Michał Krystkowiak

In this work, we present a three-phase diode bridge rectifier with a power line current close to a sinusoidal shape. To benefit from this approach, a solution called ‘current modulation’ is used in the DC link of the rectifier. The main advantage of this system is that the power supplied to the current modulation stage is only a small percentage of the entire power system, meaning that this solution is especially attractive in the case of high-output power systems, for example, for supplying electrical traction. The essential aspect of the current modulation stage is a wide-pass band power electronics controlled current source (VCCS), which is based on a dual-channel (interleaved) topology. The control algorithm for the current modulation stage also takes into consideration the impact of aliasing phenomena on the stability of the system, and uses a control method proposed by the authors. This work contains a general description of the operation of this rectifier and presents basics of operation for the current modulation stage. Selected results from both a simulation of the rectifier and an experimental model are included.

The article presents the solution of a power rectifier system dedicated to cooperating with an electric generator based on a special synchronous generator, which can be used in wind or water energy systems. In this generator, a pair of three-phase windings in a stator is utilized. One of the windings is connected in a star, and the second one is connected in a delta configuration. Two six-pulse uncontrolled (diode) rectifiers are included at the outputs of the windings. The rectifiers are coupled by a pulse transformer. The primary windings of this transformer are supplied by a power-electronics current source called a current modulator. With the help of this current modulator, the quasi-sinusoidal magnetomotive force (mmf) in the stator of the machine can be obtained. Additionally, to improve the efficiency of the described system, the low-power transistor rectifier, which is connected to the DC bus of the current modulator, has been used. With the help of this converter, it is possible to control and stabilize the voltage level in a DC circuit. It works, in this case, in inverter mode. The principle of working and elaborated control methods of the current modulator and the additional rectifier are presented. Selected results of simulation and experimental tests are also presented.

W artykule zaprezentowano rozwiązania umożliwiające polepszenie jakości przekształcania energii w tyrystorowych złożonych układach prostownikowych. W pierwszej części opisano rozwiązanie bazujące na zastosowaniu w obwodzie stałoprądowym modulatora napięcia. Odznacza się ono jednak dość istotnymi wadami. Dlatego też przedstawiono inną metodę zmniejszenia niekorzystnego oddziaływania na sieć zasilającą tych układów poprzez wykorzystanie koncepcji wykorzystującej modulację prądu, stosowaną dotychczas w prostownikach diodowych. Zaprezentowano również wybrane wyniki przeprowadzonych badań symulacyjnych.

The article presents various concepts of three-phase power rectifiers with improved quality of converted electric power. This effect is obtained by modulating the currents in the DC output circuits of the rectifiers by means of power electronics controlled voltage or current sources, working as a so-called voltage or current modulators. For further quality improvement of the grid currents of the analyzed systems, it was proposed to use an additional controlled current source connected in parallel to the DC load, hereinafter referred to as a supporting system. The original elaborated method of controlling this source (supporting system) was presented. The main goal of the work was to propose a solution for an effective method of improving the quality of energy conversion in rectifier systems, especially high power ones, by using controlled current sources in DC circuits, operating as the power electronics current modulator and the supporting system.

In this work, the concept of an energy conversion system for wind turbines based on the modified permanent magnet synchronous generator (PMSG) is presented. In the generator, a pair of three-phase windings is used, one of which is connected in a “star” and the second in a “delta” configuration. At the outputs of both windings, two six-pulse uncontrolled (diode) rectifiers are included. These rectifiers are mutually coupled by a specially designed pulse transformer, whose primary winding is powered by the power electronics converter—the so-called “current modulator”—which, in this case, operates as a magnetic flux modulator, in the generator. The modulator provides a quasi-sinusoidal magnetomotive force (mmf) in the stator of the machine. The whole system is connected to the power grid via a dedicated voltage source inverter (VSI) converter. The main objective of the elaborated solution is to provide high efficiency conversion of mechanical (wind) energy into electricity by means of a relatively simple electrical system.

The article presents the solution of the power supply with a tunable inductive filter. The power supply is characterized additionally by the possibility of compensation of both reactive power and deformation power, generated by other loads connected to the same power grid node. The passive filter with tuned inductance is used in the system for obtaining a high dynamics of the input current of the power supply. This one significantly improves the quality of compensation process. The article presents the principles of the system operation as well as the structure of the control circuits and the power stage of the system. Selected results of the tests of the system simulation model, for various operating conditions, are presented too. (Power supply with tunable induction filter).

In the article the elaborated simulation and experimental models of the power electronics UPS converter with the possibility of active parallel compensation were described. The power circuits, control algorithms and the principle of working of presented UPS structure were presented. Also the chosen simulation and experimental results were analyzed.

Purpose: The purpose of this paper is to present the electromagnetic phenomena in permanent magnet synchronous generator (PMSG) suited for wind turbines with uniquely designed system of two windings. The machine’s windings allow for application of a reliable and low-cost power electronic converter. Design/methodology/approach: The 2D field-circuit model has been developed and used in comparative analysis between reference design PMSG with concentrated three-phase winding and two-windings PMSG to facilitate application of a low-cost and reliable AC/DC power electronic converter. The paper focuses on comparison of radial force density, core losses and torque waveforms in the proposed and reference machine with sinusoidal load currents. Findings: The usefulness of the proposed approach for analysis of the two-winding PMSG performance by means of the field-circuit model has been proved. The obtained results show practically no drop off of performance of proposed machine in relation to reference PMSG. Moreover, it has been shown that both machines are characterized by the same level of radial force density. Therefore, the lower cost and reliable power electronic converts can be applied in the wind power energy systems (WPES) by slightly more complex design of the stator winding. Originality/value: The proposed 2D field-circuit numerical model makes it possible to analyze the performance of the star-delta winding PMSG dedicated to be loaded by the AC to DC converter specially designed to achieve high reliability and efficiency of the system. Presented comparative studies on generator performance show that proposed modulated synchronous flux generator characterize with the same output torque at given supply current and core losses level like conventional PMSG with sinusoidal load.

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In the paper the 3-phase power diode rectifier system with quasi-sinusoidal input (power grid) current is presented. In order to benefit from it, the current modulation in the DC circuit of a rectifier is used. The essential part of the current modulator is the wide-band power electronics controlled current source based on a multi-channel converter. The control algorithm of the current modulator respects impact of aliasing phenomena at system stability by using the method proposed by the authors. The paper includes the rectifier system description and rules of operation of the current modulator. Also, some results of research on both the rectifier simulation model and the laboratory prototype of a current modulator are presented.