Wireless charging system for electric vehicle (EV) batteries
A system and method for controlling output power in an LCC-series wireless power system based on one or more primary-side variables, such as a peak voltage in an LCC-series compensation circuit that is provided in conjunction with a primary coil for transmitting power wirelessly to an electric vehicle. The coupling factor between the primary coil and a receiver may be in the range of 0.1-0.5, and a target power level may be in a range of 50-150 kW.
1 . A wireless power transfer (WPT) system for wirelessly providing AC power to an electric vehicle or a plug-in electric vehicle, the system comprising:
an off-board module including:
a primary-side inverter configured to convert, during operation of the WPT system, a DC voltage to a high-frequency AC voltage;
a primary coil configured to wirelessly transmit the high-frequency AC voltage, the transmitted high-frequency AC voltage to be received by a pick-up coil of an onboard module of the WPT system when the pick-up coil is disposed adjacent to the primary coil;
a primary-side compensating network configured to couple the high-frequency AC voltage between the primary-side inverter and the primary coil;
sensing circuitry configured to measure a signal within the primary-side compensating network, wherein the measured signal is independent of
a coupling factor between the primary coil and the pick-up coil, the coupling factor being in a range of 0.1-0.5, and
a load to which the onboard module is coupled, a resistance of the load being in a range of 0.1-1.0 Ω;
controller circuitry configured to
store a reference value (Pref) corresponding to a target power level in a range of 50-150 kW to be output to the load by the onboard module, and
produce a feedback signal (Vin) using the measured signal (vc) and the reference value (Pref); and
driver circuitry configured to
produce a driving signal using the feedback signal (Vin), and
drive the primary-side inverter using the driving signal.
2 . The system of claim 1 wherein the sensing circuitry comprises peak-detection circuitry configured to track a peak of the signal measured within the primary-side compensating network.
3 . The system of claim 2 wherein the peak-detection circuitry comprises an operational amplifier-based precision full-wave rectifier circuit.
4 . The system of claim 1 wherein:
the primary-side compensating network is configured as an LCC-series network including a compensating capacitor Cp, a series inductor L, and a series capacitor C, and
the sensing circuitry is configured to measure a voltage signal vct across the series capacitor C.
5 . The system of claim 4 wherein the controller circuitry is configured to produce the feedback signal (Vin) in accordance with an error signal based on the measured signal (vc) and a target value Vcref determined as
V
cref
=
X
C
V
in
Z
1
V
i
n
4
+
4
P
ref
2
Z
1
2
,
where Xc is the capacitive reactance of the series capacitor C at resonance and Zl is the impedance of the series inductor L at resonance, Vin is a present value of the feedback signal, and Pref is the target power level.
6 . The system of claim 1 wherein a frequency of the fundamental component of the high-frequency AC voltage is 85 kHz.
7 . The system of claim 1 comprising the on-board module.
8 . A wireless power supply for wirelessly transmitting power to a receiver of a remote device, the wireless power supply comprising:
power supply circuitry operable to receive power from a power source, the power supply circuitry configured to output supply power;
switching circuitry operably coupled to the power supply circuitry, the switching circuitry configured to generate an AC voltage signal based on the output supply power received from the power supply circuitry;
a transmitter operably coupled to the switching circuitry, the transmitter configured to transmit power wirelessly to the receiver based on the AC voltage signal that is generated by the switching circuitry;
compensation circuitry operably coupled to the switching circuitry and the transmitter, the compensation circuitry configured as an LCC-series network to condition the AC voltage signal generated by the switching circuitry, the LCC-series network including a compensating capacitor Cp, a series inductor L, and a series capacitor C;
a sensor operable to provide sensor output indicative of a peak of a characteristic of power in the compensation circuitry, wherein the sensor is configured to measure a voltage signal Vct across the series capacitor C; and
a control system configured to direct operation of the switching circuitry based on the sensor output indicative of the peak of the characteristic of power in the compensation circuitry.
9 . The wireless power supply of claim 8 wherein the characteristic of power is a voltage signal in the compensation circuitry.
10 . The wireless power supply of claim 9 wherein the sensor is operable to detect a peak voltage of a capacitor provided in the compensation circuitry.
11 . The wireless power supply of claim 8 wherein the peak of the characteristic of power is independent of a coupling factor between the transmitter and the receiver, and wherein the peak of the characteristic of power is independent of a load of the remote device.
12 . The wireless power supply of claim 8 wherein the control system is configured to produce a feedback signal (Vin) in accordance with an error signal based on the peak of the characteristic of power (Vc) and a target value Vcref determined as
V
cref
=
X
C
V
in
Z
1
V
i
n
4
+
4
P
ref
2
Z
1
2
,
where Xc is the capacitive reactance of the series capacitor C at resonance and Zl is the impedance of the series inductor L at resonance, Vin is a present value of the feedback signal, and Pref is a target power level.
13 . The wireless power supply of claim 12 wherein the target power level is in a range of 50-150 kW.
14 . A wireless power supply for wirelessly transmitting power to a receiver of a remote device, the wireless power supply comprising:
power supply circuitry operable to receive power from a power source, the power supply circuitry configured to output supply power;
switching circuitry operably coupled to the power supply circuitry, the switching circuitry configured to generate an AC voltage signal based on the output supply power received from the power supply circuitry;
a transmitter operably coupled to the switching circuitry, the transmitter configured to transmit power wirelessly to the receiver based on the AC voltage signal that is generated by the switching circuitry;
compensation circuitry operably coupled to the switching circuitry and the transmitter, the compensation circuitry configured to condition the AC voltage signal generated by the switching circuitry;
a sensor operable to provide sensor output indicative of a characteristic of power in the compensation circuitry that is independent of a coupling factor between the transmitter and the receiver, wherein the characteristic of power is independent of a load of the remote device and is a peak of a voltage signal in the compensation circuitry, and the sensor is operable to detect a peak voltage of a capacitor (C) provided in the compensation circuitry; and
a control system configured to direct operation of the switching circuitry based on the sensor output indicative of the characteristic of power in the compensation circuitry.
15 . The wireless power supply of claim 14 wherein:
the compensation circuitry is configured as an LCC-series network including a compensating capacitor Cp, a series inductor L, and a series capacitor C, and
the sensor is configured to measure a voltage signal vct across the series capacitor C.
16 . The wireless power supply of claim 14 wherein the control system is configured to produce a feedback signal (Vin) in accordance with an error signal based on the peak of the characteristic of power (Vc) and a target value Vcref determined as
V
cref
=
X
C
V
in
Z
1
V
i
n
4
+
4
P
ref
2
Z
1
2
,
where Xc is the capacitive reactance of the series capacitor C at resonance and Zl is the impedance of the series inductor L at resonance, Vin is a present value of the feedback signal, and Pref is a target power level.
17 . The wireless power supply of claim 16 wherein the target power level is in a range of 50-150 kW.