Efficient wireless charging control system for electric automobile

Abstract

The invention provides an efficient wireless charging control system for an electric vehicle, and the system comprises a sensor assembly which is used for collecting an input current and an input voltage of a wireless charging system; the impedance estimation subsystem is used for calculating the input impedance of the wireless charging system of the electric vehicle; the mutual inductance estimation subsystem is used for calculating a mutual inductance value according to the input impedance; the current and voltage estimation subsystem is used for estimating the output current and the output voltage of the system according to the input current and the input voltage; the charging control subsystem is used for controlling a full-bridge inverter of the wireless charging system according to the estimated values of the output current and the output voltage and the mutual inductance value, accurate control over the charging process is achieved by monitoring fluctuation of the mutual inductance value, meanwhile, a primary side control method is adopted, the output current and the output voltage are estimated according to the input current and the input voltage, and therefore the charging efficiency is improved. And finally, output power control can be realized only by changing the size of the secondary side phase shift angle of the system, so that the system space is greatly saved, the system weight is reduced, and the system cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of charging control, and more particularly, to an efficient wireless charging control system for electric vehicles. Background Art

[0002] The wireless charging technology for electric vehicles mainly uses the principles of electromagnetic induction or magnetic resonance. An alternating current in the primary coil generates electromagnetic induction, which produces a current in the secondary coil, thus realizing wireless energy transmission. This technology provides a more convenient and flexible charging method for electric vehicles without physical connection.

[0003] In terms of wireless charging control technology, it mainly involves issues such as the precise alignment of the energy emission mechanism (ground transmitting coil) and the energy pickup mechanism (in-vehicle receiving coil), efficient energy transmission, and electromagnetic compatibility. To achieve efficient wireless charging, it is necessary to optimize the design of the charger and the matching degree between the transmitting coil and the receiving coil to improve the coupling coefficient and energy transmission efficiency. At the same time, the power output of wireless charging also needs to be considered to meet the demand for fast charging, but a balance also needs to be found among power, efficiency, and heat dissipation. However, in existing control technologies, multiple control strategies are often required to achieve perfect controllability of the charging process, which makes the structure of the control system extremely complex and unable to achieve precise control according to the change of the mutual inductance value during the charging process. Summary of the Invention

[0004] In view of this, the present invention proposes an efficient wireless charging control system for electric vehicles to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention proposes an efficient wireless charging control system for electric vehicles, including a sensor assembly, an impedance estimation subsystem, a mutual inductance estimation subsystem, a current and voltage estimation subsystem, and a charging control subsystem.

[0006] The sensor assembly is used to collect the input current and input voltage of the wireless charging system, including a voltage sensor and a current sensor respectively connected to the wireless charging system;

[0007] The impedance estimation subsystem is used to calculate the input impedance of the electric vehicle wireless charging system;

[0008] The mutual inductance estimation subsystem is used to calculate the mutual inductance value according to the input impedance;

[0009] The current and voltage estimation subsystem is used to estimate the output current and output voltage of the system according to the input current and input voltage;

[0010] The charging control subsystem is used to control the full-bridge inverter of the wireless charging system according to the estimated values of the output current and output voltage and the mutual inductance value.

[0011] Further, the impedance estimation subsystem calculates the input impedance according to the following formula:

[0012]

[0013] where Z in is the input impedance, R 1 , R 2 are the internal resistances of the primary and secondary coils, X 1 , X 2 are the reactances of the primary and secondary sides, Z ref is the equivalent reflected impedance of the primary side, ω is the operating angular frequency of the wireless charging system, M is the mutual inductance value, I 1 , I 2 are the primary and secondary current vectors respectively, R e is the equivalent resistance of the uncontrolled rectifier bridge.

[0014] Further, the mutual inductance estimation subsystem calculates the mutual inductance value according to the following formula:

[0015]

[0016] where θ is the phase angle by which the voltage leads the current, and V 1 is the primary and secondary voltage vector of the wireless charging system.

[0017] Further, the current and voltage estimation subsystem calculates the output current according to the following formula:

[0018]

[0019] where I out represents the output current, V in represents the input voltage, α represents the phase shift angle of the primary side of the wireless charging system, M is the mutual inductance value, and ω is the operating angular frequency of the wireless charging system.

[0020] Further, the current and voltage estimation subsystem calculates the output voltage according to the following formula:

[0021]

[0022] where V out represents the output voltage, I in represents the input current, α represents the phase shift angle of the primary side of the wireless charging system, M is the mutual inductance value, and ω is the operating angular frequency of the wireless charging system.

[0023] Furthermore, during the charging process, the charging control subsystem controls the output voltage and output current of the system by changing the magnitude of the primary side phase shift angle of the wireless charging system.

[0024] Furthermore, the charging control subsystem obtains the desired input voltage and desired input current of the system according to the requirement of the transmission power, calculates the adjustment value of the phase shift angle based on the difference between the expected value and the estimated value, generates the corresponding phase shift angle adjustment signal, and finally generates four PWM waves through the PI controller, and realizes the control of the full-bridge inverter after passing through the drive circuit.

[0025] Furthermore, during the charging process, the charging control subsystem adjusts the wireless charging process according to the fluctuation range of the mutual inductance value. Specifically:

[0026] When the mutual inductance value is within the normal range, power closed-loop regulation is adopted to finely adjust the duty cycle of the inverter;

[0027] When the mutual inductance value is less than the normal range, a dynamic matching mechanism is adopted to adjust the primary side resonant capacitor C through the adjustable capacitor array p to compensate for the reflected impedance;

[0028] When the change rate of the mutual inductance value exceeds 5 μH / s, the duty cycle of the inverter is reduced to 30% to limit the input power;

[0029] When the change rate of the mutual inductance value is less than 5 μH / s, the resonant frequency of the corresponding proportion is adjusted in advance according to the change value of the mutual inductance value.

[0030] Compared with the prior art, the beneficial effects of the present invention are that the present invention collects the input current and input voltage during the charging process of the wireless charging system through the sensor component, estimates the input impedance and mutual inductance value of the system according to the input current and input voltage, realizes the precise control of the charging process by monitoring the fluctuation of the mutual inductance value, and at the same time adopts the primary side control method, calculates the output current and output voltage of the system through the input current and input voltage, and finally realizes the output power control only by changing the magnitude of the secondary side phase shift angle of the system, which greatly saves the system space, reduces the system weight, and reduces the system cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0032] Figure 1 is a schematic diagram of an efficient wireless charging control system for electric vehicles in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0034] This embodiment proposes an efficient wireless charging control system for electric vehicles, as Figure 1 shown, including:

[0035] A sensor component, an impedance estimation subsystem, a mutual inductance estimation subsystem, a current and voltage estimation subsystem, and a charging control subsystem.

[0036] The sensor component is used to collect the input current and input voltage of the wireless charging system, including a voltage sensor and a current sensor respectively connected to the wireless charging system;

[0037] The impedance estimation subsystem is used to calculate the input impedance of the electric vehicle wireless charging system;

[0038] The mutual inductance estimation subsystem is used to calculate the mutual inductance value according to the input impedance;

[0039] The current and voltage estimation subsystem is used to estimate the output current and output voltage of the system according to the input current and input voltage;

[0040] The charging control subsystem is used to control the full-bridge inverter of the wireless charging system according to the estimated values of the output current and output voltage and the mutual inductance value.

[0041] The system of the present invention controls the electric vehicle wireless charging system for a series topology compensation network. The structure of the wireless charging system includes a DC power supply, a filter capacitor, a field effect transistor, a transmitting coil, a receiving coil, a load resistor, and a resonant compensation capacitor, and the secondary side of the electric vehicle is composed of a single-phase full-bridge uncontrollable circuit.

[0042] According to Kirchhoff's voltage law, the primary and secondary side voltage vectors of the wireless charging system can be expressed as:

[0043] V 1 = jωM I 2 + I 1 (jX 1 + R 1 ) (1)

[0044] V 2 = jωM I 1 + I 2 (jX 2 + R 2 + R e ) (2)

[0045] Among them, V 1 and V 2 are the primary and secondary side voltage vectors of the wireless charging system respectively, and I 1 and I 2 are the primary and secondary side current vectors respectively; X 1 and X 2 are the primary and secondary side reactances respectively; M is the mutual inductance; R 1 and R 2 are the internal resistances of the primary and secondary side coils respectively; R e is the equivalent resistance of the uncontrolled rectifier bridge.

[0046] Let the parameters of the primary and secondary side coils be the same, so the resonance compensation capacitors are also the same. Therefore, the reactances X 1 and X 2 of the primary and secondary sides can be expressed as:

[0047]

[0048] Among them, ω is the operating frequency of the wireless charging system.

[0049] Usually, the inverter needs to work in the resonance state, that is:

[0050]

[0051] Therefore, at the resonance frequency, the reactances X 1 and X 2 of the primary and secondary sides are 0. In most wireless charging systems, the internal resistance of the coil is small and can be ignored. Ignoring R 1 , R 2 , and R e later, the secondary side current phasor I 2 and the secondary side voltage phasor V 2 can be approximately expressed as:

[0052]

[0053] V 2 ≈ jωM I 1 (6)

[0054] When the wireless charging system is working properly, the load on the secondary side will be reflected to the primary side coil. At this time, the equivalent reflected impedance on the primary side is Z ref , and the input impedance obtained from the inverter is Z in, therefore, in a circuit where the resistor, primary and secondary reactances X1, and equivalent reflected impedance Z ref are in series, the system input impedance Z in is:

[0055]

[0056] After obtaining the system equivalent circuit, its input impedance Z in can also be calculated from the rms value of the primary voltage V 1 and the rms value of the current I 1 as:

[0057]

[0058] where θ is the phase angle by which the voltage leads the current.

[0059] Combining Equation (7) and Equation (8) gives:

[0060]

[0061] Equation (9) is a complex equation, and the real and imaginary parts of both sides need to be equal, resulting in Equation (10) and Equation (11):

[0062]

[0063] From the real part equation (10), the expression for the mutual inductance M can be derived:

[0064]

[0065] Mutual inductance is an important parameter in a wireless charging system. During the initialization phase, the system can operate at a non-resonant frequency state to estimate the mutual inductance value. Since the coil position does not change after charging starts and the mutual inductance remains basically unchanged, the estimated mutual inductance value can be used for subsequent control strategies.

[0066] After calculating the mutual inductance value of the wireless charging system, it is necessary to maintain it within a stable range to ensure stable power transmission. Therefore, in this embodiment, a dynamic adjustment strategy is adopted for the charging power control of the wireless charging system, including:

[0067] First, analyze the state of the mutual inductance value M and set a normal range, for example, 45 μH ≤ M ≤ 55 μH (allowing ±10% fluctuation). When the M value is less than 45, the charging process is in a low coupling state, such as when the vehicle is not aligned; when the M value is higher than 55, the charging process is in a high coupling state, such as when there are foreign objects around.

[0068] When the mutual inductance value M is within the normal range, power closed-loop regulation is adopted to finely adjust the inverter duty cycle (such as ±5%) to keep the output power stable.

[0069] When the mutual inductance value M is in the state of M < 45, the reason may be the decrease in coupling degree caused by vehicle offset or lift. At this time, a dynamic matching mechanism is adopted, and the primary side resonant capacitor C is adjusted through an adjustable capacitor array. p , to compensate for the reflected impedance, as shown in the following formula:

[0070]

[0071] For example, when M decreases by 20%, then C is increased. p to reduce the resonant frequency. At the same time, the phase-locked loop is started, and the operating frequency is adjusted from 85 kHz to 88 kHz to approach the new resonant point. If the output power is still insufficient, the DC bus voltage can be increased through the Boost circuit.

[0072] When the change rate of the mutual inductance value M exceeds 5 μH / s, it may be caused by foreign object intrusion or rapid vehicle displacement. At this time, it is necessary to detect whether there is a foreign object in the vehicle, and at the same time reduce the duty cycle of the inverter to 30% to limit the input power.

[0073] When the change rate of the mutual inductance value M is less than 5 μH / s, it may be caused by slow vehicle sliding. At this time, the resonant frequency should be reduced in advance according to the decrease value of M, or the servo motor should be controlled to move the transmitting coil horizontally to restore the M value to the normal range.

[0074] In the calculation formula of the mutual inductance M, the high-frequency alternating current I 1 is difficult to collect. Further, the high-frequency alternating current I 1 is estimated according to the principle of energy conservation. Assuming that the loss of the inverter is ignored, according to the energy conservation, it can be approximately obtained:

[0075] V in I in ≈V 1 I 1 cosθ(13)

[0076] where V in , I in are the input voltage and input current of the DC power supply.

[0077] According to the Fourier transform theory, the effective value of the fundamental wave voltage on the primary side V 1 can be expressed as:

[0078]

[0079] In the formula, α is the phase shift angle of the primary side full-bridge controllable circuit.

[0080] From formula (13) and formula (14), the expression of I 1 is:

[0081]

[0082] Combining equations (5), (6), (14), and (15), the output current I on the secondary DC side can be obtained. out and the output voltage V out The expressions are as follows:

[0083]

[0084] Through the above derivation, the control principle of the wireless charging system for electric vehicles is obtained. In equations (16) and (17), the output current I on the DC side out and the output voltage V out are only related to the phase-shift angle α on the primary side. Therefore, the output current I on the DC side out and the output voltage V out can be controlled by the phase-shift angle α on the primary side. In addition, the output current I out and the output voltage V out can also be estimated according to equations (16) and (17). Without communication, constant voltage and constant current control can be achieved only through primary-side control.

[0085] As a preferred embodiment, the present invention collects the input voltage V in and the input current I in through voltage and current sensors, and the current-voltage estimation subsystem estimates the output voltage or output current according to the sampling values of the sensors. When the estimated value is less than the expected value, the phase-shift angle α is increased; otherwise, the phase-shift angle α is decreased.

[0086] As a preferred embodiment, after obtaining the estimated values of the system input voltage and input current, the charging control subsystem obtains the expected input voltage and expected input current of the system according to the requirement of the transmission power, calculates the adjustment value of the phase-shift angle according to the difference between the expected value and the estimated value, generates a corresponding phase-shift angle adjustment signal, and finally generates four PWM waves through the PI controller, and realizes the control of the full-bridge inverter after passing through the drive circuit.

[0087] As a preferred embodiment, according to the above equations (16) and (17), the transfer function equations of the constant current control and constant voltage control of the wireless charging system are respectively expressed as follows:

[0088]

[0089] where k p and k I are respectively the proportional and integral parameters of the PI controller.

[0090] From equations (18) and (19), it can be seen that when k p and kI When it is greater than 0, the real part of the characteristic root of the transfer function is negative, and the system is stable. k p and k I The specific values need to be tuned through experiments according to different systems. PI control overcomes the disadvantages of pure proportional regulation with static error and slow pure integral regulation, and can improve both static and dynamic characteristics simultaneously. k p The larger k is, the faster the dynamic response speed of the system; k I The larger k is, the better the steady-state characteristics of the system.

[0091] Those skilled in the art should understand that the embodiments of the present invention can be provided as a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0092] The present invention is described with reference to the flowcharts and / or block diagrams of computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the processes and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0093] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device realizes the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0094] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Therefore, the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0095] Finally, it should be noted that the above-described embodiments are only specific implementation manners of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments, or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. All should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An efficient wireless charging control system for electric vehicles, characterized in that: It includes sensor components, impedance estimation subsystem, mutual inductance estimation subsystem, current and voltage estimation subsystem, and charging control subsystem. The sensor assembly is used to collect input current and input voltage of the wireless charging system, and includes a voltage sensor and a current sensor respectively connected to the wireless charging system; The impedance estimation subsystem is used to calculate the input impedance of the electric vehicle wireless charging system; The mutual inductance estimation subsystem is used to calculate the mutual inductance value according to the input impedance; The current and voltage estimation subsystem is used to estimate the output current and output voltage of the system according to the input current and input voltage; The charging control subsystem is used to control the full-bridge inverter of the wireless charging system according to the estimated values ​​of the output current and the output voltage and the mutual inductance value.

2. The high-efficiency wireless charging control system for electric vehicles according to claim 1, characterized in that: The impedance estimation subsystem calculates the input impedance according to the following formula: Among them, Z in is the input impedance, R1 and R2 are the internal resistance of the primary and secondary coils, X1 and X2 are the primary and secondary reactances, and Z ref is the equivalent reflected impedance of the primary side, ω is the operating angular frequency of the wireless charging system, M is the mutual inductance value, I1 and I2 are the primary and secondary current vectors, R e is the equivalent resistance of the uncontrolled rectifier bridge.

3. The high-efficiency wireless charging control system for electric vehicles according to claim 1, characterized in that: The mutual inductance estimation subsystem calculates the mutual inductance value according to the following formula: Among them, θ is the phase angle of voltage leading current, and V1 is the primary and secondary voltage vector of the wireless charging system.

4. The high-efficiency wireless charging control system for electric vehicles according to claim 1, characterized in that: The current and voltage estimation subsystem calculates the output current according to the following formula: Among them, I out Indicates output current, V in represents the input voltage, α represents the phase shift angle of the primary side of the wireless charging system, M is the mutual inductance value, and ω is the operating angular frequency of the wireless charging system.

5. The high-efficiency wireless charging control system for electric vehicles according to claim 1, characterized in that: The current and voltage estimation subsystem calculates the output voltage according to the following formula: Among them, V out Indicates output voltage, I in represents the input current, α represents the phase shift angle of the primary side of the wireless charging system, M is the mutual inductance value, and ω is the operating angular frequency of the wireless charging system.

6. The high-efficiency wireless charging control system for electric vehicles according to claim 1, characterized in that: During the charging process, the charging control subsystem controls the output voltage and output current of the system by changing the magnitude of the primary phase shift angle of the wireless charging system.

7. The high-efficiency wireless charging control system for electric vehicles according to claim 6, characterized in that: The charging control subsystem obtains the expected input voltage and expected input current of the system according to the transmission power requirement, calculates the adjustment value of the phase shift angle according to the difference between the expected value and the estimated value, and generates a corresponding phase shift angle adjustment signal. Finally, four PWM waves are generated through the PI controller, and the full-bridge inverter is controlled after passing through the drive circuit.

8. The high-efficiency wireless charging control system for electric vehicles according to claim 1, characterized in that: During the charging process, the charging control subsystem adjusts the wireless charging process according to the fluctuation range of the mutual inductance value, specifically: When the mutual inductance value is within the normal range, power closed-loop regulation is used to fine-tune the inverter duty cycle; When the mutual inductance value is less than the normal range, a dynamic matching mechanism is adopted to adjust the primary side resonant capacitor C through the adjustable capacitor array. p , to compensate for the reflected impedance; When the mutual inductance value change rate exceeds 5μH / s, the duty cycle of the inverter is reduced to 30% to limit the input power; When the change rate of the mutual inductance value is less than 5 μH / s, the resonant frequency of the corresponding proportion is adjusted in advance according to the change value of the mutual inductance value.

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