Reliable high-voltage power transmission

Insulated gate bipolar transistor (IGBT) modules are commonly used in VSCs for voltage switching applications. A short circuit in IGBTs causes high-voltage spikes that cause failure in stacked IGBTs, resulting in power blackouts and significant losses.

Backed by EU funding, the 'Universal failsafe IGBT package for robust power transmission' (UNIPACK) project developed an intrinsic fail-safe mechanism that fails to short circuit, thereby maintaining continuity of power transmission in all applications. The fail-safe IGBT module can operate at 4.5 kilovolts and 900 amperes.

The project exploited shape memory alloy (SMA) compositions for fail-safe components and transient liquid-phase jointing materials such as nano-silver. Other achievements were the development of test benches to characterise SMA compositions and the VSC device.

UNIPACK technology is a retrofit product. Together with the new-build market, this factor also opens up the replacement and maintenance market. The universal design of the UNIPACK device enables its operation in both stacked and non-stacked applications.

A number of different power transmission and distribution applications should benefit from UNIPACK technology. These include chopper converters for direct current (DC) traction motor drives, voltage source inverters for alternating current (AC) motor drives and rectifiers for AC-DC conversion in rail traction.

UNIPACK technology should offer much-needed confidence by ensuring continuity of power supply with the lowest possible losses. Efficient high-voltage switching should also enable the increased use of energy from renewable energy sources such as offshore wind farms with lower losses and lesser risks of power failure.