Documentation

Speed Controller (Scalar Control)

Implement speed-controller model for scalar controlled AC drives

Library

Electric Drives/Fundamental Drive Blocks

Description

The Speed Controller (Scalar Control) block models a PID speed-regulator model for AC machines used in scalar-controlled (Volts/Hertz) drives. The output of the PID regulator is the machine slip, which is added to the machine speed to obtain the reference frequency of the inverter. To keep the machine Volts/Hertz ratio constant, the reference frequency also generates the reference voltage of the inverter.

Parameters

Proportional gain

The PID controller's proportional gain. The default value is 9.

Integral gain

The PID controller's integral gain. The default value is 10.

Volts/Hertz ratio (Volts/Hz)

The proportionality constant between the stator line-to-line RMS voltage and frequency, in volts/hertz. The default value is 3.2.

Zero speed crossing time (s)

The delay at zero speed, in seconds, to eliminate the machine air gap residual flux. The default value is 0.4.

Sample time (s)

The speed-controller sampling time, in seconds. The sampling time must be a multiple of the simulation time step. The default value is 100e-6.

Base speed (rpm)

Base speed of the AC machine, in rpm, typically equivalent to the nominal operating speed. The default value is 1800.

Reference ramp speed (rpm/s) [Deceleration, Acceleration]

The maximum rate of change of the speed reference to keep the machine's currents within rated values. The default value is [-1800,1800].

Low-pass filter cutoff frequency (Hz)

The speed measurement first-order filter cutoff frequency, in hertz. The default value is 100.

Frequency limits (Hz) [Minimum, Maximum]

The minimum and maximum reference frequency limits, in hertz. The default value is [0.05,120].

Voltage limits (V) [Minimum, Maximum]

The minimum and maximum reference voltage limits, in volts. The default value is [10,180].

Saturation (Hz) [Negative, Positive]

The PI controller maximum negative and positive output, in hertz. The default value is [-30,30].

Pairs of poles

The number of pole pairs. The default value is 2.

Base​ ​sample time (s)

​The time step used for the simulation, in seconds. The default value is ​2​e-6.

Inputs and Outputs

N

The speed of the machine, in rpm.

N*

The speed reference of the machine, in rpm.

Freq*

The reference frequency of the inverter.

Volts*

The reference voltage of the inverter.

dir

Motor speed sign (-1 for negative speed, 1 for positive speed, or 0).

ctrl

A bus containing these measurements:

  • Voltage reference — In volts.

  • Frequency reference — In hertz.

  • Error — The speed error (difference between the reference and actual speed).

  • Speed reference — In rpm.

Examples

The Speed Controller (Scalar Control) block is used in the AC2 block of the Electric Drives library.

References

[1] Bose, B. K. Modern Power Electronics and AC Drives, NJ: Prentice-Hall, 2002.

Introduced in R2015b

Was this topic helpful?