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Stochastic Hosting Capacity in LV Distribution Networks
Hosting capacity is defined as the level of penetration that a particular technology can connect to a distribution network without causing power quality problems. In this work, we study the impact of solar photovoltaics (PV) on voltage rise. In most cases, the locations and sizes of the PV are not known in advance, so hosting capacity must be considered as a random variable. Most hosting capacity methods study the problem considering a large number of scenarios, many of which provide little additional information. We overcome this problem by studying only cases where voltage constraints are active, with results illustrating a reduction in the number of scenarios required by an order of magnitude. A linear power flow model is utilised for this task, showing excellent performance. The hosting capacity is finally studied as a function of the number of generators connected, demonstrating that assumptions about the penetration level will have a large impact on the conclusions drawn for a given network
The Value of Reactive Power for Voltage Control in Lossy Networks
Reactive power has been proposed as a method of voltage control for distribution networks, providing a means of increasing the amount of energy transferred from distributed generators to the bulk transmission network. The value of reactive power can therefore be measured according to an increase in transferred energy, where the transferred energy is defined as the total generated energy, less the total network losses. If network losses are ignored, an error in the valuation of a given amount of reactive power will be observed (leading to reactive power provision being under- or over-valued). The non-linear analytic solution of a two-bus network is studied, and non-trivial upper and lower bounds are determined for this `valuation error'. The properties predicted by this two-bus network are demonstrated to hold on a three-phase unbalanced distribution test feeder with good accuracy. This allows for an analytic assessment of the importance of losses in the valuation of reactive power in arbitrary networks
Posttranslational modifications of alpha-tubulin: acetylated and detyrosinated forms in axons of rat cerebellum.
The distribution of acetylated alpha-tubulin in rat cerebellum was examined and compared with that of total alpha-tubulin and tyrosinated alpha-tubulin. From immunoperoxidase-stained vibratome sections of rat cerebellum it was found that acetylated alpha-tubulin, detectable with monoclonal 6-11B-1, was preferentially enriched in axons compared with dendrites. Parallel fiber axons, in particular, were labeled with 6-11B-1 yet unstained by an antibody recognizing tyrosinated alpha-tubulin, indicating that parallel fibers contain alpha-tubulin that is acetylated and detyrosinated. Axonal microtubules are known to be highly stable and the distribution of acetylated alpha-tubulin in other classes of stable microtubules suggests that acetylation and possibly detyrosination may play a role in the maintenance of stable populations of microtubules
Conic optimisation for electric vehicle station smart charging with battery voltage constraints
This paper proposes a new convex optimisation
strategy for coordinating electric vehicle charging, which accounts for battery voltage rise, and the associated limits on
maximum charging power. Optimisation strategies for coordinating electric vehicle charging commonly neglect the increase
in battery voltage which occurs as the battery is charged.
However, battery voltage rise is an important consideration,
since it imposes limits on the maximum charging power. This is
particularly relevant for DC fast charging, where the maximum
charging power may be severely limited, even at moderate state
of charge levels. First, a reduced order battery circuit model is
developed, which retains the nonlinear relationship between state
of charge and maximum charging power. Using this model, limits
on the battery output voltage and battery charging power are
formulated as second-order cone constraints. These constraints
are integrated with a linearised power flow model for three-phase
unbalanced distribution networks. This provides a new multiperiod optimisation strategy for electric vehicle smart charging.
The resulting optimisation is a second-order cone program, and
thus can be solved in polynomial time by standard solvers. A
receding horizon implementation allows the charging schedule
to be updated online, without requiring prior information about
when vehicles will arrive
-Ga<sub>2</sub>O<sub>3</sub> in Power Electronics Converters: Opportunities & Challenges
In this work, the possibility of using different generations of -Ga2O3 as an ultra-wide-bandgap power semiconductor device for high power converter applications is explored. The competitiveness of -Ga2O3 for power converters in still not well quantified, for which the major determining factors are the on-state resistance, , reverse blocking voltage, , and the thermal resistance, . We have used the best reported device specifications from literature, both in terms of reports of experimental measurements and potential demonstrated by computer-aided designs, to study power converter performance for different device generations. Modular multilevel converter-based voltage source converters are identified as a topology with significant potential to exploit these device characteristics. The performance of MVDC & HVDC converters based on this topology have been analysed, focusing on system level power losses and case temperature rise at the device level. Comparisons of these -Ga2O3 devices are made against contemporary SiC-FET and Si-IGBTs. The results have indicated that although the early -Ga2O3 devices are not competitive to incumbent Si-IGBT and SiC-FET modules, the latest experimental measurements on NiOX/-Ga2O3 and -Ga2O3/diamond significantly surpass the performance of incumbent modules. Furthermore, parameters derived from semiconductor-level simulations indicate that the -Ga2O3/diamond in superjunction structures delivers even superior performance in these power converters
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