Filter choice and EMI concerns for 10 A dimmer

Question

I need a power router to divert excess photovoltaic power into a water heater.

Context: Solar panels are connected to a grid-tied inverter. A smartmeter measures how much power the house draws, and the inverter uses this information to adjust its output power to compensate, resulting in zero average power drawn from the utility if there's enough sun. So this question is about AC not DC, I'm not looking for a solution to feed DC power to the water heater.

The goal is to use excess power without drawing from the grid. This is usually implemented with a dimmer. All required data is available over Modbus from the solar inverter and smartmeter, so this question is only about the style of dimmer to use for this application, not how to control it.

A popular choice is a triac dimmer, which draws distorted current from mains and makes a lot of noise.

Another option would be to use two back-to-back MOSFETs to make an AC switch, and PWM it at high frequency. This makes the AC current more sinusoid-like, but the tradeoff is more HF noise.

The best option, which would be pulse density modulation using whole cycles, is unfortunately not available as the utility meter counts energy on a period by period basis and does not do net metering. So if available power is not enough to cover the full power of the heating element, it would result in importing energy from the grid, which would defeat the purpose.

This is a hobby project, so there is no plan to pass EMC certification.

Question:

What kind of filter can I use on both options (triac or PWM) to make this circuit "civilized" in regards to conducted EMI?

Here's a candidate filter for the triac version. It keeps di/dt drawn from mains at turn-on under 0.4A/µs. The 1mH inductor with 10A saturation current is a problem, but I've found a suitable core.

I'm not sure where to put the load either (after the filter or before like in this variant):

Answer 1

PWM at AC mains works same as any other, but you need bidirectional switches (e.g. anti-series MOSFETs), and can't use a catch diode, it has to be synchronous. You also can't use, like, obnoxiously large electrolytics for filtering the input or output; it has to be film caps, and with a cutoff frequency somewhere between F_mains and F_sw, suitable to get adequate attenuation of switching noise, without impairing line regulation through the converter. Most likely, gate drive will need to be isolated; anti-series pairs can be wired source-to-source, so two such drivers will be required. Control can be open loop (fixed percentage or voltage-mode PWM), but current limiting should still be employed to protect the switches.

It also needs to handle the full range of mains transients, so, consider 1200 V Si or SiC MOSFETs, and a MOV at the inlet. Or if adequate protection is available in the grid-tie inverter, and an auxiliary outlet is provided after such protection, that might save a little bit of work. Do not modify approved equipment, or do so entirely at your own bodily, property and financial risk.

If a common DC (solar input?) rail is available (again, in a safe manner, preferably without modifying equipment), a load there would be much simpler.