Thanatchai Kulworawanichpong

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.

Harmonic Identification for Active Power Filters Via Adaptive Tabu Search Method

Harmonic identification by using Adaptive Tabu Search (ATS) Method embedded in the active power filter is proposed in this paper. The use of the ATS identifies harmonic components more accurately and precisely. Besides the accuracy and precision, it is able to select only some particular harmonic orders that cause severe consequences to the system for elimination. This principle thus leads to the reduction in size and cost of hardware implementation + active power filters. In this paper, two test current waveforms are simulated to validate and verify the performance of the proposed algorithm. The satisfactory results obtained by this identification method are also com-pared against those obtained by the d-q axis based harmonic identification method. As a result, the ATS based method has better performance for eliminating only selective harmonic orders over the d-q method. Furthermore, the compensated current from the proposed method has a good transient response while there is the first-cycle delay due to the use of the d-q method.

The DQ Axis With Fourier (DQF) Method for Harmonic Identification

This letter proposes the DQ axis with Fourier (DQF) method for harmonic identification. The method, when used with a parallel active power filter, provides much better results than its predecessors, namely, the DQ axis and the sliding window Fourier analysis methods, in terms of harmonic elimination and phase balancing

Finite Convergence and Performance Evaluation of Adaptive Tabu Search

The naive tabu search (NTS) has been enhanced with two adaptive mechanisms namely back-tracking and adaptive search radius. The proposed search is called adaptive tabu search (ATS). The paper provides convergence and performance analyses of the ATS.

Optimal overcurrent relay coordination using genetic algorithms

This paper presents an intelligent approach for overcurrent relaying coordination design. Due to a powerful search scheme of the selected intelligent method, genetic algorithms (GA), digital relays are well coordinated to satisfy a large number of constraints, which are complicated over the ability of the conventional relay setting. The proposed scheme was demonstrated through a 6-bus power system, in which fourteen digital overcurrent relays were situated to be coordinated smartly. Also, the results obtained from GA were compared with those obtained by applying an efficient non-linear quasi-Newton method. It strongly confirms the effectiveness of the proposed method.

Moving Towards a New Era of Intelligent Protection Through Digital Relaying in Power Systems

This paper presents an intelligent approach for digital relaying de- sign. Due to a powerful search scheme of the selected intelligent method, digi- tal relays are well discriminated to satisfy a large number of constraints, which are so complicated over the ability of the conventional relay setting. Also, the proposed scheme is demonstrated through a small 5-bus power system, in which six digital relays are situated to be smartly discriminated.

Optimal overcurrent relay coordination using artificial bees colony algorithm

This paper presents optimal coordination of overcurrent relays by using artificial bees colony algorithm. The objective function of the relay coordination problem is to minimize the operation time of associated relays in the systems. The control variables used in this paper are the pickup current and time dial setting of relays. Quasi-Newton (BFGS), particle swarm optimization (PSO) and artificial bees colony (ABC) are employed to evaluate the search performance. For test, a 9-bus test power system was used. The simulation results showed that the artificial bees colony algorithm is capable to minimize the operation time of relays in the entire system. As a result, all search algorithms can solve optimal coordination relay which the artificial bees colony (ABC) gives the best solutions for coordination relay setting.

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.