Micro-grid is a system of load and composed of micro-power, which provides electricity and heat conversion while; micro-grid power mainly by internal power electronic device responsible for energy conversion, and provides the necessary control; microgrid relative external manifestations of a single large grid controlled unit can meet the power quality and power users of safety requirements.
- The Consoitium for Electric Reliability Technology Solutions (CERTS)
The Smart MicroGrid is an independent micro electricity distribution system. It is composed of micro energy source (an electricity generation unit which generates power lower than 100 kW, including photovoltaic, wind, biomass, wave and combustion turbine), load, transmission and distribution lines, energy storage device, energy manage system, control unit, communication system and smart relay protection device.
Smart microgrid combines an electricity generator, a load, an energy storage device and a control device, forming a single controllable unit and providing both power and heat to users at the same time. They are connected at the user's side, with the characteristics of low cost, low voltage and low pollution. Microgrid can be interconnected with a bulk power or run independently without the major system when electrical grid failure occurs or when necessary. It also plays a double role: it is the "cell" controlled by the electric power system to public electricity companies. For example, this "cell" can be controlled as a simple adjustable appliance, and can react to meet the need of the transmission system in a few seconds. Microgrid also acts as a customised power source, to satisfy various needs of users, such as increasing the reliability of local electricity supply, lowering the loss of electricity feed, supporting local voltage, improving efficiency by using waste-heat, adjusting voltage sag or acting as a non-stop power supply.
Properties of smart microgrid include strong, self-recovering, compatible, economical, integrating and optimising.
When major disturbance and failure occurs, the grids can still provide electricity for users and will not have a large scale power cut. The grid can still run safely under natural disasters and extreme weather conditions, or damages caused by human power. It can also guarantee safety of information and prevent damage caused by computer virus.
It is able to access and analyse safety level instantly and continuously. It has a powerful warning control system and the ability to prevent & control error. It can also identify and quarantine failures, and conduct self-recovery.
It supports the correct and reasonable access of renewable energy source, and also suitable for the access of distributed electricity generation and microgrid, greatly enhancing the managing function of the demand side, thus enabling a highly effective interaction between the supplier and users, and meeting the various needs of the users.
It supports the development of the electricity market and trading, enables a rational resources allocation, decreases the wearing of electric grid, increases the efficiency of energy usage and provides electricity which is affordable to users.
It enables the integration and sharing of electric grid information, and applies a unified platform and model, achieving standardised and refined management.
It optimises the usage of resources to lower investment cost and maintenance cost.