.Buildings.Controls.OBC.CDL.Reals.LimitSlewRate

Information

The block limits the rate of change of the input by a ramp.

This block computes a threshold for the rate of change between input u and output y as thr = (u-y)/Td, where Td > 0 is parameter. The output y is computed as follows:

• If thr < fallingSlewRate, then dy/dt = fallingSlewRate,
• if thr > raisingSlewRate, then dy/dt = raisingSlewRate,
• otherwise, dy/dt = thr.

Implementation

For the block to work with arbitrary inputs and in order to produce a differentiable output, the input is numerically differentiated with derivative time constant Td. Smaller time constant Td means nearer ideal derivative.

Revisions

• January 27, 2022, by Jianjun Hu:
  Renamed the block name from SlewRateLimiter to LimitSlewRate.
  This is for issue 2865.
• November 12, 2020, by Michael Wetter:
  Reformulated to remove dependency to Modelica.Units.SI.
  This is for issue 2243.
• April 21, 2020, by Michael Wetter:
  Removed final attribute on unit because if the input quantity is power, then the rate limit is units of power per units of time.
• March 2, 2020, by Michael Wetter:
  Changed icon to display dynamically the output value.
• March 29, 2017, by Jianjun Hu:
  First implementation, based on the implementation of the Modelica Standard Library.