Power Management Strategy of Low Voltage DC Micro Grid
In order to improve the efficiency and safety of the utilization of user-invested small scale renewable distributed generation (RDG), a structure of multi level DC micro grid based on the load classification, and corresponding stabilizing strategy were pr
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Abstract In order to improve the efficiency and safety of the utilization of user-invested small scale renewable distributed generation (RDG), a structure of multi level DC micro grid based on the load classification, and corresponding stabilizing strategy were proposed in this paper. The methods of load classification and multi-level grid are introduced to design the structure of DC micro grid. Three flexible operational modes of the structure and corresponding stabilizing strategy in grid mode based on the calculation of real-time status of user-level micro grids were discussed. A minimum test bench with two users was established, and a LabVIEWbased control system consists of supervisory terminal and main controller was designed for test and illustration. The results showed that the system can track the changes of status such as varying the loads and irradiance, and keep the bus voltage of the micro grid within a pre-set range. Keywords Photovoltaic • DC micro grid • Power management • Distributed power resource
1 Introduction In recent years, modern industries are exhausting the fossil energy, such as crude oil, coal, and natural gas, and the consuming of fossil energy will result in severe environmental problems. In this case, the renewable distributed generations (RDG), with PV arrays and wind turbines as the representatives [1, 2], are playing a more important role in the global energy market. As we know, small-scale standalone RDG systems are inefficient, and connecting the RDGs directly to the distribution grid, however, will degrade the
M. Lei (*) • Y. Guo • K. Ding Electric Power Research Institute, Hubei Electric Power Company, Wuhan, China e-mail: [email protected] W. Wang (ed.), Mechatronics and Automatic Control Systems, Lecture Notes in Electrical Engineering 237, DOI 10.1007/978-3-319-01273-5_51, © Springer International Publishing Switzerland 2014
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stability and quality of power supply due to the unreliability and unpredictability characteristics of renewable energy. Thus, connecting the small-scaled distributed RDGs to a node with local loads and energy storage devices, to form a micro grid system [3] becomes a commonly used approach to improve the efficiency of the renewable energy and reduce the dependence of fossil energy [4]. The commonly used structures of micro grids are single-leveled, which confined the utilization of RDGs to one specific operational mode. If the requirements of such mode cannot be satisfied, the whole system will be out of service. Micro grid can be classified as AC micro grid and DC micro grid [1]. In low-voltage cases, the DC micro grids are more efficient, less complicated, and safer than AC micro grids as described in [1, 2]. Therefore, in this paper, a multi-level DC micro grid structure designed for low-voltage DC micro grid connecting user-invested RDGs and household appliances together, and the flexible operational modes of this structure were proposed, and related stabilizing strategy in grid mode was discussed. The test results verifi
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