Swapan Kumar Goswami

A new algorithm for the reconfiguration of distribution feeders for loss minimization

The authors report a power-flow-minimum heuristic algorithm for determining the minimum loss configuration of radial distribution networks. The algorithm is based on the concept of optimum flow pattern which is determined by solving the KVL and KCL (Kirchoffs voltage and current laws) equations of the network. The optimum flow pattern of a single loop formed by closing a normally open switch is found, and the flow pattern is established in the radial network by opening a closed switch. This process is repeated until the minimum loss configuration is obtained. A simple, fast and approximate power flow method has also been developed to assist the reconfiguration algorithm. The proposed reconfiguration algorithm has been found to give better network configuration than those obtained by some other methods. >

Optimum Siting and Sizing of Distributed Generations in Radial and Networked Systems

Abstract This article presents a genetic algorithm-based method to determine optimal location and size of the distributed generations to be placed in radial, as well as networked, systems with an objective to minimize the power loss. Several simulation studies have been conducted on radial feeders, as well as networked systems, considering single-distributed generation and multiple-distributed generations separately to minimize the power loss of the system subjected to no voltage violation at any of the buses. Simulation results are given, and the results are compared with the results of Wang and Hashem Nehrir [“Analytical approaches for optimal placement of distributed generation sources in power systems,” IEEE Trans. Power Syst., Vol. 19, No. 4, pp. 2068–2076, November 2004] and Gozel et al. [“Optimal placement and sizing of distributed generation on radial feeder with different static load model,” Proc. of IEEE International Conference on Future Power Systems (EPS 2005), pp. 1–6, Amsterdam, The Netherlands, 16–18 November 2005] to verify the proposed method.

An application of PSO technique for harmonic elimination in a PWM inverter

Harmonic elimination problem in PWM inverter is treated as an optimization problem and solved using particle swarm optimization (PSO) technique. The derived equation for computation of total harmonic distortion (THD) of the output voltage of PWM inverter is used as the objective function in the PSO algorithm. The objective function is minimized to contribute the minimum THD in the voltage waveform and the corresponding switching angles are computed. The method is applied to investigate the switching patterns of both unipolar and bipolar case. While minimizing the objective function, the individual selected harmonics like 5th, 7th, 11th and 13th can be controlled within the allowable limits by incorporating the constraints in the PSO algorithm. The results of the unipolar case using five switching angles are compared with that of a recently reported work and it is observed that the proposed method is effective in reducing the voltage THD in a wide range of modulation index. The simulated results are also validated through suitable experiments.

Distribution system planning using branch exchange technique

This paper reports the development of a new algorithm for the planning of radial distribution systems. The algorithm is based on the branch exchange technique. Branch exchange has been applied in two stages-between the elements of the network under each substation, called intrazone branch exchange and between the elements of the networks under adjacent substations, called interzone branch exchange. Intrazone exchange determines the optimum network configuration of each substation and interzone exchange determines the optimum service area of each substation. A complete power flow is required after each successful branch exchange. A new algorithm has also been proposed for the load flow of radial distribution networks. The algorithm is not based on node and branch numbering schemes and can handle multiple number of zones and therefore is particularly suitable for planning environment.

A new fuzzy based solution of the capacitor placement problem in radial distribution system

A fuzzy based method has been proposed for identification of probable capacitor nodes of radial distribution system. Simulated annealing technique has been used for final selection of the capacitor sizes. New fuzzy membership functions have been formulated where the active power membership is an exponential function of the nodal per unit active power and branch active power loss, the reactive membership function is a function of nodal reactive power and reactive branch loss. Voltage membership has been formulated in two ways - as function of the node voltage only and also as function of the nodal voltage and reactive power as well. The method has been applied to different test systems. It has been found that the proposed membership functions are less dependent upon weighting factors. The weighting factor may even be avoided at all. The proposed method thus is more general a other fuzzy based capacitor placement methods.

A PSO based optimal switching technique for voltage harmonic reduction of multilevel inverter

Selected lower order harmonics of multilevel inverter are eliminated while the overall voltage THD is optimized by computing the switching angles using particle swarm optimization (PSO) technique. The discontinuity in the solution of selected harmonic elimination (SHE) problem at certain modulation indices is avoided by optimizing the individual harmonics to allowable limits. While choosing the set of solution leading to minimum THD, the abrupt changes in the switching angles are discarded by limiting the voltage THD within allowable limits. Also the selected higher order harmonics are eliminated by additional switching along with the lower order harmonics. In order to reduce the computational burden for online application, the switching angles computed by the proposed PSO technique for optimum THD at varying modulation indices are stored as a look-up table in the DSP memory. The simulated results are also validated through suitable experiments.

Multi-objective Optimization of Distributed Generation Planning Using Impact Indices and Trade-off Technique

Abstract This article presents a multi-objective formulation for determining the best location and size of distributed generation. This multi-objective formulation includes reliability of service, system operational efficiency, cost of purchased energy, power quality, and system security as objective functions that are the primary concern of system planners. These objectives contradict each other and have trade-off relations. Conventional approaches for optimizing a single objective yield an uncompromised solution for such multi-objective problems. The multi-objective formulation is solved using an interactive trade-off algorithm to obtain compromised or most satisfactory non-inferior solutions. The system planner has a choice to include his/her preference on each objective through interactive steps. The practical situations, such as voltage rise phenomenon and voltage dependency of loads, are addressed, incorporating certain voltage constraints and appropriate load models. The test system is an existing Indian rural distribution network.

Differential Evolution Algorithm for Solving Unit Commitment with Ramp Constraints

Abstract This article proposes a differential evolution algorithm to solve the unit commitment problem with ramp constraints. Two implementations of the proposed algorithm—the first one using the binary code, and the second one using the integer code—have been developed. Both of these implementations have been found to converge to the same optimum solution requiring a different number of generations and a different CPU time. The proposed algorithm shows competitive performance with the best of the similar methods proposed earlier.

Expert algorithm based on adaptive particle swarm optimization for power flow analysis

An Expert algorithm based on particle swarm optimization (PSO) technique with adaptive PSO parameters has been developed for power flow analysis under critical conditions and multiple power flow solutions. Depending on the objective functions of the current and best solutions in the present generation, unique and innovative formulas are designed for two sets of PSO parameters, inertia weight and learning factors. For faster, sure convergence and overcome the limitations of conventional methods, PSO parameters are so designed that they are highly adaptive. To the best of our knowledge, it is the first report of applying Adaptive PSO (APSO) to solve power flow problems. Multiple power flow solutions which are used for voltage stability analysis can be obtained if proposed method is used with local search as accelerating technique. The proposed algorithm proves its robustness providing reliable and better convergence under high R/X ratios and maximum loadability limits. The effectiveness and efficiency has been established showing results for standard and ill-conditioned test systems.

An artificial bee colony-least square algorithm for solving harmonic estimation problems

Solving harmonic estimation problems in power quality signals has attained significant importance in recent times. Stochastic optimization algorithms have been successfully employed to determine magnitude of this information in an unknown signal contaminated with noise or containing additive dc decaying components. The present paper shows how a recently proposed stochastic optimization algorithm, called artificial bee colony algorithm, can be hybridized with least square algorithm to solve these problems effectively. The proposed algorithm has been tested for a series of case studies employing different benchmark environment situations and our extensive simulation tests validate the usefulness of the proposed algorithm and it could largely outperform several competing simulation algorithms, proposed in the recent past. The effectiveness of the proposed algorithm is further demonstrated for those situations where the number of harmonics present in the signal is also not known, along with the magnitude and phase of each harmonic.