CN108649804B - Direct current transformer system based on magnetic coupling wireless power transmission - Google Patents
Direct current transformer system based on magnetic coupling wireless power transmission Download PDFInfo
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- CN108649804B CN108649804B CN201810589925.2A CN201810589925A CN108649804B CN 108649804 B CN108649804 B CN 108649804B CN 201810589925 A CN201810589925 A CN 201810589925A CN 108649804 B CN108649804 B CN 108649804B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
- H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
- H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
- H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
- H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
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Abstract
The invention provides a direct current transformer system based on magnetic coupling wireless power transmission, which comprises: the DC-AC inversion module is used for converting input direct current into primary side high-frequency alternating current; the wireless power transmission module comprises a primary side resonance module and a secondary side resonance module, wherein the primary side resonance module receives the high-frequency alternating current, converts the high-frequency alternating current into a strongly coupled electromagnetic field and sends the strongly coupled electromagnetic field to the secondary side resonance module; the secondary resonance module receives the electromagnetic energy and converts the electromagnetic energy into secondary high-frequency alternating current; and the rectification filtering module is used for converting the secondary side high-frequency alternating current into direct current through rectification, filtering out high-frequency components and finally outputting direct current voltage. The transformer system has a simple, reliable and practical circuit structure, and realizes high-efficiency wireless electric energy transmission with controllable transmission power between two sides of the transformer.
Description
Technical Field
The invention relates to the technical field of wireless power transmission and power electronics, in particular to a direct-current transformer system based on magnetic coupling wireless power transmission.
Background
The direct current transformer is divided into two types, namely a direct current transformer with adjustable output and a direct current transformer with unregulated output, the direct current transformer can realize power transmission and voltage improvement, is widely applied to a high-voltage direct current transmission system, has a plurality of applications in the field of new energy resources such as photovoltaic, fuel cells, super capacitors and the like, and simultaneously, the direct current-direct current transformer technology can also be used for a direct current voltage sampling and direct current energy transmission and impedance conversion circuit.
The direct current-direct current transformer is generally solved by adopting a power electronic scheme, wherein a high-frequency transformer based on an electromagnetic induction principle is generally adopted for completing an isolation transformation task, namely, alternating current is obtained by direct current inversion firstly, the alternating current is transformed by the high-frequency transformer to complete a transformation ratio and an electrical isolation task, and finally, direct current is obtained by rectification, namely, a common DC/AC/DC scheme. At present, a direct current-direct current transformer is mainly used in the field of high-voltage direct current transmission systems and new energy resources, and is widely applied to occasions such as photovoltaics, fuel cells, super capacitors and the like.
The strong magnetic coupling wireless power transmission and conversion technology is a promising high and new technology, has a very wide application prospect, can obtain a direct current-direct current transformer by adopting a strong magnetic coupling wireless power transmission and conversion scheme, is different from an isolation mode of a transformer of a conventional power electronic scheme by an electromagnetic induction principle, carries out energy transmission by a high-frequency resonance coupling principle of an original coil and a secondary coil, can realize the physical isolation of a non-magnetic core scheme of the original coil and the secondary coil and simultaneously realize wireless power transmission, and can make the design more flexible in industrial application. However, considering that the strong magnetic coupling wireless power transmission is very sensitive to the load change or the energy flow change of the secondary side, i.e. the energy receiving side, the working frequency and the output power transmitted by the wireless circuit need to be adjusted to realize the high-efficiency wireless power transmission with controllable transmission power between the two sides of the transformer.
Disclosure of Invention
In view of the above problems, the present invention is directed to a dc transformer system based on a strong magnetic coupling wireless power transmission transformation, in which a high frequency transformer is replaced by a strong magnetic coupling wireless power transmission transformation part, the energy transmission of the dc-dc transformer is realized by a wireless power transmission transformation technology, and the high-efficiency wireless power transmission with controllable transmission power between two sides of the transformer is realized by controlling and adjusting the working frequency and output power of the wireless power transmission.
The purpose of the invention is realized by adopting the following technical scheme:
provided is a direct current transformer system based on magnetic coupling wireless power transmission, including:
the DC-AC inversion module is used for converting input direct current into primary side high-frequency alternating current;
the wireless power transmission module comprises a primary side resonance module and a secondary side resonance module, wherein the primary side resonance module receives the high-frequency alternating current, converts the high-frequency alternating current into a strongly coupled electromagnetic field and sends the strongly coupled electromagnetic field to the secondary side resonance module; the secondary resonance module receives the electromagnetic energy and converts the electromagnetic energy into secondary high-frequency alternating current;
the rectification filtering module is used for converting the secondary high-frequency alternating current rectification into direct current and filtering out high-frequency components;
the positive and negative ends of the direct current input are connected with the input end of the DC-AC inversion module; the output end of the DC-AC inversion module is connected with the input end of the wireless power transmission module; the output end of the wireless power transmission module is connected with the input end of the rectification filter module; and the rectifying and filtering module obtains the finally output direct-current voltage.
Preferably, the DC-AC inverter module is a single-phase full-bridge inverter circuit, and includes two parallel-connected bridge arms, and each bridge arm is connected in series with two fully-controlled transistors.
Preferably, the wireless power transmission module includes: inductance of LyPrimary side coil and capacitor CyInductance is LfSecondary winding and capacitor Cf(ii) a The primary coil and the capacitor CyThe DC-AC inverter module is connected with the output end of the DC-AC inverter module after being connected in series to form the primary side, namely the input end, of the wireless power transmission module; the secondary coil and the capacitor CfAnd the secondary side, namely the output end, of the wireless power transmission module is formed by connecting the two modules in parallel.
Preferably, the rectification filter module comprises a full-bridge rectification circuit and an LC filter circuit, the input end of the full-bridge rectification circuit is connected with the output end of the wireless power transmission module, and the output end of the full-bridge rectification circuit is connected with the LC filter circuit and then is output.
Preferably, the dc transformer system further includes: the DC-AC inverter comprises a sampling monitoring unit, a zero-crossing detection unit, a driving module and a control module, wherein the sampling monitoring unit is used for sampling and monitoring the voltage and the current flowing through the input end and the output end of a DC-AC inverter module, the voltage and the current of the output end of a rectifying filter; the zero-crossing detection unit is used for acquiring the time when the monitored voltage and current pass through a zero point in a resonance period; the control module is used for controlling the working frequency of the DC-AC inversion module and the output power of the DC transformer; the driving module is controlled by the control module and drives a switching tube in the DC-AC inversion module to be switched on or switched off.
Preferably, the control module includes a state determination unit configured to determine whether the wireless power transmission module is in a resonant state and a frequency correction unit configured to adjust an operating frequency of the DC-AC inverter module so that the operating frequency is adapted to the resonant frequency during off-resonance transmission, and a specific process of the control module adjusting the operating frequency of the DC-AC inverter module is as follows:
(1) and (3) state judgment: the sampling monitoring unit is used for sampling and monitoring the voltage and the current of the input end of the DC-AC inversion module and sending a sampling monitoring result into the state judgment unit, the voltage and the current of the input end which are sampled and monitored are passed through the multiplier and the zero value comparator, if the product of the voltage and the current is more than 0, the wireless electric energy transmission module is in a resonance state, and at the moment, the working frequency of the DC-AC inversion module adapts to the resonance frequency of the wireless electric energy transmission module; otherwise, the state judgment unit judges that the wireless power transmission module is in the detuning state and enters the step (2);
(2) and (3) establishing an adjusting function: the zero-crossing detection unit calculates the zero-crossing time of the input end voltage and the current of the DC-AC inversion module, and establishes a frequency regulation function according to the zero-crossing time, wherein the frequency regulation function is as follows:
in the formula of UtA voltage feedback adjustment value; f. ofkThe switching frequency of a switching device in the DC-AC inversion module; t is tiThe moment when the input voltage of the DC-AC inversion module crosses zero; t is tjThe moment when the input current of the DC-AC inversion module crosses zero; u shapesetA known voltage comparison value representing a set voltage adapted to a resonant frequency of the wireless power transmission module; gamma is a frequency variance adjustment factor; f. ofzIs a resonance frequency of the wireless power transmission module.
(3) Adjusting the switching frequency of a switching device in the DC-AC inversion module according to the frequency adjusting function, so that the switching frequency returns to the frequency corresponding to the resonant frequency of the wireless power transmission module; the switching frequency of the switching device is specifically adjusted in the following process:
1) acquiring a resonance frequency sigma neighborhood located in a wireless power transmission module as follows: [ f ] ofz-σ，fz+σ](ii) a The endpoint frequency of the field corresponds to the same voltage feedback adjustment value on the frequency adjustment function and is recorded as a reference voltage adjustment value Uck；
2) Setting the working frequency of the DC-AC inversion module obtained by the ith sampling as fki(ii) a And calculating a voltage feedback regulation value U corresponding to the ith regulation according to the zero-crossing time of the voltage and the current of the input end of the DC-AC inverter circuit obtained by samplingti(ii) a Feeding back the regulation value U according to the calculated voltagetiAnd a reference voltage regulation value UckComparing the working frequency f of the DC-AC inverter circuit obtained according to the sampling of the (i-1) th timek(i-1)Working frequency f of the DC-AC inverter circuit obtained by sampling at the ith timekiRelative magnitude of comparison and voltage feedback adjustment value UtiAnd a reference voltage regulation value UckDifferent comparison results adopt different strategies to update the existing working frequency fkiSo that the existing operating frequency fkiTowards the resonance frequency fzApproaching; and triggering the driving circuit through processing the updated working frequency, and adjusting the frequency of the DC-AC inversion module.
3) When the calculated voltage feedback adjustment value U corresponding to the ith adjustment is obtainedtiIs equal to the voltage comparison value UsetWhen the wireless power transmission module is used, the adjustment process is finished, and the switching frequency of a switching device in the DC-AC inversion module returns to the frequency corresponding to the resonant frequency of the wireless power transmission module; otherwise, continue with step 2).
The invention has the beneficial effects that: the magnetic coupling wireless electric energy transmission conversion technology realizes a direct current-direct current transformer; the wireless power transmission can be carried out, so that the application occasion is more flexible, and the circuit has a simple, reliable and practical structure. The direct current-direct current transformer can be widely applied to the application fields of high-voltage direct current transmission systems, new energy sources, direct current energy wireless transmission, wireless scheme direct current impedance transformation circuits, certain special experiments and the like; and the circuit model of the transformer system is analyzed, and a direct current-direct current transformer system capable of controlling and adjusting the working frequency and the output power of wireless electric energy transmission is provided, so that the wireless electric energy transmission with high efficiency and controllable transmission power between two sides of the transformer is realized.
Drawings
The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.
FIG. 1 is a circuit diagram of a DC transformer circuit in accordance with a preferred embodiment of the present invention;
fig. 2 is a circuit topology connection diagram of a DC-AC inverter module in a preferred embodiment of the invention.
Reference numerals:
a DC-AC inversion module 1; a wireless power transmission module 2; a rectification filter module 3;
Detailed Description
The invention is further described in connection with the following application scenarios. The described embodiments are only some, but not all embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, in this embodiment, a magnetic coupling wireless power transmission-based dc transformer system is provided, including:
the DC-AC inversion module 1 is used for converting input direct current into primary side high-frequency alternating current;
the wireless power transmission module 2 comprises a primary side resonance module and a secondary side resonance module, wherein the primary side resonance module receives the high-frequency alternating current, converts the high-frequency alternating current into a strongly coupled electromagnetic field and sends the strongly coupled electromagnetic field to the secondary side resonance module; the secondary resonance module receives the electromagnetic energy and converts the electromagnetic energy into secondary high-frequency alternating current;
the rectification filter module 3 is used for converting the secondary side high-frequency alternating current rectification into direct current and filtering out high-frequency components;
the positive and negative ends of the direct current input are connected with the input end of the DC-AC inversion module; the output end of the DC-AC inversion module is connected with the input end of the wireless power transmission module; the output end of the wireless power transmission module is connected with the input end of the rectification filter module; and the rectifying and filtering module obtains the finally output direct-current voltage.
In this embodiment, the DC-AC inverter module is a single-phase full-bridge inverter circuit, and includes two parallel-connected bridge arms, and each bridge arm is connected in series with two fully-controlled transistors.
In this embodiment, the wireless power transmission module includes: inductance of LyPrimary side coil of, electricityContainer CyInductance is LfSecondary winding and capacitor Cf(ii) a The primary coil and the capacitor CyThe DC-AC inverter module is connected with the output end of the DC-AC inverter module after being connected in series to form the primary side, namely the input end, of the wireless power transmission module; the secondary coil and the capacitor CfAnd the secondary side, namely the output end, of the wireless power transmission module is formed by connecting the two modules in parallel.
In this embodiment, the rectification filter module includes full-bridge rectifier circuit and LC filter circuit, the input of full-bridge rectifier circuit is connected with wireless power transmission module's output, and LC filter circuit is connected to full-bridge rectifier circuit's output and then is exported.
In this embodiment, the dc transformer system further includes: the DC-AC inverter comprises a sampling monitoring unit, a zero-crossing detection unit, a driving module and a control module, wherein the sampling monitoring unit is used for sampling and monitoring the voltage and the current flowing through the input end and the output end of a DC-AC inverter module, the voltage and the current of the output end of a rectifying filter; the zero-crossing detection unit is used for acquiring the time when the monitored voltage and current pass through a zero point in a resonance period; the control module is used for controlling the working frequency of the DC-AC inversion module and the output power of the DC transformer; the driving module is controlled by the control module and drives a switching tube in the DC-AC inversion module to be switched on or switched off.
In this embodiment, the control module includes a state determining unit configured to determine whether the wireless power transmission module is in a resonant state and a frequency correcting unit configured to adjust a working frequency of the DC-AC inverter module so that the working frequency is adapted to the resonant frequency during off-resonance transmission, and a specific process of adjusting the working frequency of the DC-AC inverter module by the control module is as follows:
(1) and (3) state judgment: the sampling monitoring unit is used for sampling and monitoring the voltage and the current of the input end of the DC-AC inversion module and sending a sampling monitoring result into the state judgment unit, the voltage and the current of the input end which are sampled and monitored are passed through the multiplier and the zero value comparator, if the product of the voltage and the current is more than 0, the wireless electric energy transmission module is in a resonance state, and at the moment, the working frequency of the DC-AC inversion module adapts to the resonance frequency of the wireless electric energy transmission module; otherwise, the state judgment unit judges that the wireless power transmission module is in the detuning state and enters the step (2);
(2) and (3) establishing an adjusting function: the zero-crossing detection unit calculates the zero-crossing time of the input end voltage and the current of the DC-AC inversion module, and establishes a frequency regulation function according to the zero-crossing time, wherein the frequency regulation function is as follows:
in the formula of UtA voltage feedback adjustment value; f. ofkThe switching frequency of a switching device in the DC-AC inversion module; t is tiThe moment when the input voltage of the DC-AC inversion module crosses zero; t is tjThe moment when the input current of the DC-AC inversion module crosses zero; u shapesetA known voltage comparison value representing a set voltage adapted to a resonant frequency of the wireless power transmission module; gamma is a frequency variance adjustment factor; f. ofzIs a resonance frequency of the wireless power transmission module.
(3) Adjusting the switching frequency of a switching device in the DC-AC inversion module according to the frequency adjusting function, so that the switching frequency returns to the frequency corresponding to the resonant frequency of the wireless power transmission module; the switching frequency of the switching device is specifically adjusted in the following process:
1) acquiring a resonance frequency sigma neighborhood located in a wireless power transmission module as follows: [ f ] ofz-σ，fz+σ](ii) a The endpoint frequency of the field corresponds to the same voltage feedback adjustment value on the frequency adjustment function and is recorded as a reference voltage adjustment value Uck；
2) Setting the working frequency of the DC-AC inversion module obtained by the ith sampling as fki(ii) a And calculating a voltage feedback regulation value U corresponding to the ith regulation according to the zero-crossing time of the voltage and the current of the input end of the DC-AC inverter circuit obtained by samplingti(ii) a Feeding back the regulation value U according to the calculated voltagetiAnd a reference voltage regulation value UckComparing the working frequency f of the DC-AC inverter circuit obtained according to the sampling of the (i-1) th timek(i-1)And the ith miningSampling the working frequency f of the obtained DC-AC inverter circuitkiRelative magnitude of comparison and voltage feedback adjustment value UtiAnd a reference voltage regulation value UckDifferent comparison results adopt different strategies to update the existing working frequency fkiSo that the existing operating frequency fkiTowards the resonance frequency fzApproaching; and triggering the driving circuit through processing the updated working frequency, and adjusting the frequency of the DC-AC inversion module.
3) When the calculated voltage feedback adjustment value U corresponding to the ith adjustment is obtainedtiIs equal to the voltage comparison value UsetWhen the wireless power transmission module is used, the adjustment process is finished, and the switching frequency of a switching device in the DC-AC inversion module returns to the frequency corresponding to the resonant frequency of the wireless power transmission module; otherwise, continue with step 2).
In the preferred embodiment, frequency detuning and rapid adjustment can be found in time by setting a state judging unit for judging whether the wireless power transmission module is in a resonance state and a frequency correcting unit for adjusting the working frequency of the DC-AC inverter module to be adaptive to the resonance frequency during detuning transmission; and a frequency adjusting function and a corresponding adjusting algorithm are designed, so that the response speed of frequency adjustment is high, and the electric energy transmission efficiency of the wireless electric energy transmission module is ensured.
In this embodiment, it is considered that when wireless power transmission is performed, energy loss exists in the wireless power transmission module due to magnetic coupling, and there is time delay in the prior art by detecting voltage and current of the secondary side of the transformer to calculate output power and performing feedback control according to a calculation result, which causes control bias delay; therefore, based on the law of conservation of energy and the principle of an equivalent circuit, all parts of the secondary side of the transformer are equivalent to the primary side of the transformer; the power transmitted from the primary side of the transformer to the secondary side can be determined by calculating the equivalent resistance of the equivalent circuit of the secondary side to the primary side of the transformer, and the output power of the transformer system to the outside is reflected.
In this embodiment, the control module further includes: and the output power regulating module is used for calculating an equivalent value reflecting the output power, and carrying out feedback regulation on the on-off time ratio of a switching tube in the DC-AC inversion module in one period according to the equivalent value of the output power so as to regulate the output power of the DC-AC inversion module.
In this embodiment, the calculation of the output power equivalent value is calculated based on an equivalent impedance obtained by equating all circuits of the secondary side to the primary side, where the equivalent impedance is: zK(ii) a Thus, the equivalent value calculation formula of the power transmitted from the primary side of the transformer to the secondary side of the transformer, namely the output power, is as follows:
Pdo＝Iyf 2×Re(ZK)
in the formula, PdoIs the equivalent value of the output power; said IyfIs the effective value of the current flowing through the primary coil within the sampling time period; zKThe equivalent impedance is obtained after all circuits of the secondary side of the transformer are equivalent to the primary side.
In the preferred embodiment, based on the principle of an equivalent circuit, the estimation of the overall output power of the transformer can be realized by calculating the power consumed by the equivalent impedance at the primary side, and a new idea is provided for the feedback regulation of the output power of the transformer.
In this embodiment, the output power adjusting module includes an equivalent impedance calculating unit and a power adjusting unit; the equivalent impedance calculation unit can calculate the value of the equivalent impedance in the corresponding sampling period by detecting the voltage and the current of the output end of the DC-AC inversion module based on an energy conservation model; the specific process of calculating the equivalent impedance is as follows:
(1) setting a fixed sampling period, and sampling the voltage and the current value of the output end of the DC-AC inversion module in the sampling period;
(2) the voltage and the current obtained by the detection are sent to a zero-crossing detection unit, and the time t when the output end voltage of the DC-AC inversion module passes through the zero point is obtainedm(ii) a Obtaining the time t of the zero crossing of the current at the output endn(ii) a Calculating an offset phase angle according to the angular frequency of the voltage and current of the DC-AC inversion module
Is calculated by the formula
And w is the angular frequency of the voltage and current at the output end.
(3) Calculating the equivalent impedance of the secondary side to the primary side according to the obtained electric quantities and the internal resistance in the primary side coil of the transformer:
in the formula, ZKIs the equivalent impedance of the secondary side to the primary side; voThe effective value of the voltage at the output end of the DC-AC inversion module in a sampling period is obtained; i isoThe effective value of the current at the output end of the DC-AC inversion module in a sampling period is obtained; theta is an offset phase angle; i isxThe effective value of the current flowing through the primary side coil in a sampling period is obtained; r islIs the internal resistance of the primary coil; i isomaxThe maximum value of the current of the output end of the DC-AC inversion module in one sampling period is obtained; i isxminThe maximum value of the current flowing through the primary side coil in one sampling period is obtained; cyA resonant capacitor on the primary side; l isyIs the inductance of the primary coil; cfA resonant capacitor as a secondary side; l isfIs the inductance of the secondary winding.
In the preferred embodiment, based on the law of conservation of energy, a calculation formula of equivalent impedance of all circuits on the secondary side relative to the primary side is designed, the equivalent impedance obtained by the calculation formula is used for calculating equivalent power, the precision requirement of estimating the output power of the transformer is met, the calculation formula is simple, the calculation amount is small, the equivalent impedance can be quickly obtained in a sampling period, and the response speed of the subsequent power regulation is ensured.
In this embodiment, the positive electrode of the input end of the DC-AC inverter module is connected to controllable switching tubes S1 and S3; the negative electrode of the input end of the DC-AC inversion module is connected with controllable switching tubes S2 and S4; the S1 and S2 form one bridge arm, and the S3 and S4 form the other bridge arm; the ratio of the on time to the off time of the controllable switch tube in one switching period is controlled by the driving circuit, and the trigger signals of the controllable switch tubes S1 and S4 are the same and are switched on or switched off simultaneously; the trigger signals of the control switch tubes S2 and S3 are the same and are switched on or off simultaneously; the controllable switch tube S1 is complementary to the trigger signal of the controllable switch tube S2.
In this embodiment, the power adjusting unit adjusts a ratio of on-time to off-time of the controllable switch tube in a switching period, so as to adjust and control the output power, and the specific process is as follows:
(1) the sampling monitoring unit sets a sampling period, and samples the current value flowing through the primary coil in one sampling period; and according to the equivalent impedance obtained by the calculation, calculating the equivalent of the secondary side to the primary side to obtain the equivalent power Pdo；
(2) Setting a power reference value Prck(ii) a When the equivalent power P is detecteddoLess than the power reference value PrckAnd the zero crossing point time of the current flowing through the output end of the DC-AC inversion module is the same as the zero crossing point time of the resonance current flowing through the primary coil, the direction of the current of the primary coil at the next sampling time is detected, if the current is in the forward direction (flows to the secondary side), control signals for switching on S1 and S4 and switching off S2 and S3 are sent to the driving circuit, and then the switching on and switching off of the switching tube are controlled; if the current is in the reverse direction (the current flows to the output end of the DC-AC inversion module), control signals for turning off S1 and S4 and turning on S2 and S3 are sent to the driving circuit, and then the switching tube is controlled.
When detecting that the equivalent power is larger than the power reference value PrckAnd the zero crossing point time of the current flowing through the output end of the DC-AC inversion module is the same as the zero crossing point time of the resonance current flowing through the primary coil, the direction of the current of the primary coil at the next sampling time is detected, if the current is in the forward direction (flows to the secondary side), a control signal for switching on S1 and switching off S2, S3 and S4 is sent to the driving circuit, and further the switching tube is controlled; if the current is in the reverse direction (flows to the output end of the DC-AC inversion module), the control signals of turning off S1, turning on S2 and turning on S3 are sent to the driving circuit, and further, the driving circuit is further connected with the control signals of turning on S4Realize the control switch tube.
(3) In the switching period of the switching tube, the sampling monitoring unit can perform sampling for multiple times, and the more the sampling times are, the more accurate the on-time and off-time of the controllable switching tube can be controlled in real time, and then the output power is corrected until the calculated output power tracks the power reference value Prck。
In the preferred embodiment, a power regulating unit is established, and different control strategies are selected to control the on-off of a fully-controlled high-frequency switching tube in a DC-AC inverter circuit according to the reflected secondary equivalent power, the DC-AC inverter module and the voltage and current changes flowing in a coil, so that the power tracking is real-time and efficient.
In the embodiment, a magnetic coupling wireless power transmission conversion technology is provided to realize a direct current-direct current transformer; the wireless power transmission can be carried out, so that the application occasion is more flexible, and the circuit has a simple, reliable and practical structure. The direct current-direct current transformer can be widely applied to the application fields of high-voltage direct current transmission systems, new energy sources, direct current energy wireless transmission, wireless scheme direct current impedance transformation circuits, certain special experiments and the like; and the circuit model of the transformer system is analyzed, and a direct current-direct current transformer system capable of controlling and adjusting the working frequency and the output power of wireless electric energy transmission is provided, so that the wireless electric energy transmission with high efficiency and controllable transmission power between two sides of the transformer is realized.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be analyzed by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (4)
1. A direct current transformer system based on magnetic coupling wireless power transmission, characterized by comprising:
the DC-AC inversion module is used for converting input direct current into primary side high-frequency alternating current;
the wireless power transmission module comprises a primary side resonance module and a secondary side resonance module, wherein the primary side resonance module receives the high-frequency alternating current, converts the high-frequency alternating current into a strongly coupled electromagnetic field and sends the strongly coupled electromagnetic field to the secondary side resonance module; the secondary resonance module receives the electromagnetic field and converts the electromagnetic field into secondary high-frequency alternating current;
the rectification filtering module is used for converting the secondary high-frequency alternating current rectification into direct current and filtering out high-frequency components;
the positive and negative ends of the direct current input are connected with the input end of the DC-AC inversion module; the output end of the DC-AC inversion module is connected with the input end of the wireless power transmission module; the output end of the wireless power transmission module is connected with the input end of the rectification filter module; the rectification filtering module obtains the finally output direct-current voltage; the dc transformer system further comprises: the DC-AC inverter comprises a sampling monitoring unit, a zero-crossing detection unit, a driving module and a control module, wherein the sampling monitoring unit is used for sampling and monitoring the voltage and the current flowing through the input end and the output end of a DC-AC inverter module, the voltage and the current of the output end of a rectifying filter; the zero-crossing detection unit is used for acquiring the time when the monitored voltage and current pass through a zero point in a resonance period; the control module is used for controlling the working frequency of the DC-AC inversion module and the output power of the DC transformer; the driving module is controlled by the control module and drives a switching tube in the DC-AC inversion module to be switched on or switched off; the control module comprises a state judgment unit for judging whether the wireless power transmission module is in a resonance state and a frequency correction unit for adjusting the working frequency of the DC-AC inversion module to be adaptive to the resonance frequency during detuning transmission, and the specific process of adjusting the working frequency of the DC-AC inversion module by the control module is as follows:
(1) and (3) state judgment: the sampling monitoring unit is used for sampling and monitoring the voltage and the current of the input end of the DC-AC inversion module and sending a sampling monitoring result into the state judgment unit, the voltage and the current of the input end which are sampled and monitored are passed through the multiplier and the zero value comparator, if the product of the voltage and the current is more than 0, the wireless electric energy transmission module is in a resonance state, and at the moment, the working frequency of the DC-AC inversion module adapts to the resonance frequency of the wireless electric energy transmission module; otherwise, the state judgment unit judges that the wireless power transmission module is in the detuning state and enters the step (2);
(2) and (3) establishing an adjusting function: the zero-crossing detection unit calculates the zero-crossing time of the input end voltage and the current of the DC-AC inversion module, and establishes a frequency regulation function according to the zero-crossing time, wherein the frequency regulation function is as follows:
U_t＝U_set/γ×√(2×π)×e^((-(π×〖〖[f〗_k×e^|t_j-t_i|-f_z]〗^2)/(2×γ^2)))
in the formula, the U _ t voltage feeds back a regulating value; f _ k is the switching frequency of a switching device in the DC-AC inversion module; t _ i is the moment of zero crossing of the input voltage of the DC-AC inverter module; t _ j is the moment when the input current of the DC-AC inversion module crosses zero; u _ set is a known voltage comparison value and represents a set voltage adapted to the resonant frequency of the wireless power transmission module; gamma is a frequency variance adjustment factor; f _ z is the resonant frequency of the wireless power transmission module;
(3) adjusting the switching frequency of a switching device in the DC-AC inversion module according to the frequency adjusting function, so that the switching frequency returns to the frequency corresponding to the resonant frequency of the wireless power transmission module; the switching frequency of the switching device is specifically adjusted in the following process:
1) acquiring a resonance frequency sigma neighborhood located in a wireless power transmission module as follows: [ (f) represents [ f ] z-sigma, f _ z + sigma ]; the endpoint frequency of the neighborhood corresponds to the same voltage feedback adjustment value on the frequency adjustment function and is recorded as a reference voltage adjustment value U _ ck;
2) setting the working frequency of the DC-AC inversion module obtained by the ith sampling as f _ ki; calculating a voltage feedback adjustment value U _ ti corresponding to the ith adjustment according to the zero-crossing time of the voltage and the current of the input end of the DC-AC inverter circuit obtained by sampling; comparing the calculated voltage feedback adjustment value U _ ti with a reference voltage adjustment value U _ ck, and updating the existing working frequency f _ ki by adopting different strategies according to the relative size of the working frequency f _ (k (i-1)) of the DC-AC inverter circuit obtained by sampling for the (i-1) th time and the working frequency f _ ki of the DC-AC inverter circuit obtained by sampling for the (i-1) th time and the relative size of the voltage feedback adjustment value U _ ti and the reference voltage adjustment value U _ ck, so that the existing working frequency f _ ki approaches to the resonant frequency f _ z; triggering a driving circuit through processing the updated working frequency, and adjusting the frequency of the DC-AC inversion module;
3) when the voltage feedback adjustment value U _ ti corresponding to the ith adjustment obtained through calculation is equal to the voltage comparison value U _ set, the adjustment process is finished, and the switching frequency of the switching device in the DC-AC inverter module is returned to the frequency corresponding to the resonant frequency of the wireless power transmission module; otherwise, continue with step 2).
2. The direct-current transformer system based on magnetic coupling wireless power transmission of claim 1, wherein the DC-AC inverter module is a single-phase full-bridge inverter circuit, and comprises two parallel-connected bridge arms, and each bridge arm is connected with two fully-controlled transistors in series.
3. The direct current transformer system based on magnetic coupling wireless power transmission of claim 1, wherein the wireless power transmission module comprises: inductance of LyPrimary side coil and capacitor CyInductance is LfSecondary winding and capacitor Cf(ii) a The primary coil and the capacitor CyThe DC-AC inverter module is connected with the output end of the DC-AC inverter module after being connected in series to form the primary side, namely the input end, of the wireless power transmission module; the secondary coil and the capacitor CfAnd the secondary side, namely the output end, of the wireless power transmission module is formed by connecting the two modules in parallel.
4. The magnetic coupling wireless power transmission-based direct current transformer system according to claim 1, wherein the rectifying and filtering module comprises a full bridge rectifying circuit and an LC filter circuit, an input end of the full bridge rectifying circuit is connected with an output end of the wireless power transmission module, and an output end of the full bridge rectifying circuit is connected with the LC filter circuit and then output.
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