Wireless Power Transmission System and Method for Electric Vehicles Adapted to Different Chassis Heights

Abstract

The present invention relates to the technical field of power electronic converters, and particularly to a wireless power transmission system for electric vehicles adapted to different chassis heights. The method includes: a dual-inverter at the GA end, two RIITGs at the GA end, and a rectifier at the VA end. In each RIITG, the primary sides of m transformers are connected in parallel as the input end of the RIITG, and the secondary sides of m transformers are connected in series as the output end of the RIITG; the output ends of the two inverters are connected to the two RIITGs in one-to-one correspondence, and the input ends of the inverters are connected to the DC bus voltage; the output ends of the RIITGs are connected in parallel and are connected to the GA-end LCC resonance circuit and the transmitting coil; the input end of the rectifier is connected to the VA-end LCC resonance circuit and the receiving coil, and the output end of the rectifier is connected to the battery pack of the electric vehicle at the VA end. This system is adapted to different input voltages and chassis heights, providing a new general architecture for the wireless power transmission system of electric vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic converters, and in particular to a general architecture of an electric vehicle wireless charging system based on series-parallel inverters and an integrated resonant inductor transformer group (RIITG) with different turns ratios to adapt to different input voltages and power transmission distances, that is, a wireless power transmission system and method for electric vehicles with different chassis heights. Background Art

[0002] Currently, various means of transportation are accelerating their green transformation. Among them, electric vehicles (EVs) have developed rapidly in recent years. Wireless power transfer (WPT), as one of the charging methods for electric vehicles, eliminates the trouble of connecting charging cables compared with wired power transmission, and is more convenient and safe. Therefore, the wireless power transmission system for electric vehicles has gradually received more attention.

[0003] The traditional wireless power transmission system mainly consists of two parts: a ground assembly (GA) and a vehicle assembly (VA). Among them, the GA side includes a power factor corrector (PFC), a DC / DC converter, an inverter, and a compensation circuit, and the VA side consists of a compensation circuit, a rectifier, a DC / DC converter, and a battery pack. Although the wireless power transmission system for electric vehicles has more advantages than the wired power transmission system, there are still some problems to be solved before it can be widely applied.

[0004] The problems of the wireless power transfer system for electric vehicles are as follows: On the one hand, due to the different power environments in different regions, there are differences in the grid voltages in different regions, and single-phase electricity and three-phase electricity are used simultaneously in most countries and regions. For example, the civil single-phase voltage in China is 220V, the three-phase voltage in China is 380V, the single-phase voltage in the United States is 120V, while the three-phase voltage in the United States is 240V or 480V. For different input voltages, traditional EV WPT systems need to use different DC / DC converters and various compensation circuits at the GA end, resulting in an increase in the design and installation costs of the wireless power transfer system for electric vehicles, which is not conducive to the popularization and application of WPT technology. On the other hand, to achieve high-power and high-efficiency wireless power transfer, it is often necessary to ensure that the transmitting coil and the receiving coil are accurately aligned and at the same height each time they are used. Otherwise, due to the change in the power transfer distance, the coupling coefficient will also change, affecting the power transfer efficiency. However, there are a wide variety of electric vehicles on the market currently, and different types of electric vehicles often correspond to different chassis heights, and the wireless power transfer systems for electric vehicles with different chassis heights are all different. If the circuit and resonant parameters need to be redesigned for electric vehicles with different chassis heights, this will undoubtedly increase a lot of R & D and maintenance costs. Therefore, to achieve the large-scale popularization and application of electric vehicle WPT technology, there is an urgent need for a wireless charging solution that can adapt to different grid voltages and different power transfer distances. Summary of the Invention

[0005] By providing a wireless power transfer system and method for electric vehicles that can adapt to different chassis heights, the embodiments of the present application solve the technical problems in the prior art that for adapting to different grid input voltages and electric vehicles with different heights, the wireless power transfer systems all need to be designed and maintained separately, increasing the R & D, design and maintenance costs of the existing wireless power transfer systems for electric vehicles, and being not conducive to the popularization and application of the wireless power transfer technology for electric vehicles. The general architecture of the wireless power transfer system for electric vehicles that can adapt to different input voltages and different chassis heights based on series-parallel inverters is realized. Without changing the circuit parameters of the electric vehicle, only by adjusting the series or parallel connection mode of the inverters and using resonant inductor integrated transformer groups (RIITG) with different turns ratios, the wireless power transfer matching for a wide range of grid voltage inputs and electric vehicles with different chassis heights can be achieved, and the wireless power transfer system of this embodiment can also have the technical effects such as automatic current sharing and voltage equalization.

[0006] In a first aspect, an embodiment of the present invention provides a wireless power transmission system for an electric vehicle adapted to different chassis heights, including: two inverters at the ground end GA, two integrated resonant inductance transformer groups RIITG at the GA end, and a rectifier at the vehicle-mounted end VA. Each of the RIITG includes m transformers, where m ≥ 1. In each RIITG, the primary windings of the m transformers are connected in parallel as the input end of the RIITG, and the secondary windings of the m transformers are connected in series as the output end of the RIITG;

[0007] The two inverters are connected to the two RIITG in a one-to-one correspondence. In each inverter, the input end of the inverter is connected to the DC bus voltage at the GA end, and the output end is connected to the input end of one of the RIITG. The output ends of the two RIITG are connected in parallel and are connected to the transmitting coil through the GA end LCC resonant circuit. The resonant inductance of the GA end LCC resonant circuit is provided by the equivalent leakage inductance after the parallel connection of the output ends of the two RIITG;

[0008] The transmitting coil is connected to the receiving coil correspondingly. The input end of the rectifier is connected to the receiving coil through the VA end LCC resonant circuit, and the output end of the rectifier is connected to the battery pack of the electric vehicle at the VA end;

[0009] The two inverters are configured to: if the DC bus voltage is not greater than the first input voltage threshold, the input ends of the two inverters are connected in parallel to the DC bus voltage; if the DC bus voltage is not less than the second input voltage range, the input ends of the two inverters are connected in series to the DC bus voltage, where the second input voltage threshold is greater than the first input voltage threshold;

[0010] The value of m for each RIITG is determined according to the transmission power of the system corresponding to the electric vehicle and the rated transmission power of each inverter, and the turns ratio of each transformer is determined according to the chassis height of the electric vehicle.

[0011] Optionally, the GA end LCC resonant circuit includes: a GA end parallel resonant capacitor C f_ga , a GA end series resonant capacitor C ga and the transmitting coil;

[0012] After the secondary side windings of the two RIITG are connected in parallel, they are connected in parallel with the GA end parallel resonant capacitor C f_ga ;

[0013] The GA end parallel resonant capacitor C f_ga is connected in series with the GA end series resonant capacitor C gais connected in parallel with the transmitting coil.

[0014] Optionally, the VA terminal LCC resonant circuit includes: a VA terminal parallel resonant capacitor C f_va , a VA terminal series resonant capacitor C va , a VA terminal series resonant inductor L f_va and the receiving coil;

[0015] The series-connected VA terminal series resonant capacitor C va and the receiving coil are connected in parallel with the VA terminal parallel resonant capacitor C f_va ;

[0016] The VA terminal parallel resonant capacitor C f_va is connected in parallel with the series-connected VA terminal series resonant inductor L f_va and the input terminal of the rectifier.

[0017] Optionally, the two integrated resonant inductance transformer groups RIITG are the first RIITG and the second RIITG respectively;

[0018] The secondary leakage inductances of the first RIITG and the second RIITG are respectively:

[0019] ;

[0020] Wherein, is the secondary leakage inductance of the first RIITG, and the is the leakage inductance of the secondary winding of the i-th transformer in the first RIITG, is the secondary leakage inductance of the second RIITG, and the is the leakage inductance of the secondary winding of the i-th transformer in the second RIITG.

[0021] Optionally, the resonant inductance of the GA terminal LCC resonant circuit is:

[0022] ;

[0023] Wherein, Lf_ga is the equivalent resonant inductance of the GA terminal LCC resonant circuit.

[0024] Optionally, the equivalent resonant inductance L f_ga of the GA terminal LCC resonant circuit and the reactance X f_ga of the GA terminal parallel resonant capacitor C ga and the reactance X of the VA terminal series resonant inductor L f_va and the VA terminal parallel resonant capacitor C f_va of the VA terminal LCC resonant circuitva is:

[0025] ;

[0026] ;

[0027] where ω is the operating angular frequency of the wireless power transfer system.

[0028] Optionally, the transmission power of the wireless power transfer system is:

[0029] ;

[0030] ;

[0031] where k is the coupling coefficient between the transmitting coil and the receiving coil, N is the turns ratio of the transformer, Lga is the inductance of the transmitting coil, Lva is the inductance of the receiving coil, Vbus represents the DC bus voltage, Vbat represents the battery pack voltage of the electric vehicle, represents the phase angle of the inverter, is the phase difference between the output voltage of the inverter and the input voltage of the rectifier.

[0032] Optionally, the two inverters are used for:

[0033] When the inputs of the two inverters are connected in series, the two inverters perform a voltage equalization operation;

[0034] When the inputs of the two inverters are connected in parallel, the two RIITGs perform a current sharing operation.

[0035] Optionally, the resonance frequency of the GA end is the same as the resonance frequency of the VA end.

[0036] Based on the same inventive concept, in a second aspect, the present invention further provides a wireless power transfer method for an electric vehicle adapted to different chassis heights, which is applied to the wireless power transfer system for an electric vehicle adapted to different chassis heights described in the first aspect. The method includes:

[0037] Obtain the DC bus voltage and the chassis height of the electric vehicle to be adapted;

[0038] Determine the connection relationship of the inputs of the two inverters of the system according to the DC bus voltage;

[0039] Obtain the coupling coefficient according to the chassis height;

[0040] Obtain the turns ratio of the transformer of the system according to the coupling coefficient;

[0041] Based on the system, in combination with the connection relationship of the input ends of the two inverters, the coupling coefficient, and the turns ratio of the transformer, a target system corresponding to the chassis height is obtained, so as to obtain electric energy from the DC bus voltage through the target system and supply the electric energy to the electric vehicle.

[0042] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0043] The system of the embodiment of the present invention includes a dual inverter at the GA end, an RIITG connected to each inverter at the GA end, an LCC resonance circuit at the GA end (i.e., the LCC compensation loop at the GA end), a transmitting coil at the GA end, a receiving coil at the VA end, an LCC resonance circuit at the VA end (i.e., the LCC compensation loop at the VA end), a rectifier at the VA end, and a charged battery pack at the VA end. m transformers connected in parallel at the output ends of the dual inverter at the GA end form two identical RIITGs. The parameter design of the RIITG is carried out according to the original LCC-LCC compensation loop for wireless charging of electric vehicles. The number m of transformers in the RIITG is determined by the transmission power of the system, and the resonance inductance of the LCC compensation loop at the GA end is composed of the total leakage inductance of all RIITGs connected to the inverter.

[0044] When the DC bus voltage is not greater than the first input voltage threshold, it indicates that the input voltage is relatively small, and the input terminals of the first inverter and the second inverter are connected in parallel. When the DC bus voltage is not less than the second input voltage threshold, it indicates that the input voltage is relatively large, and the input terminals of the first inverter and the second inverter are connected in series. This can enhance the voltage withstand capacity of the system, achieve the ability to adapt to a wide range of input voltages, reduce device stress, and save costs. Under the same conditions, compared with the conventional method, there is one less stage of circuit, fewer devices are used, soft switching is easier to achieve, and the switching loss of the inverter is reduced. The output terminals of each inverter at the GA end are connected in parallel to one end of the RIITG composed of m transformers, so that by changing m, the transmission power of the wireless power transmission system for electric vehicles can also be adjusted, improving the expandability of the system. At the same time, the transformer has an isolation effect, can suppress common-mode noise, and prevent other circuits of the system from being interfered. In addition, when this system is used for electric vehicles with different chassis heights, only the turns ratio N of the transformer needs to be adjusted, and other parameters of the system do not need to be changed, so as to achieve the matching of electric vehicles with different chassis heights. Moreover, the system of the embodiment of the present invention can adapt to a wide range of grid voltages and electric vehicles with different power transmission distances, and can also automatically achieve voltage sharing of the input-side DC bus voltage when the input terminals of the inverters are connected in series, and automatically achieve current sharing among the transformers in the RIITG group when the input terminals of the inverters are connected in parallel, that is, the 2m transformers share current when the input terminals of the inverters are connected in parallel. In this way, the safety and stability of the system of the embodiment of the present invention are ensured, the power density and system efficiency of the system are improved, which is beneficial to practical applications, and the research, design, and maintenance costs of the wireless power transmission system for electric vehicles are reduced.

[0045] Therefore, the embodiment of the present invention provides a general architecture of a wireless power transmission system for electric vehicles that adapts to different input voltages and chassis heights based on series-parallel inverters and a transformer bank. Without changing the circuit parameters, it can achieve wireless power transmission with a wide range of grid voltage inputs and different chassis height matches only by adjusting the connection mode of the double inverters in series or parallel and using resonant inductance integrated transformer banks RIITG with different turns ratios. The embodiment of the present invention has a double-inverter structure, each inverter is connected to a RIITG, and the turns ratio of the RIITG is adjusted according to different power transmission distances. The number of transformers inside each RIITG is determined by the wireless transmission power. The primary windings of the transformers in each RIITG are connected in parallel, and the secondary windings are connected in series. The primary side windings of different RIITGs are in series or parallel with the inverters, and the secondary side windings are connected in parallel in the compensation circuit, with the characteristics of automatic current sharing and voltage sharing. At the same time, the total leakage inductance of the RIITG is used as the resonant inductance of the LCC resonant circuit at the GA end, improving the power density and system efficiency of the system. Description of the Drawings

[0046] Upon reading the following detailed description of the preferred embodiments, various other advantages and benefits will become apparent to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0047] Figure 1 Fig. shows a schematic circuit diagram of a wireless power transmission system for an electric vehicle adapting to different chassis heights according to an embodiment of the present invention;

[0048] Figure 2 Fig. shows a schematic equivalent circuit diagram of a wireless power transmission system for an electric vehicle adapting to different chassis heights according to an embodiment of the present invention;

[0049] Figure 3 Fig. shows in an embodiment of the present invention Figure 2 simplified circuit schematic diagram of;

[0050] Figure 4 Fig. shows a schematic diagram of the design application steps of a wireless power transmission system for an electric vehicle adapting to different chassis heights according to an embodiment of the present invention;

[0051] Figure 5 Fig. shows a schematic diagram of the steps of a wireless power transmission method for an electric vehicle adapting to different chassis heights according to an embodiment of the present invention. Detailed Embodiments

[0052] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0053] Embodiment 1

[0054] The first embodiment of the present invention provides a wireless power transmission system for an electric vehicle adapting to different chassis heights, as Figure 1 shown, including: two inverters at the ground end GA, two Resonant Inductor Integrated Transformer Groups (RIITG) at the GA end, and one rectifier at the vehicle-mounted end VA. Among them, the two integrated resonant inductor transformer groups RIITG are the first RIITG and the second RIITG respectively. In Figure 1Among them, 1#RIITG represents the first RIITG, and 2#RIITG represents the second RIITG. Each RIITG includes m transformers, where m≥1. In each RIITG, the primary windings of the m transformers are connected in parallel as the input end of the RIITG, and the secondary windings of the m transformers are connected in series as the output end of the RIITG. In each RIITG, the primary windings of the m transformers form the primary side winding of the RIITG, that is, the input end of the RIITG, and the secondary windings of the m transformers form the secondary side winding of the RIITG, that is, the output end of the RIITG.

[0055] Two inverters are connected in one-to-one correspondence with two RIITGs. In each inverter, the input end of the inverter is connected to the DC bus voltage at the GA end, and the output end is connected to the input end of one RIITG. In Figure 1 Among them, 1# inverter represents the first inverter, and 2# inverter represents the second inverter. The output end of the first inverter is connected to the primary side winding of the first RIITG, and the output end of the second inverter is connected to the primary side winding of the second RIITG.

[0056] The output ends of the two RIITGs are connected in parallel and connected to the transmitting coil through the LCC resonance circuit at the GA end. Among them, the resonance inductor of the LCC resonance circuit at the GA end is provided by the equivalent leakage inductance after the parallel connection of the output ends of the two RIITGs. In Figure 1 Among them, after the secondary side windings of the two RIITGs are connected in parallel, they are connected to the transmitting coil through the LCC resonance circuit at the GA end (that is, the LCC compensation loop at the GA end).

[0057] The transmitting coil is connected in correspondence with the receiving coil, so that the transmitting coil transmits the electric energy at the GA end to the receiving coil, and then transmits it to the battery pack of the electric vehicle through the receiving coil. The input end of the rectifier is connected to the receiving coil through the LCC resonance circuit at the VA end (that is, the LCC compensation loop at the VA end), and the output end of the rectifier is connected to the battery pack of the electric vehicle at the VA end.

[0058] Two inverters are used to: if the DC bus voltage is not greater than the first input voltage threshold, the input ends of the two inverters are connected in parallel to the DC bus voltage; if the DC bus voltage is not less than the second input voltage threshold, the input ends of the two inverters are connected in series to the DC bus voltage, where the second input voltage threshold is greater than the first input voltage threshold. The m of each RIITG is determined according to the transmission power of the system corresponding to the electric vehicle and the rated transmission power of each inverter, and the turns ratio of each transformer is determined according to the chassis height of the electric vehicle.

[0059] It should be noted that the first input voltage threshold and the second input voltage threshold can be reliably set according to actual requirements. For example, when a single-phase 220V grid voltage is input, the DC bus voltage range is 380V - 420V, then the first input voltage threshold range can be set to 380V - 420V, so that the first input voltage threshold can be set to 420V. When a three-phase 380V grid voltage is input, the DC bus voltage range is 640V - 840V, then the second input voltage threshold range can be set to 640V - 840V, so that the second input voltage threshold can be set to 640V. In Figure 1 In it, in the GA terminal, the input ends of the two inverters are connected by short dashed lines, indicating that the input ends of the two inverters are connected in parallel. The input ends of the two inverters are connected by solid lines, indicating that the input ends of the two inverters are connected in series.

[0060] The chassis heights of different electric vehicles are different, and electric vehicles with different chassis heights are different types of electric vehicles. For example, the chassis height of a family car is usually in the range of 110 to 150 millimeters, and the chassis height of an SUV is usually in the range of 150 to 200 millimeters. The chassis heights of different electric vehicles represent different coupling coefficients between the transmitting coil at the GA terminal and the receiving coil at the VA terminal in the system of this embodiment. In addition, the coil design is not the content of this embodiment, and the relative position relationship between the coils depends on the actual requirements of electric vehicle wireless charging.

[0061] The system of this embodiment includes a dual inverter at the GA terminal, an RIITG connected to each inverter at the GA terminal, an LCC resonant circuit at the GA terminal (i.e., the LCC compensation loop at the GA terminal), a transmitting coil at the GA terminal, a receiving coil at the VA terminal, an LCC resonant circuit at the VA terminal (i.e., the LCC compensation loop at the VA terminal), a rectifier at the VA terminal, and a battery pack for charging at the VA terminal. Two identical RIITGs are formed by m transformers whose output terminals of the dual inverter at the GA terminal are respectively connected in parallel. The parameters of the RIITG are designed according to the conventional LCC-LCC compensation loop for electric vehicle wireless charging. The number m of transformers in the RIITG is determined by the transmission power of the system, and the resonant inductor of the LCC compensation loop at the GA terminal is composed of the total leakage inductance of all RIITGs connected to the inverters.

[0062] When the DC bus voltage is not greater than the first input voltage threshold, it indicates that the input voltage is relatively small, and the input terminals of the first inverter and the second inverter are connected in parallel. When the DC bus voltage is not less than the second input voltage threshold, it indicates that the input voltage is relatively large, and the input terminals of the first inverter and the second inverter are connected in series. This can enhance the voltage withstand capacity of the system, realize the ability to adapt to a wide range of input voltages, reduce device stress, and save costs. Under the same conditions, compared with the conventional method, one stage of circuit is less, and fewer devices are used, making it easier to achieve soft switching and reduce the inverter switching loss. One end of the RIITG composed of m transformers, which is connected in parallel to the output terminal of each inverter at the GA end, enables the adjustment of the transmission power of the wireless power transmission system for electric vehicles by changing m, improving the expandability of the system. At the same time, the transformer has an isolation effect, can suppress common-mode noise, and prevent other circuits of the system from being interfered. In addition, when this system is used for electric vehicles with different chassis heights, only the turns ratio N of the transformer needs to be adjusted, without changing other parameters of the system, to achieve the matching of electric vehicles with different chassis heights. Moreover, while the system of this embodiment adapts to a wide range of grid voltages and electric vehicles with different power transmission distances, it can also automatically achieve voltage sharing of the input-side DC bus voltage when the input terminals of the inverter are connected in series, and automatically achieve current sharing among the transformers in the group within the RIITG when the input terminals of the inverter are connected in parallel, that is, the 2m transformers share current when the input terminals of the inverter are connected in parallel. In this way, the safety and stability of the system of this embodiment are ensured, the power density and system efficiency of the system are improved, which is beneficial to practical applications, and the R & D, design, and maintenance costs of the wireless power transmission system for electric vehicles are reduced.

[0063] Therefore, this embodiment provides a general architecture of a wireless power transmission system for electric vehicles that adapts to different input voltages and chassis heights based on series-parallel inverters and transformer groups. Without changing the circuit parameters, it can achieve wireless power transmission with a wide range of grid voltage inputs and different chassis height matching only by adjusting the connection mode of the double inverters in series or parallel and using resonant inductance integrated transformer groups RIITG with different turns ratios. This embodiment has a double-inverter structure, each inverter is connected to a RIITG, and the turns ratio of the RIITG is adjusted according to different power transmission distances. The number of transformers inside each RIITG is determined by the wireless transmission power. The primary windings of the transformers in each RIITG are connected in parallel, and the secondary windings are connected in series. The primary side windings of different RIITGs are in series or parallel with the inverter, and the secondary side windings are connected in parallel to the compensation circuit, with the characteristics of automatic current sharing and voltage sharing. At the same time, the total leakage inductance of the RIITG is used as the resonant inductance of the LCC resonant circuit at the GA end, improving the power density and system efficiency of the system.

[0064] Next, in combination with Figure 1Elaborate on the system structure and principle of this embodiment:

[0065] The LCC resonant circuit at the GA end includes: a parallel resonant capacitor C at the GA end f_ga , a series resonant capacitor C at the GA end ga and a transmitting coil. After the secondary side windings of two RIITGs are connected in parallel, they are connected in parallel with the parallel resonant capacitor C at the GA end f_ga . The parallel resonant capacitor C at the GA end f_ga is connected in parallel with the series-connected series resonant capacitor C at the GA end ga and the transmitting coil.

[0066] The LCC resonant circuit at the VA end includes: a parallel resonant capacitor C at the VA end f_va , a series resonant capacitor C at the VA end va , a series resonant inductor L at the VA end f_va and a receiving coil. The series-connected series resonant capacitor C at the VA end va and the receiving coil are connected in parallel with the parallel resonant capacitor C at the VA end f_va . The parallel resonant capacitor C at the VA end f_va is connected in parallel with the series-connected series resonant inductor L at the VA end f_va and the input end of the rectifier.

[0067] The resonant frequency at the GA end is the same as the resonant frequency at the VA end, indicating that the resonant frequency of the LCC resonant circuit at the GA end is the same as the resonant frequency of the LCC resonant circuit at the VA end, so that the resonant frequencies at the GA end and the VA end are set to be the same. In this way, while the system realizes high-power transmission, the use of an additional resonant inductor at the ground end is avoided, and the volume of the system device is reduced.

[0068] In Figure 1 , each inverter can be selected as a full-bridge inverter or other inverters. Each switching tube of each inverter can be replaced by a switching tube group formed by multiple switching tubes, where the number of switching tubes in each switching tube group can be set according to actual needs, that is, the specific number is selected in combination with device stress and cost. For example, as Figure 1 shown, the first inverter, the 1# inverter, includes switching tubes S1, S2, S3, and S4. Among them, each switching tube can be replaced by a switching tube group formed by multiple switching tubes. For example, switching tube S1 includes multiple switching tubes, and so on.

[0069] The rectifier is a diode rectifier or a controllable rectifier or other rectifiers. For example, each diode in the diode rectifier can be replaced by a diode group formed by multiple diodes, where the number of diodes in each diode group can be set according to actual needs. For example, as Figure 1The rectifier shown includes diode D1, diode D2, diode D3, and diode D4. Among them, each diode can be replaced by a diode group formed by multiple diodes. For example, diode D1 includes multiple diodes, and so on.

[0070] In this embodiment, two inverters are used to: when the input ends of the two inverters are in series connection, the two inverters perform a voltage equalization operation, indicating that the input ends of the two inverters achieve voltage equalization. When the input ends of the two inverters are in parallel connection, the two RIITGs perform a current sharing operation. This means that when the input ends of the two inverters are in parallel connection, the m transformers in the RIITG achieve current sharing, and both of the two RIITGs achieve current sharing, that is, 2m transformers achieve current sharing. In this way, it is ensured that low-stress devices can be used under different input voltages, saving costs.

[0071] The principle of the system in this embodiment:

[0072] The secondary leakage inductances of the first RIITG and the second RIITG are respectively:

[0073] (1);

[0074] Among them, is the secondary leakage inductance of the first RIITG, is the leakage inductance of the secondary winding of the i-th transformer in the first RIITG, is the secondary leakage inductance of the second RIITG, is the leakage inductance of the secondary winding of the i-th transformer in the second RIITG.

[0075] The resonant inductor of the LCC resonant circuit at the GA end is provided by the equivalent leakage inductance after the output ends of the two RIITGs are connected in parallel. The resonant inductor of the LCC resonant circuit at the GA end is:

[0076] (2);

[0077] Among them, Lf_ga is the equivalent resonant inductor of the LCC resonant circuit at the GA end.

[0078] The equivalent resonant inductor L of the LCC resonant circuit at the GA end f_ga and the reactance X of the parallel resonant capacitor C at the GA end f_ga are: ga The series resonant inductor L at the VA end of the LCC resonant circuit at the VA end f_va and the reactance X of the parallel resonant capacitor C at the VA end f_va are: va (3);

[0079] (3);

[0080] (4);

[0081] Where ω is the operating angular frequency of the wireless power transfer system.

[0082] Let λ represent the series or parallel situation of the system in this embodiment, and take different values respectively:

[0083] (5).

[0084] The transmission power (i.e., output power) of the wireless power transfer system is:

[0085] (6);

[0086] Where k is the coupling coefficient between the transmitting coil and the receiving coil (the coil design is not the content of this embodiment, and the relative position relationship between the coils depends on the actual requirements of electric vehicle wireless charging), N is the turns ratio of the transformer, Lga is the inductance of the transmitting coil, Lva is the inductance of the receiving coil, Vbus represents the DC bus voltage, Vbat represents the battery pack voltage of the electric vehicle, represents the phase angle of the inverter, is the phase difference between the output voltage of the inverter and the input voltage of the rectifier.

[0087] It can be seen from formula (6) that when the input voltage varies within a large range, changing the value of λ can adjust the output power within a large range. By changing m, the transmission power of the wireless power transfer system of the electric vehicle is adjusted, improving the expandability of the system. In addition, when charging electric vehicles with different chassis heights, corresponding to the change in the power transmission distance, which in turn affects the magnitude of the coupling coefficient k. At this time, by changing the turns ratio N, the stability of the output power is also ensured.

[0088] Therefore, when the DC bus voltage is within the first input voltage range, it means that the input voltage is small, and the input terminals of the first inverter and the second inverter are connected in parallel. When the DC bus voltage is within the second input voltage range, it means that the input voltage is large, and the input terminals of the first inverter and the second inverter are connected in series. This can enhance the voltage withstand capacity of the system and realize the ability to adapt to a wide range of input voltages. By changing m, the transmission power of the wireless power transfer system of the electric vehicle can also be adjusted. In addition, when this system is used for electric vehicles with different chassis heights, only by adjusting the turns ratio N of the transformer, without changing other parameters of the system, the matching of electric vehicles with different chassis heights can be achieved.

[0089] Such as Figure 2As shown, the relationship of connecting each inverter to an RIITG is equivalent to connecting a power supply to a transformer. For example, the first power supply v g11 is connected to a transformer, and the output voltage of this transformer is v inv11 , until the power supply v g2m is connected to a transformer, and the output voltage of the transformer connected by v g2m is v inv2m . Among them, L k_s11 is the leakage inductance of the transformer connected by v g11 , and L k_s2m is the leakage inductance of the transformer connected by v g2m . The leakage inductance identification of each transformer follows this analogy. The specific connection relationship of each power supply connected to a transformer is that taking the connection of the first power supply v g11 to a transformer as an example: one end of the power supply v g11 is connected to one end of the primary winding of the transformer through the capacitor C g11 , and the other end of the power supply v g11 is connected to the other end of the primary winding of the transformer. R g1 is the internal resistance of the primary winding of the transformer. The output current of the power supply v g11 is i g11 . By analogy, for the circuit structure of other power supplies connected to a transformer, the numbers of the corresponding electronic devices change accordingly. For example, one end of the power supply v g2m is connected to one end of the primary winding of a transformer through the capacitor C g2m , and the other end of the power supply v g2m is connected to the other end of the primary winding of the transformer. R g1 is the internal resistance of the primary winding of the transformer. The output current of the power supply v g2m is i g2m .

[0090] The secondary windings of each transformer are connected in parallel, and then are connected in parallel with the parallel resonance capacitor C f_ga at the GA end. R g2 is the internal resistance of the secondary winding of the transformer. The output current of all transformers is i inv . The parallel resonance capacitor C f_ga at the GA end is connected in parallel with the series-connected series resonance capacitor C ga at the GA end and the transmitting coil L ga . R ga is the internal resistance of the transmitting coil L ga . The transmitting coil L ga is correspondingly connected to the receiving coil L va . The current flowing through the transmitting coil L ga is i ga , and the current flowing through the receiving coil L va is i va。

[0091] The rectifier is equivalent to the power supply v rec 。The power supply v rec has an output current of i rec 。The series-connected VA terminal series resonance inductor L f_va and the power supply v rec are in parallel connection with the VA terminal parallel resonance capacitor C f_va 。The series-connected VA terminal series resonance capacitor C va and the receiving coil L va are in parallel connection with the VA terminal parallel resonance capacitor C f_va ,and R va is the internal resistance of the receiving coil L va 。

[0092] For Figure 2 simplification, we get Figure 3 ,equivalent all transformers to the power supply v inv 。The power supply v inv has an output current of i inv 。As Figure 3 shown, the series-connected power supply v inv and the resonance inductor L of the GA terminal LCC resonance circuit f_ga (i.e., the equivalent resonance inductor of the GA terminal) are in parallel connection with the GA terminal parallel resonance capacitor C f_ga ,and R f_ga is the internal resistance of the equivalent resonance inductor of the GA terminal. The GA terminal parallel resonance capacitor C f_ga is in parallel connection with the series-connected GA terminal series resonance capacitor C ga and the transmitting coil L ga 。The transmitting coil L ga is correspondingly connected to the receiving coil L va 。The current flowing through the transmitting coil L ga is i ga ,and the current flowing through the receiving coil L va is i va 。

[0093] The series-connected VA terminal series resonance inductor L f_va and the power supply v rec are in parallel connection with the VA terminal parallel resonance capacitor C f_va ,and R f_va is the internal resistance of the VA terminal series resonance inductor L f_va 。The series-connected VA terminal series resonance capacitor C va and the receiving coil L va are in parallel connection with the VA terminal parallel resonance capacitor C f_va 。

[0094] Combining Figure 2 andFigure 3 , after being equivalent, the electric vehicle wireless power transfer system based on the series - parallel inverter and the integrated resonant inductor transformer group (RIITG) with different turns ratios proposed in this embodiment becomes a conventional LCC - LCC wireless charging system. This means that the circuit parameters of the conventional wireless charging system and the design experience are also applicable to the system proposed in this embodiment, avoiding the need for a re - design of the system and saving time and cost for subsequent popularization and application.

[0095] The design and application process of the system in this embodiment is as follows: Figure 4 As shown, in the first step, after boosting the grid voltage of the location through a PFC (Power Factor Correction), the DC bus voltage V bus is obtained. In the second step, according to the DC bus voltage V bus , the connection method of the input ends of the dual inverters is selected. If the DC bus voltage V bus is within the first input voltage range, indicating a relatively small input voltage, the input ends of the two inverters are connected in parallel. If the DC bus voltage V bus is within the second input voltage range, indicating a relatively large input voltage, the input ends of the two inverters are connected in series. In the third step, the coupling coefficient k is measured according to the chassis height of the adapted electric vehicle. In the fourth step, without changing the resonant network, the appropriate turns ratio N of the transformer inside the RIITG is determined according to k. In the fifth step, other parameters of the system including the compensation circuit are determined to complete the construction of the system.

[0096] Among them, taking an electric vehicle with a chassis height of 200 mm as the design target (assuming the coupling coefficient corresponding to this chassis height is 0.17), the turns ratio N of the transformer selected at this time is 10:10. When it is necessary to match another electric vehicle with a chassis height of 150 mm (assuming the coupling coefficient is 0.25), the transformer turns ratio is changed to N = 14:10. The change in the transformer turns ratio basically offsets the change in the coupling coefficient, enabling the output power to remain basically unchanged.

[0097] Therefore, the system in this embodiment has the capabilities of self - voltage equalization and self - current equalization, and can adapt to different input voltages and different chassis heights without an additional DC / DC circuit or changing the resonant network, providing a new general architecture for the electric vehicle wireless power transfer system. The application method of the system in this embodiment also has the advantages of simplicity, high efficiency, and low cost.

[0098] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0099] This embodiment provides a general architecture of a wireless power transfer system for electric vehicles that is based on a series-parallel inverter and an integrated resonant inductor transformer group (RIITG) with different turns ratios to adapt to different input voltages and chassis heights. This system combines the series-parallel connection methods of inverters and integrated resonant inductors transformers with different turns ratios, streamlines the circuit structure on the vehicle side, and can adapt to a wide range of input voltages and match electric vehicles with different chassis heights without changing other circuit parameters, including the compensation circuit. Moreover, this system can automatically achieve voltage equalization and current sharing, and has obvious application value.

[0100] Embodiment 2

[0101] Based on the same inventive concept, the second embodiment of the present invention also provides a wireless power transfer system for electric vehicles that adapts to different chassis heights and is applied to the wireless power transfer system for electric vehicles that adapts to different chassis heights described in Embodiment 1, as Figure 5 shown. This method includes:

[0102] S101, obtaining the DC bus voltage and the chassis height of the electric vehicle to be adapted;

[0103] S102, determining the connection relationship of the input ends of the two inverters of the system according to the DC bus voltage;

[0104] S103, obtaining the coupling coefficient according to the chassis height;

[0105] S104, obtaining the turns ratio of the transformer of the system according to the coupling coefficient;

[0106] S105, based on the system, combining the connection relationship of the input ends of the two inverters, the coupling coefficient, and the turns ratio of the transformer, obtaining the target system corresponding to the chassis height, so as to obtain electrical energy from the DC bus voltage through the target system and supply the electrical energy to the electric vehicle.

[0107] Those skilled in the art should understand that although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concepts, they can make additional changes and modifications to these embodiments. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0108] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A wireless power transmission system adapted to electric vehicles with different chassis heights, characterized in that: include: Two inverters at the ground end GA, two integrated resonant inductor transformer groups RIITG at the GA end, and a rectifier at the vehicle end VA, wherein each of the RIITGs includes m transformers, m≥1, and in each of the RIITGs, the primary windings of the m transformers are connected in parallel as the input end of the RIITG, and the secondary windings of the m transformers are connected in series as the output end of the RIITG; The two inverters are connected to the two RIITGs in a one-to-one correspondence. In each inverter, the input end of the inverter is connected to the DC bus voltage of the GA end, and the output end is connected to the input end of one RIITG. The output ends of the two RIITGs are connected in parallel and connected to the transmitting coil through the LCC resonant circuit at the GA end, wherein the resonant inductance of the LCC resonant circuit at the GA end is provided by the equivalent leakage inductance of the output ends of the two RIITGs connected in parallel. The transmitting coil is connected to the receiving coil correspondingly; the input end of the rectifier is connected to the receiving coil through the VA end LCC resonant circuit, and the output end of the rectifier is connected to the battery pack of the electric vehicle at the VA end; The two inverters are used for connecting the input ends of the two inverters in parallel to the DC bus voltage if the DC bus voltage is not greater than a first input voltage threshold; and connecting the input ends of the two inverters in series to the DC bus voltage if the DC bus voltage is not less than a second input voltage threshold, wherein the second input voltage threshold is greater than the first input voltage threshold; The m of each RIITG is determined according to the transmission power of the system corresponding to the electric vehicle and the rated transmission power of each inverter, so that the transmission power of the wireless power transmission system can be adjusted by changing m; the turns ratio of each transformer is determined according to the chassis height of the electric vehicle, so that the power transmission distance corresponding to different chassis heights can be adapted by changing the turns ratio of each transformer, and the stability of the transmission power can be ensured.

2. The system according to claim 1, characterized in that The GA end LCC resonant circuit comprises: a GA end parallel resonant capacitor C f_ga , GA end series resonant capacitor C ga and the transmitting coil; After the two secondary windings of the RIITG are connected in parallel, a resonant capacitor C is connected in parallel with the GA end. f_ga Connected in parallel; The GA terminal parallel resonant capacitor C f_ga The GA terminal is connected in series with the series resonant capacitor C ga The transmitting coil is connected in parallel.

3. The system according to claim 2, characterized in that The VA end LCC resonant circuit comprises: a VA end parallel resonant capacitor C f_va , VA terminal series resonant capacitor C va , VA end series resonant inductor L f_va and the receiving coil; The VA terminal is connected in series with a series resonant capacitor C va The receiving coil and the VA terminal parallel resonant capacitor C f_va Connected in parallel; The VA terminal parallel resonant capacitor C f_va The VA terminal is connected in series with the series resonant inductor L f_va The rectifier is connected in parallel with the input end of the rectifier.

4. The system according to claim 3, characterized in that The two integrated resonant inductor transformer groups RIITG are respectively a first RIITG and a second RIITG; The secondary side leakage inductance of the first RIITG and the secondary side leakage inductance of the second RIITG are respectively: ； in, is the secondary leakage inductance of the first RIITG, is the leakage inductance of the secondary winding of the i-th transformer in the first RIITG, is the secondary leakage inductance of the second RIITG, is the leakage inductance of the secondary winding of the i-th transformer in the second RIITG.

5. The system according to claim 4, characterized in that The resonant inductance of the LCC resonant circuit at the GA end is: ； Wherein, Lf_ga is the equivalent resonant inductance of the LCC resonant circuit at the GA end.

6. The system according to claim 5, characterized in that The equivalent resonant inductance L of the LCC resonant circuit at the GA end is f_ga and the GA terminal parallel resonant capacitor C f_ga Reactance X ga The VA end of the LCC resonant circuit is connected in series with the VA end resonant inductor L f_va The VA terminal parallel resonant capacitor C f_va Reactance X va for: ； ； Wherein, ω is the operating angular frequency of the wireless power transmission system.

7. The system according to claim 6, characterized in that The transmission power of the wireless power transmission system is: ； ； Wherein, k is the coupling coefficient between the transmitting coil and the receiving coil, N is the turns ratio of the transformer, Lga is the inductance of the transmitting coil, Lva is the inductance of the receiving coil, Vbus represents the DC bus voltage, Vbat represents the battery pack voltage of the electric vehicle, represents the phase angle of the inverter, is the phase difference between the output voltage of the inverter and the input voltage of the rectifier.

8. The system of claim 1, wherein: The two inverters are used for: Under the condition that the input ends of the two inverters are in series connection, the two inverters perform a voltage balancing operation; Under the condition that the input ends of the two inverters are connected in parallel, the two RIITGs perform current sharing operation.

9. The system according to claim 1, characterized in that The resonant frequency of the LCC resonant circuit at the GA end is consistent with the resonant frequency of the LCC resonant circuit at the VA end.

10. A wireless power transmission method for electric vehicles with different chassis heights, characterized in that: The method applied to the wireless power transmission system for electric vehicles adapting to different chassis heights as claimed in any one of claims 1 to 9 comprises: Obtaining the DC bus voltage and the chassis height of the electric vehicle to be adapted; Determining a connection relationship between input terminals of two inverters of the system according to the DC bus voltage; According to the chassis height, a coupling coefficient is obtained; According to the coupling coefficient, a turns ratio of a transformer of the system is obtained; Based on the system, combined with the connection relationship between the input ends of the two inverters, the coupling coefficient and the turns ratio of the transformer, a target system corresponding to the chassis height is obtained, so as to obtain electric energy from the DC bus voltage through the target system and provide the electric energy to the electric vehicle.

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