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

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... plementation 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. Energies 2015, 8 4456 photovoltaic system (PV), energy storage devices, and controllable loads, and provide two kinds of operation mode, including autonomous mode and grid-connected mode. Due to their energy management and operation optimization technology, micro-grids can be used to enhance the reliability of power supplies, realize efficient energy utilization, and improve the renewable energy integration capability [2] [3] [4] . At present, there are many types of equipment in micro-grids, including DERs, monitoring devices, and protection devices with different information interfaces and communication protocols. Influenced by some uncertain factors such as complicated operation scheduling, and intermittent fluctuations in renewable energy power, these equipment may be put into operation or shut down frequently. If a large amount of equipment is put into operation with multiple protocols, supervisory control and data acquisition systems (SCADAs)/energy management systems (EMSs) cannot automatically identify the device characteristics, or adjust operation strategies to adapt to new system states. Therefore micro-grids need a "plug and play" function to reduce the time of system configuration during the equipment integration to improve the system integration efficiency [5] . On the other hand, micro-grids may convert their operation modes, such as conversion from the autonomous mode to the grid-connected mode and vice versa according to the operation requirements, and need fast and reliable control of the diverse equipment during the conversion to ensure the stable operation of the micro-grid. Therefore, to establish a standardized information system with "plug and play" functions and rapid information exchange, and further effectively manage the equipment, has positive significance for micro-grid operation. IEC 61850 adopts the object-oriented modelling technology and flexible communication architecture, and provides a standardized system language, semantics, service, protocol and architecture, to meet the requirements of interoperability and extendibility for a variety of applications [6] . IEC 61850 is becoming an effective solution for information modelling and micro-grid "plug and play" function with reduced complexity and cost of system integration. Besides, due to its real-time data transmission and publish/subscribe mechanism, IEC 61850 can also support the fast control to realize the operation modes conversion of micro-grids. At present, the research around IEC 61850 application in micro-grids provides the related information model and implementation methods of "plug and play" functions for information modelling and information mapping of typical equipment involving PV, fuel cells, WP, and electric vehicles (EVs) [7-9], design of intelligent electronic devices (IEDs) as universal gateways in IEC 61850 bay level [10], micro-grid economic scheduling and hierarchical management based on IEC 61850 [11] . Reference [12] presents a plug-and-play cloud solution for next generation DERs, built upon the IEC 61850 standard for easy communication and cooperation between DERs and system operators, and the centralized configuration combined with a "plug and play" behaviour can control and monitor resources with little user interaction. Reference [13] introduces a new communication protocol mapping for IEC 61850 based on the devices' profiles for web services, to enable vertical automation in energy distribution networks, and the work makes it possible to achieve the "plug and play" capability so that information can be shared on a single network independent from any implementation or manufacturer. Reference [14] develops a new middleware platform for micro-grids integrating the device-level service oriented architecture based on IEC 61850, to significantly facilitate standards-compliant DER integration and micro-grid management, and the middleware mapping presented demonstrates the extensibility of IEC 61850 systems and provides proof-of-concept for "plug and play" DER systems.