EV-DWPT system based on dynamic magnetic field control and output power control method

Abstract

The invention provides an EV-DWPT system based on dynamic magnetic field control and an output power control method. The EV-DWPT system and the output power control method are used for solving the problem of large output power fluctuation in an existing short guide rail dynamic wireless charging system. The system comprises a ground transmitting end and a vehicle-mounted receiving end, wherein the ground transmitting end comprises a plurality of power transmitting units and a power control unit which are arranged in sequence; the power control unit comprises a first detection module and a second detection module which are of the same structure, a voltage detection circuit used for collecting load induction current of the first detection module and the second detection module, and a current detection circuit used for collecting direct current input current of the power transmitting unit. The position estimation module is used for estimating the position of the vehicle-mounted receiving end according to the output of the voltage detection circuit and the current detection circuit; and the phase shift control module is used for controlling the output of the power transmitting unit according to the estimated position of the vehicle-mounted receiving end. The output of the power transmitting unit is controlled through the estimated position of the vehicle-mounted receiving end, and the stability of the system output power is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless power transmission, and particularly to an EV-DWPT system and output power control method based on dynamic magnetic field control. BACKGROUND

[0002] The dynamic wireless charging technology of electric vehicles can be divided into two types, dynamic wireless charging based on long guide rail and dynamic wireless charging based on short guide rail, according to the structure of the ground end transmitting device. The main difference is that the EV-DWPT system based on long guide rail has a ground end transmitting coil size much larger than the size of the vehicle, and the transmitting coil has a large inductance value, which limits the working frequency of the system, and the transmitting coil needs to be always powered on, which causes serious electromagnetic leakage. The EV-DWPT system based on short guide rail has a ground end transmitting coil array composed of a series of independently controllable short transmitting coils, and the size of a single transmitting coil is comparable to or shorter than the length of the vehicle. Only a small number of transmitting coils in the ground end transmitting coil array are in power supply state at each moment, which avoids excessive magnetic field exposure caused by power supply of non-coupled transmitting coils. It is also suitable for supplying power to multiple electric vehicles simultaneously, and has the advantages of flexibility, small electromagnetic pollution, high efficiency, etc., and is suitable for dynamic wireless charging scheme of electric vehicles.

[0003] However, the dynamic wireless charging system based on short guide rail has a small magnetic field range generated by a single powered transmitting coil, and the overall uniformity is not high. During the process of dynamic energy pickup of the vehicle-mounted end, the relative position between the transmitting coil and the receiving coil changes constantly, which leads to the change of the total coupling mutual inductance between them, and further leads to the instability of the system output power. Especially when the receiving coil is at the edge position of the powered transmitting coil, the receiving power will drop significantly or even be zero. The large power fluctuation makes the vehicle-mounted end unable to pick up the required electric energy, and on the other hand, makes the charging process of the battery extremely unstable, seriously reduces the life of the battery, and even damages the battery and reduces the safety.

[0004] The power fluctuation problem is one of the bottleneck problems in the segmented short rail EV-DWPT system, and it is of great significance to realize the stable output power of the EV-DWPT system to promote the development of the dynamic wireless charging technology of electric vehicles. In recent years, many research teams at home and abroad have conducted in-depth research on the power fluctuation problem existing in the segmented short rail EV-DWPT system, and have proposed a large number of research methods to solve the problem. These methods can be mainly divided into three aspects: 1. Through the design of the magnetic coupling mechanism to suppress the change of the coupling coefficient during relative motion. 2. Through the optimization of the compensation network to cope with the coupling coefficient fluctuation. 3. Application of the controller to dynamically adjust the system to make the output power stable. The characteristics of each research direction can be summarized as follows: 1. The advantage of the coupling mechanism design is to change the structure of the magnetic coupler from the essence, so that the coupling coefficient becomes stable. The disadvantage is that most of the improvements make the structure complex, reduce the universality, are difficult to construct, significantly increase the material consumption, and greatly increase the cost, which has an important influence on the promotion of the dynamic wireless charging system of electric vehicles. 2. The mixed compensation network design uses different topological characteristics to improve the output power fluctuation to a certain extent, but for the system, it increases the additional coupling coil, compensation network and control switch, and the system cost rises sharply, which is not conducive to the large-scale and commercialization of the dynamic wireless charging system of electric vehicles. 3. The vehicle-end control in the control strategy can conveniently monitor the output information and realize closed-loop control, and the control effect is good. However, the additional DC / DC conversion circuit increases the system cost and the weight of the vehicle-end, and the controllable rectification mode needs to realize phase synchronization before rectification, and the control algorithm is complex. In addition, for the high-power EV-DWPT system, the vehicle-end control may cause the vehicle-end power conversion module to bear high electrical stress and be easily damaged. SUMMARY

[0005] The purpose of the present application is to provide an EV-DWPT system based on dynamic magnetic field control and an output power control method. To solve the technical problems of large output power fluctuation and poor stability in the existing short rail dynamic wireless charging system.

[0006] An EV-DWPT system based on dynamic magnetic field control, comprising a ground transmitting end and a vehicle-mounted receiving end, the ground transmitting end comprising a plurality of power transmitting units and a power control unit arranged in sequence along the movement direction of the vehicle-mounted receiving end;

[0007] The power control unit comprises first and second detection modules with the same structure, a voltage detection circuit for collecting load-induced current of the first and second detection modules, a current detection circuit for collecting direct current input of the power transmitting unit, a position estimation module for estimating position of the vehicle-mounted receiving end according to output of the voltage detection circuit and the current detection circuit, and a phase shift control module for controlling output of the power transmitting unit according to the estimated position of the vehicle-mounted receiving end.

[0008] Optionally, the first and second detection modules each comprise the first detection module comprising a detection load, a first detection capacitor and a detection coil connected with each other.

[0009] Optionally, the power transmitting unit comprises a direct current power supply, an inverter, a primary side compensation circuit and a transmitting coil connected in sequence, and the transmitting coils are arranged along a movement direction of the vehicle-mounted receiving end in sequence.

[0010] The vehicle-mounted receiving end comprises a receiving coil, a secondary side compensation circuit, a rectification filter circuit and a battery load connected in sequence.

[0011] Optionally, the transmitting coil and the receiving coil are both planar Q-type coils.

[0012] Optionally, the detection coil is a planar DD-type coil.

[0013] The detection coils of the first and second detection modules are symmetrically arranged on both sides of the transmitting coil, and the detection coils of the first and second detection modules are arranged on the transmitting coil.

[0014] An output power control method of an EV-DWPT system based on dynamic magnetic field control, defining a movement direction of a vehicle-mounted receiving end as an X direction and a transverse direction as a Y direction, the vehicle-mounted receiving end being in uniform motion, for controlling the above-mentioned EV-DWPT system based on dynamic magnetic field control, the specific steps being:

[0015] S1: collecting system parameters and constructing a system model, simulating mutual inductance of the jth and (j+1)th transmitting coils and the receiving coil when the receiving coil is located at different X direction positions and Y direction offsets, and obtaining a mutual inductance database, wherein: j∈(1~(N-1)), N is the number of power transmitting units;

[0016] S2: collecting an initial position of the vehicle-mounted receiving end and direct current input current variation data of the first and second power transmitting units at the initial position, and calculating a movement speed v of the vehicle-mounted receiving end;

[0017] S3: calculating an X direction position of the receiving coil at time t according to the initial position of the vehicle-mounted receiving end and the movement speed v;

[0018] S4: Collecting output voltage of the first and second detection modules at time t, and calculating Y direction offset of the receiving coil at time t;

[0019] S5: According to X direction position and Y direction offset of the receiving coil at time t, obtaining mutual inductance of the i th and i+1 th transmitting coil and the receiving coil at time t from mutual inductance database;

[0020] S6: According to mutual inductance of the i th and i+1 th transmitting coil and the receiving coil at time t and position of the receiving coil, adjusting output current of the i th or i+1 th transmitting coil at time t;

[0021] S7: Let t=t+1, and return to step S3.

[0022] Optionally, the specific steps of step S2 are as follows:

[0023] S2.1: Controlling rated power output of the first and second power transmitting units at the initial position, and collecting change data of direct current input current of the first and second power transmitting units at the initial position respectively;

[0024] S2.2: Obtaining time of current zero point of the direct current input current of the first power transmitting unit and current equal point of the direct current input current of the first and second power transmitting units, and calculating time difference between the two points;

[0025] S2.3: According to system parameter simulation, obtaining interval between the current zero point and the current equal point, and according to the interval and the time difference between the two points, calculating movement speed of the vehicle-mounted receiving end.

[0026] Optionally, the steps of calculating Y direction offset of the receiving coil at time t in step S4 are as follows:

[0027] S4.1: According to system parameter simulation, obtaining mutual inductance of the first and second detection coils and the receiving coil at different Y direction offsets, and calculating ratio of the two mutual inductances to obtain offset mutual inductance database;

[0028] S4.2: Collecting output voltage of the first and second detection modules at time t, and calculating ratio of the two voltages, wherein the voltage ratio at time t is equal to mutual inductance ratio of the first and second detection coils at time t;

[0029] S4.3: According to the voltage ratio, obtaining Y direction offset of the receiving coil at time t from the offset mutual inductance database.

[0030] Optionally, the specific steps of adjusting output current of the i th or i+1 th transmitting coil in step S6 are as follows:

[0031] S6.1: judging whether the receiving coil enters the working area of the i+1th transmitting coil according to the position of the receiving coil: if not, the i th power transmitting unit is for adjusting power output, and the i+1th power transmitting unit is for rated power output; if yes, the i th power transmitting unit is for rated power output, and the i+1th power transmitting unit is for adjusting power output;

[0032] S6.2: setting a power adjusting constant C according to system parameters and power output requirements, so that:

[0033] M i ·I pi +M (i+1) ·I p(i+1) =C

[0034] In the formula, M i is the mutual inductance of the i th transmitting coil and the receiving coil, M (i+1) is the mutual inductance of the i+1th transmitting coil and the receiving coil, I pi and I p(i+1) are the output currents of the i th and i+1th transmitting coils respectively; through the above formula, the expected output current of the power transmitting unit for adjusting power output at t time is calculated;

[0035] S6.3: generating a control signal according to the expected output current to control the output of the inverter in the i th or i+1th power transmitting unit.

[0036] Due to the adoption of the above technical scheme, the application has the following advantages:

[0037] 1. The application realizes the detection of the X-direction position of the receiving coil through the current detection circuit and the detection of the Y-direction offset of the receiving coil through the first and second detection modules, and adjusts the output of the power transmitting unit according to the X-direction position and Y-direction offset of the receiving coil, so that the output power stability of the vehicle-mounted receiving end is high, and the efficiency of wireless charging and the service life of the system are improved.

[0038] 2. The application determines the current zero-crossing point and current equal point by analyzing the currents of adjacent power transmitting units, and calculates the movement speed of the vehicle-mounted receiving end through the two points, so as to realize the estimation of the X-direction position of the receiving coil, which has high estimation accuracy and is beneficial to the control of system power.

[0039] 3. The application reduces the difficulty of system control by controlling the adjacent transmitting coils to be respectively for rated power output and adjusting power output in the power adjustment process, and can meet the stable transmission of multiple power requirements by setting the power adjusting constant C.

[0040] Additional advantages, objects, and features of the application will be apparent from the following specification, taken in conjunction with the accompanying drawings. The above-mentioned and other advantages and features of the application will become more apparent and the application itself will be better understood by reference to the following description of the application taken in conjunction with the accompanying drawings, wherein: BRIEF DESCRIPTION OF DRAWINGS

[0041] The drawings accompanying the specification are included as part of, and are to be taken in conjunction with, the disclosure. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0042] Figure 1 The circuit diagram of the dual power transmitting unit and the vehicle-mounted receiving end of the present application.

[0043] Figure 2 The circuit diagram of the power transmitting unit, the power control unit and the vehicle-mounted receiving end of the present application.

[0044] Figure 3 The structural schematic diagram of the transmitting coil, the receiving coil and the detection coil of the present application.

[0045] Figure 4 The mutual inductance curve diagram of the receiving coil and the dual power transmitting unit during the movement of the receiving coil of the present application.

[0046] Figure 5 The mutual inductance curve diagram of the receiving coil and the two transmitting coils in the simulation of the present application.

[0047] Figure 6 The direct current input current curve diagram of the power transmitting unit simulation of the present application.

[0048] Figure 7 The mutual inductance curve diagram of the receiving coil and the transmitting coil under different offsets in the simulation of the present application.

[0049] Figure 8 The schematic diagram of the principle of the X-direction position estimation of the vehicle-mounted receiving end of the present application.

[0050] Figure 9 The working state schematic diagram of the transmitting coil with the change of the position of the receiving coil of the present application.

[0051] Figure 10 The output voltage curve diagram of the detection resistor under different y offsets of the present application.

[0052] Figure 11 The ratio curve diagram of the output voltage U of the detection resistor when the y offset is different in the present application. D1 / U D2

[0053] Figure 12 The load output current curve diagram of the vehicle-mounted receiving end of the present application when the speed is 10 m / s.

[0054] ​Figure 13 Load output current curve diagram when the speed of the vehicle-mounted receiving end of the application is 20 m / s.

[0055] Figure 14 Load output current curve diagram when the receiving coil of the application is offset y=5 cm.

[0056] Figure 15 Load output current curve diagram when the receiving coil of the application is offset y=8 cm.

[0057] Figure 16 Load output current curve diagram when the receiving coil of the application is offset y=10 cm. DETAILED DESCRIPTION

[0058] The application will be further described below in conjunction with the drawings and examples.

[0059] Example 1:

[0060] As shown in Figure 1 , Figure 2 and Figure 3 , an EV-DWPT system based on dynamic magnetic field control includes a ground transmitting end and a vehicle-mounted receiving end, the ground transmitting end includes a plurality of power transmitting units and a power control unit arranged in sequence along the movement direction of the vehicle-mounted receiving end;

[0061] The power transmitting unit includes a direct current power supply, an inverter, a primary side compensation circuit and a transmitting coil connected in sequence, and a plurality of transmitting coils are arranged in sequence along the movement direction of the vehicle-mounted receiving end.

[0062] The vehicle-mounted receiving end includes a receiving coil, a secondary side compensation circuit, a rectifier filter circuit and a battery load connected in sequence.

[0063] The power control unit includes first and second detection modules with the same structure, a voltage detection circuit for collecting the load induced current of the first and second detection modules, a current detection circuit for collecting the direct current input current of the power transmitting unit, a position estimation module for estimating the position of the vehicle-mounted receiving end according to the output of the voltage detection circuit and the current detection circuit, and a phase shift control module for controlling the output of the power transmitting unit according to the estimated position of the vehicle-mounted receiving end.

[0064] In this embodiment, as shown in Figure 1 , the output voltage of the first and second power transmitting units is U dc , the inverter includes a total of 4 MOSFET tubes Q1-Q4, the primary side compensation circuit is an LCC topology structure, the first primary compensation circuit includes a primary side compensation inductor L f1 , a primary side first compensation capacitor C f1 and a primary side second compensation capacitor Cp1 , the first transmitting coil is L p1 .

[0065] In the embodiment, as shown in Figure 1 , the receiving coil is Ls; the secondary side compensation circuit is an LCC topology structure, including a secondary side compensation inductor L fs , a secondary side first compensation capacitor C fs and a secondary side second compensation capacitor C s ; the arrangement filter circuit includes a filter capacitor C d , and a full-bridge rectifier composed of four diodes D1-D4; and the load battery is R L In the embodiment, the transmitting coil L pi and the receiving coil Ls are both planar Q-type coils, wherein i∈(1, N), and N is the number of power transmitting units.

[0066] In the embodiment, as shown in Figure 2 , the first detection module in the power control unit includes a detection load R D1 , a detection capacitor C D1 and a detection coil L D1 connected in sequence; the second detection module includes a detection load R D2 , a detection capacitor C D2 and a detection coil L D2 connected in sequence; and the detection coil L D1 and the detection coil L D2 are both planar DD-type coils.

[0067] In the embodiment, as shown in Figure 3 , the detection coil L D1 and the detection coil L D2 are symmetrically arranged on both sides of the transmitting coil L pi , and the detection coil L D1 and the detection coil L D2 are arranged on the transmitting coil L pi .

[0068] In the embodiment, the output power of the system is P o , and the output power can be expressed as:

[0069]

[0070] In the formula, I Lfs , U in are the output current and input voltage effective values, ω, L f , L fs are inherent parameters of the system, which do not change in the dynamic driving process of the electric vehicle, and the equivalent resistance R eqThe output power of the EV-DWPT system vehicle-mounted receiving end is determined by the battery of the electric vehicle, and only fluctuates with the sum of the mutual inductance and the product of the input voltage of each coil. After the system is determined, the fluctuations of the input voltages U in1 and U in2 are small and can be considered constant, and whether the output power changes is only related to the change of the mutual inductance M1 and M2.

[0071] In the EV-DWPT system based on the segmented short guide rail structure, the mutual inductance between the receiving coil and the transmitting coil will inevitably change as the vehicle travels. During the movement of the receiving coil along the X direction, due to the non-uniform magnetic field generated by the transmitting coil in space, especially the distortion of the magnetic field in the adjacent area between the two transmitting coils, the coupling mutual inductance between the primary and secondary coils changes, thereby affecting the stability of the output power. Taking the transmitting coil as a plane, without considering the offset of the receiving coil in the Z and Y axes, only the mutual inductance change during the movement of the receiving coil along the X direction is observed. The parameters of the transmitting coil and the receiving coil are set as shown in Table 1.

[0072] Table 1 Parameters of transmitting coil and receiving coil

[0073]

[0074] Through the above parameters, the mutual inductance curve is simulated as shown in Figure 4 M1 is the mutual inductance between the receiving coil Ls and the first transmitting coil L p1 , and M2 is the mutual inductance between the receiving coil Ls and the second transmitting coil L p2 . When the vehicle-mounted receiving coil is in the directly opposite area above the first transmitting coil L p1 , the receiving coil is mainly coupled with the first transmitting coil L p1 , and the coupling mutual inductance is stable, and the output power is relatively stable. When the receiving coil is in the transition position between the two transmitting coils, the coupling mutual inductance between the receiving coil and the transmitting coil rapidly decreases, resulting in a drop in the system output power. Assuming that the input voltages U in1 = U in2 = U in , the output power expression is:

[0075]

[0076] At this time, the output power is related to the mutual inductance and M1+M2, and it can be known from Figure 4 that the mutual inductance and M1+M2 in the transition area between the two transmitting coils drop greatly relative to the directly opposite area during the movement of the receiving coil, causing the output power fluctuation phenomenon during the travel of the electric vehicle.

[0077] Example 2:

[0078] An output power control method of an EV-DWPT system based on dynamic magnetic field control, defining the motion direction of the vehicle-mounted receiving end as X direction, the transverse direction as Y direction, and the vertical direction as Z direction, the vehicle-mounted receiving end being in uniform motion, for controlling the output power of the EV-DWPT system based on dynamic magnetic field control described in embodiment 1, the specific steps being:

[0079] S1: Collect system parameters and construct a system model, simulate the mutual inductance between the jth and j+1th transmitting coils and the receiving coil when the receiving coil is located at different X direction positions and Y direction offsets, and obtain a mutual inductance database, wherein: j∈(1~(N-1)), N is the number of power transmitting units;

[0080] In this embodiment, the parameters of the N power transmitting units are the same, so by simulating the mutual inductance between the jth and j+1th transmitting coils and the receiving coil, general mutual inductance data can be obtained.

[0081] S2: Collect the initial position of the vehicle-mounted receiving end, and the direct current input current change data of the 1st and 2nd power transmitting units at the initial position, and calculate the motion speed v of the vehicle-mounted receiving end; the specific steps being:

[0082] S2.1: Control the rated power output of the 1st and 2nd power transmitting units at the initial position, and collect the change data of the direct current input current of the 1st and 2nd power transmitting units at the initial position, respectively;

[0083] S2.2: Obtain the time of the current zero point of the direct current input current of the 1st power transmitting unit and the current equal point of the direct current input current of the 1st and 2nd power transmitting units, and calculate the time difference between the two points;

[0084] S2.3: Obtain the interval between the current zero point and the current equal point according to the system parameter simulation, and calculate the motion speed of the vehicle-mounted receiving end according to the interval and the time difference of the two points.

[0085] In this embodiment, the transmitting coil is laid under the road surface, and the receiving coil is installed under the chassis of the vehicle. The receiving coil and the transmitting coil have a fixed distance in the Z direction, that is, the Z direction of the receiving coil relative to the transmitting coil in space is unchanged. Therefore, to perceive the position of the vehicle-mounted receiving end in three-dimensional space from the ground transmitting end, it is sufficient to measure the two-dimensional coordinates of the receiving coil projected on the plane of the transmitting coil of the ground transmitting end. Nowadays, electric vehicles are developing rapidly, and intelligentization has become the core competitiveness of electric vehicles. The rich functions also bring us convenience. The cruise control function is also a relatively popular and mature function in our life. When the vehicle is driving on the road, the cruise control can make the vehicle maintain a constant speed on the road. In the application scenario of the electric vehicle dynamic wireless charging system, it is feasible for the electric vehicle to drive at a constant speed on the wireless power supply road surface. The electric vehicle dynamic wireless charging system can be simplified as a double-transmitting single-receiving model for analysis. The mutual inductance between the receiving coil and the transmitting coil in the relative motion process is analyzed by modeling the double-transmitting single-receiving coupling mechanism by using the finite element software COMSOL, and the parameters in Table 1 are adopted. The mutual inductance curves M1 and M2 between the receiving coil and the transmitting coil when the receiving coil passes through the two transmitting coils in sequence along the X direction are obtained as shown in Figure 5 .

[0086] It can be seen that the shapes of the mutual inductance curves M1 and M2 in Figure 5 are the same, only the spatial positions are different, which is the same as the structure of the two transmitting coils. Taking the M2 mutual inductance curve as an example, the mutual inductance change in the motion process of the receiving coil is analyzed. When the receiving coil drives from left to right through the second transmitting coil area, the mutual inductance M2 between the receiving coil and the second transmitting coil first has a negative coupling state, then gradually rises, and there is a coupling zero point during the period, and then rapidly rises to a mutual inductance interval with a larger and relatively stable value; the relatively stable interval in the middle of the M2 mutual inductance curve is that the receiving coil is in the area opposite to the transmitting coil, at this time the coupling is strong and stable; finally, the mutual inductance gradually decreases to negative, until it tends to zero, and the receiving coil drives away from the second transmitting coil. The change trend of the M1 mutual inductance curve is the same as that of the M2 mutual inductance curve.

[0087] Through Simulink simulation, it can be seen that the above characteristics make the DC input current of the second transmitting unit lower than the DC input current when the receiving coil drives into the area, as shown in Figure 6 . The transmitting unit of the ground transmitting end needs to be turned on in advance before the vehicle-mounted receiving end arrives, at this time it is in an idle state, and the DC input current of the transmitting unit is a fixed value, representing the loss when the system is idle. The value is related to the system parameters. In Figure 6In this circuit, the no-load DC input current is used as the reference line. As the receiving coil gradually enters the operating region of the second transmitting coil, the magnitude of the DC input current of the second transmitting unit gradually increases from less than the reference value to greater than the reference value, intersecting the reference line at a certain point. This intersection point corresponds to the coupling zero point in the mutual inductance curve. This intersection point is fixed and depends only on the coil structure; it is called the current zero-crossing point. Figure 6 Feature point 1).

[0088] Secondly, the DC input current curves of the first and second transmitting coils intersect at a point in the transition region of the transmitting coils. This intersection point is located in the middle of the two transmitting coils, and this position is fixed and only depends on the installation position of the transmitting coils. Figure 6 From the mutual inductance curve, we can see that at the midpoint between the two transmitting coils, M1 and M2 are equal. At this point, the currents in both transmitting coils are the same, simultaneously supplying power to the receiving coil. Therefore, the power consumed by the two transmitting units is the same, resulting in a DC input current I... dc1 and I dc2 When the magnitudes are equal, the intersection point is called the point of equal current. Figure 6 Feature point 2).

[0089] Therefore, by monitoring the DC input current curve at the ground transmitter, two position-dependent feature points can be extracted. The distance between these two feature points is fixed and depends only on the coupling mechanism structure. By timing the time it takes for the receiving coil to pass these two positions, the moving speed of the receiving coil can be calculated. In this application, the distance between the two feature points in the coupling mechanism is 16 cm. Furthermore, as... Figure 7 As shown, when the longitudinal offset y≠0cm, the zero-crossing points of the mutual inductance curves almost coincide, indicating that the longitudinal offset of the receiving coil does not affect this feature point. Furthermore, the mutual inductance of the two transmitting coils and the receiving coil is equal at the midpoint. As long as the coil currents are equal, the intersection of the DC currents will correspond to the midpoint. Therefore, the vehicle speed sensing method based on the feature point is stable.

[0090] S3: Calculate the position of the receiving coil in the X direction at time t based on the initial position and speed v of the vehicle-mounted receiver;

[0091] In this embodiment, when the receiving coil passes the transmitting coil of a ground transmitter at a constant speed, if the transmitting coil senses the instantaneous speed of the receiving coil at the moment it first enters, it can predict and estimate the relative position of the receiving coil and the transmitting coil in the direction of travel, i.e., the X-axis. For example... Figure 8As shown, the geometric midpoint of the receiving coil is M, when M is at position x0, the ground transmitting end measures the moving speed of the receiving coil as v0, and at the same time, the timer is started. It can be known that at time t1, the position of point M relative to the transmitting coil is x1=x0+v0(t1-t0). Based on this principle, the ground end can estimate the relative position of the vehicle-mounted receiving end in the X direction by sensing the speed of the vehicle-mounted receiving end.

[0092] S4: Collecting output voltages of the first and second detection modules at time t, and calculating the Y direction offset of the receiving coil at time t; the specific steps are as follows:

[0093] S4.1: Simulating the mutual inductance of the first and second detection coils and the receiving coil at different Y direction offsets according to system parameters, and calculating the ratio of the two mutual inductances to obtain a mutual inductance database of offsets;

[0094] S4.2: Collecting output voltages of the first and second detection modules at time t, and calculating the ratio of the two voltages, the voltage ratio at time t being equal to the mutual inductance ratio of the first and second detection coils at time t;

[0095] S4.3: Obtaining the Y direction offset of the receiving coil at time t from the mutual inductance database of offsets according to the voltage ratio.

[0096] In this embodiment, the mutual inductance of the transmitting coil and the receiving coil is measured by the detection coil. Figure 7 It can be known that the mutual inductance curve of the transmitting coil and the receiving coil changes greatly at different offsets. If the mutual inductance data at offset y=0 cm is used for current regulation, it can be effective for the case when the vehicle-mounted receiving end is offset by y=0 cm, but when the vehicle-mounted receiving end is offset in the Y direction, using this mutual inductance data for calculation will cause the output to be lower than the set value. Therefore, it is necessary to detect the Y direction offset state of the vehicle-mounted receiving end and use the corresponding mutual inductance curve data for calculation. In this embodiment, the offset state is divided into three intervals. When the Y direction offset y is in the interval of 0-5 cm, the mutual inductance curve data of offset y=5 cm is used for calculation; when the Y direction offset y is in the interval of 5-8 cm, the mutual inductance curve data of offset y=8 cm is used for calculation; and when the Y direction offset y is in the interval of 8-10 cm, the mutual inductance curve data of offset y=10 cm is used for calculation. This scheme is conducive to improving the output stability in the offset state, and also reduces the requirement for the sensing accuracy of the Y direction offset state. The parameters of the detection coil are shown in Table 2.

[0097] Table 2: Parameters of the detection coil

[0098]

[0099] In this embodiment, the transmitting coil and the receiving coil of the EV-DWPT system coupling mechanism for transmitting power are Q coils, the detection coil is a DD coil, and the detection coil, the transmitting coil and the receiving coil form a mutually decoupled DDQ coil, so that the detection coil LD1 and L D2 decoupled, the magnetic field generated by the transmitting coil will not induce an induced voltage in the detection coil. Similarly, assuming that the receiving coil has no Y-direction offset, moving along the X-direction, the receiving coil is also decoupled with the detection coil. When the receiving coil has a Y-direction offset, moving along the X-direction, the receiving coil and the detection coil L D1 and L D2 are no longer decoupled, the magnetic field generated by the receiving coil will induce an induced voltage in the detection coil. At the same time, due to the different positions of the two groups of DD coils, the sizes of the induced voltages are different, and the two induced voltages have certain characteristic relationship, which can represent the Y-direction offset state of the receiving coil. Therefore, the ratio of the effective values of the voltages on the two detection resistors is:

[0100]

[0101] From the above formula, it can be seen that the voltage ratio of the two detection resistors is only related to the mutual inductance M D1 and M D2 between the two detection coils and the receiving coil, respectively.

[0102] Therefore, by designing the detection coil, the mutual inductance multiple relationship can be used to reflect the Y-direction offset state of the receiving coil, and the characteristic is not affected by the X-direction offset of the receiving coil. When the detection coil has a Y-direction offset, the vehicle-mounted receiving end is regarded as the primary side, and the ground transmitting end is regarded as the secondary side. The detection resistors of the first and second detection modules have the same value. The ratio of the voltages on the two detection resistors is taken, and the controller obtains the longitudinal Y-direction offset state of the receiving coil according to the ratio.

[0103] S5: According to the X-direction position and Y-direction offset of the receiving coil at t time, the mutual inductance of the i th and i+1 th transmitting coils and the receiving coil at t time is obtained from the mutual inductance database;

[0104] S6: According to the mutual inductance values of the i th and i+1 th transmitting coils and the receiving coil at t time and the position of the receiving coil, the output current of the i th or i+1 th transmitting coil at t time is adjusted;

[0105] S6.1: According to the position of the receiving coil, it is judged whether the receiving coil enters the working area of the i+1 th transmitting coil: if not, the i th power transmitting unit is adjusted power output, and the i+1 th power transmitting unit is rated power output; if yes, the i th power transmitting unit is rated power output, and the i+1 th power transmitting unit is adjusted power output;

[0106] S6.2: According to the system parameters and power output demand, the power adjustment constant C is set, then:

[0107] M i ·Ipi +M (i+1) ·I p(i+1) =C

[0108] where M i is the mutual inductance between the i-th transmitting coil and the receiving coil, M (i+1) is the mutual inductance between the i+1-th transmitting coil and the receiving coil, I pi and I p(i+1) are the output currents of the i-th and i+1-th transmitting coils, respectively; through the above formula, the expected output current of the power transmitting unit at time t is calculated, which outputs the adjusted power;

[0109] S6.3: generating a control signal according to the expected output current, and controlling the output of the inverter in the i-th or i+1-th power transmitting unit.

[0110] In this embodiment, by controlling the adjacent transmitting coils to output the rated power and the adjusted power, respectively, during the power adjustment, the difficulty of system control is reduced, and by setting the power adjustment constant C, the stable transmission of multiple power requirements can be met. Specifically, as shown in FIG. 1, three transmitting coils are included, when the receiving coil moves to the latter half of the X direction of the 1# transmitting coil and to the former half of the X direction of the 2# transmitting coil, the 1# transmitting coil is defined as the i-th transmitting coil, and the 2# transmitting coil is defined as the i+1-th transmitting coil; when the receiving coil moves to the latter half of the X direction of the 2# transmitting coil, the 2# transmitting coil is defined as the i-th transmitting coil, and the 3# transmitting coil is defined as the i+1-th transmitting coil. Figure 9 In this embodiment, according to the output characteristics of the LCC topology, the size of the transmitting coil current is controlled by the inverter output voltage, and the adjustment of the inverter output voltage can be realized by adjusting the DC input voltage or changing the phase shift angle of the inverter. The application uses inverter phase shift control to adjust the coil current, without the need to increase additional DC-DC conversion circuit, reducing the system cost. In this embodiment, as known from the foregoing analysis in the transition area, the currents of different transmitting coils need to be kept in phase, so that the superimposed magnetic induction intensity is maximum. Due to the differences and different starting times of each inverter circuit, the driving pulse phases of the inverters of different transmitting units are different, which will cause the phases of the inverter voltages to be different, and further cause the phases of the transmitting coil currents to be different. Therefore, the driving pulse signals of the high-frequency inverter circuit need to be synchronized, and the application utilizes a signal source to generate multiple pulse signals, and transmits the pulse signals with the same frequency and phase to each ground end transmitting unit to realize synchronization.

[0111] S7: let t=t+1, and return to step S3.

[0112] S8: simulation verification: a system simulation model is constructed, and the parameters used by the simulation model are shown in Table 3.

[0113] ​

[0114] Figure 3 EV-DWPT system simulation model parameters

[0115]

[0116] S8.1: Simulation of Y-axis offset sensing based on detection coil: The current Y-axis offset state of the receiving coil can be obtained by collecting the output voltage on the two detection resistors and performing a division operation. Figure 10 This is a curve showing the effective value of the output voltage of the detection resistor under different offset conditions of the receiving coil. Figure 10 In (a), the offset y = 5cm, Figure 10 In (b), the offset y = 8cm, Figure 10 In (c), the offset y = 10cm. Figure 11 The graph shows the relationship between the output voltage multiple of the detection resistor under different offsets within the working area of ​​the transmitting coil. As can be seen from the graph, the multiple is approximately 4.1 when the offset y = 5cm, approximately 3.6 when the offset y = 8cm, and approximately 3.3 when the offset y = 10cm. This is the same as the relationship between the mutual inductance multiples between the two detection coils and the receiving coil under different offsets, thus verifying the effectiveness of the offset detection method.

[0117] S8.2: Simulation Analysis of System Output Power Stability: The EV-DWPT system of this application adopts an LCC-LCC topology, whose output current has the characteristic of being independent of the load. Since the battery load voltage remains constant, the stability of the output current reflects the stability of the output power. To test the effectiveness of the proposed control strategy, the system output at different speeds and at different offsets was tested.

[0118] First, when the Y-axis offset is y = 0 cm, the system response under test velocity changes is shown in the simulation results. Figure 12 and Figure 13 As shown. The simulation is a dual-transmitter, single-receiver model, with only the second power transmitting unit adjusting the power output. When the receiving coil moves to the working area of ​​the second transmitting coil at a speed of 10m / s or 20m / s, its controller takes control action, keeping the load current of the vehicle-mounted receiver basically stable around the set value of 29A, with an output current fluctuation rate of less than 3%. Figure 12 (b) and Figure 13 As shown in (b).

[0119] Then, the system output under longitudinal offset of the receiving coil was tested, and the simulation results are as follows: Figure 14 to Figure 16 As shown. Figure 14 and Figure 15 At offsets of y = 5cm, y = 8cm, and y = 10cm, respectively, the output current of the vehicle-mounted receiver within the operating area of ​​the second transmitting coil remained relatively stable around the set value of 29A, with an output current fluctuation rate of less than 3%.Figure 14 (b) and Figure 15 (b) as shown. Figure 16 For the offset y = 10 cm, the minimum output current of the transition zone in the middle of the transmitting coil is 27.6 A, which is slightly lower than the reference value, due to the excessive offset and the weak magnetic induction. As shown in Figure 16 (b) as shown, the overall output current fluctuation rate is still less than 5%, which meets the expectation. The experimental results show that the dynamic magnetic field control method of the EV-DWPT system proposed in the application has certain effectiveness for realizing the smooth output power.

[0120] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or replaced by the equivalent, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered within the protection scope of the claims of the present application.

Claims

1. An EV-DWPT system based on dynamic magnetic field control, comprising a ground transmitting end and a vehicle-mounted receiving end, characterized in that, The ground transmitting end comprises a plurality of power transmitting units and a power control unit arranged in sequence along the movement direction of the vehicle-mounted receiving end; The power control unit comprises first and second detection modules with the same structure, a voltage detection circuit for collecting the load-induced current of the first and second detection modules, a current detection circuit for collecting the direct current input current of the power transmitting units, a position estimation module for estimating the position of the vehicle-mounted receiving end according to the output of the voltage detection circuit and the current detection circuit, and a phase shift control module for controlling the output of the power transmitting units according to the estimated position of the vehicle-mounted receiving end.

2. The EV-DWPT system based on dynamic magnetic field control according to claim 1, wherein, The first and second detection modules each comprise a detection load, a first detection capacitor and a detection coil connected to each other.

3. The EV-DWPT system based on dynamic magnetic field control according to claim 2, wherein, The power transmitting unit comprises a direct current power supply, an inverter, a primary side compensation circuit and a transmitting coil connected in sequence, and a plurality of transmitting coils arranged in sequence along the movement direction of the vehicle-mounted receiving end. The vehicle-mounted receiving end comprises a receiving coil, a secondary side compensation circuit, a rectification filter circuit and a battery load connected in sequence.

4. The EV-DWPT system based on dynamic magnetic field control according to claim 3, wherein, The transmitting coil and the receiving coil are both planar Q-type coils.

5. The EV-DWPT system based on dynamic magnetic field control according to claim 3, wherein, The detection coil is a planar DD-type coil. The detection coils of the first and second detection modules are symmetrically arranged on both sides of the transmitting coil, and the detection coils of the first and second detection modules are arranged on the transmitting coil.

6. A method for controlling the output power of an EV-DWPT system based on dynamic magnetic field control, defining the motion direction of the vehicle-mounted receiving end as the X direction and the transverse direction as the Y direction, and the vehicle-mounted receiving end as uniform motion, characterized in that, The steps for controlling the dynamic magnetic field control-based EV-DWPT system of any one of claims 1-5 are as follows: S1: Collect system parameters and build a system model. Simulate the mutual inductance between the jth and (j+1)th transmitting coils and the receiving coil when the receiving coil is located at different X-direction positions and Y-direction offsets, and obtain a mutual inductance database, where j ∈ (1~(N-1)), and N is the number of power transmitting units. S2: Collect the initial position of the vehicle-mounted receiving end and the direct current input current variation data of the first and second power transmitting units at the initial position, and calculate the movement speed v of the vehicle-mounted receiving end. S3: Calculate the X-direction position of the receiving coil at time t according to the initial position and the movement speed v of the vehicle-mounted receiving end. S4: Collect the output voltages of the first and second detection modules at time t, and calculate the Y-direction offset of the receiving coil at time t. S5: Obtain the mutual inductance between the ith and (i+1)th transmitting coils and the receiving coil at time t according to the X-direction position and Y-direction offset of the receiving coil at time t. S6: Adjust the output current of the ith or (i+1)th transmitting coil at time t according to the mutual inductance between the ith and (i+1)th transmitting coils and the receiving coil at time t and the position of the receiving coil. S7: Let t = t+1 and return to step S3.

7. The output power control method of the EV-DWPT system based on dynamic magnetic field control according to claim 6, wherein, The specific steps of step S2 are as follows: S2.1: Control the rated power output of the first and second power transmitting units at the initial position, and collect the variation data of the direct current input current of the first and second power transmitting units at the initial position, respectively. S2.2: Obtain the time of the current zero point of the direct current input current of the first power transmitting unit and the current equal point of the direct current input current of the first and second power transmitting units, and calculate the time difference between the two points. S2.3: According to the system parameters simulation, the interval between the current zero-crossing point and the current equal point is obtained, and according to the interval and the time difference of the two points, the motion speed of the vehicle-mounted receiving end is calculated.

8. The output power control method of the EV-DWPT system based on dynamic magnetic field control according to claim 6, wherein, The step of calculating the Y direction offset of the receiving coil at time t in step S4 is: S4.1: According to the system parameters simulation, the mutual inductance of the first and second detection coils and the receiving coil at different Y direction offsets is calculated, and the ratio of the two mutual inductances is obtained to obtain the offset mutual inductance database; S4.2: The output voltages of the first and second detection modules at time t are collected, and the ratio of the two voltages is calculated, which is equal to the ratio of the mutual inductances of the first and second detection coils at time t; S4.3: According to the voltage ratio, the Y direction offset of the receiving coil at time t is obtained from the offset mutual inductance database.

9. The output power control method of the EV-DWPT system based on dynamic magnetic field control according to claim 6, wherein, The specific steps of adjusting the output current of the i-th or i+1-th transmitting coil in step S6 are: S6.1: According to the position of the receiving coil, it is judged whether the receiving coil enters the working area of the i+1-th transmitting coil: if not, the i-th power transmitting unit is adjusted power output, and the i+1-th power transmitting unit is rated power output; if yes, the i-th power transmitting unit is rated power output, and the i+1-th power transmitting unit is adjusted power output; S6.2: According to the system parameters and power output demand, set the power adjustment constant C, then: M i • I pi + M (i+1) • I p(i+1) = C where M i is the mutual inductance of the ith transmit coil and receive coil, M (i+1) is the mutual inductance of the ith+1 transmit coil and receive coil, I pi and I p(i+1) are the output currents of the ith and ith+1 transmit coils, respectively; by the above equations, the expected output current of the power transmitting unit at time t is calculated, which adjusts the power output. S6.3: According to the expected output current, generate a control signal to control the output of the inverter in the i-th or i+1-th power transmitting unit.

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