Delay compensation for stable current regulation when using variable-delay random PWM switching

1. A control system for an electric machine, comprising:

a rotor position sensor that generates a rotor position signal;

a velocity module that generates an electric angular velocity value based on said rotor position signal;

a random pulse width modulation module that generates a switching period and a delay for a current cycle; and

a phase angle compensation module that sums a sample rate, one half of said switching period, and said delay of a previous cycle and that outputs a delay time and that multiplies said delay time and said electric angular velocity value to generate a compensating angle.

2. The control system according to claim 1 further comprising:

a second summer that sums said compensating angle and said rotor position value to generate a transformation angle.

3. The control system according to claim 2 further comprising:

a synchronous-to-stationary transformation module that receives said transformation angle and a synchronous reference frame voltage command and that outputs a stationary frame voltage command.

4. The control system according to claim 3 further comprising:

a subtractor that subtracts a measured synchronous reference frame current from a current command and that outputs an error signal; and

a current regulator that receives said error signal and that generates said synchronous reference frame voltage command.

5. The control system according to claim 1 wherein said rotor position sensor is a sensorless sensor that senses inductance in windings of said electric machine and generates said rotor position signal based thereon.

6. The control system according to claim 1 wherein said rotor position sensor includes a transducer that measures a position of said rotor.

7. A control system for an electric machine, comprising:

a rotor position sensor that generates a rotor position signal;

a velocity module that generates an electric angular velocity value based on said rotor position signal;

a random pulse width modulation module that generates a switching period and a delay for a current cycle;

a phase angle compensation module that sums a sample rate, one half of said switching period, and said delay of a previous cycle and that outputs a delay time and that multiplies said delay time and said electric angular velocity value to generate a compensating angle; and

a pulse width modulation inverter module that receives a synchronous reference frame voltage command, said switching period, and said delay and that generates a voltage output to said electric machine.

8. The control system according to claim 7 further comprising a second summer that sums said compensating angle and said rotor position value to generate a transformation angle.

9. The control system according to claim 8 further comprising a synchronous-to-stationary transformation module that receives said transformation angle and a synchronous reference frame voltage command and that outputs a stationary frame voltage command.

10. The control system according to claim 9 , further comprising:

a subtractor that subtracts a measured synchronous reference frame current from a current command and that outputs an error signal; and

a current regulator that receives said error signal and that generates said synchronous reference frame voltage command.

11. The control system according to claim 7 wherein said rotor position sensor is a sensorless sensor that senses inductance in windings of said electric machine and that generates said rotor position signal based thereon.

12. The control system according to claim 7 wherein said rotor position sensor includes a transducer that measures a position of said rotor.