Microgrid - basics, structure, advantages, disadvantages

What is the Microgrid?

The microgrid is a small-scale power supply network that is designed to provide power for a small community with a local power generation unit. The microgrid connects both power generation and the utility grid thus preventing power outages.

Micro-grids micro-grids need to be incorporated into the electrical supply system. It helps to balance out supply and demand and make the system more flexible and reliable.help balance out supply and demand and make the system more flexible and reliable. Excess power after local use can be sold to the utility grid, Micro Grid consists of Fuel cells, Microturbine, Reciprocating engines, wind power and PV array systems.

Microgrid general Structure:

The microgrid has mainly two steady states of operation, grid-connected operation and is landed. It also has two transient states, corresponding to the transitions between these steady-states. During all these four conditions it must remain stable and maintain grid code requirement.

  • Additional hardware and software are required to control the voltage power and flow in the aggregate system to produce the improved behaviour required of a microgrid.

  • The connection interface (CI) to the utility network is something is like a circuit breaker, although solid-state switches and also back-to-back power electronic inverter.

  • The selection numbered as 2 in th figure is energy absorption and injection capability is usually required to balance power flows at the onset of Microgrid islanding.

  • Energy storage could also be used to control the net power flows to and from the utility in the grid-connected mode, allowing the Microgrid to behave as a ‘model’ citizen, capable assisting stable network operation by providing improved power quality and voltage control.

  • The characteristics of load can determine the requirement for energy storage. Loads are shown as numbered 3 to 7 in the figure. Local energy storage in conjunction with a power electronics interface.

  • The central control of the system is shown as number 8 - 1. It functions to regulate the instantaneous phase voltages and currents at the point of coupling. The communication is by the means of the telecommunication line, a signal modulated to the microgrid or a signal superimposed on the network voltage.

Advantages of microgrid:

  • Ability to disconnect from utility grid during disturbance and operate independently

  • It reduces demand on utility grid thus prevents grid failure

  • We can use both electricity and heat energy so that over all efficiency increases

Disadvantages of microgrid:

  • Voltage ,frequency and power quality should be at acceptable limits

  • Requires battery tanks to store which requires space and maintenance

  • Resynchronization to utility grid is difficult

  • Protection is difficult