A wireless power transfer compensation topology and system with compact receiving end

Abstract

The application discloses a wireless power transmission compensation topology with a compact receiving end, comprising a direct current power supply, an inverter circuit, a primary side compensation circuit, a transmitting and receiving coil, a rectification filter circuit and a load. The primary side compensation circuit is connected with the alternating current side of the inverter circuit and has two branches: one branch is a parallel compensation inductor, and the other branch is a series connection of the transmitting coil and a primary side compensation capacitor; the secondary side receiving coil is directly connected with the two ends of the alternating current side of the rectification circuit. Through parameter design, the compensation topology can realize constant current output independent of the load, eliminate the input side reactive power and realize zero voltage opening of the inverter. The secondary side of the compensation topology only comprises the necessary receiving coil and the rectification filter circuit, and the inductance and the number of turns of the receiving coil can be designed to be very small, so that the cost, the volume and the weight of the receiving end are greatly reduced, the compact receiving end is formed, and therefore the application has practical significance and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology, and specifically relates to a wireless power transmission compensation topology with a compact receiver. Background Technology

[0002] Wireless power transfer technology enables contactless energy transfer. Compared to traditional plug-in charging technology, wireless power transfer offers advantages such as safety, reliability, low maintenance, resilience to inclement weather, and ease of operation. Inductive wireless power transfer relies on electromagnetic induction between the transmitting and receiving coils of a loosely coupled transformer to transfer energy. To compensate for the significant leakage inductance of the loosely coupled transformer, passive compensation circuits are typically added to both the primary and secondary sides, thereby reducing reactive power on the circuit input side and improving efficiency.

[0003] Currently, the existing compensation circuits mainly include four basic compensation topologies: S / S (series / series), S / P (series / parallel), P / S (parallel / series), and P / P (parallel / parallel), as well as higher-order compensation topologies such as SP / S, S / SP, LCL, LCC, and CLC. Under traditional design methods, the four basic compensation structures can provide load-independent voltage gain or current transconductance, and the reactive power on the input side is almost completely eliminated.

[0004] Advanced compensation structures such as SP / S combine the characteristics of S / S and P / S, creating output power that is insensitive to coil offset. LCL compensation, used on the primary side, can provide load-independent transmitting coil current, and the resonance condition is unaffected by coil offset. LCC compensation improves upon LCL compensation, reducing the size of the compensation inductor while retaining the circuit characteristics. CLC compensation and other advanced compensations offer greater design freedom and can be used in constant voltage / constant current battery charging applications or to address output fluctuations caused by coil offset.

[0005] In existing compensation structures, the compensation circuit design does not fully consider the compactness and power density of the secondary receiver. Besides the necessary receiving coil, the receiver also includes compensation capacitors and inductors, leaving considerable room for optimization of the receiver's power density. In practical applications of wireless power transfer systems, the compactness and power density of the system receiver are crucial due to the following two characteristics:

[0006] 1. In practical applications, only a small number of energy transmitting devices are typically installed, while a large number of energy receiving terminals are present. Examples include wireless charging for smart mobile devices, electric vehicles, drones, and electric bicycles. In these scenarios, a single charging station or charging pad often needs to charge a large number of electric vehicles or different smart mobile devices at different times.

[0007] 2. Energy receiving terminals are mostly mobile objects, while energy transmitting terminals are generally located in a fixed position. Therefore, the limitations on cost, size, and weight of the receiving terminal are more stringent. In summary, the compactness of the secondary receiving side is particularly important.

[0008] To address the above two issues, the papers "Modeling and analysis of series-none compensation for wireless power transfer systems with a strong coupling" (vol. 34, no. 2, pp. 1209–1215, Feb. 2019) and "A high-power wireless charging system using LCL-N topology to achieve a compact and low-cost receiver" (vol. 35, no. 1, pp. 131-137, Jan. 2020) published in IEEE Transactions on Power Electronics introduce S / N compensation structures and LCL / N compensation structures, respectively. Both compensation methods achieve a compact receiver on the secondary side, with only a rectifier bridge and a receiving coil present. However, S / N compensation only provides a constant voltage output characteristic independent of the load, making it unsuitable for charging applications with battery loads. Furthermore, it exhibits a large inductive phase angle on the input side, resulting in a low inverter power factor. LCL-N compensation lacks both load-independent constant voltage and constant current output characteristics, and cannot achieve zero phase angle and unity power factor in the inverter. Currently, in most applications of IPT technology, battery loads are used, making load-independent constant current output a necessary characteristic. Achieving zero phase angle and unity power factor in the inverter minimizes device stress and losses, thereby improving energy transfer efficiency.

[0009] In summary, considering the practical applications of wireless power transmission today, current conventional compensation circuit designs do not adequately consider the compactness and power density of the secondary receiving side. Existing techniques that address the compactness of the secondary receiving side cannot achieve zero phase angle and unity power factor in the inverter, nor do they provide load-independent constant current output characteristics for battery loads. Summary of the Invention

[0010] In view of the above, the object of the present invention is to propose a wireless power transfer compensation topology with a very compact receiver. The receiver of the present invention only includes the necessary receiving coil and rectifier filter circuit, and the receiving coil can be designed with a small inductance and a small number of turns as much as possible, further reducing the weight, size, and cost of the receiver. Furthermore, this compensation also has load-independent constant current output capability, can eliminate reactive power on the input side, and naturally achieves zero-voltage turn-on of the inverter.

[0011] To achieve the aforementioned objectives, the present invention adopts the following technical solution:

[0012] A wireless power transfer compensation topology with a compact receiver includes: a DC power supply, an inverter circuit, a primary-side parallel compensation inductor L1, and a primary-side series compensation capacitor C. p Primary transmitting coil L p Secondary receiving coil L s 1. Rectifier and filter circuit and load;

[0013] The DC side of the inverter circuit is connected to the DC power supply to convert the DC output of the DC power supply into high-frequency AC. The two ends of the AC side of the inverter circuit are connected to the two ends of the primary side in parallel with the compensation inductor L1.

[0014] The primary-side series compensation capacitor C p One end is connected to one end of the compensation inductor L1 in parallel with the primary side, and the compensation capacitor C is connected in series with the primary side. p The other end is connected to the primary side transmitting coil L p One end is connected to the primary-side transmitting coil L. p The other end is connected to the other end of the primary-side parallel compensation inductor L1;

[0015] The primary-side transmitting coil L p and secondary receiving coil L s Energy is transferred between them via electromagnetic coupling, with the secondary receiving coil L... s Both ends are directly connected to the AC side of the rectifier circuit, and the DC side of the rectifier circuit is connected to the load after output filtering.

[0016] This invention achieves a compact receiver from the perspective of compensation circuit design in the following two aspects:

[0017] 1. From the perspective of circuit structure: minimize the number of components in the secondary receiving side compensation circuit, and only retain the necessary receiving coil.

[0018] 2. From the perspective of parameter design: Design a receiving coil with the smallest possible inductance to reduce the size, volume and weight of the receiving coil.

[0019] Furthermore, the inverter circuit adopts an inverter structure such as a half-bridge inverter structure, a full-bridge inverter structure, or a push-pull inverter structure.

[0020] Furthermore, the primary-side transmitting coil or the secondary-side receiving coil is composed of a magnetic core and a power transmission coil wound with wire, wherein the magnetic core is made of a magnetically conductive material.

[0021] Furthermore, the primary-side parallel compensation inductor L1 and the primary-side series compensation capacitor C p Primary transmitting coil L p Secondary receiving coil L s The parameters of the mutual inductance M of the coupled coils are designed to satisfy the following resonance condition:

[0022] Condition 1:

[0023] Condition 2: L1L s =M 2 ;

[0024] Where ω is the inverter switching angular frequency.

[0025] Furthermore, the primary-side parallel compensation inductor L1 can be finely adjusted after the parameter design is completed, thereby generating a slightly inductive or capacitive input impedance angle without changing the power characteristics.

[0026] Furthermore, a DC blocking capacitor can be connected in series on the parallel branch where the primary-side parallel compensation inductor L1 is located, or a series DC blocking capacitor can be added between the AC side of the inverter circuit and the connection point of the primary-side compensation circuit to eliminate the DC current component on this parallel branch.

[0027] This invention proposes a wireless power transfer compensation topology with a compact receiver. Unlike traditional compensation structures, this invention retains only the necessary coils and rectifier / filter circuits on the secondary receiver side. No compensation circuit is configured on the secondary side; output characteristics and reactive power compensation are entirely achieved through primary-side compensation. Therefore, the output characteristics of this invention are consistent with traditional S / S compensation structures, but the receiver side is significantly simplified.

[0028] The significant advantages of this invention lie in its focus on the power density and compactness of the secondary-side receiver. It proposes a compensation topology that replaces existing topologies and offers a highly compact receiver. The primary-side compensation circuit is connected to the AC side of the inverter circuit and has two branches: one branch consists of a parallel compensation inductor, and the other branch is a series connection between the transmitting coil and the primary-side compensation capacitor. The secondary-side receiving coil is directly connected to both ends of the rectifier circuit's AC side. Through parameter design, the proposed compensation topology achieves load-independent constant current output, eliminates reactive power on the input side, and enables zero-voltage turn-on of the inverter. This compensation topology's secondary side only includes the necessary receiving coil and rectifier / filter circuit, and the receiving coil inductance and number of turns can be designed to be very small, thereby significantly reducing the cost, size, and weight of the receiver, resulting in a compact receiver.

[0029] Compared with existing wireless power transmission, the practical application of this invention has two main characteristics:

[0030] 1) One transmitter can charge dozens or hundreds of receivers, and the number of receivers is far greater than the number of transmitters;

[0031] 2) The receiver is located in a mobile device while the transmitter is located in a fixed location.

[0032] The wireless power transmission system with a compact receiver topology proposed in this invention ensures that the secondary side has a compact receiver while providing load-independent constant current output and achieving zero phase angle on the input side. The compact, low-cost, small-volume, and lightweight receiver has practical significance and good application prospects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the compact receiver wireless power transmission topology of the present invention.

[0034] Figure 2 This is a schematic diagram of the equivalent circuit model of the wireless power transmission structure of the present invention.

[0035] Figure 3 This is a schematic diagram of the equivalent circuit model of the wireless power transmission structure of the present invention, which converts the self-inductance of the secondary coil to the primary coil.

[0036] Figure 4 shows the AC side current of the inverter circuit, the current of the primary-side parallel compensation inductor, the ds terminal voltage of the power device, and the drive signal waveforms under different loads.

[0037] Among them: Figure 4(a) is the waveform diagram at 1 / 4 of the rated power, Figure 4(b) is the waveform diagram at 1 / 2 of the rated power, and Figure 4(c) is the waveform diagram at the rated power. In the figures, v... ds and v gs Here are the ds-terminal voltage and drive voltage of the power device; in the figure, ip This represents the AC side current of the inverter; i in the diagram L1 The current flowing through the parallel compensating inductor on the primary side; the positive direction of the above current is as follows: Figure 2 Middle I p and I L1 As shown.

[0038] Figure 5 shows the AC side current, receiving coil current, and receiving terminal output DC current of the rectifier circuit under different loads; where: Figure 5(a) is the waveform diagram under 1 / 4 rated power, Figure 5(b) is the waveform diagram under 1 / 2 rated power, and Figure 5(c) is the waveform diagram under rated power. (The text then abruptly switches to a different topic: u...) s and i s The AC side voltage and coil current of the rectifier circuit are shown in the following positive directions: Figure 2 Middle U s and I s As shown in the figure. I o The receiver outputs DC current, in the positive direction as follows: Figure 2 . Detailed Implementation

[0039] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] The following combination Figures 1 to 3 The working principle of the wireless power transmission compensation topology with a compact receiver proposed in this invention will be explained, such as... Figure 1 As shown, the compensation topology in this example includes a DC power supply 1, an inverter circuit 2, a compensation circuit 3, a rectifier and filter circuit 4, and a load 5.

[0041] Figure 2 This is a simplified compensation circuit using fundamental frequency analysis and a loosely coupled transformer T-model. It includes a primary-side parallel compensation inductor L1 and a primary-side series compensation capacitor C. p Primary transmitting coil L p and secondary receiving coil L s The mutual inductance between the transmitting and receiving coils is denoted by M. Some circuit parameters are defined as follows:

[0042] V in DC power supply input voltage;

[0043] V o I o : Load-side DC output voltage, load-side DC output current;

[0044] R o The equivalent load resistance on the DC side after filtering by the rectifier circuit;

[0045] R eq: Equivalent load resistance on the AC side of the rectifier circuit;

[0046] U p : The effective value of the fundamental voltage on the AC side of the inverter circuit;

[0047] I p : The effective value of the fundamental current on the AC side of the inverter circuit;

[0048] U s : The effective value of the fundamental voltage on the AC side of the rectifier circuit;

[0049] I s : The effective value of the fundamental current on the AC side of the inverter circuit;

[0050] L p L s C p L1: Inductance and capacitance at corresponding positions in the primary and secondary side compensation circuit;

[0051] M, k: Mutual inductance and coupling coefficient of a loosely coupled transformer, their relationship is as follows:

[0052] According to the fundamental frequency analysis method, the relationship between the effective values ​​of the AC side voltage and current and the DC voltage and current of the inverter circuit and rectifier circuit is as follows:

[0053]

[0054] The equivalent load resistance of the AC and DC sides of the rectifier circuit is

[0055]

[0056] Figure 2 In the loosely coupled transformer T model, a T-shaped gyroscope is naturally formed, therefore the self-inductance L of the receiving coil is... s This can be equivalently converted back to before the T-type gyroscope; the equivalent circuit after conversion is as follows: Figure 3 C eq The equivalent series capacitance is calculated under the following conditions:

[0057]

[0058] Based on the equivalent circuit Figure 3 Only the self-inductance L of the transmitting coil is needed. p The compensation capacitor C connected in series with the primary side p Series resonance, primary side parallel compensation inductor L1 and equivalent parallel capacitance C eq In parallel resonance, only one T-type gyroscope remains in the compensation circuit. The resonance condition is:

[0059]

[0060] Substituting into (3), the resonance condition simplifies to:

[0061]

[0062] At this point, the circuit output characteristics are consistent with those of traditional S / S compensation, and the output current transconductance G is:

[0063]

[0064] The equivalent input impedance Z of the inverter circuit in for:

[0065]

[0066] As can be seen from equations (6) and (7), the compensation structure of the present invention has a constant current output capability independent of the load, and the input equivalent impedance is purely resistive with a power factor close to 1. In addition, the primary-side parallel compensation inductor L1 is directly connected in parallel to the inverter output side, and the current on it is actually a triangular wave. The high-order harmonic components contained in the triangular wave current can naturally provide the inverter with the turn-off current, thereby achieving zero-voltage turn-on.

[0067] This example designs an experimental prototype with a rated power of 1kW, an input DC voltage of 200V, and a constant output DC current of 5A. A large-value DC blocking capacitor is connected in series on the primary-side parallel compensating inductor branch to isolate the DC current component in the parallel inductor branch. If this DC blocking capacitor is not connected in series, the DC current component can also be eliminated by using control methods.

[0068] The parameters were designed based on the following resonance conditions 1 and 2:

[0069] Primary-side parallel compensation inductor L1, primary-side series compensation capacitor C p Primary transmitting coil L p Secondary receiving coil L s The parameters of the mutual inductance M of the coupled coils are designed to satisfy the following resonance condition:

[0070] Condition 1:

[0071] Condition 2: L1L s =M 2 .

[0072] The primary-side parallel compensation L1 is slightly reduced to facilitate zero-voltage turn-on of the inverter. The parameters of the designed compensation structure are as follows:

[0073] Vin Io L1 Cp Lp Ls M k 200V 5A 60.8μH 8.22nF 427μH 47.7μH 60.7μH 0.42

[0074] In the above design parameters, the inductances of the transmitting and receiving coils are 427μH and 47.7μH, respectively. In actual winding, the transmitting coil has 13 turns and the receiving coil has 4 turns.

[0075] It can be seen that the receiving coil can be designed with a small inductance and a small number of turns. On the one hand, this is more conducive to the compactness of the receiving end; on the other hand, according to equation (5), L s A smaller value will result in a larger value for L1, which will reduce the current flowing through the compensation inductor L1, thereby further reducing the current in the transmitting coil and improving system efficiency.

[0076] The effects of the present invention are described below using actual experimental results and waveforms. Figures 4 and 5 show the experimental waveforms of the wireless power compensation topology with a compact receiver in this example.

[0077] The waveform in Figure 4 includes the inverter input current i. p The current i flowing through the primary-side parallel compensating inductor L1 and the terminal voltage v of the power device SiCMOSFET ds and driving voltage v gs Figure 4(a) shows the waveform at 1 / 4 of the rated power, Figure 4(b) shows the waveform at 1 / 2 of the rated power, and Figure 4(c) shows the waveform at the rated power.

[0078] Experimental results show that the AC side voltage and current of the compensated topology inverter of this invention are nearly in phase under different power levels, meaning the inverter always maintains a near unity power factor. Furthermore, the inverter can achieve zero-voltage turn-on at different output power levels.

[0079] The waveform in Figure 5 includes the AC side voltage u of the rectifier bridge. s , rectifier bridge AC side current i s and DC output current I o Figure 5(a) shows the waveform at 1 / 4 of the rated power, Figure 5(b) shows the waveform at 1 / 2 of the rated power, and Figure 5(c) shows the waveform at the rated power.

[0080] Experimental results show that the DC output current of the compensated topology of this invention ranges from 5.1A to 5.0A at different power levels, which is basically the set constant current output value. These experimental results demonstrate that the output characteristics of this invention are consistent with the design.

[0081] The compensation topology of this invention is consistent with traditional S / S compensation; however, the receiver of this invention only contains the necessary receiving coil and rectifier filter circuit, and the inductance and number of turns of the receiving coil are relatively small. This design ensures that the receiver is as compact, low-cost, small in size, and lightweight as possible. Based on these advantages, this topology has great potential for practical applications.

[0082] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A wireless power transmission compensation topology with a compact receiver, characterized in that, include: DC power supply, inverter circuit, primary-side parallel compensation inductor L 1. Primary-side series compensation capacitor C p Primary-side transmitting coil L p Secondary receiving coil L s 1. Rectifier and filter circuit and load; The DC side of the inverter circuit is connected to a DC power supply to convert the DC output of the DC power supply into high-frequency AC. Compensating inductors are connected in parallel with the primary side of the AC side of the inverter circuit. L 1. Connect both ends; The primary-side series compensation capacitor C p One end is connected in parallel with the primary side to compensate for the inductance. L One end of 1 is connected, and a compensation capacitor is connected in series on the primary side. C p The other end is connected to the primary side transmitting coil L p One end is connected to the primary-side transmitting coil. L p The other end is connected in parallel with the primary side to compensate for the inductance. L The other end of 1 is connected; The primary-side transmitting coil L p and secondary receiving coil L s Energy is transferred between them via electromagnetic coupling, with the secondary receiving coil... L s Both ends are directly connected to the AC side of the rectifier circuit, and the DC side of the rectifier circuit is connected to the load after output filtering. The primary-side parallel compensation inductor L 1. Primary-side series compensation capacitor C p Primary-side transmitting coil L p Secondary receiving coil L s and mutual inductance of coupled coils M The parameter design satisfies the following resonance condition: Condition 1: ; Condition 2: ; Where ω is the inverter switching angular frequency.

2. The wireless power transmission compensation topology according to claim 1, characterized in that: The inverter circuit adopts a half-bridge inverter structure, a full-bridge inverter structure, or a push-pull inverter structure.

3. The wireless power transmission compensation topology according to claim 1, characterized in that: The primary-side transmitting coil or the secondary-side receiving coil consists of a power transmission coil made of a magnetic core and wire.

4. The wireless power transmission compensation topology according to claim 3, characterized in that: The magnetic core uses a magnetically conductive material.

5. The wireless power transmission compensation topology according to claim 1, characterized in that: The primary-side parallel compensation inductor L A DC blocking capacitor is connected in series on the parallel branch where 1 is located to eliminate the DC current component in the parallel inductor branch.

6. The wireless power transmission compensation topology according to claim 1, characterized in that: A series DC blocking capacitor is added between one end of the inverter circuit on the AC side and the connection point of the primary side compensation circuit to eliminate the DC current component on the parallel inductor branch.

7. A wireless power transmission system, characterized in that: The wireless power transmission compensation topology described in any one of claims 1-6 is adopted.

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