Incorporating a load change penalty in central plant optimization

Patent metadata

Field	Value
Publication number	US-10101730-B2
Application number	US-201514634573-A
Country	US
Kind code	B2
Filing date	Feb 27, 2015
Priority date	May 1, 2014
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

An optimization system for a central plant includes a processing circuit configured to receive load prediction data indicating building energy loads and utility rate data indicating a price of one or more resources consumed by equipment of the central plant to serve the building energy loads. The optimization system includes a high level optimization module configured to generate an objective function that expresses a total monetary cost of operating the central plant over the optimization period as a function of the utility rate data and an amount of the one or more resources consumed by multiple groups of the central plant equipment. The optimization system includes a load change penalty module configured to modify the objective function to account for a load change penalty resulting from a change in an amount of the building energy loads assigned to one or more of the groups of central plant equipment.

First claim

What is claimed is:

1. An optimization and control system for a central plant configured to serve building energy loads, the optimization and control system comprising:
a central plant controller configured to receive utility rate data indicating a price of one or more resources consumed by central plant equipment of the central plant to serve the building energy loads at each of a plurality of time steps in an optimization period, the central plant controller comprising:
a load/rate prediction module configured to use feedback from a building automation system to predict the building energy loads for the plurality of time steps in the optimization period, the feedback from the building automation system comprising input from one or more sensors configured to monitor conditions within a controlled building;
a high level optimization module configured to generate an objective function that expresses a total monetary cost of operating the central plant over the optimization period as a function of the utility rate data and an amount of the one or more resources consumed by multiple groups of the central plant equipment at each of the plurality of time steps;
wherein the high level optimization module is configured to optimize the objective function over the optimization period subject to a set of constraints to determine an optimal amount of the predicted building energy loads assigned to each of the groups of the central plant equipment at each of the plurality of time steps, wherein the set of constraints ensure that the optimal distribution satisfies the predicted building energy loads at each of the plurality of time steps; and
a load change penalty module configured to modify the objective function to account for a load change penalty resulting from a change in the amount of the building energy loads assigned to one or more of the groups of the central plant equipment, wherein the load change penalty module is configured to calculate and apply the load change penalty at each time step k of the optimization period for each group of the central plant equipment as a function of and proportional to the change in the amount of the building energy loads assigned to the group of the central plant equipment at time step k relative to the amount of the building energy loads assigned to the same group of the central plant equipment at a previous time step k−1 consecutive with time step k;

wherein the central plant controller is configured to control the central plant equipment such that the central plant equipment operate to achieve the optimal distribution of the building energy loads at each of the plurality of time steps.

2. The optimization and control system of claim 1 , wherein the high level optimization module uses linear programming to generate and optimize the objective function.

3. The optimization and control system of claim 1 , wherein modifying the objective function to account for the load change penalty comprises:
adding one or more load change variables to the objective function, each of the load change variables representing a change in an energy load assigned to a corresponding group of the central plant equipment; and
weighting each of the load change variables with a cost representing a monetary penalty associated with a per unit change in an energy load assigned to the corresponding group of the central plant equipment.

4. The optimization and control system of claim 1 , wherein modifying the objective function to account for the load change penalty comprises:
adding one or more constraints to the set of constraints that require a change in an energy load assigned to a group of the central plant equipment to be less than or equal to a threshold value.

5. The optimization and control system of claim 4 , wherein the threshold value is a percentage of a maximum capacity of the group of the central plant equipment.

6. The optimization and control system of claim 1 , wherein:
the objective function comprises a cost vector including cost variables that represent a monetary cost associated with each of the one or more resources consumed by the central plant equipment to serve the building energy loads at each of the plurality of time steps; and
modifying the objective function to account for the load change penalty comprises adding a load change cost to the cost vector.

7. The optimization and control system of claim 6 , wherein modifying the objective function to account for the load change penalty comprises adding a load change cost to the cost vector for each of the groups of the central plant equipment.

8. The optimization and control system of claim 1 , wherein:
the objective function comprises a decision matrix including load variables that represent an energy load for each of the multiple groups of the central plant equipment at each of the plurality of time steps;
modifying the objective function to account for the load change penalty comprises adding a load change variable to the decision matrix; and
optimizing the objective function comprises determining optimal values for the load variables in the decision matrix.

9. The optimization and control system of claim 8 , wherein modifying the objective function to account for the load change penalty comprises adding a load change variable to the decision matrix for each of the groups of the central plant equipment.

10. The optimization and control system of claim 8 , wherein modifying the objective function to account for the load change penalty comprises adding one or more constraints on the load change variable to the set of constraints for each of the plurality of time steps in the optimization period;
wherein the one or more constraints on the load change variable for each time step require the load change variable to be greater than or equal to a change in the energy load assigned to a corresponding group of the central plant equipment relative to a previous time step.

11. A method for incorporating a load change penalty in an optimization process for a central plant, the method comprising:
using feedback from a building automation system to predict building energy loads for a plurality of time steps in an optimization period, the feedback from the building automation system comprising input from one or more sensors configured to monitor conditions within a controlled building;
receiving, at a central plant controller, utility rate data indicating a price of one or more resources consumed by central plant equipment of the central plant to serve the building energy loads at each of the plurality of time steps;
generating, by a high level optimization module of the central plant controller, an objective function that expresses a total monetary cost of operating the central plant over the optimization period as a function of the utility rate data and an amount of the one or more resources consumed by multiple groups of the central plant equipment at each of the plurality of time steps;
optimizing, by the high level optimization module, the objective function over the optimization period subject to a set of constraints to determine an optimal amount of the predicted building energy loads assigned to each of the groups of the central plant equipment at each of the plurality of time steps, wherein the set of constraints ensure that the optimal amount satisfies the predicted building energy loads at each of the plurality of time steps;
modifying, by a load change penalty module of the central plant controller, the objective function to account for a load change penalty resulting from a change in the amount of the building energy loads assigned to one or more of the groups of the central plant equipment, wherein the load cha

Assignees

• Johnson Controls Tech Co

Inventors

• Wenzel Michael J
• Turney Robert D

Classifications

• G05B2219/2639

  Energy management, use maximum of cheap power, keep peak load low · CPC title

• G05B2219/2642

  Domotique, domestic, home control, automation, smart house · CPC title

• G05B2219/32021

  Energy management, balance and limit power to tools · CPC title

• G05B2219/31414

  Calculate amount of production energy, waste and toxic release · CPC title

• G06Q10/04

  Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem" (market predictions or forecasting for commercial activities G06Q30/0202) · CPC title