Final Thoughts

It is the same, but not exactly

 

An electric power grid is a complex system for delivering electric power from different sources to individual consumers over an interconnected transmission and distribution system, while maintaining the stability of the system, the quality of power and balancing the load and the generation at every moment in time.

 

This simplified definition of the electric power grid can be used at every level of the system - from the megagrid to the nanogrid. So with the constantly increasing penetration of renewable distributed energy resources and their use in microgrids in order to improve the resiliency of the system during disturbances it will look like we have a simple case - use the knowledge that we have from more than a hundred years of electric power grids, but at the lower scale of the microgrids.

Well, unfortunately it is not that simple. What we are used to is the synchronous generators based grid operation where the voltage and frequency is the result of the interaction between the generation and load over the transmission and distribution networks. In case of wide area system disturbances that result in unintentional islanding the frequency and voltage measurements can be used as the criteria to perform load or generation shedding to restore the balance in the island.

In an urban environment today we see large solar photovoltaic installations on rooftops, parking lots, side walls or any available surface exposed to the sun for long periods of time.

In case of disturbance when the microgrid is islanded from the system we face the challenges of a completely different mode of operation. Since PV solar systems do not generate power at the grid frequency, they need an inverter to interface with the microgrid. In the case of operation with connection to the power grid the system frequency is used as a reference. But once in an islanded condition this reference is lost. And this is when innovation needs to come in place in order to take full advantage of the available resources and maximize their use instead of shutting them down.

We need innovative solutions to deal with the constantly changing loads and generation that does not behave like the synchronous machines based systems that we know.   

Protecting your electrical assets? today and tomorrow