METHOD FOR CONSTANT AIR VOLUME CONTROL BY DIRECT POWER CONTROL OF PM MOTOR AND HVAC SYSTEM APPLYING SAME

摘要

The present invention discloses a method of constant airflow control of motor direct power control and a HVAC system using the same. The method comprises the following steps of: step A), starting a motor controller to receive a target airflow IN-CFM; step B), acquiring a corresponding function P=f(n) according to the target airflow IN-CFM; step C), entering a direct power controlled constant airflow control mode: controlling a motor to reach a steady working point (pt, nt) along a control track of the function P=f(n); step D), calculating the real-time input power Pi of the motor according to operating parameters of the motor, and calculating ”P=| Pt-Pi |; step E), keeping the current working point if ”P is less than a set value Pset; step F), calculating whether the operating time of a speed loop is reached if ”P is greater than or equal to the set value Pset, and keeping the current working point if the operating time of the speed loop is not reached; and step G), entering a speed control circuit to adjust the speed if the time is already reached, so as to realize a new working point (Pi, ni) on the track, i.e., letting pt=Pi and nt=ni, and returning to step C. The present invention is particularly suitable for the airflow control at a steady state, and has simple algorithm, low requirements for CPU operation, low cost and high control accuracy.