Delay compensation for stable current regulation when using variable-delay random PWM switching
A control system for an electric machine having a rotor position sensor that generates a rotor position signal, a velocity module that generates an electric angular velocity value based on the 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 the switching period, and the delay of a previous cycle and that outputs a delay time. The phase angle compensation module further multiplies the delay time and the electric angular velocity value and generates a compensating angle.
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.