A method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system

Abstract

This invention provides a method for calculating the power and efficiency of a phase-shifted full-bridge S-S wireless power transfer system, relating to the field of wireless power transfer. The method includes: determining the voltage at the inverter output terminal; determining the equivalent load resistance including the rectifier bridge, filter capacitors, and load; determining the receiver impedance, reflection impedance, and the equivalent load impedance of the inverter at the input terminal; determining the current flowing through the transmitting coil and the receiving coil according to the KVL equation, thereby determining the active power of the input power and the active power in the output power; and obtaining the output efficiency based on the active power in the input power and the active power in the output power. This invention can calculate the output power and output efficiency of this type of circuit system with relatively accurate results. The calculation process is highly reproducible and operable, providing strong theoretical support for the design of wireless power transfer systems.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission, and more particularly to a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system. Background Technology

[0002] Wireless power transfer technology is a charging and energy transfer method that utilizes invisible soft media (such as electric fields, magnetic fields, etc.) in space to transfer electrical energy from the power source to the device. Since no physical contact is required during power transfer, it greatly increases the freedom of power supply. Furthermore, wireless power transfer technology transfers energy through coil coupling, which is more flexible and safer than traditional wire connections. Existing formulas / methods for calculating the power conversion efficiency (η) and output power (P) of wireless power transfer systems are mainly based on: 1) experimental methods and 2) theoretical methods. Experimental methods involve actual measurements and analysis of the system (built, fabricated, or purchased) under a given operating condition (i.e., load resistance, input voltage, coil distance) using an oscilloscope or power analyzer. Theoretical methods do not require physical components; they directly input any given circuit parameters and, based on one or more theoretically derived formulas, obtain the efficiency and power values ​​in one step. However, the experimental method has the following drawbacks: the wiring for physical experiments is complicated; only one operating condition can be measured at a time, making it impossible to quickly measure multiple operating conditions in batches; therefore, it is inherently not scalable; and it relies on expensive measuring instruments. The (existing) theoretical method has the following drawbacks: it only considers simple circuit topologies (referred to as "topology," meaning a specific circuit element and its interconnections), without considering detailed topologies (such as the "phase-shifted full-bridge SS" topology). Summary of the Invention

[0003] To address the shortcomings of existing technologies in handling complex circuit topologies and rapidly measuring multiple points in batches, as well as the problems of complex physical wiring and high cost, this invention provides a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system. The system includes: a voltage source U for providing DC voltage. s Switches Q1, Q2, Q3, and Q4 form a rectifier bridge; diodes D1, D2, D3, and D4 form a rectifier bridge for rectification; compensation capacitors C1 and C2; filter capacitor C3; line resistors R1 and R2; and load resistor R. L A pair of coupled inductors including a transmitting coil L1 and a receiving coil L2; wherein Q1 and Q4 are switched simultaneously, Q2 and Q3 are switched simultaneously, and the two sets of switching transistors are alternately turned on to realize DC-AC inversion;

[0004] Voltage source U s The positive terminals of transistors Q1 and Q2 are connected in parallel to their collectors, and the emitters of transistors Q3 and Q4 are connected to the voltage source U.s The negative terminal of each of the switching transistors Q1, Q2, Q3, and Q4 contains an internal body diode between its collector and emitter. Switches Q1 and Q4 are connected to the same trigger voltage, while Q2 and Q3 are connected to a different trigger voltage with the same frequency and magnitude. Q4 lags Q1 by 180 degrees relative to Q1, and Q3 lags Q2 by 180 degrees relative to Q2. The emitter of switch Q1 is connected to the collector of switch Q3 and one end of capacitor C1. The emitter of switch Q2 is connected to the collector of switch Q4 and one end of resistor R1. The transmitting coil L1 is connected to the other ends of capacitor C1 and resistor R1, respectively. The receiving coil L2 is connected to one end of capacitor C2 and one end of resistor R2, respectively. The other end of capacitor C2 is connected to the anode of diode D1 and the cathode of diode D3, respectively. The other end of resistor R2 is connected to the anode of diode D2 and the cathode of diode D4, respectively. The cathodes of diodes D1 and D2 are connected in parallel to one end of capacitor C3 and the load resistor R. L One end of the diode is connected in parallel with the positive terminals of diodes D3 and D4 to capacitor C3. The other end is connected to the load resistor R. L The other end;

[0005] Based on the above system, the method for calculating the output power and output efficiency of the system includes the following steps:

[0006] S1: Determine the voltage at the inverter output terminal based on the voltage-source single-phase bridge inverter topology and the Fourier pole number method; determine the equivalent load resistance including the rectifier bridge, filter capacitor and load based on the single-phase full-wave rectifier circuit topology.

[0007] S2: Based on the inverter output voltage and equivalent load resistance determined in step S1, determine the equivalent impedance Zs and reflection impedance Z at the receiving end. R The equivalent load impedance Z of the input inverter p ;

[0008] S3: Determine the transmitting coil current and receiving coil current according to the KVL equation, and thus determine the active power of the input power and the active power of the output power.

[0009] S4: Based on the active power of the input power and the active power of the output power determined in step S3, the output efficiency is obtained.

[0010] A storage device that stores instructions and data for implementing a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system.

[0011] An apparatus for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system includes: a processor and a storage device; the processor loads and executes instructions and data in the storage device to implement a method for calculating the power and efficiency of the phase-shifted full-bridge SS wireless power transmission system.

[0012] The beneficial effects of the technical solution provided by this invention are as follows: This invention targets a wireless power transmission system with a "phase-shifted full-bridge SS" topology. Utilizing the fundamental conclusions of Fourier series, it employs a method that treats the power at the output of the phase-shifted full-bridge inverter as the system input power and the total power consumed by the receiving rectifier bridge and the actual load resistance as the system output power. Combined with a series of equivalent transformations, it finally derives calculation formulas for the output power and efficiency of the wireless power transmission system under this specific circuit topology, and its accuracy has been verified through simulation. The calculation process of this invention is clear, reproducible, and highly operable, providing strong theoretical support for the design of wireless power transmission systems. When used in the design of wireless power transmission systems, this invention can quickly and in batches estimate the system output power and efficiency under multiple different operating conditions through the calculation formulas, helping to improve the design efficiency of this type of circuit system and reduce the trial-and-error costs during the development process. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0014] Figure 1 This is a flowchart of the calculation method for output power and output efficiency in this invention.

[0015] Figure 2 This is a schematic diagram of the wireless power transmission system based on the "phase-shifted full-bridge SS topology" of the present invention.

[0016] Figure 3 This is a diagram showing the results of symbolic formula derivation and calculation using MWORKS software in an embodiment of the present invention.

[0017] Figure 4 This is a simulation model diagram of the test circuit built using Simulink software in an embodiment of the present invention.

[0018] Figure 5 This is a simulation result diagram of Simulink software in an embodiment of the present invention.

[0019] Figure 6 This is a schematic diagram of the hardware device working in an embodiment of the present invention. Detailed Implementation

[0020] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] Example 1

[0022] Please refer to Figure 1-2 , Figure 1This is a flowchart illustrating a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a wireless power transfer system based on the "phase-shifted full-bridge SS" topology. Specifically, the wireless power transfer system based on the "phase-shifted full-bridge SS" topology includes: a voltage source U for providing DC voltage. s The switching transistors Q1, Q2, Q3, and Q4 form a rectifier bridge to achieve rectification; diodes D1, D2, D3, and D4 form a rectifier bridge; capacitors C1, C2, and C3 form a capacitor bridge; line resistors R1 and R2 form a line resistor R. L A pair of coupled inductors including transmitting coil L1 and receiving coil L2; wherein, capacitors C1 and C2 are compensation capacitors for the transmitting and receiving circuits, capacitor C3 is the filter capacitor after the rectifier bridge, and Q1 and Q4 switch simultaneously, Q2 and Q3 switch simultaneously, and the two sets of switching transistors alternately conduct to realize DC-AC inversion.

[0023] Voltage source U s The positive terminals of transistors Q1 and Q2 are connected in parallel to their collectors, and the emitters of transistors Q3 and Q4 are connected to the voltage source U. s The negative terminal of each of the switching transistors Q1, Q2, Q3, and Q4 contains an internal body diode between its collector and emitter. Switches Q1 and Q4 are connected to the same trigger voltage, while Q2 and Q3 are connected to a different trigger voltage with the same frequency and magnitude. Q4 lags Q1 by 180 degrees relative to Q1, and Q3 lags Q2 by 180 degrees relative to Q2. The emitter of switch Q1 is connected to the collector of switch Q3 and one end of capacitor C1. The emitter of switch Q2 is connected to the collector of switch Q4 and one end of resistor R1. The two ends of the coupling inductor transmitting coil L1 are connected to the other ends of capacitor C1 and resistor R1, respectively. The two ends of the receiving coil L2 are connected to one end of capacitor C2 and one end of resistor R2, respectively. The other end of capacitor C2 is connected to the anode of diode D1 and the cathode of diode D3, respectively. The other end of resistor R2 is connected to the anode of diode D2 and the cathode of diode D4, respectively. The cathodes of diodes D1 and D2 are connected in parallel to one end of capacitor C3 and the load resistor R. L One end of the diode is connected in parallel with the positive terminals of diodes D3 and D4 to capacitor C3. The other end is connected to the load resistor R. L At the other end, the bases of switching transistors Q1, Q2, Q3, and Q4 are connected to the circuit related to the trigger signal. In this embodiment, Q1, Q2, Q3, and Q4 are all IGBT type switching transistors. If Q1, Q2, Q3, and Q4 were selected as MOSFET type switching transistors in this embodiment, then the voltage source U... s The positive terminals are connected in parallel to the drains of switching transistors Q1 and Q2, and the source of switching transistor Q1 is connected to the drain of switching transistor Q3 and one end of capacitor C1.

[0024] The method for calculating the output power and output efficiency of the wireless power transfer system based on the above-mentioned "phase-shifted full-bridge SS" topology includes the following steps:

[0025] S1: Determine the voltage at the inverter output terminal based on the voltage-source single-phase bridge inverter topology and the Fourier pole number method; determine the equivalent load resistance including the rectifier bridge, filter capacitor and load based on the single-phase full-wave rectifier circuit topology.

[0026] S2: Based on the inverter output voltage and equivalent load resistance determined in step S1, determine the equivalent impedance Z of the receiver. s Reflection impedance Z R The equivalent load impedance Z of the input inverter p Specifically:

[0027] Step A: Determine the voltage U after inversion. Taking a voltage-source single-phase bridge inverter as an example, the voltage becomes a square wave after passing through the DC-AC inverter. Based on the fundamental conclusions of Fourier series, and considering that the fundamental frequency accounts for a much higher proportion than harmonics, the fundamental frequency is used instead of the square wave to obtain... Where ω is the angular frequency of the fundamental wave, U s Given the DC input voltage to the system, the effective value of U is as follows:

[0028]

[0029] Step B: In the full-wave rectifier circuit, for the load resistor R L In terms of the bridge circuit's input port, its equivalent resistance is:

[0030]

[0031] Step C: Analyze the receiving loop to obtain the equivalent impedance. Determine the reflection impedance Then, the equivalent load impedance of the input inverter is obtained by analyzing the transmitting circuit. ω represents the circuit's operating angular frequency, and M is the mutual inductance between the coupled inductors. The expressions for each impedance are derived as follows:

[0032]

[0033] S3: Determine the current flowing through the transmitting coil and the receiving coil using the KVL equations, thereby determining the active power of the input power and the active power of the output power; input power refers to the power at the output of the phase-shifted full-bridge inverter, and output power refers to the equivalent resistance R including the entire rectifier bridge and filter capacitors. eq The power. The specific steps for calculating the active power in the output power are as follows:

[0034] Step A: Analyze the "phase-shifted full-bridge SS topology" wireless power transfer system and list the KVL equations for the transmitting and receiving loops as follows:

[0035]

[0036] Where I1 is the transmitting coil current, I2 is the current in the receiving coil. ω is the angular frequency of the fundamental wave, and M is the mutual inductance between the transmitting and receiving coils. The expressions for I1 and I2 are calculated as follows:

[0037]

[0038] in:

[0039]

[0040] Step B: Based on the I1 expression obtained in Step A, the active power of the input power is:

[0041]

[0042] Among them, U rms U is the effective value, and I1 is the transmitting coil current. Re represents the conjugate of I1, and Re[] represents the operation of taking the real part of a complex number;

[0043] Substituting the expressions for each quantity into the formula for calculating active power in input power, and expanding, we get:

[0044]

[0045] in,

[0046] Step C: Calculate the active power P in the output power based on the I² formula obtained in Step A. out =|I2 2 ·R eq Expanding on:

[0047]

[0048] in,

[0049]

[0050] S4: Based on the active power in the input power and the active power in the output power determined in step S3, the output efficiency is obtained: η = P out / P in .

[0051] The expression for output efficiency is obtained by rearranging:

[0052]

[0053] The expressions for λ2, λ3, λ4, λ5, and λ6 are consistent with those in step C of S3.

[0054] The above formula derivation was completed using the scientific calculator MWORKS and is consistent with the results of manual derivation.

[0055] Based on the above technical solution, using MWORKS software, numerical calculations were performed by substituting the following circuit component parameters into the above formula. The example parameters are: U s =15V, L1=350.6e-6H, C1=10e-9F, L2=350.6e-6H, C2=10e-9F, R1=0.2Ω, R2=0.2Ω, C3=100e-6F, R L =13.197Ω, M=2e-5H, base voltage frequency f=85071Hz. The input power P is calculated using MWORKS. in =17.07872973656848W, Output power P out =16.45127878394656W, output efficiency eff = 96.32612634370318% (that is, the output efficiency η mentioned above), as detailed below. Figure 3 As shown.

[0056] Then, using Simulink software, build such as Figure 4 The detailed circuit model is shown, and the input power, output power, and output efficiency of the circuit are measured using RMS components combined with the definition of power. The measurement results are as follows: Figure 5 As shown, the input power P is: in =17.08W (see) Figure 5 (a)), Output power P out =16.45W (see) Figure 5 (b)), the output efficiency eff = 96.32% (see Figure 5 (c)). It can be seen that the result here is basically consistent with the result obtained by theoretical calculation using MWROKS software.

[0057] Example 2

[0058] A device 601 for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system, such as Figure 6 As shown, it includes: a processor 602 and a storage device 603; the processor 602 loads and executes instructions and data in the storage device 603 to implement the method for calculating the power and efficiency of the phase-shifted full-bridge SS wireless power transmission system.

[0059] Example 3

[0060] A storage device that stores instructions and data for implementing a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system, characterized in that: The system includes: a voltage source U for providing DC voltage. s Switches Q1, Q2, Q3, and Q4 form a rectifier bridge; diodes D1, D2, D3, and D4 form a rectifier bridge for rectification; compensation capacitors C1 and C2; filter capacitor C3; line resistors R1 and R2; and load resistor R. L A pair of coupled inductors including a transmitting coil L1 and a receiving coil L2; wherein Q1 and Q4 are switched simultaneously, Q2 and Q3 are switched simultaneously, and the two sets of switching transistors are alternately turned on to realize DC-AC inversion; Voltage source U s The positive terminals of transistors Q1 and Q2 are connected in parallel to their collectors, and the emitters of transistors Q3 and Q4 are connected to the voltage source U. s The negative terminal of each of the switching transistors Q1, Q2, Q3, and Q4 contains an internal body diode between its collector and emitter. Switches Q1 and Q4 are connected to the same trigger voltage, while Q2 and Q3 are connected to a different trigger voltage with the same frequency and magnitude. Q4 lags Q1 by 180 degrees relative to Q1, and Q3 lags Q2 by 180 degrees relative to Q2. The emitter of switch Q1 is connected to the collector of switch Q3 and one end of capacitor C1. The emitter of switch Q2 is connected to the collector of switch Q4 and one end of resistor R1. The transmitting coil L1 is connected to the other ends of capacitor C1 and resistor R1. The receiving coil L2 is connected to one end of capacitor C2 and one end of resistor R2. The other end of capacitor C2 is connected to the anode of diode D1 and the cathode of diode D3. The other end of resistor R2 is connected to the anode of diode D2 and the cathode of diode D4. The cathodes of diodes D1 and D2 are connected in parallel to one end of capacitor C3 and the load resistor R. L One end of the diode is connected in parallel with the positive terminals of diodes D3 and D4 to capacitor C3. The other end is connected to the load resistor R. L The other end; Based on the above system, the method for calculating the output power and output efficiency of the system includes the following steps: S1: Determine the inverter output voltage based on the voltage-source single-phase bridge inverter and the Fourier series method; determine the equivalent load resistance including the rectifier bridge, filter capacitor and load based on the single-phase full-wave rectifier circuit topology. S2: Determine the equivalent impedance of the receiver based on the inverter output voltage and equivalent load resistance determined in step S1. Reflection impedance Input inverter equivalent load impedance ; S3: Determine the transmitting coil current and receiving coil current according to the KVL equation, and thus determine the active power of the input power and the active power of the output power. In step S3, the KVL equations for the transmitting and receiving coils are obtained as follows: in, It is the current in the transmitting coil. , It is the current of the receiving coil. ω is the angular frequency of the fundamental wave, and M is the mutual inductance between the coupled inductors. Input inverter equivalent load impedance; The equivalent impedance of the receiving end loop is calculated. , The expression is as follows: in, This represents the effective value of the voltage U after inversion. The active power in the input power is: in, For the effective value of U, For the transmitting coil current, express The conjugate of the complex number, Re[] denotes the operation of taking the real part of the complex number; Substituting the expressions for each quantity into the formula for calculating active power in input power, and expanding, we get: ， in, ; The active power in the output power is: in, The current flowing through the transmitting coil L2, This includes a rectifier bridge, filter capacitor C3, and load R. L The equivalent load resistance, including the load resistance; Expanded to: in S4: Based on the active power in the input power and the active power in the output power determined in step S3, the output efficiency is obtained; In step S4, the output efficiency is: in, The active power in the output power. For the active power in the input power, we can simplify to: 。 2. The method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system as described in claim 1, characterized in that: In step S1, after passing through the DC-AC inverter, the voltage U of the voltage-source single-phase bridge inverter becomes a square wave. Replacing the square wave with the fundamental wave, a Fourier series expansion is performed, yielding... ; Effective value of U for: Where U is the voltage after inversion, and t is time.

3. The method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system as described in claim 1, characterized in that: In step S1, the equivalent load resistance is: Among them, R L This is the load resistance.

4. The method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system as described in claim 2, characterized in that: In step S2, the equivalent impedance of the receiving end circuit Thus, the reflection impedance is determined. Input inverter equivalent load impedance M represents the mutual inductance between the coupled inductors; the expressions for each impedance are obtained by rearranging as follows: 。 5. A storage device, characterized in that: The storage device stores instructions and data for implementing the method for calculating the power and efficiency of the phase-shifted full-bridge SS wireless power transmission system as described in any one of claims 1 to 4.

6. A device for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transfer system, characterized in that: include: A processor and a storage device; the processor loads and executes instructions and data in the storage device to implement the method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system as described in any one of claims 1 to 4.

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