CN111830318B - Wireless charging high-frequency current sampling system and sampling method thereof - Google Patents

Wireless charging high-frequency current sampling system and sampling method thereof Download PDF

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CN111830318B
CN111830318B CN202010670644.7A CN202010670644A CN111830318B CN 111830318 B CN111830318 B CN 111830318B CN 202010670644 A CN202010670644 A CN 202010670644A CN 111830318 B CN111830318 B CN 111830318B
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signal
current
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CN111830318A (en
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宋凯
张子明
姜金海
梁策
张航
逯仁贵
朱春波
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Harbin Institute of Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
    • G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
    • G01R19/2509—Details concerning sampling, digitizing or waveform capturing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/02—Measuring effective values, i.e. root-mean-square values
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
    • G05B19/0423—Input/output
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/10—Technologies relating to charging of electric vehicles
    • Y02T90/14—Plug-in electric vehicles

Abstract

The invention discloses a wireless charging high-frequency current sampling system and a sampling method thereof. The invention belongs to the technical field of wireless power transmission, and the system comprises: the device comprises a DSP (digital signal processor), a current transformer, an input acquisition module, a bias and signal amplification module and a voltage following module; the input signal is amplified by a bias and signal amplification module through high-frequency alternating current in a current transformer acquisition circuit, the amplified signal is input into a voltage following module to play a buffering role, the buffered signal is input into an input acquisition circuit again, and the buffered signal is input into a DSP (digital signal processor) by an input acquisition module to finish current hardware sampling; the output quantity of the input acquisition module is input into an ADC module in the DSP processor for current sampling, and the current is input into the DSP processor after current sampling processing for high-frequency current sampling. The method provided by the patent has the advantages of high precision, high speed, simple system structure and the like.

Description

Wireless charging high-frequency current sampling system and sampling method thereof
Technical Field
The invention relates to the technical field of wireless power transmission, in particular to a wireless charging high-frequency current sampling system and a sampling method thereof.
Background
Nowadays, wireless charging technology is rapidly developing. The wireless charging technology enables the working equipment to be separated from the constraint of the wire when the working equipment moves, the problems of heating, aging, accidental electric shock of people and the like of the wire are avoided, the wireless charging device is safe and reliable to operate, and can be applied to occasions where electric energy transmission cannot be achieved due to the fact that the wire is limited, such as electric automobiles, implanted medical electronic equipment, industrial robots, underwater detection equipment, household electronic equipment and the like. The appearance of the wireless charging technology brings great convenience to production and life of people. In the technical field of wireless charging, in order to realize output constant current control, high-frequency current in a system is generally required to be collected, converted into effective value voltage and then input into an MCU (microprogrammed control unit) for subsequent control. Therefore, the acquisition time of the high-frequency current influences the analysis speed of the MCU, so that the response time of the output constant current is influenced, and the response time is prolonged and cannot meet the corresponding technical requirements. How to shorten the acquisition time of the effective value of the output high-frequency current is always a problem of industrial research. However, in the conventional technology, the complexity of the overall design is increased and the cost is high to ensure a fast acquisition speed.
The prior art discloses a high-frequency current partial discharge signal acquisition sensor, which can acquire a high-frequency current partial discharge signal of a micro signal, induce a voltage current on a coil, and convert the current into a voltage through a resistor. The device has the advantages of large operation processing amount, long sampling time and low acquisition speed.
The prior art discloses a brushless motor high-frequency current acquisition module, which adopts a heat dissipation device to effectively dissipate a large amount of heat generated during acquisition of high-frequency current so as to protect components, but the acquisition speed and the acquisition precision of the high-frequency current are not considered in the method. In fact, the high-frequency current of the patent is low in acquisition speed and general in acquisition precision.
Disclosure of Invention
The invention provides a wireless charging high-frequency current sampling system and a sampling method thereof for realizing rapid high-frequency current sampling, and the invention provides the following technical scheme:
a wireless charging high-frequency current sampling system, the system comprising: the device comprises a DSP (digital signal processor), a current transformer, an input acquisition module, a bias and signal amplification module and a voltage following module;
the DSP processor control signal data signal input end is connected with the input acquisition module data signal output end, the current transformer data signal output end is connected with the input acquisition module data signal input end, the input acquisition module control signal output end is connected with the control signal input end of the bias and signal amplification module, the control signal output end of the bias and signal amplification module is connected with the control signal input end of the voltage following module, and the data signal output end of the voltage following module is connected with the input acquisition module.
Preferably, the voltage following module employs OPA340, and the bias and signal amplification module employs INA 128.
A wireless charging high-frequency current sampling method comprises the following steps:
step 1: alternating current in the circuit is acquired through the current transformer, and is input to the offset and signal amplification module after being subjected to amplitude limiting and low-pass filtering through the input acquisition module;
step 2: the bias and signal amplification module amplifies an input signal, and inputs the amplified signal to the voltage following module for signal conditioning;
and step 3: inputting the collected signal into the input collection circuit again, and inputting the collected signal into the DSP processor by the input collection module to finish current hardware sampling;
and 4, step 4: the output quantity of the input acquisition module is input into an ADC module in the DSP processor for current sampling, and the current is input into the DSP processor after current sampling processing for output constant current control.
Preferably, interval break points are carried out on the collected current, the initial collection point is alpha, the termination collection point is b, the collected input current is equally divided by n, the step length h and the node x are determined k Mean evenly inserted node x k+1/2 Node x k Corresponding sine function value f (x) k ) Mean value evenly inserted node x k+1/2 Corresponding sine function value f (x) k+1/2 )，k＝1,2,…n-1；
Determining sine function value f (x) of each node k ) Is denoted sum 1; uniformly inserting the mean value into the node sine function value f (x) k+1/2 ) The sum is denoted sum 2; the integrated value S is calculated by using the simpson algorithm, and is expressed by the following formula:
Figure BDA0002582159230000021
wherein f (alpha) is a starting collection point function, and f (b) is a terminating collection point function;
acquiring the amplitude voltage Um according to the integral value S, and solving the amplitude voltage Um through the following formula:
Figure BDA0002582159230000022
wherein T is a sampling period, f is frequency, and T is time;
and determining the collected current according to the amplitude voltage to finish current sampling.
Preferably, the sampling delay is controlled within 0.25 period.
The invention has the following beneficial effects:
the integral of the absolute value of the half period of the sine quantity is proportional to the amplitude Um, so that the integral value of any half period of the sine quantity can represent the effective value of the complete period of the current sine quantity. The invention can realize the sampling speed faster than the single signal period by using the sampling circuit and the algorithm, and ensure that the system realizes the single signal period control. Compared with the problems that the corresponding speed is low due to traditional multi-period sampling, the operation amount is large due to complete period sampling, the system is complex and not easy to realize, and the like, the method provided by the patent has the advantages of high precision, high speed, simple system structure and the like.
Drawings
Fig. 1 is a structural diagram of a wireless charging high-frequency current sampling system;
FIG. 2 is a schematic diagram of an input acquisition module;
FIG. 3 is a schematic diagram of an offset and signal amplification module;
FIG. 4 is a schematic diagram of a voltage follower module;
fig. 5 is a flowchart of a high-frequency current sampling method of the wireless charging system;
fig. 6 is a graph of the effect of current sampling of the coil at the transmitting end.
Detailed Description
The present invention will be described in detail with reference to specific examples.
The first embodiment is as follows:
as shown in fig. 1 to 4, the present invention provides a wireless charging high-frequency current sampling system and a sampling method thereof, which specifically include:
the invention provides a wireless charging high-frequency current sampling system, which comprises: the device comprises a DSP (digital signal processor), a current transformer, an input acquisition module, a bias and signal amplification module and a voltage following module;
the DSP processor control signal data signal input end is connected with the input acquisition module data signal output end, the current transformer data signal output end is connected with the input acquisition module data signal input end, the input acquisition module control signal output end is connected with the control signal input end of the bias and signal amplification module, the control signal output end of the bias and signal amplification module is connected with the control signal input end of the voltage following module, and the data signal output end of the voltage following module is connected with the input acquisition module.
The voltage following module employs OPA340 and the bias and signal amplification module employs INA 128.
As shown in fig. 2, the current transformer collects current and inputs the current into the collection input port, the input current forms a limiting circuit through the switching diodes D1 and D2, and the input signal is clamped; the resistor R1 and the capacitor C1 form a first low-pass filter circuit, and the cut-off frequency fc of the first low-pass filter circuit satisfies the following relation:
Figure BDA0002582159230000031
and the filtering output signal Vf is connected with the bias and signal amplification module and the voltage following module. The acquisition output end J1 is connected with the output end CHN of the voltage following module after passing through the resistor R2; j1 is connected to the ADC block in the DSP.
The filter range of the first low-pass filter circuit formed by the R1 and the C1 is mainly more than three times of harmonics in the signal, and the filter cutoff frequency is set to be three times of the fundamental frequency, so that excessive signal delay is not caused.
As shown in fig. 3, the core of the bias and signal amplification module is a three-operational amplifier high-speed amplifier composed of U1, U2 and U3. When RN1 is RN2, RN3 is RN4, and RN5 is RN6, the amplification factor G of the triple-operational amplifier high-speed amplifier satisfies the following relation:
Figure BDA0002582159230000032
the bias and signal amplification module can condition the collected high-frequency alternating current signals to a voltage range which can be collected by the DSP chip, and the output signals of the signal conditioning circuit can be ensured to have smaller delay relative to the input signals due to the adoption of the high-speed operational amplifier chip.
As shown in fig. 4, in the voltage follower module, an operational amplifier U4 mainly forms a voltage follower circuit, which is used for driving an ADC module in the DSP; the switching diodes D3, D4, the resistor R5 and the capacitor C2 form an amplitude limiting circuit and a second low-pass filter circuit, and the basic principle of the amplitude limiting circuit and the second low-pass filter circuit is the same as that of the circuit in the input acquisition module; the output CHN of the voltage following module is connected in series with the resistor R2 of the acquisition module and then connected with the acquisition output J1 to be input into the ADC module in the DSP.
As shown in fig. 5, the present invention provides a wireless charging high-frequency current sampling method, which includes the following steps:
step 1: alternating current in the circuit is acquired through the current transformer, and is input to the offset and signal amplification module after being subjected to amplitude limiting and low-pass filtering through the input acquisition module;
step 2: the bias and signal amplification module amplifies an input signal, and inputs the amplified signal to the voltage following module for signal conditioning;
and step 3: inputting the collected signal into the input collection circuit again, and inputting the collected signal into the DSP processor by the input collection module to finish current hardware sampling;
and 4, step 4: the output quantity of the input acquisition module is input into an ADC module in the DSP processor for current sampling, and the current is input into the DSP processor after current sampling processing for output constant current control.
Carrying out interval breakpoint on the collected current, wherein the initial collection point is alpha, the termination collection point is b, carrying out n equal division on the collected input current, and determining the step lengthh, node x k Mean evenly inserted node x k+1/2 Node x k Corresponding sine function value f (x) k ) Mean value evenly inserted node x k+1/2 Corresponding sine function value f (x) k+1/2 )，k＝1,2,…n-1；
Determining sine function value f (x) of each node k ) Is denoted sum 1; uniformly inserting the mean value into the node sine function value f (x) k+1/2 ) The sum is denoted sum 2; the integrated value S is calculated by using the simpson' S algorithm, and is expressed by the following formula:
Figure BDA0002582159230000041
wherein f (alpha) is a starting collection point function, and f (b) is a terminating collection point function;
acquiring the amplitude voltage Um according to the integral value S, and solving the amplitude voltage Um through the following formula:
Figure BDA0002582159230000042
wherein T is a sampling period, f is frequency, and T is time;
and determining the collected current according to the amplitude voltage to finish constant current sampling.
The second concrete embodiment:
the DSP sampling algorithm uses a half-cycle integration algorithm, and the basic principle is as follows: the integral of the absolute value of the sine quantity in any half period is a constant S, the S is irrelevant to the initial phase angle alpha of the starting point of the integral, and the integral of the absolute value is proportional to the amplitude Um. According to the principle, the quick effective value calculation of the input signal can be realized, and the speed reaches one half period of the input signal.
The specific principle of half-cycle sampling is as follows:
Figure BDA0002582159230000051
the half-cycle integration algorithm can be expressed as follows:
Figure BDA0002582159230000052
since the sampled values are summed instead of integrated, an error is also introduced, where K (α) varies with the α value. When the number of sampling points in a period is not changed, the value of K (alpha) is only related to alpha. The integral formula is approximated using a trapezoidal algorithm as:
Figure BDA0002582159230000053
u 'in the formula' k For interpolated values, the algorithm can accurately find interpolated values for clean sinusoidal signals, thereby reducing errors, and can improve the calculation accuracy for some signals that approximate a sine. kp is constant, and the overall running speed is high.
The method for calculating the integral by using the composite Simpson algorithm instead of the trapezoidal algorithm comprises the following steps:
Figure BDA0002582159230000054
in the formula: m is the number of 1/4 cycles of samples. The trapezoidal algorithm has one-time algebraic precision, and the complex Simpson algorithm has at least three-time algebraic precision. Therefore, the accuracy of the algorithm can be improved and the error can be reduced by using the compound Simpson algorithm. Meanwhile, the operation amount of the Simpson algorithm is extremely small, and the processing speed is high.
Average value is used to insert N/2 u' k The algebraic precision of the Simpson algorithm is improved to be at least 3 times, the precision reaches 4 times after interpolation improvement, and the operation amount is not increased so that the processing speed is still high.
Fig. 6 is a diagram showing the effect of current sampling of the transmitting-end coil in the present embodiment. The effect of the original signal and the sampled signal is shown in the figure, and the core part is completed by using C language. As can be seen from the figure, the sampling signal of the device can accurately reflect the actual sinusoidal current signal, and the sampling delay is controlled within 0.25 period, which is beneficial to the dynamic response capability.
The above description is only a preferred embodiment of the wireless charging high-frequency current sampling system and the sampling method thereof, and the protection range of the wireless charging high-frequency current sampling system and the sampling method thereof is not limited to the above embodiments, and all technical solutions belonging to the idea belong to the protection range of the present invention. It should be noted that modifications and variations which do not depart from the gist of the invention will be those skilled in the art to which the invention pertains and which are intended to be within the scope of the invention.

Claims (3)

1. A wireless charging high-frequency current sampling method is based on a wireless charging high-frequency current sampling system, and the system comprises: the device comprises a DSP (digital signal processor), a current transformer, an input acquisition module, a bias and signal amplification module and a voltage following module;
DSP treater control signal data signal input end connects input acquisition module data signal output end, current transformer data signal output end connects input acquisition module data signal input end, input acquisition module control signal output end connects the control signal input of biasing and signal amplification module, the control signal input of biasing and signal amplification module control signal output end connection voltage following module, the data signal output end connection input acquisition module, characterized by of voltage following module: the method comprises the following steps:
step 1: alternating current in the circuit is acquired through the current transformer, and is input to the offset and signal amplification module after being subjected to amplitude limiting and low-pass filtering through the input acquisition module;
step 2: the bias and signal amplification module amplifies an input signal, and inputs the amplified signal to the voltage following module for signal conditioning;
and step 3: inputting the acquired signal into the input acquisition circuit again, and inputting the acquired signal into the DSP through the input acquisition module to finish current hardware sampling;
and 4, step 4: the output quantity of the input acquisition module is input to an ADC module in the DSP processor for current sampling, and is input to the DSP processor after current sampling processing for output constant current control;
carrying out interval breakpoint on the collected current, wherein the initial collection point is alpha, the termination collection point is b, carrying out n equal division on the collected input current, determining step length h and node x k Mean evenly inserted node x k+1/2 Node x k Corresponding sine function value f (x) k ) Mean value evenly inserted node x k+1/2 Corresponding sine function value f (x) k+1/2 )，k＝1,2,…n-1；
Determining sine function value f (x) of each node k ) Is denoted sum 1; uniformly inserting the mean value into the node sine function value f (x) k+1/2 ) The sum is denoted sum 2; the integrated value S is calculated by using the simpson' S algorithm, and is expressed by the following formula:
Figure FDA0003651795170000011
wherein f (alpha) is a starting collection point function, and f (b) is an ending collection point function;
acquiring the amplitude voltage Um according to the integral value S, and solving the amplitude voltage Um through the following formula:
Figure FDA0003651795170000012
wherein T is a sampling period, f is frequency, and T is time;
and determining the collected current according to the amplitude voltage to finish current sampling.
2. The wireless charging high-frequency current sampling method according to claim 1, characterized in that: the sampling delay is controlled within 0.25 period.
3. The wireless charging high-frequency current sampling method according to claim 1, characterized in that: the voltage following module employs OPA340 and the bias and signal amplification module employs INA 128.
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