CN118174468A - Phase-shifting modulation method and system of EC-BWPT system under coupling capacitance change - Google Patents
Phase-shifting modulation method and system of EC-BWPT system under coupling capacitance change Download PDFInfo
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Abstract
The invention relates to the technical field of electric field coupling bidirectional wireless power transmission (EC-BWPT), and particularly discloses a phase shift modulation method and a phase shift modulation system of an EC-BWPT system under the change of coupling capacitance, and in order to enable the EC-BWPT system to realize expected power transmission when the coupling capacitance is changed, the method and the system adjust the relative phase angles of output voltages of a primary side converter and a secondary side converter through a secondary side controller under the condition of presetting the power size and the power direction, and compensate the coupling capacitance change caused by different transmission distances and offset and simultaneously determine the power transmission direction so as to realize system resonance. The desired power of the system is then obtained by adjusting the internal phase angle of the secondary side converter. Finally, the feasibility and the effectiveness of the proposed phase shift tuning and power flow control strategy of the EC-BWPT system are verified through simulation.
Description
Technical Field
The invention relates to the technical field of electric field coupling bidirectional wireless power transmission (EC-BWPT), in particular to a phase-shift modulation method and a phase-shift modulation system of an EC-BWPT system under the change of coupling capacitance.
Background
The wireless power transmission (wireless power transfer, WPT) technology refers to the integrated application of electrotechnology theory, power electronics technology, control theory, and uses magnetic fields, electric fields, microwaves, etc. to realize the transmission of power from a power grid or a battery to electric equipment in a non-electric contact manner. The technology has the advantages of convenience and safety in power supply access, higher reliability and safety, application in special environment conditions such as coal mine drilling, aerospace and the like, and becomes a research hotspot in the fields of electrical engineering and automation. At present, the technical development of magnetic field coupling wireless power transmission (Magnetic Coupled Wireless Power Transfer, MC-WPT) is mature, and the technology has been popularized and applied in various fields such as electric automobiles, biomedicine, household appliances, underwater equipment and the like.
Electric-field Coupling Wireless Power Transfer (EC-WPT) technology of Electric field coupling wireless power transmission using Electric field as transmission carrier is similar to magnetic field in many characteristics, and the two are dual in basic theory, so that high attention of expert scholars at home and abroad is increasingly drawn. The EC-WPT system adopts an electric field as an electric energy transmission medium, and the metal polar plates form a coupling mechanism, so that the EC-WPT system has the following characteristics: the coupling mechanism is simple, light, thin, easy to change in shape and low in cost; most of electric flux of the electric field coupling mechanism is distributed between the electrodes in the working state, so that the electromagnetic interference to the surrounding environment is low; can transfer energy across metal obstacles; there is little eddy current loss generated on the metal conductor around and between the coupling mechanisms.
With the rapid growth of the number of electric vehicles (ELECTRIC VEHICLES, EVS), energy sharing between the grid and the electric vehicles has become an attractive area of research, and the two-way wireless power transfer (Bidirectional Wireless Power Transfer, BWPT) technology is a key technology in this area. The vehicle-mounted power battery energy is used for participating in peak clipping and valley filling scheduling operation of the power grid, so that the EVs charging convenience is improved, the power grid burden is reduced, the power grid quality is improved, and the power grid stability is enhanced. In recent years, most of research on EC-WPT technology using an Electric field as a transmission carrier is limited to unidirectional power transmission, and Electric field coupling bidirectional wireless power transmission (Electric-field Coupling Bidirectional Wireless Power Transfer, EC-BWPT) technology starts later and related research is less.
The block diagram of a typical EC-BWPT system is shown in fig. 1, consisting of two-way converters (primary and secondary) on both sides, a resonant network (primary and secondary), a coupling mechanism (primary and secondary), and a power source (primary and secondary). The power source may be a power grid or a direct current battery energy storage device. For an EC-BWPT system for power flow between a power grid and a battery energy storage device, the power grid is generally used as a primary side of the system, and the DC battery energy storage device is used as a secondary side of the system. The bidirectional high-frequency converter of the primary side and the secondary side of the system is used for driving the coupling mechanism and the resonance network.
However, since the coupling capacitance value of the EC-BWPT system is small (pF level), the polar plate is slightly deviated, the coupling capacitance value is very easy to change, and the parameter sensitivity is very high, so that the power transmission performance of the system is obviously reduced. At present, students at home and abroad have proposed some research methods to solve the problem of coupling capacitance change, mainly including compensation network tuning control, frequency tuning control, compensation topology conversion and the like. In compensation network tuning control, the adoption of adjustable inductance and capacitance matrixes increases the overall volume of the system, and in addition, the dynamic switching of the tuning control of the switch increases the loss and complexity of the system. In frequency tuning control, frequency bifurcation and frequency splitting may be caused when coupling capacitance or system parameters are changed, so that a plurality of resonance frequency points exist in the system, and other resonance points may be automatically tracked by adopting frequency tuning control, so that the system cannot realize the expected power control effect. In the compensation topology transformation, although a proper compensation network design can avoid a relatively complex frequency tracking technology and no additional circuit is added, the coupling capacitance or load change can be compensated only in a limited parameter change range, and the system circuit design needs to meet specific conditions or requirements to realize the effect of approximate constant output.
Therefore, the existing methods for compensating network tuning control, frequency tuning control, compensating topology conversion and the like for solving the coupling capacitance change have corresponding disadvantages. At present, a technology which does not add additional circuit elements, does not have a compensation network switching design and does not have a complex control circuit is lacking, and the problem of coupling capacitance change caused by coupling polar plate offset dislocation of an EC-BWPT system can be solved.
Disclosure of Invention
The invention provides a phase shift modulation method and a phase shift modulation system of an EC-BWPT system under the change of coupling capacitance, which solve the technical problems that: on the premise of not adding additional circuit elements, not compensating network switching design and not having complex control circuits, the problem of coupling capacitance change caused by coupling polar plate offset dislocation of the EC-BWPT system is solved.
In order to solve the technical problems, the invention provides a phase shift modulation method of an EC-BWPT system under the change of coupling capacitance, which comprises the following steps:
detecting whether the coupling capacitance of the EC-BWPT system is changed when the coupling capacitance is opposite to the coupling pole plate, if so, adjusting an adjustable delay phase shift angle delta between a primary side control signal and a secondary side control signal to carry out phase shift tuning control, and if not, continuing to detect;
After the phase-shifting tuning control is finished, detecting whether the actual output power P o of the EC-BWPT system is equal to the expected output power P ref, if not, adjusting the phase-shifting angle delta and the internal phase-shifting angle of the secondary side converter And (5) performing bidirectional power flow adjustment, and if so, continuing detection.
Further, the process of adjusting the adjustable delay phase shift angle delta between the primary side control signal and the secondary side control signal for phase shift tuning control specifically comprises the steps of:
Setting the switching drive frequency f s of the EC-BWPT system, the internal phase angle of the primary side converter using a set of default values And internal phase shift angle/>, of the secondary side converterAn adjustable delay phase angle delta, a preset power P set and a desired power P ref, wherein And delta is selected from the range/> δ∈(0,2π)；
Operating the EC-BWPT system according to the preset power P set and the relative phase angle theta between the primary side resonance voltage and the secondary side resonance voltage corresponding to the transmission direction, which is theta 1, wherein theta 1 is equal to the current adjustable delay phase angle delta 1;
The actual output power P o is obtained by detecting the secondary DC current I o and is compared with the preset power P set, if P o is not equal to P set, the power is kept And/>The adjustable delay phase angle delta is unchanged and adjusted until P o is equal to P set, finally delta is changed from delta 1 to delta 2, and the relative phase angle theta between the primary side resonance voltage and the secondary side resonance voltage is changed from theta 1 to theta 2, so that the EC-BWPT system is in a resonance state;
Relative phase angle θ and phase angle The relationship between the adjustable delay phase angle delta is as follows:
further, the phase shift angle delta and the internal phase shift angle of the secondary side converter are adjusted The process of bidirectional power flow regulation is specifically as follows:
Maintaining the relative phase angle theta 2 of the output voltages of the primary and secondary side converters constant, and adjusting the internal phase angle of the secondary side converter Until the actual output power P o is equal to the desired output power P ref, finally the internal phase angle/>, of the secondary converter is madeFrom/>To/>Delta changes from delta 2 to delta 3,/>
Further, the EC-BWPT system comprises a primary side and a secondary side, wherein the primary side comprises a primary side direct current power supply, a primary side converter, a primary side resonant network and a primary side polar plate which are sequentially connected, and the secondary side comprises a secondary side polar plate, a secondary side resonant network, a secondary side converter and a secondary side direct current power supply which are sequentially connected;
The primary side converter and the secondary side converter are reversible full-bridge converters composed of 4 switching tubes, all the switching tubes of the primary side converter and the secondary side converter work at a duty ratio of 50% and a switching frequency f s, and an internal phase shift angle between two branches of the primary side converter is The internal phase shift angle between two branches of the secondary side converter is/>
Further, by controlling the transmission direction of the θ control power, power is transmitted from the secondary side to the primary side when 0 ° < θ < 180 °, and power is transmitted from the primary side to the secondary side when-180 ° < θ <0 °.
Further, the primary side resonance network and the secondary side resonance network both adopt LCLC resonance networks.
The invention also provides a phase shift modulation system of the EC-BWPT system under the change of coupling capacitance, which is characterized in that: the phase-shift modulation method applied to the EC-BWPT system under the change of the coupling capacitance comprises a primary side controller connected with the primary side converter and a secondary side controller connected with the secondary side converter; the primary side controller is used for generating a primary side driving signal, and the primary side driving signal acts on the primary side converter to enable the internal phase shift angle of the primary side converter to beThe secondary side controller is used for generating a secondary side driving signal, and the secondary side driving signal acts on the secondary side converter, so that the internal phase shift angle of the secondary side driving signal is/>And an adjustable delay phase shift angle between the primary side control signal and the secondary side control signal is delta.
Preferably, the secondary side controller adopts a PID control mode to carry out phase shift tuning control and bidirectional power flow adjustment.
In order to enable the EC-BWPT system to realize expected power transmission when the coupling capacitance changes, the invention provides a EC-BWPT system based on a bilateral LCLC resonant network, and provides a phase-shift modulation method and a phase-shift modulation system of the EC-BWPT system under the condition of changing the coupling capacitance. The desired power of the system is then obtained by adjusting the internal phase angle of the secondary side converter. Finally, the feasibility and effectiveness of the proposed phase shift tuning and power flow control strategy of the EC-BWPT system are verified through experiments.
Drawings
FIG. 1 is a block diagram of an exemplary EC-BWPT system provided in an embodiment of the present invention;
FIG. 2 is a block diagram of the structure of an EC-BWPT system of a bilateral LCLC compensation topology provided by an embodiment of the present invention;
FIG. 3 is a schematic structural dimension of a coupling capacitor according to an embodiment of the present invention;
FIG. 4 is a circuit model diagram of a capacitive coupler provided by an embodiment of the present invention;
FIG. 5 is a simplified circuit diagram of an equivalent current source model provided by an embodiment of the present invention;
FIG. 6 shows the values of θ and A relationship diagram between delta;
FIG. 7 is a graph of the variation of the coupling self-capacitance and the equivalent mutual capacitance provided by an embodiment of the present invention;
FIG. 8 is a graph of transmission power versus relative phase angle provided by an embodiment of the present invention;
FIG. 9 is a graph of the relative phase angle as a function of coupling plate spacing or lateral offset provided by an embodiment of the present invention;
FIG. 10 is a block diagram of phase shift tuning and power flow control of an EC-BWPT system provided by an embodiment of the present invention;
FIG. 11 is a timing diagram of phase-shifting tuning and power control drive signals provided by an embodiment of the present invention;
FIG. 12 is a flow chart of phase shift tuning and power flow control provided by an embodiment of the present invention;
FIG. 13 is a diagram of drive signals under phase shift tuning and power control provided by an embodiment of the present invention;
FIG. 14 is a graph of resonant voltage and current waveforms under phase-shifting tuning and power control provided by an embodiment of the present invention;
Fig. 15 is a diagram of transmission power of a system under phase shift tuning and power control provided by an embodiment of the present invention.
Detailed Description
The following examples are given for the purpose of illustration only and are not to be construed as limiting the invention, including the drawings for reference and description only, and are not to be construed as limiting the scope of the invention as many variations thereof are possible without departing from the spirit and scope of the invention.
The electric field coupling bidirectional wireless electric energy transmission (EC-BWPT) system is suitable for power grids, electric vehicles or battery energy storage devices and the like, and realizes energy interaction and sharing between the electric power grids and the electric vehicles or the battery energy storage devices. In a charging system based on the EC-BWPT technology, offset dislocation of a coupling polar plate or change of transmission spacing are unavoidable, and the transmission performance of the system is greatly affected by coupling capacitance. In order to enable the system to realize the desired power transmission when the coupling capacitance changes, an EC-BWPT system based on a double-sided LCLC resonant network, a phase-shifting tuning and power modulation method and a corresponding system are provided.
The present example was analyzed and designed with the EC-BWPT system of the double sided LCLC topology.
In order to achieve energy interaction between the power supply and the battery energy storage device, the current and voltage stress of circuit elements near the coupling electrode plates is reduced, as the power of the double-sided LCLC topology is proportional to the coupling coefficient and provides good performance in the event of coupling misalignment. The double sided LCLC resonant network of the EC-BWPT system is shown in figure 2. L p1,Lp2,Lr1,Lr2 is the self inductance of the coil, C p1,Cp2,Cr1,Cr2 is the compensation capacitance, C d and C o are the dc filter capacitance. V d is the DC output voltage, typically kept constant by a grid-tied bi-directional AC-DC converter. V o is the dc voltage of the battery of the electric vehicle, V p and V r are the ac resonant voltages generated by the full-bridge converters on the primary side and the secondary side, and i p and i r are the ac resonant currents on the primary side and the secondary side. Under the action of the interaction electric field, electric energy is wirelessly transmitted between the polar plates. The primary and secondary circuits are implemented with nearly identical electronic components, including an H-full bridge converter (reversible rectifier bridge) and a double sided LCLC resonant network, to facilitate bi-directional power flow between electronic devices.
The capacitive coupler comprises four metal plates P 1～P4, the structure and dimensions of which are shown in fig. 3. Plates P 1 and P 3 are placed on the primary side as power transmitters, and plates P 2 and P 4 are placed on the secondary side as power receivers. The side length of the polar plate P 1-P4 is l=300 mm, the distance between the polar plates of the primary side and the secondary side is d=10 mm, the distance between the polar plates P 1-P2 and the polar plate P 3-P4 is m=150 mm, and the thickness of all polar plates is 2mm. There is a capacitive coupling between every two plates, resulting in six coupling capacitances C 12～C34, as shown in fig. 4. It is further simplified to a two-port model, where C x1 and C x2 are self-capacitance and C M is equivalent mutual capacitance.
Fig. 5 shows a simplified circuit diagram of an EC-BWPT system with an equivalent current source model. The equivalent current source associated with the capacitive voltage represents the capacitive coupling between the primary and secondary plates. The equivalent self-capacitance and capacitive coupling coefficient k c can be expressed as:
Wherein the method comprises the steps of
The frequency of the double-sided LCLC resonant circuit of the EC-BWPT system is omega, and then the resonant relationship of the circuit can be obtained:
where ω=2pi f s,fs is the operating frequency.
All switching tubes (S1-S4, S5-S8) of the primary and secondary converters are operated at a duty cycle of 50% and a switching frequency f s to produce resonant voltages v p and v r with an internal phase shift angle between the two legs of each converter ofAnd/>As shown in fig. 6, δ is an adjustable delay phase shift angle between the primary side control signal and the secondary side control signal. θ is the relative phase angle of the primary and secondary resonant voltages. Generally,/>Delta epsilon (0, 2 pi), theta can be determined by delta,/>And/>Is modulated by any combination of relative phase angle θ and phase shift angle/>And δ are shown in fig. 6 (a) and 6 (b). (a) correspondence of FIG. 6/>In case of/>FIG. 6 (b) corresponds/>In case of/>
To obtain a mathematical model of the power flow of the proposed EC-BWPT system, the fundamental expression of v p、vr is given by
The relationship between current and voltage for the EC-BWPT system shown in fig. 5 can be deduced as follows, according to the KVL equation:
Wherein the method comprises the steps of
And (3) making:
Thus, the resonant current of the secondary side can be expressed as:
wherein:
the transmission power expression of the system can be given by:
When the system satisfies the resonance relationship, the resonance current and transmission power of the secondary side can be expressed as:
thus, given the circuit parameters and the dc input voltage, it is apparent from equation (11) that the secondary side resonant current depends only on the primary side resonant voltage V p, and is independent of the secondary side resonant voltage V r. Due to The secondary side transmission power of the system can be controlled/>And/>To change the converter output voltage or adjust the relative phase angle θ, the power transfer direction depending only on θ. When 0 DEG < θ < 180 DEG, P r >0, the retard phase angle enables power transfer from the secondary side to the primary side; when-180 DEG < θ <0 DEG, P r <0, the lead phase angle causes power to be transferred from the primary side to the secondary side. In addition, the system achieves maximum power transfer when θ is ±90°.
However, in practical applications, a change in the position of the wireless powered device may result in a coupling offset or a change in transmission spacing, which may result in a change in coupling capacitance. Even in the case of a perfectly aligned coupling mechanism, the coupling capacitance may change due to a change in environmental parameters.
By the coupling mechanism parameters of fig. 3, and by combining the system circuit parameters given in table 1, fig. 7 shows the variation curves of the coupling self-capacitance and the equivalent mutual capacitance when the coupling polar plate is laterally shifted or the coupling transmission distance is changed.
TABLE 1 Circuit parameters of EC-BWPT System
Wherein (a) of fig. 7 shows a graph of the coupling self-capacitance and the equivalent mutual capacitance as a function of the transmission distance d in the case where the coupling plate is not horizontally offset; fig. 7 (b) shows a graph of the variation of the coupling self-capacitance and the equivalent mutual capacitance with the lateral offset distance b of the coupling plate, for a d of 10 mm. It can be seen that as b or d increases, the coupling self capacitance C x1、Cx2 and the equivalent mutual capacitance C M decrease. The trend of C x1 and C x2 is consistent because the influence of the lateral offset of the coupling plates and the change in the transmission distance on the two coupling self-capacitances is the same in the symmetrical coupling mechanism.
According to equation (11), for a given system operating frequency, circuit component parameters, and ac resonant voltage, when b and d change, a graph of the change between the system secondary side transmission power P r and the relative phase angle θ is shown in fig. 8, where fig. 8 (a) corresponds to d and fig. 8 (b) corresponds to b. As can be seen from fig. 8, when the coupling capacitance changes, the system has different lateral offset distances or coupling transmission distances corresponding to different relative phase angles at the same power output. Thus, power variations caused by coupling capacitance variations can be overcome by adjusting the relative phase angle of the system converter output voltage. The transmission power of the system is set at an expected value of 80W, and fig. 9 specifically shows a graph of variation θ in the case where the coupling plate offset distance b and the coupling plate spacing d are varied, where fig. 9 (a) corresponds to d and fig. 9 (b) corresponds to b. For example, as shown in fig. 9 (a), when d is 20mm, θ is 28 ° or 152 °, and when d is 10mm, the corresponding relative phase angle θ is 14.1 ° or 165.9 °. Thus, the relative phase angle should be adjusted from 28 ° to 14.1 °, or the relative phase angle 152 ° to 165.9 °, i.e., the system resonance state can be restored.
Thus, based on the above mathematical analysis of resonance and detuning conditions, the system can be brought to a preset power by controlling the relative phase angle θ.
The EC-BWPT system phase-shifting tuning and power flow control block diagram based on the bilateral LCLC compensation network is shown in figure 10, and comprises an original secondary side controller, and a phase-shifting tuning and power flow control two control loops are arranged in the secondary side controller of the secondary side of the system. The primary side controller is used for generating a primary side driving signal, and the primary side driving signal acts on the primary side converter to enable the internal phase shift angle of the primary side converter to beThe secondary side controller is used for generating a secondary side driving signal, and the secondary side driving signal acts on the secondary side converter so that the internal phase shift angle of the secondary side driving signal is/>And an adjustable delay phase shift angle between the primary side control signal and the secondary side control signal is delta. According to the analysis, firstly, the relative phase angle corresponding to the planned power is detected and compared with the actual phase angle, so that the delay phase angle delta is adjusted, and the system tuning is realized by adjusting the phase shift angle under the change of the coupling capacitance. After the system reaches resonance, the relative phase angle θ is kept unchanged by adjusting the phase shift angles δ and/>, of the secondary side converterThereby adjusting the power.
The timing and flow diagrams of the drive signals for system phase shift tuning and power flow control are shown in fig. 11 and 12. The phase shift tuning control aiming at the dislocation of the coupling polar plates of the system operates firstly, and then the power adjustment is carried out by adjusting the internal phase angle, so that the expected power and the expected power direction of the system are achieved. It can be seen that the secondary side controller performs phase shift tuning control and bidirectional power flow regulation in a PID control mode.
After the frequency tuning control program is started, the switch driving frequency f s and the internal phase angle of the system are set by using a set of default valuesAnd/>Delay phase angle delta, preset power P set and desired power P ref. Wherein/>Namely, two pairs of bridge arms of the primary side converter and the secondary side converter are alternately conducted at 180 degrees.
The first stage is the phase shift tuning control of the system. When the coupling polar plate of the system shifts or the transmission distance changes, the transmission power of the system changes with the corresponding relative phase angle.
The system must therefore first tune the circuit. Firstly, the system operates according to the preset power magnitude and the relative phase angle theta 1 corresponding to the transmission direction, at the moment theta 1＝δ1, the actual output power P o is obtained by detecting the secondary side direct current I o and is compared with the preset power, and according to the comparison result, V p、Vr is kept unchanged, namelyAnd/>The delay phase shift angle delta of the secondary side converter leg control signal is adjusted so that delta changes from delta 1 to delta 2 and theta changes from theta 1 to theta 2, thereby placing the system in resonance with the primary and secondary side drive signals and the resonant voltage waveforms changing as shown by the orange dashed line in fig. 11.
Then, according to the expected power of the system, the relative phase angles theta 2 of the output voltages of the primary and secondary side converters are kept constant, the phase shift between each branch of the secondary side converter is adjusted, and the internal phase angle is changedSo that delta is changed from delta 2 to From/>To/>Thereby changing the magnitude V r of the secondary side resonance voltage to obtain the desired power magnitude P ref, and the primary and secondary side driving signals and the waveform change of the resonance voltage are shown as blue dotted lines in fig. 11.
In order to verify the feasibility of the phase shift tuning and power flow control method and system of the EC-BWPT system provided by the invention, a 100W experimental device is built according to a system circuit shown in FIG. 2. The system includes primary and secondary full bridge converters controlled by two controllers. The controller core has been fully HDL encoded and implemented on a Cyclone II FPGA. The full bridge converter implemented with GaN power modules can operate at MHz.
The circuit parameters of the experimental prototype were designed symmetrically from primary side to secondary side and summarized in table 2. Parallel compensation capacitors C r1、Cr2、Cp1 and C p2 use high voltage multilayer Surface Mount Device (SMD) ceramic capacitors. The compensating inductances L r1、Lr2、Lp1 and L p2 are made of litz wire wound on PVC pipes.
TABLE 2 Circuit parameters of EC-BWPT System
According to the phase shift control method shown in fig. 10, fig. 13 shows a simulation waveform when a 15mm transmission spacing exists between the primary and secondary side coupling plates. Fig. 14 shows the resonant voltage and current waveforms under phase-shift tuning and power control, and fig. 15 shows the system transmit power under phase-shift tuning and power control. According to Maxwell simulation results, coupling self-capacitance C x1、Cx2 decreases from 47.8pF to 33.9pF and coupling mutual capacitance C M decreases from 44.8pF to 30.2pF. At the same time, the change in coupling capacitance causes the relative phase angle to change from 32 ° to 58 °, while the transmission power is controlled to a constant value, while the magnitude of Vr increases slightly. Thus, the controller adjusts the retard phase angle from 32 ° to 58 ° by adjusting the switching transistors S5 and S8, and since the secondary side converter is 180 ° complementarily turned on in the initial stage, the relative phase angle is adjusted from 32 ° to 58 ° in correspondence with the retard phase angle change angle to adjust the 100W constant power transmission to the primary side, as shown in fig. 13 (a), fig. 14 (a) to fig. 13 (b), fig. 14 (b), the power change is shown before and after t o in fig. 15, the system achieves resonance in the time t o～t1 by adjusting the relative phase angle, and the system preset power is adjusted to 100W.
After the system reaches a resonant state, the power is controlled by changing the magnitude of the secondary side resonant voltage. As shown in fig. 13 (c) and 14 (c), in order to obtain desired power, the switching tubes S5 to S8 are adjusted to change the internal phase angle of the secondary converter while maintaining the relative phase angle unchangedThe system achieves a power change from 100W to 90W at time t 1.
In summary, the invention provides a phase shift tuning and power flow control method and a system for an EC-BWPT system based on a bilateral LCLC compensation network, which effectively solve the problem that the transmission power of the system is changed due to the change of coupling capacitance caused by the lateral offset of a coupling polar plate or the change of transmission distance. The power change caused by the change of the coupling capacitance is overcome by adjusting the relative phase angles of the output voltages of the primary side converter and the secondary side converter, so that the system is in a resonance state before the power flow is adjusted, and the power is adjusted by adjusting the internal phase angle of the secondary side converter, thereby realizing the control of the power transmission direction and the power transmission size and ensuring that the system can adjust the power stably. Simulation and results verify the implementation of phase-shifting tuning control and bi-directional power flow regulation. The result shows that the proposed phase-shifting tuning control method can be effectively applied to bidirectional power flow regulation of the system, and an effective solution is provided for the coupling capacitance change of the EC-BWPT system.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (8)
1. The phase shift modulation method of the EC-BWPT system under the change of coupling capacitance, the EC-BWPT system refers to an electric field coupling bidirectional wireless power transmission system, and is characterized in that the method comprises the following steps:
detecting whether the coupling capacitance of the EC-BWPT system is changed when the coupling capacitance is opposite to the coupling pole plate, if so, adjusting an adjustable delay phase shift angle delta between a primary side control signal and a secondary side control signal to carry out phase shift tuning control, and if not, continuing to detect;
After the phase-shifting tuning control is finished, detecting whether the actual output power P o of the EC-BWPT system is equal to the expected output power P ref, if not, adjusting the phase-shifting angle delta and the internal phase-shifting angle of the secondary side converter And (5) performing bidirectional power flow adjustment, and if so, continuing detection.
2. The method for phase-shifting modulation of an EC-BWPT system under a change in coupling capacitance according to claim 1, wherein the process of adjusting the adjustable delay phase-shifting angle δ between the primary side control signal and the secondary side control signal for phase-shifting tuning control specifically comprises the steps of:
Setting the switching drive frequency f s of the EC-BWPT system, the internal phase angle of the primary side converter using a set of default values And internal phase shift angle/>, of the secondary side converterAn adjustable delay phase angle delta, a preset power P set and a desired power P ref, wherein And delta is selected from the range/> δ∈(0,2π)；
Operating the EC-BWPT system according to the preset power P set and the relative phase angle theta between the primary side resonance voltage and the secondary side resonance voltage corresponding to the transmission direction, which is theta 1, wherein theta 1 is equal to the current adjustable delay phase angle delta 1;
The actual output power P o is obtained by detecting the secondary DC current I o and is compared with the preset power P set, if P o is not equal to P set, the power is kept And/>The adjustable delay phase angle delta is unchanged and adjusted until P o is equal to P set, finally delta is changed from delta 1 to delta 2, and the relative phase angle theta between the primary side resonance voltage and the secondary side resonance voltage is changed from theta 1 to theta 2, so that the EC-BWPT system is in a resonance state;
Relative phase angle θ and phase angle The relationship between the adjustable delay phase angle delta is as follows:
3. The phase shift modulation method of an EC-BWPT system under a change in coupling capacitance as claimed in claim 2, wherein the phase shift angle δ and the internal phase shift angle of the secondary side converter are adjusted The process of bidirectional power flow regulation is specifically as follows:
Maintaining the relative phase angle theta 2 of the output voltages of the primary and secondary side converters constant, and adjusting the internal phase angle of the secondary side converter Until the actual output power P o is equal to the desired output power P ref, finally the internal phase angle/>, of the secondary converter is madeFrom/>To/>Delta changes from delta 2 to delta 3,/>
4. A phase shift modulation method for an EC-BWPT system under a change in coupling capacitance as claimed in claim 3, wherein:
The EC-BWPT system comprises a primary side and a secondary side, wherein the primary side comprises a primary side direct current power supply, a primary side converter, a primary side resonant network and a primary side polar plate which are sequentially connected, and the secondary side comprises a secondary side polar plate, a secondary side resonant network, the secondary side converter and a secondary side direct current power supply which are sequentially connected;
The primary side converter and the secondary side converter are reversible full-bridge converters composed of 4 switching tubes, all the switching tubes of the primary side converter and the secondary side converter work at a duty ratio of 50% and a switching frequency f s, and an internal phase shift angle between two branches of the primary side converter is The internal phase shift angle between two branches of the secondary side converter is/>
5. The phase shift modulation method of the EC-BWPT system under coupling capacitance variation as claimed in claim 4, wherein: by controlling the transmission direction of the theta control power, power is transmitted from the secondary side to the primary side when theta is 0 DEG < 180 DEG, and power is transmitted from the primary side to the secondary side when theta is-180 DEG < 0 deg.
6. The phase shift modulation method of the EC-BWPT system under coupling capacitance variation according to claim 5, wherein: and the primary side resonance network and the secondary side resonance network both adopt LCLC resonance networks.
7. The phase shift modulation system of the EC-BWPT system under the change of coupling capacitance is characterized in that: a phase shift modulation method applied to the EC-BWPT system under the coupling capacitance change as defined in any one of claims 4 to 6, the phase shift modulation system comprising a primary side controller connected to the primary side converter, and a secondary side controller connected to the secondary side converter; the primary side controller is used for generating a primary side driving signal, and the primary side driving signal acts on the primary side converter to enable the internal phase shift angle of the primary side converter to beThe secondary side controller is used for generating a secondary side driving signal, and the secondary side driving signal acts on the secondary side converter, so that the internal phase shift angle of the secondary side driving signal is/>And an adjustable delay phase shift angle between the primary side control signal and the secondary side control signal is delta.
8. The phase shift modulation system of the EC-BWPT system under coupling capacitance variation as claimed in claim 7, wherein: and the secondary side controller adopts a PID control mode to carry out phase-shifting tuning control and bidirectional power flow adjustment.
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