TIDUEY6 April 2021
The traction drive subsystem is designed to drive an AC induction motor or some combination of interior permanent magnet synchronous motor (IPMSM) and synchronous reluctance motor (SynRM). High bandwidth field oriented control (FOC) scheme with dynamic decoupling is implemented with C2000 real-time control MCU together with field-weakening and over-modulation techniques to driver motor to industry-leading high speed up to 20,000 RPM, which can enable cost and weight reduction to the traction motor.
Traction drive system normally uses a variable reluctance (VR) resolver, which matches the pole count of the motor, to directly measure the electric angle of the rotor. Resolver to digital conversion (RDC) is required to measure position and speed using resolver signal. RDC is traditionally handled by a separate IC, such as PGA411-Q1. With C2000 MCU, RDC for high-speed traction inverter can be integrated into main control MCU, where the excitation generation can be handled with DMA without CPU involvement, and feedback is read through ADC and decoded with CPU.
A PSFB topology allows the switching devices to switch with zero voltage switching (ZVS) resulting in lower switching losses and higher efficiency. PCMC is a highly desired control scheme for power converters because of its inherent voltage feed forward, automatic cycle-by-cycle current limiting, flux balancing, and other advantages, which requires generating complex PWM drive waveforms along with fast and efficient control loop calculations. This is made possible on C2000 microcontrollers by advanced on-chip control peripherals like PWM modules, analog comparators with DAC and slope compensation hardware and 12-bit high-speed ADCs coupled with an efficient 32-bit CPU.