Cascaded indoor air quality and outdoor air flow economizer system

A control system for an economizer, the control system comprising:

• an economizer configured to facilitate an outdoor air flow (OAF) of outdoor air into a conditioned space;
• a flow rate sensor configured to measure an actual OAF of the outdoor air entering the conditioned space;
• an air quality sensor configured to measure an actual indoor air quality (IAQ) of the conditioned space;
• and
• a controller configured to:
• receive the actual IAQ of the conditioned space and determine an IAQ setpoint error based on the actual IAQ and an IAQ setpoint;
• determine an adjusted OAF setpoint based on the IAQ setpoint error, an initial or previous OAF setpoint, and an OAF setpoint upper limit in response to a comparison between the initial or previous IAQ setpoint error and an IAQ setpoint error threshold;
• perform proportional variable deadband control to adjust a deadband of the economizer based on the adjusted OAF setpoint and the actual OAF and generate control signals to cause the economizer to drive the OAF toward the adjusted OAF setpoint;
• and
• adjust an operation of at least one of an actuator and a damper of the economizer to cause outdoor air to enter the conditioned space at the adjusted OAF setpoint.

A method for controlling an economizer, the method comprising:

• receiving, from a first sensor, an actual indoor air quality (IAQ) of a conditioned space;
• determining an IAQ setpoint error based on the actual IAQ and an IAQ setpoint;
• determining an adjusted outdoor air flow (OAF) setpoint based on the IAQ setpoint error, an initial or previous OAF setpoint, and an OAF setpoint upper limit in response to the IAQ setpoint error exceeding an IAQ setpoint error threshold;
• receiving, from a second sensor, an actual outdoor air flow (OAF) of outdoor air entering the conditioned space;
• adjusting a deadband of the economizer based on the adjusted OAF setpoint and the actual OAF using a proportional variable deadband control technique and generating control signals for the economizer to achieve the adjusted OAF setpoint based on the actual OAF and the adjusted deadband;
• controlling the economizer to drive the actual OAF toward the adjusted OAF setpoint;
• and
• repeating the steps of receiving the actual OAF from the second sensor, adjusting the deadband and generating control signals, and controlling the economizer until the actual OAF meets the OAF setpoint.