Integrated magnetic coupling mechanism for improving power density of WPT system, and WPT system

Abstract

The present invention relates to the technical field of wireless power transmission (WPT). Specifically disclosed are an integrated magnetic coupling mechanism for improving the power density of a WPT system, and a WPT system. Magnetic integration design is performed on a magnetic coupling mechanism, which specifically involves: providing a current-doubling inductive coil LB in a hollow area of a secondary D-shaped coil LS, and improving a circuit topology, specifically, dividing the current-doubling inductive coil LB into two coils, and connecting the two coils in a full-bridge rectifier circuit at a receiving end of a WPT system. In this way, it can be ensured that the currents in the two coils are always at positive values, thereby achieving a corresponding current-doubling effect, improving the power density of the system, and reducing the weight of an on-board end. Moreover, by means of designing the inductance value of the current-doubling coil, ripples in an output voltage can be reduced while ensuring output power remaining unchanged. In the present invention, providing a current-doubling rectifier topology of a current-doubling inductive coil is also applicable to other circuit topologies having the problem of excessive inductance, and the present invention has the universal applicability characteristic for a circuit topology in wireless transmission.

Description

Magnetic integrated coupling mechanism and WPT system for improving the power density of WPT system Technical Field

[0001] The present invention relates to the field of wireless power transmission technology, and in particular to a magnetic integrated coupling mechanism for improving the power density of a WPT system and a WPT system using the magnetic integrated coupling mechanism. Background Art

[0002] With rapid economic and population growth, as well as rapid urbanization, the number of cars is increasing, and the shortage of traditional energy sources and environmental pollution are becoming increasingly prominent. In particular, the harm that traditional fuel vehicles pose to the environment and resources is a significant development. Therefore, the development of electric vehicles (EVs) is of great significance. However, traditional EV wired charging has many limitations, such as fragile connections (due to aging and leakage), sparks during plugging and unplugging, which pose safety risks, and a large footprint. Power batteries also suffer from high costs and short range. Magnetic coupling wireless charging technology offers a solution to these charging issues, but with the development of wireless charging technology for EVs, the requirements for onboard output power are becoming increasingly stringent.

[0003] Existing methods for increasing circuit topology output power primarily include increasing input parameters such as voltage and current, or adding circuit components. Increasing input parameters does not fundamentally improve vehicle-mounted output power, while adding circuit components increases the weight and volume of the receiver. Therefore, it is necessary to meet the requirement of lightweight receivers while increasing output power.

[0004] Summary of the Invention

[0005] The present invention provides a magnetic integrated coupling mechanism and a WPT system for improving the power density of the WPT system, and solves the technical problem of how to improve the system output power while meeting the lightweight requirements of the receiving end.

[0006] In order to solve the above technical problems, the present invention provides a magnetic integrated coupling mechanism for improving the power density of the WPT system, comprising a primary D-type coil L P , secondary side D-type coil L S , and the D-type coil L located on the secondary side S The current-doubling inductor L in the hollow area B , the current-doubling inductor L B It includes the same first current doubling inductor L1 and second current doubling inductor L2; the first current doubling inductor L1 and the second current doubling inductor L2 are connected to the full-bridge rectifier circuit at the receiving end of the WPT system, which can ensure that the current in the first current doubling inductor L1 and the second current doubling inductor L2 is always positive.

[0007] Preferably, the full-bridge rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The first output end of the secondary resonant network of the WPT system is connected to the first current doubling inductor L1 and then to the positive end of the first diode D1. The negative end of the first diode D1 is connected to the load resistor R L The second output end of the secondary resonant network is connected to the second current doubling inductor L2 and then to the positive end of the second diode D2, and the negative end of the second diode D2 is connected to the load resistor R L One end of the third diode D3 is forward connected to the load resistor R L The fourth diode D4 is connected in a forward direction to the load resistor R L between the other end of the secondary resonant network and the second output end of the secondary resonant network.

[0008] Preferably, the inductance L1 of the first current-doubling inductor L1 and the inductance L2 of the second current-doubling inductor L2 satisfy:

[0009] Where D is the primary inverter duty cycle of the WPT system, U L is the load voltage, C is the resistor connected to the full-bridge rectifier circuit and the load resistor R L The capacitance value of the filter capacitor between the two, f is the system operating frequency, △U L is the output voltage ripple.

[0010] Preferably, the magnetic integrated coupling mechanism also includes a secondary side D-type coil L S The receiving end magnetic core is arranged in layers, and the first current-doubling inductor L1 and the second current-doubling inductor L2 are spirally wound in the center of the receiving end magnetic core.

[0011] Preferably, the first current doubling inductor L1 is composed of the same first sub-coil L a and the second sub-coil L b The second current doubling inductor L2 is composed of the same third sub-coil L c and the fourth sub-coil L d Connected in series.

[0012] Preferably, the first sub-coil (L a ), the second sub-coil (L b ), the third sub-coil (L c ) or the fourth sub-coil (L d ) is set according to the following principle: Under the premise of ensuring the output power remains unchanged, the current doubler inductor (LB ) volume and weight.

[0013] Preferably, the secondary resonant network adopts an LCC compensation network; the primary D-type coil L P The connected primary side resonant network adopts LCC type compensation network.

[0014] The present invention also provides a WPT system, the key of which is to adopt the above-mentioned magnetic integrated coupling mechanism to improve the power density of the WPT system.

[0015] Specifically, the WPT system includes a transmitter and a receiver, wherein the transmitter includes a DC power supply U connected in sequence. dc , high frequency inverter, primary compensation network, the primary D-type coil L P The receiving end includes the secondary D-type coil L connected in sequence S , secondary side resonant network, the current doubler inductor L B , the full-bridge rectifier circuit, filter capacitor C and load resistor R L .

[0016] Preferably, both the primary side compensation network and the secondary side compensation network adopt LCC type compensation networks.

[0017] The magnetic integrated coupling mechanism and WPT system provided by the present invention for improving the power density of the WPT system are designed by magnetic integration of the magnetic coupling mechanism, specifically, the secondary side D-type coil L S A current-doubling inductor L is set in the hollow area B , and improve the circuit topology, specifically by adding the current-doubling inductor L B The first current-doubling inductor L1 and the second current-doubling inductor L2 are divided into two coils and connected to the full-bridge rectifier circuit at the receiving end of the WPT system. This ensures that the current in the two coils is always positive, thereby achieving the corresponding current-doubling effect, improving the power density of the system, reducing the weight of the vehicle-mounted end, and by designing the inductance value of the current-doubling coil, the ripple of the output voltage can be reduced while ensuring that the output power remains unchanged. The current-doubling rectifier topology of the present invention with the addition of a current-doubling inductor is also applicable to other circuit topologies with the problem of excessive inductance, and has the universal applicability of circuit topologies in wireless transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a structural diagram of a magnetic integrated coupling mechanism for improving the power density of a WPT system provided by an embodiment of the present invention;

[0019] FIG2 is a circuit topology diagram of a WPT system using a first current-doubling inductor L1 and a second current-doubling inductor L2 provided in an embodiment of the present invention;

[0020] FIG. 3 is a circuit diagram of a first sub-coil L provided in an embodiment of the present invention. a , the second sub-coil L b , the third sub-coil L c , the fourth sub-coil L d Circuit topology diagram of the WPT system;

[0021] FIG4 is a diagram showing the mutual inductance relationship of a segmented current-doubling inductor provided in an embodiment of the present invention;

[0022] FIG5 is a circuit output ripple diagram before optimization (corresponding to the circuit topology diagram of FIG2 ) provided in an embodiment of the present invention;

[0023] FIG6 is a diagram of the output ripple of the circuit after optimization (corresponding to the circuit topology diagram of FIG3 ) provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings. The embodiments are provided for illustrative purposes only and are not to be construed 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 protection of the present invention. Many changes may be made to the present invention without departing from the spirit and scope of the present invention.

[0025] In order to improve the system output power on the basis of meeting the lightweight requirements of the receiving end, the embodiment of the present invention provides a magnetic integrated coupling mechanism for improving the power density of the WPT system. As shown in the structural diagram of Figure 1, the magnetic integrated coupling mechanism includes a primary D-type coil L P , secondary side D-type coil L S , and the D-type coil L located on the secondary side S The current-doubling inductor L in the hollow area B Referring to the circuit topology diagram of the magnetic integrated coupling mechanism in Figure 2, the current-doubler inductor L B It includes the same first current doubling inductor L1 and second current doubling inductor L2; the first current doubling inductor L1 and the second current doubling inductor L2 are connected to the full-bridge rectifier circuit at the receiving end of the WPT system, which can ensure that the current in the first current doubling inductor L1 and the second current doubling inductor L2 is always positive.

[0026] As shown in Figure 2, the full-bridge rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The first output end of the secondary resonant network of the WPT system is connected to the first current doubling inductor L1 and then to the positive end of the first diode D1. The negative end of the first diode D1 is connected to the load resistor R L The second output end of the secondary resonant network is connected to the second current doubling inductor L2 and then to the positive end of the second diode D2. The negative end of the second diode D2 is connected to the load resistor R LOne end of the third diode D3 is forward connected to the load resistor R L The fourth diode D4 is connected in the forward direction between the load resistor R L The secondary resonant network uses an LCC compensation network (inductor L T2 , capacitor C T2 , capacitor C S ); Primary D-type coil L P The primary resonant network connected uses an LCC compensation network (inductor L T1 , capacitor C T1 , capacitor C P ).

[0027] As shown in FIG1 , the magnetic integrated coupling mechanism also includes a secondary side D-type coil L S The receiving end magnetic core is arranged in layers, and the first current-doubling inductor L1 and the second current-doubling inductor L2 are spirally wound in the center of the receiving end magnetic core.

[0028] The receiving end magnetic core size designed by the present invention is 33*33*0.5cm, and the secondary side D-shaped coil L S The outer diameter is 32cm, the number of winding turns is 18, the wire diameter is 0.5cm, the system input voltage is 700V, the coupling distance is 16cm, the transmitter circuit parameters adopt the GB / T38775.7 standard, and other circuit parameters can be obtained according to the LCC-LCC circuit tuning, so they are not explained here.

[0029] Added current doubler inductor L B The full-bridge rectifier circuit is called a current doubler rectifier circuit. In order for the current doubler rectifier circuit to achieve the current doubler effect, the following conditions must be met:

[0030] 1. Working suppression conditions of ineffective rectification pure inductance circuit:

[0031] L is L1 or L2, w=2πf is the system operating angular frequency, and f is the system operating frequency.

[0032] 2. Due to the output characteristics of the current-doubling rectifier circuit, to ensure that the current in L1 or L2 is always positive, the inductance value must be large enough to ensure a small inductor ripple; at the same time, ensure that the low current in the two filter inductors changes equally.

[0033] Therefore, the current-doubling inductors L1 and L2 are designed to be equal in this example and can be calculated using the following formula:

[0034] Where D is the primary inverter duty cycle of the WPT system, which can be 0.45, and U Lis the load voltage (reference value), f is the system operating frequency, △U L is the output voltage ripple (reference value).

[0035] Common receiving end coupling structure (receiving coil L S The bottom is covered with a layer of magnetic core): transmitter inductance: 47.39uH, receiver inductance: 113.83uH, receiver coil L S With the transmitting coil L P Mutual inductance: 12.22uH; Coupling structure of the present invention: transmitting end inductance: 47.389uH, receiving end inductance: 118.45uH, receiving end coil L S Between the transmitting coil L P The mutual inductance is 13.315uH. It can be seen that after adding the current doubler inductor, the mutual inductance between the transmitting and receiving coils is significantly improved. Therefore, the design of the current doubler inductor of the present invention can improve the mutual inductance of the coupling mechanism.

[0036] According to the normal working conditions of the current doubler rectifier, the ideal current doubler inductor is infinite. However, in application, the practical feasibility of large inductance must be considered. To solve the problem of the current doubler inductor being too large, the present invention optimizes the current doubler inductor by winding it in a "segmented" manner. That is, the first current doubler inductor L1 is composed of the same first sub-coil L a and the second sub-coil L b The second current doubling inductor L2 is composed of the same third sub-coil L c and the fourth sub-coil L d The proposed new coupling mechanism utilizes the strong coupling characteristics of two smaller inductors to replace a large inductor, which is more in line with practical needs. Furthermore, integrating the segmented inductor into the magnetic core of the receiver solves the problem of excessively large inductors in circuit topologies and fully utilizes the remaining magnetic core in the middle of the receiver, reducing the weight and volume of the secondary side and improving the system's power density. The proposed receiver and corresponding circuit topology are shown in Figure 3.

[0037] As shown in Figure 3, L a ~L d There is a coupling relationship between the four inductors, where L a With L b It is a strong coupling relationship with L c and L d The relationship between the four current-doubling inductors is shown in Figure 4. a With L b The strong coupling mutual inductance between them can greatly reduce the inductance of the current doubler inductor, and use L a With L c and L dThe weak coupling relationship between them can reduce the output voltage ripple to a certain extent. The receiving end magnetic core size designed in this invention is 33*33*0.5cm, the receiving coil outer diameter is 32cm, the number of receiving end winding turns is 18, the coil wire diameter is 0.5cm, the input voltage is 700V, the coupling distance is 16cm, and the transmitting end circuit parameters adopt the GB / T38775.7 standard. Other circuit parameters can be obtained by LCC-LCC circuit tuning and are therefore not elaborated here.

[0038] Before optimization, the parameters of the current-doubler inductor coils L1 and L2 are both 250uH. The optimized parameters L after the integrated "segmented" inductor series connection are adopted. a With L b The inductance is 74.59uH. Under the premise of ensuring the output power remains unchanged, the volume and weight of the current doubler inductor are reduced as much as possible. According to the circuit output requirements and comsol simulation results, the number of turns is 6, and the inductance is 74.59uH. Compared with the circuit before optimization, the inductance is reduced by 40.33%. The number of turns of each current doubler inductor coil is 6 turns. a With L b The distance between them is 2 cm, and from Figure 4 and the comsol simulation results, we can get L a , L b , L c and L d The mutual inductance matrix is ​​as follows:

[0039] The circuit simulation results before optimization showed an output power of 22056.9115W and an efficiency of 92.20%. Substituting the mutual inductance matrix into the optimized circuit, the simulation results show an output power of 22363.6810W and an efficiency of 93.18%. After the circuit stabilizes, the output ripple of the circuit before optimization is shown in Figure 5, with a maximum voltage of 566.701V, a minimum voltage of 565.948V, and a voltage ripple of 0.753V. The output voltage ripple of the optimized circuit is shown in Figure 6, with a maximum voltage of 570.298V, a minimum voltage of 570.177V, and a voltage ripple of 0.121V. This shows that the optimized circuit achieves better output power and efficiency than the original circuit, while reducing the current-doubling inductor by 40.33%, and the voltage ripple is smaller than before optimization.

[0040] Based on the above magnetic coupling mechanism, an embodiment of the present invention further provides a WPT system using the magnetic integrated coupling mechanism. The system uses a first current-doubling inductor L1 and a second current-doubling inductor L2. The circuit topology is shown in FIG2. The first sub-coil L a , the second sub-coil L b , the third sub-coil L c , the fourth sub-coil Ld The circuit topology is shown in Figure 3. The WPT system has been described in detail above and will not be repeated here.

[0041] In addition to the circuit topology shown in this embodiment, the current-doubling rectification topology with a current-doubling inductor added in the embodiment of the present invention is also applicable to other circuit topologies with the problem of excessive inductance, and has the universal applicability of circuit topologies in wireless transmission.

[0042] In summary, the magnetic integrated coupling mechanism and WPT system for improving the power density of the WPT system provided by the embodiment of the present invention are designed by magnetic integration of the magnetic coupling mechanism, specifically, the secondary side D-type coil L S A current-doubling inductor L is set in the hollow area B , and improve the circuit topology, specifically by adding the current-doubling inductor L B The first current doubling inductor L1 and the second current doubling inductor L2 are divided into two coils and connected to the full-bridge rectifier circuit at the receiving end of the WPT system. This can ensure that the current in the two coils is always positive, thereby achieving the corresponding current doubling effect, improving the power density of the system, and reducing the weight of the vehicle-mounted end. By designing the inductance value of the current doubling coil, the output voltage ripple can be reduced while ensuring that the output power remains unchanged.

[0043] 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 considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A magnetic integrated coupling mechanism for improving the power density of a WPT system, characterized in that: Including the primary D-type coil (L P )、Secondary D-type coil (L S ), and the secondary side D-type coil (L S ) The current-doubler inductor (L B ), the current-doubling inductor (L B ) comprises an identical first current doubling inductor (L1) and a second current doubling inductor (L2); the first current doubling inductor (L1) and the second current doubling inductor (L2) are connected to a full-bridge rectifier circuit at a receiving end of a WPT system, so as to ensure that the current in the first current doubling inductor (L1) and the second current doubling inductor (L2) is always positive.

2. According to claim 1, the magnetic integrated coupling mechanism for improving the power density of the WPT system is characterized in that: The full-bridge rectifier circuit comprises a first diode (D1), a second diode (D2), a third diode (D3), and a fourth diode (D4); the first output end of the secondary resonant network of the WPT system is connected to the first current doubling inductor (L1) and then to the positive end of the first diode (D1); the negative end of the first diode (D1) is connected to a load resistor (R L ), the second output end of the secondary resonant network is connected to the second current doubling inductor (L2) and then connected to the positive end of the second diode (D2), and the negative end of the second diode (D2) is connected to the load resistor (R L ), the third diode (D3) is forwardly connected to the load resistor (R L ) and the first output terminal of the secondary resonant network, the fourth diode (D4) is forwardly connected to the load resistor (R L ) between the other end of the secondary resonant network and the second output end of the secondary resonant network.

3. The magnetic integrated coupling mechanism for improving the power density of the WPT system according to claim 2, characterized in that: The inductance L1 of the first current-doubling inductor (L1) and the inductance L2 of the second current-doubling inductor (L2) satisfy: Where D is the primary inverter duty cycle of the WPT system, U L is the load voltage, C is the resistor connected between the full-bridge rectifier circuit and the load resistor (R L ), f is the system operating frequency, △U L is the output voltage ripple.

4. The magnetic integrated coupling mechanism for improving the power density of the WPT system according to claim 2, characterized in that: The magnetic integrated coupling mechanism also includes a secondary side D-type coil (L S ) layers, the first current-doubling inductor (L1) and the second current-doubling inductor (L2) are spirally wound in the center of the receiving-end magnetic core.

5. The magnetic integrated coupling mechanism for improving the power density of the WPT system according to claim 4, characterized in that: The first current doubling inductor (L1) is composed of the same first sub-coil (L a ) and the second sub-coil (L b ) are connected in series, the second current doubling inductor (L2) is composed of the same third sub-coil (L c ) and the fourth sub-coil (L d ) are connected in series.

6. The magnetic integrated coupling mechanism for improving the power density of the WPT system according to claim 5, characterized in that: The first sub-coil (L a ), the second sub-coil (L b )、the third sub-coil (L c ) or the fourth sub-coil (L d ) is set according to the following principle: Under the premise of ensuring that the output power remains unchanged, the current-doubler inductor (L B ) volume and weight.

7. The magnetic integrated coupling mechanism for improving the power density of the WPT system according to claim 6, characterized in that: The secondary resonant network adopts an LCC compensation network; the primary D-type coil (L P )The primary side resonant network connected adopts an LCC type compensation network. 8.WPT system, characterized in that: A magnetic integrated coupling mechanism for improving the power density of a WPT system as described in any one of claims 1 to 7 is adopted.

9. The WPT system according to claim 8, characterized in that: It includes a transmitting end and a receiving end, wherein the transmitting end includes a DC power supply (U dc ), high frequency inverter, primary compensation network, the primary D-type coil (L P ), the receiving end includes the secondary side D-type coils (L S ), the secondary resonant network, the current doubler inductor (L B ), the full-bridge rectifier circuit, the filter capacitor (C) and the load resistor (R L ).

10. The magnetic integrated coupling mechanism for improving the power density of the WPT system according to claim 9, characterized in that: The primary side compensation network and the secondary side compensation network both adopt LCC type compensation networks.

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