low pass filter in spwm h bridge
Your inductor value and capacitor value seem OK (resonant at 2.9 kHz) and loading with 48.4 ohms (1000 watts on 220 VAC) should not be a problem.

But the devil is in the detail: -


Your inductor has too much series resistance
Your inductor is saturating
Your H bridge is incapable of delivering 1000 watts efficiently
Your H bridge bus voltage is drooping under load


Here's a bode plot so you can see it should be OK: -





The red curve tells you that the frequency response is flat in the 50 Hz area and that you get "as-expected" roll off of the PWM artefacts above 3 kHz.

Picture source.

With perfect components there should be very little attenuation at 50 Hz