Rapid current starting control method for transmitting coil of dynamic wireless power supply system

Abstract

The invention relates to the technical field of wireless power supply, and particularly discloses a dynamic wireless power supply system transmitting coil current quick start control method, which comprises the following steps: establishing a differential equation of a transmitting coil resonance circuit; determining a state variable influencing the current of the transmitting coil, and solving the differential equation to obtain a time domain expression of the state variable; performing normalization processing on the time domain expression of the state variable to obtain a differential equation of a normalized state variable; according to the differential equation of the normalized state variable, solving a trajectory equation of the normalized state variable in different inverter output states; determining a steady-state track of the normalized state variable according to the track equation, and determining an initial starting point of the starting track according to the steady-state track; designing a starting track from the initial starting state point to the steady-state track; and calculating an inverter pulse sequence for realizing the starting track. According to the invention, the current of the transmitting coil can be started from an initial value to a rated value within 1-2 periods, and overshoot and oscillation are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power supply, and in particular to a method for quickly starting and controlling a current of a transmitting coil of a dynamic wireless power supply system. Background Art

[0002] The wireless power supply system uses the principle of high-frequency electromagnetic field near-field coupling, uses high-frequency magnetic field as the transmission medium, and realizes wireless transmission of electric energy through magnetic field coupling between the transmitting coil and the receiving coil. The common two-coil wireless power supply system mainly consists of two parts, one is the transmitting end connected to the power supply side, and the other is the receiving end located on the load side. The energy is transmitted from the transmitting end to the receiving end by electromagnetic induction. The dynamic wireless power supply system can be used to dynamically charge electrified transportation vehicles, thereby reducing the parking and charging time of transportation vehicles and improving transportation efficiency.

[0003] Normally, in order to reduce the loss of the transmitting coil in the dynamic wireless power supply system, the transmitting coil needs to be powered in sections. When the receiving coil moves to the vicinity of a certain section of the transmitting coil, the transmitting coil of that section starts working; when the receiving coil moves away from a certain section of the transmitting coil, the transmitting coil of that section should be turned off.

[0004] The segmented transmitting coil needs to start and establish a stable, rated transmitting coil current before the receiving coil arrives. The longer the transmitting coil takes to start and establish the rated current, the lower the receiving coil movement speed it can adapt to; the longer the transmitting coil needs to start in advance, the greater the loss of the transmitting coil startup process. If there is no good control during the startup process, there will be problems such as overshoot and oscillation of the transmitting coil current. Therefore, how to achieve fast startup of the segmented transmitting coil without overshoot and oscillation is a key issue. Summary of the invention

[0005] The present invention provides a dynamic wireless power supply system transmitting coil current rapid start control method, which solves the technical problem of how to achieve rapid start of segmented transmitting coils without overshoot and oscillation.

[0006] In order to solve the above technical problems, the present invention provides a method for quickly starting the current of a transmitting coil of a dynamic wireless power supply system, comprising the steps of:

[0007] S1. Establishing a differential equation of a transmitting coil resonant circuit of a dynamic wireless power supply system, wherein the transmitting coil resonant circuit is connected to an inverter at the front stage;

[0008] S2. Determine the state variables that affect the current of the transmitting coil, and solve the differential equation to obtain the time domain expression of the state variables;

[0009] S3, normalizing the time domain expression of the state variable to obtain a differential equation of the normalized state variable after the state variable is normalized;

[0010] S4. According to the differential equation of the normalized state variable, finding the trajectory equation of the normalized state variable under different inverter output states;

[0011] S5, determining a steady-state trajectory of the normalized state variable according to the trajectory equation, and determining an initial starting point of the starting trajectory according to the steady-state trajectory;

[0012] S6, designing a starting trajectory from the initial starting state point to a steady-state trajectory;

[0013] S7. Calculate an inverter pulse sequence for realizing the startup trajectory according to the output mode of the inverter.

[0014] Furthermore, in step S2, after solving the differential equation, the initial value of the state variable and the DC voltage V input to the inverter are obtained. in , the characteristic impedance Z0 of the transmitter resonant circuit and the characteristic frequency ω of the transmitter resonant circuit r The time domain expression of the state variables.

[0015] Furthermore, in step S3, based on the DC voltage V in The time domain expression of the state variable is normalized by the characteristic impedance Z0.

[0016] Furthermore, in step S4, by transforming the differential equation of the normalized state variable, a trajectory equation including only the normalized state variable and the initial value of the normalized state variable is obtained.

[0017] Furthermore, in step S4, when obtaining the trajectory equation, the two cases of positive and negative inverter outputs are distinguished and the corresponding trajectory equations are determined respectively.

[0018] Further, in step S5, the trajectory equation established in step S4 is used to draw a corresponding trajectory with the normalized state variable as the coordinate axis to obtain the steady-state trajectory of the normalized state variable.

[0019] Further, in step S5, the initial starting point is an initial value of the normalized state variable corresponding to time zero of the inverter in the coordinate system of the normalized state variable.

[0020] Furthermore, step S6 specifically includes the steps of:

[0021] S61, determining the center positions of multiple arcs according to the center of the trajectory equation;

[0022] S62. Taking the center position of the circle as the center of the circle, design multiple connected arcs in the space of the steady-state trajectory to obtain a starting trajectory. The starting trajectory starts from the initial starting point and ends on the steady-state trajectory.

[0023] Furthermore, the step S7 specifically includes the steps of:

[0024] S71, determining multiple central angles corresponding to the multiple arcs according to the designed multiple arcs;

[0025] S72. Calculate the voltage pulse width time of the inverter corresponding to the multiple arcs in one cycle according to the multiple center angles corresponding to the multiple arcs, so as to obtain the inverter startup pulse sequence corresponding to the startup trajectory.

[0026] Furthermore, in step S72, based on the multiple central angles corresponding to the multiple arcs, the voltage pulse width times of the multiple stages of the inverter corresponding to the multiple arcs are calculated by dividing the central angle by π and then multiplying by the cycle time, and the cycle time is a cycle time corresponding to the characteristic frequency of the transmitting end resonant circuit.

[0027] The present invention also provides a dynamic wireless power supply system transmitting coil current rapid start control system, the key of which is: comprising a processing unit, the processing unit is used to implement the above-mentioned dynamic wireless power supply system transmitting coil current rapid start control method.

[0028] The present invention provides a method for quickly starting the transmitting coil current of a dynamic wireless power supply system, the method comprising establishing a differential equation of a transmitting coil resonant circuit of a dynamic wireless power supply system; determining the state variables that affect the transmitting coil current, solving the differential equation to obtain a time domain expression of the state variable; normalizing the time domain expression of the state variable to obtain a differential equation of the normalized state variable; according to the differential equation of the normalized state variable, obtaining a trajectory equation of the normalized state variable under different inverter output states; determining the steady-state trajectory of the normalized state variable according to the trajectory equation, and determining the initial starting point of the starting trajectory according to the steady-state trajectory; designing the starting trajectory from the initial starting state point to the steady-state trajectory; and calculating the inverter pulse sequence that realizes the starting trajectory according to the output mode of the inverter. The present invention can realize the starting of the transmitting coil current from the initial value to the rated value within 1-2 cycles without overshoot and oscillation, solving the problem of long starting time and possible overshoot of the traditional starting control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a circuit diagram of an LCL type transmitting coil resonant circuit provided by an embodiment of the present invention;

[0030] Figure 2 is a diagram of a steady-state trajectory and a startup trajectory obtained by the theory provided in an embodiment of the present invention;

[0031] Figure 3 is a start-up pulse sequence diagram of an inverter provided by an embodiment of the present invention;

[0032] Figure 4 is a transient waveform diagram of the transmitting coil current provided by an embodiment of the present invention;

[0033] Figure 5 It is a steady-state trajectory and a startup trajectory diagram obtained by actual measurement provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] The embodiment of the present invention provides a method for quickly starting the current of a transmitting coil of a dynamic wireless power supply system, comprising the steps of:

[0036] S1. Establish the differential equation of the transmitting coil resonant circuit of the dynamic wireless power supply system;

[0037] S2. Determine the state variables that affect the current of the transmitting coil, and solve the differential equation to obtain the time domain expression of the state variables;

[0038] S3, normalizing the time domain expression of the state variable to obtain a differential equation of the normalized state variable after the state variable is normalized;

[0039] S4. According to the differential equation of the normalized state variable, the trajectory equation of the normalized state variable under different inverter output states is obtained;

[0040] S5. Determine a steady-state trajectory of the normalized state variable according to the trajectory equation, and determine an initial starting point of the starting trajectory according to the steady-state trajectory;

[0041] S6. Design a starting trajectory from the initial starting state point to a steady-state trajectory;

[0042] S7. Calculate the inverter pulse sequence that realizes the startup trajectory according to the output mode of the inverter.

[0043] The fast start-up control method can realize the start-up of the transmitting coil current from the initial value to the rated value within 1-2 cycles without overshoot and oscillation, thus solving the problem of long start-up time and possible overshoot in the traditional start-up control method.

[0044] In step S1, the transmitting coil resonant circuit of the dynamic wireless power supply system includes but is not limited to the commonly used LCL type, LCC type, and S type. For different transmitting coil resonant circuits, the same control steps are adopted. This example takes the LCL type as an example for explanation.

[0045] LCL type transmitting coil resonant circuit Figure 1 As shown, it includes a transmitting coil L P , and the transmitting coil L P The series resonant inductor L r , and the transmitting coil L P Parallel resonant capacitor C P , the front stage circuit of the resonant circuit is a full-bridge inverter. Figure 1 The LCL type transmitting coil resonant circuit shown can establish its differential equation as:

[0046]

[0047] Among them, v in is the inverter output voltage, v CP is the resonant capacitor C P The voltage, i CP is the current flowing into the resonant capacitor C P The current. d represents the differential, and t represents the time. CP / dt represents the current i CP The rate of change of the current i per unit time CP The amount of change. Similarly, dv CP / dt represents voltage v CP The rate of change of voltage v per unit time CP How much has changed.

[0048] In step S2, after solving the differential equation, the initial value of the state variable and the DC voltage V input to the inverter are obtained. in , the characteristic impedance Z0 of the transmitter resonant circuit and the characteristic frequency ω of the transmitter resonant circuit r The time domain expression of the state variables. Figure 1 The circuit structure relationship shown in the figure, in this embodiment, the state variable affecting the transmitting coil current is determined as v CP and i CP Then solve the differential equation shown in formula (1) and get v CP (t) and i CP The time domain expression of (t) is:

[0049]

[0050] Among them, V C0 and I C0 is the resonant capacitor CP The initial voltage value and initial current value of the transmitter resonant circuit; the characteristic impedance Characteristic frequency of the transmitter resonant circuit

[0051] In step S3, observe v CP (t) and i CP (t) in the time domain, it is found that there is an invariant parameter V in and Z0, then based on V in The time domain expression of the state variable is normalized by Z0, so that the differential equation of the normalized state variable is obtained. Normalization does not affect v CP (t) and i CP (t) has an impact on the transmitting coil current, but v CP (t) and i CP (t) is unified into one dimension to facilitate the implementation of subsequent steps. Here, v shown in formula (2) CP (t) and i CP The time domain expressions of (t) are divided by V in and V in / Z0 is normalized to obtain the normalized state variable v CPN (t) and i CPN The state equation of (t) is:

[0052]

[0053] Among them, v CPN (t) = v CP (t) / V in ,i CPN (t) = i CP (t)Z0 / V in , I C0N and V C0N Respective resonant capacitors C P The normalized initial voltage and current values ​​are:

[0054]

[0055] In step S4, the differential equation of the normalized state variable is transformed to obtain a trajectory equation including only the normalized state variable and the initial value of the normalized state variable. When obtaining the trajectory equation, it is necessary to distinguish between the two situations when the inverter output voltage is positive and when the inverter output voltage is negative.

[0056] Taking equation (3) as an example, when the inverter output voltage is a square wave positive half cycle, the equation of the positive half cycle circular trajectory is obtained by squaring the left and right sides of the two equations in equation (3) respectively, and then adding the left side of the squared equation to the left side, and the right side to the right side, and integrating them. The center of the circle is (0.5, 0):

[0057]

[0058] When the inverter output voltage is the negative half cycle of the square wave, the equation of the negative half cycle circular trajectory is as follows, and its center is (-0.5, 0):

[0059]

[0060] In step S5, firstly, the trajectory equation established in step S4 is used to draw the corresponding trajectory with the normalized state variable as the coordinate axis to obtain the steady-state trajectory of the normalized state variable. When the inverter output voltage is the positive half cycle of the square wave, the steady-state trajectory obtained by formula (5) is as follows: Figure 2 When the inverter output voltage is the negative half cycle of the square wave, the steady-state trajectory obtained by equation (6) is as follows: Figure 2 The overall steady-state trajectory is two large semicircles.

[0061] According to equations (5) and (6), the steady-state trajectory of the system consists of two arcs, corresponding to the positive half-cycle output and negative half-cycle output of the inverter. CPN -i CPN On the state plane, these two arcs and v CPN The intersection of the axes is (V CSN ,0) and (-V CSN ,0),V CSN The solution is:

[0062]

[0063] with i CPN The intersection of the axes is (0,I CSN ) and (0,-I CSN ), I CSN The solution is:

[0064]

[0065] The initial starting point is further determined to be the initial value of the normalized state variable corresponding to the inverter at time zero in the coordinate system of the normalized state variable. In this example, the initial starting point is v CPN -i CPN The coordinates of the state plane correspond to the normalized resonant capacitor voltage and current initial values ​​of the inverter at time zero (V C0N ,I C0N). The initial starting point is also the starting point of the starting trajectory. In this embodiment, the resonant capacitor has no initial value, that is, the starting point position is (0,0).

[0066] Step S6 specifically includes the following steps:

[0067] S61, determining the center positions of the multiple arcs according to the center of the trajectory equation;

[0068] S62. Taking the center position of the circle as the center of the circle, design multiple connected arcs in the space of the steady-state trajectory to obtain a starting trajectory. The starting trajectory starts from the initial starting point and ends on the steady-state trajectory.

[0069] In step S61, the center positions of the multiple arcs are determined by the center of the trajectory equation. According to equations (5) and (6), the center positions of the multiple arcs are selected from the centers (0.5, 0) and (-0.5, 0) of the trajectory equation. In order to achieve the continuity of the startup trajectory, the center positions of the multiple arcs are alternately selected from the centers (0.5, 0) and (-0.5, 0) in the connection order.

[0070] In step S62, if Figure 2 As shown, according to the coordinates of the initial starting point and the steady-state trajectory, a starting trajectory consisting of multiple arc segments is designed, and the end of the starting trajectory is connected to the steady-state trajectory. The starting trajectory designed in this embodiment includes three arc segments, such as Figure 2 As shown, it is formed by connecting arc I, arc II, and arc III, and the centers of the three arcs are (0.5, 0), (-0.5, 0), and (0.5, 0) respectively.

[0071] It should be noted that, in other implementations, the following methods may be used but are not limited to: Figure 2 The three arcs shown are used, but at least three arcs should be provided.

[0072] Step S7 specifically includes the following steps:

[0073] S71, determining multiple central angles corresponding to the multiple arcs according to the designed multiple arcs;

[0074] S72. Calculate the voltage pulse width time of the inverter corresponding to the multiple arcs in one cycle according to the multiple center angles corresponding to the multiple arcs, so as to obtain the inverter startup pulse sequence corresponding to the startup trajectory.

[0075] Continuing with the above example, in step S71, for arc I, which outputs a positive rectangular wave voltage for the inverter, the center of the arc is (0.5, 0), the radius ρ1 is designed to be 0.5, and the first angle α1 is designed to be 180°.

[0076] In step S72, according to the central angles corresponding to the multiple arcs, the voltage pulse width times of the inverter in multiple stages are calculated by dividing the central angles by π and then multiplying by the cycle time, where the cycle time is a cycle time corresponding to the characteristic frequency of the transmitting end resonant circuit.

[0077] For arc II, which outputs a negative rectangular wave voltage for the inverter, the center of the circle is (-0.5, 0), the radius ρ2 is designed to be 1.5, and the second angle α2 is solved by the following formula:

[0078]

[0079] Solving equation (9), we obtain the second angle α2 as 29.54°.

[0080] For arc III, which outputs a positive rectangular wave voltage for the inverter, the center of the circle is (0.5, 0), the radius ρ3 is designed to be 0.8, and the third angle α3 is calculated by the following formula:

[0081] α3=180°-α A -α B (10)

[0082] Auxiliary angle α A and α B like Figure 2 As shown, α A Solve it by the following formula:

[0083]

[0084] α B Solve it by the following formula:

[0085]

[0086] Solving for α A , α B and α3 are 67.58°, 51.32°, and 61.1° respectively.

[0087] Finally, the angle values ​​of α1, α2, and α3 are determined to be 180°, 29.54°, and 61.1°, respectively.

[0088] In step S72, according to the angle values ​​of α1, α2 and α3, by dividing the angle value by π and then multiplying by the cycle time, the voltage pulse width times T1, T2 and T3 of the inverter in the three stages (positive, negative, positive) can be calculated respectively:

[0089]

[0090] T r is the characteristic frequency ω r The corresponding cycle time.

[0091] Therefore, according to formula (13), we can get Figure 3 The inverter starts the pulse sequence shown and acts on Figure 1 The transmitting coil resonant circuit shown in the figure has a transient waveform of the transmitting coil current during the startup process. Figure 4 As shown. Figure 4 It can be seen that the transmitting coil current reaches the rated steady-state current within 1 cycle without overshoot or oscillation.

[0092] Figure 5 is the actual measured v CPN -i CPN The steady-state trajectory and startup trajectory are highly consistent with the steady-state trajectory and theoretical trajectory obtained by theoretical analysis.

[0093] Figure 4 and Figure 5 The effectiveness of the present invention in realizing the rapid start-up of the segmented transmitting coil without overshoot or oscillation is demonstrated.

[0094] Based on the above method, an embodiment of the present invention further provides a dynamic wireless power supply system transmitting coil current rapid start control system, which includes a processing unit, and the processing unit is used to implement the above dynamic wireless power supply system transmitting coil current rapid start control method.

[0095] In summary, the embodiment of the present invention provides a method for quickly starting the current of the transmitting coil of a dynamic wireless power supply system. The method includes establishing a differential equation of the transmitting coil resonant circuit of the dynamic wireless power supply system; determining the state variables that affect the current of the transmitting coil, solving the differential equation to obtain the time domain expression of the state variable; normalizing the time domain expression of the state variable to obtain the differential equation of the normalized state variable; according to the differential equation of the normalized state variable, finding the trajectory equation of the normalized state variable under different inverter output states; determining the steady-state trajectory of the normalized state variable according to the trajectory equation, and determining the initial starting point of the starting trajectory according to the steady-state trajectory; designing the starting trajectory from the initial starting state point to the steady-state trajectory; and calculating the inverter pulse sequence that realizes the starting trajectory according to the output mode of the inverter. The experimental results verify that the present invention can realize the starting of the transmitting coil current from the initial value to the rated value within 1-2 cycles without overshoot and oscillation, solving the problem of long starting time and possible overshoot of the traditional starting control method.

[0096] 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 method for quickly starting and controlling the current of a transmitting coil of a dynamic wireless power supply system, characterized in that: Includes steps: S1. Establish the differential equation of the transmitting coil resonant circuit of the dynamic wireless power supply system; S2. Determine the state variables that affect the current of the transmitting coil, and solve the differential equation to obtain the time domain expression of the state variables; S3, normalizing the time domain expression of the state variable to obtain a differential equation of the normalized state variable after the state variable is normalized; S4. According to the differential equation of the normalized state variable, finding the trajectory equation of the normalized state variable under different inverter output states; S5, determining a steady-state trajectory of the normalized state variable according to the trajectory equation, and determining an initial starting point of the starting trajectory according to the steady-state trajectory; S6, designing a starting trajectory from the initial starting state point to a steady-state trajectory; S7. Calculate an inverter pulse sequence for realizing the startup trajectory according to the output mode of the inverter.

2. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 1, characterized in that: In step S2, after solving the differential equation, the initial value of the state variable and the DC voltage V input to the inverter are obtained. in , the characteristic impedance Z0 of the transmitter resonant circuit and the characteristic frequency ω of the transmitter resonant circuit r The time domain expression of the state variables.

3. The method for rapid start-up control of transmitting coil current of a dynamic wireless power supply system according to claim 1, characterized in that: In step S3, based on the DC voltage V in The time domain expression of the state variable is normalized by the characteristic impedance Z0.

4. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 1, characterized in that: In step S4, the differential equation of the normalized state variable is transformed to obtain a trajectory equation including only the normalized state variable and the initial value of the normalized state variable.

5. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 4, characterized in that: In step S4, when obtaining the trajectory equation, the two cases of positive and negative inverter outputs are distinguished and the corresponding trajectory equations are determined respectively.

6. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 1, characterized in that: In step S5, the trajectory equation established in step S4 is used to draw a corresponding trajectory with the normalized state variable as the coordinate axis to obtain a steady-state trajectory of the normalized state variable.

7. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 6, characterized in that: In step S5, the initial starting point is the initial value of the normalized state variable corresponding to the zero time of the inverter in the coordinate system of the normalized state variable.

8. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 1, characterized in that: Step S6 specifically includes the following steps: S61, determining the center positions of the multiple arcs according to the center of the trajectory equation; S62. Taking the center position of the circle as the center of the circle, design multiple connected arcs in the space of the steady-state trajectory to obtain a starting trajectory. The starting trajectory starts from the initial starting point and ends on the steady-state trajectory.

9. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 8, characterized in that: The step S7 specifically includes the following steps: S71, determining multiple central angles corresponding to the multiple arcs according to the designed multiple arcs; S72. Calculate the voltage pulse width time of the inverter corresponding to the multiple arcs in one cycle according to the multiple center angles corresponding to the multiple arcs, so as to obtain the inverter startup pulse sequence corresponding to the startup trajectory.

10. The method for rapid start-up control of the transmitting coil current of a dynamic wireless power supply system according to claim 9, characterized in that: In step S72, according to the multiple central angles corresponding to the multiple arcs, the voltage pulse width times of the multiple stages of the inverter corresponding to the multiple arcs are calculated by dividing the central angle by π and then multiplying by the cycle time, and the cycle time is a cycle time corresponding to the characteristic frequency of the transmitting end resonant circuit.

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