EMS self consumption

Purpose:

The purpose of this function is to keep the electricity bill low by making sure that the grid meter is 0W at all time.

Setup:

In the scenario above, the load is 10 kW, the PV produces only 2 kW, therefore the grid import is 8 kW. When the EMS is set to self consumption, its task is to bring the meter power to 0W. To achieve so, the EMS will control the inverter active power set point to +8 kW to provide to the load. This means that the inverter will discharge the battery with 8 kW if possible.

This mode will drain the battery soc at some point therefore the EMS-cloud needs to schedule this mode properly and take battery recharge/recovery into account.

Implementation:

In practice, using the above formula to calculate the inverter active set point (=P_grid-P_pv) is inaccurate and may lead to static errors. Therefore a common way to implement this mode consists in using a PID where the set point is gridMeter_power=0. The error calculation is therefore e = P_grid-P_pv. This error is then fed into the PID for correction.

Emulation:

To simulate this scenario one can create a constant PV power (can be constant 0W) and have a variable load with peaks. The EMS shall follow these variations and make the grid imports close to 0W at all time.