Cascade control systems and dehumidifier systems for controlling a humidity level

Abstract

A cascade control system of a dehumidifier for controlling a humidity level including: a heater for adjusting the humidity level of the outlet process air by heating inlet reactivation air, a primary control module for controlling the humidity level by controlling the dehumidifier, and a secondary control module for controlling the temperature of inlet reactivation air to match a desired temperature setpoint by controlling the heater. The primary control module is configured to regulate the humidity level to match a desired humidity setpoint while providing the desired temperature setpoint for the secondary control module as output. The primary controller is a Model Predictive Control, MPC, module configured to predict future humidity levels and to calculate the desired temperature setpoint for the secondary control module based on the predicted humidity levels.

1 . A cascade control system of a dehumidifier for controlling a humidity level, the dehumidifier comprising a desiccant rotor, the desiccant rotor comprising a desiccant material, the dehumidifier being arranged to guide a process air stream and a reactivation air stream across separate axially extending channels through the desiccant material, each air stream having respective inlet air when entering the desiccant material and outlet air when exiting the desiccant material, the inlet reactivation air being arranged to remove moisture from the desiccant material when heated, the cascade control system comprising:
 a heater for adjusting the humidity level of the outlet process air by heating the inlet reactivation air,   a primary control module for controlling the humidity level by controlling at least one operational parameter of the dehumidifier, and   a secondary control module for controlling the temperature of the inlet reactivation air to match a desired temperature setpoint by controlling at least one operational parameter of the heater,   wherein the primary control module is configured to regulate the humidity level to match a desired humidity setpoint while providing the desired temperature setpoint for the secondary control module as output, and   wherein that the primary controller is a Model Predictive Control (MPC) module configured to predict future humidity levels based on historical data on the humidity level and historical data on the desired temperature setpoints provided to the secondary control module, and to calculate the desired temperature setpoint for the secondary control module based on the predicted humidity levels.   
     
     
         2 . The cascade control system according to  claim 1 , wherein the MPC module is configured to utilize a machine learning (ML) algorithm in the prediction of the future humidity levels. 
     
     
         3 . The cascade control system according to  claim 1 , wherein the secondary control module comprises at least one PID controller. 
     
     
         4 . The cascade control system according to  claim 1 , wherein the MPC module is further configured to predict the future humidity levels and/or to calculate the desired temperature setpoint for the secondary control module based on sensor data relating to parameters influencing the humidity level being controlled. 
     
     
         5 . The cascade control system according to  claim 1 , wherein the MPC module comprises
 a predictor module, and   an optimizer module,   wherein the predictor module is configured to predict the future humidity levels, the predicting of the future humidity levels further comprises
 generating a plurality of sequential future humidity levels, and 
 generating a plurality of future desired temperature setpoints, 
   wherein the optimizer module is configured to calculate the desired temperature setpoint for the secondary control module, the calculating of the desired temperature setpoint being based on at least one of a humidity level control performance metric using the plurality of sequential future humidity levels, a desired temperature setpoint stability metric using the plurality of future desired temperature setpoints and an energy efficiency performance metric using the plurality of future desired temperature setpoints.   
     
     
         6 . The cascade control system according to  claim 1 , wherein the predicting of future humidity levels is performed using a linear model. 
     
     
         7 . The cascade control system according to  claim 6 , the calculating of the desired temperature setpoint is determined from a closed form solution. 
     
     
         8 . The cascade control system according to  claim 1 , further comprising a primary PID control module configured to control the humidity level by controlling the at least one operational parameter of the dehumidifier and provide the desired temperature setpoint for the secondary control module when a predetermined criterion is met. 
     
     
         9 . The cascade control system according to  claim 1 , wherein the cascade control system is further configured to adjusting the desired temperature setpoint for the secondary control module based on the temperature and/or the humidity level of the outlet reactivation air. 
     
     
         10 . The cascade control system according to  claim 1 , further comprising a tertiary control module for controlling the temperature of the outlet reactivation air by adjusting the desired temperature setpoint for the secondary control module based on a difference between the temperature of the outlet reactivation air and a predetermined threshold temperature. 
     
     
         11 . The cascade control system according to  claim 1 , further comprising a quaternary control module, the quaternary control module being configured to
 receive a desired room humidity setpoint relating to a humidity level of a room to which the outlet process air is fed,   receive a current humidity level of the room, and   generate the desired humidity setpoint for the primary control module.   
     
     
         12 . A dehumidifier system for controlling a humidity level, the dehumidifier system comprising
 a dehumidifier, and   the cascade control system according to  claim 1 .