Active and Reactive Powers Control of DFIG Based WECS Using PI Controller and Artificial Neural Network Based Controller

The purpose of this study is to improve the control performance of a Doubly Fed Induction Generator (DFIG) in a Wind Energy Conversion System (WECS) by using both of the conventional Proportional-Integral (PI) controllers and an Artificial Neural Network (ANN) based controllers. The rotor-side converter (RSC) voltages are controlled using a stator flux oriented control (FOC) to achieve an independent control of the active and reactive powers, exchanged between the stator of the DFIG and the power grid. Afterward, the PI controllers of the FOC are replaced with two ANN based controllers. A Maximum Power Point Tracking (MPPT) control strategy is necessary in order to extract the maximum power from the of wind energy system. A simulation model was carried out in MATLAB environment under different scenarios. The obtained results demonstrate the efficiency of the proposed ANN control strategy.

Line to Ground and Line to Line Fault Analysis in IEEE Standard 9 Bus System

Line to Ground (LG) and Line to Line (LL) faults are the two most frequently encountered faults in any power system network. For the purpose of designing advanced protection systems, detection of the location as well as the identification of the type of fault, from a remote location is of paramount importance. In this paper a Discrete Wavelet Transform based statistical analysis has been carried out to detect the fault type and location of LG and LL faults. IEEE standard 9 bus system has been considered for this purpose. Faults are made to occur in the load buses and outgoing currents from the generator buses are analyzed by Discrete Wavelet Transform (DWT) as these current waveforms are non-stationary in nature. Statistical parameters are calculated from the approximate and detail coefficients which have been derived from the DWT. Based upon these parameters, a rule set has also been made. Simulation work is performed with the help of MATLAB. Methods proposed here can be helpful for designing better protection schemes.

Multi-Objective Control Optimization for Congestion Avoidance in Computer Networks

Effective congestion control is an issue strongly impacting basic features demanded from modern network environment as reliability, high and stable throughput, and low delays. These characteristics define the quality of communication channels. Optimizing network nodes configuration for only one of mentioned features, can exacerbate other parameters. This paper focuses on avoiding and alleviating network congestions using multi-objective optimization for gain setting of used controllers. Unlike in other presented approaches, in this case the non-stationary, discrete, dynamical model is discussed. The significant advantage of this approach is in the better reflection of the real environment conditions, where the transmission delay is floating. As the further development of the control strategy, the controller with the memory of previous steps have been deployed. Such control strategy mitigates the unfavorable impact of extended delays. Both proposed control strategies tune the presented model of communication channel to alleviate the results of sudden, unexpected network state changes. It is obtained by maximization of available bandwidth usage combined with minimization of buffer utilization. This supports avoiding undesirable congestion effects like packet dropping, retransmissions, high delay, and low network throughput.

Sensorless Speed Control of IPMSM Using Sliding Mode Observer Based on Active Flux Concept

This paper proposes a new speed and position sensorless control method of Interior permanent magnet synchronous motors (IPMSM) using sliding mode observer based on Active Flux concept. First, a new description of IPMSM dynamic model in the stationary reference frame using active flux concept is proposed. The model obtained suits for both SPMSM and IPMSM in the stationary reference frame, Therefore, all that sensorless controls proposed for SPMSM can be directly and easily applied to IPMSM. Secondly, from the measurement of the voltages and the currents, a new analysis of the observability property is developed. Then, the sliding mode observer (SMO) structure and its design method are described in the stationary reference frame by using the active flux equation. A “chattering” phenomenon is reduced by using this technique. The stability of the proposed SMO was verified using the Lyapunov function. The speed and position of the IPMSM are estimated based on back EMF which are related to the active flux. Moreover, the zero d-axis current control strategy is used to control the IPMSM. Finally, the proposed method on the proposed model has been simulated and tested to show the effectiveness of the proposed scheme.

Design Optimization of Induction Motor Using On-Line Improved Genetic Algorithms

The main objective of this work is the application of a new architecture of genetic algorithms to the induction machine design in order to improve their performance. The latter is proposed by our research team based on modified crossing and mutation operators who have fixed values for conventional genetic algorithms. In addition, this version is characterized by a double loop and a random crossover. Firstly, to demonstrate the ability to locate the global optimum with this version algorithm a mathematical function was used. Then we approached the second phase which its application in real time to the induction motor optimized design problem. Knowing that, the machine is a highly coupled with multivariable system and constraints. Finally, the results obtained have been analyzed where we have found that satisfactory and can be declared that adaptation algorithm is effective in locating rapidly the region in which the global optimum exists in relation to the classical genetic algorithm.

Influence of Cable Lengths on EMI Emissions of a DC/DC Converter

The aim of this study is to evaluate the influence of the position of a DC/DC static converter between a source and a load with regard to the conducted EMC emissions measured on the source. An experimental model was established through the analysis of relevant stresses, such as the variation in the lengths of the source-converter, converter-load cables and the impact of the shield connection. Through this study, it was observed that the circuit was sensitive to too large variations in the capacities of common mode and of the link, and the results obtained make it possible to confirm the reality of the electromagnetic pollution of the static DC/DC converter "Buck" as a function of connections. The results of this research can be used in DC/DC network designs based on buck converters.