Buildings.DHC.Networks.Controls

Package of control blocks for distribution systems

Information

This package contains models for control of distribution networks.

Package Content

Name	Description
AgentPump1Pipe	Ambient network storage and plants agent pump control, developed for reservoir network
MainPump1Pipe	Main pump controller for 1 pipe networks, developed for reservoir network main circulation loop
Examples	District controller example models

Buildings.DHC.Networks.Controls.AgentPump1Pipe

Ambient network storage and plants agent pump control, developed for reservoir network

Information

Controller for balacing agents (i.e. reservoirs and plants) pump.

This controller decides to turn on or off the agent pump depending on the current net demand of the district if TRetDis > TSupDis cooling else heating and the temperature differential between the agent source temperature TSou and the agent inlet temperature TSouIn adjusted by the offset dToff. In particular the pump turns on : if heating and TSou - TSouIn - dToff > 0 or if cooling and TSouIn - Tsou - dToff > 0. Then if the pump is turned on a PID controller, by default used as P, controls the pump control input by using TSouOut as measurement and as setpoint TSou - dToff for heating or TSou + dToff for cooling. dToff can be considered the nominal value of the agent heat exchanger pinch point temperature difference.

References

Ettore Zanetti, David Blum, Michael Wetter Control development and sizing analysis for a 5th generation district heating and cooling network using Modelica, 2023 International Modelica conference proceedings.

Parameters

Connectors

Modelica definition

Buildings.DHC.Networks.Controls.MainPump1Pipe

Main pump controller for 1 pipe networks, developed for reservoir network main circulation loop

Information

Controller for the main circulation pump.

This controller adjusts the pump speed in order to reduce it, unless the water temperature at the mixing points after the agents in the district is too high or too low, as measured by the difference to TMin and TMax. In that case, the pump speed is increased to prevent the loop getting too cold or too warm. The control is as follows: Let TMixMin and TMixMax be the minimum and maximum mixing temperatures. If TMax-TMixMax or TMixMin-TMin is too small, the pump speed is increased. If the difference is larger than dTSlo, then the pump speed is set to the minimum speed yPumMin. This calculation is done for both, TMixMin and TMixMax. The actual pump speed is then the larger of the two pump signals. Therefore, the pump speeds are calculated as shown in the figure below.

Moreover, if the parameter use_temperatureShift is set to true, then the district loop temperature is adjusted by changing the mass flow rate of the pump to increase the overall efficiency if there is net cooling or net heating on the loop. Specifically, if the district heating or cooling loop is in net heating (cooling) mode, it may be favorable to increase (decrease) the loop temperature, which can be done by increasing the pump speed. Whether the loop is in heating or cooling mode is determined based on the temperature differences across the loop sources, which are the inputs TSouIn and TSouOut. Each heat source or sink needs to be connected to one element of these vectorized input signals. This net difference is then used with a PI-controller to determine how much the slopes should be shifted in order to increase the pump speed. The shift of these slopes is indicated by the arrows in the figure. Note that this controller must be configured to be slow reacting, as it requires the feedback from the district heating and cooling loop. Furthermore, if the parameter use_constantHeaTemShift is set to true, then a constant temperature offset offTMax is added when only heating is present, this determination is done by checking that the cooling demand for each energy transfer station via QCoo is close to zero. This mode can used by itself or in conjuction with use_temperatureShift.

For a typical usage of this controller, see Buildings.DHC.Examples.Combined.SeriesVariableFlow.

Parameters

Connectors

Modelica definition