Overvoltage protection of high power IGBTs in wind power converters under short circuit

Wind power has the largest development in renewable energy recently. Countries are asking more strict requirements for wind power generation system, like low voltage ride through capability; meanwhile, utility grid wants wind power generation system to do more, like separated active power and reactive power flow control, compensated harmonic and reactive power; also, from the wind power generation system itself, it wants a full control of the wind turbine in order to make full use of the wind power. With the demands above, a structure contains a permanent magnet synchronous generator, a full size AC-DC-AC power electronics converter and a transformer becomes the trend. So, insulated gate bipolar transistor (IGBT) becomes the designers´ choice. This paper is focused on the short circuit protection of IGBTs under extremely fault condition-short circuit. Short circuit failure mechanism is described; a cost-effective, close-loop and simple protection circuit is proposed to protect IGBTs from over voltage caused by turning off the short circuit current. Experimental result is proposed on a 750 kW 3 phase 2 level wind power converter.