CN112234722B - S-LCC type inductive power transmission system and dynamic tuning method thereof - Google Patents
S-LCC type inductive power transmission system and dynamic tuning method thereof Download PDFInfo
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Abstract
The invention discloses an S-LCC type induction type electric energy transmission system and a dynamic tuning method thereof, which are characterized by comprising the following steps: the frequency tracking and adjusting module is used for detecting the output current of the inverter and adjusting the working frequency of the inverter according to the output current so that the system works in a preset range of high bifurcation frequency of the system under an over-coupling condition. According to the invention, through frequency tracking, the power of the system is improved under the over-coupling condition when the system works near the high-bifurcation frequency, and the voltage stress of components is reduced.
Description
Technical Field
The invention belongs to the technical field of electric energy transmission, and particularly relates to an S-LCC type inductive electric energy transmission system and a dynamic tuning method thereof.
Background
Inductive Power Transfer (IPT) technology has the advantages of large transmission Power, high transmission efficiency, no need of physical connection and the like, and thus is widely applied to the fields of material handling, electric vehicles, electronic equipment, medical equipment, underwater environment and the like. In order to ensure that the IPT system obtains high transmission efficiency and transmission power, the primary side circuit and the secondary side circuit of the IPT system are subjected to resonance compensation, and a typical IPT system working principle diagram is shown in fig. 1. The traditional compensation methods are based on SS, SP, PS and PP types. Of the four compensation modes, the resonant frequencies of the SP, PS and PP systems are affected by the load and the coupling coefficient, so that the SS topology is relatively widely applied. However, the output characteristics of the SS topology are highly dependent on the coupler parameters, resulting in a low degree of freedom in designing system parameters. In order to improve the freedom degree of parameter design of an IPT system, researchers provide topological structures such as an LCC type. For the bilateral LCC structure, although the degree of freedom of parameter design is high, the frequency characteristic is too complex to be applied to a frequency conversion system. Therefore, the invention selects S-LCC type topology as a research object. The S-LCC is a compensation topological structure of the circuit, and refers to a compensation topological structure with a primary side compensated through capacitance series resonance and a secondary side compensated through capacitance-inductance-capacitance.
In IPT systems, Zero Voltage Switching (ZVS) operation is important to improve system efficiency and reduce electromagnetic interference (EMI). To date, many methods have been proposed to achieve ZVS operation, including fixed frequency systems and variable frequency systems.
However, in the prior art, the IPT system usually works in an under-coupled state and is designed to be charged at a fixed distance, so that the difficulty of output control and the difficulty of system design are reduced. However, when the IPT system is applied to an underwater environment, for example, when a parked electric ship is charged, the longitudinal charging distance is difficult to control accurately, and strong disturbance of an external environment can cause the distance between a transmitting coil and a receiving coil to change rapidly, so that mutual inductance parameters of a coupler of the IPT system can change correspondingly, and further the system loses a soft switching condition, the efficiency of the system is reduced, and greater electromagnetic interference is caused; when the working distance is suddenly reduced, the IPT system enters an over-coupled abnormal working state from an under-coupled normal working state. At this time, for the abnormal working condition, the output power of the IPT system with a plurality of topological structures can be sharply reduced. For this reason, it is necessary to solve the problem that operation of the IPT system over a wide range of distances results in system detuning and output power variation.
Aiming at the problem of detuning of an IPT system, two dynamic tuning methods are mainly adopted at present: (1) tuning parameters such as inductance and capacitance of the system by an impedance matching method to enable the system to recover a resonance state; (2) the resonant frequency of the system is tracked by controlling and adjusting the switching frequency of the IPT system, so that the system works in a resonant state.
For the problem of power drop, power regulation is mainly realized by two methods: (1) performing phase shift control on a transmitting end high-frequency inverter; (2) the DC/DC module is cascaded before the transmitting end high-frequency inverter or after the receiving end rectification filtering.
Although the method can realize the detuning control and the power regulation of the IPT system within a certain range, the control is basically carried out under the condition of under-coupling, and the range of the power regulation is limited. When external disturbance occurs and the IPT system enters an over-coupling state from an under-coupling state, the output power is sharply reduced, and the adjusting ranges of common phase-shifting control and DC/DC control are insufficient, so that the method cannot realize the improvement of the output power under the over-coupling condition.
Disclosure of Invention
In view of at least one of the drawbacks or needs for improvement in the prior art, the present invention provides an S-LCC type inductive power transfer system and a dynamic tuning method thereof, which achieve power boosting by enabling the system to operate near a bifurcation frequency under an over-coupling condition through frequency tracking, and reduce voltage stress of components.
To achieve the above object, according to a first aspect of the present invention, there is provided an S-LCC type inductive power transfer system comprising: the frequency tracking and adjusting module is used for detecting the output current of the inverter and adjusting the working frequency of the inverter according to the output current so that the system works in a first preset range of high branching frequency of the system under the over-coupling condition.
Preferably, when the operating frequency of the inverter is adjusted according to the output current, the system is further enabled to operate in a second preset range of the system resonant frequency under the under-coupled condition.
Preferably, the frequency tracking and adjusting module includes a current detecting module, a zero-crossing comparing module, a phase-locked loop module and a driving circuit module, the current detecting module is configured to detect the output current of the inverter, the zero-crossing comparing module is configured to generate a square wave signal having the same frequency and phase as the output current according to the output current, the phase-locked loop module is configured to adjust the frequency of the output signal of the phase-locked loop module according to the phase difference between the square wave signal and the output signal of the phase-locked loop module, and the driving circuit module is configured to drive the S-LCC type resonator according to the output signal of the phase-locked loop module.
Preferably, the adjusting the frequency of the output signal of the phase-locked loop module includes:
presetting a phase angle threshold interval for the output impedance angle of the primary side of the S-LCC type resonator, wherein the phase angle threshold interval meets the condition that the system works under the weak inductance condition;
if the phase difference is smaller than the phase angle threshold interval, increasing the output signal frequency of the phase-locked loop module;
and if the phase difference is larger than the phase angle threshold interval, reducing the frequency of the output signal of the phase-locked loop module.
Preferably, the inverter comprises a voltage gain control module, wherein the voltage gain control module is used for detecting a voltage or current signal of a system load and adjusting the input voltage of the inverter according to the voltage or current signal of the system load.
Preferably, the voltage gain control module includes a field effect transistor, a driving circuit, a controller and a detection module, the field effect transistor is connected in series with the input end of the inverter module, the detection module is used for detecting a voltage or current signal of a system load, the controller is used for receiving a detection signal of the detection module and generating a control signal to control the driving circuit, and the driving circuit generates a PWM signal according to the control signal of the controller to control on and off of the field effect transistor.
Preferably, the S-LCC type resonator comprises a transmitter coil, a receiver coil, a series compensation capacitance (Cp) of the transmitter coil, a series compensation capacitance (Cs) of the receiver coil, a series compensation inductance (L) of the receiver coil2) Parallel compensation capacitance (C) with receiver coil2）。
Preferably, the over-coupling condition is determined by a transmitter coil inductance, a receiver coil inductance, a series compensation inductance of a receiver coil, a resonant frequency of the S-LCC type resonator, and an equivalent load resistance at an output terminal of the S-LCC type resonator.
According to a second aspect of the present invention, there is provided a dynamic tuning method of an S-LCC type inductive power transfer system comprising an inverter module for outputting a current signal to a primary side of an S-LCC type resonator and an S-LCC type resonator having a secondary side for supplying a voltage to a load, the dynamic tuning method comprising the steps of: and detecting the output current of the inverter, and adjusting the working frequency of the inverter according to the output current, so that the system works in a preset range of high bifurcation frequency of the system under an over-coupling condition.
Preferably, when the operating frequency of the inverter is adjusted according to the output current, the system is further enabled to operate in a preset range of the system resonant frequency under the condition of under-coupling.
In general, compared with the prior art, the invention has the following beneficial effects: a dynamic regulation strategy under an over-coupling condition is provided, ZVS operation is realized by regulating the working frequency of the system through frequency tracking regulation module frequency modulation, and the output power can be greatly improved by controlling the system to work near a high bifurcation frequency under the over-coupling condition, so that the constant power output is realized without excessively increasing the voltage of the inverter, and the voltage stress of components is reduced; and the constant power output is realized by adjusting the output voltage gain through a high-frequency inverter front-end voltage adjusting circuit.
Drawings
Figure 1 is a schematic diagram of the operation of an IPT system of an embodiment of the invention;
FIG. 2 is a circuit diagram of a dynamic tuning circuit for an S-LCC type IPT system of an embodiment of the present invention;
FIG. 3 is an equivalent circuit of an S-LCC type IPT system of an embodiment of the invention;
FIG. 4 is a schematic diagram of frequency bifurcation of an IPT system of the S-LCC type in accordance with an embodiment of the present invention;
FIG. 5 is a schematic diagram of equivalent load voltage gain of an S-LCC type IPT system according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of the output efficiency of an S-LCC type IPT system of an embodiment of the invention;
FIG. 7 is a schematic diagram of the operation of a phase-locked loop of an S-LCC type IPT system according to an embodiment of the present invention;
fig. 8 is a frequency characteristic curve of an S-LCC type IPT system of an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An S-LCC type inductive power transfer system according to an embodiment of the present invention includes: the frequency tracking and adjusting module is used for detecting the output current of the inverter and adjusting the working frequency of the inverter according to the output current so that the system works in a first preset range of high branching frequency of the system under the over-coupling condition. The first preset range is an allowable range around a preset high bifurcation frequency.
Preferably, when the operating frequency of the inverter is adjusted according to the output current, the system is further enabled to operate in a second preset range of the system resonant frequency under the under-coupled condition. The second preset range is an allowable range around the preset system resonance frequency.
Preferably, the S-LCC type inductive power transfer system further includes a voltage gain control module, wherein the voltage gain control module is configured to detect a voltage or current signal of a system load, and adjust an input voltage of the inverter according to the voltage or current signal of the system load.
Possible specific implementations are described below.
(1) General framework and working principle of S-LCC type induction type electric energy transmission system
The embodiment of the invention provides an S-LCC type induction type electric energy transmission system, wherein a frequency tracking and adjusting module comprises a current detection module, a zero-crossing comparison module, a phase-locked loop module and a driving circuit module, and a voltage gain control module is a Buck circuit. The working frequency is adjusted through the phase-locked loop, so that the system works under the ZVS condition, the output voltage of the inverter is adjusted through the front-end Buck circuit, the output voltage gain is further controlled, the system output is kept constant, and the structure diagram of the system is shown in FIG. 2.
The topology of the main circuit comprises a Buck converter, a high frequency full bridge inverter, a series inductor-capacitor (S-LCC) resonant network and a rectifier. In the context of figure 2 of the drawings,
is the power switch of the primary side F-B inverter.
Is a DC power supply, and is converted into high-frequency output voltage by a full-bridge inverter circuit
。
And
the self-inductance of the transmitter coil and the receiver coil, respectively.
And
are series compensation capacitors on the primary side and the secondary side, respectively.
Is a series compensated inductance.
Is a parallel compensation capacitor.
Is the mutual inductance between the coils. The high-frequency AC on the secondary side outputs DC to the load side through the rectifier circuit.
Is a load resistor with an output dc voltage.
Is the equivalent load of the system.
The designed system control circuit can be divided into two parts, namely a Buck control circuit and a ZVS control circuit (frequency tracking and adjusting module). The two control loops are decoupled.
The embodiment of the invention provides a sectional control strategy of an S-LCC type topological structure under an over-coupling condition, wherein a ZVS control circuit controls a system to work near a resonant frequency under an under-coupling condition; aiming at the problem of rapid reduction of output power under the over-coupling condition, the power is improved by controlling a system to work near a high bifurcation frequency through a ZVS (zero voltage switching) control circuit, and the constant power output is regulated by combining a front-end Buck converter.
(2) Dynamic tuning method under over-coupling condition
a) IPT system over-coupling power reduction mechanism analysis
And in consideration of the energy transfer characteristics of the coupling coil, the S-LCC-IPT system equivalent circuit diagram shown in FIG. 3 can be obtained by simplifying the system structure shown in FIG. 2.
、
The equivalent internal resistances of the coils of the primary side and the secondary side respectively,
the mutual inductance between the primary coil and the secondary coil and the self-inductance of the coil are satisfied
Wherein the content of the first and second substances,
called the coupling coefficient, is influenced by the parameters of the coils themselves and the relative positions between the coils.
In the context of figure 3, it is shown,
respectively corresponding to the mesh current, and the impedance values of the elements are respectively
、
、
、
、
、
(ii) a Definition of
Is the transimpedance. According to kirchhoff's voltage law, the corresponding voltage equation can be written as
The notation as a matrix is
Wherein the content of the first and second substances,
、
、
、
、
、
。
for the sake of simplifying the operation, equation (3) is written as
Thus, a current vector can be obtained as
The mesh current of the system can be derived from equation (4) as
The output power of the system can be derived from the formula (5) to be
When the primary side and the secondary side both meet the reactive compensation condition, the system is in a resonance state, namely, works at a resonance frequency
Above, the resonance parameter needs to be satisfied
、
、
. Because the internal resistance of the coil is far smaller than the load resistance, the influence on the output power of the system is small, and the efficiency of the system is mainly influenced. Neglecting coil internal resistance in order to obtain more concise output expression
、
The output power of the system can be derived as
The relation between the output power and the coupling coefficient of the S-LCC-IPT system is reflected very intuitively by the formula (7). If the change of the parameters caused by the reduction of the relative distance of the coils is not considered, the output power under the ideal condition is inversely proportional to the square of the coupling coefficient. Under the normal working distance, the system is generally under an under-coupling condition, and the coupling coefficient is usually designed to be between 0.1 and 0.3; when the relative distance of the coil is sharply reduced, the coupling coefficient of the IPT system is increased to 0.5-0.7 from the under-coupling stage to the over-coupling stage, so that the output power is reduced by several times. If the power boost is achieved by merely regulating the inverter input voltage by the BUCK converter, the voltage stress of the device is significantly increased.
b) Bifurcation frequency determination
The frequency bifurcation phenomenon of the S-LCC-IPT system is analyzed, an analytic expression of bifurcation frequency is obtained, and then the relationship between the frequency bifurcation and parameters such as mutual inductance is analyzed.
Firstly, the ratio of the output voltage and the current of the inverter is defined as the equivalent input impedance of the primary side. The equivalent input impedance of the primary side obtained from the equation (5) is
After finishing, the product is obtained
The primary side input impedance angle obtained from the equation (9) is
Real part of primary side input impedance angle
Reflects the transmission capability of active power, and the imaginary part
The magnitude of the reactive power is reflected, and the primary side input impedance angle reflects the detuning condition. In order to reduce the apparent power of the power source end and to make the system in the ZVS state, the system is usually made to work in a weak-inductance state, i.e. the primary side output impedance angle is controlled within a certain range, and the engineering implementation is usually about 15 degrees.
For ease of analysis, the normalized angular frequency is defined as
When the system is operated at Zero Phase Angle (ZPA), that is, the system satisfies
When in use
When the working frequency is equal to the resonance frequency of the system, the system is in a resonance state. If present, is
When the equation (11) is satisfied by the plurality of angular frequencies, the system exhibits a frequency bifurcation phenomenon. The system can only work at the resonance frequency or the bifurcation frequency, and the primary side power factor is 1. In order to obtain the boundary condition of the frequency bifurcation of the S-LCC type structure, the equation (11) needs to be solved, and the equation (11) is simplified layer by layer to obtain the variable
Fourth order equation of (2)
Wherein the content of the first and second substances,
and is and
each coefficient being
If there is a real root in equation (12)
And is and
then the system has a bifurcation frequency, otherwise the system will not have a frequency bifurcation. The process of solving equation (12) is very difficult, the root of the equation can be determined according to the formula of solving the fourth root of the unitary equation, and the discriminant is firstly defined
Wherein the content of the first and second substances,
considering the practical situation, the solution of equation (12) can be divided into the following three cases:
case 1: when in use
Then equation (12) must have two unequal real roots, whose solution is
At this time, the high bifurcation frequency means solution
。
Wherein the content of the first and second substances,
as a function of the sign, the other parameters are as follows
Case 2: when in use
And is
When, then the equation has four unequal solid roots, each being
Wherein the content of the first and second substances,
at this time, the high bifurcation frequency means solution
。
Case 3: when it is satisfied with
And is
At this time, the equation only has an imaginary root, so that the system does not have frequency bifurcation.
In conclusion, the frequency bifurcation characteristic of the S-LCC topological structure is deduced, and when the frequency bifurcation characteristic is satisfied
Or
Then, an analytic solution of the fork frequency can be obtained as
，
Is the real root of the equation that satisfies the boundary condition. For some cases where frequency forking needs to be avoided, it needs to be satisfied
And is
。
In the following, a frequency bifurcation condition of a system is simulated, and considering that an air gap exists between actual couplers, even if the working distance of the couplers is reduced to 0, the coupling coefficient cannot be very large due to factors such as package thickness, and the like, the distance range of the couplers tested in the text is 0-20 cm, and the variation range of the coupling coefficient is 0.13-0.68. Thus, the coupling coefficient of the simulation parameter is set
The variation range is 0.1-0.7, the setting range of equivalent load resistance parameters is 20-50 ohms, and the resonant cavity parameters are shown in table 1. The frequency bifurcation behavior of the IPT system of the S-LCC type topology is simulated and analyzed by combining the analytic expression (14) and the analytic expression (15),the variation relationship of the frequency bifurcation behavior of the S-LCC type topology along with the coupling coefficient under different loads obtained by MATLAB simulation is shown in FIG. 4, and the load resistance is 20 ohms, 30 ohms, 40 ohms and 50 ohms in sequence.
As can be seen from fig. 4, under the given system parameters, the S-LCC type topology does not have frequency bifurcation under the under-coupled condition; as the coupling coefficient increases, beyond a certain critical coupling coefficient, the system begins to experience a frequency bifurcation phenomenon. The critical value discriminant
Determination of the value of, the magnitude of and the system parameters
Resonant frequency of
And equivalent load resistance
In general, for a high-power charging system, the resonant frequency needs to meet the international established standard, so that the resonant frequency can be combined with the actual load parameter
、
To design the target critical coupling coefficient
。
c) Voltage gain analysis at bifurcated frequencies
It has been analyzed above that under over-coupling conditions, the output power of the system at the resonant frequency is greatly reduced. This section will demonstrate that boosting of the output power can be achieved at high bifurcation frequencies. Therefore, the power characteristics of the S/LCC type topological structure are analyzed, and the change of the system output power along with the coupling coefficient on the bifurcation frequency is researched.
To simplify the analysis, the equivalent load output voltage gain is defined as
. The original problem can be equivalent to analyzing the voltage gain
Following the variation of the coupling coefficient at the fork frequency, the voltage gain of (3) is obtained
By substituting the analytical solution of the branch frequency obtained by equations (14) and (15) into equation (16), the voltage gain at the branch frequency can be obtained
。
The change relation of the equivalent load output voltage gain of the S-LCC-IPT system on the bifurcation frequency along with the coupling coefficient is obtained through MATLAB simulation and is shown in figure 5, the load resistance is 20 ohms, 30 ohms, 40 ohms and 50 ohms in sequence, and the coupling coefficient is 0.1-0.7.
As can be seen from fig. 5, for the S-LCC type topology, (1) as the coupling coefficient increases, the equivalent load voltage gain at the resonant frequency is gradually decreasing; (2) as the coupling coefficient increases, the equivalent load voltage gain is gradually increased at the high branch frequency and gradually decreased at the low branch frequency. Thus, the system output power under over-coupling conditions can be increased by operating the system near the high bifurcation splitting frequency.
d) Output efficiency analysis
The above analyzes that the voltage gain is greatly increased when the over-coupled system works at the high branch frequency, and this part analyzes the change condition of the output efficiency when the system works at the high branch frequency. The influence of the internal resistance of the coil needs to be considered. From the definition of efficiency
The variation relation of the equivalent load output efficiency of the S-LCC-IPT system on the high bifurcation frequency and the like obtained by MATLAB simulation along with the coupling coefficient is shown in figure 6, the load resistance is 30 ohms, and the coupling coefficient is between 0.1 and 0.7
According to the efficiency curve of the IPT system, the output efficiency of the system working on the resonant frequency is gradually increased along with the increase of the coupling coefficient; when the coupling coefficient exceeds the critical coupling, the output efficiency of the system working at the high branch frequency is gradually reduced along with the increase of the coupling coefficient, but the output efficiency of the system is maintained to be more than 0.9 as a whole, so that the system working at the high branch frequency has higher efficiency.
e) Dynamic tuning system implementation
The embodiment of the invention provides an S-LCC type induction type electric energy transmission system, which enables the system to work under the ZVS condition by adjusting the working frequency through a phase-locked loop and controls the output voltage gain by adjusting the output voltage of an inverter through a front-end Buck circuit, so that the output power of the system is kept constant, and the structure diagram of the system is shown in figure 2.
The ZVS control loop provided by the embodiment of the invention essentially keeps constant phase of output voltage and output current of the inverter through frequency tracking control, so that the system is in a weak inductance state, and comprises current detection, zero-crossing comparison, a phase-locked loop and a driving circuit. The phase-locked loop includes a phase detector, a loop filter, and a voltage-controlled oscillator, as shown in fig. 7 (a), and the corresponding mathematical model is shown in fig. 7 (b).
Firstly, the output current of the inverter is detected
Through a zero-crossing comparison circuit to generate a sum
Square wave signal with same frequency and phase
. Suppose that
，
With feedback signal generated by voltage-controlled oscillator
Comparing to generate a phase difference signal
. Defining the current control voltage
At 0, the signal frequency is
Then, then
Can be written as
(ii) a In the same way, can
Is shown as
Whereby the phase difference signal is
Wherein the content of the first and second substances,
is the phase difference. The frequency difference can be obtained by taking the derivative of the phase difference
When the phase difference is a constant value, the frequency difference is zero, and phase locking is realized.
In order to ensure that the system is in a ZVS state, the system needs to work under the condition of weak sensitivity, and a threshold phase angle interval is set for the primary side output impedance angle
Carrying out simulation analysis on the formula (10) to obtain the angle-dependent coupling coefficient of the equivalent input impedance of the primary side of the S-LCC type topology IPT system
And normalizing the operating frequency
The relationship of (2) is shown in FIG. 8.
According to the frequency characteristic curve of the S-LCC-IPT system, under the over-coupling condition, the impedance angle value at the high-branching frequency is in positive correlation with the frequency, so that a frequency tracking strategy can be formulated: if the phase difference is smaller than the phase angle threshold interval, increasing the output signal frequency of the phase-locked loop module; and if the phase difference is larger than the phase angle threshold interval, reducing the frequency of the output signal of the phase-locked loop module. Specifically, it may be determined whether the system is in the over-coupling condition by detecting the output current signal of the inverter, and when the system is in the over-coupling condition, the frequency is increased to a preset 1.5 times of the resonant frequency, and it is determined whether the phase difference is present
Less than a given phase angle threshold interval, the signal frequency is increased
If there is a phase difference
Greater than a given phase angle threshold interval, the signal frequency is reduced
Until the phase difference is in the threshold interval. And in the voltage gain control link, the output voltage is compared with a reference voltage signal by detecting a voltage current signal at the load side to obtain an error signal, and then the error signal is regulated by PID to give a signal to the PWM generator, and the PWM signal controls the on and off of the MOSFET to realize the control of the input voltage of the inverter.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. An S-LCC type inductive power transfer system, comprising: the system comprises an inverter module, an S-LCC type resonator and a frequency tracking and adjusting module, wherein the inverter module is used for outputting a current signal to the primary side of the S-LCC type resonator, the secondary side of the S-LCC type resonator is used for providing voltage for a load, the frequency tracking and adjusting module is used for detecting the output current of the inverter module and adjusting the working frequency of the inverter module according to the output current, so that the system works in a first preset range of high branching frequency of the system under an over-coupling condition;
the S-LCC resonator comprises a transmitter coil, a receiver coil, a series compensation capacitance (Cp) of the transmitter coil, a series compensation capacitance (Cs) of the receiver coil, a series compensation inductance (L) of the receiver coil2) And a parallel compensation capacitance (C) of the receiver coil2）；
Establishing a working frequency solving model, and determining the high bifurcation frequency, wherein the working frequency solving model is as follows:
wherein the content of the first and second substances,
and is and
，
each coefficient being
Wherein the content of the first and second substances,
is the self-inductance of the transmitter coil,
is the self-inductance of the receiver coil, L2K is the coupling coefficient for the series compensation inductance of the receiver coil,
for the resonant frequency, Req is the system load resistance,
is the operating frequency.
2. An inductive power transfer system of the S-LCC type according to claim 1, wherein the adjustment of the operating frequency of said inverter module in response to said output current also causes the system to operate in an under-coupled condition within a second predetermined range of the system resonant frequency.
3. The S-LCC type inductive power transfer system of claim 1, wherein the frequency tracking adjustment module includes a current detection module, a zero-crossing comparison module, a phase-locked loop module and a driving circuit module, the current detection module is configured to detect the output current of the inverter module, the zero-crossing comparison module is configured to generate a square wave signal having the same frequency and phase as the output current according to the output current, the phase-locked loop module is configured to adjust the frequency of the output signal of the phase-locked loop module according to a phase difference between the square wave signal and the output signal of the phase-locked loop module, and the driving circuit module is configured to drive the S-LCC type resonator according to the output signal of the phase-locked loop module.
4. An inductive power transfer system of the S-LCC type according to claim 3, wherein said adjusting the frequency of the output signal of said phase locked loop module comprises the steps of:
presetting a phase angle threshold interval for the output impedance angle of the primary side of the S-LCC type resonator, wherein the phase angle threshold interval meets the condition that the system works under the weak inductance condition;
if the phase difference is smaller than the phase angle threshold interval, increasing the output signal frequency of the phase-locked loop module;
and if the phase difference is larger than the phase angle threshold interval, reducing the frequency of the output signal of the phase-locked loop module.
5. An inductive power transfer system of the S-LCC type according to claim 1, comprising a voltage gain control module for detecting a voltage or current signal of the system load and adjusting the input voltage of said inverter module in accordance with the voltage or current signal of the system load.
6. An inductive power transfer system of the S-LCC type according to claim 5, wherein the voltage gain control module comprises a fet, a driving circuit, a controller and a detection module, the fet is connected in series with the input terminal of the inverter module, the detection module is configured to detect a voltage or current signal of a system load, the controller is configured to receive a detection signal from the detection module and generate a control signal to control the driving circuit, and the driving circuit generates a PWM signal to control the fet to be turned on or off according to the control signal from the controller.
7. An inductive power transfer system of the S-LCC type according to claim 1, characterized in that said resonators of the S-LCC type comprise a transmitter coil, a receiver coil, a series compensation capacitance (Cp) of the transmitter coil, a series compensation capacitance (Cs) of the receiver coil, a series compensation inductance (L) of the receiver coil2) And a parallel compensation capacitance (C) of the receiver coil2）。
8. An inductive power transfer system of the S-LCC type according to claim 7, characterized in that said over-coupling condition is determined by the transmitter coil inductance, the receiver coil inductance, the series compensation inductance of the receiver coil, the resonance frequency of said S-LCC type resonator and the equivalent load resistance at the output of said S-LCC type resonator.
9. A method for dynamic tuning of an inductive power transfer system of the S-LCC type comprising an inverter module for outputting a current signal to a primary side of a resonator of the S-LCC type and a resonator of the S-LCC type for supplying a voltage to a load, characterized in that it comprises the steps of: detecting the output current of the inverter module, and adjusting the working frequency of the inverter module according to the output current so that the system works in a preset range of high bifurcation frequency of the system under an over-coupling condition;
the S-LCC resonator comprises a transmitter coil, a receiver coil, a series compensation capacitance (Cp) of the transmitter coil, a series compensation capacitance (Cs) of the receiver coil, a series compensation inductance (L) of the receiver coil2) And a parallel compensation capacitance (C) of the receiver coil2）；
Establishing a working frequency solving model, and determining the high bifurcation frequency, wherein the working frequency solving model is as follows:
wherein the content of the first and second substances,
and is and
，
each coefficient being
Wherein the content of the first and second substances,
is the self-inductance of the transmitter coil,
is the self-inductance of the receiver coil, L2K is the coupling coefficient for the series compensation inductance of the receiver coil,
for the resonant frequency, Req is the system load resistance,
is the operating frequency.
10. A method of dynamically tuning an inductive power transfer system of the S-LCC type according to claim 9, wherein adjusting the operating frequency of said inverter module in response to said output current also causes the system to operate in an under-coupled condition within a predetermined range of the system resonant frequency.
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