Methods for parameter identification, load monitoring and output power control in wireless power transfer systems

• US 10,224,751 B2
• Filed: 08/06/2014
• Issued: 03/05/2019
• Est. Priority Date: 08/06/2013
• Status: Active Grant

• Current Assignee: University of Hong Kong (Government of Hong Kong Special Administrative Region)
• Original Assignee: University of Hong Kong (Government of Hong Kong Special Administrative Region)
• Inventors: Hui, Shu Yuen, Lin, Deyan, Yin, Jian, Lee, Chi Kwan
• Primary Examiner(s): Tran, Thienvu
• Assistant Examiner(s): Sun, Pinping
• Application Number:
  US14/910,560
• Publication Number:
  US 20160181824A1
• Time in Patent Office: 1,672 Days
• CPC Class Codes: B60L 53/12 Inductive energy transfer
• CPC Class Codes: G01N 27/02 by investigating impedance
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/50 using additional energy repeaters between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A method for identifying impedance related parameters in a wireless power transfer (WPT) system including n coils is disclosed. Said method includes determining optimum values of the impedance related parameters based on a set of measured input impedance by applying an evolutionary algorithm to solve optimum solutions. Wherein the set of measured input impedance includes an input impedance vector {right arrow over (Z)}=(Z₁, Z₂, . . . , Z_m−1, Z_m), each input impedance in the vector (Z_k) measured at different frequencies f_k, (k=1, 2, . . . m); and the impedance related parameters includes d_ll−1 representing a distance between the l-th coil and the l+1 coil (l=1, 2, . . . n−1) and C_i representing a capacitance of the capacitor connected to the i-th coil (i=1, 2, . . . n).

Claims

1. A method for identifying impedance related parameters in a wireless power transfer (WPT) system including n coils for maximizing an overall WPT system efficiency, the method comprising:

providing a wireless power transfer (WPT) system comprising;

an n number of coils arranged sequentially,

wherein a first coil of the n number of coils is a transmitting coil;

at least one capacitor connected to an i-th coil of the n number of coils;

a power source configured to be electrically connected to the first coil of the n number of coils and configured to drive a current through the first coil of the n number of coils;

a plurality of sensors configured to be electrically connected to the first coil of the n number of coils; and

a non-transitory computer readable medium configured to receive a signal from a sensor of the plurality of sensors and comprising stored instructions that when executed cause at least one processor to;

sense, by the sensor of the plurality of sensors, input impedances of the WPT system at different respective frequencies f_k,(k=1, 2, . . . m);

express the measured input impedances at the different respective frequencies as a following first matrix equation;

2. The method for identifying impedance related parameters of claim 1, wherein the input impedance vector is measured experimentally.

3. The method for identifying impedance related parameters of claim 1, wherein n is one of the following values:

3, 4, and 8.

4. The method for identifying impedance related parameters of claim 1, wherein the WPT system is one of the following:

a domino WPT system or any other WPT system structure with more than two coils.

5. The method for identifying impedance related parameters of claim 1, wherein a load for the WPT system is connected in series with or in parallel with a capacitor connected to an n-th coil.

6. The method for identifying impedance related parameters of claim 1, wherein the optimum solution solved by the evolutionary algorithm is as follows:

7. A method for monitoring a load Z_L in a wireless power transfer (WPT) system including n coils, the method comprising:

sensing only an input voltage U₁ and an input current I₁ of a transmitter coil of the n coils;

determining a set of measured input impedances based on the sensed input voltage U₁ and the sensed input current I₁;

identifying impedance related parameters according to the method of any one of claims 1-6;

describing the WPT in terms of the following second matrix equation;

8. The method for monitoring a load of claim 7, further comprising:

calculating the load Z_L by the equation of

9. The method for monitoring a load of claim 8, further comprising:

determining the terms Z_LI_nand I_n based on the following equation;

10. The method for monitoring a load of claim 9, further comprising:

determining a power P_out of the load Z_L, based on the following equation;

P_out=I_n²Re(Z_L).

11. The method for monitoring a load of claim 10, further comprising:

determining an efficiency η

of the WPT system based on one of the following equations;

12. The method for monitoring a load of claim 11, further comprising:

determining an output voltage U_o of the WPT system based on the following equation;

U_o=Z_LI_n.

13. A method for controlling output power in a wireless power transfer (WPT) system including n coils for maximizing an overall WPT system efficiency, the method comprising:

providing a wireless power transfer (WPT) system comprising;

an n number of coils arranged sequentially,

wherein a first coil of the n number of coils is a transmitting coil;

at least one capacitor connected to an i-th coil of the n number of coils;

a power source configured to be electrically connected to the first coil of the n number of coils and configured to drive a current through the first coil of the n number of coils;

a plurality of sensors configured to be electrically connected to the first coil of the n number of coils; and

a non-transitory computer readable medium configured to receive a signal from the a sensor of the plurality of sensors and comprising stored instructions that when executed cause at least one processor to;

(a) sense, by the sensor of the plurality of sensors, an input voltage U₁ and an input current I₁ of the first coil of the n number of coils;

(b) determine whether impedance related parameters in the WPT system are known, wherein the impedance related parameters include d_ll+1 representing a distance between an l-th coil and an l+1 coil (l=1, 2, . . . n−

1) and C_i representing a capacitance of the capacitor connected to the i-th coil (i=1, 2, . . . n);

(b.1) if the impedance related parameters in the WPT are known, the method further comprises;

based on the sensed input voltage U₁, the sensed input current I₁, and the known impedance related parameters, estimating a load Z_Lof the WPT system, an output current I_n of the WPT system, a power P_out of the load Z_L, an output voltage U_o of the WPT system, and an efficiency η

of the WPT system in the following manner;

calculate the load Z_L, by the equation of

14. The method of claim 13, wherein identifying impedance related parameters in the WPT system comprises:

determining optimum values of the impedance related parameters based on a set of measured input impedances by applying an evolutionary algorithm to solve for the optimum values,

wherein the set of measured input impedance includes an input impedance vector {right arrow over (Z)}=(Z₁, Z₂, . . . , Z<sub>m−

1</sub>, Z_m),each measured input impedance in the vector (Z_k) measured at- different respective frequencies f_k,(k=1, 2, . . . m),

wherein the impedance related parameters includes d_ll+1representing a distance between an l-th coil and an l+1 coil (l=1, 2, . . . n−

1) and C_i representing a capacitance of a capacitor connected to an i-th coil (i=1, 2, . . . n),

wherein a capacitance C_i of the capacitor connected to an i-th coil is configured to be adjustable to the determined optimum value of C_i; and

wherein a position of at least one coil of the n number of coils is configured to be adjustable to reach a distance equal to the determined optimum value of d_ll+1.

15. The method of claim 14, wherein the input impedance vector is measured experimentally.

16. The method of claim 14, wherein n is one of the following values:

3, 4, and 8.

17. The method of claim 14, wherein the WPT system is one of the following:

a domino WPT system or any other WPT system with more than two coils.

18. The method of claim 14, wherein a load for the WPT system is connected in series with or in parallel with a capacitor connected to an n-th coil.

19. The method of claim 14, wherein an optimum solution is solved by the following evolutionary algorithm: