Research On DC/DC Sectionalizer Based DC Micro-grid

Renewable energy usage is gradually becoming a great concern nowadays because of the energy exhaustion and environmental problems, at the same time requiring the adjustment of energy structure urgently. However, the acceptance of large-scale intermittent renewable energy by existing power grids is not that satisfying in terms of system vulnerability and unsuitability. Among the methods for solving this problem, the application of DC micro grid, which is of high reliability and low energy consumption, is widely researched and discussed because of its advantages.This thesis presents a DC-DC sectionalizer applied in DC micro-grid, which replaces the solid-state circuit breakers. By using These electronic devices, a multi-division and multi-contact power supply pattern will be accomplished with the connection of different DC bus. According to this, a study on DC micro-grid is conducted and the main contents are introduced as follows.Firstly, a small-signal model is built according to the structure and working principle of DC/DC sectionalizer.Then a control strategy is proposed basing on the model above and control methods involving phase-shifting power control and direct double-loop power control, in order to achieve power control and fault isolation in DC micro grid.Secondly, a thorough research of DC micro-grid inner structure is carried on, which analysing the working principles and control strategies of energy storage systems, permanent-magnet direct-drive wind power generation systems and photovoltaic power generation systems.Then the factors that influences the overall performance of DC micro-grid is analysed in terms of system reliability and energy efficiency.A comprehensive performance evaluation model is established including the index system, the optimal combination of weight and gray comprehensive evaluation.Finally, a radiation DC micro-grid simulation model based on DC-DC sectionalizer is built in PSCAD/EMTDC to verify the effectiveness of DC-DC sectionalizer. Combining with the simulation data and evaluation model stated above, the example analysis about DC micro-grid overall performance is carried on in order to verify the effectiveness of evaluation model.