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Islanding detection is an essential function for safety
and reliability in grid-connected Distributed Generation Systems (DGS).
Passive and active islanding detection methods have been analyzed in literature
considering DGS with only one inverter connected to the utility. With the big
scale application of photovoltaic (PV) power systems, islanding detection
technology of multi-inverter DGS has been paid more attention. This paper
analyzes the performance of diverse islanding detection methods in multiple
inverters grid-connected PV systems. Non-Detection Zones (NDZ) of
multi-inverter systems in a load parameter space are used as analytical tool.
The paper provides guidance for the islanding detection design in multiple
A forecast method of the impact factor
trend was given based on grey system theory. Using this method, combined with the
top 20 management science journals, the grey system GM (1, 1) model was
constructed. The model evaluates and predicts the average impact factor trend
of the top 20 management science journals.
A square complex matrix is called if it
can be written in the form with being fixed unitary and being arbitrary matrix in . We give necessary and sufficient conditions for the
existence of the solution to the system
of complex matrix equation and present an
expression of the solution to the system
when the solvability conditions are satisfied. In addition, the solution to an
optimal approximation problem is obtained. Furthermore, the least square solution with least
norm to this system mentioned above is considered. The representation of such
solution is also derived.
In this paper, isophorone diisocyanate (IPDI),
polyethylene glycol (PEG), dimethylolpropionic acid (DMPA) and internal
crosslinking agent trimethylolpropane (TMP) were used to prepare waterborne
polyurethane. And then double-crosslinked polyurethane-acrylic composite
aqueous dispersion was prepared in which polyacrylate was adopted to modify
waterborne polyurethane and some special external crosslinking agents were
added including silicone and trifunctional aziridine. The influence of the
amounts of internal and external crosslinking agents, emulsifier, initiator on
the particle size, particle size distribution, viscosity, molecular weight, as well as
water adsorption ratio were studied.