Showing 1–12 of 238 results
1Bit Sub Threshold Full Adders in 65nm CMOS Technology
In this paper a newرایگان!
In this paper a new full adder (FA) circuit optimized for ultra low power operation is proposed. The circuit is based on modified XOR gates operated in the subthreshold region to minimize the power consumption. Simulated results using 65nm standarad CMOS models are provided. The simulation esults show a 5% – 20% for frequency ranges from 1 KHz to 20MHz and supply voltages lower than 0.3V.
A Combined Gate Replacement and Input Vector Control Approach for Leakage Current Reduction
Input vector controlرایگان!
Input vector control (IVC) is a popular technique for leakage power reduction. It utilizes the transistor stack effect in CMOS gates by applying a minimum leakage vector (MLV) to the primary inputs of combinational circuits during the standby mode. However, the IVC technique becomes less effective for circuits of large logic depth because the input vector at primary inputs has little impact on leakage of internal gates at high logic levels. In this paper, we propose a technique to overcome this limitation by replacing those internal gates in their worst leakage states by other library gates while maintaining the circuit’s correct functionality during the active mode. This modification of the circuit does not require changes of the design flow, but it opens the door for further leakage reduction when the MLV is not effective. We then present a divide-and- conquer approach that integrates gate replacement, an optimal MLV searching algorithm for tree circuits, and a genetic algorithm to connect the tree circuits. Our experimental results on all the MCNC91 benchmark circuits reveal that 1) the gate replacement technique alone can achieve 10% leakage current reduction over the best known IVC methods with no delay penalty and little area increase; 2) the divide-and-conquer approach outperforms the best pure IVC method by 24% and the existing control point insertion method by 12%; and 3) compared with the leakage achieved by optimal MLV in small circuits, the gate replacement heuristic and the divide-and-conquer approach can reduce on average 13% and 17% leakage, respectively.
A Computational Framework for Uncertainty Quantification and Stochastic Optimization in Unit Commitment With Wind Power Generation
We present a computaرایگان!
We present a computational framework for integrating a state-of-the-art numerical weather prediction (NWP) model in stochastic unit commitment/economic dispatch formulations that account for wind power uncertainty. We first enhance the NWP model with an ensemble-based uncertainty quantification strategy implemented in a distributed-memory parallel computing architecture. We discuss computational issues arising in the implementation of the framework and validate the model using real wind-speed data obtained from a set of meteorological stations. We build a simulated power system to demonstrate thedevelopments.
A fuzzy logic based multi-agents controller
This paper presentsرایگان!
This paper presents a fuzzy logic based controller (Multi-Agents System Controller (MASC)) which regulates the number of agents released to the network on a Multi-Agents Systems (MASs). A fuzzy logic (FL) model for the controller is as presented. The controller is a two-inputs-one- output system. The controllability is based on the network size (NTZ) and the available bandwidth (ABD) which are the inputs to the controller, the controller’s output is number of agents (ANG). The model was simulated using SIMULINK software. The simulation result is presented and it shows that ABD is the major constraint for the number of agents released to the network.
A hybrid multi-agent based particle swarm optimization algorithm for economic power dispatch
This paper presentsرایگان!
This paper presents a new multi-agent based hybrid particle swarm optimization technique (HMAPSO) applied to the economic power dispatch. The earlier PSO suffers from tuning of variables, randomness and uniqueness of solution. The algorithm integrates the deterministic search, the Multi-agent system (MAS), the particle swarm optimization (PSO) algorithm and the bee decision-making process. Thus making use of deterministic search, multi-agent and bee PSO, the HMAPSO realizes the purpose of optimization. The economic power dispatch problem is a non-linear constrained optimization problem. Classical optimization techniques like direct search and gradient methods fails to give the global optimum solution. Other Evolutionary algorithms provide only a good enough solution. To show the capability, the proposed algorithm is applied to two cases 13 and 40 generators, respectively. The results show that this algorithm is more accurate and robust in finding the global optimum than its counterparts.
A hybrid wavelet-ELM based short term price forecasting for electricity markets
Accurate electricity price forecasting is a formidable challenge for market participants and managers owing to high volatility of the electricity prices. Price forecasting is also the most important management goal for market participants since it forms the basis of maximizing profits. This study investigates the performance of a novel neural network technique called Extreme Learning Machine (ELM) in the price forecasting problem. Keeping in view the risk associated with electricity markets with highly volatile prices, relying on a single technique is not so profitable. Therefore ELM has been coupled with the Wavelet technique to develop a hybrid model termed as WELM (wavelet based ELM) to improve the forecasting accuracy as well as reliability. In this way, the unique features of each tool are combined to capture different patterns in the data. The robustness of the model is further enhanced using the ensembling technique. Performances of the proposed models are evaluated by using data from Ontario, PJM, New York and Italian Electricity markets. The experimental results demonstrate that the proposed method is one of the most suitable price forecasting techniques.
A New Battery Charger for Plug-in Hybrid Electric Vehicle Application using Back to Back Converter in a Utility Connected Micro-grid
The major drawbacksرایگان!
The major drawbacks of the most battery chargers for plug-in hybrid electric vehicle (PHEV) are high volume and weight, low power, long charging time, deleterious harmonic effects on the electric utility distribution systems and low flexibility and reliability. This paper proposes a new battery charger structure for PHEV application using back to back (B2B) converter in a utility connected micro-grid. In the proposed structure, an AC micro-grid, based on the typical household circuitry configuration, is connected to the grid via a B2B converter; and the DC link is used for battery charging. In fact, the B2B converter can provide an isolated, low cost, simple and reliable connection with power-flow management between the grid, micro-grid and battery. This proposed structure, depending on the power requirement of the vehicle, can run in four different modes: battery charging mode from the grid (G2V) or microgrid (M2V), vehicle to grid mode (V2G) and vehicle to micro-grid mode (V2H). The feasibility of the proposed scheme has been validated in the simulation study for various operating conditions.
A Novel and Fundamental Approach towards Field and Damper Circuit Parameter Determination of Synchronous Machine
In this era of advanرایگان!
In this era of advanced computing where complex algorithms and expensive approaches are used to determine the machine parameters of a synchronous machine, this paper proposes a novel, economical and yet fundamental approach towards estimation of the d- and q-axis field and damper circuit parameters of a low/medium power wound-field synchronous machine. The proposed novel methodology employs fundamental voltage, current, flux linkage relationships of the 3-phase wound-field synchronous machine in a-b-c reference frame theory. Firstly, the proposed methodology has been explained in detail using analytical equations and then employed to determine the aforementioned parameters of a small laboratory synchronous machine. Other equivalent circuit parameters have been determined using conventional tests. Further validation of the proposed methodology was performed using two other larger machines with different nameplate ratings. Moreover, the aforementioned parameters of the larger machines were also experimentally determined using IEEE standard tests. Finally, a comparison of the results obtained employing the conventional and the proposed methodologies were performed and the proposed methodology has been established to be valid as the results are in close agreement.
A Novel Hybrid Network Architecture to Increase DG Insertion in Electrical Distribution Systems
Distribution networks will experience a deep mutation concerning their planning and operation rules due to the expected increase of distributed generation (DG) interconnection to the grid. Indeed, the opening of the electricity market or the growing global concern for environmental issues will lead to a massive development of DGs. Yet, a too large amount of DGs could raise technical problems on distribution networks which have not been planned to operate with bi-directional power flow. The existing solutions to solve marginal DG connections could be no longer relevant. The distribution network definitely has to evolve towards a smarter and more flexible network. Two possible ways to reach this goal are through new architectures and developing intelligent systems. This paper focuses on new architectures and operating modes. The traditional radial distribution network could accept more DGs by introducing appropriately specific loops. A new hybrid structure enabling the coexistence of the radial and meshed operation is proposed. It is equipped with autonomous circuit-breakers and automated switches that improve its reliability. A heuristic algorithm is also proposed to build this new architecture while ensuring the equality of consumers with respect to the continuity of service and while minimizing the global cost.
A Novel Protective Scheme to Protect Small-Scale Synchronous Generators Against Transient Instability
Installation of smalرایگان!
Installation of small generators in distribution networks has been increased recently due to its various benefits. One of the important issues related to these distributed generators is the effect of system faults on their transient stability. Due to the low inertia constant of the small-scale generators and the slow operation of the distribution networks’ protective relays, transient instability is quite probable for these generators. In this paper, the dynamic behavior of small-scale synchronous generators to the system faults and its sensitivity to the system parameters are investigated. Then, a practical protective method using theexisting overcurrent and undervoltage relays is proposed, and its advantages and disadvantages are pointed out. Next, based on the obtained information from sensitivity analysis, a novel protective relay is proposed to protect the generators against instability. The proposed relay uses a generator active power to determine the appropriate time to disconnect the generator. Simulation results confirm the secure operation and robustness of the proposed relay against system transients. In addition, the proposed algorithm complies with the generator fault-ride-through requirements.
A Phase-Domain Synchronous Machine Model With Constant Equivalent Conductance Matrix for EMTP-Type Solution
Interfacing machine models in either nodal analysisbased (EMTP-like) or state variable-based transient simulation programs play an important role in numerical accuracy and computational performance of the overall simulation. As an advantageous alternative to the traditional qd models, a number of advanced phase- domain (PD) and voltage-behind-reactance machine models have been recently introduced. However, the rotor-positiondependent conductance matrix in the machine–network interface complicates the use of such models in EMTP. This paper focuses on achieving constant and efficient interfacing circuit for the PD synchronous machine model. It is shown that the machine conductance matrix can be formulated into a constant submatrix plus a time-variant submatrix. Eliminating numerical saliency from the second term results in a constant conductance matrix of the proposed PD model, which is a very desirable property for the EMTP solution since the refactorization of the network conductance matrix at every time step is avoided. Case studies demonstrate that the proposed PD model represents a significant improvement over other established models used in EMTP while preserving the accuracy of the original/classical PD model.
A review of solar photovoltaic technologies
Global environmental concerns and the escalating demand for energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till date. The power from sun intercepted by the earth is about 1.8 × 1011 MW, which is many times larger than the present rate of all the energy consumption. Photovoltaic technology is one of the finest ways to harness the solar power. This paper reviews the photovoltaic technology, its power generating capability, the different existing light absorbing materials used, its environmental aspect coupled with a variety of its applications. The different existing performance and reliability evaluation models, sizing and control, grid connection and distribution have also been discussed.