How do I successfully drive this MOSFET for a dump load resistor with a wind turbine?

Question

I am constructing an AC-DC Rectifier with dump load control for a wind turbine (see Schematic for info). The following use cases are required:

1. Rectifier rectifies AC into DC and provides energy to inverter, dump load is off

2. Rectifier rectifies AC into DC but the voltage produced is over 500V and thus PWM is used with a MOSFET to manage overvoltage and feather the load to the inverter

3. There is a grid outage and I need to isolate the circuit from the grid and then dump all the load to the dump load resistor to slow down the turbine

Solution 1: Use an enhancement type MOSFET to manage overvoltage. In the event of a grid outage have a UPS and this battery to power the MOSFET and ensure it is switched on: https://uk.rs-online.com/web/p/lead-acid-batteries/0597835?gb=s. Issues arise here with the involvement of having to use a battery thus increasing complexity to regulate the voltage for the microcontroller circuit and the MOSFET driving circuit.

Solution 2: Use a depletion type MOSFET so in the event of a grid outage and an inability to send signals from the microcontroller the depletion type MOSFET defaults to close and the switch (Q2) defaults to open to isolate it from the grid and take all the power. This solution would negate the necessity for a battery.

The turbine is specced for 6kW but as it may have to take all the load peak voltage with SF should be around 1000V and peak current should be around 20A hence the high specced MOSFETs.

Using an NC Relay would be a much simpler option but is not one we want to explore.

Note: the MOSFET Q2 will be a simple switch and not a MOSFET (I just couldn't find a switch. The capacitor creates a delay to avoid a voltage surge.

Answer 1

How do I successfully drive this MOSFET for a dump load resistor with a wind turbine?

My 1st suggestion allows the MOSFET to be driven from a ground referenced system: -

1. Derive a 15 volt supply from the wind turbine output using an isolated converter
2. That 15 volt supply need only be a couple of watts
3. Recom and Murata make converters that are suitable but,
4. They will need a steady DC supply input derived from the turbine AC
5. Next, use an opto-isolated MOSFET gate driver that is powered by the isolated converter
6. Many people make these types of devices (e.g. the FOD8343)
7. Use that to activate and deactivate the MOSFET

Or, derive everything from the MOSFET side. When an over-voltage looks likely to occur, the MOSFET can be activated for a period of time and clamp the problematic voltage.