CN218183082U

CN218183082U - Current-converting and rectifying constant-current mode wireless charging system

Info

Publication number: CN218183082U
Application number: CN202221945980.9U
Authority: CN
Inventors: 不公告发明人
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-07-26
Filing date: 2022-07-26
Publication date: 2022-12-30
Anticipated expiration: 2032-07-26

Abstract

The utility model discloses a constant current mode wireless charging system of unsteady flow rectification belongs to the wireless power transmission field. The system comprises: the device comprises an AC-DC conversion circuit (1), a DC-AC converter (2), a primary side compensation network (3), a primary side coil Lp, a secondary side coil Ls, a secondary side compensation network (4), a variable current rectifier (5) and a filter circuit (6). The primary side compensation network is in an LCC topology; the secondary side compensation network is a three-gain or double-gain CCL topology; the converter rectifier is a three-order or two-order converter topology. Establishing a design principle and a parameter formula of a coil and a compensation network, and providing a method for determining the size of a secondary side magnetic core; and dividing the coupling coefficient interval by taking the geometric progression as a boundary value, and controlling the switch state to realize multi-stage variable current rectification. The advantages are as follows: the bus voltage is narrowed to 760-535V; optimizing the current of the primary/secondary side coil to improve the heat dissipation of the secondary side; unifying the self-inductance of the primary/secondary coil and the secondary magnetic core; and the method is compatible with national standard topology and control mode.

Description

Current-converting and rectifying constant-current mode wireless charging system

Technical Field

The utility model relates to a constant current mode wireless charging system of unsteady flow rectification and design and control method thereof are wireless power transmission technique, belong to power electronics/wireless field of charging.

Background

In recent years, with the development of new energy automobile industry, wireless charging technology of electric automobiles also has a huge development prospect and is highly valued by the industry and the national level, and related international standards (SAE J2954, ISO 19363, iec 61980) and national standards are released successively. By 5/1/2022, 7 national standards (namely 7 parts) about GB/T38775. X electric vehicle wireless charging system have been promulgated and implemented in full.

The contents of the above-mentioned international sections 6 and 7 are the interoperability requirements and tests of the ground side and the vehicle side. In section 5, the ground equipment and the vehicle-mounted equipment are classified into a type a and a type B, and the type a equipment should meet the requirement of interoperability with the reference equipment in the standard appendix a. The core contents of the series of national standards are summarized as follows.

The rated output Power of an MF-WPT (Wireless Power Transfer Through Magnetic Field-based Wireless Power Transfer) system consisting of class A devices with different Power levels is shown in the following table.

A MF-WPT system formed by the A-type ground reference equipment and the A-type vehicle-mounted reference equipment recommended by the national standard adopts LCC-CCL topology for a primary side compensation network and a secondary side compensation network. The electrical architecture is shown in fig. 7.

Under different power levels, the main electrical parameters of the MF-WPT system formed by the class A equipment are as follows:

the minimum value L of the self-inductance of the primary coil of the A-type reference equipment under different ground clearances and different power levels _p-min And a maximum value L _p-max And the minimum value L of the self-inductance of the secondary coil _s-min And a maximum value L _s-max The minimum value k of the coupling coefficient of the primary coil and the secondary coil _min And a maximum value k _max And its compensation network parameters, are summarized in the following list.

The mechanical dimensions of a class a reference device at different power levels, different ground clearance types are as follows:

as can be seen from the core content of the national standard GB/T38775. X Wireless charging System for electric vehicles, the ground equipment of the wireless charging system of the electric automobile can adopt three-level power conversion. The first stage is PFC conversion, namely high power factor AC-DC; the second stage is DC-DC conversion; the third stage is DC-AC conversion, recommended to be operated at a fixed frequency, and nominal frequency f ₀ = (85.5 ± 0.05) kHz. Wherein the DC-DC conversion of the second stage is optional.

If the input voltage U is to be adapted _dc = 300-840V, there are two methods at present, the first method is to add the second DC-DC conversion, generally adopting Buck topology; the PFC conversion of the first stage adopts a Boot topology. The second method is to remove the second stage of DC-DC conversion, and the first stage of PFC conversion adopts Buck-Boot topology. The disadvantages of both methods are the complexity, cost and efficiency of the control, which is due to the input voltage U _dc The range is wide.

A second disadvantage of a wide input voltage range is that the input voltage U is higher if the coupling coefficient k is higher _dc Lower, resulting in a smaller current in the primary coil and a larger current in the secondary coil; secondary winding in extreme case I _s-max The current is likely to be overrun. In addition, the vehicle-mounted secondary coil is small and not beneficial to heat dissipation, and the current is large; the primary coil on the ground is large, heat dissipation is facilitated, and the current is small. This is not reasonable and is not safe.

A third disadvantage of a wide input voltage range is that the required output power is low if the coupling coefficient k is high, such as ground equipment and ground equipment with high power levelsWhen the vehicle-mounted equipment with low power level is matched, the input voltage U can be caused _dc And the voltage drops below the minimum voltage of 300V. This is also not suitable.

So that the input voltage U _dc The range of = 300-840V is very wide because the compensation topology and the electrical architecture of the MF-WPT system recommended by the national standard operate in a constant-frequency mode, and the output current of the MF-WPT system is in direct proportion to the coupling coefficient k. The overall range of coupling coefficients is k = 0.100-0.279, with 0.100/0.279 ≈ 300/840.

The mechanical dimensions of the onboard reference devices of different power classes, the self-inductance of the secondary coil, are identical in the types of ground clearance Z3 and Z2, but not identical in the type of ground clearance Z1. This causes inconvenience in standardized design and manufacture of the in-vehicle equipment, and increases the range of variation in the self-inductance of the primary coil in the aligned state.

SUMMERY OF THE UTILITY MODEL

The utility model aims at overcoming the not enough of prior art, provide a constant current mode wireless charging system of unsteady flow rectification and design and control method thereof. The secondary side compensation network adopts a three-gain or double-gain CCL topology, the rectifier adopts a current-converting rectification topology, an optimization design method is provided to determine the optimal system parameters and the secondary side magnetic core size, and a multi-stage current-converting rectification control method based on coupling coefficient interval switching is provided. Narrowing the voltage range of the direct current bus and reserving allowance for lifting power; the current of the primary side coil/the secondary side coil is optimally distributed, and the heat dissipation effect is improved. The method is beneficial to the adoption of Boot topology for the first-stage PFC conversion and the removal of the second-stage DC-DC conversion; the self-inductance of the primary/secondary side coil and the size of each type of ground clearance of vehicle-mounted equipment are unified. The MF-WPT system recommended by the national standard is compatible in the national standard framework to accelerate standardization, popularization and application.

The technical scheme of the utility model as follows.

A constant current mode wireless charging system with variable current and rectification comprises a primary side part and a secondary side part; the primary side part comprises an AC-DC conversion circuit (1), a DC-AC converter (2), a primary side compensation network (3) and a primary side coil Lp, and the secondary side part comprises a secondary side coil Ls, a secondary side compensation network (4), a variable current rectifier (5) and a filter circuit (6). The AC-DC conversion circuit (1) comprises an APFC unit, realizes high power factor and regulates the output direct-current voltage; the DC-AC converter (2) adopts a full-bridge topology; the primary side compensation network (3) adopts an LCC topology and comprises capacitors Cp and Cr and an inductor Lr. Wherein the content of the first and second substances,

the secondary side compensation network (4) adopts a three-gain CCL topology or a double-gain CCL topology; the three-gain CCL topology comprises capacitors Cs, C1, C2 and C3 and inductors L1, L2 and L3, and the double-gain CCL topology comprises capacitors Cs, C1 and C2 and inductors L1 and L2.

The converter rectifier (5) adopts a three-order converter topology or a second-order converter topology, and respectively corresponds to a three-gain CCL topology or a double-gain CCL topology of the secondary side compensation network (4); the three-order current transformation topology comprises two types, namely a three-bridge arm two-switch topology and a two-bridge arm three-switch topology; two kinds of second-order variable current topologies exist, namely a three-bridge arm one-switch topology and a two-bridge arm two-switch topology. The three-bridge arm two-switch topology comprises diodes D1, D2, D3, D4, D5 and D6 and switches S1 and S2, and the two-bridge arm three-switch topology comprises diodes D1, D2, D3 and D4 and switches S1, S2 and S3; and removing the switch S2 from the three-bridge arm two-switch topology to form a three-bridge arm one-switch topology, and removing the switch S3 from the two-bridge arm three-switch topology to form a two-bridge arm two-switch topology. The switches S1, S2 and S3 are electronic switches or contactor switches.

The connection relation between the secondary side compensation network (4) and the converter rectifier (5) is that the three-gain CCL topology is correspondingly connected with a third-order converter topology, and the double-gain CCL topology is correspondingly connected with a second-order converter topology.

When the secondary side compensation network (4) adopts a three-gain CCL topology and the converter rectifier (5) adopts a three-order converter topology: a first end of a secondary coil Ls is connected with a first end of a capacitor Cs, a second end of the capacitor Cs is connected with a first end of a capacitor C2 and a first end of an inductor L2, and a second end of the inductor L2 is used as a node V2; the second end of the capacitor C2 is used as a node V3; the second end of the secondary coil Ls is connected with the second end of the capacitor C1 and the first end of the inductor L1, and the second end of the inductor L1 is used as a node V1; the first end of the capacitor C1 is connected with the second end of the capacitor C3 and the first end of the inductor L3, the first end of the capacitor C3 is connected with the node V3, and the second end of the inductor L3 is used as a node V4. If the converter rectifier (5) adopts a three-bridge arm two-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, and the anode of the diode D5 and the cathode of the diode D6 are connected with the node V3; the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1 and S2, the other end of the S1 is connected with a node V1, and the other end of the S2 is connected with a node V4; the cathodes of the diodes D1, D3, D5 are connected together as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2, D4, D6 are connected together as the ground GND of the converter rectifier (5). If the converter rectifier (5) adopts a two-bridge arm three-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1, S2 and S3, the other end of the diode S1 is connected with the node V1, the other end of the diode S2 is connected with the node V4, and the other end of the diode S3 is connected with the node V3. The cathodes of the diodes D1 and D3 are connected together to be used as the positive end Vd of the converter rectifier (5), and the anodes of the diodes D2 and D4 are connected together to be used as the ground end GND of the converter rectifier (5).

When the secondary side compensation network (4) adopts a double-gain CCL topology and the converter rectifier (5) adopts a second-order converter topology: a first end of a secondary coil Ls is connected with a first end of a capacitor Cs, a second end of the capacitor Cs is connected with a first end of a capacitor C2 and a first end of an inductor L2, and a second end of the inductor L2 is used as a node V2; the second end of the capacitor C2 is used as a node V3; the second end of the secondary coil Ls is connected with the second end of the capacitor C1 and the first end of the inductor L1, the first end of the capacitor C1 is connected with a node V3, and the second end of the inductor L1 is used as a node V1. If the converter rectifier (5) adopts a three-bridge arm one-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, and the anode of the diode D5 and the cathode of the diode D6 are connected with the node V3; the anode of the diode D1 and the cathode of the diode D2 are connected with one end of the switch S1, and the other end of the switch S1 is connected with the node V1; the cathodes of the diodes D1, D3, D5 are connected together as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2, D4, D6 are connected together as the ground GND of the converter rectifier (5). If the converter rectifier (5) adopts a two-bridge arm two-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1 and S2, the other end of the diode S1 is connected with the node V1, and the other end of the diode S2 is connected with the node V3. The cathodes of the diodes D1 and D3 are connected together to serve as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2 and D4 are connected together to serve as the ground terminal GND of the converter rectifier (5).

If bidirectional electric energy transmission or synchronous rectification is needed, the diodes D1, D2, D3, D4, D5 and D6 are respectively replaced by the switching tubes Q1, Q2, Q3, Q4, Q5 and Q6, the switching tubes adopt MOSFETs or IGBTs, the source electrodes and the drain electrodes of the switching tubes respectively correspond to the anodes and the cathodes of the diodes, and the connection relationship is kept unchanged.

The positive end Vd and the ground end GND of the variable current rectifier (5) are connected with an equivalent load Ro through a filter circuit (6). The AC power source Uac is connected with an AC-DC conversion circuit (1).

The design method of the constant-current mode wireless charging system with variable-current rectification is as follows.

Description of the drawings: the design method is suitable for three types of ground clearance Z1, Z2 and Z3 specified by the national standard and three power levels MF-WPT1, MF-WPT2 and MF-WPT3, and can be popularized to a wireless charging system with a higher power level.

Defining: q _p ＝U _p I _p Is the volt-ampere value of the primary coil, U _p ＝ω ₀ L _p I _p Is the effective voltage value of the primary coil; q _s ＝U _s I _s Is the volt-ampere value of the secondary coil, U _s ＝ω ₀ L _s I _s The effective value of the voltage of the secondary side coil; wherein ω is ₀ ＝2πf ₀ ，f ₀ The nominal frequency of the MF-WPT system. The relation between the transmission power of the MF-WPT system in the constant current mode and the volt-ampere value of the coil is as follows:

wherein, P is transmission power, k is coupling coefficient, and M is mutual inductance. L is _p Is the self-inductance of the primary coil, L _s The self-inductance of the secondary coil is obtained; i is _p Is the effective value of the current of the primary coil, I _s The effective value of the current of the secondary coil is obtained.

Design principles of a primary coil Lp and a secondary coil Ls:

1) And relatively equalizing volt-ampere values of the primary coil and the secondary coil to define a volt-ampere equalizing coefficient B.

Q _{sM_h-3} ＝B·Q _pM ,B＝1.25～1.65 (E-02)

2) For three types of ground clearance and three power levels, the primary coil adopts the same self-inductance; according to the three types of ground clearance regardless of the power grade, the secondary side coil adopts three different self-inductance quantities, or the secondary side coil adopts the same self-inductance regardless of ground clearance and power level. Setting the relation between the self-inductance of the secondary coil and the coupling coefficient:

or L _{s_h} ＝L _{s_3} (E-03)

In the formulae (E-01) to (E-03), P _M-n Maximum power for nth power class (same for three types of ground clearance); k is a radical of _{m_h} Is Z _h Minimum coupling coefficient of ground clearance (same for three power levels), k _{m_3} Minimum coupling coefficient for Z3 ground clearance;

is the maximum volt-ampere value of the primary coil, I _pM Is the maximum effective current value, L, of the primary coil _p Is the self inductance of the primary coil;

and

respectively secondary side coil at Z _h Maximum volt-ampere values of the nth power level and the 3 rd power level of the ground clearance; i is _{sM_h-n} And I _{sM_h-3} Respectively secondary side coil at Z _h The maximum current effective value of the nth power class and the 3 rd power class of the ground clearance; l is _{s_h} And L _{s_3} Are respectively asZ _h And the secondary coil self-inductance of the ground clearance and the Z3 ground clearance. n =1,2,3 represents a power level; h =1,2,3 represents a ground clearance type; eta is the efficiency of the MF-WPT system except for the coupling coil, and generally requires eta to be more than 0.9.

Design principle of primary side compensation network (3): the primary compensation network (3) uses the same parameter L _r ,C _r ,C _p ]。

The design principle of the secondary side compensation network (4) is as follows: determining different parameters [ C ] according to different ground clearance and power grade _{s_h-n} ,C _{1_h-n} ,C _{2_h-n} ,C _{3_h-n} ,L _{1_h-n} ,L _{2_h-n} ,L _{3_h-n} ]。

Based on the design principle, according to the topological characteristics of the compensation network, a primary coil Lp, a secondary coil Ls, a primary compensation network (3) and a secondary compensation network (4) are provided, and a parameter design formula for realizing variable current rectification in a constant current mode is provided. When the secondary windings adopt the same self-inductance, k is used in the formulae (E-04) and (E-05) _{m_3} Replacement of k _{m_h} 。

C _{s_h-n} ,C _{1_h-n} ,C _{2_h-n} ,C _{3_h-n} ,L _{1_h-n} ,L _{2_h-n} ,L _{3_h-n} Are respectively C _s ,C ₁ ,C ₂ ,C ₃ ,L ₁ ,L ₂ ,L ₃ At Z _h A parameter value of an nth power level of ground clearance;

is an intermediate variable. I.C. A _oM-n The maximum value of the output current of the variable current rectifier (5) at the nth power level; u shape _dc-M Is the maximum value of the DC bus voltage of the DC-AC converter (2), namely the output voltage U of the AC-DC conversion circuit (1) _dc Is measured. k is a radical of _{M_h} Is Z _h Maximum coupling coefficient of ground clearance (same for three power levels). g is the gain order, the triple-gain CCL topology g =3, the double-gain CCL topology g =2. q. q.s _h Referred to as the common ratio; when g =3, if 1.385 ≦ q _h If the ratio is less than or equal to 1.445, taking

To let L _{1_h-n} ＝L _{2_h-n} 。

The dual-gain CCL topology can be seen as a reduction of the triple-gain CCL topology, i.e. L when g =2 _{3_h-n} ＝0、C _{3_h-n} And = ∞ and thus gets rid of.

Description of the drawings: self-inductance L given by formula (E-05) _p And L _{s_h} Is at Z _h The value at which the minimum coupling coefficient of the ground clearance is obtained. This is because the primary winding and the secondary winding are paired and their self-inductance varies with the difference in ground clearance and alignment offset. The amount of self-inductance should be reduced (experimentally set) when the primary and secondary coils are independent of each other.

The mechanical size of the magnetic core matched with the secondary windings of the three types of ground clearances Z1, Z2 and Z3 is adjusted and determined according to the following method: in the range of each type of ground clearance and the offset range of X, Y direction thereof, when the coupling coefficient of the secondary coil and the primary coil is minimum, the mechanical dimension of the magnetic core of the type of ground clearance is determined, so that the self-inductance L of the primary coil of the standard reference equipment is enabled to be L _p Meeting the design value calculated by the formula (E-05); and coupling in three types of ground clearanceWhen the coefficient is maximum, the difference between the maximum values of the self-inductance of the primary coil is minimized.

The control method of the constant-current mode wireless charging system with variable-current rectification is as follows.

The minimum value k of the coupling coefficients of Z1, Z2 and Z3 to the ground clearance is confirmed according to the regulation of the national standard GB/T38775.6-2021 part 6 of the wireless charging system for electric vehicles _{m_h} And maximum value k _{M_h} . And providing a variable flow rectification control flow based on a constant frequency and constant current mode according to the parameter design of the secondary side compensation network (4), the topological structure of the variable flow rectifier (5) and the variation range of the coupling coefficient.

In a first step, the coupling coefficients are partitioned into regions.

When the secondary side compensation network (4) adopts a three-gain CCL topology, the coupling coefficient is divided into three intervals: [ k ] A _{m_h} ,k _{1_h} )、[k _{1_h} ,k _{2_h} )、[k _{2_h} ,k _{M_h} ]Wherein k is _{1_h} And k _{2_h} Is Z _h Two boundary values of the coupling coefficient of the ground clearance. Setting k _{m_h} ,k _{1_h} ,k _{2_h} Is given a common ratio of q _h Is compared with the prior art, and the geometric series of (c),

when the secondary side compensation network (4) adopts a double-gain CCL topology, the coupling coefficient is divided into two intervals: [ k ] A _{m_h} ,k _{a_h} )、[k _{a_h} ,k _{M_h} ]Wherein k is _{a_h} Is Z _h The boundary value of the coupling coefficient of the ground clearance. Setting k _{m_h} ,k _{a_h} ,k _{M_h} Is given a common ratio of q _h Is compared with the prior art, and the geometric series of (c),

secondly, after the secondary coil and the primary coil are aligned, the detected mutual inductance M is detected _e Conversion to the actual coupling factor k _e 。

Thirdly, judging the coupling coefficient k according to the topology adopted by the secondary side compensation network (4) _e To which it belongsAn interval.

And fourthly, controlling the on-off state of switches S1, S2 and S3 in the variable current rectifier (5).

For a three-arm two-switch topology with three-order current transformation:

when k is _e ∈[k _{m_h} ,k _{1_h} ) When the circuit is started, the switches S1 and S2 are both turned off;

when k is _e ∈[k _{1_h} ,k _{2_h} ) When the switch S1 is turned off, the switch S2 is turned on;

when k is _e ∈[k _{2_h} ,k _{M_h} ]When the switch S2 is turned off, the switch S1 is turned on.

For a two leg three switch topology for three order current conversion:

when k is _e ∈[k _{m_h} ,k _{1_h} ) When the circuit is started, the switches S1 and S2 are turned off, and the switch S3 is turned on;

when k is _e ∈[k _{1_h} ,k _{2_h} ) When the circuit is started, the switches S1 and S3 are turned off, and the switch S2 is turned on;

when k is _e ∈[k _{2_h} ,k _{M_h} ]When the switch is turned off, the switches S2 and S3 are turned off, and the switch S1 is turned on.

For a three-arm one-switch topology with second order conversion:

when k is _e ∈[k _{m_h} ,k _{a_h} ) When the switch S1 is turned off, the switch S1 is turned off;

when k is _e ∈[k _{a_h} ,k _{M_h} ]At this time, the switch S1 is turned on.

For a two leg two switch topology with second order conversion:

when k is _e ∈[k _{m_h} ,k _{a_h} ) When the switch S1 is turned off, the switch S2 is turned on;

when k is _e ∈[k _{a_h} ,k _{M_h} ]When the switch S2 is turned off, the switch S1 is turned on.

Therefore, three-order or two-order variable current rectification can be realized, and the multiple of variable current is q in common ratio _h An equal ratio series of (c).

A fifth step of starting the DC-AC converter (2) at the nominal frequency f ₀ Operation at constant frequency of =85.5kHz while adjusting output voltage U of AC-DC conversion circuit (1) _dc To constant or regulated deliveryAnd (6) discharging current.

U _dc Namely the direct current bus voltage of the DC-AC converter (2). If the design and control method are as above, then U _dc Is substantially determined as U _dc Voltage span of = 760V-535V

Because the output current is equal to U _dc In proportion, based on the voltage data 840/760 ≈ 1.1 and 400/535 ≈ 0.75, the output current still has 10% of up-regulation margin under the condition of the minimum coupling coefficient, and has 25% of down-regulation margin under the condition of the maximum coupling coefficient. Therefore in U _dc Under the condition of not less than 400V, the AC-DC conversion circuit (1) with single-phase alternating current power input can adopt Boost type single-stage PFC conversion, thereby simplifying control, improving efficiency and reducing cost.

Because of the DC bus voltage U _dc =760V to 535V, the primary coil current I _p ≈(1～0.7)I _pM . Because of the three-order constant ratio variable current rectification, the current I of the secondary coil _s-n ≤(1,0.7,0.5)I _sM-n . From this, it can be seen that the secondary coil current is greater than the primary coil current only when the output power is greater than 9.9kW (9.9 =11.1 × 58/65) and k < 0.158 (0.158 =0.141 × 65/58); in any other case, the secondary winding current is less than the primary winding current.

Compared with the prior art, the utility model has the following advantages.

1) The utility model can narrow the voltage range of the direct current bus and reserve margin for improving or reducing the output power;

2) The utility model is beneficial to adopting a Boot type single-stage PFC converter to remove the DC-DC conversion of the second stage;

3) The utility model is beneficial to reducing the current of the secondary side coil and properly increasing the current of the primary side coil, and improving the heat dissipation of the secondary side;

4) The utility model is beneficial to unifying the self-inductance of the primary/secondary coil and the size of the secondary magnetic core under each type of ground clearance;

5) The utility model discloses within the national standard frame, the circuit topology and the constant current mode of deciding the frequency of the MF-WPT system that compatible national standard recommends provide the optimal design and retrench the control scheme, strengthened the basis for MF-WPT system standardization and popularization and application.

Drawings

Fig. 1 is a schematic block diagram of the first embodiment of the variable-current rectification constant-current mode wireless charging system.

In the first embodiment, the secondary side compensation network (4) adopts a three-gain CCL topology, and the variable current rectifier (5) adopts a three-bridge arm two-switch (three-order variable current) topology.

Fig. 2 is a schematic block diagram of a second embodiment of the variable-current rectification constant-current mode wireless charging system.

In a second embodiment, the secondary side compensation network (4) adopts a double-gain CCL topology, and the converter rectifier (5) adopts a three-bridge-arm one-switch (second-order converter) topology.

Fig. 3 is a schematic block diagram of a third embodiment of the variable-current rectified constant-current mode wireless charging system.

In the third embodiment, the diodes D1, D2, D3, D4, D5, D6 in the second embodiment are replaced by switching tubes Q1, Q2, Q3, Q4, Q5, Q6, respectively, and the rest is the same as the second embodiment.

Fig. 4 is a schematic block diagram of a fourth embodiment of the variable-current rectified constant-current mode wireless charging system.

In the fourth embodiment, the secondary side compensation network (4) adopts a three-gain CCL topology, and the variable current rectifier (5) adopts a two-bridge arm three-switch (three-order variable current) topology.

Fig. 5 is a schematic block diagram of a fifth embodiment of the variable-current rectified constant-current mode wireless charging system.

In a fifth embodiment, the secondary compensation network (4) adopts a dual-gain CCL topology, and the converter rectifier (5) adopts a two-bridge-arm two-switch (second-order converter) topology.

Fig. 6 is a schematic block diagram of a sixth embodiment of the variable-current rectified constant-current mode wireless charging system.

In the sixth embodiment, the diodes D1, D2, D3, D4 in the fifth embodiment are replaced with switching tubes Q1, Q2, Q3, Q4, respectively, and the other portions are the same as the fifth embodiment.

FIG. 7 is a schematic block diagram of the electrical architecture of a MF-WPT system composed of class A reference devices recommended by the national standard.

Fig. 8 is a mutual inductance model diagram of the primary coil and the secondary coil being coupled to each other.

FIG. 9 is an equivalent model diagram of a controlled source with a primary coil and a secondary coil coupled to each other.

Fig. 10 is a circuit schematic of a T-network.

Fig. 11 is an equivalent circuit model diagram of the primary side compensation network accessing the primary side coil.

FIG. 12 is an equivalent circuit model diagram of a secondary winding connected to a three-gain CCL compensation network.

Fig. 13 is an equivalent circuit model diagram of a secondary winding connected to a dual-gain CCL compensation network.

Reference numbers in the drawings: 1-AC-DC conversion circuit, 2-DC-AC converter, 3-primary side compensation network, 4-secondary side compensation network, 5-converter rectifier, 6-filter circuit; lp-primary coil, ls-secondary coil. Cp, cr, cs, C1, C2, C3-capacitance, lr, L1, L2, L3-inductance; s1, S2 and S3-switches, D1, D2, D3, D4, D5 and D6-diodes, and Q1, Q2, Q3, Q4, Q5 and Q6-switching tubes. Uac-alternating current power supply, ro-equivalent load.

Detailed Description

The present invention will be described and analyzed in detail with reference to the preferred embodiments thereof, which are illustrated in the accompanying drawings. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of them.

To put it another way, references to "first", "second", etc. in this disclosure are for indicative purposes only and are not to be construed as indicating their relative importance or implicitly indicating the number of technical features.

1. Preferred embodiments of the present invention

As shown in fig. 1 to 6, a current-variable rectification constant-current mode wireless charging system and a design and control method thereof, wherein the wireless charging system comprises a primary side part and a secondary side part; the primary side part comprises an AC-DC conversion circuit (1), a DC-AC converter (2), a primary side compensation network (3) and a primary side coil Lp, and the secondary side part comprises a secondary side coil Ls, a secondary side compensation network (4), a variable current rectifier (5) and a filter circuit (6). The AC-DC conversion circuit (1) comprises an APFC unit, realizes high power factor and regulates the output direct-current voltage; the DC-AC converter (2) adopts a full-bridge topology; the primary side compensation network (3) is of an LCC topology and comprises capacitors Cp and Cr and an inductor Lr.

The converter rectifier (5) adopts a three-order converter topology or a second-order converter topology, and respectively corresponds to a three-gain CCL topology or a double-gain CCL topology of the secondary side compensation network (4); the three-order variable current topology comprises two topologies, namely a three-bridge arm two-switch topology and a two-bridge arm three-switch topology; two kinds of second-order variable current topologies exist, namely a three-bridge arm one-switch topology and a two-bridge arm two-switch topology. The three-bridge arm two-switch topology comprises diodes D1, D2, D3, D4, D5 and D6 and switches S1 and S2, and the two-bridge arm three-switch topology comprises diodes D1, D2, D3 and D4 and switches S1, S2 and S3; and removing the switch S2 from the three-bridge arm two-switch topology to form a three-bridge arm one-switch topology, and removing the switch S3 from the two-bridge arm three-switch topology to form a two-bridge arm two-switch topology. The switches S1, S2 and S3 are electronic switches or contactor switches.

As shown in fig. 1 and 2, the secondary compensation network (4) adopts a three-gain CCL topology, and the converter rectifier (5) adopts a third-order converter topology. A first end of a secondary coil Ls is connected with a first end of a capacitor Cs, a second end of the capacitor Cs is connected with a first end of a capacitor C2 and a first end of an inductor L2, and a second end of the inductor L2 is used as a node V2; the second end of the capacitor C2 is used as a node V3; the second end of the secondary coil Ls is connected with the second end of the capacitor C1 and the first end of the inductor L1, and the second end of the inductor L1 is used as a node V1; the first end of the capacitor C1 is connected with the second end of the capacitor C3 and the first end of the inductor L3, the first end of the capacitor C3 is connected with the node V3, and the second end of the inductor L3 is used as a node V4. If the converter rectifier (5) adopts a three-bridge arm two-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, and the anode of the diode D5 and the cathode of the diode D6 are connected with the node V3; the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1 and S2, the other end of the S1 is connected with a node V1, and the other end of the S2 is connected with a node V4; the cathodes of the diodes D1, D3, D5 are connected together as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2, D4, D6 are connected together as the ground GND of the converter rectifier (5). If the converter rectifier (5) adopts a two-bridge arm three-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1, S2 and S3, the other end of the diode S1 is connected with the node V1, the other end of the diode S2 is connected with the node V4, and the other end of the diode S3 is connected with the node V3. The cathodes of the diodes D1 and D3 are connected together to serve as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2 and D4 are connected together to serve as the ground terminal GND of the converter rectifier (5).

As shown in fig. 4 and 5, the secondary side compensation network (4) is a dual-gain CCL topology, and the converter rectifier (5) is a second-order converter topology. A first end of a secondary coil Ls is connected with a first end of a capacitor Cs, a second end of the capacitor Cs is connected with a first end of a capacitor C2 and a first end of an inductor L2, and a second end of the inductor L2 is used as a node V2; the second end of the capacitor C2 is used as a node V3; the second end of the secondary coil Ls is connected with the second end of the capacitor C1 and the first end of the inductor L1, the first end of the capacitor C1 is connected with a node V3, and the second end of the inductor L1 is used as a node V1. If the converter rectifier (5) is a three-bridge-arm one-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, and the anode of the diode D5 and the cathode of the diode D6 are connected with the node V3; the anode of the diode D1 and the cathode of the diode D2 are connected with one end of the switch S1, and the other end of the switch S1 is connected with a node V1; the cathodes of the diodes D1, D3, D5 are connected together as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2, D4, D6 are connected together as the ground GND of the converter rectifier (5). If the converter rectifier (5) is a two-bridge arm two-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1 and S2, the other end of the diode S1 is connected with the node V1, and the other end of the diode S2 is connected with the node V3. The cathodes of the diodes D1 and D3 are connected together to serve as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2 and D4 are connected together to serve as the ground terminal GND of the converter rectifier (5).

If bidirectional electric energy transmission or synchronous rectification is needed, the diodes D1, D2, D3, D4, D5 and D6 are respectively replaced by the switching tubes Q1, Q2, Q3, Q4, Q5 and Q6, the switching tubes adopt MOSFETs or IGBTs, the source electrodes and the drain electrodes of the switching tubes respectively correspond to the anodes and the cathodes of the diodes, and the connection relation is unchanged. As shown in fig. 3 and 6.

2. The working principle of the utility model

The working principle of the variable-current rectification constant-current mode wireless charging system is characterized in that the content is analyzed in detail in three sections.

2.1 mutual inductance model and controlled source equivalent model of coupling coil

The primary coil and the secondary coil of the wireless charging system in the constant current mode of current transformation and rectification are coupled with each other, and the mutual inductance model is shown in fig. 8. According to the circuit theory, a frequency domain equation set is obtained as follows.

In the formula (E-1), L _p Is self-inductance of the primary coil, L _s The self inductance of the secondary coil is obtained, and M is the mutual inductance of the coupling coil. Omega is AC power supply U ₁ The angular frequency of (c).

A controlled source equivalent model of the coupling coil can be built from the frequency domain equation set as shown in fig. 9.

Defining a coupling coefficient k:

2.2T-type network and circuit characteristics thereof

A T-network is a circuit consisting of an inductor and a capacitor, as shown in fig. 10, which is commonly used in resonant converters.

The input is a sine voltage source, and the effective values of the input voltage and the input current are respectively U _in And I _in The effective values of the output voltage and the current are respectively U _o And I _o Then, from KVL and ohm's law:

in the formula (E-3), G _I Is a current transfer function equal to the ratio of the output current to the input voltage; z _in Is an input impedance equal to the ratio of the input voltage to the input current; r is _L Is an equivalent load.

If a constant current mode, i.e. constant current output in the full load range, is to be realized, the current transfer function G _I With equivalent load R _L Irrelevant; and simultaneously, the input reactive power is zero, namely the input impedance angle is zero. Then the following constraints are required:

at this time, the current transfer function G _I And an input impedance Z _in Respectively as follows:

constant current output condition and Z ₃ Not related, but Z ₃ But affects the input impedance angle. Do not provide: z ₁ And Z ₃ Being inductive, Z ₂ Is capacitive; or Z ₁ And Z ₃ Is capacitive, Z ₂ Is inductive. Then the constraint is materialized as:

or

2.3 basic conditions for constant current mode and variable current rectification

The T-type network is introduced into the compensation network design of the MF-WPT system, and the analysis is carried out from the angle of fixed frequency.

A T-type network is introduced into the primary side of the coupling coil controlled source equivalent model to obtain an equivalent circuit model of the primary side compensation network accessing the primary side coil, as shown in fig. 11. The primary side compensation network adopts an LCC topology, and is obtained according to the formula (E-6):

and introducing a T-shaped network into a secondary side of the coupling coil controlled source equivalent model to obtain an equivalent circuit model with a secondary side coil connected with a three-gain CCL compensation network and a two-gain CCL compensation network, as shown in FIGS. 12 and 13.

Defining a common ratio q E (1,2), and when the secondary side compensation network is a three-gain CCL topology, obtaining the following formula (E-6):

for a dual-gain CCL topology, it can be seen as a reduction of the triple-gain CCL topology, i.e., L in equation (E-8) ₃ ＝0、C ₃ And = ∞ and thus gets rid of. The relation is simplified as follows:

the formula (E-7), the formula (E-8) and the formula (E-9) are basic conditions for operating the MF-WPT system in a constant current mode and realizing variable current rectification. As shown in fig. 1, when the variable current rectifier (5) is input at nodes V1 and V2 or at nodes V2 and V4 or at nodes V2 and V3, the MF-WPT system operates in a constant current mode, and the output current of the variable current rectifier (5) is proportional to the common ratio q. On the basis, as can be known from the controlled source equivalent model, the transmission power P of the coupling coil is:

as can be seen from the formula (E-10), the maximum transmission capability of the coupling coil is defined by the angular frequency omega and the primary current effective value I _p Secondary side current effective value I _s Primary coil self-inductance L _p Secondary winding self-inductance L _s And the coupling coefficient k.

The controlled source equivalent model and the formulas (E-5) and (E-2) are obtained:

wherein, I _e Is the effective value of the rectifier input current, i.e. the effective value of the current flowing from nodes Va and Vc; i is _o The rectifier output current (average value). Effective value of sine alternating current I _e With the average value I _o The relationship of (c) is derived from integration.

The DC bus voltage of the DC-AC converter (2) is set to be U _dc And neglecting the conduction voltage drop of a switch tube in the DC-AC converter (2). According to Fourier series analysis, the fundamental effective value U of the output voltage of the DC-AC converter (2) _in Comprises the following steps:

according to the formulae (E-12) and (E-5):

3. the design method of the utility model

Defining: volt-ampere value Q of primary coil _p ＝U _p I _p Effective value of voltage U of primary winding _p ＝ω ₀ L _p I _p (ii) a Volt-ampere value Q of secondary coil _s ＝U _s I _s Effective value of voltage U of secondary winding _s ＝ω ₀ L _s I _s . Wherein omega ₀ ＝2πf ₀ ，f ₀ The nominal frequency of the MF-WPT system. Derived from the formula (E-10):

wherein, P _M-n Maximum power for the nth power class (same for three types of ground clearance), k _{m_h} Is Z _h Minimum coupling coefficient of ground clearance (same for three power levels);

is the maximum volt-ampere value of the primary coil, I _pM The maximum current effective value of the primary coil;

for the secondary coil at Z _h Maximum volt-ampere value of the nth power level of the ground clearance, I _{sM_h-n} For the secondary coil at Z _h The ground clearance nth power level maximum current effective value. n =1,2,3 represents a power class; h =1,2,3 represents a ground clearance type. Eta is the efficiency of the MF-WPT system (except for the coupling coil), and generally requires eta > 0.9.

Aiming at three types of ground clearance Z1, Z2 and Z3 and three power levels MF-WPT1, MF-WPT2 and MF-WPT3, a method for designing a primary coil Lp, a secondary coil Ls, a primary compensation network (3) and a secondary compensation network (4) is provided.

3.1 design of Primary coil Lp and Secondary coil Ls

Firstly, the design principles of a primary coil Lp and a secondary coil Ls are determined, and the number of the primary coil Lp and the secondary coil Ls is two.

1) And relatively balancing volt-ampere values of the primary coil and the secondary coil. Defining a voltammetry equalization coefficient B, and setting:

Q _sM-3-h ＝B·Q _pM ,B＝1.25～1.65 (E-15)

2) For three types of ground clearance and three power levels, the primary coil adopts the same self-inductance; the secondary side coil adopts three different self-inductance quantities according to three types of ground clearance regardless of power level, or adopts the same self-inductance quantity regardless of the ground clearance and the power level. Setting the relation between the self-inductance and the coupling coefficient of the secondary coil:

according to said principle, it follows from the formulae (E-14), (E-15) and (E-16):

wherein L is _{s_h} Is Z _h The self-inductance of the secondary coil of the ground clearance; l is _p Is the self-inductance of the primary coil; I.C. A _{sM_3-3} The maximum effective value of current, P, of the 3 rd power class of the secondary coil at Z3 ground clearance _M-3 Maximum power at 3 rd power level (same for three types of ground clearance), k _{m_3} The minimum coupling coefficient for the gap Z3 from the ground (same for three power levels). When the secondary windings adopt the same self-inductance, k is used in the formulas (E-17) and (E-18) _{m_3} Replacement of k _{m_h} 。

The self-inductance of the primary coil and the secondary coil changes with the difference of ground clearance and alignment offset when the ground equipment and the vehicle-mounted equipment are paired. Thus, the self-inductance given by formula (E-18) is in Z _h The value at which the minimum coupling coefficient of the ground clearance is obtained. The amount of self-inductance should be reduced (experimentally set) when the primary and secondary coils are independent.

3.2 design of Primary Compensation network (3)

The primary compensation network (3) uses the same parameter L _r ,C _r ,C _p ]。

The inductance L can be determined from the formula (E-13) _r The value of (c).

Wherein, U _dc-M Is the maximum value of the DC bus voltage of the DC-AC converter (2), namely the output voltage U of the AC-DC conversion circuit (1) _dc Is measured.

Substituting the formula (E-19) into (E-7) to derive:

3.3 design of the Secondary Compensation network (4)

For Z2 and Z3 ground clearance, the secondary side compensation network (4) adopts a three-gain CCL topology, and for Z1 ground clearance, the secondary side compensation network (4) adopts a double-gain CCL topology or a three-gain CCL topology.

The secondary side compensation network (4) determines a specific parameter [ C ] according to different ground clearance types and power levels _{s_h-n} ,C _{1_h-n} ,C _{2_h-n} ,C _{3_h-n} ,L _{1_h-n} ,L _{2_h-n} ,L _{3_h-n} ]Are respectively [ C _s ,C ₁ ,C ₂ ,C ₃ ,L ₁ ,L ₂ ,L ₃ ]At Z _h A parameter value for the nth power level of the ground clearance. In which intermediate variables are introduced

Derived from the formula (E-11), the formula (E-17) and the formula (E-18):

a unified analytical formula of the secondary side compensation network parameters can be deduced from the formula (E-21), the formula (E-8) and the formula (E-9):

in the formulae (E-21) to (E-22), I _eM-n Is the maximum effective value, I, of the input current of the variable current rectifier (5) at the nth power level _oM-n The output current of the variable current rectifier (5) is at the maximum value of the nth power level,

k _{M_h} is Z _h Maximum coupling coefficient of ground clearance (same for three power levels). g is the gain order, the triple-gain CCL topology g =3, the double-gain CCL topology g =2. q. q of _h Referred to as the common ratio; when g =3, if 1.385 ≦ q _h When the concentration is less than or equal to 1.445, the extract is taken

So that L _{1_h-n} ＝L _{2_h-n} 。

As can be seen by equation (E-22), the dual-gain CCL topology can be viewed as a reduced order of the triple-gain CCL topology. I.e., g =2, L _{3_h-n} ＝0,C _{3_h-n} And = ∞ and thus gets rid of.

3.4 mechanical dimensions of the secondary winding adapted to the magnetic core

The mechanical size of the magnetic core matched with the secondary windings of the three types of ground clearances Z1, Z2 and Z3 is adjusted and determined according to the following method: in the range of each type of ground clearance and the offset range of X, Y direction thereof, when the coupling coefficient of the secondary coil and the primary coil is minimum, the mechanical dimension of the magnetic core of the type of ground clearance is determined, so that the self-inductance L of the primary coil of the standard reference equipment is enabled to be L _p In accordance with the calculated design value of the formula (E-18); and when the coupling coefficients of the three types of ground clearances are the maximum, the difference of the maximum value of the self-inductance of the primary coil is minimized.

3.5 optimal parameters of primary/secondary coil and compensation network thereof

Under the principle of being compatible with the national standard GB/T38775. X, the section provides a set of optimal parameters which are in a constant current mode and can realize variable current rectification according to the design method.

For Z2 and Z3 ground clearance, the secondary side compensation network (4) adopts a three-gain CCL topology; for the Z1 ground clearance, the secondary side compensation network (4) adopts a double-gain CCL topology; unity common ratio

According to the regulation of the national standard GB/T38775.6-2021 electric vehicle wireless charging system, f ₀ ＝85.5kHz，P _M-3 ＝11.1kW，P _M-2 ＝7.7kW，P _M-1 =3.7kW. Setting the highest charging voltage of the vehicle-mounted end to be 400V, the maximum output currents of the three power levels are respectively as follows: i is _oM-3 ＝27.75、I _oM-2 ＝19.25、I _oM-1 ＝9.25。

Let η =0.93, b =1.385 _pM ＝58A，U _dc-M ＝760V，I _{sM_3-3} And =60 to 61A. The optimal parameter values are calculated according to the equations (E-18) to (E-22), and are listed as follows.

4. The control method of the utility model

The control method of the wireless charging system in the constant current mode of variable current rectification is as follows.

The minimum value k of the coupling coefficients of the Z1, Z2 and Z3 ground clearance is confirmed according to the regulation of the national standard GB/T38775.6-2021 electric vehicle wireless charging system part 6 _{m_h} And maximum value k _{M_h} . And providing a variable current rectification control flow based on a constant frequency constant current mode according to the parameter design of the secondary side compensation network (4), the topological structure of the variable current rectifier (5) and the variation range of the coupling coefficient.

In a first step, the coupling coefficients are partitioned into regions.

Thirdly, judging the coupling coefficient k according to the topology adopted by the secondary side compensation network (4) _e The section to which it belongs.

And fourthly, controlling the on-off states of switches S1, S2 and S3 in the converter rectifier (5).

For a three-arm two-switch topology with three-order current transformation:

For a two leg three switch topology for three order current conversion:

For a three-arm one-switch topology with second order conversion:

when k is _e ∈[k _{a_h} ,k _{M_h} ]At this time, the switch S1 is turned on.

For a two leg two switch topology with second order conversion:

Therefore, three-order or two-order variable current rectification can be realized, and the multiple of the variable current is q in common ratio _h An equal ratio series of (c).

A fifth step of starting the DC-AC converter (2) at a nominal frequency f ₀ Operation at constant frequency of =85.5kHz while adjusting output voltage U of AC-DC conversion circuit (1) _dc To maintain constant or regulate the output current.

Because the output current is equal to U _dc In proportion, based on the voltage data 840/760 ≈ 1.1 and 400/535 ≈ 0.75, the output current still has 10% of up-regulation margin under the condition of the minimum coupling coefficient, and has 25% of down-regulation margin under the condition of the maximum coupling coefficient. So at U _dc Under the condition of not less than 400V, the AC-DC conversion circuit (1) of the single-phase AC power input can adopt Boost type single-stage PFC conversion, thereby simplifying control and improving efficiencyHigh efficiency and low cost.

Because of the DC bus voltage U _dc =760V to 535V, the primary coil current I _p ≈(1～0.7)I _pM . Because of the three-order geometric variable current rectification, the secondary coil current I _s-n ≤(1,0.7,0.5)I _sM-n . From this, it can be seen that the secondary coil current is greater than the primary coil current only when the output power is greater than 9.9kW (9.9 =11.1 × 58/65) and k < 0.158 (0.158 =0.141 × 65/58); in any other case, the secondary winding current is less than the primary winding current.

The above only is the preferred embodiment of the present invention, not so limiting the patent scope of the present invention, all of which are under the innovative concept of the present invention, the equivalent structure transformation made by the contents of the specification and the drawings is utilized, or directly or indirectly applied to other related technical fields, all included in the patent protection scope of the present invention.

Claims

1. A constant-current mode wireless charging system adopting variable-current rectification comprises a primary side part and a secondary side part, wherein the primary side part comprises an AC-DC conversion circuit (1), a DC-AC converter (2), a primary side compensation network (3) and a primary side coil Lp, and the secondary side part comprises a secondary side coil Ls, a secondary side compensation network (4), a variable-current rectifier (5) and a filter circuit (6); the AC-DC conversion circuit (1) comprises an APFC unit, realizes high power factor and regulates the output direct-current voltage; the DC-AC converter (2) adopts a full-bridge topology; the primary side compensation network (3) is an LCC topology and comprises capacitors Cp and Cr and an inductor Lr; the method is characterized in that:

the secondary side compensation network (4) adopts a three-gain CCL topology or a double-gain CCL topology, the three-gain CCL topology comprises capacitors Cs, C1, C2 and C3 and inductors L1, L2 and L3, and the double-gain CCL topology comprises capacitors Cs, C1 and C2 and inductors L1 and L2;

the converter rectifier (5) adopts a three-order converter topology or a second-order converter topology, and respectively corresponds to a three-gain CCL topology or a double-gain CCL topology of the secondary side compensation network (4); the three-order current transformation topology comprises two types, namely a three-bridge arm two-switch topology and a two-bridge arm three-switch topology; two second-order variable current topologies are available, namely a three-bridge arm one-switch topology and a two-bridge arm two-switch topology; the three-bridge arm two-switch topology comprises diodes D1, D2, D3, D4, D5 and D6 and switches S1 and S2, and the two-bridge arm three-switch topology comprises diodes D1, D2, D3 and D4 and switches S1, S2 and S3; removing the switch S2 from the three-bridge arm two-switch topology to obtain a three-bridge arm one-switch topology, and removing the switch S3 from the two-bridge arm three-switch topology to obtain a two-bridge arm two-switch topology; the switches S1, S2 and S3 are electronic switches or contactor switches;

2. The constant-current mode wireless charging system adopting variable-current rectification according to claim 1, wherein the secondary side compensation network (4) adopts a three-gain CCL topology, and the variable-current rectifier (5) adopts a three-order variable-current topology, and the connection relationship is as follows:

a first end of a secondary coil Ls is connected with a first end of a capacitor Cs, a second end of the capacitor Cs is connected with a first end of a capacitor C2 and a first end of an inductor L2, and a second end of the inductor L2 is used as a node V2; the second end of the capacitor C2 is used as a node V3; the second end of the secondary coil Ls is connected with the second end of the capacitor C1 and the first end of the inductor L1, and the second end of the inductor L1 is used as a node V1; the first end of the capacitor C1 is connected with the second end of the capacitor C3 and the first end of the inductor L3, the first end of the capacitor C3 is connected with a node V3, and the second end of the inductor L3 is used as a node V4;

the converter rectifier (5) adopts a three-bridge arm two-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, and the anode of the diode D5 and the cathode of the diode D6 are connected with the node V3; the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1 and S2, the other end of the S1 is connected with a node V1, and the other end of the S2 is connected with a node V4; the cathodes of the diodes D1, D3 and D5 are connected together to be used as the positive end Vd of the variable current rectifier (5), and the anodes of the diodes D2, D4 and D6 are connected together to be used as the ground end GND of the variable current rectifier (5);

or the converter rectifier (5) adopts a two-bridge arm three-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1, S2 and S3, the other end of the S1 is connected with the node V1, the other end of the S2 is connected with the node V4, and the other end of the S3 is connected with the node V3; the cathodes of the diodes D1 and D3 are connected together to serve as the positive terminal Vd of the converter rectifier (5), and the anodes of the diodes D2 and D4 are connected together to serve as the ground terminal GND of the converter rectifier (5).

3. The constant-current mode wireless charging system adopting variable-current rectification according to claim 1, wherein the secondary side compensation network (4) adopts a double-gain CCL topology, and the variable-current rectifier (5) adopts a second-order variable-current topology, and the connection relationship is as follows:

a first end of a secondary coil Ls is connected with a first end of a capacitor Cs, a second end of the capacitor Cs is connected with a first end of a capacitor C2 and a first end of an inductor L2, and a second end of the inductor L2 is used as a node V2; the second end of the capacitor C2 is used as a node V3; the second end of the secondary coil Ls is connected with the second end of the capacitor C1 and the first end of the inductor L1, the first end of the capacitor C1 is connected with a node V3, and the second end of the inductor L1 is used as a node V1;

the converter rectifier (5) adopts a three-bridge arm one-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, and the anode of the diode D5 and the cathode of the diode D6 are connected with the node V3; the anode of the diode D1 and the cathode of the diode D2 are connected with one end of the switch S1, and the other end of the switch S1 is connected with a node V1; the cathodes of the diodes D1, D3 and D5 are connected together to be used as the positive end Vd of the variable current rectifier (5), and the anodes of the diodes D2, D4 and D6 are connected together to be used as the ground end GND of the variable current rectifier (5);

or the converter rectifier (5) adopts a two-bridge arm two-switch topology, the anode of the diode D3 and the cathode of the diode D4 are connected with the node V2, the anode of the diode D1 and the cathode of the diode D2 are connected with one ends of the switches S1 and S2, the other end of the S1 is connected with the node V1, and the other end of the S2 is connected with the node V3; the cathodes of the diodes D1 and D3 are connected together to be used as the positive end Vd of the converter rectifier (5), and the anodes of the diodes D2 and D4 are connected together to be used as the ground end GND of the converter rectifier (5).

4. The variable current rectified constant current mode wireless charging system according to any one of claims 1 to 3, wherein: the diodes D1, D2, D3, D4, D5 and D6 are respectively replaced by switching tubes Q1, Q2, Q3, Q4, Q5 and Q6, the source electrode and the drain electrode of each switching tube respectively correspond to the anode and the cathode of each diode, and the connection relationship is kept unchanged; the switching tubes Q1, Q2, Q3, Q4, Q5 and Q6 adopt MOSFETs or IGBTs.

5. The variable-current rectification constant-current mode wireless charging system as claimed in claim 1, wherein the primary coil Lp, the secondary coil Ls, the primary compensation network (3) and the secondary compensation network (4) are designed according to the following parameter design formula for realizing variable-current rectification in the constant-current mode:

when the same self-inductance is used for the secondary windings, k is used for equations (E _ 01) and (E _ 02) _{m_3} Replacement of k _{m_h} (ii) a Self-inductance L given by formula (E _ 02) _p And L _{s_h} Is at Z _h The value at which the ground clearance has a minimum coupling coefficient;

the parameters in the formulae (E _ 01) to (E _ 05) are described below:

L _p is self-inductance of primary coil, C _p ,C _r ,L _r Parameters of the primary side compensation network (3); l is _{s_h} And L _{s_3} Respectively indicating the self-inductance of the secondary coil at Z _h And Z3 value of the ground clearance, C _{s_h-n} ,C _{1_h-n} ,C _{2_h-n} ,C _{3_h-n} ,L _{1_h-n} ,L _{2_h-n} ,L _{3_h-n} Respectively representing the parameters of the secondary compensation network (4) in Z _h The value of the nth power level of the ground clearance; l is ^* _h-n Is an intermediate variable; k is a radical of _{m_h} And k _{m_3} Are each Z _h And Z3 minimum coupling coefficient of ground clearance, k _{M_h} Is Z _h Maximum coupling coefficient of ground clearance; n =1,2,3 represents a power level; h =1,2,3 represents a ground clearance type;

g is the gain order, the triple-gain CCL topology g =3, the double-gain CCL topology g =2; q. q.s _h Is a common ratio, when g =3, if 1.385 is less than or equal to q _h If the ratio is less than or equal to 1.445, taking

L when g =2 _{3_h-n} ＝0,C _{3_h-n} = infinity, thus removed;

P _M-n and P _M-3 Maximum powers of the nth and 3 rd power classes, respectively; i is _pM The maximum current effective value of the primary coil; i is _{sM_h-n} And I _{sM_h-3} Respectively secondary side coil at Z _h Maximum current effective values for the nth and 3 rd power levels of the ground clearance; i is _oM-n The maximum value of the output current of the variable current rectifier (5) at the nth power level; u shape _dc-M The maximum value of the direct current bus voltage of the DC-AC converter (2); b is a voltammetry equilibrium coefficient, and B = 1.25-1.65 is selected; eta is the efficiency of the MF-WPT system except for the coupling coil.