Can a MOSFET generated high voltage (315v) pulse train be measured using a DMM in AC mode?
How to measure high frequency pulses on 1M DMM?

Since rise time and implied frequency is greater than DMM BW, it cannot measure.

One can measure peak voltage and average DC to obtain some meaning of the pulse duty cycle. This requires a series 1N400x diode and a plastic shunt cap of impedance about 1% of 1MOhm at f (PWM) to hold the voltage without excessive wire loop area to prevent stray induction and resonance.  This also minimizes the steady state load.

If can compute this value , then you can measure Vdc peak then without this circuit for Vdc using a 10k series R and 10x bigger cap.