Showing 4 results for H. Farzanehfard
H. Farzanehfard, Z. Ghassemi and H. Moghbeli,
Volume 18, Issue 2 (7-1999)
Abstract
H. Farzanehfard, G. Askari and S. Gazor,
Volume 21, Issue 2 (1-2003)
Abstract
In recent years, active filters have been considered and developed for elimation of harmonics in power networks. Comparing with passive, they are smaller and have better compensating characteristics and resistance to line distortions. In this paper, a novel idea based on adaptive filter theory in presented to develop an active filter to eliminate the distortions of an arbitrary signal. Using this idea, new methods of active power filters, are introduced to remove harmonic distortions in single phase power networks. Stability of these methods are analyzed and the simulation results are shown. Design and implementation of this adaptive active filter are done and the performance and advantages of this technique are affirmed by the practical results. Exact estimation of amplitude, frequency and phase of input signal first harmonic is the most important advantage of this adaptive technique. Furthermore, this method is for canceling the harmonic of any arbitrary signal and can easily be modified for other systems, and three phase networks.
Due to its adaptive nature, this technique can adopt itself with variation in environment and system parameters and be adjusted for optimal behaviour.
Keywords: Adaptive active filter, ac network, amplitude, Phase and frequency Estimation, Floque theorem, Averaging theorem.
H. Farzanehfard and A. Pakizeh Moghadam,
Volume 22, Issue 1 (7-2003)
Abstract
Soft Switcing techniques have recently been applied in the design of dc-ac converters, in order to achive better performance, higher efficiency, and power density. One of the soft switching techniques uesd in inverters is resonant dc links. These topologies have some disadvantages such as irregular current peaks, large voltage peaks, uncotrollble pulse width, etc. Another soft switching method in inverters is using Quasi –resonant links, which have PWM modulation capability. Inverters with series or parallel Quasi-resonant dc links use several quasi-resonant current or voltage pulses, respectively, to produce PWM modualation. In this paper an inverter with a novel Quasi-resonant series dc link is introduced. This topology enables current source inverters to have characteristics such as resonant pulse peak limition and pulse width controllability. This circuit provides the inverter with two to three ranges of PWM control capability which increases the switching time control in a larger range.
Various operational modes of this novel Quasi-resonant dc link is analyesed and then the circuit losses is calculated. Finally, simulation results by PSPICE software is presented to justify the circuit operation.
Keyword: Inverter, Soft switching, Novel quasi-series resonant link, increasing control areas, Losses
H. Farzanehfard, S. R. Motahari and M.m. Tavasoulkhamseh,
Volume 23, Issue 2 (1-2005)
Abstract
One of the difficulties with PWM switching converters is high switching loss and electromagnetic interference due to switching at non-zero voltage and current, which limits the operating frequency. In order to reduce the converter volume and weight (by increasing the frequency) and reducing switching losses, zero voltage and current switching methods are recommended. In this paper, four main zero voltage switching (ZVS) methods in full bridge converters are introduced and compared. These four methods are compared on dead times required to obtain the ZVS, load range at ZVS condition, circulating energy in the switch anti parallel diodes during freewheeling periods and voltage oscillations on rectifying diodes. Finally, the results of a 3 KW prototype full bridge ZVS converter with a clamp circuit for rectifier diodes oscillations are presented and analyzed
