This paper is focused on an adaptive controller for the direct current (DC) voltage in three-phase three-wire shunt active power filters systems. Although the controller structure of the proportional-integral (PI) type is determined off-line and does not change, the prescribed DC voltage and the controller parameters are calculated in an adaptation block, depending on the non-active power to be compensated. The adaptive control is based on the design expressions for the DC circuit of the shunt active power filter found by the authors, based on the detailed analysis of its operation, during the active filtering. The performances of the proposed adaptive control and its advantages compared to the classical control (where the prescribed DC voltage and the controller parameters are constant) were first determined on the virtual model of a laboratory setup. Then, the adaptive control was implemented on the dSPACE 1103 control board, which allowed the experimental determinations that prove and support the results obtained on the virtual model.

Main objective of this paper is to provide a practical tool for the analysis and study of power quality and deforming regime. The LabVIEW graphical programming environment is used for designing virtual instrument to achieve the main two objectives. First goal is synthesizing a distorted signal by adding a number of sinusoidal harmonics which composing it. An accurate voltage signal and the current one are synthesized. Each harmonic amplitude, frequency and phase can be changed by simulation, noting the effects on the shape and parameters of the distorted signal obtained. For each signal distortion voltage and current are calculated following parameters: components level of the harmonic number including 0 (DC), 1 (fundamental), 2 (second harmonic), n (nth harmonic), up to and including the highest harmonic; the detected fundamental frequency resulting from searching the frequency domain; (THD) total harmonic distortion up to and including the highest harmonic. They are also calculated: active power, reactive power, apparent power and distorted power, power factor, each by component and the total value. The second objective of virtual instrument is power harmonic analysis for the experimental instantaneous input data of three-phase power consumer. These values instantaneous currents and voltages are obtained by data acquisition and are found saved in a text-based measurement file (.txt). This virtual instrument can be used at the same time in power quality education and research.

This article describes a control method called "direct power control" designed specifically for parallel active power filters. The purpose of this method is to attenuate harmonics in the supply current and offset reactive power problems. The main goal is to bring the active power and reactive power back to the reference values through hysteresis control. The output of the hysteresis controller is combined with the switching table to regulate active and reactive power in real time by determining the optimal switching configuration of the inverter. This study proposes a novel switching table design based on analyzing the impact of the inverter switching vector on the instantaneous reactive and active power derivatives. The goal is to reduce the number of commutations by eliminating zero vectors while maintaining the required DC bus voltage using anti-windup techniques based on PI controllers.

This paper present a virtual instrumentation system for learning the Operational Amplifiers (Op Amps) circuits function, design and analysis. By combining the schematic diagram and simulation tools with the multifunction data acquisition board (DAQ) and measurement features provided by LabVIEW, the real analog signals are easily sampled and then compared with the signals of simulated Op Amp circuits. With the proposed system can be studied Op Amp circuits in different configurations: inverting, adder and integrator amplifier. With minimal modifications can be added other circuits' configurations as: no inverting, subtraction, differential or other nonlinear circuits. Simulated Op Amp circuits have models that are based on the electrical characteristics of their components. Experimental platform consists of integrated circuit Op Amp, related components configured diagram and power supply. Voltage signals applied to the input of the circuit come from an external source or signal generator or are generated using DAQ module. The generated signals from DAQ module can be in the form of DC voltage, sinusoidal, triangular or rectangular; these signals parameters can easily be adjusted by software. All parameter values are measured using DAQ module and specially designed virtual instruments. The output signal values from DAQ module may be manually applied, point by point to the input of the circuit test or can be applied automatically.

The main objective of this paper is to solve a practical and current problem, by taking advantage of the virtual instrumentation in testing electrical machines. The abilities of virtual instrumentation are used to data acquisition, measurement and analyze the values of no-load testing's parameters for three-phase induction motor. The virtual measurement system bench is designed and consist from two principal components: the hardware components (six LEM transducers for measuring three voltages and three currents; elements for signal conditioning and power transducers; USB multifunction Input / Output module; a personal computer) and the software components (operating system for the computer; drivers for the acquisition and manipulation of data; virtual instrument for calculation and graphical presentation of results). The LabVIEW graphical programming environment is used for designing virtual instrument. This virtual measurement system bench is an easy to use device which can be used in engineering education laboratories from universities or in electrical machines testing workbenches; it is capable of data acquisition, storage or memorization on different media, visualization of different graphs or analysis on-line or off-line of the results obtained. The virtual measurement system described in the paper can work independently (in the Simulation mode or Real time Acquisition mode) or integrated as part of a future complex virtual system for measurement and analysis in the domain of electrical machines testing workbenches.

In this paper an modern solution to measure and analyse selected parameters of variable reluctance synchronous motor is presented. An virtual instrument with multiple options for selecting the analyzed parameters is described. The values of motor measurement voltages, currents and speed are read from a specified folder. With present virtual instrument it can be see the motor currents, voltages and speed waveforms and from the acquired data and recorded a set of parameters are computed. Boolean selector determine which signals are selected from the original seven signals (three current, three voltages and speed). It can be extract portions of data from the input signals. The extract portion is defined by the begin of offset (point of start) and the length (end the extraction). This instrument allow timing and transition measurements such as: pulse duration (pulse width), duty cicle (duty factor), preshoot (%), overshoot (%), slew rate. Also this virtual instrument allow to find the first highest (maximum) and the lowest (minimum) point in a set of values in signals of currents, voltages or motor' speed and find the time of the maximum and minimum values so determined. Knowing these values can be determined the range from the lowest point to the highest point in a set of motor's start current and voltage.