AC/DC converter and method of modulation thereof

1. A method for modulating a discontinuous conduction mode (DCM) Boost Rectifier having a switchable booster section, the method comprising:

defining a booster section ON time modulation signal having a modulation characteristic according to the following equation:

T ON (φ)= f 1(φ)+ f 2(φ)+ f 3(φ),

where,

φ defines a phase angle for an input phase voltage of the DCM Boost Rectifier;

T ON (φ) defines a modulation characteristic for an ON time of the booster section, and is a continuous function;

f1(φ) defines a first function from 0≦φ≦π/3;

f2(φ) defines a second function from π/3≦φ≦2π/3;

f3(φ) defines a third function from 2π/3≦φ≦π; and modulating the switchable booster section using the modulation signal.

2. The method of claim 1 , wherein:

the f1(φ) function comprises a linear characteristic;

the f2(φ) function comprises a non-linear characteristic; and

the f3(φ) function comprises a linear characteristic.

3. The method of claim 1 , wherein:

f1(φ) and f3(φ) are each triangular functions having a positive peak at φ equals π/6 and 5π/6, respectively.

4. The method of claim 1 , wherein:

f1(φ) is a linear function having a negative slope and a peak at φ=0; and

f3(φ) is a linear function having a positive slope and a peak at φ=π.

5. The method of claim 1 , wherein:

f2(φ) is a quadratic function having a minimum at φ=π/2.

6. The method of claim 1 , wherein:

T ON (φ) is defined by:

T ON (φ)= K*[Vdc (φ)−Vmax(φ)] 0.5 ,

where,

K defines a factor proportional to the active power to be drawn by the DCM Boost Rectifier;

Vdc defines the output voltage of the DCM Boost Rectifier;

Vmax defines the voltage on the input phase of the DCM Boost Rectifier having the maximum amplitude.

7. The method of claim 6 , wherein:

the modulation characteristic shape of T ON , as a function of the angle φ, is composed of two triangular portions each having a maximum amplitude defined by coefficient G p , and by a third harmonic portion having a minimum value defined by coefficient K T , the K T minimum being intermediate the two G p maximums.

8. The method of claim 7 , wherein:

the two triangular portions are defined at phase voltage angles 0≦φ≦π/3 and 2π/3≦φ≦π, respectively; and

the third harmonic portion is defined at phase voltage angles π/3≦φ≦2π/3.

9. The method of claim 6 , wherein:

the modulation characteristic shape of T ON , as a function of the angle φ, is composed of two straight line portions each having a maximum amplitude defined by coefficient G p , and by a third harmonic portion having a minimum value defined by coefficient K T , the K T minimum being intermediate the two G p maximums.

10. The method of claim 9 , wherein:

the two straight line portions are defined at phase voltage angles 0≦φ≦π/3 and 2π/3≦φ≦π, respectively; and

the third harmonic portion is defined at phase voltage angles π/3≦φ≦2π/3.

11. The method of claim 1 , further comprising:

providing the modulation signal to a two-switch three level DCM Boost Rectifier.

12. The method of claim 1 , further comprising:

providing the modulation signal to a six-switch three level DCM Boost Rectifier.

13. The method of claim 8 , further comprising:

providing the modulation signal to a two-switch three level DCM Boost Rectifier.

14. The method of claim 10 , further comprising:

providing the modulation signal to a six-switch three level DCM Boost Rectifier.

15. The method of claim 1 , further comprising:

performing an iterative analysis on the modulation signal for a specified DCM Boost Rectifier in order to satisfy a defined set of cost functions, thereby defining a quasi-optimal modulation signal; and

wherein the modulating comprises modulating the switchable booster section using the quasi-optimal modulation signal.

16. An apparatus for modulating a discontinuous conduction mode (DCM) Boost Rectifier having a switchable booster section, the apparatus comprising a processor operable in response to executable instructions for:

modulating the switchable booster section using a defined ON time modulation signal having a modulation characteristic according to the following equation:

T ON (φ)= f 1(φ)+ f 2(φ)+ f 3(φ),

where,

φ defines a phase angle for an input phase voltage of the DCM Boost Rectifier;

T ON (φ) defines a modulation characteristic for an ON time of the booster section, and is a continuous function;

f1(φ) defines a first function comprising a linear characteristic from 0≦φ≦π/3;

f2(φ) defines a second function comprising a non-linear characteristic from π/3≦φ≦2π/3; and

f3(φ) defines a third function comprising a linear characteristic from 2π/3≦φ≦π.

17. The apparatus of claim 16 , wherein the switchable booster section comprises a two-switch booster section, and wherein the processor is further operable in response to executable instructions for:

modulating the two-switch booster section wherein:

f1(φ) and f3(φ) are each triangular functions having a positive peak at φ equals π/6 and 5π/6, respectively; and

f2(φ) is a quadratic function having a minimum at φ=π/2.

18. The apparatus of claim 16 , wherein the switchable booster section comprises a six-switch booster section, and wherein the processor is further operable in response to executable instructions for:

modulating the six-switch booster section wherein:

f1(φ) is a linear function having a negative slope and a peak at φ=0;

f2(φ) is a quadratic function having a minimum at φ=π/2; and

f3(φ) is a linear function having a positive slope and a peak at φ=π.

19. The apparatus of claim 16 , wherein the processor is further operable in response to executable instructions for:

prior to the modulating, defining the modulation signal for a specified DCM Boost Rectifier that satisfies a defined set of cost functions, thereby defining a quasi-optimal modulation signal.

20. The apparatus of claim 19 , wherein the processor is further operable in response to executable instructions for:

defining the modulation signal by reference to a look up table, defining the modulation signal by performing a real-time iterative analysis relating to an operational parameter of the DCM Boost Rectifier, or both.