Siemens 6SR41 series - The Control Modes

Application and Operation
6.2 The Control Modes
Product User Manual
108 Operating Instructions, Version AE 12/2009, A5E01454341C
6.2 The Control Modes
Harmony drives use vector control to control induction and synchronous motors. Vector
control provides a framework that is simple to implement, but performs nearly as well as a
DC motor. Figure "Block Diagram of Vectors Control Algorithmus for Induction and
Synchronous Motor Control" shows a simplified representation of the vector control algorithm
implemented in Harmony drives. The basic components of vector control are:
1. Motor model: determines motor flux and speed.
2. Current regulators: these regulators are referred to as the inner loops.
3. Flux and speed regulators: these regulators are referred to as the outer loops.
4. Feed-forward (FF) compensation: improves the transient response of torque loop and flux
loop.
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Figure 6-2 Block Diagram of Vector Control Algorithms for Induction and Synchronous Motor Control
The motor model uses measured motor voltage and estimated stator resistance voltage drop
to determine stator flux amplitude, motor speed, and flux angle. This allows stator resistance
compensation to be automatic. A simplification of motor equations is obtained by
transforming the 3-phase AC quantities (which are referred to as being in a stationary
reference frame) to DC quantities (that are in a synchronously rotating or DQ reference