مجله مهندسی برق و الکترونیک ایران
سال هفتم شماره 2 (پاییز و زمستان 1389)

The advent of cybertechnologies has led to radical paradigm shifts in our social, economic, cultural, and psychological conceptualizations. The paper investigates the advent of cyborgs, indeed our transformation into cyborgs, and the impact of this transformation upon identities and face management, which has an important social value since the late modernism. Cyborg is a designation for the inhabitants of the new environment: the cyberspace. They represent manifold boundary pollutions. The idea of cyberspace already marks the fusion of the real with the imagined and the fantastic. This new virtual space is being inhabited with a new kind of actors: intelligent agents. A fusion of animal and machine. The boundary between human and non- human is also being transgressed. The problematic concept of selfhood and the related technologies constitute the subject of this discourse. It is argued that this process of confusion and corruption can be viewed as also a process of breaking down monological communication and totality.

Signed digit (SD) number systems provide the possibility of constant-time addition, where inter-digit carry propagation is eliminated. Such carry-free addition is primarily a three-step process; adding the equally weighted SDs to form the primary sum digits, decomposing the latter to interim sum digits and transfer digits, which commonly belong to {–1, 0, 1}, and finally adding the transfers to the corresponding (i.e., with the same weight) interim sum digits. All the final sum digits are therefore obtained in parallel. The special case of radix-2h maximally redundant SD number systems is more attractive due to maximum symmetric range (i.e., [–2h+1, 2h–1]) with only one redundancy bit per SD, and the possibility of more efficient carry-free addition. The previous relevant works use three parallel adders that compute sum and sum±1, where some speed-up is gained at the cost of more area and power. In this paper, we propose an alternative nonspeculative addition scheme that uses carry-save encoding for representation of the primary sum and interim sum digits and computes the transfer digits via a fast combinational logic. The simulation and synthesis of the proposed adder, based on 0.13 μm CMOS technology, shows advantages in terms of speed, power and area.

This paper presents the method of reducing torque ripple of brushless DC (BLDC) motor. The commutation torque ripple is reduced by control of the DC link voltage during the commutation time. The magnitude of voltage and commutation time is estimated by a neural network and optimized with an optimization method named particle swarm optimization (PSO) algorithm analysis. The goal of optimization is to minimize the error between the command torque and real torque and doesn’t need knowledge of the conduction interval of the three phases. It adaptively adjusts the DC link voltage in commutation duration so that commutation torque ripple is effectively reduced. In this paper, the performance of the proposed brushless DC (BLDC) control is compared with that of conventional BLDC drives without input voltage control.

Nowadays, high-voltage circuit breakers have reached such high short-circuit capabilities that testing them under the full rated voltage is generally not possible with direct tests, and they are conducted by using the synthetic test methods. Although the phenomena associated with making tests is of particular importance especially in case of load break switches, but making tests are rather disregarded in power studies. The aim of this paper is to present an innovative simple test circuit for single-phase short-circuit making test which can properly test the breaker at a reasonable cost, eliminating the need to large capacity power sources. The test circuit satisfies all relevant standard requirements and its results are conformable to those of reputable international testing laboratories.

Reactive power management plays an essential role in the secure operation of the power system as an ancillary service. Although in electricity markets, the particular attention is paid to active power, the reactive power also plays an important on total generation costs of electricity. On the other hand, as it is mainly confined to local consumption, to avoid market power and maintain the secure operation of a power system, accurate reactive power pricing and cost allocation methods are essential. It has been a challenging problem during the past decade. However, most methods proposed so far for reactive power pricing, are essentially based on empirical approximations. In this paper a new method for reactive power cost allocation is proposed. The method is based on the calculation of accurate cost imposed on generators supporting reactive power. The proposed method is fair, accurate and realistic and it can be formulated very easily. Furthermore, a new approach based on tracing algorithm is proposed for pricing of reactive power which considers the cost of both active and reactive losses allocated to each generator and cost of capacitor banks. To validate the performance of the proposed method, it is applied to both 9-bus and 30-bus IEEE test systems.

This paper proposes a novel technique for solving generation scheduling and ramp rate constrained unit commitment. A modified objective function associated with a new start-up cost term is introduced in this paper. The proposed method is used to solve generating scheduling problem satisfying SRR, minimum up and down time as well as ramp rate constraints. Two case studies are conducted to implement and show the effectiveness of the proposed method. One is a conventional 10-unit system and its multiples while the other is a 26-unit system with 24-h scheduling horizon. A comparison between the results of the proposed technique with those of some methods demonstrates a significant improvement.

A detailed model of wind power station, including Double Fed Induction Generator, DFIG is presented in this paper. Two control mechanisms are included in the model. The inner control system uses stator flux oriented control for the rotor side converter and grid voltage vector control for the grid side converter. The outer control system is used for wind turbine pitch angle. PSCAD/EMTDC is used for the simulation. The simulation model is used to investigate the performance of controllers under wind speed variations, short circuit at the grid side and dynamics of active power demand.

The infrastructure of the electricity grid and super grid system in the hitherto industrialized world was to a large extent built up in the decades following World War II with a peak in investments around 1960-1980. This means that the flotilla of power transformers is now starting to reach projected lifetime of around 40 years. During the last couple of decades there has also been an ongoing deregulation and privatization of electricity generation and distribution. This has led to higher utilization of existing equipment to deliver an ever increasing demand of power. The demand for planned asset management, investments, reliability and availability of power delivery, has also increased. To ensure that aging equipment is working satisfactory and will do so for yet some time, interest in aging behavior of power equipment has increased. Yet there is precious little basic information openly available on how the insulating materials in transformers behave over longer periods of time. Such information is valuable both from the perspective of transformer maintenance/asset management, and as background information to make informed choices on which type of insulating liquid to employ in new equipment.