Iranian Journal of Electrical and Electronic Engineering
Volume:3 Issue: 3, July 2007

A new heterodyne nano-displacement with error reduction is presented. The main errors affecting the displacement accuracy of the nano-displacement measurement system including intermodulation distortion error, cross-talk error, cross-polarization error and phase detection error are calculated. In the designed system, a He-Ne laser having three-longitudinal-mode is considered as the stabilized source. The free spectral range of the 35cm laser cavity is about 435-MHz at 632.8-nm wavelength, which a secondary beat frequency equal to 300-kHz is produced by combining the reference and measurement beams. The resolution of the displacement measurement resulting from intermodulation distortion, cross-talk and cross-polarization errors is limited to 18-pm. Also, the phase detection uncertainty causes an error of only 5.9-pm in the displacement measurement. Furthermore, frequency-path models of two- and three-longitudinal-mode laser interferometers are modeled as the ac interference, ac reference, dc interference and optical power terms. A comparison study between two- and three-longitudinal-mode laser interferometers confirms that the performance of the designed system is considerably improved.

This paper presents a novel implementation of an electromagnetically coupled patch antenna using air gap filled substrates to achieve the maximum bandwidth. We also propose an efficient modeling technique using the FDTD method which can substantially reduce the simulation cost for modeling the structure. The simulated results have been compared with measurement to show the broadband behavior of the antenna and the accuracy of the proposed modeling technique. The measured results show a 16% of VSWR<2 bandwidth which is considerable considering the inherent bandwidth limitations in microstrip antenna technology.

This paper presents a parametric low differential order model, suitable for mathematically analysis for Induction Machines with faulty stator. An adaptive Kalman filter is proposed for recursively estimating the states and parameters of continuous–time model with discrete measurements for fault detection ends. Typical motor faults as interturn short circuit and increased winding resistance are taken into account. The models are validated against winding function induction motor modeling which is well known in machine modeling field. The validation shows very good agreement between proposed method simulations and winding function method, for short-turn stator fault detection.

This paper presents an original study on the generated torque ripples of phase commutation in the Four-Switch, Three-Phase Inverter (FSTPI) Brushless DC (BLDC) motor drive which is suitable for low cost applications. Analytic values of torque ripple and commutation duration are obtained for different operation conditions. Moreover, limitation on the speed range operation caused from splitting of the DC-link voltage is shown exactly. Then a novel current control technique is developed to minimize the commutation torque ripple for a wide speed range. The technique proposed here is based on a strategy that the current slopes of the rising and the decaying phases during the commutation intervals can be equalized by proper duty-ratios at commutations. Finally, the validity of the proposed analysis and developed torque ripple reduction technique are verified via simulation.

This paper describes a DC isolated network which is fed with Distributed Generation (DG) from photovoltaic (PV) renewable sources for supplying unbalanced AC loads. The battery energy storage bank has been connected to the DC network via DC/DC converter to control the voltage of the network and optimize the operation of the PV generation units. The PV arrays are connected to the DC network via its own DC/DC converter to ensure the required power flow. The unbalanced AC loads are connected to the DC network via its own DC/AC converter. This paper proposes a novel control strategy for storage converter which has a DC voltage droop regulator. Also a novel control system based on Park rotating frame has been proposed for DC/AC converters. In this paper, the proposed operation method is demonstrated by simulation of power transfer between PV arrays, unbalanced AC loads and battery unit. The simulation results based on PSCAD/EMTDC software show that DC isolated distribution system including PV generation systems can provide the high power quality to supplying unbalanced AC loads.