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Critical Conduction Mode (CRM) Flyback APFCs is widely used in High Brightness Light Emitting Diodes (HB-LEDs) driver. But with high input voltage or light load, its line current distortion deteriorates because of the peak distortion. In this paper, an improved control strategy is introduced to solve this problem. It is realized by the injection of sin2θ component to primary reference current. Nonetheless,...
Based on PSCAD/EMTDC, the authors build a harmonic analysis model for a bi-pole dual 12-pulse ±1000kV Ultra-High Voltage Direct Current (UHVDC) converter and the interconnected AC system. The control strategy for UHVDC employs the current margin control from CIGRE HVDC Benchmark. The AC system includes the equipments above 500kV and the equivalent circuit under 500kV. The harmonic interaction of DC...
A method that can be used in the calculation of harmonic of MEDC transmission system is described in this paper. This is based on the advanced switching function model of MIDC converters in the DC side and the network topology in the AC side of MIDC. In this method, both the effect of the harmonic interaction between the AC and DC system and the harmonic transfer among subsystems of MIDC are considered...
Previous works on interleaved operation of switching power converters are based on the assumption that natural-sampling pulsewidth modulation (PWM) is used. Various interleaving strategies have been reported to minimize EMI filtering requirements, eliminate system resonance at certain frequencies, or minimize total harmonic current distortion through optimization of the interleaving phase shift angles...
This paper addresses the steady-state and dynamic modeling of a three-level, neutral-point-clamped (NPC) voltage source converter (VSC) with active front-end (AFE) in a commercial 2.5 MW variable speed motor drive (VSD). The AFE of the modeled VSD adopts the selective harmonic elimination SHE-PWM technique with the optimization of inverter power capacity and power source quality for a wide-range VSD...
Grid connected power electronic converters must be synchronized to the mains voltage by using suitable converter control circuit and gate signals, in order to function correctly. Without proper synchronization, the operation of the converter is adversely affected. This paper proposes a method to synchronize power converters to the mains voltage without using a phase-lock-loop (PLL). This is achieved...
The 100 Hz protection function in an HVDC system is a backup protection for the ac system. The misoperation of the 100 Hz protection has severe effect on the safe and stable operation of the power system. Based on the proposed sequence switching-function model of the HVDC converter, and combined with the short circuit calculation program for the ac system, a practical method of calculation and Identification...
This paper proposes a current control strategy with zero steady-state tracking error for grid-connected boost-inverters. Two boost converters are controlled separately to achieve both output current tracking and balanced output voltages. Based on cascading control and feedback linearization, the inner and outer-loop controllers are derived combining the inversion of boost converter model and the output...
This paper concentrates on the design, control and implementation of an LCL-filter-based shunt active power filter (SAPF), which can effectively compensate harmonic currents produced by nonlinear loads in a three-phase three-wire power system. The use of LCL-filter at the output end of SAPF offers superior switching harmonic suppression with much reduced size of passive filtering elements. This allows...
One of the most important aims in the electronic industry is the reduction of the size of the magnetic components, since it allows the improvement on the power density and the decrease in the cost of the power electronics equipment. In this paper, the chopped sinusoid peak current control scheme in critical conduction mode (CRM) PFC converter is proposed to reduce the inductance and the peak inductor...
The stability of HVDC system is under the influence of the strength of AC system, which is reflected as the AC and DC short-circuit ratio(SCR) on the converter stations. In this paper, a simulation study is carried out on the sending end of a certain HVDC system that has been put into operation under different SCR, using PSCAD/EMTDC. The simulation indicates that with the reduction of SCR, the recovery...
The EMTDC model of ±500kV Gao-Zhao HVDC with DC power forth-and-reverse transmission deicing function is firstly introduced, including model parameters, user-defined SIMADYN D module development and HVDC control strategies, then bipole DC power forth-and-reverse transmission theory, deicing function realization and deicing function operation procedure are presented successively, and finally some deep...
As one of the major advantages of High-brightness LED (HBLED) is their lifetime, electronic equipment used in power conditioning for HBLED should avoid some technologies as electrolytic capacitors that reduce significantly the operation lifetime. In this paper, a new strategy to drive HBLED from the AC mains is explored in order to reduce the required energy storage, while keeping a reduced level...
This paper presents a field programmable gate array (FPGA) implementation of a digital circuit that measures in real-time first harmonics of voltage and current medium-frequency (25 kHz-70 kHz) induction-heating cooking appliances. The inverter output voltage and load current are sensed using first-order delta-sigma (ΔΣ) analog to digital converters. The coefficients of the Discrete-Time Fourier Series...
This paper describes an algorithm for phase angle estimation based on symmetrical sequence components. The algorithm uses the recursive weighted least-squares method to estimate the fundamental component of the positive and negative sequences. The phase angle is estimated at each iteration from the fundamental component of positive sequence. The proposed method eliminates low order harmonics and dc...
This paper attempts to design a fuzzy controller, with a view to enhance the overall power quality of an ac-ac converter and regulate the load voltage. Besides it envisages investigating the performance of three firing strategies for the power switches in an AC-AC Converter. The algorithm is articulated in order that the input current vector is allowed to closely follow the source voltage wave such...
This paper is dedicated to a comparative study between prevailing schematics of rectifiers employed in industry for high current uses. Different configurations are introduced so far but the most common ones are thyristor- controlled rectifiers (ANSI 25-26 and ANSI 45-46). This paper proposes another configuration that is a combination of AC/AC converter, transformer and paralleled diode rectifiers...
Switching Mode Power Supplies (SMPS) usually emit Electromagnetic Interferences (EMI) at switching frequency and its harmonics. There are many different methods to reduce EMI interferences made by switching converters. In this paper different kinds of spread spectrum EMI reduction methods have been tested. Unlike traditional proper tuned filters used for this purpose, PWFM technique is a reliable...
This paper proposes a new topology for three-phase to three-phase cycloconverters. In the proposed topology, in order to generate the desired output voltage, the main states of switches are decreased in comparison with conventional topologies of three-phase to three-phase cycloconverters which can improve the performance of the cycloconverter. Increasing of the maximum output/input voltage transfer...
In this paper a 24 pulse autotransformer based ac-dc converter has been proposed to improvement power quality at the point of common coupling (PCC). The idea is to use an autotransformer based 12-pulse ac-dc converter using a DC ripple reinjection technique to double its pulse numbers (providing a 24-pulse AC-DC converter). A polygon connected autotransformer is used to produce 12-pulses with flexibility...
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