Control device for rotating electric machine and method of controlling rotating electric machine
An ECU executes a program including a step of detecting the rotation speed of a motor, a step of determining the diffusion width of carrier frequency, a step of determining the carrier frequency based on the determined diffusion width, a step of generating a carrier signal based on the determined carrier frequency, and a step of executing pulse width modulation based on an AC voltage command and the carrier signal.
1. A control device for a rotating electric machine having a three-phase coil, comprising:
a detection unit for detecting a rotation speed of said rotating electric machine;
a determination unit for determining a diffusion width of a carrier frequency based on the rotation speed of said rotating electric machine detected by said detection unit such that a plurality of sideband wave components occurring centered on the carrier frequency while said rotating electric machine is driven are not superimposed on one another, said determination unit determining said diffusion width such that, when the rotation speed of said rotating electric machine is a first rotation speed, said diffusion width is larger than said diffusion width when the rotation speed is a second rotation speed which is lower than said first rotation speed;
a carrier generation unit for changing the carrier frequency within a range of said diffusion width determined by said determination unit to generate a carrier signal; and
a pulse width modulation unit for executing pulse width modulation based on a command voltage and said carrier signal to generate a pulse signal for driving said rotating electric machine.
2. The control device for a rotating electric machine according to claim 1 , wherein
said determination unit determines said diffusion width such that said diffusion width changes in proportion to the rotation speed of said rotating electric machine between said first rotation speed and said second rotation speed.
3. The control device for a rotating electric machine according to claim 1 , wherein
said determination unit determines said diffusion width such that said diffusion width changes stepwise relative to the rotation speed of said rotating electric machine between said first rotation speed and said second rotation speed.
4. The control device for a rotating electric machine according to claim 1 , wherein
said carrier generation unit changes the carrier frequency at random within the range of said diffusion width determined by said determination unit to generate said carrier signal.
5. The control device for a rotating electric machine according to claim 1 , wherein
said carrier generation unit changes the carrier frequency along a sine wave within the range of said diffusion width determined by said determination unit to generate said carrier signal.
6. The control device for a rotating electric machine according to claim 1 , wherein
said carrier generation unit changes the carrier frequency so as to change stepwise within the range of said diffusion width determined by said determination unit to generate said carrier signal.
7. A method of controlling a rotating electric machine having a three-phase coil, comprising the steps of:
detecting a rotation speed of said rotating electric machine;
determining a diffusion width of a carrier frequency based on the rotation speed of said rotating electric machine such that a plurality of sideband wave components occurring centered on the carrier frequency while said rotating electric machine is driven are not superimposed on one another, the determining of the diffusion width being such that, when the rotation speed of said rotating electric machine is a first rotation speed, said diffusion width is larger than said diffusion width when the rotation speed is a second rotation speed which is lower than said first rotation speed;
changing the carrier frequency within a range of said diffusion width to generate a carrier signal; and
executing pulse width modulation based on a command voltage and said carrier signal to generate a pulse signal for driving said rotating electric machine.