VAR CONTROL FOR INDUCTIVE POWER TRANSFER SYSTEMS

• US 20150035377A1
• Filed: 02/01/2013
• Published: 02/05/2015
• Est. Priority Date: 02/02/2012
• Status: Active Grant

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Auckland UniServices Limited (Auckland University)
• Inventors: Covic, Grant Anthony, Boys, John Talbot, James, Jason Edward Ian
• Granted Patent: US 11,277,027 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 3/1864 wherein the stepless control of reactive power is obtained by at least one reactive element connected in series with a semiconductor switch
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer
• CPC Class Codes: H02M 7/4818 with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuits
• 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

Abstract

Disclosed herein is an inductive power transfer (IPT) compensation circuit and method for reflecting a controlled reactance to a primary conductor at a selected operating frequency, compensating for reactive loads reflected to the primary conductor by one or more other pick-ups inductively coupled with the primary conductor in use. The compensation circuit comprises a first switch means coupled to a resonant circuit and operable to reflect a capacitive reactance to the primary conductor; a second switch means coupled to the resonant circuit and operable to reflect an inductive reactance to the primary conductor; and control means adapted to control operation of the first and second switch means to compensate for inductive and capacitive reactances, respectively, in the primary conductor.

Claims

1-6. -6. (canceled)

7. A method for controlling reactance in the primary conductor of an inductive power transfer (IPT) system, the method comprising:

sensing a variable reactance in the primary conductor; and

controlling a first reactive element associated with a resonant circuit of a compensation device inductively coupled with the primary conductor, dependent on the sensed reactance, to reflect a controlled compensatory reactance ameliorating the reactance in the primary conductor.

8. The method of claim 7, further comprising the step of selectively activating a passive compensation means prior to operation of the IPT system, to ameliorate a substantially constant component of reactance in the primary conductor, whereby the controlled compensatory reactance is minimized.

9. The method of claim 8, wherein the step of selectively activating the passive compensation means comprises coupling a capacitor in series with the primary conductor, or adjusting a frequency of a power supply supplying the primary conductor.

10. The method of claim 7, wherein the first reactive element is operable to reflect a capacitive reactance to ameliorate an inductive reactance in the primary conductor.

11. The method of claim 7, wherein the first reactive element is operable to reflect an inductive reactance to ameliorate a capacitive reactance in the primary conductor.

12. The method of claim 7, wherein the first reactive element comprises a capacitor selected to resonate with a series inductor at an operating frequency of the IPT system and thereby short an inductive pick-up of the resonant circuit inductively coupled with the primary conductor.

13. The method of claim 7, wherein the first reactive element comprises a capacitor selected to be controllable to have an effective capacitance resonant with a series inductor through a range of frequencies about an operating frequency of the IPT system.

14. The method of claim 13, wherein the capacitor is selected to be controllable to have an effective capacitance ranging from zero to at least twice a capacitance resonant with the series inductor at the operating frequency.

15. The method of claim 7, further comprising the step of controlling a second reactive element associated with the resonant circuit, dependent on the sensed reactance, wherein the first reactive element is operable to reflect a capacitive reactance to ameliorate an inductive reactance in the primary conductor, and the second reactive element is operable to reflect an inductive reactance to ameliorate a capacitive reactance in the primary conductor.

16. The method of claim 15, further comprising the step of biasing the primary conductor towards a capacitive reactance, whereby the second reactive element is predominantly or exclusively operated in preference to the first reactive element, to minimise harmonics.

17. An inductive power transfer (IPT) compensation circuit for reflecting a controlled reactance to a primary conductor at a selected operating frequency, the circuit comprising:

a resonant circuit comprising a pick-up coil and a tuning capacitor, for inductive coupling with the primary conductor in use;

a controllable reactive element coupled to the resonant circuit and operable to reflect a compensatory reactance to the primary conductor; and

a controller operable to control the controllable reactive element to compensate for a sensed reactance in the primary conductor caused by a pick-up inductively coupled therewith, and thereby ameliorate reactance in the primary conductor.

18. The IPT compensation circuit of claim 17, wherein the controllable reactive element comprises a controllable capacitor in series with an inductor, and the controllable capacitor and series inductor are selected such that the controllable capacitor may be controlled to selectively reflect both an inductive and a capacitive reactance.

19. The IPT compensation circuit of claim 17, wherein the controllable reactive element is operable to reflect one of a substantially inductive or capacitive reactance, and the compensation circuit further comprises a second controllable reactive element operable to reflect the other of a substantially inductive or capacitive reactance.

20-42. -42. (canceled)

43. A primary inductive power transfer (IPT) resonator operable to transfer power to a secondary IPT resonator to form an IPT system having a nominal tuning state and a tolerance within the tuning state, wherein the tuning of the primary resonator circuit is adjustable such that a tuning range of the secondary IPT resonator is capable of adjusting the tuning state of the IPT system to the nominal tuning state of the system or within the tolerance of the nominal state.

44. The primary IPT resonator of claim 43, wherein the primary circuit comprises one or more controllable reactive components and/or one or more components operable to increment a frequency of the system so as to adjust the tuning of the primary resonator.

45-46. -46. (canceled)

47. An inductive power transfer (IPT) compensation circuit for reflecting a controlled reactance to a primary conductor at a selected operating frequency, the circuit comprising:

a resonant circuit comprising a pick-up coil and a tuning capacitor, for inductive coupling with the primary conductor in use;

a controllable reactive element coupled to the resonant circuit and operable to reflect a compensatory reactance to the primary conductor; and

control means operable to control the controllable reactive element to compensate for a sensed reactance in the primary conductor caused by a pick-up inductively coupled therewith, and thereby ameliorate reactance in the primary conductor.

48. The IPT compensation circuit of claim 47, wherein the controllable reactive element comprises a controllable capacitor in series with an inductor, and the controllable capacitor and series inductor are selected such that the controllable capacitor may be controlled to selectively reflect both an inductive and a capacitive reactance.

49. The IPT compensation circuit of claim 47, wherein the controllable reactive element is operable to reflect one of a substantially inductive or capacitive reactance, and the compensation circuit further comprises a second controllable reactive element operable to reflect the other of a substantially inductive or capacitive reactance.