization, as minimization of system active power losses and improving the voltage stability in the system. In the present paper different objective functions that reflect Fuel cost minimization, System power loss minimization, Voltage Stability Enhancement (L-index minimization), Power loss minimization with SVC device and Power loss minimization with combined application of SVC and TCSC devices have been considered. To monitor and improve voltage stability in power system, minimization of sum of squared L-indices of all the load buses is considered as objective function in OPF. This index also guides the optimal location for VAR compensation. During normal operating conditions a planning engineer requires that all line flows and voltages are within limits while minimizing investment (including losses). While during outage conditions, line loading and voltages are again desired within limits while minimizing investment. It is important to obtain feasible solutions with in a minimal amount of engineering time.

A comparison of embedded cost based transmission pricing methods

In the restructured power market, it is necessary to develop an appropriate pricing scheme that can provide the useful economic information to market participants, such as generation, transmission companies and customers. Proper pricing method is needed for transmission network to ensure reliability and secure operation of power system. Accurately estimating and allocating the transmission cost in the transmission pricing scheme still remains challenging task. This paper gives an overview of different costs incurred in transmission transaction, types of transmission transactions and the transmission pricing methodologies. Embedded as well as Incremental cost methods are explained. It mainly focussed on determining the embedded transmission cost by various methods and compared the results for 6bus, IEEE 14bus and RTS 24 bus systems.

Impact of SCIG, DFIG wind power plant on IEEE 14 bus system with small signal stability assessment

In power systems voltage stability is a key issue which attracts worldwide attention. This research presents an implementation of a modified IEEE 14 bus system model in Power System Analysis Toolbox (PSAT) - free and open source software. A newly developed Squirrel Cage induction generator (SCIG) and Doubly Fed Induction Generator (DFIG) wind turbine model are modeled and connected to a modified IEEE 14 bus system. This paper investigates the impact of Squirrel Cage induction generator (SCIG) and Doubly Fed Induction Generator (DFIG) on the power system stability. Here considered wind generators are SCIG which is fixed speed and DFIG is variable speed. Small signal stability study has been conducted on a modified IEEE 14 bus system with SCIG, DFIG wind turbine systems and their simulation results have been analyzed in this paper.

Short-range fixed head hydrothermal scheduling using Fast genetic algorithm

This paper presents a Fast genetic algorithm for solving Hydrothermal scheduling (HTS) problem. Genetic Algorithms (GAs) perform powerful global searches, but their long computation times, put a limitation when solving large scale optimization problems. The present paper describes a Fast GA (FGA) to overcome this limitation, by starting with random solutions within the search space and narrowing down the search space by considering the minimum and maximum errors of the population members. Since the search space is restricted to a small region within the available search space the algorithm works very fast. This algorithm reduces the computational burden and number of generations to converge. The proposed algorithm has been demonstrated for HTS of various combinations of Hydro thermal systems. In all the cases Fast GA shows reliable convergence. The final results obtained using Fast GA are compared with simple (conventional) GA and found to be encouraging.

Optimal generation scheduling with operating reserves including wind uncertainties

The increase in the production cost of electricity from conventional energy sources, led systems to look for cheaper and cleaner energy sources like wind and solar. Over past few years wind energy integration drew more attention in the electricity markets. But, due to uncertainties in wind energy forecasts and to maintain system under balance condition, additional services are required. Such additional services are named as Ancillary Services. This paper presents a scheduling methodology for thermal generators, under wind integration uncertainties to serve the demand, while providing a schedule for operating reserve (Ancillary Services). In this paper minimization of Operating cost objective is considered which includes thermal units fuel cost and cost paid to reserve, required due to intermittency in wind energy forecast. The uncertainties in wind are also considered, wind output is modelled using Weibull probability density function (PDF). Dynamic Programming method with Priority-list is used to schedule thermal units. The performance and feasibility of the projected method is illustrated with case studies on 6 and 10 thermal generators test systems, along with one wind generator is considered and results are found encouraging.

LMP based electricity market simulation using genetic algorithm

In restructured electricity markets, an effective transmission pricing method is required to address transmission issues and to generate correct economic signals. Transmission line constraints can result in variations in energy prices throughout the network. These prices depend on generator bids, load levels and transmission network limitations. Locational Marginal Pricing (LMP) is a dominant approach in energy market operation and planning to identify nodal prices and manage transmission congestion. This paper presents a GA based security constrained economic dispatch (SCED) approach to evaluate LMPs at all buses while minimizing total system fuel cost for a constrained transmission system, with and without considering system losses. The proposed GA based SCED approach is applied on IEEE 14 bus, 75 bus Indian power system and New England 39 bus system. The results obtained are compared with conventional Linear Programming based DCOPF using Power World Simulator. Both fixed and linear bids are considered for generators. The load is assumed to be inelastic. The proposed GA based SCED for LMP calculation is proved to be very simple, reliable and efficient in all the cases studied. Further, the optimal redispatch of generators using GA leads to overall reduction in generation fuel cost.

Adaptive Wavelet Neural Network Based Wind Speed Forecasting Studies

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Aumann Shapley Method for Congestion Cost Allocation in Multilateral Transactions Framework of Restructured Power Market

Deregulation of Electricity market has not only led to increase in competition among generators, but also reduced electricity prices. It has introduced several issues in the market; two of them are congestion management and market power. Due to open transmission access all the participants have equal right to access transmission network. However, they have to bear the costs incurred to accommodate their transaction. The cost allocation is still a problem to be tackled efficiently. The prevailing problem is how to allocate the congestion cost among the market participants. An efficient and fair allocation of congestion cost would result in smooth operation of transmission system. It also helps in tackling congestion and market power. This paper proposes a novel approach using Aumann Shapley (AS) method of game theory for congestion cost allocation in a deregulated electricity market. The results obtained using proposed method are compared with uplift and nodal pricing methods for IEEE 14 bus system, New En...