Three phase buck power converters having input current control

• US 7,139,180 B1
• Filed: 09/15/2005
• Issued: 11/21/2006
• Est. Priority Date: 09/15/2004
• Status: Expired due to Fees

• Current Assignee: Edward Herbert
• Original Assignee: Edward Herbert
• Inventors: Herbert, Edward
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US11/162,591
• Time in Patent Office: 432 Days
• Field of Search: 363/34, 363/44, 363/124, 363/125, 363/127, 363/131
• US Class Current: 363/124
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 1/4291 by using a Buck converter to switch the input current
• CPC Class Codes: H02M 7/2176 comprising a passive stage to generate a rectified sinusoidal voltage and a controlled switching element in series between such stage and the output
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A three phase buck power converter having input power control is described. The power converter uses a three input buck converter comprising switches for each phase, a catch rectifier, an inductor and an output capacitor. The duty cycle of the three switches is constrained to have a sine function relationship that may be derived from the input voltage wave form or from a reference oscillator. When so constrained, the input currents have high power factor. The output is a precise, high quality dc voltage, comparable to the output of a dc—dc buck converter, and the dynamic response is comparable. Voltage mode and current mode controls are shown, as is a precise line regulation feed forward for the voltage mode embodiment. The three phase buck power converter may be operated in reverse as a three phase boost converter, as they are reciprocal. A three phase ac—ac converter may have a three phase buck converter as its input and a three phase boost converter as its output.

Claims

1. A three phase buck converter having input current control for converting a three phase ac input to a dc output comprising:

a dc voltage output Vo and a dc common return;

a phase A input having a means for rectifying a phase A ac current Ia having a nominal value of IpSinX to a phase A rectified current |Ia| having a nominal value Ip|SinX|,

where Ip is the desired peak value of the three phase ac input current and where X is the desired instantaneous phase angle of the phase A ac current;

a phase B input having a means for rectifying a phase B ac current Ib having a nominal value of IpSin(X+120°

) to a phase B rectified current |Ib| having a nominal value Ip|Sin(X+120°

)|;

a phase C input having a means for rectifying a phase C ac current Ic having a nominal value of IpSin(X+240°

) to a phase A rectified current |Ic| having a nominal value Ip|Sin(X+240°

)|;

an inductor having an input terminal and an output terminal;

at least a first phase A switch connected between the means for rectifying the phase A current and the input terminal of the inductor;

at least a first phase B switch connected between the means for rectifying the phase B current and the input terminal of the inductor;

at least a first phase C switch connected between the means for rectifying the phase C current and the input terminal of the inductor;

at least a first catch rectifier having an input rectifier terminal connected to the dc common return and an output rectifier terminal connected to the input of the inductor for conducting the current in the inductor when there is not at least one of the at least a first phase A switch, the at least a first phase B switch and the at least a first phase C switch in an on state;

a capacitor having a first terminal connected to the output terminal of the inductor and the dc voltage output and having a second terminal connected to the dc common return;

means for controlling the switching of the at least a first phase A switch so that the phase A switch has a duty cycle Da equal to K|SinX|,

where K is a gain factor;

means for controlling the switching of the at least a first phase B switch so that the phase B switch has a duty cycle Db equal to K|Sin(X+120°

)|; and

means for controlling the switching of the at least a first phase C switch so that the phase C switch has a duty cycle Dc equal to K|Sin(X+240°

)|.

2. The three phase buck converter of claim 1 wherein the gain factor K has a nominal value of

$K=\frac{2}{}$

V o 3 ⁢

V p ⁢

where Vo is the desired voltage of the dc voltage output and Vp is the actual peak voltage of the three phase ac input.

3. The three phase buck converter of claim 1 wherein the gain factor K is modulated by a means for feedback control as a function of the value of the dc voltage output to control precisely the value of the dc voltage output.

4. The three phase buck converter of claim 1 wherein the gain factor K is modulated by a means for input voltage feed-forward control to compensate for variations in the voltage of the three phase ac input.

5. The three phase buck converter of claim 1 wherein the gain factor K is modulated as a function of 1/Vp² to compensate for variations in the voltage of the three phase ac input, and where Vp is the actual peak voltage of the three phase ac input.

6. The three phase buck converter of claim 1 further comprising a dc—

dc converter connected to the dc output voltage to provide a modified dc voltage output having dielectric isolation.

7. The three phase buck converter of claim 1 further comprising a dc—

dc converter connected to the dc output voltage to provide a modified dc voltage output having a different dc voltage value.

8. The three phase buck converter of claim 1 wherein the means for rectifying a phase A ac current Ia is a positive phase A rectifier and a negative phase A rectifier, the positive phase A rectifier rectifying the phase A input current Ia when the phase A input current Ia is positive and the negative phase A rectifier rectifying the phase A input current Ia when the phase A input current Ia is negative;

the means for rectifying a phase B ac current Ib is a positive phase B rectifier and a negative phase B rectifier, the positive phase B rectifier rectifying the phase B input current Ib when the phase B input current Ib is positive and the negative phase B rectifier rectifying the phase B input current Ib when the phase B input current Ib is negative;

the means for rectifying a phase C ac current Ic is a positive phase C rectifier and a negative phase C rectifier, the positive phase C rectifier rectifying the phase C input current Ic when the phase C input current Ic is positive and the negative phase C rectifier rectifying the phase C input current Ic when the phase C input current Ic is negative;

the at least a first phase A switch is a positive phase A switch connected between the positive phase A rectifier and the input of the inductor, the positive phase A switch operating when the phase A input current Ia is positive;

the at least a first phase B switch is a positive phase B switch connected between the positive phase B rectifier and the input of the inductor, the positive phase B switch operating when the phase B input current Ib is positive;

the at least a first phase C switch is a positive phase C switch connected between the positive phase C rectifier and the input of the inductor, the positive phase C switch operating when the phase C input current Ic is positive;

the at least a first catch rectifier is first and second catch rectifiers connected in series with the common connection between the first and second catch rectifiers connected to a neutral input of the three phase ac input;

further comprising

a negative phase A switch connected between the negative phase A rectifier and the dc common return, the negative phase A switch operating when the phase A input current Ia is negative and the negative phase A switch;

a negative phase B switch connected between the negative phase B rectifier and the dc common return, the negative phase B switch operating when the phase B input current Ib is negative and the negative phase B switch, and;

a negative phase C switch connected between the negative phase C rectifier and the dc common return, the negative phase C switch operating when the phase C input current Ic is negative and the negative phase C switch.

9. The three phase buck converter of claim 1 wherein

the at least a first phase A switch is a phase A primary switching circuit of a phase A isolation transformer and the at least a first phase A switch is connected to the input terminal of the inductor through the phase A isolation transformer and a phase A secondary rectifying circuit;

the at least a first phase B switch is a phase B primary switching circuit of a phase B isolation transformer and the at least a first phase B switch is connected to the input terminal of the inductor through the phase B isolation transformer and a phase B secondary rectifying circuit;

the at least a first phase C switch is a phase C primary switching circuit of a phase C isolation transformer and the at least a first phase C switch is connected to the input terminal of the inductor through the phase C isolation transformer and a phase C secondary rectifying circuit.

10. The three phase buck converter of claim 1 wherein the means for rectifying a phase A ac current Ia, the means for rectifying a phase B ac current Ib, the means for rectifying a phase C ac current Ic and the at least a first catch rectifier are synchronous rectifiers.

11. The three phase buck converter of claim 8 wherein the phase A switch, the negative phase A switch, the positive phase B switch, the negative phase B switch, the positive phase C switch and the negatives phase C switch are ac switches;

and

the phase A rectifier, the negative phase A rectifier, the positive phase B rectifier, the negative phase B rectifier, the positive phase C rectifier and the negatives phase C rectifier are the phase A switch, the negative phase A switch, the positive phase B switch, the negative phase B switch, the positive phase C switch and the negatives phase C switch, respectively, operate as synchronous rectifiers as well as switches.

12. A three phase buck converter having input current control for converting a three phase ac input to a dc output comprising:

a dc voltage output Vo and a dc common return;

a phase A input having a means for rectifying a phase A ac current Ia having a nominal value of IpSinX to a phase A rectified current |Ia| having a nominal value Ip|SinX|,

where Ip is the desired peak value of the three phase ac input current and where X is the desired instantaneous phase angle of the phase A ac current;

a phase B input having a means for rectifying a phase B ac current Ib having a nominal value of IpSin(X+120°

) to a phase B rectified current |Ib| having a nominal value Ip|Sin(X+120°

)|;

a phase C input having a means for rectifying a phase C ac current Ic having a nominal value of IpSin(X+240°

) to a phase A rectified current |Ic| having a nominal value Ip|Sin(X+240°

)|;

an inductor having an input terminal and an output terminal;

at least a first phase A switch connected between the means for rectifying the phase A current and the input terminal of the inductor;

at least a first phase B switch connected between the means for rectifying the phase B current and the input terminal of the inductor;

at least a first phase C switch connected between the means for rectifying the phase C current and the input terminal of the inductor;

at least a first catch rectifier having an input rectifier terminal connected to the dc common return and an output rectifier terminal connected to the input of the inductor for conducting the current in the inductor when there is not at least one of the at least a first phase A switch, the at least a first phase B switch and the at least a first phase C switch in an on state;

a capacitor having a first terminal connected to the output terminal of the inductor and the dc voltage output and having a second terminal connected to the dc common return;

and wherein at any instant of time

the one of the phase A ac current, the phase B ac current and the phase C ac current that has the highest magnitude is designated the phase 1 current and its current magnitude is designated as I1;

the one of the phase A ac current, the phase B ac current and the phase C ac current that has the second highest magnitude is designated the phase 2 current and its current magnitude is designated as I2

the one of the phase A ac current, the phase B ac current and the phase C ac current that has the lowest magnitude is designated the phase 3 current and its current magnitude is designated as I3

the one of the at least a first phase A switch, the at least a first phase B switch and the at least a first phase C switch that has the same phase as phase 1 is designated as switch 1 and its duty cycle is designated as D1

the one of the at least a first phase A switch, the at least a first phase B switch and the at least a first phase C switch that has the same phase as phase is designated as switch 3 and its duty cycle is designated as D3

the one of the at least a first phase A switch, the at least a first phase B switch and the at least a first phase C switch that has the same phase as phase is designated as switch 3 and its duty cycle is designated as D3

a means for controlling the switching of switch 1, switch 2 and switch 3 such that

the duty cycle D1 of switch 1 terminates when the current in the inductor equal a reference current as determined by a means for feedback control to precisely control the dc output current Vo;

the duty cycle D2 of switch 2 is controlled to be

$\mathrm{D2}=\mathrm{D1}<br><br>\frac{\mathrm{I2}}{\mathrm{I1}}$

and the duty cycle D3 of the switch 3 is controlled to be

$\mathrm{D3}=\mathrm{D1}<br><br>\frac{\mathrm{I3}}{\mathrm{I1}}.$

13. The three phase buck converter of claim 12 further comprising a dc—

dc converter connected to the dc output to provide a modified dc output having dielectric isolation.

14. The three phase buck converter of claim 12 further comprising a dc—

dc converter connected to the dc output to provide a modified dc output having a different dc voltage value.

15. The three phase buck converter of claim 12 wherein

the means for rectifying a phase A ac current Ia is a positive phase A rectifier and a negative phase A rectifier, the positive phase A rectifier rectifying the phase A input current Ia when the phase A input current Ia is positive and the negative phase A rectifier rectifying the phase A input current Ia when the phase A input current Ia is negative;

the means for rectifying a phase B ac current Ib is a positive phase B rectifier and a negative phase B rectifier, the positive phase B rectifier rectifying the phase B input current Ib when the phase B input current Ib is positive and the negative phase B rectifier rectifying the phase B input current Ib when the phase B input current Ib is negative;

the means for rectifying a phase C ac current Ic is a positive phase C rectifier and a negative phase C rectifier, the positive phase C rectifier rectifying the phase C input current Ic when the phase C input current Ic is positive and the negative phase C rectifier rectifying the phase C input current Ic when the phase C input current Ic is negative;

the at least a first phase A switch is a positive phase A switch connected between the positive phase A rectifier and the input of the inductor, the positive phase A switch operating when the phase A input current Ia is positive;

the at least a first phase B switch is a positive phase B switch connected between the positive phase B rectifier and the input of the inductor, the positive phase B switch operating when the phase B input current Ib is positive;

the at least a first phase C switch is a positive phase C switch connected between the positive phase C rectifier and the input of the inductor, the positive phase C switch operating when the phase C input current Ic is positive;

the at least a first catch rectifier is first and second catch rectifiers connected in series with the common connection between the first and second catch rectifiers connected to a neutral input of the three phase ac input current;

further comprising

a negative phase A switch connected between the negative phase A rectifier and the dc common return, the negative phase A switch operating when the phase A input current Ia is negative and the negative phase A switch;

a negative phase B switch connected between the negative phase B rectifier and the dc common return, the negative phase B switch operating when the phase B input current Ib is negative and the negative phase B switch; and

a negative phase C switch connected between the negative phase C rectifier and the dc common return, the negative phase C switch operating when the phase C input current Ic is negative and the negative phase C switch.

16. The three phase buck converter of claim 12 wherein

the at least a first phase A switch is a phase A primary switching circuit of a phase A isolation transformer and the at least a first phase A switch is connected to the input terminal of the inductor through the phase A isolation transformer and a phase A secondary rectifying circuit;

the at least a first phase B switch is a phase B primary switching circuit of a phase B isolation transformer and the at least a first phase B switch is connected to the input terminal of the inductor through the phase B isolation transformer and a phase B secondary rectifying circuit;

the at least a first phase C switch is a phase C primary switching circuit of a phase C isolation transformer and the at least a first phase C switch is connected to the input terminal of the inductor through the phase C isolation transformer and a phase C secondary rectifying circuit.

17. The three phase buck converter of claim 12 wherein the means for rectifying a phase A ac current Ia, the means for rectifying a phase B ac current Ib, the means for rectifying a phase C ac current Ic and the at least a first catch rectifier are synchronous rectifiers.

18. The three phase buck converter of claim 15 wherein the phase A switch, the negative phase A switch, the positive phase B switch, the negative phase B switch, the positive phase C switch and the negative phase C switch are ac switches;

and

the phase A rectifier, the negative phase A rectifier, the positive phase B rectifier, the negative phase B rectifier, the positive phase C rectifier and the negatives phase C rectifier are the positive phase A switch, the negative phase A switch, the positive phase B switch, the negative phase B switch, the positive phase C switch and the negatives phase C switch, respectively, operating as synchronous rectifiers as well as switches.

19. A three phase boost converter for converting a dc input to a three phase ac output current comprising:

a dc input and a dc common return;

a phase A output having a phase A ac current Ia having a nominal value of IpSinX,

where Ip is the desired peak value of the three phase ac output current and where X is the desired instantaneous phase angle of the phase A ac current;

a phase B output having a phase B ac current Ib having a nominal value of IpSin(X+120°

);

a phase C output having a phase C ac current Ic having a nominal value of IpSin(X+240°

);

an ac neutral output for connecting to the common connection of a Y connected three phase load;

an inductor having an input terminal and an output terminal;

a positive phase A switch connected between the phase A output and the output terminal of the inductor;

a positive phase B switch connected between the phase B output and the output terminal of the inductor;

a positive phase C switch connected between the phase C output and the output terminal of the inductor;

a negative phase A switch connected between the phase A output and the dc common return;

a negative phase B switch connected between the phase B output and the dc common return;

a negative phase C switch connected between the phase C output and the dc common return;

a positive synchronous rectifier connected between the neutral ac output and the output of the inductor for conducting the current in the inductor when there is not at least one of the positive phase A switch, the positive phase B switch and the positive phase C switch in an on state;

a negative synchronous rectifier connected between the dc common return and the ac neutral output for conducting the current in the inductor when there is not at least one of the negative phase A switch, the negative phase B switch and the negative phase C switch in an on state;

means for controlling the switching of the positive phase A switch so that the positive phase A switch has a duty cycle Da equal to K|SinX| when the phase A output current Ia is positive,

where K is a gain factor;

means for controlling the switching of the negative phase A switch so that the negative phase A switch has a duty cycle Da equal to K|SinX| when the phase A output current Ia is negative

means for controlling the switching of the positive phase B switch so that the positive phase B switch has a duty cycle Db equal to K|Sin(X+120°

)| when the phase B output current Ib is positive;

means for controlling the switching of the negative phase B switch so that the negative phase B switch has a duty cycle Db equal to K|Sin(X+120°

)| when the phase B output current Ib is negative;

means for controlling the switching of the positive phase C switch so that the positive phase C switch has a duty cycle Dc equal to K|Sin(X+240°

)| when the phase C output current Ic is positive;

means for controlling the switching of the negative phase C switch so that the negative phase C switch has a duty cycle Dc equal to K|Sin(X+240°

)| when the phase C output current Ic is negative;

- and

means for controlling the gain factor K so as to regulate the three phase ac output.

20. The three phase boost converter of claim 19 further comprising:

a three phase buck converter having input current control as the dc input of the three phase boost converter for converting a three phase ac input to a dc output and a dc common return, which is the dc input and the dc common return of the three phase boost converter, comprising;

a phase D input having a means for rectifying a phase D ac current Id having a nominal value of IqSinZ to a phase D rectified current |Id| having a nominal value Iq|SinZ|,

where Iq is the desired peak value of the three phase ac input current and where Z is the desired instantaneous phase angle of the phase D ac current;

a phase E input having a means for rectifying a phase E ac current Ie having a nominal value of IqSin(Z+120°

) to a phase E rectified current |Ie| having a nominal value Iq|Sin(Z+120°

)|;

a phase F input having a means for rectifying a phase F ac current If having a nominal value of IqSin(Z+240°

) to a phase D rectified current |If| having a nominal value Iq|Sin(Z+240°

)|;

at least a first phase D switch connected between the means for rectifying the phase D current and the input terminal of the inductor;

at least a first phase E switch connected between the means for rectifying the phase E current and the input terminal of the inductor;

at least a first phase F switch connected between the means for rectifying the phase F current and the input terminal of the inductor;

at least a first catch rectifier having an input rectifier terminal connected to the dc common return and an output rectifier terminal connected to the input of the inductor for conducting the current in the inductor when there is not at least one of the at least a first phase D switch, the at least a first phase E switch and the at least a first phase F switch in an on state;

means for controlling the switching of the at least a first phase D switch so that the phase D switch has a duty cycle Dd equal to M|SinZ|,

where M is a gain factor;

means for controlling the switching of the at least a first phase E switch so that the phase E switch has a duty cycle De equal to M|Sin(Z+120°

)|; and

means for controlling the switching of the at least a first phase F switch so that the phase F switch has a duty cycle Df equal to M|Sin(Z+240°

)|.

21. The three phase boost converter of claim 19 further comprising:

a three phase buck converter having input current control as the dc input of the three phase boost converter, for converting a three phase ac input to a dc output and a dc common return, which are the dc input and the dc common return of the three phase boost converter, comprising;

a phase D input having a means for rectifying a phase D ac current Id having a nominal value of IqSinZ to a phase D rectified current lidl having a nominal value Iq|SinZ|,

where Iq is the desired peak value of the three phase ac input current and where Z is the desired instantaneous phase angle of the phase D ac current;

a phase E input having a means for rectifying a phase E ac current le having a nominal value of IqSin(Z+120°

) to a phase E rectified current |Ie| having a nominal value Iq|Sin(Z+120°

)|;

a phase F input having a means for rectifying a phase F ac current If having a nominal value of IqSin(Z+240°

) to a phase D rectified current |If| having a nominal value Iq|Sin(Z+240°

)|;

at least a first phase D switch connected between the means for rectifying the phase D current and the input terminal of the inductor;

at least a first phase E switch connected between the means for rectifying the phase E current and the input terminal of the inductor;

at least a first phase F switch connected between the means for rectifying the phase F current and the input terminal of the inductor;

at least a first catch rectifier having an input rectifier terminal connected to the dc common return and an output rectifier terminal connected to the input of the inductor for conducting the current in the inductor when there is not at least one of the at least a first phase D switch, the at least a first phase E switch and the at least a first phase F switch in an on state;

and wherein at any instant of time

the one of the phase D ac current, the phase E ac current and the phase F ac current that has the highest magnitude is designated the phase 1 current and its current magnitude is designated as I1;

the one of the phase D ac current, the phase E ac current and the phase F ac current that has the second highest magnitude is designated the phase 2 current and its current magnitude is designated as I2

the one of the phase D ac current, the phase E ac current and the phase F ac current that has the lowest magnitude is designated the phase 3 current and its current magnitude is designated as I3

the one of the at least a first phase D switch, the at least a first phase E switch and the at least a first phase F switch that has the same phase as phase 1 is designated as switch 1 and its duty cycle is designated as D1

the one of the at least a first phase D switch, the at least a first phase E switch and the at least a first phase F switch that has the same phase as phase 2 is designated as switch 2 and its duty cycle is designated as D2

the one of the at least a first phase D switch, the at least a first phase E switch and the at least a first phase F switch that has the same phase as phase 3 is designated as switch 3 and its duty cycle is designated as D3

a means for controlling the switching of switch 1, switch 2 and switch 3 such that

the duty cycle D1 of switch 1 terminates when the current in the inductor equal a reference current as determined by a means for feedback control to precisely control the dc output current Vo;

the duty cycle D2 of switch 2 is controlled to be

$\mathrm{D2}=\mathrm{D1}<br><br>\frac{\mathrm{I2}}{\mathrm{I1}}$

and the duty cycle D3 of the switch 3 is controlled to be

$\mathrm{D3}=\mathrm{D1}<br><br>\frac{\mathrm{I3}}{\mathrm{I1}}.$