Wyniki 1-7 spośród 7 dla zapytania: authorDesc:"Sardar Muhammad GULFAM"

Design and Analysis of Odd-Harmonic Repetitive Control for Three-Phase Grid Connected Voltage Source Inverter

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This paper presents a novel design and analysis of an odd-harmonic repetitive control (ORC) for a two-level three-phase grid connected voltage source inverter. An LCL filter between the inverter and the grid is used to attenuate high frequency PWM switching harmonics. The controller lowers the memory requirement, compared to a conventional repetitive controller. The control scheme contains a traditional conventional tracking controller with a dual loop feedback system, and a zero-phase noncasual filter with add-on ORC. Our analysis and simulation results suggest that the proposed control scheme is able to provide high quality output current (THD=1.8 %) even in worst case scenario. Streszczenie. W artykule przedstawiono nową strategię sterowania ORC (ang. Odd-harmonic Repetitive Control) dla trójfazowego, dwupoziomowego sieciowego przekształtnika napięcia. Dodatkowo wykorzystano filtr wyjściowy LCL. Algorytm redukuje ilość wymaganej pamięci. Jego struktura opiera się na sterowniku nadążnym z podwójną pętlą sprzężenia zwrotnego, filtrze o zerowym przesunięciu fazy oraz ORC. Analiza i symulacje wykazały, że proponowane sterowanie może zapewnić wysokiej jakości prąd (THD=1,8%). (Opracowanie i analiza algorytmu ORC dla trójfazowego przekształtnika sieciowego). Keywords: current control, pulse width modulation converter, system analysis and design, total harmonic distortion. Słowa kluczowe: sterowanie prądem, przekształtnik PWM, projekt i analiza systemu, THD. Introduction Many renewable and conventional energy sources generate DC/AC power at inconvenient frequencies. A pulse width modulated (PWM) voltage source inverter as shown in Fig.1 is typically used to integrate the distributed generation plant into the grid. The quality of the output current of inverter introduced into the grid must conform to standards and regulations that define the total harmonic distortion (THD) limits [1].This is attained by a mixture of output filter and adequa[...]

DSP Based Hardware Implementation of Repetitive Current Controller for Interleaved Grid Connected Inverter

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The performance of the repetitive controller (RC) for classical inverters (e.g. two-level LCL filter based inverter) can decline if the system bandwidth is not sufficient enough due to much larger LCL filter component values. The novel interleaved inverters can provide higher bandwidth than the classical inverters because of low filter values. This paper reflects upon the analysis and hardware implementation of the RC for interleaved inverter using DSP. High quality (very low THD) output current is demonstrated through simulation and experimental results. Streszczenie. W artykule przedstawiono analizę i implementację na DSP sterowania powtarzalnego dla badanego falownika typu interleaved. Przedstawione wyniki badań symulacyjnych, pokazują wysoką jakość (niskie THD) prądu wyjściowego przekształtnika. (Implementacja sterowania powtarzalnego na DSP dla przekształtnika sieciowego typu interleaved). Keywords: Interleaved inverter, total harmonic distortion (THD), repetitive control (RC), digital signal processor (DSP) Słowa kluczowe: falownik interleaved, THD, sterowanie powtarzalne, DSP. Introduction The power electronic inverters have been widely employed as the interface between distributed generators and the grid. There exist different types of power electronic inverters for interfacing with the grid [1]. The most common is the two-level bridge inverter. However, there is always requirement of improved efficiency and low cost. This has encouraged researchers to look into alternative topologies. Many multilevel inverters have been proposed. These inverters have the advantage of reducing the voltage step changes at the expense of increased complexity and cost of the power electronics and control components. An alternative to the multilevel inverter is to use an interleaved inverter topology (as shown in Fig. 1), which in effect comprises several low power, high frequency, multilevel bridge inverters connected in parallel. Since, there [...]

Detection of ECG T-wave Alternans Using Maxima of Continuous-Time Wavelet Transform Ridges

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Prognostic utility of microvolt T-wave alternans (TWA) has been established since its clinical acceptance as marker for malignant ventricular arrhythmias, leading to sudden cardiac death. Accurate detection of TWA from surface ECG is a challenge because of invisible nature of the phenomenon. A novel TWA detection scheme based upon analysis of continuous time wavelet ridges (CTWR) of consecutive ventricular repolarization complexes is presented. The CTWR is computed using maxima of wavelet energy coefficients of continuous wavelet transform. Variety of simulated alternans waveforms, wavelet functions, frequency bands and noise levels are used to test the algorithm. The study concludes that CTWR can successfully characterize the alternation of cardiac repolarization and detect TWA phenomenon. Streszczenie. Diagnostyka sygnału TWA odgrywa du˙za˛ role˛ w badaniach jako marker arytmii powoduja˛cej zawał serca. Sygnał TWA jest wykrywany jako składowa sygnału elektrokardiogramu. W artykule opisano wykorzystanie cia˛głej transformaty falkowej do analizy tego sygnału. (Detekcja składowej TWA sygnału EKG bazuja˛ca na wykorzystaniu cia˛głej transformaty falkowej) Keywords: Continuous-Time Wavelet Transform, Detection, Electrocardiography (ECG), T-wave Alternans Słowa kluczowe: transformata falkowa, elektrokardiogram, sygnał TWA Introduction Electrocardiography (ECG) is an important clinical tool for diagnosis of cardiac diseases. It is commonly measured by placing the surface electrodes on a subject’s chest and recording the cardiac cellular potential variations. The measured voltages, graphically plotted as a function of time, represent sequential depolarization (P-wave and QRS complex) and repolarization (T-wave) of cardiac chambers. A single such heart beat is shown in Fig. 1(a). 0 0.1 0.2 0.3 0.4 0.5 0.6 -1 0 1 2 (a) ECG (mV) 0 1 2 3 4 5 -1 0 1 2 (b) ECG (mV) 0 1 2 3 4 5 -1 0 1 2 (c) time(sec) ECG (mv) P Q R S T[...]

Vertical Handover Triggering Condition Estimation for a Mobile Node Moving Out of a WiFi Cell

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In this work we estimate the handover trigger condition for a mobile node moving out of a WLAN cell roaming in a heterogeneous network environment by performing vertical handover using an end-to-end handover scheme. Determining the characteristics of the handover latency of the employed handover scheme we estimate the appropriate handover triggering instance so as to maximize the WiFi usage but limit the handover failure. The remaining time within the WiFi cell is determined through successive changes in received signal strength as the mobile node moves out of the WiFi coverage cell. Streszczenie. W pracy określono warunki trigera przełączania (handover) w mobilnym węźle komórki WLAN w środowisku sieci niejednorodnej. Określając opóźnienie przełączania określano sytuację przełączania tak aby maksymalizować użycie sieci WiFi ale ograniczać błąd przełączania. (Określanie warunków trigera przełączania typu handover w mobilnym węźle komórki WiFi) Keywords: Vertical handover, handover triggering condition estimation, handover failure probability. Słowa kluczowe: przełączanie - handover, trigger Introduction Determination of optimum handover initiation time is particularly of prime importance in the context of optimization of vertical handover from the WiFi network, which is characterized by fast and low cost of access but limited coverage range. Desire to maximize its usage is obvious, however, handover triggering close to the boundary region may lead to handover failure. Delaying the handover trigger for a moving out mobile node increases the probability of handover failure due to insufficient time for handover completion. For a given probability of handover failure the instance of handover trigger is estimated. In this work we use a geometrical model for handover triggering condition estimation. This work aims to estimate the handover triggering condition of the mobile node using an end-to-end vertical handover scheme. Geometrical an[...]

Estimation of Baseline Wander Characteristics in ECG Signals Using Adaptive Transversal Filter and Lomb's Periodogram Analysis

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A new technique is proposed to estimate the frequency and amplitude of baseline wander in ECG signals. The estimation has been performed in two stages. In the first stage, a QRS detector detects R peaks and signal samples between consecutive R peaks are passed through a weighted average adaptive filter. The cut-off frequency and order of the filter depends upon the time domain characteristics of the input samples and is automatically updated for each RR interval. In the second stage, Lomb’s periodogram is utilized to analyse the frequency response of the resultant unevenly sampled time series for estimating the baseline frequencies. These frequencies are then used to demodulate the signal for estimation of respective amplitudes. Results have been obtained using synthetic ECG signals with artificially introduced baseline wander containing single or multiple frequencies. The performance of the technique is evaluated by extracting baseline wander through three standard techniques and comparing the estimation errors. Streszczenie. W artykule opisano propozycje estymatora cz˛estotliwosci i amplitudy wahan osi podstawy dla sygnałów w badaniu EKG. Estymacja przebiega w dwóch etapach. Najpierw detektor QRS wykrywa impulsy R, a próbki sygnałów poddawane sa˛ filtracji w filtrze adaptacyjnym. W drugim kroku, korzystaja˛c z periodogramu Lomb’a, analizowana jest odpowiedz cze˛stotliwosciowa, be˛da˛ca w postaci nierównomiernie pobieranych próbek. Tym sposobem uzyskuje si ˛e estymacj ˛e cz˛estotliwosci odniesienia. Działanie algorytmu poddano weryfikacji na bazie symulowanych sygnałów EKG i porównano z trzema standardowymi technikami. (Estymacja charakterystyki przemieszczenia osi podstawy dla sygnałów EKG z wykorzystaniem filtru adaptacyjnego poprzecznego i analizy periodogramem Lomb’a). Keywords: Electrocardiogram, baseline wander, ECG preprocessing, estimation Słowa kluczowe: elektrokardiogram, w˛edrowanie osi podstawy, EKG, przetwarza[...]

The Q-Best Spreading Sequences for Low-Complexity DS-CDMA IEEE 802.15 UltraWideBand Systems in Dense Multipath Channels

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This paper presents an analysis for the selection of Q-Best spreading sequences of the synchronous Direct Sequence Code Division Multiple Access (DS-CDMA) UltraWideBand (UWB) system on the uplink using joint detection. It is shown that the time-domain cross correlation function between the spreading sequences is a prime interference measure for the synchronous DS-CDMA UWB users. Therefore auto and cross correlation funcitons of the spreading sequences, along with UWB IEEE 802.15 channel characteristics are amalgamated to obtain minimum Bit Error Rate (BER), using low complexity correlation joint detection scheme. Some well known classes of length Q sequences, such as m, Gold, Walsh and Random sequences are evaluated with respect to the aforementioned basic criteria. Explicitly, the performance of each sequence with length Q is shown in high Inter-Symbol Interference (ISI) and Multiple Access Interference (MAI) environment produced by dense multipath and multiuser. Streszczenie. W artykule przedstawiono analiz˛e metod rozpraszania widma z wykorzystaniem detekcji poła˛czen, dla metody doste˛powej DS-CDMA w poła˛czeniu z satelita˛ w systemie UltraWideBand. Wykazano, z˙e wyznaczenie funkcji korelacji przejscia dziedziny czasu mie˛dzy sekwencjami rozpraszania powinno stanowic główny czynnik pomiarowy dla u˙zytkowników systemu DS-CDMA UWB. W badaniach wykorzystano najlepiej znane klasy o długosci sekwencji Q (Gold, Walsh, Random, m). Ich działanie sprawdzono w ´srodowisku ISI oraz MAI stworzonym przez g˛esty zbiór wielu scie˙zek i wielu u˙zytkowników. (Sekwencja rozpraszania Q-Best w systemie DS-CDMA UWB IEEE 802.15 w kanałach wieloscie˙zkowych) Keywords: Spreading Sequences, DS CDMA, UWB, Dense Multipath Słowa kluczowe: sekwencja rozpraszania, DS-CDMA, UWB, spójna wielodro˙znosc. Introduction The Federal Communications Commission’s (FCC) ruling released the band spanning from 3.1 to 10.6 GHz in the USA for UltraWideBand UWB forms the basi[...]

Performance of Time Hopping Impulse Radio in Ultrawideband Propagation Channels: Implications of UWB and Diversity Order Selection

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In this treatise, we quantify the effects of the UltraWideBand (UWB) on Time Hopping (TH) Impulse Radio (IR) operating in UWB propagation channels environment in terms of bandwidth utilization through diversity order selection. We select L strongest MultiPath Components (MPC) from Nr resolvable MPCs using Maximal Ratio Combining (MRC) in order to achieve maximum performance gain in single and full load scenarios. Three classical detectors have being used for analysis purposes named Correlation (Corr), Zero Forcing Detector (ZFD) and Minimum Mean Square Error (MMSE). Our results suggest that the diversity order L of 20 achieves maximum gain of 18dB and 12dB in single and full load Nu of 63 users scenarios, having spreading factor Ns of 63 over no diversity configuration. Hence, MPCs with delays greater than the TH chip time Tc are resolved by synchronization with the initial path of the received signal gives maximum performance gain. Streszczenie. W artykule przedstawiono wyniki analizy dotycza.cej dzia.ania techniki Time Hopping Impulse Radio, zastosowanej w komunikacji Ultra WideBand, pod ka.tem stopnia wykorzystania doste.pnej przepustowosci. W analizie zastosowano trzy typy detektorow: Corr, ZFD, MMSE. Wyniki badan wskazuja., z.e gdy komponenty wielosciez.kowe o opoznieniach wie.kszych niz. okres Time Hopping sa. synchronizowane z pocza.tkiem odbieranego sygna.u, osia.gana jest maksymalna efektywnosc dzia.ania. (Dzia.anie techniki Time Hopping Impulse Radio w komunikacji Ultra Wide-Band . zastosowanie UWB oraz doboru stopnia ro.znorodnosci). Keywords: UWB, Diversity Order, Time Hopping, Impulse Radio S.owa kluczowe: UWB, stopien ro.znorodnosci, Time Hopping, Impulse Radio. Introduction UltraWideBand (UWB) radio communicates with baseband pulses of very short duration, typically on the order of a nanosecond, thereby spreading the energy of the radio signal very thinly (about a few ?ĘW per MHz) from near DC to a few Gigahertz. Because o[...]

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