Mojgan Hojabri

Available Transfer Capability Calculation

The maximum power that can be transferred from one area to another area is called transfer capability. In 1996, North American Electric Reliability Council (NERC) established a framework for Available Transfer Capability (ATC) definition and evaluation. According to the NERC definition, ATC is the transfer capability remaining between two points above and beyond already committed uses (NERC, 1996). The ATC value between two points is given as:

PID controller adjustment for MA-LFC by using Imperialist Competitive Algorithm

In this paper a new evolutionary computing method based on Imperialist Competitive Algorithm (ICA) is used for tuning the elements of a PID controller which is applied in a Multi Area Load Frequency Control System (MA-LFC). If a large power imbalance is suddenly happened in a multi area power electric system, generation units and also consumer sides will be affected by the distortion in the energy balance between both two sides. This inequality is firstly handled by the kinetic energy of the system turning components, but, eventually, the frequency will change. Therefore, LFC is considered as one of the most challenging issues in power system control and operation. PID type controllers are conventional solutions for MA-LFC. The three parameters of the PID controllers have been adjusted traditionally. In this paper, a PID controller is applied for the MA-LFC problem and then its parts are modified by using ICA method. To validate the application of the technique, a multi area network with some uncertainties is provided. Finally the results of the ICAPID controller are compared with the ones of GA optimized controllers. The simulation results show the success and the validity of the ICA-PID controller in compare with the GA - PID controller.

Photovoltaic Grid-Connected Modeling and Characterization Based on Experimental Results

A grid-connected photovoltaic (PV) system operates under fluctuated weather condition has been modeled and characterized based on specific test bed. A mathematical model of a small-scale PV system has been developed mainly for residential usage, and the potential results have been simulated. The proposed PV model based on three PV parameters, which are the photocurrent, IL, the reverse diode saturation current, Io, the ideality factor of diode, n. Accuracy of the proposed model and its parameters evaluated based on different benchmarks. The results showed that the proposed model fitting the experimental results with high accuracy compare to the other models, as well as the I-V characteristic curve. The results of this study can be considered valuable in terms of the installation of a grid-connected PV system in fluctuated climatic conditions.

Wind farm reactive power optimization by using imperialist competitive algorithm

In this paper a new evolutionary computing method based on imperialist competitive algorithm (ICA) is used for optimization of the reactive power in a wind farm. The output power and also the reactive power of wind farms are not constant due to the oscillation in wind speed. Reactive power optimization is known as an efficient way to have an improvement in power quality and also to reduce power loss. The conventional optimization algorithms have some drawbacks, such as slow convergence and premature. ICA as one of the newest optimization algorithm could be applied in order to optimization of the reactive power and overcomes the difficulties which are coming from the traditional methods. In this paper, the reactive power consumption of a wind turbine is optimized by using (ICA) method. To illustrate the application of the method, a wind farm with some uncertainties is provided. Finally the results of the ICA method are compared with the one of conventional method. Results show that the proposed reactive power optimization method is simple and effective.

User-friendly tool for power flow analysis and distributed generation optimisation in radial distribution networks

The intent of power distribution companies (DISCOs) is to deliver electric power to their customers in an efficient and reliable manner – with minimal energy loss cost. One major way to minimise power loss on a given power system is to install distributed generation (DG) units on the distribution networks. However, to maximise benefits, it is highly crucial for a DISCO to ensure that these DG units are of optimal size and sited in the best locations on the network. This paper gives an overview of a software package developed in this study, called Power System Analysis and DG Optimisation Tool (PFADOT). The main purpose of the graphical user interface-based package is to guide a DISCO in finding the optimal size and location for DG placement in radial distribution networks. The package, which is also suitable for load flow analysis, employs the GUI feature of MATLAB. Three objective functions are formulated into a single optimisation problem and solved with fuzzy genetic algorithm to simultaneously obtain DG optimal size and location. The accuracy and reliability of the developed tool was validated using several radial test systems, and the results obtained are evaluated against the existing similar package cited in the literature, which are impressive and computationally efficient. Keywords: distribution networks, distributed generation, graphical user interface, PFADOT, fuzzy genetic algorithm, optimisation

CFD analysis of wind blocking vs. Venturi effect: A case study in tropical climate

Wind catchers are structures used for natural ventilation using the two basic principles of stack effect and wind induced natural ventilation and has recently attracted a lot of attention due to relying only on the free sustainable energy of wind and hence being able to reduce energy expenditure and greenhouse gas emission to a considerable amount. Even though this structures have been used for thousands of years in Iran and other regions of the Middle East but due to the low temperature difference between the indoor and outdoor in hot and humid climates these structures have not been used. However by the finding that stack ventilation has negligible effect on the ventilation compared to wind induced ventilation, hopes have arisen to provide comfort and high ventilation rates by high air exchange rates. Venturi shaped roof as one of the most effective way of producing driving force for ventilation is studied in this paper. A specific venturi shaped roof in University of Putra Malaysia was considered and a case study and CFD simulations were performed. The results showed that the venturi effect could be seen in the specific roof and hence a correct choice of ventilation technique and design has been applied for this case. Even though the results are optimistically stated and further studies and validation is required but could be a good initiation towards more efficient use of sustainable energy sources.

Krylov Subspace methods for Available Transfer Capability margins calculations

Nowadays considering more accuracy and speed to compute Available Transfer Capabilities (ATC) are important for electricity markets. Most studies involved load flow based and contingencies that often can be performed in reasonable time with the use of linear methods. Since the limitations of linear ATC calculations is the error produced by neglecting the nonlinear nature of real power flows. This paper presents Krylov Subspace methods that can reduce this error. By applying these methods for calculating ATC, the speed and the accuracy of them are calculated and compared to find the best one. All computations are tested on IEEE-30 bus system in MATLAB 7.1.