Sometimes we may see a DC ripple warning. In my experience DC Ripple warnings can come from a couple of different sources.
- Actual real DC Ripple that is a DC supply voltage variation at the Quattro or Multiplus terminals in sympathy with the inverter AC output waveform. The DC Ripple has a frequency of 100Hz for 50 Hz systems and 120 Hz for 60 Hz systems and may be caused by a relatively high battery cable resistance. It is not sinusoidal but it does have a fundamental frequency.
- DC Voltage variation that can be caused by something other than generating an AC waveform by the inverter. Causes could be multiple batteries in the battery bank with lots of BMS activity when fully charged or a heavy load of the DC system that causes what could be more accurately described a DC variation rather than DC Ripple, but presents as a DC ripple warning.
Both of these scenarios may present a DC Ripple warning. In the first case that warning is accurate but in the second case it is DC variation rather than DC Ripple as it usually does not have a defined frequency.
Perhaps the DC ripple measurement could have a simple band pass filter algorithm to separate these two distinct types of DC variation to better direct the engineering staff to the root cause of the problem.
I am not suggesting this is urgent or of pressing importance but if product improvements were being contemplated in the future to this parameter measurement the band pass filter idea I think has some merit as it can separate DC Ripple from DC Variation for improved fault finding.