Journal of Operation and Automation in Power Engineering
Volume:1 Issue: 2, Summer - Autumn 2013

One of the important factors influencing outdoor insulators performance is pollution phenomenon. The pollution، especially during humidity condition، reduces superficial resistance of insulator and lead to a flow of Leakage Currents (LC) on the insulator surface، which may result in total flashover. The LC characteristics are affected by parameters such as nature and severity of pollution. Location of pollution is another parameter that can be effective. This paper presents the analysis of LC waveforms of insulator strings under different pollution location and Equivalent Salt Deposit Density (ESDD). The tests was performed on the HV porcelain suspension insulator string in which three adjacent discs of insulator string were contaminated and location of them changes along the insulator string. Besides، the effect of humidity and operating voltage on LC waveforms were investigated. Experimental data were analyzed in both time and frequency domain. Obtained results indicate that there is strong correlation between the location of pollution and LC parameters such as peak value ()، harmonic components and Total Harmonic Distortion (THD). Also، the ratio of fifth to third harmonic component () is presented as an important index that has strong relationship to the pollution location.

Economic dispatch with valve point effect and Prohibited Operating Zones (POZs) is a non-convex and discontinuous optimization problem. Harmony Search (HS) is one of the recently presented meta-heuristic algorithms for solving optimization problems، which has different variants. The performances of these variants are severely affected by selection of different parameters of the algorithm. Intelligent Tuned Harmony Search (ITHS) is a recently developed variant، which mitigates the drawbacks of parameter initializing by maintaining a proper balance between diversification and intensification throughout the search process. The proposed method is applied to five different cases of power systems and the effectiveness، feasibility، and robustness of method is explored through the comparison with reported results in recent literature. First three case studies are systems with 3، 13، and 40-units، considering valve- point effect. The fourth and fifth cases are six and 15-generation unit taking into account generator constraints including POZs، ramp rate limit and transmission line losses which is a challenging Economic Dispatch (ED) problem due to restriction in search space. Computation results imply the efficiency of the proposed method toward other optimization methods reported in recent literature، judged in terms of the objective function value and solution robustness.

Wind power generation is variable and uncertain. In the power systems with high penetration of wind power، determination of equivalent operating reserve is the main concern of systems operator. In this paper، a model is proposed to determine operating reserves in simultaneous market clearing of energy and reserve by stochastic programming based on scenarios generated via Monte Carlo simulation (MCS). This model considers the wind power، load and network uncertainties and includes the cost of involuntary load shedding and wind spillage. The proposed methodology is examined on an example and a case study to investigate various effects of wind power generation on the system operating reserves and costs.

In this paper، a novel compensator based on Magnetically Controlled Reactor with Fixed Capacitor banks (FC-MCR) is introduced and then power system stability in presence of this compensator is studied using an intelligent control method. The problem of robust FC-MCR-based damping controller design is formulated as a multi-objective optimization problem. The multi-objective problem is concocted to optimize a composite set of two eigenvalue-based objective functions comprising the desired damping factor، and the desired damping ratio of the lightly damped and undamped electromechanical modes. The controller is automatically tuned by optimization of an eigenvalue-based multi-objective function using Honey Bee Mating Optimization (HBMO) to simultaneously shift the lightly damped and undamped electromechanical modes to a prescribed zone in the s-plane so that the relative stability is guaranteed and the time domain specifications concurrently secured. The effectiveness of the proposed controller in damping low frequency oscillations under different operating conditions is demonstrated through eigenvalue analysis and nonlinear time simulation studies. The results show that the tuned HBMO-based FC-MCR controller which is designed by using the proposed multi-objective function has an outstanding capability in damping power system low frequency oscillations and significantly improves the power systems dynamic stability.

Flexible AC Transmission Systems (FACTS) controllers with its ability to directly control the power flow can offer great opportunities in modern power system، allowing better and safer operation of transmission network. In this paper، in order to find type، size and location of FACTS devices in a power system a Dedicated Improved Particle Swarm Optimization (DIPSO) algorithm is developed for decreasing the overall costs of power generation and maximizing of profit. Thyristor-Controlled Series Capacitor (TCSC) and Static VAr compensator (SVC) are two types of FACTS devices that are considered to be installed in power network. The purpose of this study is reducing the power generation costs and the costs of FACTS devices with considering different load levels. The main bases of this paper are using of Optimal Power Flow (OPF) and DIPSO algorithm to techno-economical analysis of the system for finding optimal operation. The Net Present Value (NPV) method is used to economic analysis of the system and power losses and maximum possibility load demand are considered for technical analysis. The proposed method is implemented on IEEE 57-bus test system and the achieved results are compared with genetic algorithm and particle swarm optimization methods to illustrate its effectiveness.

Accurate and effective electricity price forecasting is critical to market participants in order to make an appropriate risk management in competitive electricity markets. Market participants rely on price forecasts to decide on their bidding strategies، allocate assets and plan facility investments. However، due to its time variant behavior and non-linear and non-stationary nature، electricity price is a complex signal. This paper presents a model for short-term price forecasting according to similar days and historical price data. The main idea of this article is to present an intelligent model to forecast market clearing price using a multilayer perceptron neural network، based on structural and weights optimization. Compared to conventional neural networks، this hybrid model has high accuracy and is capable of converging to optimal minimum. The results of this forecasting method for Market Clearing Price (MCP) of Iranian and Nord Pool Electricity Markets، as well as Locational Marginal Price (LMP) forecasting in PJM electricity market، verify the effectiveness of the proposed approach in short-term price forecasting.

This paper proposes a Flexible Power Electronic Transformer (FPET) for the application in the micro-grids. The low frequency transformer is usually used at the Point of Common Coupling (PCC) to connect the low voltage grid and utility network to each other. The conventional 50Hz transformer results in enhanced low voltage-grid power management system during grid-connected operation. In this paper، the whole system represented as two، three-phase AC systems with an intermediate high-frequency transformer for power flow controlling. The FPET consists of a high frequency transformer and three-phase to single-phase matrix converter. The matrix converters are modulated with a Pulse Width Modulation (PWM) strategy for a bi-directional power flow control. Phase shift modulation strategy in two sides of FPET is used for power flow controlling by PI controller from utility network to low voltage grid and vice versa. FPET model is established in Matlab/Simulink software with controller for power flow controlling. Presented simulation results have shown the validity of the proposed control system for FPET through the Matlab/Simulink simulation.