Research on 3D Modeling and Visualization of Coal Pillars for Surface Protection

In order to safely exploit coal resource, protection coal pillars must be prepared in coal mines. Some correlative parameters of protection coal pillar are calculated by Drop face and Drop line methods. Models of protecting surface objects and coal pillars are established by TIN modeling and object-oriented technique. By using ACCESS2000as the database and the VC＋＋ and OpenGL as the language, the calculation of protective coal pillars is realized and the 3D-visulizaiton system for protected objects on ground surface and for coal pillars is developed. The system can obtain the data of characteristic points on the surface interactively from the digitized mine topography map, constructing 3D model automatically. It can also obtain the interrelated parameters of the coal seam and drill hole data from existing geolog!cal surveying database to calculate the location, surface area and the total coal columns. The whole process can be computed quickly and accurately. And the 3D visualization system was applied in a mine, showing that the system solve the problem of complex calculation, not only realized the automatic 3D mapping and visualization of coal pillars for buildings protection, but also greatly improves the working efficiency.

Study of Improved Load Sharing Methodologies for Distributed Generation Units Connected in a Microgrid

In this paper,an improved load sharing strategy is proposed for distributed generation units(DGs)connected in a microgrid.Conventional frequency and voltage droop control result in unacceptable active and reactive power sharing.The proposed method formulates a suitable algorithm for load sharing in the islanded microgrid.The feeder power loss and the line impedance voltage drops are minimized so as to regulate the voltage at the point of common coupling(PCC)at its nominal value.The desired DG output voltages are calculated and a linear relationship is obtained between the shared active and reactive powers and the DG output voltages.A master DG controller sets the frequency which is followed by other DG units.The reference powers for the DG units are adjusted so as to maintain the rated PCC voltage.The proposed strategy is verified taking into account the DG ratings,unequal line impedance drops,feeder losses,change in system impedance and effect of DG local loads and formulates an improved power sharing strategy that also facilitates PCC voltage regulation under variable loading conditions.Simulation and experimental results are presented to verify the effectiveness of the proposed method.