Drive System#

Machine drives are sampled-data systems, consisting of continuous-time systems and discrete-time systems as well as the interfaces between them [1], [2]. The figure below shows a generic example system. The same architecture is used in motulator.

Block diagram of a sampled-data system

Block diagram of a sampled-data system. Discrete signals and systems are shown in blue, and continuous signals and systems are shown in red.#

The continuous-time system (named mdl in Examples) is the model of a physical machine drive system, typically consisting of a machine, mechanics, and power converter. The continuous-time system may have external inputs, such as a load torque.

The discrete-time controller (named ctrl) contains control algorithms, such as the current control and speed control. The reference signals could be, e.g., the speed and flux references. The feedback signal \(\boldsymbol{y}(k)\) typically contains the measured DC-bus voltage and stator currents.

Digital control systems typically have a computational delay of one sampling period, \(N=1\). The PWM block shown in the figure models the carrier comparison, see more details in Converters. The carrier comparison is implemented in the class motulator.drive.model.CarrierComparison. If the switching ripple is not of interest in simulations, the carrier comparison can be replaced with zero-order hold (ZOH).

References