I follow how you are making the 350 volt DC source well enough but the concern I have is that with solar and wind your available input power is highly variable which is what I found is the least understood or most overlooked part by people wanting to design grid tie inverters.
In a typical stand alone power inverter it gets its input power from a battery or similar DC source that is relatively stable and has minimal voltage drop regardless of the range load demand put on it.
However with solar panels and wind power that source is not the least bit stable or constant both in voltage or available current which is where I have had difficulties understating why anyone would want to try and create a stable rail voltage like you are doing at 350 VDC to drive a grid tie system from an inherently unstable power source then go through the additional efforts to try to rematch those variable levels of available input power to inverter circuit and feed it back from there.
Going from a variable input power source to constant level back to a output that has to be forcibly controlled to keep it properly proportioned in reference to the primary input source is not necessary and adds a middle stage that is not needed in my opinion.
The method I have found to be the simplest and easiest to work with is to let the middle stage rail voltage, the 350 volt level in your case, simply float in relative proportion to the available input voltage and power opposed to trying to keep it at a constant voltage and then try and vary the output power being fed back to the grid from that.
By eliminating the control loop that tries to produce a constant 350 volt middle rail voltage, peak voltage limiting at this stage may be necessary though, you can also eliminate part of the output stage control loop that has to be referenced to the input source. Both circuit parts counts drop and complexity drop while picking up some efficiency.
If you are planing to use a SMPS type first stage to boost your input voltage up and provide line isolation, good practice for safety, you can set up your control circuit to basically float the mid point circuit voltage while still using your PWM wave form shaping in the output stage to get a clean and peak current limited/controlled waveform matching effect without having to do any referencing to the input power stage. If that makes sense.
Basically you run it as two independent inverter stages. the first one does your primary voltage step up and isolation duty and the second one does all of the line end synchronizing, waveform shaping and power switching duties without concern over the input power source fluctuation other that simply being told when to connect and disconnect from the mains lines.