Agreed, optocoupler with a suitable gate drive IC or circuit (depending on the MOSFET or IGBT). The gate drive circuit may itself need a few MOSFETs or similar in parallel to be able to supply enough current to rapidly charge/discharge the gate of your power semiconductor (which may have significant capacitance due to the size of the device). Usually the data sheet for the power semiconductor will include some suggested gate drive circuits, so start by selecting a suitably rated device and then read the data sheet.

TI have a nice paper published on this topic:

http://www.ti.com/lit/ml/slup169/slup169.pdf‎

Use optocoupler in gate drive circuit, it provides enough isolation..

Agreed, optocoupler with a suitable gate drive IC or circuit (depending on the MOSFET or IGBT). The gate drive circuit may itself need a few MOSFETs or similar in parallel to be able to supply enough current to rapidly charge/discharge the gate of your power semiconductor (which may have significant capacitance due to the size of the device). Usually the data sheet for the power semiconductor will include some suggested gate drive circuits, so start by selecting a suitably rated device and then read the data sheet.

TI have a nice paper published on this topic:

http://www.ti.com/lit/ml/slup169/slup169.pdf‎

In case of using optocouplers we get a comparative large propagation delay. Take a look at the part "TRANSFORMER COUPLED GATE DRIVES" in the paper, recommended by Dr. D. Franklin.

http://blog.chinaaet.com/uploads/Blog_affix/files/6103169864159.pdf

see this tip, written by Dr. Ray Ridley.

Is difficult to get an opto-coupler for the voltage rating you are mentioning, I recommend you using plastic optical fiber, they already sell the emitter, and receiver, so basically you made your own opto-coupler, and since the fiber is made by plastic, you may add several meters to get that isolation.

The emitter I have used is the IF-E96 by Industrial Fiberoptics (DigiKey part number: FB128-ND), it basically has a light emitter diode LED inside. The plastic optical fiber (cable) is the 501232-3 by TE Connectivity (DigiKey part number: A1700-100-ND), the installation is simple, emitter and receiver have a screw-nut type adjustment mechanism, (you don´t need special equipment to cut the fiber like in the case of high speed optical fibers). The receiver is the IF-D96 by Industrial Fiberoptics (DigiKey part number: FB132-ND). Those are the elements I have use, you may take a look on digikey to get other similar components.

To supply the gate drive power some designs draw it from the dc bus or from the control supply through isolated dc-dc converters. For low/medium-power applications, a flyback converter often does the job.