Beschreibung
Six-step modulation offers notable advantages over the conventional space vector pulse width modulation (SVPWM) in the flux-weakening region. It enhances the torque capability of the machine and guarantees maximum power performance by maximizing battery voltage utilization. Moreover, it enhances the system efficiency by reducing the phase current required for flux weakening and minimizing switching losses. This thesis introduces an enhanced Deadbeat Flux Vector Controller (DBFC), as a one single control strategy capable of operating interior permanent magnet synchronous machines (IPMSMs) across the entire torque-speed range. Stable operation across the complete voltage modulation range, including SVPWM, overmodulation (I and II), and six-step, is achieved through precise tracking of various flux trajectories. DBFC enables a continuous and seamless transition between the different operating regions, where the modulation index varies linearly with speed in the constant torque region. With this proposed strategy, undesirable torque dynamics, stability problems, and increased computational efforts, associated with the use of multiple control laws, are completely avoided. A time-optimal torque control algorithm is developed to achieve the fastest possible torque response, significantly reducing the settling time, particularly when operating at the voltage limit (six-step). The torque can be controlled with high accuracy and high robustness to machine parameter variations. The proposed controller offers significant advantages over conventional Field-Oriented Control (FOC) and it is simpler to implement. Simulation and experimental results confirm the effectiveness of the proposed strategy, which is tested on a high-power, high-performance automotive traction machine.
