Methods for Parameter Identification, Load Monitoring and Output Power Control in Wireless Power Transfer Systems

• US 20160181824A1
• Filed: 08/06/2014
• Published: 06/23/2016
• 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
• Granted Patent: US 10,224,751 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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, 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_in), 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 (l=1, 2, . . . n).

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, 8, and 4.

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

domino WPT system or any other structure of WPT system 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 the capacitor connected to the 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, comprises:

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

determining a set of measured input impedance 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; and

determining the load only based on the sensed input voltage U₁, the sensed input current I₁, and the identified impedance related parameters.

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

calculating the load Z_L by the equation of

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

determining the terms Z_LI_n and I_n based on the following equation;

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

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

P_out=I_n²Rc(Z_L).

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

determining efficiency η

of the WPT system based on the following equation;

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

determining 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, comprises:

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

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

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

(b.1) if the result of the step of determining is yes, the method further comprises;

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

of the WPT system according to the method of claim 12;

(b.2) if the result of the step of determining is no, the method further comprises;

determining a set of measured input impedance based on the sensed input voltage U₁ and the sensed input current I₁,

identifying impedance related parameters in the WPT system according to the method of any one of claim 1-6,

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

of the WPT system according to the method of claim 12;

(c) generating feedback information based on the estimated parameters in step (b.1) or (b.2); and

(d) controlling the operations of the transmitter coil based on the generated feedback information.