Iranian Journal of Electrical and Electronic Engineering
Volume:6 Issue: 2, Jun 2010

In this paper, using the neural space mapping (NSM) concept, we present a SPICE-compatible modeling technique to modify the conventional MOSFET equations, to be suitable for ballistic carbon nanotube transistors (CNTTs). We used the NSM concept in order to correct conventional MOSFET equations so that they could be used for carbon nanotube transistors. To demonstrate the accuracy of our model, we have compared our results with those obtained by using open-source software known as FETToy. This comparison shows that the RMS errors in our calculated IDS, under various conditions, are smaller than the RMS errors in IDS values calculated by the existing analytical models published by others.

Q frequency reference devices are essential components in many Integrated circuits. This paper will focus on the Resonant Suspended Gate (RSG) MOSFET. The gate in this structure has been designed to resonate at 38.4MHz. The MOSFET in this device has a retrograde channel to achieve high output current. For this purpose, abrupt retrograde channel and Gaussian retrograde channels have been investigated.

New control circuits and algorithms are frequently proposed to control the impedance (Z) source inverter in efficient way with added benefits. As a result, several modified control techniques have been proposed in recent years. Although these techniques are clearly superior to the simple boost control method which was initially proposed along with the Z-source inverter (ZSI), little or conflicting data is available about their merits relating to each other. In this paper, it is shown how the shoot-through periods are inserted in the switching waveforms of the power switches and the performances of them are analyzed based on the operation of ZSI. Simple boost control, maximum boost control, constant boost control and space vector modulation based control methods given in the literature has been illustrated with their control characteristics. A critical investigation on ripples of the impedance source elements, output voltage controllability, output harmonic profile, transient response of the voltage across the impedance source capacitor and voltage stress ratio etc has been presented with the simulation results. The simulation results are experimentally verified in the laboratory with digital signal processors (DSP). DSP coding for the above all control techniques has been generated by interfacing Matlab/Simulink with DSP C6000 tool box and signal processing block set.

This paper presents a method to allocate the transmission network costs to users based on nodal pricing approach by regulating the nodal prices from the marginal point to the new point. Transmission nodal pricing based on marginal prices is not able to produce enough revenue to recover the total transmission network costs. However, according to the previous studies in this context, this method recovers only a portion of transmission costs. To solve this problem, in this paper a method is presented in which by considering the direction and amount of injected power in each node the marginal price is regulated to the new price, in such a way as the nodal pricing can recover the total transmission network costs. Also the proposed method is able to control the cost splitting between loads and generators in accordance with the pre-specified ratio. The proposed method is implemented on both IEEE 24-bus and 118-bus test systems and the obtained results are reported.

Reliability of a power system is considerably influenced by its equipments. Power transformers are one of the most critical and expensive equipments of a power system and their proper functions are vital for the substations and utilities. Therefore, reliability model of power transformer is very important in the risk assessment of the engineering systems. This model shows the characteristics and functions of a transformer in the power system. In this paper the reliability model of the power transformer with ONAN cooling is obtained. The transformer is classified into two subsystems. Reliability model of each subsystem is achieved. Markov process representation and the frequency/ duration approach are employed to obtain a complete reliability model of the subsystems. By combining these models reliability model of power transformer is obtained. The reliability model associated with the transformer is then proposed combining the models of subsystems. The proposed model contains five states. To make the model more applicable, the 5-state model is alleviated to a 3-state one. Numerical analysis and sensitivity analysis relevant to the proposed reliability model are performed for evaluating the numerical values of the model parameters and the impact of different components on the reliability of the model.

Here, a new fuzzy direct torque control algorithm for induction motors is proposed. As in the classical direct torque control, the inverter gate control signals directly come from the optimum switching voltage vector look-up table, the best voltage space vector selection is a key factor to obtain minimum torque and flux ripples. In the proposed approach, the best voltage space vector is selected using a new fuzzy method. A simulation model is built up and the torque and flux ripples of basic direct torque control and the proposed method are compared. The simulation results show that the torque and flux ripples are significantly decreased and in addition, the switching frequency can be fixed.

This paper deals with the measurement of AC corona inception voltage, Vincp, at the tip of a rod electrode using a hemispherically-capped rod-plane electrode configuration for various rod radii with a short air gap. Effects of atmospheric pressure and temperature variation on Vincp are investigated experimentally. An empirical equation for the field form factors of the hemispherically capped rod-plane electrodes is proposed with its range of applicability. The obtained results are analyzed to derive a more accurate analytical equation for the calculation of the electric field at corona inception voltage, Eincp, and the average of electric field distribution, Emean