No abstract

No abstract

Abstract. This paper presents an analysis of the properties of pulse width modulator with a single (symmetrical regular sampled PWM) and double (asymmetrical regular sampled PWM) control sampling of the input signal (low-frequency control input wave) in presence of a triangular auxiliary signal. In this paper, a comparison of the characteristics of these modulators used in the control system with a linear proportional controller is presented. The article provides the relations derived for the maximum amplification of regulators for which the control system operates stably. Analysis results have been confirmed by simulation and experimental studies of a commercial active filter installed in an industrial plant. Simulation studies show an increase of the critical proportional controller gain with symmetrical regular sampled PWM with a doubled number of samples in the period of the triangular auxiliary signal for which the control system is stable. Also, the analysis included in this article demonstrates the possibility of increasing the value of the gain of the proportional controller in a closed system with asymmetrical regular sampled PWM. Publications [8][9][10][11][12][13][14] devoted to applications in power electronics systems with the asymmetrical regular sampled PWM are not related to control systems with a proportional controller. From the point of view of the topics covered in this article, the most interesting paper is publication [15]. This paper addresses the digital control system with asymmetrical regular sampled PWM with different types of controllers, but the issues critical to the gain of the proportional controller addressed in the present article are not discussed.One of the objectives of the work presented is to compare the dynamic and static properties of the control system with a proportional controller and symmetrical regular sampled or asymmetrical regular sampled PWM.Carried out in this article is an analysis taking into account the time between the instant of measurement of the controlled value and the actual determination of the magnitude of the sampled reference (PWM computation delay [15]).Control system with proportional controller has non-zero value of disturbance error. From the point of view of minimizing the disturbance errors and the reducing the time of decay of transient component of this error advantages of asymmetrical regular sampled PWM compared to the symmetrical regular sampled PWM manifest themselves only under the condition of an appropriately small value of the PWM computation delay.The article also describes a mechanism allowing for elimination of the impact of this error on the output current of the APF. This is a feature of APF with supervisory system of DC link voltage which allows the use of output current proportional controller.

Abstract. This paper presents an analysis allowing for the determination of the differential equation describing the circuit of the active filter inverter output current control with an additional measurement of input voltage. The resulting equation allows to determine the conditions that ensure stable operation of the filter with the load in form of a resonant LC circuit. Analysis results were confirmed by computer simulation and experimental studies of commercial active filter.

Abstract. This paper deals with performance of the 50 kVA three-phase converter built with switches based on SiC MOSFET and anti-parallel Schottky diodes. In contrast to popular IGBT converters, a negative switch current is capable of flowing through the reverse conducting transistor, which results in different distribution of power losses among the devices. Thus, equations describing the conduction power losses of the transistor and diode are improved and verified by means of circuit simulations in Saber. Moreover, a comparison of power losses calculated with the use of standard and new equations is also shown. Total power losses in three SiC MOSFET modules of a 50 kVA converter operating at 20 kHz are up to 30% lower when reverse conduction is taken into account. This shows the importance of the discussed problem and proves that much better accuracy in the estimation of power losses and junction temperatures of SiC devices may be obtained with the proposed approach.

This article provides formulae to determine the root mean square (rms) value of a capacitor current in an inductive-capacitive-inductive (LCL) filter used in a parallel active power filter (PAPF) circuit. The article presents an analysis of three components of the capacitor current: a component forced by the usually distorted voltage of the grid; a component forced by the nonlinear load current harmonics and harmonics in the output current of the PAPF that compensates them (a novel aspect presented in this document); and a component forced by the inverters of the PAPF containing carrier and sideband harmonics. The article also presents formulae for determining the rms value of current harmonics in dc-link capacitors forced by the ripple of the ac output current without load of the filter inverters (also novel to this document). The results of the analysis have been confirmed by simulation and experimental research of a commercial active filter consisting of two parallel interleaved voltage inverters. Elements of the LCL filter of the PAPF have been selected according to dependencies available in scientific and technical literature. In addition, the formulae presented in the article are used to verify the correctness of selection of capacitors from the point of view of their catalogue acceptable rms value of capacitor current.

No abstract

Aby zrealizować ideę komunikacji kolejowo-tramwajowej, niezbędne jest posiadanie pojazdu trakcyjnego, który będzie mógł być zasilany z sieci kolejowej 3300Vdc i typowej sieci tramwajowej 600Vdc. Jednym z rozwiązań jest zbudowanie przekształtnika obniżającego wysokie napięcie. W artykule przedstawiono projekt i wyniki badań laboratoryjnych przekształtnika rezonansowego z transformatorem toroidalnym. Ze względu na zakres napięcia wejściowego 3300Vdc zastosowano konfigurację układu półmostka z szeregowym obwodem rezonansowym po stronie pierwotnej transformatora. Praca w trybie rezonansowym umożliwia zwiększenie częstotliwości pracy układu, dzięki temu mogą być mniejsze wymiary i masa transformatora. Głównym zastosowaniem przekształtnika ma być zasilanie układu napędowego (falownikowego) w dwusystemowym pojeździe tramwajowokolejowym 3000Vdc/600Vdc. Do tego celu został specjalnie zaprojektowany i wykonany transformator z nanokrystalicznym rdzeniem toroidalnym o mocy czynnej 120kW. Artykuł zawiera wyniki badań sprawności przekształtnika rezonansowego.