Incompletely compensated wireless power transfer system
AssigneeZhejiang University
InventorsWenxing Zhong, Dehong Xu
Life of this patent
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Abstract
Disclosed in the present application is an incompletely compensated wireless power transfer system. On the basis of an SS compensated wireless power transfer system topology, a primary side capacitor C1 and a secondary side capacitor C2 take specific values, and in combination with a phase shift frequency modulation control method, a coupling range of a system output rated power is improved. According to the present application, by finding an appropriate combination of the primary side capacitor C1 and the secondary side capacitor C2, the system can output a required rated power in a larger coupling range under the condition of incomplete compensation.
Claims4
An incompletely compensated wireless power transfer system, comprising:
- two coils and two compensation capacitors, wherein on basis of an Series-Series (SS) compensated wireless power transfer system topology, a primary side compensation capacitance C1 and a secondary side compensation capacitance C2 take specific values, and a phase shift frequency modulation control method is combined, to increase a coupling range of rated output power of the system;
- values of the primary side compensation capacitance C1 and the secondary side compensation capacitance C2 are obtained by a first method described below:
- 1) circuit equations of a wireless charging transfer system:
- (R1+jX1)I1+jωM12I2=V1 (1)
- jωM12I1+(R2+RL+jX2)I2=0 (2)
- where Ri, i=1 or 2, is parasitic resistance, generally including coil resistance and equivalent series capacitor resistance;
- Xi=ωLi−1/(ωCi), i=1 or 2, is reactance of a harmonic oscillator i;
- Li, Ci, i=1 or 2, are coil inductance and compensation capacitance, I1 and I2 are current phasors of a primary loop and a secondary loop respectively;
- V1 is input voltage phasor;
- M12 is mutual inductance of the two coils;
- RL is equivalent load resistance;
- ω=2πf is angular frequency, and f is frequency of a power supply;
- 2) with rated output direct current (DC) voltage Vout and power Pout, the equivalent load resistance is obtained by:
- R
- L
- =
- 8
- π
- 2
-
- V
- out
- P
- out
- (
- 3
- )
- 3) range of operating frequency is given by:
- fmin≤f≤fmax (4)
- wherein fmin is a minimum value of f and fmax is maximum value of f;
- 4) coupling range of the two coils is obtained by:
- M12min≤M12≤M12max (5)
- wherein M12min is a minimum value of M12 and M12max is a maximum value of M12;
- 5) based on DC input voltage VDC, through a phase shift control, V1_r is an effective value of a fundamental wave of a square wave applied to a primary LC harmonic oscillator is limited by:
- V
- 1
-
- _
-
- r
- ≤
- 2
-
- 2
- π
-
- V
- D
-
- C
- (
- 6
- )
- 6) maximum primary current I1max, is obtained by:
- I1≤I1max (7)
- where, I1 is an effective value of the current phasor I1;
- 7) a primary input current configured to lag behind an input square wave to achieve zero voltage turn-on, is obtained by:
- θ
- +
- 90
-
- °
- -
- arcsin
-
- (
- π
-
- V
- 1
- 2
-
- 2
- ·
- V
- D
-
- C
- )
- <
- 0
- (
- 8
- )
- where θ is a phase angle of the primary input current phasor I1 with respect to an input voltage phasor V1, and V1 is an effective value of a fundamental wave of an inverter output square wave:
- V
- 1
- =
- 2
-
- 2
- π
-
- V
- D
-
- C
-
- sin
-
- (
- α
- 2
- )
- ;
- (
- 9
- )
- α is an angle occupied by a half wave of the inverter output square wave, and is 180° when a duty cycle of the inverter output square wave is 1;
- 8) calculating the coil resistance via a finite element simulation;
- the equivalent series resistance of a compensation capacitor configured to be estimated by the following method:
- the coil inductance is Li, then the compensation capacitance Ci is approximately resonance capacitance value Ci0, and a calculation method of the resonance capacitance value and corresponding equivalent series resistance is as follows:
- C
- i0
- =
- 1
- ω
- 2
-
- L
- 1
- ;
- (
- 10
- )
- R
- C
-
- i
- ≈
- tan
-
- δ
- ω
-
- C
- i0
- ;
- (
- 11
- )
- where tan δ is a tangent value of a loss angle of the compensation capacitor;
- when in simplified calculation, the parasitic resistance is neglected;
- for given coils L1 and L2, in combination with above operating conditions, ranges of C1 and C2 that simultaneously meet conditions is obtained by a numerical solution method.
Dependencies are inferred from the claim text.