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The paper deals with the behavior of a medium voltage/low voltage transformer (MV/LV), used to power the excitation circuit of a power group. The transformer's load is nonlinear, therefore inducing strong non-sinusoidal regimes in the primary and the secondary windings of the transformer. Non-sinusoidal regimes are due a thyristor rectifier used to power excitation. Two distinct situations are analyzed,...
The performance of some Fourier transform based fundamental current detection algorithms is evaluated and compared in this paper. Some difficult conditions are imposed by a load which draws a highly distorted current with a slight fluctuation, i.e. with non-equal semi-periods. The implemented algorithms are Recursive Discrete Fourier Transform (RDFT), Discrete Fourier Transform (DFT) implemented through...
The paper deals with the components design and the simulation of a photovoltaic power generation system using MATLAB and Simulink software. The power plant is composed of photovoltaic panels connected in series and parallel strings, a DC-DC boost converter and a three-phase inverter which connects to a 0.4 kV three-phase low voltage grid and a 20 kV medium voltage grid by means of a step-up transformer...
The paper analyzes the behavior of a three-phase consumer, consisting of several personal computers connected to a transformer's secondary phases. The modalities of monitoring and recording of electrical quantities are presented in this work. The structure of the consumer is described. The recorded waveforms are analyzed. The Fast Fourier Transform (FFT) analysis allowed for the decomposition of the...
This paper deals with issues related to a high power shunt active filter which is compensating the distorting regime and reactive power introduced by a silicon controlled rectifier. The current and voltage distortion is analyzed as a function of the system configuration and line reactors compensation. Different solutions are given for compensation and one of them is modeled and simulated in MATLAB/Simulink...
This paper presents measurements comprising both power quality and EMC fields for a static excitation system composed of a transformer and controlled rectifier bridge in a power system generator group. The replacement of the old auxiliary excitation generator eliminates the disadvantage of using electrical machines with the mass in motion inertia and wear over time, but with the price of facing two...
The paper deals with a wind power generation system which consists in wind turbines driving an asynchronous Doubly-Fed Induction Generator — DFIG connected to a 0.4 kV three-phase network. The wind turbines which use DFIG generators provide a constant frequency although the rotor operates with variable speed, by means of the converter with IGBT AC-DC-AC transistors based on PWM control. There are...
The paper deals with Power Quality (PQ) and Electromagnetic Compatibility (EMC) related problems, occurred during the operation of a driving system with induction motor and AC-DC-AC converter. The induction motor's driving system is presented, along with its characteristic features. An analysis is made with respect to the power quality indices related to the voltage and current absorbed from the power...
This paper presents the simulations made with a special software (EMTP-RV) for the analysis of transient regimes corresponding to the disconnection of a generator from the supplying bars from a power naval system, which is a system with limited power. One could determine the effects of driving various protections at the chosen timings. Based on the waveforms analysis one could evaluate the effects...
A medium/low voltage transformer from a distribution substation for urban transports operating in a highly distorting regime is analyzed. Regimes of idle running, running with non-linear load, respectively fault (short-circuit) are presented from the theoretical point of view. The results yielded by their operation simulation using MATLAB / SIMULINK are discussed. Aspects related to the measurement...
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