A.M. Cozgarea

Bio: A.M. Cozgarea is an academic researcher from Ştefan cel Mare University of Suceava. The author has contributed to research in topics: Harmonics & Total harmonic distortion. The author has an hindex of 5, co-authored 9 publications receiving 44 citations.

An analysis of Rectifiier with Near Sinusoidal input current

Abstract: The IEEE-519 and IEC 61000-3 standards limit the individual harmonics current as well as the total harmonic distortion (THD) for nonlinear power electronic loads. We present a comparative study of a classical three-phase rectififier diode (TPRD) and RNSIC rectififier (Rectififier with Near Sinusoidal Currents), with respect to harmonic current distortion. Simulation results are experimentally verifified.

Robust-adaptive flux observer in high performance vector control of induction motors

Abstract: The paper presents the simulation a high performance control for induction machines with robust-adaptive rotor flux observer. The solution is tested by numerical simulation of the closed-loop vector control system.

Harmonie elimination and power factor improvement of three-phase rectifier using RNSIC variant

Abstract: Three-phase rectifiers with low harmonics and power factor correction have been receiving wide interest in the last years. The proposed method is based on the rectifier with near sinusoidal currents which is called RNSIC and which functions as power factor compensation in a wide range of load currents. The decrease of input current harmonics, below the limits imposed by IEEE 519/1992 and IEC 61000-3-4 international standards, allows the decrease of THD, reduces the reactive power, hence the increase in real power factor. The performance of the proposed RNSIC in power factor correction (PFC) regime is verified by simulation, as well as by experimentation, under different loads.

Wavelet multi-resolution analysis of TPRD and RNSIC input current

Abstract: It is well-known the fact that the frequency-domain approach obtained by Fourier transforms (FT) can provide amplitude-frequency spectrum while losing time-related information. In non-stationary regime, some of power electronics equipment connected to grid requires time related information, which cannot be provided by FT. Using discrete wavelet transform (DWT), we can preserve the information concerning time and frequency. In this paper, an wavelet analysis of input current of three-phase rectifier with diode (TPRD) and rectifier with near sinusoidal current (RNSIC) are presented. The experimental results are imported in MATLAB for multi-resolution analysis (MRA). Results of MRA confirm the reduction of RNSIC input current discontinuities, the waveform coming closer to sinusoidal form.

A comparative analysis of total harmonic distortion in TPRD and RNSIC

Abstract: The total harmonic distortion (THD) monitoring is an important challenge in the industrial and office building environment. The IEEE-519 and IEC 61000-3 standards limit the individual harmonics current as well as the THD for nonlinear power electronic loads. A harmonic current distortion comparative study of a classical three-phase rectifier diode (TPRD) and rectifier with near sinusoidal currents (RNSIC) are presented. Simulation results are experimentally verified.

Clustering Techniques in Load Profile Analysis for Distribution Stations

Abstract: The demand characteristic is the most important one in analyzing customer information. In a distribution network, there is in any moment certain degree of uncertainty about busses loads, and consequently, about load level of network, busses voltage level, and power losses. Therefore, it is very important to estimate first of all the load profiles of buses, using available data (measurements effectuated in distribution stations). The results obtained for various distribution stations demonstrate the effectiveness of the present method in overcoming the difficulties encountered in optimal planning and operation of distribution networks.

Harmonic currents generated by the voltage-source active rectifier

Abstract: Share of current harmonics, which is taken from the power net, increases with the use of diode and thyristor rectifiers (so-called characteristic harmonics of current). One of the ways to minimize these harmonics is to use the active rectifier. The principle of operation of active rectifier is based on correct switching of transistors, which allows the two basic functions: a) to keep the first harmonic of current in phase with the first harmonic of voltage, power factor is approximately one, b) to achieve almost sinusoidal current, which is taken from the grid. Characteristic harmonics in the spectrum of the current, which is drawn from the grid by active rectifier, are negligible. There appear new harmonics in the spectrum of the current; these new harmonics are produced by switching frequency of transistors. These harmonics are little dependent on load. That can cause the fact that the proportional value of the examined harmonics is high, although the absolute value is actually low. This paper briefly describes the voltage-source active rectifier and its workings. The main part is devoted to results from simulations and measurements in the laboratory.

A solution for the study and understanding of PID controllers

Abstract: Today, in most automatic process control applications in industry are used PID controllers. It is very important for the students to understand how work these controllers and how important it is to make an optimal tuning of these controllers. This paper presents a solution which permits to study and understand PID controllers. This solution is a closed-loop speed control system in a centrifugal load application which permits air flow control by fan's motor speed adjusts using a VFD. The PID controller is implemented in a PLC that control the VFD by CANOpen protocol.

Application with a XY-plotter controlled by PLC used in student laboratory works

Abstract: In many specific laboratories the students use only a PLC simulator software, because the hardware equipment is expensive. This paper presents a solution that allows students to study both the hardware and software parts, in the laboratory works. The hardware part of solution consists in an old plotter, an adapter board, a PLC and a HMI. The software part of this solution is represented by the projects of the students, in which they developed applications for programming the PLC and the HMI. This equipment can be made very easy and can be used in university labs by students, so that they design and test their applications, from low to high complexity [1], [2].