Simplified Second-Order Generalized Integrator - Frequency-Locked Loop

Second-Order Generalized Integrator –Frequency-Locked Loop (SOGI-FLL) is a popular technique available in the grid synchronization literature. This technique uses gain normalization in the frequency locked-loop. This increases the computational complex-ity. In this paper, we propose an alternative imple-mentation to reduce the computational complexity of the SOGI-FLL. The proposed implementation modifies mainly the frequency locked-loop part and requires normalized voltage measurement. dSPACE 1104 board-based hardware implementation shows that the proposed implementation executes 20 % faster than the standard implementation. This could be very beneficial for high switching frequency application e.g. ≥ 1 MHz. In ad-dition to the nominal frequency case, multiresonant implementation is also proposed to tackle grid harmonics using a simpler harmonic decoupling network. Small signal dynamical modeling and tuning are performed for both implementations. Dynamical equivalence is also established between the two implementations. Experimental comparative analysis demonstrates similar or better performance (depending on test scenarios) with respect to the standard implementation of the SOGI-FL

Four wave mixing nonlinearity effect in wavelength division multiplexing radio over fiber system

The integration of wireless and optical networks is a potential solution for the increasing capacity and mobility as well as decreasing costs in the access networks. Optical networks are fast, robust and error free, however, there are nonlinearity obstacles preventing them from being perfect media. The performance of wavelength division multiplexing (WDM) in radio over fiber (RoF) systems is found to be strongly influenced by nonlinearity characteristics in side the fiber. The effect of four wave mixing (FWM) as one of the influential factors in the WDM for RoF has been studied here using Optisystem and Matlab. From the results obtained, it is found that the FWM effects have become significant at high optical power levels and have become even more significant when the capacity of the optical transmission line is increased, which has been done by either increasing the channel bit rate, and decreasing the channel spacing, or by the combination of both process. It is found that when the channel spacing is 0.1 nm, 0.2 nm and 0.5 nm the FWM power is respectively, becomes about -59 dBm, -61 dBm and -79 dBm. This result confirms that the fiber nonlinearities play decisive role in the WDM for RoF system. The simulation results obtained here are in reasonable agreement as compared with other numerical simulation results obtained, elsewhere, using different simulation tools

Study on the trade off between throughput and power consumption in the design of bluetooth low energy applications

Bluetooth Low Energy (BLE) is an emerging technology that is considered a breakthrough in the field of wireless communications due to its very low power consumption property. One of the issues of the current practical implementations of BLE is throughput. The theoretical throughput of BLE is around 260 Kbps but the current practical implementations have much lower throughput values. In this work, the effect of important parameters related to the BLE connection and the Generic Attribute Profile (GATT) protocol on the throughput and power consumption of the system has been studied based on practical laboratory experiments. The throughput was found to increase almost linearly with the number of characteristics and characteristic size used in a BLE application. Additionally, the throughput was found to have an inverse relationship with the connection interval. The average current consumed while the device is connected was found to have a proportional relationship with the number of characteristics and characteristic size and therefore the battery life of a BLE device is greatly affected by these variables. Understanding these results is crucial to BLE system designers and developer because it allows them to design their systems in a way that suits their needs optimally

Characterization of spring thaw for different forest types in the southern boreal forest under current and future climate

Spring thaw timing is of great significance for ecological, biogeochemical, and hydrological processes in seasonally-frozen boreal forests. Site characteristics such as canopy architecture, ground cover type, thickness of organic soils, and mineral soil texture can influence thaw dynamics causing spring thaw variability for different forest types. The objective of this research was to characterize the existing and future variability of spring thaw between the two coniferous (black spruce and jack pine) and one deciduous (aspen) forests located in the southern boreal forest of Western Canada. Long-term observations (1997-98 to 2015-16) were used to explore existing inter-site variability of spring thaw. During the observation period, seasonal snowfall was similar at all three sites, but snow accumulation on the ground was 15% to 20% higher for the deciduous than the coniferous forests. The timing for the onset of snowmelt and soil thaw were similar between the sites, but varied considerably for soil thaw completion. The soil thawed at the aspen site about 2.5 and 4.5 weeks earlier than the jack pine and black spruce sites, respectively. This was likely driven by the higher sub-canopy net radiation of the leafless deciduous canopy. The differences between the two coniferous forest sites were driven by the thicker forest floor at the black spruce site causing higher ice content and providing better insulation effects. Carbon uptake was strongly correlated with snowmelt and soil thaw at both the coniferous forest sites but the correlations were not statistically significant for the aspen site. The Simultaneous Heat and Water (SHAW) model was used to predict the future spring thaw variability for the study sites. The model was selected after its performance evaluation against the observations and simulations of the Canadian Land Atmosphere Surface Scheme (CLASS) and Cold Regions Hydrological Model (CRHM) for winter-spring transition at the jack pine site. All three models simulated similar snow ablation date, with a difference of 1 to 5 days, despite large differences in snowmelt rates. The SHAW model performed better for simulating soil thaw timing (the maximum difference between observations and simulations was about 1 week for SHAW, 3 weeks for CLASS, and 6 weeks for CRHM) but spring evapotranspiration was overestimated (by 40 to 95 mm) by all three models. After a rigorous parameter sensitivity analysis and calibration of SHAW, it was determined that the ground cover layer in the model is important for improved simulations of soil temperature/soil thaw and an additional term in Jarvis-Stewart resistance scheme to consider the influence of low soil temperatures on stomatal conductance is needed for improving simulations of spring evapotranspiration. An approach based on the growing degree days (GDD) was proposed to indirectly consider the soil thermal environment in modelling the functioning of stomatal conductance. The consideration of ground cover layer reduced model bias up to 2.5 weeks and the proposed GDD factor reduced root mean square error for evapotranspiration by 35 to 40 mm. Future (2085-2097) weather data over Western Canada was generated by the Weather Research and Forecasting (WRF) model using the Pseudo Global Warming approach. The future climate at the study sites is projected to be wetter (18%) and warmer (5.8°C). In response, SHAW predicted significant changes in spring thaw processes. For example, future snow ablation and soil thaw timing are predicted to advance relative to historical conditions (2000-2012) by about 2.5 weeks and 6 to 7 weeks, respectively. The frozen ground depth is predicted to reduce by 45% to 58% with the highest reduction at the black spruce site which has the highest average soil water content. The mean annual soil temperature is projected to rise by 3.3°C to 3.9°C at all three sites. The evapotranspiration is predicted to increase by 26% to 28%. This study advances our understanding about the existing variability of spring thaw for different forest types in the southern boreal forest and predicts future changes in spring thaw dynamics at these sites

AN APPROACH FOR DESIGN AND MANAGEMENT OF A SOLAR-POWERED CENTER PIVOT IRRIGATION SYSTEM

Emerging financial and environmental challenges associated with conventional power sources have increased global interest in consuming unpolluted, renewable energy sources for irrigation sector. Solar energy may be an attractive choice in this regard due to its strong influence on crop water use and related energy requirement. However, a comprehensive approach for a reliable and economically viable photovoltaic (PV) system design to produce energy from solar source is required to accurately explore its potential. This thesis describes the development and application of a reliability assessment model, identifies a suitable solar irrigation management scheme, and provides guidelines for evaluating economic viability of a solar-powered center pivot irrigation system. The reliability model, written in MATLAB, was developed based on the loss of power supply probability (LPSP) technique in which various sub-models for estimating energy production, energy requirement and energy storage were combined. The model was validated with actual data acquired from the study site located at Outlook, Saskatchewan, Canada and an excellent agreement was found. For example, normalized root mean square error (NRMSE) for the battery current was found to be 0.027. Irrigation management strategies (irrigation depth, frequency and timing) were investigated by comparing the PV system sizing requirement for a conventional (25-35 mm per application) and for a frequent light irrigation management strategy (5-8 mm per application). The results suggest that the PV sizing can be reduced significantly by adopting frequent light irrigations which utilize the power as it is produced during daylight hours, rather than relying on stored energy. The potential of a solar-powered center pivot irrigation system was revealed for three different crops (canola, soybean and table potato) at the site by conducting a detailed economic analysis for the designed PV system. High value crops with moderate water requirements such as table potatoes appeared to be the most feasible choice for the study site. However, the potential may greatly vary for different crops in altered locations due to management, agronomic, climate, social, and economic variations. It can be concluded that a holistic approach described here can be used as a tool for designing an appropriate PV powered center pivot irrigation system under variable operating and meteorological conditions. Furthermore, its potential can be accurately explored by conducting a detailed economic analysis for a given location, considering different available crop choices