In this paper, the dynamics of a dc-ac resonant self-oscillating LC series inverter is analyzed from the point of view of piecewise smooth dynamical systems. The system under study is defined by two symmetric configurations and its bifurcation analysis is performed in a one dimensional parameter space. This analysis reveals that a non smooth transition takes place between two strongly different dynamical behaviors. The first one is an oscillating regime, which is the one used in applications and it involves a repetitive switching sequence between the system configurations. This behavior is exhibited whenever the open loop equilibrium corresponding to the system configurations are foci. The second one is a non desired stationary regime corresponding to the equilibrium points of node typewhose stable manifolds preclude the appearance of oscillations.
In medium and high power applications, the BLDC motor is associated to multi-level inverters particularly the three levels NPC topology (B12). To improve the torque performance of the B12-inverter fed BLDC motor drives, this paper deals with the synthesis and performance analysis of three control strategies, namely: (i) DCC strategy with current controlled, (ii) DTC1 strategy, with torque controlled, inspired from the one developed by Takahashi in induction motor drives and (ii) DTC2 strategy that eliminates the torque dips penalizing DTC1. Simulation results, carried out considering low and high reference motor speeds, prove the high performance exhibited by the proposed DTC2 strategy which exhibits a remarkable reduction of the torque ripple and a low distortion in the line currents.
This paper aims to investigate the electrical energy losses (ΔE) in the Jordanian national electrical power system (ES); their types, values, as well as their impacts on overall performance of the energy system. The main focus of the paper is to calculate and investigate the value of the technical losses (ΔET) as well as the commercial losses (ΔEC) to the whole system losses value. In this paper, analyses of the (ΔE) data are carried out for the last sixteen years. This period of time is divided in two equal intervals of time; which are (2000-2007) and (2008-2015). The analyses concentrate mainly on the (ΔEC) with special attention on the black losses of energy (theft), (ΔEB1). The results of the two time periods are compared and evaluated by using statistical indexes. Furthermore the paper attempts to provide answers to the following questions: How and up to what value can (ΔEC) be minimized? What is the economic influence of (ΔEC) in [MWh]? Finally, a set of conclusions and recommendations on the obtained results are along with offered of the commercial losses for the next five years a forecast.
This paper proposed a new frequency changer which can be regarded as a current source cycloconverter. Frequency changing is achieved by mixing two or more amplitude modulated current waves at supply frequency using power transistors. By appropriate selection of the modulation indices and phase shift between the supply voltages, the supply frequency component can be entirely suppressed. The harmonics content of the resulting current wave is found to be very low. This converter solves the problems and severe restrictions associated with the ordinary full-cycle synchronous AM modulation when applied to three-phase and multi-phase systems. The process of conversion involves only natural commutation.
A simplified frequency method for the parameters design of a thyristor speed regulator of a DC motor is presented. The approximation of dynamics of the thyristor controller by Pades expansion simplifies the design and gives more accurate results than that when using the approximation by means of Hurwitz polynomial approximation or other conventional approximation techniques. The proposed method gives a simple approach for analysis and design of DC drive system parameters without going to the more complicated methods suggested recently for solving the DC drive problems.
In this paper, we present a design problem targeting the improvement of the environmental performance of a railway traction transformer associated to a fully-controlled IGBT rectifier. The Life Cycle Assessment tool was used to evaluate and assess environmental impacts in order to obtain a single environmental criterion of the studied system. This environmental criterion is taken into account on the design stage of the transformer. The design problem with the new criterion is expressed as an optimization problem and solved by using a deterministic multi-objective algorithm. Results are shown as trade-off sets between the environment indicator and the subsystem mass. The convenient solution will be chosen according the price that consumers agree to pay for a reduced environmental footprint.
Recently, interest has been increased on model-based approaches for fault detection and particularly focused on observers. The fault detection methods based on observers are considered as successful method. This paper presents a comparative study between two observation techniques applied to field oriented control of permanent magnet synchronous machine (PMSM) under inter turn short circuit. These approaches are used to estimate the PMSM machine state vector and the fault current. The comparative study is done between the adaptive and the unknown inputs observer in order to choose which exhibits the highest performance. Finally, the simulation results are compared to validate the accuracy of analytic method.