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The paper deals with techniques to accelerate the DWT power quality analysis. Firstly a non-spline interpolation schematic is proposed for the evaluation of the first components near the right border of the signal. Comparisons are made between power quality indices, shape of details waveforms and runtimes, considering 3 cases. The first 2 cases correspond to data acquired on stand and correspond to...
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 specific matters concerning the electromagnetic disturbances introduced in an a.c. network by a static converter. A short description of the electronic converter AC-DC-AC of 1,500 W submitted to analysis is provided. The introduced disturbances are determined and analyzed considering the standard EN 50121-3-2. The disturbances transmitted through conducted emissions along the...
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...
The paper deals with the Discrete Wavelet Transform (DWT) analysis of quasi-stationary regimes (with small variations of magnitude and harmonic contents) in three-phase systems. The analyzed data, acquired on stand, correspond to a driving system using chopper and DC motor. Unfiltered currents are included in the first data set, unlike those from the second set. The harmonic orders to be filtered...
This paper presents a comparison of the performances related to compensation and transient response of active and passive power filters when operation relies on distorted mains voltages. MATLAB/Simulink models are used. Measurements acquired with a dedicated data acquisition system provided the parameters required by the real system simulation, namely a static excitation system of a power generator...
The paper presents some problems and solutions for instantaneous power theory applied to active power conditioning under distorted mains voltages in a MATLAB/Simulink approach. Simulation of a real system is made, namely a transformer which feeds a controlled rectifier bridge in an excitation system from a power system generator group, based on measurements acquired with a dedicated data acquisition...
The paper deals with the behavior of some RC cells used for the compensation of power distortions. Theoretical aspects related to the behavior of a RC circuit supplied from a non-sinusoidal voltage source are approached. Experimental data concerning the recordings and numerical processings for a three-phase load supplied from a rectifier fully controlled with thyristors are also included. The three-phase...
This paper deals with energy/power quality issues, correlated with Electromagnetic Compatibility (EMC) and electromagnetic interferences (EMI) which appear at urban transportation systems. One presents, briefly, some aspects regarding powers definitions for harmonic and/or unsymmetrical regimes from three-phase circuits, applicable to loads supplied from the a.c. line through low voltage power transformers...
The paper deals with the logic, implementation and testing of original algorithms that provide a fast identification of the frequency of interharmonic and harmonic disturbances when they pollute a monitored signal which in stationary state is characterized by periodical medium distortions. Unlike Fourier-based techniques, the identification requires for the (inter)harmonic identification only a small...
The paper analyzes the potential influence of a rectifier fully controlled with thyristors (RFCT) over some components of a power group with static switching. Problems related to the active power flows in distorting and/or non-symmetric regime are briefly presented. Also there are revealed issues related to the influence of non-linear and/or non-symmetric receivers of active powers over the active...
The discussed class of original hybrid wavelet algorithms is analyzed firstly relative to the decomposition vectors shape and periodicity in stationary regime. The studied signal corresponds to a current from the supplying network and has medium distortions within its first 4 periods, the other 2 being seriously affected after a fault. The noticed differences are responsible for different decomposition...
Theoretical considerations about the immunity tests within a GTEM cell are discussed. Electromagnetic field in a GTEM cell is presented. The conditions in a GTEM cell for a high degree of field uniformity according to the standard IEC/EN 61000-4-20 are discussed. The GTEM cells used for tests within the main equipment involved in the realisation of tests are presented (GTEM cell; Signal Generator/Power...
The paper deals with the analysis based on the Discrete Wavelet Transform (DWT) of stationary regimes in three-phase power systems with significant distortions. Firstly one presents the conclusion of preliminary evaluations used to select the most appropriate analysis technique: RMS values were evaluated using different DWT-based methods, analysis of errors, of memory consumptions and respectively...
Waveforms acquired from the excitation of the main generator from a power plant are analyzed with the Discrete Wavelet Transform (DWT). The proper Wavelet mother order and the proper decomposition tree were determined considering the energy deviations between subsequent decompositions and respectively the maximum approximation error generated by the signal re-composition process. Power quality indices...
Waveforms acquired from a power plant were analyzed with the Discrete Wavelet Transform (DWT). For the steady state case reference data were calculated (details and approximations vectors and 3-D tables which can be used to determine faster, in an original way, the parameters of a harmonic distortion). An original algorithm for the evaluation of parameters corresponding to harmonic disturbances was...
Some characteristics of a digital equipment used for parameters monitoring and events recording in a power system are presented. The PC-XX/104 PROCESS CONTROL equipment (PC/104 compatible) refers to modular structures that use a central unit for data acquisition and processing. The basic constructive variants include 8 analogue inputs (4 for voltages, 4 for currents) with (non)unified signals. The...
The paper deals with a solution for the compensation of a distorting regime from a distribution station for urban transport using a power active filter. Firstly the distorting regime is analyzed with a data acquisition system that provides the input data for the MATLAB/SIMULINK program used to size the active filter. The calculated parameters are afterward validated in MATLAB/SIMULINK. Experimental...
The paper presents the influence of a distorting element (D) from a power group over the lifetime of some test voltage transformers (T). D is a three phase rectifier fully controlled with thyristors and T are used to monitor the power group and measure the voltages across the main generator terminals. One presents the structure of the monitored power group's components, focusing on the electric quantities...
Waveforms acquired from a power plant were analyzed with the Discrete Wavelet Transform (DWT). For the steady state case reference data were calculated (details and approximations vectors and 3-D tables which can be used to determine faster, in an original way, the parameters of a harmonic distortion). An original algorithm for the evaluation of parameters corresponding to harmonic disturbances was...
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