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Voltage Controller (DC Bus)

Implement DC bus voltage controller for thyristor bridge rectifier


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  • Voltage Controller (DC Bus) block


The Voltage Controller (DC Bus) block represents a PI DC bus voltage regulator model for a thyristor bridge rectifier.

The controller outputs the thyristor bridge firing angle (Alpha). This firing angle is typically used by a thyristor bridge firing unit to generate the gate signals needed to reach the desired DC bus voltage.

When the bridge rectifier reaches its operating limit and the DC bus voltage becomes too high, the controller outputs the duty cycle (P_chop) for a braking chopper. The latter ensures that the DC bus voltage is kept within its upper and lower limits. During this operating mode, the braking chopper control signal (Bctrl) cancels out the integral gain of the PI controller. The integral gain is not needed due to the high dynamics of the braking chopper.


Integral gain

The PI controller's integral gain. The default value is 0.1.

Proportional gain

The PI controller's proportional gain. The default value is 0.01.

Low-pass filter cutoff frequency (Hz)

The DC bus voltage measurement first-order filter cutoff frequency, in hertz. The default value is 30.

Sample time (s)

The time step used for the simulation, in seconds. The default value is 1e-6.

Inputs and Outputs


The DC bus voltage set point for the thyristor bridge.


The braking chopper control signal (0 or 1).


The measured DC bus voltage.


The duty cycle of the braking chopper.


The thyristor bridge rectifier firing angle.


The measured DC bus voltage filtered.


A vector containing the following measurement signals:

  • Alpha (deg) — The thyristor bridge firing angle.

  • Voltage Error (V) — Difference between the DC bus voltage reference and the actual DC bus voltage (filtered).


The Voltage Controller (DC Bus) block is used in the AC1 block of the Electric Drives library.


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

Introduced in R2015b