Automatically identifying the new equipment after its integration and adjusting operation strategy to realize "plug and play" functionality are becoming essential for micro-grid operations. In order to improve and perfect the micro-grid "plug and play" function with the increased amount of equipment with different information protocols and more diverse system applications, this paper presents a solution for adaptive micro-grid operation based on IEC 61850, and proposes the design and specific implementation methods of micro-grid "plug and play" function and system operation mode conversion in detail, by using the established IEC 61850 information model of a micro-grid. Actual operation tests based on the developed IED and micro-grid test platform are performed to verify the feasibility and validity of the proposed solution. The tests results show that the solution can automatically identify the IEC 61850 information model of equipment after its integration, intelligently adjust the operation strategies to adapt to new system states and achieves a reliable system operation mode conversion.

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Here, a minimum resonant capacitor design approach is proposed for the insulated-gate bipolar transistor (IGBT)based high-power LLC resonant converter to improve its comprehensive efficiency in the electric vehicle (EV) battery charging application. The mathematical model of LLC resonant converter is established by using the first harmonic approximation (FHA) method. Then, the switching losses of IGBT-based high-power LLC resonant converter are analysed. Also, the relationship between predominant turn-off losses and turn-off current of power device IGBT is derived. To improve the comprehensive efficiency, the minimum resonant capacitor is proposed to reduce the turn-off losses, avoiding complex control or auxiliary circuit. Finally, the proposed approach is verified by a 2 kW LLC resonant converter prototype with 690 V DC input voltage and 75-150 V DC output voltage. Experimental results show the comprehensive efficiency of the prototype is up to 93.7%. Fig. 1 High-power EVs battery charger and its charging profile (a) Typical structure of the high-power EVs battery charger, (b) Simplified four-step charging profile of lead-acid battery IET Power Electron.

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