A 10 MW-class high-precision power supply was developed for the electromagnets of a large proton accelerator (J-PARC) . This power supply consists of an advanced self-commutated current-source type converter (ACSC) using IEGTs and a hybrid filter. The current ripple was less than 1×10-6, and the tracking error was less than ±0.5×10-4. With this power supply, the proton beam was successfully accelerated to 30 GeV, which is the target energy of the first stage of J-PARC.
