Wireless power transmission system capable of realizing fault tolerance and receiving end lightweight and control strategy thereof

Abstract

The invention provides a wireless power transmission system capable of realizing fault tolerance and light weight of a receiving end, which is characterized in that a high-frequency inverter, a first transmitting coil and a compensation capacitor of the first transmitting coil are connected in series, and are connected in parallel with a parallel compensation capacitor after being connected in series; the second transmitting coil and the compensation capacitor of the second transmitting coil are connected in series and then are connected in parallel with the parallel compensation capacitor; a compensation capacitor of the first receiving coil is connected in series with an input port of the first rectifier; and the compensation capacitor of the second receiving coil is connected in series with the input port of the second rectifier. According to the method, no extra conditions, auxiliary elements and bilateral communication are needed, the optimal receiving end light weight effect and fault tolerance of common faults such as load open circuit and load short circuit can be achieved while the zero phase angle characteristic is guaranteed, and the fault current multiple is minimum under the fault condition.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to a wireless power transmission system capable of achieving fault tolerance and lightweight receiving end and a control strategy thereof. Background Art

[0002] Wireless power transfer (WPT) does not require electrical contact between the power transmitter and the receiver, and is convenient, safe, and reliable. Among them, magnetic coupling WPT technology has received widespread attention from academia and industry, and has been first applied to consumer electronics, electric vehicles, and other fields.

[0003] In order to shorten the charging time and effectively alleviate the user's mileage anxiety, high power and high power density have always been one of the important research directions of WPT technology. Specific ways to increase the power level of the WPT system include series connection of power devices / converters, modular parallel connection, etc. Among them, since the output power is mainly limited by the rated current, it is relatively rare to increase the rated voltage by series connection. Modular parallel connection is still the most common and most promising way to achieve high-power WPT.

[0004] However, with the continuous increase in power levels, high-power WPT systems are facing the threat of common faults such as short circuits and open circuits, and the fault problem of large-capacity WPT systems is even more serious. Once such faults occur, they will cause irreversible damage to the WPT system. To this end, current research has formed two mainstream technical routes: one is to develop fault diagnosis technology for typical faults and formulate corresponding protection strategies, and the other is to improve the system's own fault tolerance performance through optimized design.

[0005] In terms of fault-tolerant design, the use of LCC compensation topology at the transmitting end can effectively deal with the problem that the receiving end of the WPT system under the SS topology is not allowed to be open-circuited; the high-power WPT system with a modular parallel structure also naturally has a certain fault-tolerant performance and can maintain operation through other normal modules; based on the improvement of compensation topology, parameters and system structure, detuning compensation, dual coupling structure, LCC-N topology, additional relay coils, etc. have also been proposed for fault tolerance.

[0006] At the same time, lightweight and compact design is another issue that needs to be considered for high-power WPT systems. However, obtaining unconventional fault-tolerant performance may require additional components, which is somewhat inconsistent with the lightweight requirements. Some literature on the fault-tolerant design of WPT systems also considers the lightweight design issue, starting from system control, magnetic couplers, compensation topology and parameters, etc., eliminating the redundancy of receiving end detection and control, magnetic coupler core, compensation components, filter components, etc. However, the solutions proposed by these research institutes either sacrifice the zero phase angle characteristics of the WPT system, or require special conditions such as strong coupling, which are difficult to implement, and few literatures conduct research under the modular parallel structure suitable for high-power WPT.

[0007] In summary, it is still challenging to simultaneously solve the fault tolerance and lightweight design of WPT systems, especially in high-power scenarios. Summary of the invention

[0008] In view of this, the present invention provides a wireless power transmission system and a control strategy that can achieve fault tolerance and lightweight receiving end, so as to solve the problems that the prior art cannot achieve or is difficult to achieve fault tolerance and the implementation of fault tolerance affects the zero phase angle characteristics, lightweight and compactness level of the WPT system.

[0009] The system of the present invention comprises an input unit, a transmitting unit, a receiving unit, and an output unit; it also comprises a single chip microcomputer, a driving circuit, and a DC / DC converter; The single chip microcomputer provides a PWM signal input to the driving circuit; The input part, the transmitting part, the receiving part and the output part are coupled in sequence; The input unit includes a high frequency inverter; The transmitting unit includes a first transmitting coil L p1 , the second transmitting coil L p2 And the corresponding compensation capacitor C p1 , compensation capacitor C p2 , parallel compensation capacitor C 0 ; The receiving unit includes a first receiving coil L s1 , the second receiving coil L s2 And the corresponding compensation capacitor C s1 , compensation capacitor C s2 ; The output unit includes a first receiving coil L s1, the second receiving coil L s2 A corresponding first rectifier and a second rectifier; The high-frequency inverter, the first transmitting coil and the compensation capacitor of the first transmitting coil are connected in series, and the three are connected in series and then connected in parallel with the parallel compensation capacitor; the second transmitting coil and the compensation capacitor of the second transmitting coil are connected in series, and the two are connected in series and then connected in parallel with the parallel compensation capacitor; the first receiving coil, the compensation capacitor of the first receiving coil and the input port of the first rectifier are connected in series; the second receiving coil, the compensation capacitor of the second receiving coil and the input port of the second rectifier are connected in series; the input port of the DC / DC converter is connected in parallel with the output ports of the first rectifier and the second rectifier; the output port of the DC / DC converter is connected in parallel with the load resistor.

[0010] Furthermore, the capacitance of the compensation capacitor is determined according to formula (1): ; In the formula, is the system operating angular frequency.

[0011] Further, the first transmitting coil is decoupled from the second transmitting coil and the second receiving coil respectively; The second transmitting coil is decoupled from the first transmitting coil and the first receiving coil respectively.

[0012] Furthermore, M ps1 for L p1 and L s1 The mutual induction between M ps2 for L p2 and L s2 mutual induction between Compensation capacitor C 0 , equivalent resistance R d , mutual induction M ps1 , M ps2 and the system operating angular frequency Satisfying the relationship (2): ; In the formula, R eq =n R d , where the size of n depends on the topology of the rectifier circuit.

[0013] Furthermore, the wireless power transmission system adopts a magnetic coupler structure, and the magnetic coupler includes a first transmitting coil, a second transmitting coil, a first receiving coil, and a second receiving coil; Among them, the first transmitting coil and the second transmitting coil constitute the transmitting end of the magnetic coupler. The first transmitting coil adopts a "field" - shaped coil structure, including 4 planar square windings arranged in a "field" shape. The 4 windings are connected in series, and any two adjacent windings among the 4 windings are connected in series in the same direction. The second transmitting coil adopts a planar square coil structure; The first receiving coil and the second receiving coil constitute the receiving end of the magnetic coupler. The first receiving coil adopts a "field" - shaped coil structure, including 4 planar square windings arranged in a "field" shape. The 4 windings are connected in series, and any two adjacent windings among the 4 windings are connected in series in the same direction. The second receiving coil adopts a planar square coil structure. The transmitting end and the receiving end of the magnetic coupler are placed parallel, with their four - side edges parallel. When they are facing each other, their centers are on the same vertical line.

[0014] Furthermore, a control strategy that can achieve fault tolerance and lightweight of the receiving end is provided, including the following steps: Step 1: Detect the DC currents at the output ports of the first rectifier and the second rectifier I d1 and I d2 ; Step 2: Judge whether exceeds the allowable error range. If so, execute Step 3; otherwise, end. Step 3: Compare the magnitudes of I d1 and I d2 . If I d1 > I d2 , equivalently increase the equivalent resistance R d through the impedance transformation of the DC / DC converter and execute Step 1. Conversely, decrease the equivalent resistance R d and execute Step 1.

[0015] The beneficial effects of the present invention: The present invention provides a wireless power transmission system capable of achieving fault tolerance and receiving end lightweight, which can achieve fault tolerance for common faults such as open-circuit load and short-circuit load while ensuring zero phase angle characteristics without any additional conditions and auxiliary components; the first transmitting coil of the system also plays the role of a compensation component, the transmitting end has high integration, the receiving end adopts series compensation, the compensation components are few and no compensation inductance is required, and when the system is working normally, the DC output bus voltage can be made more stable in conjunction with the corresponding control strategy, the required DC filter capacitor capacity and volume weight are smaller, and the receiving end has a high lightweight level; the control strategy of the wireless power transmission system capable of achieving fault tolerance and receiving end lightweight can complete the adjustment of the load resistance under various offset conditions without bilateral communication, so that when the system is working normally, the currents of the two receiving coils are equal, the lightweight effect of the receiving end of the system is maximized, and the fault current multiple is minimized under load open-circuit and short-circuit faults, thereby improving the fault tolerance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention has the following accompanying drawings: Figure 1 Schematic diagram of the structure of a wireless power transmission system that can achieve fault tolerance and lightweight receiving end; Figure 2 Schematic diagram of the magnetic coupler structure of the wireless power transmission system that can achieve fault tolerance and lightweight receiving end; Figure 3 Flowchart of control strategy for wireless power transmission system that can achieve fault tolerance and lightweight receiving end; Figure 4 Test results of the wireless power transmission system embodiment during normal operation; Figure 5 Test results of the wireless power transfer system embodiment under fault conditions. DETAILED DESCRIPTION

[0017] In order to make the objects, advantages and features of the present invention more obvious, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, an embodiment of the present invention provides a wireless power transmission system that can achieve fault tolerance and lightweight receiving end, and is applied to an example of a full-bridge rectifier circuit. U p It is the system high frequency AC input voltage; L p1 and L p2 They are transmitting coil 1 and transmitting coil 2 respectively; C p1 and C p2They are the compensation capacitors of transmitting coil 1 and transmitting coil 2 respectively; C 0 is the parallel compensation capacitor; M ps1 for L p1 and L s1 mutual induction between M ps2 for L p2 and L s2 mutual induction between L s1 and L s2 They are receiving coil 1 and receiving coil 2 respectively; C s1 and C s2 They are the compensation capacitors of receiving coil 1 and receiving coil 2 respectively; R L The wireless power transmission system comprises a high-frequency inverter, a transmitting coil 1 and a compensation capacitor of the transmitting coil 1 connected in series, and then connected in parallel with the parallel compensation capacitor after the three are connected in series; a transmitting coil 2 and a compensation capacitor of the transmitting coil 2 are connected in series, and then connected in parallel with the parallel compensation capacitor after the two are connected in series; a receiving coil 1, a compensation capacitor of the receiving coil 1 and an input port of the rectifier 1 are connected in series; a receiving coil 2, a compensation capacitor of the receiving coil 2 and an input port of the rectifier 2 are connected in series; an input port of the Buck-Boost converter is connected in parallel with the output ports of the rectifier 1 and the rectifier 2; and an output port of the Buck-Boost converter is connected to the load resistor. R L in parallel.

[0019] It should be noted that the capacitance of the compensation capacitor in the wireless power transmission system is determined according to formula (1): ; In the formula, is the system operating angular frequency.

[0020] It should be pointed out that the transmitting coil 1 of the wireless power transmission system is decoupled from the transmitting coil 2 and the receiving coil 2 respectively, and the transmitting coil 2 is decoupled from the transmitting coil 1 and the receiving coil 1 respectively.

[0021] It should be noted that the compensation capacitor in the wireless power transmission system C 0 , load resistance R d , mutual induction M ps1 ,M ps2 and the system operating angular frequency satisfy the relationship in Equation (2): ; wherein, according to the topological structure of the full-bridge rectifier circuit: .

[0022] It should be noted that when there is a DC / DC converter at the receiving end, the equivalent resistance in the formula should consider the impedance transformation effect of the converter.

[0023] The wireless power transmission system adopts a magnetic coupler structure as shown in Figure 2 : The magnetic coupler includes a transmitting coil 1, a transmitting coil 2, a receiving coil 1, and a receiving coil 2. Among them, the transmitting coil 1 and the transmitting coil 2 constitute the transmitting end of the magnetic coupler. The transmitting coil 1 adopts a "field" - shaped coil structure, including 4 planar square windings arranged in a "field" shape. The 4 windings are connected in series, and any two adjacent windings among the 4 windings are connected in series in the same direction. The transmitting coil 2 adopts a planar square coil structure; the receiving coil 1 and the receiving coil 2 constitute the receiving end of the magnetic coupler. The receiving coil 1 also adopts a "field" - shaped coil structure, including 4 planar square windings arranged in a "field" shape. The 4 windings are connected in series, and any two adjacent windings among the 4 windings are connected in series in the same direction. The receiving coil 2 still adopts a planar square coil structure. The transmitting end and the receiving end of the magnetic coupler are placed parallel, with their four - side edges parallel. When they are facing each other, their centers are on the same vertical line.

[0024] Based on the above - mentioned wireless power transmission system, another embodiment of the present invention shows a control strategy as shown in Figure 3 and includes the following 3 steps: Step 1: Detect the DC currents at the output ports of rectifier 1 and rectifier 2 I d1 and I d2 ; Step 2: Judge whether exceeds the allowable error range. If so, execute Step 3; otherwise, end. Step 3: Compare the magnitudes of I d1 and I d2 . If I d1 > I d2 then reduce the duty cycle of the PWM signal and execute Step 1. Conversely, increase the duty cycle of the PWM signal and execute Step 1.

[0025] It should be noted that those skilled in the art know that the equivalent resistance can be adjusted by changing the duty cycle of the PWM signalR d size.

[0026] The design parameters of the magnetic coupler used in this example are shown in Table 1, and the designed magnetic coupler coils and windings are all densely wound.

[0027] Table 1 Magnetic coupler design parameters parameter value Field-shaped coil outer diameter / mm 800×800 Number of turns of the field coil winding 6 Square coil outer diameter / mm 700×700 Square coil turns 8 Litz line pitch / mm 6 Air gap / mm 150 According to the design parameters in Table 1, the magnetic coupler was trial-produced. The measured self-inductances of the transmitting coil 1, transmitting coil 2, receiving coil 1 and receiving coil 2 of the magnetic coupler were 158.41μH, 101.30μH, 160.50μH and 100.44μH respectively. Correspondingly, at the rated operating frequency of the system of 85kHz, the capacitance of each compensation capacitor is designed according to formula (1): C p1 =24.84nF, C 0 =199.55nF, C p2 =41.89nF, C s1 =21.79nF and C s2 =34.84nF. Due to the constraints of the adopted magnetic coupler structure, the mutual inductance between the transmitting coil 1 and the transmitting coil 2, the transmitting coil 1 and the receiving coil 2, the transmitting coil 2 and the transmitting coil 1, and the transmitting coil 2 and the receiving coil 1 can be ignored. The mutual inductance between the transmitting coil 1 and the receiving coil 1 is 17.52μH, and the mutual inductance between the transmitting coil 2 and the receiving coil 2 is 28.63μH.

[0028] A test prototype was built to test the fault tolerance capability, lightweight effect of the receiving end and effectiveness of the control strategy of the wireless power transmission system embodiment. During normal operation, the control strategy is adopted to adjust the duty cycle of the PWM signal output by the single-chip microcomputer, thereby changing the on-time of the power device in the Buck-Boost converter, and the equivalent resistance seen from the input port of the Buck-Boost converter is R d is adjusted to 10Ω, which is basically consistent with the theoretical value calculated using formula (2). At this time, the test results of the wireless power transmission system embodiment are as follows: Figure 4 As shown in the figure P o and η are the system output power and transmission efficiency respectively. Figure 4It shows that the current amplitudes on receiving coil 1 and receiving coil 2 are basically the same, and the phase difference is approximately π / 2, which confirms that the control strategy of the wireless power transmission system has been executed and verified its effectiveness. According to calculations, in order to achieve the same DC output ripple level, the required capacity of the system DC filter capacitor can be reduced by about 90%. The test results of the wireless power transmission system embodiment under load open circuit and load short circuit faults are shown in Figure 1. Figure 5 As shown in the figure, it can be seen that the system will not have large overcurrent and overvoltage under load open circuit and short circuit conditions. The maximum multiple of the fault current relative to the normal working current under both faults is about 2 times, which shows the effect of the control strategy in minimizing the system fault current multiple and improving the system fault tolerance.

[0029] It should be noted that any process or method description in the embodiments may be understood as representing a module, fragment or portion of a code including one or more executable instructions for implementing steps of a specific logical function or process, and that the scope of the preferred embodiments of the present invention includes alternative implementations in which the functions may not be performed in the order shown or discussed, including performing the functions in a substantially simultaneous manner or in the reverse order according to the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0030] It should be noted that the logic and / or steps in the embodiments, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or equipment (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or equipment and execute instructions), or in combination with these instruction execution systems, devices or equipment. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or equipment, or in combination with these instruction execution systems, devices or equipment. More specific examples of computer-readable media (non-exhaustive list) include the following: an electrical connection with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0031] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0032] A person skilled in the art may understand that all or part of the steps of implementing the above-mentioned embodiment method may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0033] In addition, each functional module in the embodiment of the present invention may be integrated into a processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0034] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0035] The above embodiments describe the technical solutions of the present invention in detail. Obviously, the present invention is not limited to the described embodiments. Based on the embodiments of the present invention, people familiar with the technical field can also make various changes accordingly, but any changes that are equivalent or similar to the present invention belong to the scope of protection of the present invention.

[0036] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A wireless power transmission system capable of achieving fault tolerance and lightweight receiving end, characterized in that: It includes an input section, a transmitting section, a receiving section, and an output section; The input section, the transmitting section, the receiving section, and the output section are sequentially coupled; The input section includes a high-frequency inverter; The transmitting unit includes a first transmitting coil L p1 , the second transmitting coil L p2 And the corresponding compensation capacitor C p1 , compensation capacitor C p2 , parallel compensation capacitor C 0; The receiving unit includes a first receiving coil L s1 , the second receiving coil L s2 And the corresponding compensation capacitor C s1 , compensation capacitor C s2 ; The output unit includes a first receiving coil L s1 , the second receiving coil L s2 A corresponding first rectifier and a second rectifier; The wireless power transmission system further includes a single-chip microcomputer, a driving circuit, and a DC / DC converter; The single-chip microcomputer provides a PWM signal and inputs it to the driving circuit; The single-chip microcomputer executes a control strategy that can achieve fault tolerance and lightweight at the receiving end; The control strategy adjusts the equivalent resistance according to the output current of the first rectifier and the second rectifier R d size; The high-frequency inverter, the first transmitting coil, and the compensation capacitor of the first transmitting coil are connected in series, and after the three are connected in series, they are connected in parallel with the parallel compensation capacitor; the second transmitting coil is connected in series with the compensation capacitor of the second transmitting coil, and after the two are connected in series, they are connected in parallel with the parallel compensation capacitor; the first receiving coil, the compensation capacitor of the first receiving coil, and the input port of the first rectifier are connected in series; the second receiving coil, the compensation capacitor of the second receiving coil, and the input port of the second rectifier are connected in series; The input port of the DC / DC converter is connected in parallel with the output ports of the first rectifier and the second rectifier; the output port of the DC / DC converter is connected in parallel with the load resistor.

2. The wireless power transmission system according to claim 1, characterized in that: The capacitance value of the compensation capacitor is determined according to Equation (1): ； In the formula, is the system operating angular frequency.

3. The wireless power transmission system according to claim 2, characterized in that: The first transmitting coil is decoupled from the second transmitting coil and the second receiving coil respectively; The second transmitting coil is decoupled from the first transmitting coil and the first receiving coil respectively.

4. The wireless power transmission system according to claim 3, wherein set up M ps1 for L p1 and L s1 The mutual induction between M ps2 for L p2 and L s2 mutual induction between Compensation capacitor C 0. Equivalent resistance R d , mutual induction M ps1 , M ps2 and the system operating angular frequency Satisfying the relationship (2): ； In the formula, R eq =n R d , where the size of n depends on the topology of the rectifier circuit.

5. The wireless power transmission system according to claim 4, characterized in that: The wireless power transmission system adopts a magnetic coupler structure, and the magnetic coupler includes a first transmitting coil, a second transmitting coil, a first receiving coil, and a second receiving coil; Among them, the first transmitting coil and the second transmitting coil form the transmitting end of the magnetic coupler. The first transmitting coil adopts a "field" - shaped coil structure, including 4 planar square windings arranged in a "field" shape. The 4 windings are connected in series, and any two adjacent windings among the 4 windings are connected in series in the same direction. The second transmitting coil adopts a planar square coil structure; The first receiving coil and the second receiving coil form the receiving end of the magnetic coupler. The first receiving coil adopts a "field" - shaped coil structure, including 4 planar square windings arranged in a "field" shape. The 4 windings are connected in series, and any two adjacent windings among the 4 windings are connected in series in the same direction. The second receiving coil adopts a planar square coil structure; The transmitting end and the receiving end of the magnetic coupler are placed in parallel, with the four edges parallel. When facing each other, the centers of the transmitting end and the receiving end are on the same vertical line.

6. The wireless power transmission system according to claim 5, characterized in that: The control strategy that can achieve fault tolerance and lightweight at the receiving end includes the following steps: Step 1: Detect the DC current at the output ports of the first rectifier and the second rectifier I d1 and I d2 ; Step 2: Judgement | I d1 - I d2 |Whether it exceeds the allowable error range, if so, proceed to step 3, otherwise end; Step 3: Compare I d1 and I d2 The size of I d1 > I d2 The equivalent resistance is increased equivalently through the impedance conversion effect of the DC / DC converter R d And execute step 1, otherwise reduce the load resistance R d And execute step 1.

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