Raynitchka Tzoneva

Transient stability analysis of the IEEE 14-bus electric power system

It is widely accepted that transient stability is an important aspect in designing and upgrading electric power system. This paper covers the modeling and the transient stability analysis of the IEEE 14 test bus system using Matlab power system toolbox (PST) package. A three-phase fault is located at two different locations, to analyze the effect of fault location and critical clearing time on the system stability. In order to protect overhead transmission line, conductors and insulators, it is suggested that the faulted part to be isolated rapidly from the rest of the system so as to increase stability margin and hence decrease damage.

Impact of price penalty factors on the solution of the combined economic emission dispatch problem using cubic criterion functions

Thermal power plants play a major role in power production. The impacts of the various pollutants such as sulphur dioxide (SO2), Nitrogen oxide (NOx) and carbon dioxide (CO2) affects the environmental issues. The fuel cost of the generator in an economic dispatch problem can be presented by any order polynomial. The literature review reported that most of the papers consider the single pollutant using the second order polynomial function. The paper formulates the dispatch problem using a cubic function for both fuel cost and emission values. The impacts of various pollutants and price penalty factors such as Max-Max, MinMax, Average, and Common are considered in the multi-objective dispatch problem. The dispatch problem is solved using Lagranges method and the simulation results are provided for IEEE 30 bus system. It concludes that Min-Max Price penalty factor provides minimum fuel cost and minimum emission values in comparison to the other price penalty factors.

Comparative analyses of Min-Max and Max-Max price penalty factor approaches for multi criteria power system dispatch problem with valve point effect loading using Lagrange's method

The objective of the economic dispatch problem of electrical power generation is to schedule the committed generating units output so as to meet the required load demand while satisfying the system equality and inequality constraints. This paper solves the combined economic emission dispatch problem by Min-Max and Max-Max price penalty factor approaches using Lagranges method. The price penalty factor for the combined economic emission dispatch (CEED) is the ratio of fuel cost to emission value. The literature papers reported that most of them use Max-Max Price penalty factor for the CEED problem. This paper analyses Min-Max and Max-Max price penalty factors for CEED problem. This problem is solved for a five generator system by considering the valve point effect for both fuel cost and emission function. The total fuel cost by considering valve point effect of the combined economic emission dispatch problem is less when using Min-Max price penalty factor approach in comparison to Max-Max price penalty factor.

Distribution network fault section identification and fault location using wavelet entropy and neural networks

Display Omitted This paper proposes a new 2-stage hybrid method for distribution network fault section identification and fault location.Level-5 detail coefficients obtained from wavelet decomposition are used in computing the proposed wavelet-based indices.Artificial neural network models are developed using the proposed wavelet transform-based indices as inputs.A performance analysis of the developed models trained using the proposed indices is presented. Fault location in power system distribution networks is especially difficult because of the existence of several laterals/tap-offs in distribution networks. This implies that the calculated fault point can be wrongly estimated to be in any of the laterals. This paper proposes a new hybrid method combining Discrete Wavelet Transform (DWT) and artificial neural network (ANN) for fault section identification (FSI) and fault location (FL) in power system distribution networks. DWT was used in the analysis and extraction of the characteristic features from fault transient signals of the three phase line current measurements obtained at a single substation relaying point, rather than the double-ended approach used in the existing literature. Entropy Per Unit (EPU) indices are afterwards computed from the DWT decomposition, and are used as input to multi-layer ANN models serving as FSI classifiers and FL predictors respectively. The proposed hybrid method is tested using a benchmark IEEE 34-node test feeder. Comparisons, verification, and analysis made using the experimental results obtained from the application of the method showed very good performance for different fault types, fault locations, fault inception angles, and fault resistances. The proposed hybrid method is unique because of the pre-processing stage done with the DWT-EPU indices, the use of only line current measurements from a single relaying point, and the division of the FSI and FL tasks into sub-problems with respective ANN models.

Optimal PID control of the dissolved oxygen concentration in the wastewater treatment plant

The biological process for treatment of the municipal wastewater, the Activated Sludge process, is considered. The efficient performance of the water treatment process depends on the optimal control of the concentration of oxygen in the aeration tanks. This paper describes application of two standard PID controllers tuning methods for control of the nonlinear dissolved oxygen concentration process as a part of an adaptive optimal control strategy. Procedures for real time implementation of the tuning methods and the calculated control in the frameworks of Adroit SCADA and Matlab/Simulinks software are described. The calculations are done for COST benchmark and the University of Cape Town process structures and the ASM1 biological model.

MATLAB, LabVIEW and FPGA linear control of an inverted pendulum

Linearized model, pole placement and LQR linear controllers are derived for the inverted pendulum bytronic plant. Investigation of the real-time controller implementation using different PC (MATLAB/LabVIEW) and field programmable gate array (FPGA) CompactRIO (cRIO) platforms is done to prove and verify the FPGA capabilities in real-time control. The dynamic behaviour of the inverted pendulum under the same control, realized by the above various real-time platforms is obtained to be identical.

Method for real time optimal control of the activated sludge process

The problem for optimal control of the activated sludge process based on ASM1 model is considered. The objective is to determine a method for real time calculation of an optimal dissolved oxygen trajectory and the corresponding optimal state trajectories subject to minimization of both the deviations from the effluent requirements and the control energy consumption. The paper presents the developed reduced biological model of the activated sludge process, Athlone plant mass balance model and method for the optimal control problem solution in a real time. The optimal control problem solution is calculated in Matlab environment and the real time control is implemented in Adroit SCADA environment.

Power sector in Tanzania: Performance, trends and reforms

The United Republic of Tanzania is currently facing energy problems that have seriously affected its socio-economic development and environment. To solve these problems, the country is striving to exploit its renewable energy potential, among other efforts. This paper highlights the prevailing energy situation in Tanzania and provides a short review of potential energy resources. It then discusses current institutional efforts and capabilities in development, and commercialization of renewable energy technologies. The paper also identifies some barriers to promotion of renewable energy technologies as well as actions taken by the government of Tanzania to promote renewable energy technologies.

Neural networks for prediction of wastewater treatment plant influent disturbances

In order to develop an effective control strategy for the activated sludge process (ASP) of a wastewater treatment plant, an understanding of the nature of the influent load disturbances to the wastewater treatment plant is necessary. The wastewater treatment processes are dynamic and the interrelationships between variables are very complex. The values of the influent disturbances are usually measured off-line in a laboratory, as there are still no reliable on-line sensors available. This work proposes development of a neural network model for prediction of the values of the influent disturbances, which ultimately affect the activated sludge process. Three different dynamic multilayer perceptron feed-forward neural network models and three recurrent neural networks are developed for the prediction of the influent disturbances of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and flowrate respectively. The predictive performance of the multi-layer perceptron is compared to that of the recurrent neural network.

Method for a parallel solution of the multi area economic dispatch problem

Abstract The power system simulation software tools are traditionally designed for serial codes and optimized using single-processor computers. They are inadequate in terms of computational efficiency and execution time for the ever-increasing complexity of the power grid. Due to the above-mentioned sequential computing demerits, this paper used MATLAB data parallelism message passing interface software to execute the Lagranges and Particle Swarm Optimization (PSO) algorithms in parallel with multiple processor units with different and large data sets for the solution of the Combined Economic Emission Dispatch (CEED) problem. The two important advantages of using parallel computing approach to solve the power system economic dispatch problem are 1) to increase the efficiency (solution quality) and 2) to reduce the execution time (speed-up) of the parallelization process for the CEED problem solution. The comparison between the Lagranges and PSO data-parallel solution quality and execution time is presented for the CEED problem for Institute of Electrical and Electronic Engineers (IEEE) 30 bus and IEEE 118 bus systems. The paper contributes to the on-line real-time market analyses of the deregulated power system, which need improved solution quality and a fast computation process to solve the power system energy management (CEED) problems for proper discussion and decision making at the control center level.