A method and system for simultaneous energy transmission in wireless charging of electric vehicles

Abstract

This invention discloses a method and system for simultaneous energy transmission and signal transmission in wireless charging of electric vehicles. The method includes the following steps: S1: Mapping the data to be transmitted from the primary side into corresponding characters, and encoding each character using 8-bit binary encoding, wherein each character's 8-bit binary code contains at most two 0 bits; S2: Determining the switching frequency, where encoding "1" corresponds to frequency f1 and encoding "0" corresponds to frequency f2; S3: Determining the frequency switching time point, and then generating a PWM square wave of the corresponding frequency to drive the inverter; S4: Reading the induced signal on the receiving coil and counting the rising edges of the two frequency signals; S5: Demodulating the corresponding binary character and restoring the data transmitted from the primary side. The effect is that, without changing the system structure and component parameters, system performance can be optimized simply by changing the encoding method, effectively reducing the impact of signal transmission on energy transmission.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology, and more specifically, relates to a method and system for simultaneous power transmission and communication for wireless charging of electric vehicles. Background Technology

[0002] Electric vehicles, as a clean energy mode of transportation, not only meet people's needs for convenient transportation but also serve as a replacement for traditional fuel vehicles, responding to national energy conservation and emission reduction strategies. With the rapid development of the global electric vehicle sector, the charging issue remains to be addressed. Traditional plug-in charging methods leave the cable socket exposed. During high-power charging, in rainy weather, water on the car surface or charging contacts can easily cause short circuits or electrical sparks, posing safety hazards to electric vehicles. Simultaneously, with the development of autonomous driving and automatic parking technologies for electric vehicles, automatic charging has become a crucial component in achieving intelligent and unmanned electric vehicle systems.

[0003] Based on the above problems and needs, wireless charging for electric vehicles has become a popular solution. Wireless charging technology for electric vehicles refers to an underground wireless charging energy transmitter, including a power supply, an AC-DC-AC high-frequency inverter, and a transmitting coil; and an on-board energy receiver, including a receiving coil, a rectifier, and an on-board battery. This technology obtains high-frequency AC power through the transmitter and, utilizing electromagnetic induction, transmits it to the on-board receiver via an energy coupling mechanism. During transmission, information needs to be transmitted between the ground coil and the on-board coil. However, independent communication modules are often interfered with by the energy coil, resulting in significant noise and a high bit error rate. Therefore, solving the problem of simultaneous energy signal transmission for electric vehicles has become a crucial step in realizing the practical application of wireless charging for electric vehicles.

[0004] Chinese Patent 200910191716.3 discloses a method and device for non-contact energy signal synchronous transmission, which transmits digital signals synchronously by changing the operating frequency of the inverter. However, its technical defect is that the frequency point corresponding to data 0 will hinder energy transmission. For electric vehicle wireless charging systems, if there are too many data signals 0, it will easily affect the efficiency of wireless power transmission. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention first provides a method for simultaneous energy and signal transmission for wireless charging of electric vehicles. This method re-encodes the pre-transmitted data and reduces the impact on energy during signal transmission by increasing the number of "1"s and decreasing the number of "0"s.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0007] A method for simultaneous transmission of information and energy for wireless charging of electric vehicles, the key of which includes the following steps:

[0008] S1: Map the data to be sent from the original edge into corresponding characters, and encode each character in an 8-bit binary encoding manner, with a maximum of 2 0 bits in the 8-bit binary encoding corresponding to each character;

[0009] S2: Determine the switching frequency based on the component parameters of the electric vehicle wireless charging system, where code "1" corresponds to frequency f1 and code "0" corresponds to frequency f2;

[0010] S3: Determine the frequency switching time point based on the switching frequencies f1 and f2, and then generate a PWM square wave of the corresponding frequency to drive the inverter switch on the primary side of the wireless charging system.

[0011] S4: Read the induced signal on the receiving coil and count the rising edges of the two frequency signals;

[0012] S5: Demodulate the corresponding binary characters based on the rising edges of the two frequency signals, and restore them to obtain the data sent by the original side.

[0013] Optionally, in step S1, the data to be sent from the original edge is mapped to corresponding characters consisting of 0 to 9, and the 8-bit binary code corresponding to each character is as follows:

[0014] symbol binary 0 00111111 1 11111110 2 11111101 3 11111011 4 11110111 5 11101111 6 11011111 7 10111111 8 01111111 9 11111100

[0015] In the binary code, "1" corresponds to frequency f1 and "0" corresponds to frequency f2.

[0016] Optionally, the wireless charging system for electric vehicles adopts an LCC-S topology.

[0017] In one implementation, frequency f1 is the system's inherent resonant frequency, and frequency f2 = 1 / 3 of frequency f1. For the LCC-S system topology, since the system has two resonant frequencies, frequency f1 can be chosen as the system's first resonant frequency, corresponding to the angular frequency... Frequency f2 is the second resonant frequency of the system, and the corresponding angular frequency is Where L s For the self-inductance of the receiving coil, C s Secondary side compensation capacitor value, C p1 It is the parallel resonant capacitor in the primary-side LCC resonant circuit.

[0018] Optionally, the duty cycle of the PWM square wave corresponding to each frequency in step S3 is 50%.

[0019] Based on the above method, the present invention also provides a simultaneous energy and signal transmission system for wireless charging of electric vehicles, the key of which is: including a DC power supply, a high-frequency inverter, a primary-side compensation network, a transmitting coil, a receiving coil, a secondary-side compensation network, a rectifier and filter circuit, and a load. The switching transistor of the high-frequency inverter is driven by a frequency converter signal transmitter. A demodulation device is provided on the receiving coil. The frequency converter signal transmitter and the demodulation device transmit primary-side data to secondary-side data according to the simultaneous energy and signal transmission method described above.

[0020] Optionally, the primary-side compensation network adopts an LCC compensation structure, and the secondary-side compensation network is provided with a secondary-side compensation capacitor.

[0021] The present invention provides a method and system for simultaneous transmission of energy and information for wireless charging of electric vehicles, which has the following features:

[0022] Beneficial effects:

[0023] This invention optimizes system performance by changing the encoding method without altering the system structure and component parameters, effectively reducing the impact of signal transmission on energy transmission. Attached Figure Description

[0024] Figure 1 This is a flowchart of the energy and communication transmission method for wireless charging of electric vehicles provided by the present invention.

[0025] Figure 2 A schematic diagram of the energy and communication transmission system for wireless charging of electric vehicles provided by the present invention;

[0026] Figure 3 for Figure 2 The equivalent circuit diagram of the energy transmission channel of the system shown is presented.

[0027] Figure 4 This is a waveform diagram of the modulated signal corresponding to the symbol "0" in the conventional ASCII encoding method;

[0028] Figure 5 This is a waveform diagram of the signal demodulation corresponding to the symbol "0" in the conventional ASCII encoding method;

[0029] Figure 6 The waveforms show a comparison of the load output voltage under different encoding methods. Detailed Implementation

[0030] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0031] First, this embodiment provides a method for simultaneous transmission of energy and information for wireless charging of electric vehicles, such as... Figure 1As shown, it includes the following steps:

[0032] S1: Map the data to be sent from the original edge into corresponding characters, and encode each character in an 8-bit binary encoding manner, with a maximum of 2 0 bits in the 8-bit binary encoding corresponding to each character;

[0033] S2: Determine the switching frequency based on the component parameters of the electric vehicle wireless charging system, where code "1" corresponds to frequency f1 and code "0" corresponds to frequency f2;

[0034] S3: Determine the frequency switching time point based on the switching frequencies f1 and f2, and then generate a PWM square wave of the corresponding frequency to drive the inverter switch on the primary side of the wireless charging system.

[0035] S4: Read the induced signal on the receiving coil and count the rising edges of the two frequency signals;

[0036] S5: Demodulate the corresponding binary characters based on the rising edges of the two frequency signals, and restore them to obtain the data sent by the original side.

[0037] In step S3, when determining the frequency switching time point, first calculate the switching frequency periods T1 = 1 / f1 and T2 = 1 / f2; then calculate the common multiples of T1 and T2, m1, m2, m3, m4..., and determine the modulation and demodulation bit error rates of m1, m2, m3, m4... through simulation verification and testing. Finally, select the least common multiple m with a bit error rate of 0. x Determine the frequency switching point to ensure that the two frequencies switch at the zero crossing point.

[0038] To achieve the above method, this embodiment adopts... Figure 2 The energy and signal transmission system for wireless charging of electric vehicles shown includes a DC power supply, a high-frequency inverter, a primary-side compensation network, a transmitting coil, a receiving coil, a secondary-side compensation network, a rectifier and filter circuit, and a load. The switching transistors of the high-frequency inverter are driven by a frequency converter signal transmitter. A demodulation device is provided on the receiving coil. The frequency converter signal transmitter and the demodulation device transmit primary-side data to secondary-side data according to the energy and signal transmission method described above.

[0039] pass Figure 2 As can be seen, this embodiment uses a WPT system based on an LCC-S resonant network. S1 to S4 form a high-frequency inverter, and the frequency converter transmits information by changing the switching frequency of the switching transistors. The transmitting coil and the receiving coil form a magnetic coupling structure. p1 C p1 C p2 An LCC resonant compensation network is constructed at the transmitting end, L s and C sA resonant compensation network is constructed at the receiving end. D1 to D4 form a rectifier, and C is a filter capacitor. The equivalent circuit of the above system is as follows: Figure 3 As shown, through analysis Figure 3 It can be seen that:

[0040] Ignoring the effects of parasitic internal resistance, the receiver circuit impedance is:

[0041]

[0042] According to the principle of reflection impedance, the reflection impedance from the secondary side to the primary side is:

[0043]

[0044] Analyzing the conditions for constant voltage output of the system, for the secondary side, if the induced voltage of the receiving coil is satisfied... If the voltage across the load remains constant, then the voltage across the load remains constant. Assuming the system's operating frequency and mutual inductance remain constant, this condition represents the primary current. Given that the primary side is a constant value and can be equivalent to a T-type circuit, we can derive:

[0045]

[0046] Where Δ1 is:

[0047]

[0048] Δ2 is:

[0049]

[0050] Let (4) equal to 0 so that the original edge With the value constant, the parameters of the secondary side are configured to resonant state and the imaginary part of the input impedance in equation (1) is made equal to 0. The resonant condition for constant voltage output independent of system load is derived as follows:

[0051]

[0052] Therefore, the primary current under this condition can be obtained:

[0053]

[0054] Output voltage:

[0055]

[0056] The output voltage depends only on the mutual inductance, the input voltage, and the primary-side compensation inductance, and is independent of the load. That is, the LCC-S topology used in this embodiment can meet the constant voltage output characteristics that are independent of the load.

[0057] In this embodiment, the encoding method proposed in this invention is defined as WPT-HW encoding. A comparison with traditional ASCII encoding is shown in Table 1. It can be seen that in specific implementation, the data to be sent from the original side in step S1 is mapped to corresponding characters consisting of 0 to 9. This invention increases the number of "1"s and decreases the number of "0"s during the encoding process. Therefore, in the simultaneous transmission of signal and energy, the number of frequency switching operations is reduced, thereby reducing the impact of signal transmission on energy transmission. In this example, frequency f1 is the first resonant frequency of the system, and the corresponding angular frequency is... Frequency f2 is the second resonant frequency of the system, and the corresponding angular frequency is Where L s For the self-inductance of the receiving coil, C s Secondary side compensation capacitor value, C p1 The parallel resonant capacitor in the primary LCC resonant circuit is used, and the duty cycle of the PWM square wave corresponding to each frequency in step S3 is 50%.

[0058] Table 1 Comparison of WPT-HW Protocol and ASCII Code

[0059]

[0060] In practice, the system's component parameters are configured as shown in Table 2:

[0061] Table 2 LCC-S Structural Design Parameters

[0062]

[0063] To further demonstrate the effects of this invention, simulation experiments are conducted below:

[0064] First, a test was conducted using ASCII encoding to verify that frequency modulation could transmit the signal from the primary side to the secondary side. In this example, the transmitted string was "00110000", which corresponds to "0" in ASCII. After modulation, according to... Figure 4 The PWM signal shown drives the inverter in the wireless charging system, and the signal received on the secondary side is demodulated to obtain a clearly distinguishable signal, such as... Figure 5 As shown, by Figure 5 It can be seen that when the modulator sends a signal of 00110000, the modulator successfully modulates to a low operating frequency at 0 and converts to a high operating frequency at 1. The receiver successfully receives the rising edge information and converts it into a readable voltage signal through the demodulator, thus verifying the effectiveness of the system's simultaneous transmission function.

[0065] Furthermore, to verify the superiority of the proposed method over traditional encoding methods, tests are conducted below using the transmission of 0 to 9 as examples, combined with... Figure 6 As can be seen, during the test, the system's output voltage was 101.2V when there was no information transmission. Using the traditional ASCII code, the voltage for "0-9" is around 97V, indicating that signal transmission in the energy-information simultaneous transmission system causes a voltage drop of about 4V, affecting the energy output. However, using the WPT-HW encoding method proposed in this invention to transmit the signal only caused a voltage drop of about 1V. This proves that without changing the system structure and component parameters, system performance can be optimized simply by changing the encoding method.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for simultaneous transmission of energy and information for wireless charging of electric vehicles, characterized in that, Includes the following steps: S1: Map the data to be sent from the original edge into corresponding characters, and encode each character in an 8-bit binary encoding manner, with a maximum of 2 0 bits in the 8-bit binary encoding corresponding to each character; S2: Determine the switching frequency based on the component parameters of the electric vehicle wireless charging system, where code "1" corresponds to frequency f1 and code "0" corresponds to frequency f2; S3: Determine the frequency switching time point based on the switching frequencies f1 and f2, and then generate a PWM square wave of the corresponding frequency to drive the inverter switch on the primary side of the wireless charging system. S4: Read the induced signal on the receiving coil and count the rising edges of the two frequency signals; S5: Demodulate the corresponding binary characters based on the rising edges of the two frequency signals, and restore them to obtain the data sent by the original side; When determining the frequency switching point, the first switching frequency period is calculated based on the switching frequency f1, and the second switching frequency period is calculated based on the switching frequency f2. Calculate several common multiples of the first switching frequency period and the second switching frequency period; Determine the modulation and demodulation bit error rates by a number of common multiples; The least common multiple of the modulation and demodulation bit error rates (BER) of several common multiples is selected to determine the frequency switching point.

2. The energy transmission method for wireless charging of electric vehicles according to claim 1, characterized in that, In step S1, the data to be sent from the original edge is mapped to corresponding characters consisting of 0 to 9. The 8-bit binary code for each character is as follows: In the binary code, "1" corresponds to frequency f1 and "0" corresponds to frequency f2.

3. The energy transmission method for wireless charging of electric vehicles according to claim 2, characterized in that, The wireless charging system for electric vehicles adopts the LCC-S topology.

4. The energy transmission method for wireless charging of electric vehicles according to claim 1, characterized in that, Frequency f1 is the system's natural resonant frequency, and frequency f2 = 1 / 3 of frequency f1.

5. The energy transmission method for wireless charging of electric vehicles according to claim 3, characterized in that, Frequency f1 is the first resonant frequency of the system, and the corresponding angular frequency is Frequency f2 is the second resonant frequency of the system, and the corresponding angular frequency is Where L s For the self-inductance of the receiving coil, C s Secondary side compensation capacitor value, C p1 It is the parallel resonant capacitor in the primary-side LCC resonant circuit.

6. The energy transmission method for wireless charging of electric vehicles according to any one of claims 1-5, characterized in that, In step S3, the duty cycle of the PWM square wave corresponding to each frequency is 50%.

7. A power transmission system for wireless charging of electric vehicles, characterized in that: The system includes a DC power supply, a high-frequency inverter, a primary-side compensation network, a transmitting coil, a receiving coil, a secondary-side compensation network, a rectifier and filter circuit, and a load. The switching transistors of the high-frequency inverter are driven by a frequency converter signal transmitter. A demodulation device is provided on the receiving coil. The frequency converter signal transmitter and the demodulation device transmit primary-side data to secondary-side data according to the simultaneous transmission method described in any one of claims 1-6.

8. The energy transmission system for wireless charging of electric vehicles according to claim 7, characterized in that: The primary-side compensation network adopts an LCC compensation structure, and the secondary-side compensation network is equipped with a secondary-side compensation capacitor.

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