Microgrids are becoming increasingly attractive to consumers and as such in the future, a great number of them will be installed at consumer’s sites. In this situation, conventional distribution networks that accept distributed generation connections may face serious technical challenges when its control and protection functions become more complicated. This incurs a burden to the network operation and some technical limitations will appear when a great number of distributed generations are installed. One way of overcoming such problems, a micro grid system is formed to provide reliable electricity and heat delivering services by connecting distributed generations and loads together within a small area. A microgrid is usually connected to an electrical distribution network in an autonomous way and employs various distributed generation technologies such as micro-turbine, fuel cell, photovoltaic system together with energy storage devices such as battery, condenser and flywheel. Micro grids can cause several technical problems in its operation and control when operated as autonomous systems. This paper is a review of three technical challenges on micro grid with respect to voltage and frequency control, islanding and protection of microgrids.