With the fast development of renewable energy, the traditional power system is unable to utilize and integrate distributed energy resources (DER) easily. Microgrids can integrate micro sources, distributed storage devices and active loads altogether and play an important role to link customers and micro sources. In this paper, several common micro sources such as wind turbine, microturbine and solar PV are introduced with their operating characteristics. The mathematical models of these distributed generations (DG) and renewables will be analyzed and built in software PSCAD. In addition, PQ control strategy is applied on some sources to maintain a controllable active and reactive power output. The grid-connected micro-grid which contains a wind turbine generation system, a micro-turbine generation system and critical or non-critical loads was built up and the system level simulation was carried out for different operating scenarios.