DC Voltage Controller

Discrete-time DC voltage PI control with feedforward zero cancellation and integral anti-windup

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Libraries:
Simscape / Electrical / Control / General Machine Control

Description

The DC Voltage Controller block implements discrete-time PI-based DC voltage control. The block can implement zero cancellation in the feedforward path. To avoid saturation of the integral gain, the block can implement anti-windup gain.

Equations

The equation that the DC Voltage Controller block uses to calculate the control signal is

$control=\left(K_p+K_i\frac{T_{s}z}{z-1}\right)\left(v_{ref}-v\right),$

where:

• control is the control signal, which is expressed as a duty cycle or a current.

• K_p is the proportional gain.

• K_i is the integral gain.

• T_s is the sample time.

• v_ref is the reference voltage.

• v is the measured voltage.

The PI control calculation yields a zero in the closed-loop transfer function. To cancel the zero, the block uses this discrete-time zero-cancellation transfer function:

$G_{ZC}\left(z\right)=\frac{\frac{T_s{K}_i}{K_p}}{z+\left(\frac{T_s-\frac{K_p}{K_i}}{\frac{K_p}{K_i}}\right)}.$

To avoid saturation of the integrator output, the block uses an anti-windup mechanism. The integrator gain is then equal to

$$K_i+K_{aw}\left(contro{l}_{sat}-contro{l}_{unsat}\right),$$

where:

• K_aw is the anti-windup gain.

• control_sat is the saturated control signal, which the block calculates as $contro{l}_{sat}=\text{min}\left(\max \left(contro{l}_{unsat},contro{l}_{min}\right),contro{l}_{max}\right),$

  where:

  • control_unsat is the unsaturated control signal.

  • control_min is the lower limit for the control signal.

  • v_max is the upper limit for the control signal.

Ports

Input

vRef — Reference DC voltage

scalar

Desired DC output voltage for the plant.

Data Types: single | double

v — Measured DC voltage

scalar

Measured DC output voltage for the plant.

Data Types: single | double

Reset — External reset

scalar

External reset signal (rising edge) for the integrator.

Data Types: single | double

Output

Control — Control signal

scalar

Control signal, control, expressed as a duty cycle or a current.

Data Types: single | double

Parameters

Proportional gain — Proportional gain, K_p

0.1 (default) | positive scalar

Proportional gain, K_p, of the controller.

Integral gain — Integral gain, K_i

50 (default) | positive scalar

Integral gain, K_i, of the controller.

Anti-windup gain — Anti-windup gain, K_aw

1 (default) | positive scalar

Anti-windup gain, K_aw, of the controller.

Control action upper limit — Upper limit for the control signal, control_max

1 (default) | positive scalar

Upper limit for the Control output signal. The value must be greater than the value of the Control action lower limit parameter.

Control action lower limit — Lower limit for the control signal, control_min

0 (default) | non-negative scalar

Lower limit for the Control output signal.

Sample time (-1 for inherited) — Block sample time

-1 (default) | positive scalar

Time, in s, between consecutive block executions. During execution, the block produces outputs and, if appropriate, updates its internal state. For more information, see What Is Sample Time? and Specify Sample Time.

If this block is inside a triggered subsystem, inherit the sample time by setting this parameter to -1. If this block is in a continuous variable-step model, specify the sample time explicitly using a positive scalar.

Discretization sample time — Sample time for discretization

0.001 (default) | positive scalar

Time, in s, between consecutive discretizations.

Time constant voltage filter — DC voltage filter time constant, τ

0.001 (default) | positive scalar

Time constant, τ, for the DC voltage filter.

Dependencies

The Time constant voltage filter parameter is only visible when the Filter DC voltage checkbox is selected.

Enable zero cancellation — Feedforward zero cancellation

off (default) | on

Option to use zero cancellation on the feedforward path.

Dependencies

If you select the Enable zero cancellation option and set Sample time (-1 for inherited) to -1, the Discretization sample time parameter becomes visible.

Filter DC voltage — DC voltage filter option

on (default) | off

To enable the filter on voltage measurement path, select the checkbox. To disable the filter, clear the check box.

Dependencies

The Time constant voltage filter parameter is only visible when the Filter DC voltage check box is selected.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a