Logs Offline !
The CUMon Logs have been taken off line whilst the new Energy diverter is developed.
Development Notes
The current software that has been developed with CUMon measures Current magnitude and does not need to worry about the current phase because it determines export and imports by cross-correlating the PV amplitude with the Grid Connection amplitude.
Inverters and CT coils
Inverters use CT coils or Modbus meters on their Grid Connections to determine the power flow to or from the the Grid
CT Coils can only measure current amplitude. You do not know the phase angle of that current . To measure whether the current is flowing in or out of your house you need a Voltage value to combine with the Amplitude value from the CT coil. With Normal Grid AC to an inverter you can combine the CT Amplitude with a Voltage reading to calculate this.
With CUMon we work with a CT coil that just requires to be clipped into the Grid AC connection and the orientation of the CT coil is not needed to be known because the Current flow is determined by the Cross Correlation to the PV current.
We have chosen an inverter that has a Modbus meter replacement option that allows an NRGDivert module to mimic the Modbus meter and control how the inverter perceives the virtual “Grid connection” and thus control whether power is diverted to battery or to house/Grid.
Progress so far
- We have successfully interfaced with Modus on the Inverter and have been able to control the Flow of power in and Out
- We have used a very basic control loop to divert energy to the battery
- We have supplied the house with power from the battery
Notes
- The inverter can be set in Charge the battery mode or charge Or power the House Mode
- The MODBUS meter supplies a varied interface with lots of data available but the Inverter only seems to read the bare minimum 3 registers of Reactive power
Problems
- We have to emulate reactive power and this is currently unknown by CUMon
- We have a control loop that is basic and gets lost easily
- The inverter “remembers” the power output state and continues to drive this even if the control loop fails
Conclusion
The process is possible and the concept has been proven with an engineering setup. The Control loop needs work but is feasible