Current control of permanent magnet synchronous machines-experimental and simulation study

The control structure of a PWM (pulse width modulation) inverter-fed sinusoidal synchronous motor commonly includes two or three current control loops. Simulation and experimental results for both structures are compared, and the influence of a neutral point voltage (NPV) feedback loop in connection with canceling homopolar error in the three-loop structure is discussed. The best two-loop results are obtained with a simultaneous limitation strategy and integrator control allowing NPV displacements. This solution is best suited for digital systems. It appears that in an analog control structure the three-loop structure should be preferred because the torque is controlled throughout a higher speed range because of NPV displacements.<>