Uthen Leeton

Optimal power flow solution using improved harmony search method

This paper describes the improved harmony search method (IHS) to solve optimal power flow (OPF) problems. The harmony search is one of meta-heuristic search methods inspired by the improvisation of musicians developed by Geem (2001) [23]. The proposed algorithm was tested with five standard IEEE test systems (6-bus, 14-bus, 30-bus, 57-bus and 118-bus test systems). The tests were divided into smooth and non-smooth fuel-cost cases. The comparisons among solutions obtained by sequential quadratic programming (SQP), genetic algorithms (GA) and IHS were conducted. As revealed from the simulated results, the effectiveness of the IHS for solving OPF problems was confirmed.

Impact of energy storage in micro-grid systems with DGs

This paper presents an impact study of energy storage on a micro-grid system consisting of a very small power producer of a biomass type. The energy storage used in this paper is a battery bank. It comprises a combination between shunt and series battery cells in order to implement a sufficient battery storage system. To verify the simulated battery storage system, one day operation of an electric power distribution system was tested. This simulation was performed using MATLAB software in order to support and also to balance the energy exchange between the generation (drawn from both substation and renewable energy plants) and the power demand of the entire system. With the energy storage plant of battery banks, a simple 6-bus test system with a total power generation of 6 MW is situated for test. Considering of four test cases (case 1: without energy storage installation and neglecting power losses, case 2: without energy storage installation but considering power losses, case 3: with energy storage installation but power losses neglected, case 4: with energy storage installation and also considering power losses). Power transmission losses used in this paper can be determined by using Newton-Raphson power flow solution method. The simulation of the test system was carried out by performing one day simulation with energy storage and energizing stored energy by using an appropriate algorithm. The results showed that the system with energy storage can lead to efficient energy usage and power loss reduction.

Multi-Agent Based Optimal Power Flow Solution

This paper describes multi-agent based optimal power flow solution in which total production cost is used as the problem objective to be minimized. In this work, simulation of peer-to-peer device coordination has been developed using Java Agent Development (JADE) software package. JADE provides a FIPA-compliant agent platform and a package to develop multi-agent systems used in this paper. Six agent types are established. They are i) load agent ii) power generating plants agent, iii) transformer tap-setting agent iv) reactive power agent v) optimal load-flow agent and vi) management agent. In this paper each agent has been modeled as an intelligent agent, which joins to a container to form the multi agent system for solving optimal power flow problems. In this paper, the standard IEEE 6-bus test power system was employed. The results of this proposed system showed that the use of multi-agent systems enables possibility of applying optimal power flow in real-world applications.

Optimal reactive power flow with distributed generating plants in electric power distribution systems

This paper presents the solution of reactive power flow optimization for electric power distribution systems integrating with distributed generating (Distributed Generator: DG) plants which can support daily load demand. To reduce the total energy losses of the entire system, transformer tap and reactive power injection from available reactive power source are required. The setting of variables based on a particular load demand is to minimize losses by using particle swarm optimization in solving optimal power flow problems. The test system used in this paper is a 6-bus test power system. This study shows that the full adjustment of both transformer taps and reactive power injection is a better approach than adjustment only the transformer taps or the reactive power injection.

Optimal power flow using artificial bees algorithm

This paper presents a demonstration of solving optimal power flow problems by using one of swarm intelligences, called artificial bees algorithm. The objective of the problem can be expressed by taking the total production cost into account with required constraints. Among potential intelligent search methods, artificial bees algorithm is new and just developed since 2005. In this paper, the artificial bees algorithm is exploited to demonstrate its use of solving the optimal power flow problem. A 6-bus power system was situated for test. Sets of optimal parameters with respect to economic objectives can be efficiently found. This revealed that the artificial bees algorithm is one of efficient methods for solving the optimal power flow problem.

Application of harmony search to optimal power flow problems

This paper presents the use of the harmony search method for solving optimal power flow problems. The harmony search method mimics a jazz improvisation process by musicians in order to seek a fantastic state of harmony. To assess the searching performance of the proposed method, a 6-bus test power system was challenged. Satisfactory results obtained from the proposed method were compared to those obtained by genetic algorithms, particle swarm optimization, and the quasi-Newton with BFGS formula.

Application of key cutting algorithm to optimal power flow problems

This paper describes optimal power flow calculation in which the fuel cost function is used as the problem objective. Key cutting algorithm (KCA) based optimal power flow is formulated and then challenged in comparison with particle swarm optimization (PSO) and genetic algorithms (GA). Two standard test functions called Schaffer functions are tested. Also, a IEEE standard 6-bus, 14-bus and 30-bus test power system are employed. The solutions obtained by the proposed method are superior and very useful. The algorithm and simulation are carried out using MATLAB programming. As a result, all search algorithms can solve the optimal power flow problems however the key cutting algorithm-based optimal power flow gives the best solutions over the other two optimal power flow methods for the average and standard deviation values of the fuel cost.

Single train movement modelling and simulation with rail potential consideration

In general, the study of the train movement simulation begins with learning a simple single-train movement modelling. To be more realistic and more complete, the model should be able to calculate the profile of rail potential while a train is moving since rail potential plays an important role in the design of electrified railway service and is not supposed to exceed the critical value. The single-train movement modelling is developed to include and evaluate rail potential using multi conductor system and power flow calculation is applied in this study by using the current injection methods (CIM). The algorithm of the train movement with the gradient profile added and power flow calculation is created and implemented in MATLAB/M-file adopting Bangkok Transit System (BTS) — Sky Train Sukhumvit Line as a case study. It is expected to show the effectiveness of the proposed single-train movement modelling to evaluate rail potential, energy demand at substation, power losses and the voltage profile of the train during the movement of the train.

Modeling and simulation of voltage unbalance in AC electric railway systems using MATLAB/Simulink

This paper presents the modeling and simulation of voltage unbalance for AC electric railway systems. The development is based on MATLAB/Simulink program to determine voltages at the substation. The voltage unbalance factor (VUF) is used for this evaluation. Suvarnabhumi Airport Rail Link (ARL) in Bangkok, Thailand, is chosen for test. This test system is supplied by a cyclic winding connection of two single-phase traction transformers in which its primary side connected to the 69-kV transmission system of MEA (Metropolitan Electric Authority) power grid. The AC railway power feeding is a direct feeding scheme via 25-kV overhead catenary system. The total service distance of the ARL is 28.298 km with 8 passenger stations. The multi-train movement simulation is developed and embedded into the MATLAB program. The simulation results show that the operating voltage and the VUF during the train service can be obtained.

Effect of partial charging at intermediate stations in reducing the required battery pack capacity for a battery powered tram

Despite the fact that electric trains are ideal foi commuter rail service, most often the cost to electrify idle railway routes is unjustifiable. In an effort to replace diesel commuter trains serving short and idle routes, with battery powered trams; this paper evaluates three battery charging options. If batteries are only to be charged at terminal stations the battery powered tram simulated in MATLAB would need a 57.6 kWh battery pack to travel a distance of 12 km with six intermediate stations, limiting the minimum state of charge to 40%. A one minute, 5C partial charging at one and two of the intermediate station(s), reduced the needed battery pack capacity by 10% and 20% respectively. Having a battery chemistry with high charging rate capability, multiple smal trams rather than one big tram, and a good timetable will result into more reduction of the overall required number of batteries Thus, increase the attractiveness of an intermediate charging station.