Technology is rapidly driving the transition to smart grids. At the same time, micro-grid has been the new trend, driven by technological improvements and the aim of transition to the clean energy, in order to improve reliability and resilience of electrical grids. This article explains what is micro-grid is, and introduces the solution with grid-tied inverter and AC coupled inverter.
What is Micro-grid
A Micro-grid is a small-scale group of interconnected loads and distributed energy resources that acts as a single controllable entity with respect to the grid. It can operate in grid-connected or island mode depending on the connection state to the grid.
A micro-grid generally operates while connected to the grid, but it can also operate on its own and have the capability of keeping electricity producing for the systems connected to it in case of the grid power outage. A micro-grid might have number of connected distributed energy resources, such as solar, energy storage, wind turbines or traditional generator.
Background
Solar power as the most abundant renewable energy resource can be converted to electrical or thermal energy. Solar inverter is used to convert the DC energy produced by a solar panel into AC electricity. However, the commonly used grid-tied inverter is grid-dependant and work in accordance with the grid. The inverter will stop working when the grid is out of power. Regular grid failures can last up to long time, which requires to use alternative forms of energy. To date, diesel generators have been a traditional preferred backup solution. A hybrid micro-grid system utilizes a diversity of PV, diesel generator is an optimum way for saving fuel, reducing emissions and maintenance. And energy storage inverters can be integrated into the micro-grid system as a zero-emissions substitute for diesel generator.
Advantage of Micro-grid in PV+Storage System
Nowadays, the growing environmental problems and energy policy changes make the energy storage inverter very popular. Especially in some residential scenarios, the energy storage inverter will be used for the retrofit or expansion project to upgrade existing PV system to storage system. The AC coupled inverter and grid-tied inverter can form a typical micro-grid. In this Micro-grid system, when the
grid fails, the grid-tied inverter can still work under the micro-grid provided by AC coupled inverter’s off grid output. It helps to balance out supply and demand and make the system more
Advanced micro-grids enable the local power generation system to keep the local grid running, even if there is an outage of the utility grid. In addition, for some areas, where there is no connection to the utility grid, a micro-grid can still provide the power production.
Here is a typical topology of the micro grid
The commercial PV energy storage & power generation system is mainly used in commercial energy storage application scenarios in China and foreign countries. This system integrates PV and energy storage technologies to improve the ratio of “self-use first” of PV, reduce PV curtailment and achieve direct PV grid-connection. The system is designed with indoor and outdoor specifications so that it can meet the requirements for different installation environments, and its electric quantity can be configured as needed.
