Method for calculating power and efficiency of phase-shifted full-bridge S-S wireless power transmission system

Abstract

The invention provides a method for calculating power and efficiency of a phase-shifted full-bridge S-S wireless power transmission system, and relates to the field of wireless power transmission, and the method comprises the steps: determining the voltage of the output end of an inverter; equivalent load resistance including a rectifier bridge, a filter capacitor and a load is determined; determining receiving end impedance, reflection impedance and input end inverter equivalent load impedance; current flowing through the transmitting coil and current flowing through the receiving coil are determined according to a KVL equation, and then active power of the input power and active power in the output power are determined; and obtaining the output efficiency based on the active power in the input power and the active power in the output power. According to the method, the relatively accurate output power and output efficiency of the circuit system can be calculated, the reproducibility and operability of the calculation process are high, and a powerful theoretical support is provided for the design of a wireless power transmission system.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission, and in particular to a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system. Background Art

[0002] Wireless power transmission technology is a charging and energy transmission method that uses invisible soft media in space (such as electric fields, magnetic fields, etc.) to transfer electric energy from the power supply end to the power-consuming equipment. Since no physical contact is required during the power transmission process, the freedom of power supply is greatly improved. At the same time, wireless power transmission technology transfers energy through coil coupling, which is more flexible and safer than the traditional wire connection transmission method. The existing calculation formulas / methods for the power conversion efficiency (abbreviated as "efficiency", English symbol η) and output power (abbreviated as "power", English symbol P) of wireless power transmission systems are mainly based on: 1) experimental method 2) theoretical method. The experimental method uses an oscilloscope or power analyzer to perform actual measurement and analysis on the actual system (built, manufactured or purchased) for a given operating condition (that is, load resistance, input voltage, coil distance). The theoretical method does not require the use of the actual object, directly brings in any given circuit parameters, and obtains the efficiency value and power value in one step according to one or more calculation formulas derived from the theory. However, the experimental method has the following disadvantages: the physical experimental wiring is complicated; it can only measure one operating condition at a time, and it is impossible to quickly measure multiple operating conditions in batches; therefore, it is essentially not scalable; and it relies on expensive measuring instruments. The (existing) theoretical method has the following disadvantages: it only targets simple circuit topologies (referred to as "topology", which means a certain specific circuit element and its connection relationship with each other), and does not consider detailed topologies (such as the "phase-shifted full-bridge SS" topology). Summary of the invention

[0003] In order to solve the defects of the prior art that it cannot handle complex circuit topology and fast batch measurement of multiple points, the physical wiring is complicated and the cost is high, the present invention provides a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system, the system includes: a voltage source U for providing a DC voltage s , switch tubes Q1, Q2, Q3, Q4, diodes D1, D2, D3, D4 that form a rectifier bridge to achieve rectification; compensation capacitors C1, C2, filter capacitor C3, line resistors R1, R2, 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 at the same time, Q2 and Q3 are switched at the same time, and the two sets of switch tubes are alternately turned on to realize DC-AC inversion;

[0004] Voltage source U s The positive electrode is connected in parallel to the collectors of the switch tubes Q1 and Q2, and the emitters of the switch tubes Q3 and Q4 are connected to the voltage source Us The negative electrode, the collector and emitter of the switch tubes Q1, Q2, Q3, and Q4 all contain an internal body diode. The switch tubes Q1 and Q4 are connected to the same trigger voltage, and the switch tubes Q2 and Q3 are connected to another trigger voltage. The frequency and magnitude of the two are equal. The phase of Q4 relative to Q1 and Q3 relative to Q2 lags by 180 degrees; the emitter of the switch tube Q1 is connected to the collector of the switch tube Q3 and one end of the capacitor C1, the emitter of the switch tube Q2 is connected to the collector of the switch tube Q4 and one end of the resistor R1, the two ends of the transmitting coil L1 are respectively connected to the other end of the capacitor C1 and the other end of the resistor R1, the two ends of the receiving coil L2 are respectively connected to one end of the capacitor C2 and one end of the resistor R2, the other end of the capacitor C2 is respectively connected to the positive electrode of the diode D1 and the negative electrode of the diode D3, the other end of the resistor R2 is respectively connected to the positive electrode of the diode D2 and the negative electrode of the diode D4, the negative electrode of the diode D1 and the negative electrode of the diode D2 are connected in parallel to one end of the capacitor C3 and the load resistor R L At one end, the anode of diode D3 and the anode of diode D4 are connected in parallel to the other end of capacitor C3 and 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: Based on the voltage-type single-phase bridge inverter topology and Fourier pole number method, determine the voltage at the inverter output end; based on the single-phase full-wave rectifier circuit topology, determine the equivalent load resistance including the rectifier bridge, filter capacitor and load;

[0007] S2: According to the inverter output voltage and equivalent load resistance determined in step S1, determine the receiving end equivalent impedance Zs and the reflected impedance Z R , Input inverter equivalent load impedance Z p ;

[0008] S3: Determine the transmitting coil current and the receiving coil current according to the KVL equation, thereby determining 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 determined in step S3 and the active power in the output power, the output efficiency is obtained.

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

[0011] A device for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system comprises: 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 a phase-shifted full-bridge SS wireless power transmission system.

[0012] The technical solution provided by the present invention has the following beneficial effects: the present invention is aimed at the wireless power transmission system of the "phase-shifted full-bridge SS" topology, and utilizes the basic conclusion of Fourier series, adopts a processing method that regards the power at the outlet of the phase-shifted full-bridge inverter as the system input power, and the overall power consumption of the receiving end rectifier bridge and the real load resistance as the system output power, and combines a series of equivalent transformation processing, and finally obtains the calculation formula for the output power and efficiency of the wireless power transmission system under the specific circuit topology of "phase-shifted full-bridge SS", and its accuracy is verified by simulation. The calculation process of the present invention is clear, reproducible and operable, and provides a strong theoretical support for the design of wireless power transmission systems. When the present invention is used to design a wireless power transmission system, the system output power and efficiency under multiple different operating conditions can be quickly and batch estimated through the calculation formula, which helps to improve the design efficiency of this type of circuit system and reduce the trial and error cost in the development process. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0014] Figure 1 It is a flow chart of the method for calculating output power and output efficiency in the present invention.

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

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

[0017] Figure 4 It is a simulation model diagram of a test circuit constructed using Simulink software according to an embodiment of the present invention.

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

[0019] Figure 6 It is a schematic diagram of the operation of the hardware device in the embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0021] Example 1

[0022] Please refer to Figure 1-2 , Figure 1is a flow chart of a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system in an embodiment of the present invention, Figure 2 Schematic diagram of a wireless power transmission system based on a “phase-shifted full-bridge SS” topology. The wireless power transmission system based on a “phase-shifted full-bridge SS” topology specifically includes: a voltage source U for providing a DC voltage s , switch tubes Q1, Q2, Q3, Q4, diodes D1, D2, D3, D4 that form a rectifier bridge to achieve rectification, capacitors C1, C2, C3, line resistors R1, R2, load resistor R L , a pair of coupled inductors including a transmitting coil L1 and a receiving coil L2; wherein capacitors C1 and C2 are compensation capacitors for the transmitting circuit and the receiving circuit, capacitor C3 is a filter capacitor after the rectifier bridge, and Q1 and Q4 are switched at the same time, Q2 and Q3 are switched at the same time, and the two sets of switching tubes are alternately turned on to realize DC-AC inversion.

[0023] Voltage source U s The positive electrode is connected in parallel to the collectors of the switch tubes Q1 and Q2, and the emitters of the switch tubes Q3 and Q4 are connected to the voltage source U s The negative electrode, the collector and emitter of the switch tubes Q1, Q2, Q3, and Q4 all contain an internal body diode. The switch tubes Q1 and Q4 are connected to the same trigger voltage, and the switch tubes Q2 and Q3 are connected to another trigger voltage. The frequency and magnitude of the two are equal. The phase of Q4 relative to Q1 and Q3 relative to Q2 lags by 180 degrees; the emitter of the switch tube Q1 is respectively connected to the collector of the switch tube Q3 and one end of the capacitor C1, the emitter of the switch tube Q2 is connected to the collector of the switch tube Q4 and one end of the resistor R1, the two ends of the coupled inductor transmitting coil L1 are respectively connected to the other end of the capacitor C1 and the other end of the resistor R1, the two ends of the receiving coil L2 are respectively connected to one end of the capacitor C2 and one end of the resistor R2, the other end of the capacitor C2 is respectively connected to the positive electrode of the diode D1 and the negative electrode of the diode D3, the other end of the resistor R2 is respectively connected to the positive electrode of the diode D2 and the negative electrode of the diode D4, the negative electrode of the diode D1 and the negative electrode of the diode D2 are connected in parallel to one end of the capacitor C3 and the load resistor R L At one end, the anode of diode D3 and the anode of diode D4 are connected in parallel to the other end of capacitor C3 and load resistor R L The other end; the base of the switch tubes Q1, Q2, Q3, Q4 is connected to the trigger signal related loop. In this embodiment, Q1, Q2, Q3, Q4 are all IGBT type switch tubes. If Q1, Q2, Q3, Q4 are selected as MOSFET type switch tubes in this embodiment, the voltage source U s The positive electrode is connected in parallel to the drains of the switch tubes Q1 and Q2, and the source of the switch tube Q1 is connected to the drain of the switch tube Q3 and one end of the capacitor C1.

[0024] Based on the above-mentioned “phase-shifted full-bridge SS” topology wireless power transmission system, a method for calculating the output power and output efficiency of the system includes the following steps:

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

[0026] S2: Determine the equivalent impedance Z of the receiving end according to the inverter output voltage and equivalent load resistance determined in step S1 s , reflected impedance Z R , Input inverter equivalent load impedance Z p , specifically:

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

[0028]

[0029] Step B: In the full-wave rectifier circuit, for the load resistance R L For example, the equivalent resistance from the input port of the bridge circuit is:

[0030]

[0031] Step C: Analyze the receiving end loop to obtain the equivalent impedance Determining reflected impedance Then analyze the transmitting loop to obtain the equivalent load impedance of the input inverter ω represents the circuit operating angular frequency, and M is the mutual inductance between the coupled inductors. The expressions of each impedance are obtained by sorting out as follows:

[0032]

[0033] S3: According to the KVL equation, the current flowing through the transmitting coil and the current flowing through the receiving coil are determined to determine the active power of the input power and the active power of the output power; the input power refers to the power at the outlet of the phase-shifted full-bridge inverter, and the output power refers to the equivalent resistance R including the entire rectifier bridge and filter capacitor. eq The specific steps to calculate the active power in the output power are:

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

[0035]

[0036] Where I1 is the transmitting coil current, I2 is the receiving coil current, ω is the angular frequency of the fundamental wave, M is the mutual inductance between the transmitting coil and the receiving coil, and the expressions of 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 obtained as:

[0041]

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

[0043] Substitute the expressions of each quantity into the calculation formula of active power in the input power and expand it to obtain:

[0044]

[0045] in,

[0046] Step C: Calculate the active power P in the output power according to the I2 formula obtained in step A out =|I2 2 ·R eq . Expand to get:

[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 of output efficiency is obtained by sorting:

[0052]

[0053] Among them, the expressions of 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 the results were consistent with those obtained manually.

[0055] Based on the above technical solution, MWORKS software is used to perform numerical calculations after the following circuit component parameters are substituted into the above formula. The sample 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. MWORKS calculation yields: input power P in =17.07872973656848W, output power P out =16.45127878394656W, output efficiency eff = 96.32612634370318% (that is, the output efficiency η above), specifically as Figure 3 shown.

[0056] Then, use Simulink software to build Figure 4 The detailed circuit model shown in the figure uses effective value components combined with the definition of power to measure the input power, output power and output efficiency of the circuit. The measurement results are shown in Figure 5 As shown, they are: Input power P in =17.08W(see Figure 5 (a)), output power P out =16.45W(see Figure 5 (b)), output efficiency eff = 96.32% (see Figure 5 (c)). It can be seen that the results here are basically consistent with the results obtained by the theoretical formula calculation using the MWROKS software.

[0057] Example 2

[0058] A device 601 for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system, such as Figure 6 As shown, it includes: a processor 602 and a storage device 603; the processor 602 loads and executes the 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 stores instructions and data for implementing a method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission 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 principle of the present invention should be included in 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 transmission system, characterized in that: The system comprises: a voltage source U for providing a DC voltage s , switch tubes Q1, Q2, Q3, Q4, diodes D1, D2, D3, D4 that form a rectifier bridge to achieve rectification; compensation capacitors C1, C2, filter capacitor C3, line resistors R1, R2, 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 at the same time, Q2 and Q3 are switched at the same time, and the two sets of switch tubes are alternately turned on to realize DC-AC inversion; Voltage source U s The positive electrode is connected in parallel to the collectors of the switch tubes Q1 and Q2, and the emitters of the switch tubes Q3 and Q4 are connected to the voltage source U s The negative electrode, the collector and emitter of the switch tubes Q1, Q2, Q3, and Q4 all contain an internal body diode. The switch tubes Q1 and Q4 are connected to the same trigger voltage, and the switch tubes Q2 and Q3 are connected to another trigger voltage. The frequency and magnitude of the two are equal. The phase of Q4 relative to Q1 and Q3 relative to Q2 lags by 180 degrees; the emitter of the switch tube Q1 is respectively connected to the collector of the switch tube Q3 and one end of the capacitor C1, the emitter of the switch tube Q2 is respectively connected to the collector of the switch tube Q4 and one end of the resistor R1, the two ends of the transmitting coil L1 are respectively connected to the other end of the capacitor C1 and the other end of the resistor R1, the two ends of the receiving coil L2 are respectively connected to one end of the capacitor C2 and one end of the resistor R2, the other end of the capacitor C2 is respectively connected to the positive electrode of the diode D1 and the negative electrode of the diode D3, the other end of the resistor R2 is respectively connected to the positive electrode of the diode D2 and the negative electrode of the diode D4, the negative electrode of the diode D1 and the negative electrode of the diode D2 are connected in parallel to one end of the capacitor C3 and the load resistor R L At one end, the anode of diode D3 and the anode of diode D4 are connected in parallel to the other end of capacitor C3 and 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: Based on the voltage-type single-phase bridge inverter and the Fourier series method, determine the inverter output voltage; based on the single-phase full-wave rectifier circuit topology, determine the equivalent load resistance including the rectifier bridge, filter capacitor and load; S2: Determine the equivalent impedance Z of the receiving end according to the inverter output voltage and equivalent load resistance determined in step S1 s , reflected impedance Z R , Input inverter equivalent load impedance Z p ; S3: Determine the transmitting coil current and the receiving coil current according to the KVL equation, thereby determining the active power of the input power and the active power of the output power; 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.

2. A method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system as claimed in claim 1, characterized in that: In step S1, after passing through the DC-AC inverter, the voltage U of the voltage-type single-phase bridge inverter becomes a square wave, and the square wave is replaced by the fundamental wave, and Fourier series expansion is performed to obtain The effective value of U rms for: Among them, U is the voltage after inversion, ω is the angular frequency of the fundamental wave, t is the time, U s is the input DC voltage of the system.

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

4. A method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system as claimed in claim 2, characterized in that: In step S2, the equivalent impedance of the receiving end loop The reflected impedance is determined from Input inverter equivalent load impedance ω represents the circuit operating angular frequency, and M represents the mutual inductance between the coupled inductors. The expressions of each impedance obtained by sorting are as follows:

5. A method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system as claimed in claim 4, characterized in that: In step S3, the KVL equation is obtained for the transmitting coil and the receiving coil: Where I1 is the transmitting coil current, I2 is the receiving coil current, ω is the angular frequency of the fundamental wave, M is the mutual inductance between the transmitting coil and the receiving coil, and the expressions of I1 and I2 are calculated as follows: in, The active power in the input power is: Among them, U rms is the effective value of U, I1 is the transmitting coil current, represents the conjugate of I1, Re[] represents the operation of taking the real part of a complex number; Substitute the expressions of each quantity into the calculation formula of active power in the input power and expand it to obtain: in, The active power in the output power is: P out =|I2 2 ·R eq Where I2 is the current flowing through the transmitting coil L2, R eq The rectifier bridge, filter capacitor C3 and load R L The equivalent load resistance included; Expand to: in 6. A method for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system as claimed in claim 5, characterized in that: In step S4, the output efficiency is: Among them, P out is the active power in the output power, P in is the active power in the input power, and we can get:

7. A storage device, characterized in that: The storage device stores instructions and data for implementing 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 6.

8. A device for calculating the power and efficiency of a phase-shifted full-bridge SS wireless power transmission system, characterized in that: include: Processor and 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 the phase-shifted full-bridge SS wireless power transmission system as described in any one of claims 1 to 6.

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