HYBRID PULSE WIDTH MODULATION METHOD FOR VARIABLE SPEED DRIVE
First Claim
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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.
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Abstract
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.
21 Citations
20 Claims
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1. A method for controlling a variable speed drive (VSD) using a hybrid pulse width modulation (PWM) method comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for controlling a variable speed drive (VSD) comprising:
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providing a variable speed drive for driving a motor of a compressor; configuring the variable speed drive to operate with an input AC voltage at a fixed AC input voltage and provide an output AC power at a variable voltage and variable frequency; determining a threshold value for an input current to the VSD; measuring an input current to the VSD; comparing the measured input current with the threshold value; applying a continuous pulse width modulation (PWM) method to the VSD in response to the input current being less than the threshold value; and applying a discontinuous PWM method in response to the input current being greater than or equal to the threshold value. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A method for controlling a variable speed drive based on PWM schemes comprising:
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applying a continuous PWM scheme when an input current is less than a predetermined threshold value, to provide higher efficiency and lower total harmonic distortion (THD); and applying a discontinuous PWM method comprising a discontinuous modulation scheme when the input current is greater than the predetermined threshold value.
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Specification