Jobourton’s Community Health Care Centre’s low voltage distribution boards are currently being built by Switchboard Manufacturers JHB. The facility will use a Tesla Microgrid to supply the facility with a reliable source of power if the grid supply were to fail.
The Tesla Microgrid turnkey solution has been used in many different environments around the world to supply reliable off-grid power to a vast array of different facilities.
[A typical PV array.]
What is the Tesla Microgrid?
The Tesla Microgrid is a turnkey solution provided by Tesla to enable a facility the capability of creating its own independent power grid, called a microgrid. The microgrid provides power with the use of a diesel generator, PV arrays and Tesla’s own Powerpacks which operate as battery supplies. These systems provide reliable power solutions to facilities which either have limited or no access to grid based power supplies.
The Tesla microgrid achieves this with the use of a set of controllers which monitor the power quality of the grid supply, generator, PV array and Powerpack. When one or more of these supplies aren’t outputing the desired power, the other supplies take over to support the facility. These controllers thus ensure that there is a continuous supply of power even when grid based power fails.
[Block diagram representing the interactions between the Microgrid controllers and the Distribution board. Image created by Author]
The Proposed System
The proposed system to be built can be seen in the above image. A 200kVA diesel generator, a PV array of 28 panels and a Tesla PowerPack system will make up the supplies to the microgrid. The control system consists of the Islanding Controller, Microgrid Controller and the Site Master Controller. These controllers ensure normal operation of the microgrid.
The flow of control in the Microgrid
As can be seen in the block diagram above, the microgrid control is a fairly complex system. The islanding controller is responsible for cutting the grid supply when it detects that the grid supply is under-performing. The Islanding Controller establishes the microgrid by opening the Islanding MCCB. By opening this MCCB the facility is completely cut off from the grid supply. To re-establish the grid supply the Islanding Controller needs to first ensure that the microgrid voltage is synchronised with the grid voltage before engaging the Islanding MCCB. Equipment damage could incur if the voltages are not synchronised.
The Microgrid controller controls the generator and PV inverters. Thus, as the name suggests, the Microgrid Controller ensures that the microgrid is operating optimally. The Site Master Controller controls the entire power system and processes input from the Microgrid and Islanding controllers. The Site Master Controller also controls the Powerpack inverters and thus engages the battery supply when need be. The Site Master Controller also thus ensures that all the inverter outputs are synchronised with each other and the grid supply and that the power produced is of optimal quality.
The Distribution Board
The main distribution board shown in the diagrams above is similar in working to a solar distribution board, as the flow of power is in reverse to a normal distribution board. This is an important factor to note as certain circuit breakers and current transformers (CT’s) are direction sensitive. The distribution board takes the various power sources feeding into it and then feeds them all onto a single bus-bar. The bus-bar then feeds into eighteen smaller distribution boards which serve the various buildings of the Health Centre. The Main distribution board and the smaller distribution boards will all be made by Switchboard Manufacturers. The other systems in place are either provided by Tesla or by the supplier of the PV contractor.
Article by: Jannes Smit, 3rd year Electrical Engineering student at the University of the Witwatersrand.