HYBRID PULSE WIDTH MODULATION METHOD FOR VARIABLE SPEED DRIVE

摘要

A system or method controlling a variable speed drive based on PWM techniques, wherein a first PWM method is used when the input current is less than a predetermined threshold value, for higher efficiency and lower total harmonic distortion (THD); and a second PWM method comprising a discontinuous modulation signal is used when the input current is greater than the predetermined threshold value for higher efficiency. By doing so, the maximum efficiency of VSD within the whole operation range can be achieved.

主权项

1. A method for controlling a variable speed drive (VSD) using a hybrid pulse width modulation (PWM) method comprising:
providing a compressor, a condenser, and an evaporator connected in a closed refrigerant loop; a motor connected to the compressor to power the compressor; and the variable speed drive connected to the motor, the variable speed drive being configured to receive an input AC power at a fixed input AC voltage and a fixed input frequency and provide an output power at a variable voltage and variable frequency to the motor; determining an optimal threshold input current value for the variable speed drive; determining an actual input current value of the variable speed drive; comparing the actual current input value of the VSD with an optimal threshold current input value of the VSD; applying a first PWM method in response to the input current being less than the predetermined threshold input current value; and applying a second PWM mode in response to the input current being greater than the predetermined threshold value.