This use case is describing BEMS control of DERs(Distributed Energy Resources) and HVAC(Heating, Ventilation and Air Conditioning) equipment in a commercial building in both islanding mode and connected mode.
In the first scenario, BEMS predicts profile of PV output, thermal load and electric load of the building based on weather forecast information and past actual performance data. Based on these load prediction and DR signals, BEMS makes an operation schedule for DERs and HVACs that optimizes electric demand of the building (minimum cost, minimum CO2 emission, etc.).
In the second scenario, when BEMS receives a DR signal for demand reduction during scheduled operation, BEMS adjusts the demand power by controlling DERs and HVACs within the allowable range that meets the DR request.
In the third scenario, when BEMS receives a DR signal for islanding operation or detects system power-failures in a distribution line during the state of the scenario 2 operation mode, BEMS switches the building-side system from connected mode to islanding mode. While operating in this mode, BEMS controls the DERs in order to stabilize the voltage and frequency in the islanding area. Once conditions for restoration have been achieved, the system returns to connected mode.