Gate drivers for wind power and light rail
Power Integrations has expanded its line of iScale power module drivers for wind power and light rail applications.
“The iFLEX-LT is specifically designed for wind power and renewable applications,” said Thorsten Schmidt product marketing manager at Power Integration. This supports six 1700V EconoDUAL 3 IGBT modules in parallel with simultaneous switching for current sharing to avoid thermal issues, up from four in the first generation.
This gives more design freedom as the isolated master controller is separate from the modules, which each have adapted iScale IFlex gate driver ASICs to generate the 15V control voltage for the 1700V, 20A power modules. These are connected by a low power digital cable to synchronise the switching. This separate control line avoids cross currents from the emitter that can lead to oscillations and interfere with the driver signals with a 20ns variance in command signal propagation delay at 5kHz.
“Dynamic and static current sharing is critical for robust operation of modules arranged in parallel. For the same power output, systems using SCALE-iFlex LT require just five parallel modules
whereas competitive approaches need six,” he said. “This substantial saving of cost and complexity is achieved by guaranteeing less than 20 ns of variance in turn-on and turn-off commands between modules and less than 20 A of variance between modules when conducting the rated 600 A. This allows the modules to operate reliably without current derating.”
Overvoltage protection with advanced active clamping gives the system designers more margin.
Schmidt points to the growth in wind power predicted to rise to over 2000 turbines generating 2TW in 2030 and over 6000 turbines in 2050 generating 6TW.
The first controller will support 1700V and 1200V IGBT modules starting with Infineon in series production late Q4 21, followed by modules from Mitsubishi, ABB and Fuji.
For light rail, Power Integrations has combined a controller with a single module.
The iFlex Single is a 100 x 140mm module that is 44mm high for trams and light rail.
“There was a clear mechanical requirement for the gate driver on the module,” said Schmidt. “We combined with integrated module controller controller (IMC) and module adapted gate drive (MAG) as a stack with the 2500V area isolated from the 15V gate drive.”
The high voltage housing around the driver that isolates the boards uses the CTI600 transformer housing material that module makers use, and PI works with an external company for this.
“There is 3.3kV reinforced isolation on the IMC and 1.7kV on the MAG isolating one channel from the other,” he said. The interface to the single module is electrical, although a fibre optic version is planned.
The initial module uses IGBT power transistors although a silicon carbide version is on the roadmap, says Schmidt. “On our roadmap its an assembly variant with different gate voltages so its easily addressable,” he said.
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