There will be an SMPS circuitry inside the Charging Pod which will have some low-voltage threshold (for instance, let’s say 160V, then the Pod will not work if the Voltage from Diesel Generator falls beyond that or keeps on fluctuating). As long as the DG supplies acceptable voltage and frequency, it will work.
Having said that, I would like to say that all modern branded DG set (from 5kVA and above) engines are controlled by Microprocessor based ECU (Engine Control Unit) - The ECU will be mapped in a way that it will always throttle the engine to try to maintain the optimal RPM required by the Alternator - in the event Engine cannot maintain the required RPM, the ECU activates Error messages / LED notifications on the instrument panel and maybe even shut down the engine.