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AC6 - Comparison Between Detailed and Simplified Models

This example shows the AC6 detailed model and the AC6 average model during speed regulation. The comparison is performed for normal condition and for inverter saturation condition.

O. Tremblay, L.-A. Dessaint (Ecole de technologie superieure, Montreal)

Description

This circuit uses two AC6 blocks of Simscape™ Power Systems™ library. It models a permanent magnet (PM) synchronous motor drive with a braking chopper for a 3HP motor. The first block is set to average value model and the second is set to detailed model.

For the detailed model, the PM synchronous motor is fed by a PWM voltage source inverter, which is built using a Universal Bridge Block. The average value model uses ideal voltages and currents sources to feed the PM synchronous motor. The speed control loop uses a PI regulator to produce the flux and torque references for the vector control block. The vector control block computes the three reference motor line currents corresponding to the flux and torque references and then feeds the motor with these currents using a three-phase current regulator.

Motor currents, voltages, speed, and torque signals are available at the output of the block.

Simulation

Start the simulation. You can observe the motor stator current, the rotor speed, the electromagnetic torque and the DC bus voltage on the first scope. The speed set point and the torque set point are also shown. On the second scope, the dq currents and voltages are displayed. Note that all signals are multiplexed to compare the two models.

At time t = 0 s, the speed set point is 2400 rpm and the full load torque is applied to the motor. Observe that the speed follows precisely the acceleration ramp.

At t = 0.7 s, the inverter is saturated due to insufficient inverter voltage. You can observe loss of current tracking which decreases the motor torque.

At t = 1.2 s, the speed set point is changed to -2400 rpm.

At t = 1.5 s., the deceleration ramp reaches the motor speed. The inverter comes back to normal mode.

At t = 2 s., the mechanical load passes from 11 Nm to -11 Nm.

At t = 3.15 s., the inverter is saturated due to insufficient inverter voltage. You can observe loss of current tracking which decreases the motor torque.

Finally, note how the simplified model reacts well compared to the detailed model.

Notes

To evaluate the speed gain of the average value model, see ac6_example_simplified and compare the simulation speed with ac6_example.

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