In fact, off-grid inverter is a basis for the development of bi-directional inverter, bidirectional inverter is actually a combination of grid inverter and off-grid inverter technology characteristics, applied to the local power supply network or power generation systems and grid parallel occasions.

Such applications although not much, but because of the class system is a prototype of the microgrid development, in line with future distributed generation infrastructure and commercial operation mode, so technically belongs to the past and a role, that is, in the current grid applications and future role as a bridge between the local micro-grid applications.

In fact, in some of photovoltaic power converter development of faster, more mature countries and markets, the microgrid applications to families, small regional units start slowly developed. Meanwhile, the local government to encourage family unit development of local power generation, electricity storage, electricity network, priority to new energy generation for personal use, insufficient part taken from the grid.

Therefore need to consider more bidirectional dc to ac inverter control function and energy management functions, such as battery charge and discharge control, and network load / off-grid operation strategy and reliable power supply strategy. Summary, the bi-directional inverter more from the perspective of the whole system to play an important control and management functions, rather than a single only consider the requirements of the grid or the load requirements.

As one of the direction of development of the grid, the local power generation as the core to build new energy power generation and distribution, electricity network will be one of the ways that future micro-grid development. In this mode, the local micro-grid and the large grid to form an interactive relationship microgrid will no longer close to rely on a large grid run more to run independently, that the islands of the way in the running.

Reliable electricity to meet the region's security, priority, only wealthy in the local power or the need to take power from the external power grid, form and network operation mode. All aspects of technology, policy, and other conditions are not ripe, the micro-grid and no large-scale applications, only a small number of demonstration projects in operation, and these projects, and network operation mode of the majority.

Micro-grid inverter is a combination of the technical features of the bi-directional DC to AC Converter, also play an important grid management functions, is typical of the inverter, control and management of one machine for the integrated control of inverter. Assumes local energy management, load control, battery management, inverter, protection and other functions, and management functions with the completion of the entire micro-grid and microgrid energy management system (MGEMS), will build the core of the micro-grid system equipment.

Compared to grid-connected inverter and inverter technology development, has been out of a simple function of the inverter, and carries a micro-grid management and control functions, from the system level attention and solve some problems. Figure 2 shows the micro dot net project cooperation system configuration diagram, the system has some typical, is powered by diesel generators play basic unit of renewable energy generation as a supplement.

Inverter energy storage provided by the company, to provide bi-directional inverter, converter, battery charge and discharge, micro-grid management system to manage the entire microgrid contactor A, B, C are controlled by a micro-grid management system cut off non-critical load, according to the electricity supply in the island operation to maintain the safe operation of the micro-grid stability and load.