EPQU Journal Volume 12 Issue 1

Leszek S. CZARNECKI
 Part 2: Three-Phase Three-Wire Linear Circuits
This paper summarizes the present state of discussions on power phenomena, power definitions and compensation in three-phase three-wire linear circuits with nonsinusoidal voltages and currents. In particular, definitions of the arithmetic and geometric apparent powers are discussed. It is shown that these two powers result in an erroneous value of power factor of unbalanced loads even if voltages and currents are sinusoidal. A reasoning that leads to a right selection of the apparent power definition is presented as well. The paper also presents the con-cept of the three-phase current decomposition into Currents’ Physical Components (CPC) and its application for power definitions and compensation in three-phase circuits. 

Andrzej SZROMBA  

        
The aim of the paper is to demonstrate how to use sampled method of control of a shunt active power filter to maintain invariable power of a supplying voltage source, even though the supplied load varies randomly. The definition by S. Fryze of load current components is used as a basis for the construction of a family of shunt active power filters. The distinctive property of these filters is maintaining non-deformed source current in every one individually considered period T. The main features of the family of filters are described in the first part of the paper, which is devoted to DC circuit. In the second part, the results are implemented to a single- and a three-phase circuit. Additionally, some new features, which may be applied only for AC circuit, are discussed in the second part. All the presented waveforms are obtained using computer simulation tools.              

Grzegorz BENYSEK 

This paper presents the fundamental properties and dependences describing the UPQC (Unified Power Quality Conditioner) arrangements. The UPQC devices simultaneously permit to fulfill the following functions: voltage and current harmonics compensation, network voltage and load current symmetrization as well as network voltage stabilization and power flow control. The selected results of the experimental investigations conducted on the small power laboratory model have been described. Applied method for DC link capacity selection was talked over in details and confirmed with experimental results. Results of experimental investigations, including operation of the UPQC arrangement in case of thyristor rectifier load were also introduced.

Daniel WOJCIECHOWSKI               
The paper presents structure and experimental results of the control system of the PWM rectifier with active filtering function. Proposed control system was designed for maximum filtering performance in steady state. This task is realized by predictive algorithms applied for both control as well as calculation of grid currents. Accuracy of these algorithms strongly depends on precise information about future samples of equivalent electromotive force of the grid, which is in general distorted and unbalanced. For this purpose, a novel estimator and predictor is proposed. The control of DC voltage is realized with application of variable gain PI controller. It ensures high dynamics in transient states and low gain for steady state oscillations of DC voltage. Proposed control system is AC voltages sensor less and has excellent active filtering performance, even at presence of grid voltage distortions.

 Vanya IGNATOVA, Pierre GRANJON, Seddik BACHA 

Applications for AC/DC/AC Power Electronic Interface  

This paper presents an analytical frequency-domain method for harmonics modeling and evaluation in power electronic systems. The considered system is described by a set of differential equations, which are converted in the frequency domain and presented in a matrix form. Indeed, currents and voltages are described in terms of Fourier series and arranged in a vector form. The passive elements and the switching functions are then represented by harmonic transfer matrices. The resolution of the matrix equations leads to theoretical time and frequency expressions of the system voltages and currents. This method is applied to a closed-loop three phase AC/DC/AC PWM converter. The control loop of the converter is modeled by additional equations. The spectra of the switching functions, necessary to build the corresponding harmonic transfer matrices, are calculated through a double Fourier series decomposition. The matrix equations are solved and the results are compared to those obtained by real measurements and Matlab/Simulink simulations.        

Adam KEMPSKI, Robert SMOLENSKI          
In this paper an analytical approach to decomposition of total phase EMI noises through algebraic calculations and the Fourier transform has been presented. Separating conducted EMI noise into different, common and differential mode (CM and DM) HF current components is important for a proper spectral analysis and application of EMI mitigation techniques. The results of calculations have been compared to EMI currents measured on the motor side of the PWM drive system. The proposed approach can be useful in comparative analysis of the influence of inverter control algorithms on spectra of CM currents in a given drive system.

Irena KOVÁČOVÁ, Dobroslav KOVÁČ         
The paper is dealing with some electromagnetic compatibility (EMC) problems of converters and inverters, which are utilized for feeding of electric machines and its analyzing by PSPICE program. The main attention is focused on implications of parasitic capacitance and capacitive coupling existence.          

Leszek SZYCHTA
The article defines the coefficient of the unit energy consumption of water pumping in pump group. Correct pump operation in pump group are described during cascade control, at variable rotational speeds and in the highest range of efficiency. A method of determining the unit energy consumption of water pumping for these control systems are defined at any daily demand and known pump H(Q) and efficiency curves are plotted at nominal rotational speed.

David SALTIVERI, Antoni ARIAS, Greg ASHER, Mark SUMNER, Pat WHEELER, Lee EMPRINGHAM, Cesar SILVA 
This paper investigates the influence of the power converter on the performance of Surface Mounted Permanent Magnet Synchronous Motor drives, which employ High Frequency voltage injection to achieve low and zero speed control.  Experimental results demonstrate the remarkable performance of the sensor less speed and position control employing the Matrix Converter and the contributions of the Space Modulation Profiling technique. The Matrix Converter has almost zero dead time, which means that behaves almost like an ideal power converter and achieves better results than the conventional Voltage Source Inverter. A comparison of the sensor less technique proposed using both converters is made.

Pavel NOVÁK, Jozef JANOŠČÍK, Dušan MEDVEĎ
The place of generation of technologic heat is important applied criteria for classification of electric heating. According to that, the direct heating is if the heat is generated directly in the heated material, or the indirect heating if material is heated indirectly by the heat generated in conversion element.  Possibilities of practical application of both methods are typical for resistant heating. Considering indirect heating, the charge is out of influence of electromagnetic field, this directly does not influence its temperature field. Temperature distribution in the charge volume depends only on its heat-physical properties and conditions of heat exchange on surface, i.e. thermo kinetic processes. Fourier´s equation is applied in field solution. Considering direct heating, temperature distribution in the charge volume is more complicated. It is conditioned by interaction of temperature and electromagnetic field which is generated by the current flowing in the charge. Solution of temperature field in directly heated charge must for that reason respect current density distribution on its cross-section, this leads to applying of heat conduction equation. We introduce its application for different types of temperature fields in the solid charge in this article. We present solution by two methods, results are presented in criteria (no dimensional) form.

Ladislav VARGA, Stanislav ILENIN, Vladimír CHLADNÝ
Paper is focused to mechanics calculation of overhead transmission lines. In first part of this paper is presented mathematical model for complex solution of overhead line mechanics in a plan. Non-level overhead line can be considered. The second part of paper deals with a solution method of the mechanics of overhead line conductors in three-dimensional space in non- level span. This method enables to define three-dimensional location, vector of mechanics stress of suspended line in optional point of line under combined load caused by the ice and the wind of optional direction.