Enhanced Control Structure for Servo Drives with Adaptive PWM

The PWM switching frequency significantly impacts the performance and power dissipation of electrical servo drives. In many fields of application, such as industrial automation, static PWM frequencies are typically used. The novel adaptive PWM approach dynamically adjusts the PWM frequency according to process requirements of manufacturing processes. By adapting the PWM frequency, switching losses and the overall energy consumption of servo drives can be reduced. Changing the PWM frequency at runtime requires enhancements to the control structure for dynamic parameter adjustments and a stable operation of the controllers. To validate the enhanced control structure, an experimental evaluation of the performance at different, dynamically changing PWM frequencies is presented. It is shown that the controller operates with the expected behavior at different frequencies but that there are disturbances at the moment of adjusting the PWM frequency. Non-linearities are identified as a major source, including those caused by IGBT-deadtimes. A simple compensation mechanism is integrated in the enhanced control structure as a proof-of-concept, resulting in an almost complete cancelation of disturbances at the moment of adjusting the PWM frequency.