Suppose I want to switch AC. I want to control (allow, prevent, or interrupt) current flow in either direction. SCRs won't do because I want to interrupt current, and I don't recall seeing many IGBTs or FETs that lack an antiparallel diode. Those few I have seen have been low-power and didn't have much of a spec for reverse-blocking.
Are there transistors or other solid-state devices that will do what I want? Or should I perhaps use two IGBTs in series with the directions reversed?
Voltages I'm interested in are on the order of 600VAC. Currents are 10-200 amps. Frequencies are 1-20 kHz.
Answer
Yes, hefty back-to-back MOSFETs (maybe) or IGBTs should do what you want. Driving them would require isolated gate drive circuits. The complexity will vary a bit depending on how quickly you want them to switch. IGBTs tend to switch a lot more lethargically, but are more suited for the ~1200V PIV type operation required in this application.
SCRs (and triacs) as, you point out, have to wait for a (current) zero crossing, and the high frequency operation you speak of (20kHz) means that they would tend to stay on due to the high dv/dt at the zero crossing.
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