Field Oriented Control (FOC) for a Permanent Magnet Synchronous Motor (PMSM)

Figure 1. FOC FOR PMSM BLOCK DIAGRAM

INTRODUCTION
Current industry trends suggest the Permanent Magnet Synchronous Motor (PMSM) as the first preference for motor control application designers. Its strengths, such as high power density, fast dynamic response and high efficiency in comparison with other motors in its category, coupled with decreased manufacturing costs and improved magnetic properties, make the PMSM a good recommendation for large-scale product implementation.

FIELD ORIENTED CONTROL (FOC)

In case of the PMSM, the rotor field speed must be equal to the stator (armature) field speed (i.e., synchronous). The loss of synchronization between the rotor and stator fields causes the motor to halt.
Field Oriented Control (FOC) represents the method by which one of the fluxes (rotor, stator or air gap) is considered as a basis for creating a reference frame for one of the other fluxes with the purpose of decoupling the torque and flux-producing components of the stator current. The decoupling assures the ease of control for complex three-phase motors in the same manner as DC motors with separate excitation. This means the armature current is responsible for the torque generation, and the excitation current is responsible for the flux generation. In this application note, the rotor flux is considered as a reference frame for the stator and air gap flux.
The control scheme for FOC is presented in Figure 1. This scheme was implemented and tested using the dsPACE ds1104 and 3-Phase Inverter Development Board, which can drive a PMSM motor using different control techniques without requiring any additional hardware.

Experimental results

Now, the results of the experimental test are presented. The current response of the system due to a step change in the current command are shown in Figure [2-9], respectively. 

As it is shown in these figures, the system has a good dynamic response.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8

Figure 9.

Software part

The dSpace programming has been carried out using Simulink. Most of the model is equal to the simulations. Only few parts have been changed, added or removed.

Special attention should be placed in the Simulation > Configuration Parameters. The next modifications should be done before running a real time application:

 Software part

The stop time is set‎to‎“inf”.

The‎solver‎type‎should‎be‎“Fixed-step”.

The solver is‎“ode1 (Euler)”.

The block reduction option in the optimization menu should be unmarked.

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