Impedance-adjustable inverter source topology and adjusting method suitable for three-phase wireless power supply system

Abstract

The application provides an impedance-adjustable inverter source topology and adjusting method suitable for a three-phase wireless power supply system, the topology comprises a three-phase full-bridge inverter circuit and an impedance adjusting network; the three-phase full-bridge inverter circuit is connected with the impedance adjusting network. The method can effectively solve the emission current balance problem of the three-phase LCC compensation topology, and can also adjust the output impedance to change the load characteristics in other application scenarios.

Description

Technical Field

[0001] This invention relates to the field of wireless power supply technology, and in particular to an impedance-adjustable inverter source topology and adjustment method suitable for three-phase wireless power supply systems. Background Technology

[0002] Wireless power transfer technology is increasingly integrated into our lives due to its advantages such as safety, convenience, and intelligence. A traditional wireless power supply system structure includes a high-frequency inverter, a compensation network, a converter containing a coupling mechanism and a receiver. Compared to single-phase topology, three-phase topology offers higher output power. When applied in dynamic wireless power supply systems, three-phase topology boasts zero output fluctuation, effectively solving the problem of power fluctuation during receiver movement in applications such as electric vehicles.

[0003] The three-phase topology using an LCC compensation network is as follows: Figure 1 As shown, it can keep the current (iA, iB, iC) amplitude of the transmitting coil or rail constant and not change with different loads, effectively keeping the magnetic field of the transmitting coil of the coupling mechanism constant. Due to its fewer compensation devices and strong adaptability of the coupling mechanism, it is the most common second-order T-type topology in wireless power supply systems.

[0004] To ensure stable induced voltage on the mobile receiving side, the three-phase transmitting coil currents need to be symmetrical, meaning they have the same amplitude, and any two phases A, B, and C must be 120° out of phase. The LCC-compensated three-phase topology has three compensation inductors connected in series with the output of the three-phase inverter. The output current is related to the inductance value of each inductor. The relationship between the transmitting coil current of each phase and the corresponding inductance value is as follows:

[0005]

[0006] Where α = A, B, C, ω is the system's fundamental frequency, u α This represents the effective value of the fundamental frequency of the output voltage of each phase of the inverter source.

[0007] To reduce the content of higher harmonics, the three-phase inverter needs to be symmetrically controlled, that is, it needs to meet the following requirements.

[0008]

[0009] U m This represents the fundamental amplitude of the three-phase output voltage.

[0010] Therefore, in order to make the three-phase transmitting current of the system symmetrical, it is necessary to ensure that the series inductance at the front end of the T network is the same, that is, L needs to be... fA =L fB =L fCHowever, due to limitations in manufacturing processes, inductors are often within ±10% of their nominal values, making it impossible to guarantee the consistency of the selected inductors. Therefore, it is often necessary to add a compensation capacitor to compensate for the inductor deviation. However, there is also a certain deviation between the actual capacitance value and the nominal value of the capacitor. Moreover, in order to match, a large number of capacitors with different capacitance values ​​need to be purchased, which increases the cost significantly. This also brings great difficulties to the selection of capacitors. Summary of the Invention

[0011] The purpose of this invention is to solve the problems in the prior art and to propose an impedance-adjustable inverter source topology and adjustment method suitable for three-phase wireless power supply systems.

[0012] This invention is achieved through the following technical solution: This invention proposes an impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems. The topology includes a three-phase full-bridge inverter circuit and an impedance adjustment network; the three-phase full-bridge inverter circuit is connected to the impedance adjustment network; the three-phase full-bridge inverter circuit includes a capacitor C. DC And 6 switching transistors S1 to S6, the 6 switching transistors are connected in series in pairs and then in parallel with capacitor C. DC The impedance adjustment network comprises three impedance adjustment units connected in parallel. Each impedance adjustment unit includes two switching transistors and one capacitor. The two switching transistors are connected in series and then in parallel with the capacitor.

[0013] Furthermore, the inverter source topology is adjusted by adjusting S1 to S6 such that:

[0014]

[0015] Among them, C SA C SB C SC All are capacitors in the impedance adjustment network; L fA L fB L fC All of these are compensation inductors in a compensation network.

[0016] Furthermore, the compensation network is an LCC compensation network, an S-type compensation network, or an LCL compensation network; the compensation network is connected to the inverter source topology.

[0017] This invention also proposes an adjustment method based on the aforementioned impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems, wherein the adjustment method specifically comprises:

[0018] Adjusted capacitor C STwo reverse switches, S1 and S2, are connected in parallel. During operation, both switches use the same drive, turning on and off simultaneously. The impedance adjustment principle is to adjust the drive duty cycle, causing the equivalent capacitance value to change at the fundamental frequency. It is easy to see that the relationship between the current in capacitor Cs and the drive is:

[0019]

[0020] Where the input current i o =I o sin(ωt+θ);

[0021] The fundamental amplitude of the capacitor current is:

[0022]

[0023] After the switch is turned off, the capacitor current starts from zero, and the integral of the capacitor current between two PWM pulses is zero. During operation, the main circuit current i must be maintained. o The zero-crossing point is the midpoint of the switch's low-level state, from which we can deduce:

[0024]

[0025] The equivalent capacitance Cs′ can be obtained from the following equation.

[0026]

[0027] Therefore, adjusting the duty cycle can change the equivalent capacitance at the base frequency. By adjusting the impedance adjustment switch of each phase, the three-phase inverter source can make formula (1) hold true.

[0028] Let the capacitive reactance regulation capability be G(d), and its functional expression be:

[0029]

[0030] Its varying impedance range is -1 / ωC S ~0;

[0031] For the filter inductor L f The maximum deviation is ±σ, and the required range of adjustment capability is:

[0032]

[0033] Combining equations (2) and (3), the range of the selected capacitor can be obtained as follows:

[0034]

[0035] This invention also proposes an impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems. The topology is connected to an LCC compensation network and includes a three-phase full-bridge inverter circuit and an impedance adjustment network. The three-phase full-bridge inverter circuit is connected to the impedance adjustment network. The three-phase full-bridge inverter circuit includes a capacitor C. DC And 6 switching transistors S1 to S6, the 6 switching transistors are connected in series in pairs and then in parallel with capacitor C. DC The impedance adjustment network comprises two impedance adjustment units connected in parallel. Each impedance adjustment unit includes two switching transistors and one capacitor. The two switching transistors are connected in series and then in parallel with the capacitor. In this topology, the filter inductor with the largest measured three-phase inductance value is connected to the inverter full bridge without passing through the impedance adjustment section. That is, the inductor with the largest inductance value is placed in the LCC compensation network. fc The other two inductors can be placed arbitrarily in the L1 position of the L2 in the L3 compensation network. fa Position and L fb The position of the series-connected capacitive reactance regulating switch, while ensuring the phase meets the control requirements, is such that the duty cycle is adjusted so that the total inductive reactance of the regulated capacitive reactance and the compensation inductor in series is equal to L. fc The sensitivity values ​​are the same.

[0036] The beneficial effects of this invention are:

[0037] 1. In a three-phase wireless power supply system, the compensation topology after the inverter source needs to be symmetrical and identical. The method described in this invention solves the problem of system symmetry imbalance caused by the deviation of passive device parameters in the topology.

[0038] 2. In a three-phase wireless power supply system, it is necessary to ensure that the topology network achieves resonance. However, deviations in parameters will cause the system to be in a skewed state, resulting in a large amount of reactive power. The method described in this invention can adjust the impedance to bring the system back to the resonant state.

[0039] 3. When tuning the topology parameters of a wireless power supply system, it is difficult to obtain the theoretical calculation values ​​of the system compensation capacitor and compensation inductor due to inherent random deviations. However, the method described in this invention can achieve continuous impedance adjustment and accurately obtain the resonance state. Attached Figure Description

[0040] Figure 1 This is a topology diagram of the transmitter circuit of a three-phase wireless power supply system with LCC compensation in the prior art.

[0041] Figure 2 This is a topology diagram of a three-phase inverter with output impedance regulation.

[0042] Figure 3 Schematic diagram of the transmitter circuit for a three-phase wireless power supply system with LCC compensation.

[0043] Figure 4 This is a schematic diagram of an adjustable capacitor circuit.

[0044] Figure 5 This is a key waveform diagram of the adjustable capacitor.

[0045] Figure 6 This is a graph showing the relationship between capacitor gain and drive duty cycle.

[0046] Figure 7 This is a graph showing the relationship between the capacitive reactance adjustment strength and the duty cycle.

[0047] Figure 8 This is a schematic diagram of an LCC three-phase inverter topology embodiment. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Technical Terminology Explanation:

[0050] Wireless power transfer system (WPT)

[0051] Dynamic wireless power transfer system (DWPT)

[0052] Inductive wireless power transfer (IPT)

[0053] Magnetic Coupled Resonant Wireless Power Transfer (MCR-WPT)

[0054] LCC architecture—a commonly used topology network structure for wireless power supply systems.

[0055] To address the difficulties in achieving three-phase symmetry through compensation, this invention proposes a three-phase inverter source topology with impedance regulation capability, such as... Figure 2As shown, this invention effectively solves the transmit current balance problem in three-phase LCC compensation topologies, and can also adjust the output impedance to change load characteristics in other application scenarios. This invention uses the LCC compensation network of a three-phase dynamic wireless power supply system as an example, but it can also be applied to wireless power supply systems using other supplementary networks, such as S-type compensation networks and LCC compensation networks.

[0056] Specifically, this invention proposes an impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems. The topology includes a three-phase full-bridge inverter circuit and an impedance adjustment network; the three-phase full-bridge inverter circuit is connected to the impedance adjustment network; the three-phase full-bridge inverter circuit includes a capacitor C. DC And 6 switching transistors S1 to S6, the 6 switching transistors are connected in series in pairs and then in parallel with capacitor C. DC The impedance regulation network comprises three impedance regulation units connected in parallel. Each impedance regulation unit includes two switching transistors and one capacitor, with the two switching transistors connected in series and then in parallel with the capacitor. This three-phase inverter can have continuously adjustable port impedance. For the three-phase WPT system LCC topology, the impedance regulation control method compensates for the difference in the three-phase topology compensation inductance, making the series impedance of the three-phase LCC topology the same and ensuring symmetrical current in the three-phase transmitting coils.

[0057] The schematic diagram of the proposed three-phase inverter source circuit structure in the transmitter circuit of the LCC-compensated wireless power supply system is shown below. Figure 3 As shown. The circuit includes an inverter full-bridge (C... DC S1 to S6), impedance adjustment network (C SA C SB C SC S A S B S C ), compensating inductor (L fA L fB L fC Parallel compensation capacitors (C1, C2, C3), series compensation capacitors (C... A C B C C ), transmitting coil (L A L B L C The equivalent impedance reflected at the receiving end (Z) RA Z RB Z RC ), compensate network nodes (A, B, C) and neutral points (N, N′).

[0058] To ensure symmetrical three-phase currents in the transmitting coil of a dynamic wireless power supply, the front-end impedance of the compensation network (T-type network) must be identical. However, it is impossible to guarantee that the three compensation inductors used in the system (L...) fA L fB L fC Since they are the same, the inverter source topology described in this invention, by adjusting S1 to S6, makes:

[0059]

[0060] This effectively solves the problem of symmetrical current in the transmitting coil. Among them, C SA C SB C SC All are capacitors in the impedance adjustment network; L fA L fB L fC All of these are compensation inductors in a compensation network.

[0061] This invention also proposes an adjustment method based on the aforementioned impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems, wherein the adjustment method specifically comprises:

[0062] We will analyze a set of adjustable capacitors inside a three-phase inverter source, such as... Figure 4 As shown, the adjusted capacitor C S Two reverse switches, S1 and S2, are connected in parallel. During operation, both switches use the same drive, turning on and off simultaneously. The impedance adjustment principle is to adjust the drive duty cycle, causing the equivalent capacitance value to change at the fundamental frequency. It is easy to see that the relationship between the current in capacitor Cs and the drive is:

[0063]

[0064] Where the input current i o =I o sin(ωt+θ);

[0065] The fundamental amplitude of the capacitor current is:

[0066]

[0067] After the switch is turned off, the capacitor current starts from zero, and the integral of the capacitor current between two PWM pulses is zero. During operation, the main circuit current i must be maintained. o The zero-crossing point is the midpoint of the switch's low level; the key waveform is as follows: Figure 5 As shown, this leads to the conclusion that:

[0068]

[0069] The equivalent capacitance Cs′ can be obtained from the following equation.

[0070]

[0071] The relationship between capacitor gain and duty cycle is as follows: Figure 6 As shown, adjusting the duty cycle can change the equivalent capacitance at the base frequency. The three-phase inverter source can make formula (1) hold by adjusting the impedance adjustment switch of each phase.

[0072] Let the capacitive reactance regulation capability be G(d), and its functional expression be:

[0073]

[0074] Its variation with duty cycle is as follows Figure 7 As shown, its varying impedance range is -1 / ωC S ~0;

[0075] For the filter inductor L f The maximum deviation is ±σ, and the required range of adjustment capability is:

[0076]

[0077] Combining equations (2) and (3), the range of the selected capacitor can be obtained as follows:

[0078]

[0079] This invention also proposes an impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems. The topology is connected to an LCC compensation network and includes a three-phase full-bridge inverter circuit and an impedance adjustment network. The three-phase full-bridge inverter circuit is connected to the impedance adjustment network. The three-phase full-bridge inverter circuit includes a capacitor C. DC And 6 switching transistors S1 to S6, the 6 switching transistors are connected in series in pairs and then in parallel with capacitor C. DC The impedance adjustment network comprises two impedance adjustment units connected in parallel. Each impedance adjustment unit includes two switching transistors and one capacitor. The two switching transistors are connected in series and then in parallel with the capacitor. In this topology, the filter inductor with the largest measured three-phase inductance value is connected to the inverter full bridge without passing through the impedance adjustment section. That is, the inductor with the largest inductance value is placed in the LCC compensation network. fc The other two inductors can be placed arbitrarily in the L1 position of the L2 in the L3 compensation network. fa Position and L fb The position of the series-connected capacitive reactance regulating switch, while ensuring the phase meets the control requirements, is such that the duty cycle is adjusted so that the total inductive reactance of the regulated capacitive reactance and the compensation inductor in series is equal to L. fc The sensitivity values ​​are the same.

[0080] Example

[0081] The present invention uses specific embodiments to further describe the method described herein.

[0082] The dynamic three-phase wireless power supply system operates at a frequency of 85kHz, with an input DC voltage (UDC) of 500V and a reflection impedance of 8Ω per phase. To generate a constant and uniform magnetic field and achieve sufficient output power, the current amplitude of each phase transmitting coil is [value missing].

[0083]

[0084] The required inductance value can be derived from the relationship between the current in the transmitting coil of each phase and the corresponding inductance value.

[0085]

[0086] If the maximum inductance deviation is ±5%, the required adjustment range for the capacitive reactance is:

[0087] ΔZ max ≥2σωL need

[0088] Based on the selected capacitance range formula, the required capacitance range can be obtained as follows:

[0089] C S ≤2.94μF

[0090] Therefore, a three-phase impedance adjustment capacitor with a capacitance of 2μF was selected.

[0091] The regulating switch connected in series with the filter inductor with the largest measured three-phase inductance value is set to full duty cycle. The capacitive reactance regulating switches connected in series with the other two phases are gradually reduced in duty cycle while ensuring that their phases meet the above control requirements, so that their total series inductance is the same as the inductance value of the largest three-phase filter inductor. That is, through impedance adjustment, the transmit current symmetry of the three-phase wireless power supply system of the LCC network is achieved.

[0092] To reduce costs, the impedance adjustment section can also achieve the above function using two channels with four switching transistors. This allows the filter inductor with the largest measured three-phase inductance value to bypass the impedance adjustment section and be connected to the inverter full bridge. In other words, the inductor with the largest inductance value is placed in L... fc The other two inductors can be placed anywhere in L. fa Position and L fb The position of the series-connected capacitive reactance regulating switch, while ensuring that the phase meets the control requirements, is adjusted so that the total inductive reactance of the regulated capacitive reactance and the compensation inductor in series is equal to L. fc The sensitivity values ​​are the same, such as Figure 8 As shown.

Claims

1. An impedance-adjustable inverter source topology suitable for three-phase wireless power supply systems, characterized in that, The topology includes a three-phase full-bridge inverter circuit and an impedance regulation network; the three-phase full-bridge inverter circuit is connected to the impedance regulation network; the three-phase full-bridge inverter circuit includes a capacitor. C DC and 6 switching transistors S 1 ~S 6. The six switching transistors are connected in series in pairs, then in parallel, and finally connected to a capacitor. C DC The impedance adjustment network comprises three impedance adjustment units connected in parallel. Each impedance adjustment unit includes two switching transistors and one capacitor. C S The two switching transistors are connected in series with a capacitor. C S in parallel; The inverter source topology is adjusted by adjusting S1~S6 so that: （1） in, C SA 、C SB 、C SC All of these are capacitors in an impedance adjustment network; L fA 、L fB 、L fC All are compensation inductors in the compensation network; Adjusted capacitor C S Two reverse switches in parallel S 1 and S 2. During operation, both switching transistors use the same drive, turning on and off simultaneously. The impedance adjustment principle is to adjust the drive duty cycle, causing the equivalent capacitance value to change at the fundamental frequency. It is easy to see that the relationship between the current in capacitor Cs and the drive is: Input current i o =I o sin(ωt+θ); The fundamental amplitude of the capacitor current is: After the switch is turned off, the capacitor current starts from zero, and the integral of the capacitor current between two PWM pulses is zero. During operation, the main circuit current must be maintained. i o The zero-crossing point is the midpoint of the switch's low-level state, from which we can deduce: The equivalent capacitance Cs' can be obtained from the following equation. Therefore, adjusting the duty cycle can change the equivalent capacitance at the base frequency. The three-phase inverter source makes formula (1) hold by adjusting the impedance adjustment switch of each phase. Let the capacitive reactance regulation capability be G(d), and its functional expression be: Its varying impedance range is -1 / ωC S ~0; For the filter inductor L f The maximum deviation is ±σ, and the required range of adjustment capability is: Combining equations (2) and (3), the range of the selected capacitor can be obtained as follows: 。 2. The topology according to claim 1, characterized in that: The compensation network is an LCC compensation network, an S-type compensation network, or an LCL compensation network; the compensation network is connected to the inverter source topology.

3. An impedance-adjustable inverter topology suitable for three-phase wireless power supply systems, wherein the topology is connected to an LCC compensation network, characterized in that, The topology includes a three-phase full-bridge inverter circuit and an impedance regulation network; the three-phase full-bridge inverter circuit is connected to the impedance regulation network; the three-phase full-bridge inverter circuit includes a capacitor. C DC and 6 switching transistors S 1 ~S 6. The six switching transistors are connected in series in pairs, then in parallel, and finally connected to a capacitor. C DC The impedance adjustment network comprises two impedance adjustment units connected in parallel. Each impedance adjustment unit includes two switching transistors and one capacitor. C S The two switching transistors are connected in series with a capacitor. C S Parallel connection; in the topology, the filter inductor with the largest measured three-phase inductance value is connected to the inverter full bridge without passing through the impedance adjustment section, that is, the inductor with the largest inductance value is placed in the LCC compensation network. fc The other two inductors can be placed arbitrarily in the L1 position of the L2 in the L3 compensation network. fa Position and L fb The position of the series-connected capacitive reactance regulating switch, while ensuring the phase meets the control requirements, is such that the duty cycle is adjusted so that the total inductive reactance of the regulated capacitive reactance and the compensation inductor in series is equal to L. fc The sensitivity values ​​are the same; The inverter source topology is adjusted by adjusting S1~S6 so that: （1） in, C SA 、C SB 、C SC All of these are capacitors in an impedance adjustment network; L fA 、L fB 、L fC All are compensation inductors in the compensation network; Adjusted capacitor C S Two reverse switches in parallel S 1 and S 2. During operation, both switching transistors use the same drive, turning on and off simultaneously. The impedance adjustment principle is to adjust the drive duty cycle, causing the equivalent capacitance value to change at the fundamental frequency. It is easy to see that the relationship between the current in capacitor Cs and the drive is: The input current i o =I o sin(ωt+θ); The fundamental amplitude of the capacitor current is: After the switch is turned off, the capacitor current starts from zero, and the integral of the capacitor current between two PWM pulses is zero. During operation, the main circuit current must be maintained. i o The zero-crossing point is the midpoint of the switch's low-level state, from which we can deduce: The equivalent capacitance Cs' can be obtained from the following equation. Therefore, adjusting the duty cycle can change the equivalent capacitance at the base frequency. The three-phase inverter source makes formula (1) hold by adjusting the impedance adjustment switch of each phase. Let the capacitive reactance regulation capability be G(d), and its functional expression be: Its varying impedance range is -1 / ωC S ~0; For the filter inductor L f The maximum deviation is ±σ, and the required range of adjustment capability is: Combining equations (2) and (3), the range of the selected capacitor can be obtained as follows: 。

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