Hello,
I'm currently in the process of building a solar power diverted to route surplus electricity to my 3kW immersion heater. So far I've made a triac phase cut dimmer which is wirelessly connected to CT clamps and AC voltage reference. It works okay but I'd like to implement a PWM IGBT dimmer to reduce EMI, acoustic noise and put a more uniform load on my inverter. There are two topologies I'm currently looking into, if you know of any other good ones please say.

I found some schematics online which show a rough idea of what I mean. I also read that PWM dimming can be used in conjunction with zero crossing detection to slightly improve efficiency, I don't understand why this is true? Surely the constant switching will cause all the losses, what difference does the phase make?
Topology 1) Rectified AC applied to the heater through one IGBT:
It appears that this topology is more popular, but I'm concerned about the high power dissipation in the bridge rectifier.
The schematic that I found shows a MOSFET instead of an IGBT, is there any significant benefits of using the IGBT besides its lower switching losses?
Topology 2) Two anti series IGBTs applying the AC directly to the heater where each body diode allows the opposite cycle to pass:
Will this topology result in an overall lower power dissipation?
Will a separate rectified power source be needed to driver the gates and is a driving ic necessary?

I'd also like to put more thought into the EMI filtering, is a single common mode choke sufficient?
I came across this image of the 4-Noks Power Reducer which appears to be topology 1, looking at the top filtering PCB I see several common mode chokes and capacitors, why are so many different sized chokes used? How do you go about selecting them?
