Updated: Sep 22, 2020
By Viduni Pathirana
Imagine a future where majority of the power is generated by distributed elements locally through Microgrids and on our rooftops, ultimately the world is able to achieve a net zero carbon footprint! In Australia, several Microgrid initiatives have been successfully completed such as the SwitchDin Microgrid project in West Australia, South Australian Produce Market (SAPM) Microgrid in South Australia and Monash University in Victoria to name a few.
In a Microgrid, there are several key operational aspects and their impacts that must be taken into consideration. One such operational aspect is the voltage and frequency fluctuations in the Microgrid. For example, if a Distributed Energy Resource (DER) is causing voltage or frequency fluctuations then the Microgrid must identify the DER and disconnect it from the system. Thus, voltage regulation and frequency regulation are critical in order maintain the system stability.
In the instant where the microgrid is on islanding mode, it may not be able to maintain the same frequency bandwidth as the main grid. Some devices may not operate with any frequency outside the nominal frequency range. For example, the Australian power system operates at 50 Hz ± 0.2 Hz range during normal operating conditions. Therefore, the microgrid design should satisfy the frequency trip limit as stated in IEEE 1547-2018 standards in an island mode. Furthermore, when in an island mode, a voltage control is required to maintain the voltage of the microgrid. Voltage fluctuations may occur due to loss of loads, unbalanced delivered and consumed reactive power (i.e. when the reactive power delivered by the source is less than the reactive power consumed by the load)
A Microgrid has a 3-tier hierarchical control structure. The voltage and frequency regulation is managed by both primary and secondary controls. Primary control adjust the fequency and the voltage real time of local devices. Secondary control maintains the voltage and frequency within normal operating limits.
To sum up, the energy industry is moving towards a more sustainable future and Microgrids are likely to play a more prominent role. However, in this journey many aspects should be considered, and voltage regulation and frequency regulations are just some of these. In my next blog, I will be focussing on Frequency Control Ancillary Service (FCAS).