Is square wave inverter harmful to tvs?

The square wave inverter can be harmful to any device that has an AC to DC power supply, which almost every device does, because the slope of the incoming waveform is higher than usual and the interception point of the ripple waveform with the incoming waveform when the diode turns on can can high current transients in the diode. The can be minimized somewhat by using a series inductor to filter the high current transients.