Process variations are a major concern in today's chip design since they can significantly degrade chip performance. To predict such degradation, existing circuit and MEMS simulators rely on Monte Carlo algorithms, which are typically too slow. Therefore, novel fast stochastic simulators are highly desired. This paper first reviews our recently developed stochastic testing simulator that can achieve speedup factors of hundreds to thousands over Monte Carlo. Then, we develop a fast hierarchical stochastic spectral simulator to simulate a complex circuit or system consisting of several blocks. We further present a fast simulation approach based on anchored ANOVA (analysis of variance) for some design problems with many process variations. This approach can reduce the simulation cost and can identify which variation sources have strong impacts on the circuit's performance. The simulation results of some circuit and MEMS examples are reported to show the effectiveness of our simulator

Research of grid connected wind turbines has gained great interest in the recent years. This led to introduce guidelines and regulations regarding the connection of large wind farms to the electrical network. One of such guidelines is low voltage ride-through capability (LVRT). In this paper, a survey on recent LVRT solutions for permanent magnet synchronous generators (PMSG) is carried out along with a brief explanation of grid codes. Among those solutions is the control of fully rated converters, blade pitch angle control and capacitor sizing. Other solutions such as active crowbar rotor circuit and the DC bus energy storage circuit are illustrated. The survey extends to provide possibilities for the development of further LVRT research at the wind farm level using high power FACT devices.Index Terms-permanent magnet synchronous generator, low voltage ride through, wind energy grid connection, renewable energy

Wind turbine construction is a challenging undertaking due to the need to lift heavy loads to high locations in conditions of high and variable wind speeds. These conditions create great risks to contractors during the turbine assembly process. This paper presents a simulation-based system to aid in the construction planning of wind turbines. The system is composed of three main components; 1) A wind speed forecasting module based on artificial neural networks, 2) A series of discrete event simulation models that act as a test bed for different turbine construction methods and resource utilizations, and 3) A rule-based system that relates prevalent wind speed to the impact on lifting activity durations. Actual wind speed data from the Zafarana wind farm in Egypt is used and turbine construction productivity and resource utilization is compared for two common turbine construction methods.

Problem statement:The purpose of this study is to design a renewable energy hydrogen based power system to provide electricity to a coastal residential area in east coast area (Kuala Terengganu) of Malaysia. Approach: The selected case study represents a power demand of 20 kWh day −1 . The autonomous system used in this study is diesel generator, wind and photovoltaic hybrid system. The power system was redesigned and optimized as hydrogen-based autonomous power systems in order to meet the existing user's power demand at a minimum cost of energy. Wind speed and solar radiations data obtained from Malaysian Meteorological Department have been used in the simulation process through optimization software, Hybrid Optimization Model for Electric Renewables (HOMER). Results: Three systems that were considered in this study area are stand alone PV-wind-diesel, stand alone PV-wind-hydrogen and grid connected PV-wind-hydrogen energy system. The proposed systems then were compared regarding on their operational characteristics and cost values. The comparisons prove that grid connected PV-wind-hydrogen energy system had the lowest total net present cost and cost of energy, $53,197 and $0.57/kWh, respectively that makes it the most cost effective system and followed by PV-wind-diesel and stand alone PV-wind-hydrogen system. Conclusion/Recommendations: It can be concluded that the hydrogen-based system can become a favorable system without aid from the grid system and bring advantage in technical and economic point of view and also suitable to be applied in the coastal residential application as energy carrier if only the current cost of wind turbine, PV arrays and hydrogen system technology have been reduced to its minimum rate.

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