# DC bus correction for inverter VFD via PWM modulation

This is a question concerning an inverter circuit without PFC.

Single phase AC is rectified and pooled on DC bus capacitors. From there the DC voltage is modulated at 5kHz on 6 IGBTs, emulating sinusoidal waves of the required frequency, using an open loop V/F scheme.

Now assume the requested frequency is steady. Due to fluctuations on the AC input, DC bus voltage may vary from 280Vdc to 330Vdc. Which is the best way to modify the PWM signal in order to drive the load at the same power?

At the moment I'm adjusting the PWM duty cycle proportionately to the nominal DC BUS voltage (limiting the maximum adjustment up or downwards).

DutyAdjusted = DutyNominal * (DCBusNominal / DCBusMeasured)


Is that enough? Is the approach dependant on the type of load?