Wireless electric energy transmission system and method suitable for electric vehicles with different chassis heights

Abstract

The invention relates to the technical field of power electronic converters, in particular to a wireless electric energy transmission system suitable for electric automobiles with different chassis heights, and the system comprises double inverters at a GA end, two RIITGs at the GA end and a rectifier at a VA end, in each RIITG, primary sides of m transformers are connected in parallel to form an input end of the RIITG, and the primary sides of the m transformers are connected in parallel to form an output end of the RIITG; the secondary sides of the m transformers are connected in series to form the output end of the RIITG; the output ends of the two inverters are connected with the two RIITGs in a one-to-one correspondence mode, and the input ends of the inverters are connected with direct-current bus voltage. The output ends of the RIITG are connected in parallel and are connected in 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 with the VA-end battery pack of the electric automobile. The system adapts to different input voltages and chassis heights, and a new general architecture is provided for the wireless electric energy transmission system of the electric vehicle.

Description

Technical Field

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

[0002] At present, 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, saves the trouble of connecting charging cables compared to wired power transmission, and is more convenient and safer. Therefore, the wireless power transmission system of electric vehicles has gradually received more attention.

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

[0004] The problems of the wireless power transmission system of electric vehicles are: on the one hand, due to the different power environments in different regions, there are differences in the grid voltages in different regions, and most countries and regions use both single-phase and three-phase electricity. For example, China's civilian single-phase voltage is 220V, China's three-phase voltage is 380V, the single-phase voltage in the United States is 120V, and the three-phase voltage in the United States is 240V or 480V. For different input voltages, the traditional EV WPT system needs to use different DC / DC converters and various compensation circuits on the GA end, which leads to an increase in the design and installation costs of the wireless power transmission system of electric vehicles, which is not conducive to the promotion and application of WPT technology. On the other hand, to achieve high-power and high-efficiency wireless power transmission, 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 the power transmission distance will change, and then the coupling coefficient will also change, affecting the power transmission efficiency. However, there are many types of electric vehicles on the market, and different types of electric vehicles often correspond to different chassis heights. The wireless power transmission systems of electric vehicles with different chassis heights are different. If the circuit and resonance parameters are to be redesigned for electric vehicles with different chassis heights, this will undoubtedly increase a lot of R&D and maintenance costs. Therefore, in order to achieve large-scale promotion and application of WPT technology for electric vehicles, a wireless charging solution that can adapt to different grid voltages and different power transmission distances is urgently needed. Summary of the invention

[0005] The embodiment of the present application provides a wireless power transmission system and method that can adapt to electric vehicles with different chassis heights, thereby solving the problem in the prior art that wireless power transmission systems need to be individually designed and maintained to adapt to different grid input voltages and electric vehicles with different heights, which increases the research and development, design and maintenance costs of existing wireless power transmission systems for electric vehicles and is not conducive to the promotion and application of wireless power transmission technology for electric vehicles. The embodiment of the present application realizes a general architecture of a wireless power transmission system for electric vehicles that can adapt to different input voltages and different chassis heights based on series-parallel inverters. Without changing the circuit parameters of the electric vehicle, wireless power transmission that matches a wide range of grid voltage input and electric vehicles with different chassis heights can be achieved by simply adjusting the series or parallel connection mode of the inverter and using a resonant inductor integrated transformer group (RIITG) with different turns ratios. The wireless power transmission system of the embodiment can also have technical effects such as automatic current and voltage balancing.

[0006] In a first aspect, an embodiment of the present invention provides a wireless power transmission system adapted to electric vehicles with different chassis heights, comprising: two inverters at a ground end GA, two integrated resonant inductor transformer groups RIITG at the GA end, and a rectifier at a vehicle end VA, wherein each of the RIITGs comprises 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 range, 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, and the turns ratio of each transformer is determined according to the chassis height of the electric vehicle.

[0007] Optionally, the GA end LCC resonant circuit includes: a GA end parallel resonant capacitor C f_ga , GA terminal 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.

[0008] Optionally, the VA end LCC resonant circuit includes: 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.

[0009] Optionally, 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.

[0010] Optionally, 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.

[0011] Optionally, 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 and 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.

[0012] Optionally, 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.

[0013] Optionally, 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.

[0014] Optionally, the resonant frequency of the GA end is consistent with the resonant frequency of the VA end.

[0015] Based on the same inventive concept, in a second aspect, the present invention further provides a wireless power transmission method for electric vehicles with different chassis heights, which is applied to the wireless power transmission system for electric vehicles with different chassis heights described in the first aspect, and the method 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 that electric energy can be obtained from the DC bus voltage through the target system and provided to the electric vehicle.

[0016] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: The system of the embodiment of the present invention includes a dual inverter at the GA end, a RIITG connected to each inverter at the GA end, an LCC resonant circuit at the GA end (i.e., an LCC compensation loop at the GA end), a transmitting coil at the GA end, a receiving coil at the VA end, an LCC resonant circuit at the VA end (i.e., an LCC compensation loop at the VA end), a rectifier at the VA end, and a charged battery pack at the VA end. The m transformers connected in parallel at the output ends of the dual inverters at the GA end form two identical RIITGs. The parameters of the RIITG are designed 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 resonant inductance of the LCC compensation loop at the GA end is composed of the total leakage inductance of the RIITGs connected to all inverters.

[0017] When the DC bus voltage is not greater than the first input voltage threshold, it indicates that the input voltage is small, and the input end of the first inverter is connected in parallel with the input end of the second inverter. When the DC bus voltage is not less than the second input voltage threshold, it indicates that the input voltage is large, and the input end of the first inverter is connected in series with the input end of the second inverter. This can enhance the system's voltage resistance, achieve the ability to adapt to a wide range of input voltages, and reduce device stress and save costs. Under the same conditions, compared with the conventional method, there is one less circuit, fewer devices are used, and it is easy to achieve soft switching and reduce inverter switching losses. The output end of each inverter at the GA end is 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 of the electric vehicle can also be adjusted to improve the scalability of the system. At the same time, the transformer has an isolation effect, which can suppress common-mode noise and prevent other circuits in the system from being interfered with. In addition, when the system is used for electric vehicles with different chassis heights, it only needs to adjust the turns ratio N of the transformer without changing other parameters of the system to achieve 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 realize the voltage balancing of the DC bus voltage on the input side when the input ends of the inverters are connected in series, and automatically realize the current balancing of the transformers between groups in the RIITG group when the input ends of the inverters are connected in parallel, that is, 2m transformers are current balancing when the input ends of the inverters are connected in parallel. In this way, the safety and stability of the system of the embodiment of the present invention is ensured, the power density and system efficiency of the system are improved, which is conducive to practical application and reduces the research and development, design and maintenance costs of the wireless power transmission system for electric vehicles.

[0018] Therefore, the embodiment of the present invention provides a general architecture of an electric vehicle wireless power transmission system based on a series-parallel inverter and a transformer group adapted to different input voltages and chassis heights. Without changing the circuit parameters, it is possible to achieve wireless power transmission matching a wide range of grid voltage input and different chassis heights only by adjusting the connection mode of the dual inverters in series or in parallel and using a resonant inductor integrated transformer group RIITG with different turns ratios. The embodiment of the present invention has a dual 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, and the primary windings of the transformers in each RIITG are connected in parallel, and the secondary windings are connected in series. The primary windings between different RIITGs are connected in series or in parallel with the inverter, and the secondary windings are connected in parallel in the compensation loop, which has the characteristics of automatic current 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 to improve the power density and system efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Also, throughout the accompanying drawings, the same reference figures are used to represent the same components. In the drawings: Figure 1 A schematic diagram of the circuit structure of a wireless power transmission system adapted to electric vehicles with different chassis heights in an embodiment of the present invention is shown; Figure 2 The equivalent circuit diagram of the wireless power transmission system adapted to electric vehicles with different chassis heights in an embodiment of the present invention is shown; Figure 3 The embodiment of the present invention is shown Figure 2 A simplified circuit diagram of Figure 4 A schematic diagram of the design and application steps of a wireless power transmission system for electric vehicles with different chassis heights in an embodiment of the present invention is shown; Figure 5 A schematic flow chart of the steps of a wireless power transmission method for electric vehicles with different chassis heights in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0020] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying 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 to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0021] Embodiment 1 The first embodiment of the present invention provides a wireless power transmission system adapted to electric vehicles with different chassis heights, such as Figure 1 As shown, it includes: two inverters at the ground end GA, two integrated resonant inductor transformer groups (Resonant Inductor Integrated Transformer Group) RIITG at the GA end, and a rectifier at the vehicle end VA. The two integrated resonant inductor transformer groups RIITG are respectively the first RIITG and the second RIITG. Figure 1 In the figure, 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 winding of the RIITG, i.e., the input end of the RIITG, and the secondary windings of the m transformers form the secondary winding of the RIITG, i.e., the output end of the RIITG.

[0022] Two inverters are connected to two RIITGs 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 a RIITG. Figure 1 In the figure, 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 winding of the first RIITG, and the output end of the second inverter is connected to the primary winding of the second RIITG.

[0023] The output ends of the two RIITGs are connected in parallel and connected to the transmitting coil via the GA end LCC resonant circuit, wherein the resonant inductance of the GA end LCC resonant circuit is provided by the equivalent leakage inductance of the output ends of the two RIITGs connected in parallel. Figure 1 In the embodiment, after the secondary windings of the two RIITGs are connected in parallel, the transmitting coil is connected via the LCC resonant circuit at the GA end (i.e., the LCC compensation loop at the GA end).

[0024] The transmitting coil is connected to the receiving coil accordingly, 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 VA end LCC resonant circuit (i.e., 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.

[0025] Two inverters are used for connecting the input terminals 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 terminals 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. 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.

[0026] It should be noted that the first input voltage threshold and the second input voltage threshold can be set according to actual needs. For example, when a single-phase 220V grid voltage is used for input, the DC bus voltage range is 380V-420V, and 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 used for input, the DC bus voltage range is 640V-840V, and the second input voltage threshold range can be set to 640V-840V, so that the second input voltage threshold can be set to 640V. Figure 1 In the GA terminal, the input terminals of the two inverters are connected by a short dashed line, indicating that the input terminals of the two inverters are connected in parallel. The input terminals of the two inverters are connected by a solid line, indicating that the input terminals of the two inverters are connected in series.

[0027] 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 mm, and the chassis height of an SUV is usually in the range of 150 to 200 mm. The chassis heights of different electric vehicles represent the different coupling coefficients between the transmitting coils at the GA end and the receiving coils at the VA end 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 needs of wireless charging of electric vehicles.

[0028] The system of this embodiment includes a dual inverter at the GA end, a RIITG connected to each inverter at the GA end, an LCC resonant circuit at the GA end (i.e., an LCC compensation loop at the GA end), a transmitting coil at the GA end, a receiving coil at the VA end, an LCC resonant circuit at the VA end (i.e., an LCC compensation loop at the VA end), a rectifier at the VA end, and a charged battery pack at the VA end. The output ends of the dual inverters at the GA end are respectively connected in parallel to form two identical RIITGs. The parameters of the RIITG are designed according to the conventional 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 resonant inductance of the LCC compensation loop at the GA end is composed of the total leakage inductance of the RIITGs connected to all inverters.

[0029] When the DC bus voltage is not greater than the first input voltage threshold, it indicates that the input voltage is small, and the input end of the first inverter is connected in parallel with the input end of the second inverter. When the DC bus voltage is not less than the second input voltage threshold, it indicates that the input voltage is large, and the input end of the first inverter is connected in series with the input end of the second inverter. This can enhance the system's voltage resistance, achieve the ability to adapt to a wide range of input voltages, and reduce device stress and save costs. Under the same conditions, compared with the conventional method, there is one less circuit, fewer devices are used, and it is easy to achieve soft switching and reduce inverter switching losses. The output end of each inverter at the GA end is 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 of the electric vehicle is adjusted, and the scalability of the system is improved. At the same time, the transformer has an isolation effect, which can suppress common mode noise and prevent other circuits of the system from being interfered with. In addition, when the system is used for electric vehicles with different chassis heights, it only needs to adjust the turns ratio N of the transformer without changing other parameters of the system to achieve matching of electric vehicles with different chassis heights. Moreover, the system of this embodiment can adapt to a wide range of grid voltages and electric vehicles with different power transmission distances, and can also automatically realize the voltage balancing of the input side DC bus voltage when the input ends of the inverters are connected in series, and automatically realize the current balancing of the transformers between groups when the input ends of the inverters are connected in parallel, that is, 2m transformers are current balancing when the input ends of the inverters are connected in parallel. In this way, the safety and stability of the system of this embodiment is ensured, the power density and system efficiency of the system are improved, which is conducive to practical application and reduces the research and development, design and maintenance costs of the electric vehicle wireless power transmission system.

[0030] Therefore, this embodiment provides a general architecture of an electric vehicle wireless power transmission system based on series-parallel inverters and transformer groups that adapt to different input voltages and chassis heights. Without changing the circuit parameters, it is possible to achieve wireless power transmission matching a wide range of grid voltage input and different chassis heights by only adjusting the connection mode of the dual inverters in series or in parallel and using a resonant inductor integrated transformer group RIITG with different turns ratios. This embodiment has a dual 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, and the primary windings of the transformers in each RIITG are connected in parallel, and the secondary windings are connected in series. The primary windings between different RIITGs are connected in series or in parallel with the inverters, and the secondary windings are connected in parallel in the compensation loop, which has the characteristics of automatic current 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 to improve the power density and system efficiency of the system.

[0031] Next, combine Figure 1 The system structure and principle of this embodiment are described in detail: The LCC resonant circuit at the GA end includes: a parallel resonant capacitor C at the GA end f_ga , GA terminal series resonant capacitor C ga After the secondary windings of the two RIITGs are connected in parallel, the resonant capacitor C is connected in parallel with the GA terminal. f_ga Connected in parallel. GA terminal parallel resonant capacitor C f_ga The GA terminal is connected in series with the series resonant capacitor C ga Connected in parallel with the transmitting coil.

[0032] The LCC resonant circuit at the VA end includes: the parallel resonant capacitor C at the VA end f_va , VA terminal series resonant capacitor C va , VA end series resonant inductor L f_va and receiving coil. The VA terminal series resonant capacitor C is connected in series va The receiving coil and the VA terminal parallel resonant capacitor C f_va Connected in parallel. VA terminal parallel resonant capacitor C f_va The VA terminal is connected in series with the series resonant inductor L f_va It is connected in parallel with the input terminal of the rectifier.

[0033] The resonant frequency of the GA end is consistent with the resonant frequency of the VA end, which means that the resonant frequency of the LCC resonant circuit of the GA end is consistent with the resonant frequency of the LCC resonant circuit of the VA end, so that the resonant frequencies of the GA end and the VA end are set to be the same. In this way, while the system realizes high-power transmission, it avoids the use of additional resonant inductance at the ground end and reduces the volume of the system device.

[0034] exist Figure 1 In the embodiment, each inverter can be selected as a full-bridge inverter or other inverters. Each switch tube of each inverter can be replaced by a switch tube group formed by multiple switch tubes, wherein the number of switch tubes in each switch 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, Figure 1 The first inverter 1# shown includes switch tubes S1, S2, S3 and S4, wherein each switch tube can be replaced by a switch tube group formed by multiple switch tubes, for example, switch tube S1 includes multiple switch tubes, and so on.

[0035] The rectifier is a diode rectifier or a controlled rectifier or other rectifier. For example, each diode in the diode rectifier can be replaced by a diode group formed by multiple diodes, wherein the number of diodes in each diode group can be set according to actual needs. Figure 1 The rectifier shown includes a diode D1, a diode D2, a diode D3 and a diode D4, wherein each diode can be replaced by a diode group formed by a plurality of diodes, for example, the diode D1 includes a plurality of diodes, and so on.

[0036] In this embodiment, two inverters are used: when the input ends of the two inverters are connected in series, the two inverters perform a voltage balancing operation, indicating that the input ends of the two inverters achieve voltage balancing. When the input ends of the two inverters are connected in parallel, the two RIITGs perform a current balancing operation. This means that when the input ends of the two inverters are connected in parallel, the m transformers in the RIITG achieve current balancing, and both RIITGs achieve current balancing, that is, 2m transformers achieve current balancing. In this way, it is ensured that low-stress devices can be used under different input voltages, saving costs.

[0037] The principle of the system of this embodiment: The secondary leakage inductance of the first RIITG and the secondary leakage inductance of the second RIITG are: (1); 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.

[0038] 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 resonant inductance of the LCC resonant circuit at the GA end is: (2); Wherein, Lf_ga is the equivalent resonant inductance of the LCC resonant circuit at the GA end.

[0039] The equivalent resonant inductance L of the LCC resonant circuit at the GA end f_ga And 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 And VA terminal parallel resonant capacitor C f_va Reactance X va for: (3); (4); Where ω is the operating angular frequency of the wireless power transmission system.

[0040] λ represents the situation when the system of this embodiment is connected in series or in parallel, and takes different values ​​respectively: (5).

[0041] The transmission power (i.e. output power) of the wireless power transmission system is: (6); Wherein, 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 wireless charging of electric vehicles), 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 inverter output voltage and the rectifier input voltage.

[0042] It can be seen from formula (6) that when the input voltage varies over a wide range, changing the value of λ can adjust the output power over a wide range. By changing m, the transmission power of the wireless power transmission system of electric vehicles can be adjusted to improve the scalability of the system. In addition, when charging electric vehicles with different chassis heights, the corresponding power transmission distance changes, which in turn affects the size of the coupling coefficient k. At this time, by changing the turns ratio N, the stability of the output power is also guaranteed.

[0043] Therefore, when the DC bus voltage is in the first input voltage range, it means that the input voltage is small, and the input end of the first inverter is connected in parallel with the input end of the second inverter. When the DC bus voltage is in the second input voltage range, it means that the input voltage is large, and the input end of the first inverter is connected in series with the input end of the second inverter. This can enhance the voltage resistance of the system and achieve the ability to adapt to a wide range of input voltages. By changing m, the transmission power of the wireless power transmission system of the electric vehicle can also be adjusted. In addition, when the system is used for electric vehicles with different chassis heights, it only needs to adjust the turns ratio N of the transformer without changing other parameters of the system to achieve matching of electric vehicles with different chassis heights.

[0044] like Figure 2 As shown in Figure 1, the relationship between connecting each inverter to a RIITG is equivalent to connecting a power source to a transformer. g11 Connect a transformer whose output voltage is v inv11 , until the power supply v g2m Connect a transformer, v g2m The output voltage of the connected transformer is v inv2m Among them, L k_s11 v g11 Leakage inductance of the connected transformer, L k_s2m v g2m The leakage inductance of the connected transformer, and the leakage inductance of each transformer is marked in the same way. The specific connection relationship between each power supply and a transformer is as follows: g11 Connect a transformer as an example: power supply v g11 One end of the capacitor C g11 Connect one end of the primary winding of the transformer, the power supply V g11 The other end of the primary winding of the transformer is connected to the other end of the primary winding, R g1 is the internal resistance of the primary winding of the transformer. Power supply v g11 The output current is i g11 Similarly, other power supplies are connected to a transformer circuit structure, and the corresponding electronic device numbers are changed accordingly. For example, power supply v g2m One end of the capacitor C g2m Connect one end of the primary winding of a transformer, power supply v g2m The other end of the primary winding of the transformer is connected to the other end of the primary winding, R g1 is the internal resistance of the primary winding of the transformer. Power supply v g2m The output current is i g2m .

[0045] The secondary winding of each transformer is connected in parallel, and then connected in parallel with the resonant capacitor C at the GA end. f_ga Connected in parallel, Rg2 is the internal resistance of the secondary winding of the transformer. The output current of all transformers is i inv GA terminal parallel resonant capacitor C f_ga The GA terminal is connected in series with the series resonant capacitor C ga , transmitting coil L ga Connected in parallel, R ga The transmitting coil L ga The internal resistance of the transmitting coil L ga With receiving coil L va Corresponding connection. Flowing through the transmitting coil L ga The current is i ga , flows through the receiving coil L va The current is i va .

[0046] The rectifier is equivalent to a power supply v rec . Power supply V rec The output current is i rec The VA terminal is connected in series with the series resonant inductor L f_va and power supply v rec Connect the capacitor C in parallel with the VA terminal f_va The VA terminal series resonant capacitor C is connected in parallel. va and receiving coil L va Connect the capacitor C in parallel with the VA terminal f_va Connected in parallel, R va The receiving coil L va The internal resistance.

[0047] right Figure 2 Simplify to get Figure 3 , all transformers are equivalent to power supply v inv . Power supply V inv The output current is i inv .like Figure 3 As shown, the series connected power supply v inv and the resonant inductor L of the LCC resonant circuit at the GA end f_ga (i.e. the equivalent resonant inductance at the GA end) and the parallel resonant capacitor C at the GA end f_ga Connected in parallel, R f_ga is the internal resistance of the equivalent resonant inductor at the GA end. The parallel resonant capacitor C at the GA end f_ga The GA terminal is connected in series with the series resonant capacitor C ga and the transmitting coil L ga Connected in parallel. Transmitting coil L ga With receiving coil L va Corresponding connection. Flowing through the transmitting coil L ga The current is i ga , flows through the receiving coil L vaThe current is i va .

[0048] The VA terminal series resonant inductor L is connected in series f_va and power supply v rec Connect the capacitor C in parallel with the VA terminal f_va Connected in parallel, R f_va The series resonant inductor L at the VA end f_va The VA terminal series resonant capacitor C is connected in series va and receiving coil L va Connect the capacitor C in parallel with the VA terminal f_va Connected in parallel.

[0049] Combination Figure 2 and Figure 3 The electric vehicle wireless power transmission system based on the series-parallel inverter and the integrated resonant inductor transformer group RIITG with different turns ratios proposed in this embodiment, which is adapted to different input voltages and chassis heights, becomes a conventional LCC-LCC wireless charging system after being equivalent. This means that the circuit parameters and use design experience of the conventional wireless charging system are also applicable to the system proposed in this embodiment, avoiding the redesign of the system and saving time and cost for subsequent promotion and application.

[0050] The design and application process of the system in this embodiment is as follows: Figure 4 As shown in the figure, the first step is to obtain the DC bus voltage V after the local grid voltage is boosted by PFC (Power Factor Correction). bus The second step is to use the DC bus voltage V bus Select the connection method of the dual inverter input terminal. If the DC bus voltage V bus In the first input voltage range, it means the input voltage is small, and the input terminals of the two inverters are connected in parallel. bus The second input voltage range indicates that the input voltage is large, and the input terminals of the two inverters are connected in series. The third step is to measure the coupling coefficient k according to the chassis height of the adapted electric vehicle. The fourth step is to determine the appropriate turns ratio N of the RIITG internal transformer according to k without changing the resonant network. The fifth step is to determine other parameters of the system including the compensation loop to complete the system construction.

[0051] Among them, the design target is an electric vehicle with a chassis height of 200mm (assuming that the coupling coefficient corresponding to the chassis height is 0.17), and the transformer turns ratio N=10:10 is selected at this time. When it is necessary to match another electric vehicle with a chassis height of 150mm (assuming that 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, so that the output power can remain basically unchanged.

[0052] Therefore, the system of this embodiment has the ability of self-voltage and self-current balancing, and can adapt to different input voltages and different chassis heights without the need for additional DC / DC circuits or changes in the resonant network, providing a new general architecture for electric vehicle wireless power transmission systems. The application method of the system of this embodiment also has the advantages of simplicity, high efficiency, and low cost.

[0053] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: This embodiment provides a general architecture of an electric vehicle wireless power transmission system based on a series-parallel inverter and an integrated resonant inductor transformer group RIITG with different turns ratios that can adapt to different input voltages and chassis heights. The system combines the series-parallel connection mode of the inverter and the integrated resonant inductor transformer with different turns ratios, simplifies the circuit structure of the vehicle-mounted end, and does not need to change other circuit parameters including the compensation loop, so as to achieve adaptation to a wide range of input voltages and matching of electric vehicles with different chassis heights. In addition, the system can also automatically achieve voltage and current balancing, which has obvious application value.

[0054] Embodiment 2 Based on the same inventive concept, the second embodiment of the present invention further provides a wireless power transmission system for electric vehicles with different chassis heights, which is applied to the wireless power transmission system for electric vehicles with different chassis heights described in the first embodiment. Figure 5 As shown, the method includes: S101, obtaining a DC bus voltage and a chassis height of the electric vehicle to be adapted; S102, determining a connection relationship between input terminals of two inverters of the system according to the DC bus voltage; S103, obtaining a coupling coefficient according to the chassis height; S104, obtaining a turns ratio of a transformer of the system according to the coupling coefficient; S105, 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.

[0055] Those skilled in the art will appreciate that, although the preferred embodiments of the present invention have been described, those skilled in the art, once informed of the basic creative concept, may make additional changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0056] 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 equivalents, 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, and the turns ratio of each transformer is determined according to the chassis height of the electric vehicle.

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 terminal 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 and 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, and 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 of claim 1, wherein: 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 that electric energy can be obtained from the DC bus voltage through the target system and provided to the electric vehicle.

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