A high-power electric vehicle dynamic wireless charging system with dual transmission and dual pickup

Abstract

The present invention relates to the technical field of dynamic wireless charging of electric vehicles, and specifically discloses a dual-transmitter and dual-pickup high-power dynamic wireless charging system for electric vehicles, which uses a dual-transmitter and dual-pickup coupling mechanism to improve the output power level. A unipolar coil is integrated in the pickup coil as a compensation inductor, and the resonant network is integrated with the pickup coil, so that the structure of the pickup end is more compact; by using the segmented compensation method of the pickup coil, the port voltage is reduced to meet the voltage limit of the vehicle-mounted equipment. The present invention also provides a parameter design method for the transmitting coil, taking into account the exposure time of the magnetic field in the dynamic process, and under the premise of meeting the power level and low cost, the length of the transmitting coil can meet the two power levels of single-pickup electric vehicles and dual-pickup electric buses, thereby improving the interoperability of the system. The system operates at 85kHz, the power transmission distance is 18cm, and when the transmission power is 62kW, the DC / DC efficiency reaches 87%.

Description

Technical Field

[0001] The present invention relates to the technical field of dynamic wireless charging of electric vehicles, and in particular to a high-power dynamic wireless charging system for electric vehicles with dual emission and dual pickup. Background Art

[0002] Wireless power transfer (WPT) technology uses magnetic fields, electric fields, lasers, microwaves or other carriers to transfer electricity from a power source to an electrical device without electrical contact. Magnetic coupling wireless power transfer (MC-WPT) technology is a commonly used transmission method in wireless charging of electric vehicles (EVs), especially electric vehicle dynamic wireless power transfer technology (EV-DWPT). This technology can not only increase the range of electric vehicles, but also reduce the capacity of the battery. If 20% of the roads have a 40kW dynamic charging system, the driving range of electric vehicles can be extended by at least 80%. The reduction in on-board battery capacity reduces both vehicle cost and vehicle weight.

[0003] According to the length of the transmitting coil, the EV-DWPT system can be divided into long rail and short rail transmitting coil structures. In the long rail transmitting coil structure, the transmitting coil is much longer than the pickup end. In the short rail transmitting coil structure, the size of the transmitting coil is close to that of the electric vehicle, and the coupling with the pickup coil is more ideal. The short rail transmitting coil structure can power multiple electric vehicles by independently controlling the transmitting coil while avoiding the exposure of the magnetic field of the transmitting coil in the uncharged area. Therefore, the short rail transmitting coil structure helps to improve the efficiency and safety of power transmission in the EV-DWPT system, and has more practical application value.

[0004] It should be noted that most of the current research is in the R&D stage, but EV-DWPT still faces many challenges in commercial applications, such as improving the power capacity of the system, the interoperability of charging roads for vehicles with different power, and the adaptability of the pickup device to the vehicle.

[0005] Electric buses are a very important means of transportation, and EV-DWPT technology is also needed to extend the driving range. However, due to the limitations of the current withstand voltage indicators of power devices and the safety issues caused by high coil voltage stress, the single-transmitter single-pickup (STSP) DWPT system is difficult to meet the higher power requirements in electric bus applications. Therefore, a multi-transmitter multi-pickup structure can be used to increase the number of power transmission paths, thereby increasing the level of system output power. At present, a method has proposed a dual-transmitter dual-pickup (DTDP) structure for a static wireless charging system, in which the currents of the two transmitting coils of the structure are in reverse phase to reduce magnetic field radiation. Another method has proposed another system with dual-transmitter dual-pickup, in which the coils on the same side are decoupled from each other and activated by one or two inverters. The above methods all use a dual-transmitter dual-pickup structure to increase the power capacity of the system, but are mainly used for static wireless power transmission of electric vehicles.

[0006] The high manufacturing cost has hindered the promotion of practical application of EV-DWPT system to some extent, which is due to the large number of power modules and compensation components used in short guide rails. In order to reduce costs, there is a method to connect / disconnect the corresponding transmitting coils through relays. This method does reduce the number of inverters. However, due to the long switching time of relays and the life problem of frequent switching, this method can only be limited to application scenarios with slow movement and small power levels. There are also methods to use one inverter to drive multiple coils, but too many compensation networks in parallel with the inverter will lead to reduced system efficiency.

[0007] In addition, the practical application and commercial promotion of EV-DWPT must also consider the interoperability of the transmitting coil for vehicles of different power and the adaptability of the pickup device to the vehicle. Currently, there is little research in the relevant literature. Summary of the invention

[0008] The present invention provides a high-power electric vehicle dynamic wireless charging system with dual transmission and dual pickup. In the practical application and commercial promotion of the EV-DWPT system, the technical problems to be solved are: how to improve the power level of the EV-DWPT system so that it can meet the power requirements of electric buses; how to improve the interoperability of the system so that the EV-DWPT system road can meet the needs of both electric vehicles and electric buses; and how to improve the adaptability of the pickup end to the vehicle at a high power level.

[0009] In order to solve the above technical problems, the present invention provides a dual-transmitting and dual-pickup high-power electric vehicle dynamic wireless charging system, comprising a transmitting end and a receiving end, wherein the transmitting end comprises a plurality of power units, each of the power units comprises two transmitting coils connected in parallel, the two transmitting coils are respectively connected to a corresponding transmitting end compensation network and then connected to the same high-frequency inverter, and all the transmitting coils are evenly arranged at equal distances along the road direction; the receiving end comprises two pick-up ends, each of the pick-up ends comprises a pick-up coil and a receiving end compensation network and a rectifier circuit connected to the rear stage;

[0010] During the movement of the electric vehicle, the transmitting coil below the pickup coil is always powered, and the other transmitting coils are powered off;

[0011] The parameters of the transmitting coil and the pickup coil are designed using the following steps:

[0012] S1. Determine the length, width and number of turns of the pickup coil and the distance between the two pickup coils according to the space limitation in vehicle modification;

[0013] S2. Determine the width, number of turns and winding area width of the transmitting coil according to the pickup coil designed in step S1;

[0014] S3. Determine, based on experience and actual needs, that the distance between two adjacent transmitting coils is no more than 10 cm;

[0015] S4. Determine the system output power P according to actual needs out and the maximum current I of the transmitting coil ti ;

[0016] S5. According to Calculate the minimum mutual inductance M between the transmitting coil and the pickup coil min , ω represents the operating angular frequency of the system, L r is the self-inductance of the pickup coil, Q is the load quality factor of the receiving end;

[0017] S6, at the minimum mutual inductance M min Under the restriction of , the length of the transmitting coil is determined according to actual needs by comprehensively considering the influence of the length of the transmitting coil on the self-inductance of the transmitting coil, the mutual inductance between the transmitting coil and the pickup coil, the cost, the magnetic field exposure time, and the interoperability of heavy vehicles and light vehicles.

[0018] Furthermore, in step S1:

[0019] Considering the space limitation of vehicle modification, the size of the pickup coil is set to 80cm*62cm, the number of turns of the pickup coil is 9, and the distance between the two pickup coils is set to 2.8m. The receiving end compensation network adopts an LCC compensation network, including a pickup end compensation inductor, a pickup end parallel compensation capacitor, and a pickup end series compensation capacitor.

[0020] Furthermore, in step S1:

[0021] In order to improve the power density of the pickup end, reduce the size of the pickup end, and thus improve the adaptability of the pickup end to the vehicle. The pickup coil adopts a three-wire parallel winding method, and three thin wires are used instead of a single thick wire. The pickup end compensation inductor adopts a unipolar coil integrated in the central blank area of ​​the pickup coil. The unipolar coil adopts a two-wire parallel winding method, and is wound with the same specification of wire as the pickup coil. The number of turns is 5, and its size is set to 30cm*20cm.

[0022] Furthermore, in step S1:

[0023] In order to reduce the port voltage of the pickup coil and thus improve the adaptability of the pickup end to the vehicle. The pickup end series compensation capacitor adopts a segmented compensation method, and the port voltage of the pickup coil is reduced to 1.4kV, which is lower than 4.5kV in GB / T39752-2021. Under the premise of meeting the space modification of the pickup end and the port voltage limit of the pickup coil, the size of the pickup end is 80cm×62cm×6cm, which can be applied to various models.

[0024] Further, in step S2:

[0025] According to step S1, the pickup end size is designed. To ensure the system lateral offset output power index, the transmitting coil width is set to 55 cm, and the number of turns is 5. Furthermore, the transmitting end compensation network adopts an LCC compensation network, including a primary compensation inductor, a primary parallel compensation capacitor, a first primary series compensation capacitor, and a second primary compensation capacitor. The distance between two adjacent transmitting coils is 5 cm.

[0026] Further, in step S6:

[0027] Considering the system output power, the length of the transmitting coil has a negative correlation with the mutual inductance between the transmitting coil and the receiving coil. min An upper limit on the length of the transmitting coil is determined.

[0028] Further, in step S6:

[0029] Considering the interoperability of the length of the transmitting coil for light vehicles and heavy vehicles, the upper limit of the length of the transmitting coil is further limited. It is required that the length of 4 times the transmitting coil is not greater than the maximum length of the light vehicle, and the length of 8 times the transmitting coil is not greater than the maximum length of the heavy vehicle. Here, the heavy vehicle is equipped with two pickup coils, and the corresponding two pickup coils are arranged along the length direction of the heavy vehicle, and the light vehicle is equipped with one pickup coil.

[0030] Further, in step S6:

[0031] Considering the impact on the magnetic field exposure time, and considering the interoperability of the two vehicles, The magnetic field exposure times t1 and t2 of the light vehicle and the heavy vehicle are estimated according to the different lengths of the transmitting coils, where l represents the length of the transmitting coil, v1 and v2 represent the driving speeds of the light vehicle and the heavy vehicle respectively, and ε represents the maximum allowed magnetic field exposure time. The length of the transmitting coil has a positive correlation with the magnetic field exposure time. Under the premise of meeting the output power, in order to shorten the magnetic field exposure time, the length of the transmitting coil is required to be as short as possible.

[0032] Further, in step S6:

[0033] Considering the road cost, Cost = Cost Litz +Cost Ferrite +Cost Pow +Cost Comp and The total cost of the transmitting coils required for the entire road is estimated based on the different lengths of the transmitting coils. R Cost is the cost of a group of transmitting units. Litz Cost is the cost of the Litz wire of the transmitting coil. Ferrite is the magnetic material cost of the transmitting coil, Cost Pow Cost is the power electronic module cost required for the transmitting coil. Comp is the compensation network cost required for the transmitting coil, and R is the length of the entire road. The length of the transmitting coil has a negative correlation with the cost. In order to obtain lower costs, within the upper limit of the length determined above, the length of the transmitting coil is required to be as long as possible. Under the premise of satisfying the system output power, the interoperability of the two vehicles, and the magnetic field exposure time, considering the lowest road cost, the length of the transmitting coil is set to 1.5m.

[0034] The present invention provides a dual-transmitting dual-pickup high-power electric vehicle dynamic wireless charging system, which adopts a dual-transmitting dual-pickup coupling mechanism to increase the power level, and only uses one inverter to activate two transmitting coils to reduce costs. In order to improve the adaptability of the pickup device to the vehicle, the present invention integrates a unipolar coil as a compensation inductor in the pickup coil, integrates the resonant network with the pickup coil, and the structure of the pickup end is more compact; by using the segmented compensation method of the pickup coil, the port voltage is reduced to meet the voltage limit of the vehicle-mounted equipment. The present invention also provides a parameter design method for the transmitting coil, considering the exposure time of the magnetic field in the dynamic process, and on the premise of meeting the power level, the length of the transmitting coil can meet the two power levels of single-pickup electric vehicles and dual-pickup electric buses, thereby improving the interoperability of the system. The system operates at 85kHz, the power transmission distance is 18cm, and when the transmission power is 62kW, the DC / DC efficiency reaches 87%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a general framework diagram of the EV-DWPT system provided by an embodiment of the present invention;

[0036] Figure 2 It is a block diagram of the working principle of the segmented coil of the double-transmitting and double-picking EV-DPWT system provided by an embodiment of the present invention;

[0037] Figure 3 is a DTDP topology diagram of dual inverter drive provided by an embodiment of the present invention;

[0038] Figure 4 is an equivalent circuit diagram of a DTDP system provided by an embodiment of the present invention;

[0039] Figure 5 The conventional capacitance compensation diagram (a) and the segmented capacitance compensation diagram (b) provided by the embodiments of the present invention;

[0040] Figure 6 is a first cross-sectional schematic diagram of a vehicle-mounted pickup terminal provided by an embodiment of the present invention;

[0041] Figure 7 is a second cross-sectional schematic diagram of a vehicle-mounted pickup end provided by an embodiment of the present invention;

[0042] Figure 8 1 is a top view (a) and a cross-sectional view (b) of a transmitting coil structure provided by an embodiment of the present invention;

[0043] Fig. 9 is a graph showing changes in mutual inductance and self-inductance for different transmitting coil lengths provided by an embodiment of the present invention;

[0044] Fig.10is a graph showing the change in cost of a single charging unit and the overall cost of a road for different transmitting coil lengths provided by an embodiment of the present invention;

[0045] Fig.11 is a block diagram of the working principle of an embodiment of the present invention applied to a light vehicle;

[0046] Fig.12 is a magnetic field distribution diagram of the coupling mechanism provided by an embodiment of the present invention;

[0047] Fig.13 is a diagram of mutual inductance variation of a coupling mechanism provided by an embodiment of the present invention;

[0048] Fig.14 is a system static test diagram provided by an embodiment of the present invention;

[0049] Fig.15 It is an experimental waveform diagram of a single inverter running on a segmented coil provided by an embodiment of the present invention;

[0050] Fig.16 It is an experimental waveform diagram of a single inverter output waveform at different positions of a receiving end provided by an embodiment of the present invention;

[0051] Fig.17 This is an output waveform diagram of five power units provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0053] The embodiment of the present invention provides a dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system (abbreviated as EV-DWPT system). The configuration of the EV-DWPT system is as follows: Figure 1 As shown. The EV-DWPT system includes a transmitter and a receiver. The transmitter includes multiple power units. Each power unit includes two parallel transmitting coils. The two transmitting coils are each connected to the corresponding transmitter compensation network and then connected to the same high-frequency inverter. All transmitting coils are evenly arranged at equal distances along the road direction. The receiving end includes two pickup ends. Each pickup end includes a pickup coil and a receiving compensation network and a rectifier circuit connected to the rear stage. At the transmitter, the 50Hz 380V AC grid voltage is converted into a 650V DC voltage as the power supply for all high-frequency inverters. The corresponding compensation network of each inverter and the transmitting coil is installed in the inverter box. The transmitting coil is installed under the ground and operates at 85kHz in accordance with the provisions of the SAE J2954 standard.

[0054] The receiving end compensation network adopts an LCC compensation network, including a pickup end compensation inductor, a pickup end parallel compensation capacitor and a pickup end series compensation capacitor. The transmitting end compensation network adopts an LCC compensation network, including a primary side compensation inductor, a primary side parallel compensation capacitor, a first primary side series compensation capacitor and a second primary side compensation capacitor.

[0055] In order to allow electric vehicles, especially heavy vehicles such as electric buses, to pick up high-power electrical energy, the present invention needs to design the parameters of the transmitting coil and the picking-up coil separately. The design steps are as follows:

[0056] S1. Determine the length, width and number of turns of the pickup coil and the distance between the two pickup coils according to the space limitation of the electric vehicle in vehicle modification;

[0057] S2. Determine the width, number of turns and winding area width of the transmitting coil according to the pickup coil designed in step S1;

[0058] S3. According to experience and actual needs, the distance between two adjacent transmitting coils should not exceed 10 cm.

[0059] S4. Determine the system output power P according to actual needs out and the maximum current I of the transmitting coil ti ;

[0060] S5. According to Calculate the minimum mutual inductance M between the transmitting coil and the pickup coil min , ω represents the operating angular frequency of the system, L r is the self-inductance of the pickup coil, Q is the load quality factor of the receiving end;

[0061] S6, at minimum mutual inductance M min Under the limitation of , the length of the transmitting coil is determined according to actual needs by comprehensively considering the impact of the length of the transmitting coil on the self-inductance of the transmitting coil, the mutual inductance between the transmitting coil and the pickup coil, the cost, the magnetic field exposure time, and the interoperability of heavy vehicles and light vehicles.

[0062] In step S6:

[0063] Considering the system output power, the length of the transmitting coil has a negative correlation with the mutual inductance between the transmitting coil and the receiving coil. min An upper limit on the length of the transmitting coil is determined.

[0064] Considering the interoperability between light vehicles and heavy vehicles, the upper limit of the length of the transmitting coil is further limited. It is required that the length of 4 times the transmitting coil is not greater than the maximum length of the light vehicle, and the length of 8 times the transmitting coil is not greater than the maximum length of the heavy vehicle. Here, the heavy vehicle is equipped with two pickup coils, and the corresponding two pickup coils are arranged along the length direction of the heavy vehicle, and the light vehicle is equipped with one pickup coil.

[0065] Considering the impact on the magnetic field exposure time, and considering the interoperability of the two vehicles, The magnetic field exposure times t1 and t2 of the light vehicle and the heavy vehicle are estimated according to the different lengths of the transmitting coil, where l represents the length of the transmitting coil, v1 and v2 represent the driving speeds of the light vehicle and the heavy vehicle respectively, and ε represents the maximum allowed magnetic field exposure time. The length of the transmitting coil has a positive correlation with the magnetic field exposure time. Under the premise of meeting the output power, in order to shorten the magnetic field exposure time, the length of the transmitting coil is required to be as short as possible.

[0066] Considering the road cost, Cost = Cost Litz +Cost Ferrite +Cost Pow +Cost Comp and The total cost of the transmitting coils required for the entire road is estimated based on the different lengths of the transmitting coils. R Cost is the cost of a group of transmitting units. Litz Cost is the cost of the Litz wire of the transmitting coil. Ferrite is the magnetic material cost of the transmitting coil, Cost Pow Cost is the power electronic module cost required for the transmitting coil. Comp is the compensation network cost required for the transmitting coil, and R is the length of the entire road. The length of the transmitting coil has a negative correlation with the cost. In order to obtain lower costs, within the upper limit of the length determined above, the length of the transmitting coil is required to be as long as possible. Under the premise of satisfying the system output power, the interoperability of the two vehicles, and the magnetic field exposure time, considering the lowest road cost, the length of the transmitting coil is set to 1.5m.

[0067] During the movement of the electric vehicle, the transmitting coil below the pickup coil is always powered, and the other transmitting coils are powered off. The two transmitting coils activated by one high-frequency inverter are called power units; A and B are used to distinguish the two transmitting coils. Along the moving direction of the electric bus, when the bus is in position 1, the two pickup coils can achieve 30kW respectively, mainly provided by transmitting coils 2A and 3A, while 2B and 3B are in a light load state. Similarly, in position 2, a single pickup coil is still powered by a high-frequency inverter, and the state of transmitting coil B alternates with the state of transmitting coil A. In position 3, the pickup end is located in the middle of the two transmitting coils 2B and 3A, which are powered by the second and third inverters. The segmented coil switching process during the movement of the electric bus is as shown in the figure. Figure 2 As shown, during the entire movement process, there will be two situations where one inverter alone or two inverters simultaneously supply power to a single pickup coil.

[0068] In this paper, a case where an inverter supplies power to a single pickup is selected for modeling. The topology of two adjacent power units is as follows: Figure 3 As shown. This paper uses a full-bridge inverter, and each of the two transmitting coils is connected to a separate compensation network. The LCC compensation network is used at the transmitting end, including the primary compensation inductor L fi , primary parallel compensation capacitor C ei And the first primary compensation capacitor C ti , i=1,2,3,4. In order to improve the filtering effect and suppress the high-order harmonics of the inverter current and the transmitting coil current, a compensation capacitor C is added on the basis of the LCC compensation network. fi With compensation inductance L fi The pickup end also uses an LCC compensation network, including the pickup end compensation inductor L sj , parallel compensation capacitor C at the pickup end sj And the compensation capacitor C in series with the pickup end rj , j = 1, 2. In the following, in order to simplify the analysis, the internal resistance of all inductors and capacitors is neglected.

[0069] Transmitter coil L ti and pickup coil L rj Mutual inductance M tirj Affects the power transmission during vehicle movement, the mutual inductance M between the integrated inductor and the pickup coil rsj It will also affect the output power, so the equivalent circuit of the DTDP system structure can be obtained as follows Figure 4 shown.

[0070] In order to simplify the analysis, it is assumed that the system parameters are consistent.

[0071]

[0072] The fundamental voltage phasor of the inverter can be expressed as:

[0073]

[0074] U dc Represents the 650V DC voltage supplied to the high frequency inverter.

[0075] The equivalent self-inductance of several groups of compensation devices on the transmitter and the pickup coil can be written as:

[0076]

[0077] Considering only the fundamental components of voltage and current, the equivalent resistance can be expressed as:

[0078]

[0079] The circuit resonance parameters can be expressed as:

[0080] ω 2 L t′ C e =ω 2 L f′ C e =ω 2 L r′ C s =ω 2 L s C s =1 (5)

[0081] By substituting (5) into the impedance equation, the impedance of the pickup end can be derived as:

[0082]

[0083] From (6), we can see that M rs It only increases the impedance of the pickup and does not affect the resonant characteristics of the pickup. For one of the pickups, apply Kirchhoff's law to Figure 4 The model in , the following equation can be easily obtained:

[0084]

[0085] in,

[0086]

[0087] For the transmitter, the transmitting coil current and inverter current can be obtained:

[0088]

[0089]

[0090] For the pickup end, it can be deduced that:

[0091]

[0092] Combining equations (10) and (11), we get:

[0093]

[0094] The input power of the DTDP system can be expressed as:

[0095]

[0096] The output power of the DTDP system can be expressed as:

[0097]

[0098] The pickup end is mainly composed of a ferrite core, a pickup cable (pickup coil), compensation capacitors (pickup end series compensation capacitors and pickup end parallel compensation capacitors), integrated inductors (pickup end compensation inductors / unipolar coils) and a fiber reinforced plastic (FRP) shell. Due to space limitations in vehicle modification, the size of the pickup coil is set to 80cm*62cm, with a total of 9 turns.

[0099] In order to make the pickup more compact, the compensation inductor is integrated into the main system coil. rs It will only increase the pickup impedance without affecting the characteristics of the LCC-LCC topology. rs The principle is to make it as small as possible, increase the output current and achieve the required output power. The integrated inductor and the pickup coil share a magnetic core, which helps to dissipate heat. The size of the integrated inductor is 20cm*30cm, with a total of 5 turns. The integrated inductor is wound in parallel with two wires and is wound with the same specifications as the pickup coil. The parameters of the designed pickup coil and integrated inductor are 81μH and 12μH respectively, and the mutual inductance M between them is 20cm*30cm, with a total of 5 turns. rs It is 7.2μH.

[0100] This paper also uses segmented compensation to reduce the port voltage. This connection method is as follows Figure 5 Assume Figure 5 In (a), a current of 130A flows through the pickup coil, and the port voltage is close to 5.6kV, which is difficult to insulate. This method reduces the port voltage to 1.4kV, which is lower than the 4.5kV in the GB / T 39752-2021 standard. In addition, the pickup coil adopts a three-wire parallel winding method, and three thin wires are used instead of a single thick wire, which reduces the thickness of the pickup end.

[0101] The unipolar coil is integrated in the pickup coil as a compensation inductor, and its size is much smaller than the pickup coil. Therefore, the mutual inductance between the compensation inductor and the transmitting coil is much smaller than the mutual inductance between the transmitting coil and the pickup coil, so the impact on the system power is small. However, the unipolar integrated inductor is located in the center of the unipolar pickup coil, and a large amount of magnetic flux generated by the pickup coil flows into the unipolar integrated inductor, which cannot eliminate the coupling effect between the integrated inductor and the pickup coil.

[0102] The structure of the pickup end is as follows Figure 6 As shown in the figure, from the hierarchical point of view, it includes coils (including pickup coils and unipolar coils), magnetic cores, water-cooled aluminum plates (magnetic shielding), resonant networks and control devices from the upper layer to the lower layer. Figure 7 As shown, 1 and the four PCB boards parallel to it are compensation capacitor boards, 2 is a parallel capacitor board, 3 is a rectifier diode, 4 is an anti-backflow diode, 5 is a temperature sampling board, 6 is a filter capacitor board, 7 is a sealing coil groove, 8 is a DC output port, and the reserved holes on the aluminum plate are used for threading.

[0103] Figure 8 The structure of the transmitting coil is shown in Table 1. The width of the transmitting coil w is 55 cm, with 5 turns in total and a winding area width of 12 cm, which can meet the lateral misalignment (LTM) of 10 cm. Table 1 gives Figure 8 After setting the basic structure, the next important issue is the design of the coil length.

[0104] Table 1 Transmitting coil parameters

[0105]

[0106] In the DWPT system, ignoring the loss at the pickup end, the system transmission power is calculated as follows:

[0107]

[0108] Where ω is the operating angular frequency of the system, I ti is the effective value of the transmitting coil current, Q is the load quality factor at the pickup end, and its value is between 5 and 10, L r is the self-inductance of the pickup coil, M tirj is the mutual inductance between the transmitting coil and the pickup coil. The output power of the STSP system is set to 31 kW, and the maximum current limit of the transmitting coil is 90 A. According to equation (15), M is used to select the length of the transmitting coil. min It can be calculated as:

[0109]

[0110] First, determine the upper limit of the transmitting coil length based on the mutual inductance, and select Figure 8The structure shown was designed as a rectangular coil and then the length was swept individually in the finite element analysis (FEA) tool Maxwell. Fig. 9 The effect of the length on the self-inductance and mutual inductance of the transmitting coil is shown. According to equation (16) and Fig. 9 As a result, the length l should be chosen to be less than 2m.

[0111] Then, in order to improve the interoperability of the transmitter coil for heavy buses and light vehicles, the transmitter coil length is also designed considering light vehicles with STSP. When a light vehicle is powered by two power units, the total length of the four activated transmitter coils may exceed that of a light vehicle, such as Fig.11 As shown. Similarly, the total length of the 8 transmitting coils may exceed that of a heavy-duty passenger vehicle. This paper requires that the length of the 4-times transmitting coil is not greater than the maximum length of a light-duty vehicle (generally 6 meters, so l≤1.5m), and the length of the 8-times transmitting coil is not greater than the maximum length of a heavy-duty vehicle (generally 15 meters, so l≤1.875m). Here, the heavy-duty vehicle is equipped with two pickup ends, and the corresponding two pickup coils are arranged along the length direction of the heavy-duty vehicle, and the light-duty vehicle is equipped with one pickup end.

[0112] This paper also defines the magnetic field exposure time t as one of the reference indicators of the launch length l, and sets t within the maximum magnetic field exposure time ε at vehicle speeds v1 and v2. The specific formula can be expressed as:

[0113]

[0114] In this paper, the vehicle speed during the test is set to 10km / h. Obviously, the shorter l is, the shorter the magnetic field exposure time is.

[0115] The length of the transmitting coil is then limited by cost, taking into account the cost of the following four components: Coil Litz Wire (Cost Litz ), magnetic materials (ferrite, Cost Ferrite ), power electronics module (Cost Pow ) and compensation network (Cost Comp ). The cost of a set of transmitting units can be estimated as:

[0116]

[0117] Among them, Cost L is the cost per metre of conductor, Cost F is the cost of ferrite per cubic centimeter, Cost P is the cost of the power electronics module, and Cost C is the cost of the compensation network. The specific values ​​are shown in Table 2. R represents the length of the entire road section. Therefore, the total cost of the transmitting coil required for the entire road section is CostR :

[0118]

[0119] Table 2

[0120]

[0121] Fig.10 The cost of a single charging unit and the changes in the overall road cost for different transmitting coil lengths are shown. Fig.10 This shows that the longer the coil, the fewer power electronic modules are needed, and the road cost is higher. R The longer the coil, the lower the cost. Therefore, when the system power requirement is obtained, a longer coil should be selected to reduce the cost.

[0122] Finally, considering the exposure time of the magnetic field in the dynamic process, under the premise of meeting the power level and being applicable to both heavy-duty buses and light-duty vehicles, in order to save costs, 1.5m is selected as the length of the transmitting coil. The overall size of the transmitting coil is set to 150cm*55cm, the distance between two adjacent transmitting coils is 5cm, and the length of a group of transmitting coils is about 3.1m. The working principle block diagram applied to light vehicles is shown in the figure below. Fig.11 shown.

[0123] After designing the pickup coil and the transmitting coil, this example gives the magnetic field vector distribution diagram of the pickup coil directly above the transmitting coil, as shown in Fig.12 shown. Fig.12 It shows that in the rated power area, the energy channel composed of the transmitting and picking-up coils has a strong and stable alternating magnetic field. Fig.13 It is shown that the transmitting coil provides a relatively constant mutual inductance to the pickup end in the rated power region.

[0124] The system is tested in the rated power area. The experimental results are as follows: Fig.14 As shown, Fig.14 (a) represents the total output current and voltage of the system, Fig.14 (b) represents the output current of the two pickups. The system can achieve a maximum power output of 62kW after being connected in parallel, and Fig.14 (c) The experimental results of a single pickup end with an output power of 31 kW are also given.

[0125] Fig.15The experimental waveform of a single inverter with segmented coil operation is shown. The output current of the inverter is the total current of the transmitting coils 1A and 1B. During the entire operation, the transmitting coils 1A and 1B charge the pickup end in turn. And due to the characteristics of the LCC network, the coil current remains constant during the entire operation of the inverter, which shows that the magnetic field provided by the transmitting coil is relatively stable during the charging process.

[0126] Fig.16 The inverter output waveforms of the system at different receiver positions are given. During the entire process of the electric vehicle moving above the transmitting coil, the total inverter current lags behind the inverter voltage, indicating that the system is in weak inductive mode, which helps the system achieve soft switching.

[0127] In addition, this embodiment also records the output waveforms of the five power units, such as Fig.17 As shown. L ,i L ,i out1 , and i out2 They represent the output voltage, output current, output current of pickup terminal 1 and output current of pickup terminal 2 respectively. L is i out1 and i out2 The total current of the superposition. Under the clamping effect of the large-capacity battery, u L Maintained at 632V. During the entire process of the electric vehicle moving, due to Fig. 9 M shown tirj trend, which will lead to out1 and i out2 Fluctuation. Due to the position of the two pickup ends installed and the L is i out1 and i out2 The fact that the sum of L will always be greater than the maximum output current i of a single pickup terminal out1 or out2 , and can provide a maximum output voltage of 95A, which means that the system can reach a maximum output power of 60kW within the rated power area.

[0128] In summary, the embodiment of the present invention provides a dual-transmitting dual-pickup high-power electric vehicle dynamic wireless charging system, which adopts a dual-transmitting dual-pickup coupling mechanism to increase the power level, and only uses one inverter to activate two transmitting coils to reduce costs. In order to improve the adaptability of the pickup device to the vehicle, the present invention integrates a unipolar coil as a compensation inductor in the pickup coil, integrates the resonant network with the pickup coil, and the structure of the pickup end is more compact; by compensating the pickup coil in sections, the port voltage is reduced to meet the voltage limit of the vehicle-mounted equipment. The present invention also provides a parameter design method for the transmitting coil, considering the exposure time of the magnetic field in the dynamic process, and under the premise of meeting the power level and low cost, the length of the transmitting coil can meet the two power levels of single-pickup electric vehicles and dual-pickup electric buses, thereby improving the interoperability of the system. In order to verify the system performance, a 60kW DWPT system has been implemented and tested in a 54-meter-long dynamic charging path. The system operates at 85kHz and the power transmission distance is 18cm. When the transmission power is 62kW, the DC / DC efficiency reaches 87%.

[0129] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A dual-transmitting and dual-pickup high-power electric vehicle dynamic wireless charging system, comprising a transmitting end and a receiving end, characterized in that: The transmitting end includes a plurality of power units, each of which includes two transmitting coils arranged side by side, each of which is connected to a corresponding transmitting end compensation network and then to the same high-frequency inverter, and all the transmitting coils are evenly arranged at equal distances along the road direction; the receiving end includes two pickup ends, each of which includes a pickup coil and a receiving end compensation network and a rectifier circuit connected to the rear stage; During the movement of the electric vehicle, the transmitting coil under the pickup coil is always powered, and the other transmitting coils are powered off; The parameters of the transmitting coil and the pickup coil are designed using the following steps: S1. Determine the length, width and number of turns of the pickup coil and the distance between the two pickup coils according to the space limitation of the electric vehicle in vehicle modification; S2. Determine the width, number of turns and winding area width of the transmitting coil according to the pickup coil designed in step S1; S3. Determine, based on experience and actual needs, that the distance between two adjacent transmitting coils is no more than 10 cm; S4. Determine the system output power P according to actual needs out and the maximum current I of the transmitting coil ti ; S5. According to Calculate the minimum mutual inductance M between the transmitting coil and the pickup coil min，ω Indicates the operating angular frequency of the system, L r is the self-inductance of the pickup coil, Q is the load quality factor of the receiving end; S6, at the minimum mutual inductance M min Under the restriction of , the length of the transmitting coil is determined according to actual needs by comprehensively considering the influence of the length of the transmitting coil on the self-inductance of the transmitting coil, the mutual inductance between the transmitting coil and the pickup coil, the cost, the magnetic field exposure time, and the interoperability of heavy vehicles and light vehicles.

2. According to claim 1, a dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system is characterized in that: In step S6: The length of the transmitting coil has a negative correlation with the self-inductance between the transmitting coil and the receiving coil. min An upper limit on the length of the transmitting coil is determined.

3. According to claim 2, a dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system is characterized in that: In step S6: The upper limit of the length of the transmitting coil is limited to require that 4 times the length of the transmitting coil is not greater than the maximum length of the light vehicle, and 8 times the length of the transmitting coil is not greater than the maximum length of the heavy vehicle. Here, the heavy vehicle is equipped with two pickup coils, and the corresponding two pickup coils are arranged along the length direction of the heavy vehicle, and the light vehicle is equipped with one pickup coil.

4. According to claim 3, a dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system is characterized in that: In step S6: pass Estimate the magnetic field exposure time t1 and t2 of the light vehicle and the heavy vehicle according to the different lengths of the transmitting coil, l represents the length of the transmitting coil, v1 and v2 represent the driving speeds of the light vehicle and the heavy vehicle respectively, and ε represents the maximum allowed magnetic field exposure time; The length of the transmitting coil has a positive correlation with the magnetic field exposure time. Under the premise of satisfying the output power, in order to shorten the magnetic field exposure time, the length of the transmitting coil is required to be as short as possible.

5. A dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system according to claim 4, characterized in that: In step S6, Cost=Cost Litz +Cost Ferrite +Cost Pow +Cost Comp and The total cost of the transmitting coils required for the entire road is estimated based on the different lengths of the transmitting coils. R , Cost is the cost of a group of transmitting units, Cost Litz Cost is the cost of the Litz wire of the transmitting coil. Ferrite is the magnetic material cost of the transmitting coil, Cost Pow Cost is the power electronic module cost required for the transmitting coil. Comp is the compensation network cost required for the transmitting coil, and R is the length of the entire road; The length of the transmitting coil has a negative correlation with the cost. Therefore, the length of the transmitting coil is set correspondingly with the lowest road cost under the premise of satisfying the system output power, the interoperability of the two vehicles and the magnetic field exposure time.

6. A dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system according to any one of claims 1 to 5, characterized in that: In the step S1, considering the space limitation of vehicle modification, the size of the pickup coil is set to 80cm*62cm, the number of turns of the pickup coil is 9, and the distance between the two pickup coils is set to 2.8m; the receiving end compensation network adopts an LCC compensation network, including a pickup end compensation inductor, a pickup end parallel compensation capacitor and a pickup end series compensation capacitor.

7. A dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system according to claim 6, characterized in that: In the step S1, the pickup coil is wound in three parallel wires, and three thin wires are used instead of a single thick wire; the pickup end compensation inductor is integrated in the central blank area of ​​the pickup coil using a unipolar coil; the unipolar coil is wound in two parallel wires, and is wound with wires of the same specification as the pickup coil, has 5 turns, and its size is set to 30cm*20cm.

8. The dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system according to claim 6, characterized in that: In step S1, the pickup end series compensation capacitor adopts a segmented compensation method to reduce the port voltage of the pickup coil to 1.4kV; under the premise of meeting the space modification of the pickup end and the port voltage limit of the pickup coil, the size of the pickup end is designed to be 80cm×62cm×6cm.

9. A dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system according to claim 8, characterized in that: According to the size of the pickup end, in order to ensure the system's lateral offset output power index, the width of the transmitting coil is set to 55 cm, and the number of turns is 5; the distance between two adjacent transmitting coils is 5 cm.

10. The dual-transmitter and dual-pickup high-power electric vehicle dynamic wireless charging system according to claim 1, characterized in that: The transmitter compensation network adopts an LCC compensation network, which includes a primary compensation inductor, a primary parallel compensation capacitor, a first primary series compensation capacitor and a second primary compensation capacitor.

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