Adjustable PWM method to increase low speed starting torque and inverter voltage measurement accuracy
AssigneeRockwell Automation Technologies, Inc.
InventorsLixiang Wei, Jeffrey D. McGuire, Timothy M. Rowan
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Abstract
Methods, control apparatus and computer readable mediums are presented for controlling a switching inverter in which a controller selectively suspends PWM carrier signals to provide inverter switching control signals using zero vectors in response to a maximal pulse width value for a present PWM half cycle being greater than a threshold value, and accumulates a present output control value for individual output phases for use in a subsequent PWM half cycle for selective effective reduction in switching frequency for low-speed operation while maintaining high frequency control loop sampling.
Claims20
A method for controlling a switching inverter, the method comprising:
- determining a duty ratio for each output phase of the switching inverter for a present pulse width modulation (PWM) half cycle;
- determining, for each output phase, a present output control value for the present PWM half cycle as a sum of a previous output control value corresponding to a previous PWM half cycle and the duty ratio corresponding to the present PWM half cycle;
- determining a pulse width value for the present PWM half cycle according to a maximal one of the present output control values or a maximal present output control value difference between two phases for the present PWM half cycle;
- selectively generating switching control signals to operate the switching inverter for the present PWM half cycle according to the present output control values in response to the pulse width value for the present PWM half cycle being greater than a threshold value;
- selectively resetting the present output control values to zero in response to the pulse width value for the present PWM half cycle being greater than the threshold value;
- and
- selectively generating the switching control signals to operate the switching inverter for the present PWM half cycle according to a zero vector in response to the pulse width value for the present PWM half cycle being less than or equal to the threshold value.
A non-transitory computer readable medium with computer executable instructions for controlling a switching inverter, the computer readable medium comprising computer executable instructions for:
- determining a duty ratio for each output phase of the switching inverter for a present pulse width modulation (PWM) half cycle;
- determining, for each output phase, a present output control value for the present PWM half cycle as a sum of a previous output control value corresponding to a previous PWM half cycle and the duty ratio corresponding to the present PWM half cycle;
- determining a pulse width value for the present PWM half cycle according to a maximal one of the present output control values or a maximal present output control value difference between two phases for the present PWM half cycle;
- selectively generating switching control signals to operate the switching inverter for the present PWM half cycle according to the present output control values in response to the pulse width value for the present PWM half cycle being greater than a threshold value;
- selectively resetting the present output control values to zero in response to the pulse width value for the present PWM half cycle being greater than the threshold value;
- and
- selectively generating the switching control signals to operate the switching inverter for the present PWM half cycle according to a zero vector in response to the pulse width value for the present PWM half cycle being less than or equal to the threshold value.
An apparatus for controlling a multiphase inverter, comprising:
- an electronic memory;
- and
- at least one processor programmed to:
- determine a duty ratio for each output phase of the multiphase inverter for a pulse width modulation (PWM) half cycle;
- determine, for each output phase, a present output control value for the present PWM half cycle as a sum of a previous output control value corresponding to a previous PWM half cycle and the duty ratio corresponding to the present PWM half cycle;
- determine a pulse width value for the present PWM half cycle according to a maximal one of the present output control values or a maximal present output control value difference between two phases for the present PWM half cycle;
- selectively generate switching control signals to operate the switching inverter for the present PWM half cycle according to the present output control values in response to the pulse width value for the present PWM half cycle being greater than a threshold value;
- selectively reset the present output control values to zero in response to the pulse width value for the present PWM half cycle being greater than the threshold value;
- and
- selectively generate the switching control signals to operate the switching inverter for the present PWM half cycle according to a zero vector in response to the pulse width value for the present PWM half cycle being less than or equal to the threshold value.
Dependencies are inferred from the claim text.