Wyniki 1-10 spośród 10 dla zapytania: authorDesc:"Andrzej TOBOŁA"

A time-varying capacitance: control function of active power filters

Czytaj za darmo! »

This paper proposes new fixed switching frequency control techniques for power active filters. The method is based on an auxiliary capacitance function. This function is equivalent to time-varying capacitance. Such capacitance function can be computed when reference signal is known. The fixed switching frequency control techniques for PWM voltage source inverter can be easy obtained when the aux[...]

Sliding Mode Observer for active power filters

Czytaj za darmo! »

This paper proposes a new method of equivalent source voltage estimation for power active filters. The performance of fixed switching frequency controllers is constrained to the accuracy of the plant model as well as the accuracy of the reference signal and disturbance predictions. The error of the equivalent source voltage estimation can be treated as a unknown disturbance. The proposed sliding mode observer enables one to track the changing of supplying system voltage. The numerical example of sliding mode observer is presented in the paper. The control algorithm of the presented active power filter is based on the time-varying model. Because the switched structure of active power filter is substituted for timevarying system the observer is quite simple. The computer simulation show[...]

Average Time-varying Models of Active Power Filters

Czytaj za darmo! »

The paper presents models of the active power filter based on the of voltage source converter structure. For the single-phase circuit two models are presented - transformer model with varying turns-ratio and time-varying capacitance model. The models are results of current and voltage averaging. The relation between two models is formulated. The numerical examples illustrate time- varying parameters of considered models. Streszczenie. W pracy przedstawiono modele aktywnego filtru energetycznego o strukturze przekształtnika napięcia. Dla układu jednofazowego przedstawiono dwa ciągłe modele - model z transformatorem o zmiennej przekładni i model ze zmienną pojemnością. Modele te są wynikiem uśredniania prądów i napięć w przedziale przedziału przełączania. Pokazano związki między funkcj[...]

Ripple estimation in active power filters

Czytaj za darmo! »

The paper presents the analytical method of ripple estimation in active power filters. The method is based on an average model of PWM voltage source inverter. The formulae for the ripple magnitude are derived for single-phase and three-phase three-leg structures. Numerical examples for filters generating third and fifth order harmonics are presented. The example with reactive component of fundamental harmonic is considered as well. Streszczenie. Przedstawiono analityczną metodę estymacji tętnienia prądu wynikającego z przełączeń obwodu w aktywnych filtrach energetycznych. Metoda opiera się na uśrednionych modelach z modulacją PWM. Odpowiednie formuły analityczne zostały opracowane dla układu jednofazowego i trójfazowego. Wykonano obliczenia dla układu generującego trzecią i piątą harmoniczną oraz układu generującego składową bierną harmonicznej podstawowej. (Estymacja tętnień prądu w aktywnych filtrach energetycznych). Keywords: averaging techniques for switching circuits, current ripple, active power filters Słowa kluczowe: metoda uśredniania układów przełączanych, tętnienia prądu, aktywne filtry energetyczne. . Introduction An important feature of power electronic circuits working in switching scheme is a ripple effect. Switching frequency errors are undesirable effects always accompanying these techniques. Ripple errors are eliminated with the use of additional filters. Properly chosen switching algorithms can minimize the ripple effects [1]. The magnitude of current ripples can be computed by simulation of a specific PWM realisation. More general information can be obtained from analytical formulae. Such formulae can be derived when an average model of PWM inverter is employed. The averaging approximates the discontinuous system by a time-continuous model. Average models simplify analysis, make easier to understand the system’s behaviour, speed up simulation and can be used for control and design purposes. The averaging [...]

Ripple Analysis for Three-Phase Four-Leg Active Power Filters

Czytaj za darmo! »

The paper presents the analytical method of ripple estimation in active power filters. The method is based on an average model of PWM voltage source inverter. The formulae for the ripple magnitude are derived for three-phase four-leg structures. The numerical example for filters generating third order harmonics is presented. Streszczenie. Przedstawiono analityczną metodę estymacji tętnienia prądu wynikającego z przełączeń obwodu w aktywnych filtrach energetycznych. Metoda opiera się na uśrednionych modelach z modulacją PWM. Odpowiednie formuły analityczne zostały opracowane dla układu trójfazowego czteroprzewodowego. Wykonano obliczenia dla układu generującego trzecią harmoniczną prądu. (Analiza tętnień prądu w trójfazowych czteroprzewodowych strukturach aktywnych filtrów energetycznych). Keywords: averaging techniques for switching circuits, current ripple, active power filters. Słowa kluczowe: metoda uśredniania układów przełączanych, tętnienia prądu, aktywne filtry energetyczne. Introduction The wide use of consumer electronics and power electronic based products in industries causes current and voltage pollution in power distribution system. Active power filters have been developed to clean harmonics from power supply. The main components of active power filters are voltage source inverters. An important feature of power electronic circuits working in switching scheme is a ripple effect. Switching frequency errors are undesirable effects always accompanying these techniques [1]. The magnitude of current ripples can be computed by simulation of a specific PWM realisation. More general information can be obtained from analytical formulae. Such formulae can be derived when an average model of PWM inverter is employed. Average models simplify analysis and speed up simulation. The analytical method of ripple estimation in single-phase and threephase three-wire structures of active power filters is presented in [3]. To compensate t[...]

Voltage harmonic damping with the framework based on Kalman approach DOI:10.15199/48.2017.10.29

Czytaj za darmo! »

Voltage distortion resulting from the harmonic currents produced by power electronic equipment has become a serious problem [1,2]. Generally, individual low-power and high-power consumers are responsible for limiting distortion at the end of line feeder, while electric utilities are responsible for limiting voltage distortion at the point of common coupling in distribution systems. Most of the previous works on harmonic compensation of individual loads are based on current-controlled methods [3,4,5]. The shunt active filters based on voltage detection at the points of compensator installation seem to be more flexible to the current-controlled compensators. The voltage-controlled method for a shunt active power filter is illustrated in Fig. 1. The symbol of current controlled source in this figure means a compensator. The system is divided into two subsystems, the active power filter is placed between two subsystems. The subsystems are composed of the sinusoidal voltage sources and linear RLC elements representing the transmission lines and nonlinear loads (Fig. 1). Fig. 1. General structure of voltage-controlled single-phase shunt active filter The voltage-controlled method, which does not require the load current, detects reference signal from voltage waveform at the point of filter installation (PCC) , and then injects a compensating current. The voltage-controlled method proposed by Akagi [1] forms a feedback control loop. The filter detects voltage harmonics at the point of filter installation, and then injects a compensating current as follows ic  G h , where G is a control gain. The active filter behaves like resistor equal for all harmonic except the fundamental frequency. For fundamental harmonic it behaves as infinite resistance. Time and phase delay in active controller deteriorates harmonic damping and causes instability. Iteration method of voltage harmonic detection is proposed in [6]. The met[...]

Control of dc capacitor voltage in active power filters

Czytaj za darmo! »

The paper deals with the three-phase three-wire shunt active power filter. The analysis of capacitor voltage in such compensator is presented. It is shown that fast component of the capacitor voltage is unavoidable. The slow component should be stabilized on the desired level. The results of SIMULINK computation for chosen structures of the compensator are presented in the paper. Two controllers of capacitor voltage are treated - PI controller and fuzzy logic controller. Streszczenie. W pracy zaprezentowano analizę napięcia kondensatora w trójfazowym aktywnym filtrze energetycznym w układzie trójprzewodowym. Pokazano, że obecność składowej szybkiej napięcia kondensatora jest niezbędna, gdyż wynika ona z istoty wymiany energii w takim układzie. Składowa wolna napięcia powinna być stabilizowana na założonym poziomie. Przedstawiono przykładowe wyniki obliczeń z zastosowaniem programu SIMULINK dla wybranych struktur kompensatora. Zbadano dwa rodzaje regulatora napięcia kondensatora - regulator PI oraz regulator rozmyty. (Sterowanie napięcia kondensatora w energetycznych filtrach aktywnych) Keywords: active power filters, dc capacitor voltage, dc voltage controller. Słowa kluczowe: energetyczne filtry aktywne, napięcie kondensatora dc, regulatory napięcia dc Introduction The three-phase three-wire shunt active filter using three-leg voltage source converter (Fig. 1) is considered in the paper. Fig. 1. Structure of three-phase three-leg active filter Active filtering is one of the most challenging applications for digital current controls. But proper design of passive components of the active power filters (APF) also plays important role [1]. The value of d[...]

Feedback control versus optimization method for voltage harmonic damping DOI:10.12915/pe.2014.04.058

Czytaj za darmo! »

Two methods of voltage harmonic elimination are compared - the feedback control method and optimisation approach. The first method has been presented in the literature, the second is proposed in the paper. The results of numerical experiments comparing the efficiency of both methods are presented and compared. Streszczenie. Porównano dwie metody eliminacji harmonicznych napięcia w sieci elektrycznej - metodę sprzężenia zwrotnego i metodę optymalizacyjną. Pierwsza metoda jest opisana w literaturze druga jest proponowana w prezentowanej pracy. Przedstawiono wyniki eksperymentów numerycznych porównujących skuteczność redukcji wyższych harmonicznych przy użyciu obu metod. (Porównanie metody sprzężenia zwrotnego i metody optymalizacyjnej eliminacji harmonicznych napięcia). Keywords: active power filters, detection of voltage harmonics, feedback loop damping, optimization method. Słowa kluczowe: energetyczne filtry aktywne, eliminacja harmonicznych napięcia, sprzężenie zwrotne, optymalizacja. doi:10.12915/pe.2014.04.58 Introduction Voltage distortion resulting from the harmonic currents produced by power electronic equipment has become a serious problem to be solved [1]. The fundamental change is caused by the power electronic based distributed generation [2,3]. Properly controlled distributed generation grid can improve the power quality. The converters interfacing wind or photovoltaic plants with the system can play a similar role as the active power filters. In general, individual low-power and high-power consumers are responsible for limiting distortion at the end of the line feeder, while electric utilities are responsible for limiting voltage distortion at the point of common coupling in the distribution systems. Most of the previous works concerning harmonic compensation of individual loads are based on the current-controlled method. The shunt active filter based on voltage detection at the point of compensator installation and [...]

Synchronization of the iterative process for voltage harmonic mitigation DOI:10.15199/48.2019.06.18

Czytaj za darmo! »

The control of active power filters can be divided into three groups: control based on instantaneous power, control based on current, and control based on voltage measurements. The shunt active filters based on voltage detection at the points of compensator installation seem to be more flexible then current-controlled compensators [1]. The power necessary for active filtering can be maintained at a very low level with an accurate design of control and of the passive components. For example, the power usage of the active filter can be about 1.5% of the nominal value. The voltage-controlled method, which does not require the knowledge of the load current, determines the reference signal basing only on voltage waveform observations at the point of filter installation (PCC) and then injects the proper compensating current. Such filters should be installed in the power system rather not by consumers, but by the grid operator. The voltage-controlled method proposed in [2] forms a feedback control loop. The filter detects voltage harmonics at the point of filter installation, and then injects a compensating current. The active filter forms a short-cut for all harmonic except of the fundamental frequency. For fundamental harmonics it forms the open circuit. This method is fast as it is based on instantaneous voltage and current observations. However time delays (phase shifts) in active controller deteriorate harmonics damping and can lead to filter instability. The modifications presented in [3] are based on the assumption that all harmonics of the compensator current should be orthogonal to voltage harmonics (phase shift of π/2) as the grid impedance has dominating inductive character. More information on system parameters can be obtained from the experiments proposed in [4,5]. The vector control is the another common approach to harmonics compensation. With the synchronous reference frame implemented in grid-tie converters[...]

Możliwości wytwarzania biogazu w procesie fermentacji metanowej wysłodków buraczanych Część II: Fermentacja półciągła wysłodków buraczanych

Czytaj za darmo! »

W artykule przedstawiono wyniki badań półciągłej fermentacji metanowej zakiszonych wysłodków buraczanych. Badania pole- gały na zasilaniu fermentora nieprzefermentowaną biomasą jeden raz na dobę. Takie same ilości przefermentowanej biomasy były odprowadzane codziennie z fermentora. Proces półciągłej fermentacji metanowej wysłodków może być prowadzony z optymalnym efektem przy obciążeniu wynoszą- cym do 2,0 g s.m./dm 3 × d oraz przy zachowaniu temperatury 37ºC ±1ºC, regulacji odczynu do ≥6,8 pH i zaszczepieniu reaktora materiałem biologicznym bogatym w bakterie metanowe. Stwierdzono, że w takich warunkach redukcja substancji organicznej będzie kształtowała się na poziomie 63,5%. Przefermen- towane wysłodki będą zawierały w suchej masie 32,9% substancji organicznych. Ilość wydzielanego biogazu w odniesieniu do jednostki pojemności reaktora wyniesie 0,49 dm 3 /dm 3 × d, a w przeliczeniu na jednostkę rozkładanej substancji organicznej 0,40 dm 3 /g s.m.o. This paper presents test results for semi-continuous methane fermentation of ensilaged beet pulp. The test consisted in sup- plying unfermented biomass to the fermenter once every 24 h. The same amount of fermented biomass was removed every day from the fermenter. The semi-continuous methane fermentation process can be carried out with an optimum result with the load up to 2.0 g dry mass/dm 3 × d and at[...]

 Strona 1