Hvac system using model predictive control with distributed low-level airside optimization and airside power consumption model

Abstract

A building HVAC system includes an airside system having a plurality of airside subsystems, a waterside system, a high-level model predictive controller (MPC), and a plurality of low-level airside MPCs. Each airside subsystem includes airside HVAC equipment configured to provide heating or cooling to the airside subsystem. The waterside system includes waterside HVAC equipment configured to produce thermal energy used by the airside system to provide the heating or cooling. The high-level MPC is configured to perform a high-level optimization to generate an optimal airside subsystem load profile for each of the plurality of airside subsystems. The optimal airside subsystem load profiles optimize a total cost of energy consumed by the airside system and the waterside system Each of the low-level airside MPCs is configured to operate the airside HVAC equipment of an airside subsystem according to the load profile for the airside subsystem.

1 . A heating, ventilation, or air conditioning (HVAC) system for a building, the HVAC system comprising:
 an airside system having a plurality of airside subsystems, each airside subsystem comprising airside HVAC equipment configured to provide heating or cooling to the airside subsystem;   a waterside system comprising waterside HVAC equipment configured to produce thermal energy used by the airside system to provide the heating or cooling;   a high-level model predictive controller configured to perform a high-level optimization to generate an optimal airside subsystem load profile for each of the plurality of airside subsystems, wherein the optimal airside subsystem load profiles optimize a total energy cost of both airside power consumption by the airside system and waterside power consumption by the waterside system at each of a plurality of time steps in an optimization period; and   a plurality of low-level airside model predictive controllers, each corresponding to one of the airside subsystems and configured to use the optimal airside subsystem load profile for the corresponding airside subsystem to operate the airside HVAC equipment of the corresponding airside subsystem.   
     
     
         2 . The HVAC system of  claim 1 , wherein the airside subsystems represent separate buildings thermally decoupled from one another such that no direct heat exchange occurs between the airside subsystems. 
     
     
         3 . The HVAC system of  claim 1 , wherein:
 each airside subsystem load profile indicates a thermal energy allocation to one of the plurality of airside subsystems at each of the plurality of time steps; and   the high-level model predictive controller is configured to use an airside power consumption model to define the airside power consumption of each airside subsystem as a function of the thermal energy allocation to the airside subsystem.   
     
     
         4 . The HVAC system of  claim 1 , wherein the high-level model predictive controller is configured to generate an airside subsystem temperature model for each of the plurality of airside subsystems, each airside subsystem temperature model defining a relationship between one of the airside subsystem load profiles and a temperature of the corresponding airside subsystem. 
     
     
         5 . The HVAC system of  claim 1 , wherein the high-level model predictive controller is configured to generate an optimal waterside demand profile for the waterside system;
 the system further comprising a low-level waterside model predictive controller configured to perform a low-level optimization to generate optimal waterside setpoints for the waterside system subject to a demand constraint based on the optimal waterside demand profile;   wherein the low-level waterside model predictive controller is configured to use the optimal waterside setpoints to operate waterside HVAC equipment in the waterside system.   
     
     
         6 . The HVAC system of  claim 1 , wherein the high-level model predictive controller is configured to:
 perform the high-level optimization by optimizing a high-level cost function which defines the total energy cost as a function of a waterside demand profile indicating a thermal energy production of the waterside system at each of the plurality of time steps in the optimization period; and   use a waterside demand model to define the waterside demand profile as a function of the plurality of airside subsystem load profiles.   
     
     
         7 . The HVAC system of  claim 1 , wherein each of the low-level airside model predictive controllers is configured to:
 perform a low-level optimization to generate optimal airside temperature setpoints for the corresponding airside subsystem using the optimal airside subsystem load profile for the corresponding airside subsystem; and   use the optimal airside temperature setpoints for the corresponding airside subsystem to operate the airside HVAC equipment in the corresponding airside subsystem.   
     
     
         8 . The HVAC system of  claim 7 , wherein:
 each airside subsystem comprises a plurality of building zones; and   the optimal airside temperature setpoints for each airside subsystem comprise optimal airside temperature setpoints for each of the plurality of building zones in the airside subsystem.   
     
     
         9 . The HVAC system of  claim 7 , wherein each of the low-level airside model predictive controllers is configured to generate a zone load profile for each of the plurality of building zones in the corresponding airside subsystem, each zone load profile indicating a thermal energy allocation to one of the building zones at each of the plurality of time steps in the optimization period. 
     
     
         10 . The HVAC system of  claim 1 , wherein each of the optimal airside subsystem load profiles comprises at least one of:
 optimal thermal energy load values for the corresponding airside subsystem at each of the plurality of time steps; and   optimal temperature values for the corresponding airside subsystem at each of the plurality of time steps.   
     
     
         11 . A method for optimizing energy cost in a building HVAC system including a waterside system and an airside system having a plurality of airside subsystems, the method comprising:
 generating a high-level cost function defining the energy cost as a function of both a waterside power consumption of the waterside system and an airside power consumption of each airside subsystem at each of a plurality of time steps in an optimization period;   performing a high-level optimization at a high-level model predictive controller to generate an optimal airside subsystem load profile for each of the plurality of airside subsystems, wherein the optimal airside subsystem load profiles optimize the energy cost;   providing the optimal airside subsystem load profiles from the high-level model predictive controller to a plurality of low-level airside model predictive controllers, each of the low-level airside model predictive controllers corresponding to one of the plurality of airside subsystems;   using the optimal airside subsystem load profiles at each of the low-level airside model predictive controllers to operate airside HVAC equipment in the corresponding airside subsystem.   
     
     
         12 . The method of  claim 11 , wherein the airside subsystems represent separate buildings thermally decoupled from one another such that no direct heat exchange occurs between the airside subsystems. 
     
     
         13 . The method of  claim 11 , wherein each airside subsystem load profile indicates a thermal energy allocation to one of the plurality of airside subsystems at each of the plurality of time steps;
 the method further comprising using an airside power consumption model to define the airside power consumption of each airside subsystem as a function of the thermal energy allocation to the airside subsystem.   
     
     
         14 . The method of  claim 11 , further comprising generating an airside subsystem temperature model for each of the plurality of airside subsystems, each airside subsystem temperature model defining a relationship between one of the airside subsystem load profiles and a temperature of the corresponding airside subsystem. 
     
     
         15 . The method of  claim 11 , wherein performing the high-level optimization comprises generating an optimal waterside demand profile for the waterside system, the method further comprising:
 providing the optimal waterside demand profile to a low-level waterside model predictive controller;   performing a low-level optimization at the low-level waterside model predictive controller to generate optimal waterside setpoints for the waterside system subject to a demand constraint based on the optimal waterside demand profile; and   using the optimal waterside setpoints to operate waterside HVAC equipment in the waterside system.   
     
     
         16 . The method of  claim 11 , wherein the high-level cost function defines the energy cost as a function of a waterside demand profile indicating a thermal energy production of the waterside system at each of the plurality of time steps in the optimization period;
 the method further comprising using a waterside demand model to define the waterside demand profile as a function of the plurality of airside subsystem load profiles.   
     
     
         17 . The method of  claim 11 , further comprising:
 performing a low-level optimization at each of the low-level airside model predictive controllers to generate optimal airside temperature setpoints for the corresponding airside subsystem using the optimal airside subsystem load profile for the corresponding airside subsystem; and   using the optimal airside temperature setpoints for the corresponding airside subsystem to operate the airside HVAC equipment in the corresponding airside subsystem.   
     
     
         18 . The method of  claim 17 , wherein:
 each airside subsystem comprises a plurality of building zones; and   performing the low-level optimization comprises generating optimal airside temperature setpoints for each of the plurality of building zones.   
     
     
         19 . The method of  claim 18 , wherein performing the low-level optimization comprises generating a zone load profile for each of the plurality of building zones, each zone load profile indicating a thermal energy allocation to one of the building zones at each of the plurality of time steps in the optimization period. 
     
     
         20 . A method for optimizing energy cost in a building HVAC system including a waterside system and an airside system having a plurality of airside subsystems, the method comprising:
 generating a high-level cost function defining the energy cost as a function of both a waterside power consumption of the waterside system and an airside power consumption of each airside subsystem at each of a plurality of time steps in an optimization period;   performing a high-level optimization at a high-level model predictive controller to generate an optimal airside subsystem temperature profile for each of the plurality of airside subsystems, wherein the optimal airside subsystem temperature profiles optimize the energy cost defined by the cost function;   providing the optimal airside subsystem temperature profiles from the high-level model predictive controller to a plurality of low-level airside model predictive controllers, each of the low-level airside model predictive controllers corresponding to one of the plurality of airside subsystems; and   using the optimal airside subsystem temperature profiles at each of the low-level airside model predictive controllers to operate airside HVAC equipment in the corresponding airside subsystems.