CN116566073A - Self-excitation frequency control method and system of string compensation type WPT system - Google Patents
Self-excitation frequency control method and system of string compensation type WPT system Download PDFInfo
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Classifications
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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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- 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
- H02M3/01—Resonant DC/DC converters
- H02M3/015—Resonant DC/DC converters with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuit
Abstract
The invention relates to the technical field of wireless power transmission, and particularly discloses a self-excitation frequency control method and a self-excitation frequency control system of a string compensation type WPT system. The invention realizes the control of free switching of the self-excitation frequency of the string compensation WPT system, is not influenced by the initial state of the system, has convenient operation and simple control, improves the electric energy transmission characteristic, ensures that the system outputs more stably under the condition of variable coupling coefficient, works in weak susceptibility, and can obviously improve the system offset adaptability compared with the existing single-resonance frequency system design method.
Description
Technical Field
The invention relates to the technical field of wireless power transmission, in particular to a self-excitation frequency control method and system of a string compensation type WPT system.
Background
With the recent technological accumulation, wireless power transmission technology is becoming mature, and research results in laboratories are gradually going to industrialization. Many high and new technology products such as new energy automobiles, human body implantable devices, unmanned aerial vehicle intelligent devices and the like already adopt a wireless electric energy transmission technology. Wireless power transmission technology has brought many convenience to people's daily lives, but there are still some problems in use. Because of the loose coupling of the primary side and the secondary side of the wireless power transmission system, in order to improve the power transmission capability of the wireless power transmission system, a resonant switching circuit is generally adopted by the primary circuit and the secondary circuit of the system, which leads to high-order nonlinear characteristics of the system, so that the dynamic behavior of the system is very complex, and the phenomenon of self-excitation frequency point jump of the wireless power transmission system under certain special conditions is caused.
To solve the above problems, various academic papers and patents have been studied and corresponding solutions have been proposed. Tang Chunsen in the doctor's study on the working point of the soft switch of the non-contact electric energy transmission system and application, a power control thought based on multiple resonance points of the system is provided, and the core thought is to make the system switch back and forth among multiple resonance points according to error feedback information, so as to realize the control of power. The control method has simple structure and higher conversion efficiency, but the output current has ripple waves, and is not suitable for places with higher requirements on the quality of voltage waveforms. Tan Jian in the published patent of electric energy and signal synchronous transmission method based on frequency division in electric energy wireless transmission, the aim of signal frequency modulation transmission is achieved by switching between two resonant autonomous stable frequencies through a current zero-crossing detection method. The zero-crossing detection method is beneficial to reliable transmission of signals, but has certain defects, is greatly influenced by initial values of the system, and different initial values of the system can influence the selection of resonant frequency.
Disclosure of Invention
The invention provides a self-excitation frequency control method of a string compensation type WPT system, which solves the technical problems that: in the free switching of the self-excitation frequency of the string compensation type WPT system, the current zero-crossing detection method is greatly influenced by the selection of the initial value of the system.
In order to solve the technical problems, the invention provides a self-excitation frequency control method of a string compensation type WPT system, which comprises the following steps:
s1, detecting a coupling coefficient of a string compensation type WPT system, and acquiring the working state of the string compensation type WPT system according to the coupling coefficient;
s2, judging whether the working state of the string compensation type WPT system is single-mode or multi-mode, if so, entering a step S3, and if so, returning to the step S1;
s3, detecting primary side current i of the string compensation type WPT system 1 And inverter output voltage v 1 Generating i 1 /v 1 According to the amplitude-frequency phase curve, determining a first resonance frequency point and a second resonance frequency point from low to high;
s4, judging whether the difference between the amplitude of the first resonance frequency point and the amplitude of the second resonance frequency point is larger than a preset value, if so, executing the steps S5 and S6, and if not, executing the step S7;
s5, according to i 1 /v 1 Setting a first threshold value of a first resonance frequency point and a second threshold value of a second resonance frequency point according to a phase curve in the amplitude-frequency phase curve;
s6, taking the first threshold value or the second threshold value as a threshold value for primary side current detection, and controlling a primary side inverter circuit of the string compensation type WPT system to enable the resonant frequency of the system to be stabilized at the first resonant frequency point or the second resonant frequency point;
and S7, setting a threshold value of primary side current detection to be 0, and adjusting the effective value of a primary side resonance capacitor or a secondary side resonance capacitor of the series-series compensation type WPT system to control the resonance frequency of the system to be stabilized at a third resonance frequency point or a fourth resonance frequency point.
Further, in the step S5, the first threshold is set to be a sine value of a maximum point phase angle of the phase curve in the amplitude-frequency phase curve, and the second threshold is set to be a sine value of a minimum point phase angle of the phase curve in the amplitude-frequency phase curve.
Further, in the step S7, when the effective value of the secondary resonant tank capacitor is adjusted to be a times of the initial capacitance value, the resonant frequency of the control system is stabilized at a third resonant frequency point, a < 1, where the third resonant frequency point is i after the effective value of the secondary resonant tank capacitor is adjusted 1 //v 1 The amplitude of the resonance frequency point with larger amplitude in the amplitude-frequency phase curve.
Further, in the step S7, when the effective value of the secondary resonant tank capacitor is adjusted to be B times of the initial capacitance value, the resonant frequency of the control system is stabilized at a fourth resonant frequency point, B > 1, which is i after the effective value of the secondary resonant tank capacitor is adjusted 1 //v 1 The amplitude of the resonance frequency point with larger amplitude in the amplitude-frequency phase curve.
Further, in the step S1, the coupling coefficients between the coupling mechanisms are estimated in real time by sampling the current of the transmitting end and the dc input voltage and calculating the effective values thereof, and combining other known parameters of the system and derivation formulas of the coupling coefficients.
Further, after the step S7, the method further includes the steps of:
s8, judging whether the working state of the string compensation type WPT system is changed, if not, continuously charging until charging is completed, and if so, returning to the step S1.
The invention also provides a self-excitation frequency control system of the string compensation type WPT system, which is characterized in that: the system comprises a primary side current and voltage acquisition module and a primary side controller;
the primary side current and voltage acquisition module is used for acquiring primary side current i of the string compensation type WPT system 1 And inverter output voltage v 1 And sending to the primary side controller;
the primary side controller is used for executing steps S1-S8 in the method.
According to the self-excitation frequency control method and system for the string compensation type WPT system, the current working state of the system is obtained through detecting the coupling coefficient, the electric energy transmission characteristic is used as an optimization target, the system is in a detuned state through setting the threshold value or adjusting the resonance capacitance value, so that the ideal self-excitation oscillation frequency is switched, and when the position of the coupling mechanism is determined, namely the working state of the system is not changed any more, the charging is continued until the charging is completed. The invention realizes the free switching of the self-excitation frequency of the string compensation WPT system, is not influenced by the initial state of the system, has convenient operation and simple control, ensures that the system can stably output under the condition of variable coupling coefficient and simultaneously works in weak susceptibility, and can obviously improve the adaptability of the system to offset compared with the existing single-resonance frequency system control method.
Drawings
Fig. 1 is a circuit configuration diagram of a string compensation WPT system according to an embodiment of the present invention;
FIG. 2 is an equivalent circuit diagram of FIG. 1 provided by an embodiment of the present invention;
FIG. 3 is an equivalent circuit diagram of FIG. 2 provided by an embodiment of the present invention;
fig. 4 (a) is a system amplitude-frequency phase diagram corresponding to the mutual inductance m=10μh provided in the embodiment of the present invention;
fig. 4 (b) is a corresponding system amplitude-frequency phase diagram when the mutual inductance m=40μh provided in the embodiment of the present invention;
fig. 5 is a flowchart of a self-excitation frequency control method of a string compensation WPT system provided by an embodiment of the present invention;
FIG. 6 is a diagram of the verification result of the first method when the initial value provided by the embodiment of the invention is an arbitrary value;
FIG. 7 (a) is a diagram of a C provided by an embodiment of the present invention 2 ＝C s A corresponding amplitude-frequency phase graph;
FIG. 7 (b) is a diagram of a C provided by an embodiment of the present invention 2 ＝C s A corresponding system autonomous stable frequency diagram;
FIG. 8 (a) is a diagram of a C provided by an embodiment of the present invention 2 ＝0.8*C s A corresponding amplitude-frequency phase graph;
FIG. 8 (b) is an embodiment of the present inventionC provided 2 ＝0.8*C s A corresponding system autonomous stable frequency diagram;
FIG. 9 (a) is a diagram of a C provided by an embodiment of the present invention 2 ＝1.2*C s A corresponding amplitude-frequency phase graph;
FIG. 9 (b) is a diagram of a C provided by an embodiment of the present invention 2 ＝1.2*C s And a corresponding system autonomous stable frequency diagram.
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.
Fig. 1 is a schematic diagram of a serial-serial compensation WPT system, which is abbreviated as serial compensation WPT system, and as can be seen from fig. 1, the serial compensation WPT system comprises a transmitting end and a receiving end, the transmitting end comprises a direct current power supply, a high frequency inverter and a primary serial compensation capacitor C which are sequentially connected 1 Transmitting coil L 1 The receiving end comprises receiving coils L which are connected in sequence 2 Compensation capacitor C with secondary side connected in series 2 Rectifying and filtering circuit (consisting of rectifier and filter capacitor C f Composition, load resistance R o Corresponding current voltages are also indicated in the corresponding positions in fig. 1, including the inverter input current I dc Inverter output voltage v 1 Primary current i 1 Secondary side current i 2 Rectifier input voltage v 2 Rectifier output current I r System output current I o System output voltage V o 。
For the series-series compensation WPT system shown in fig. 1, due to the high-order nonlinear characteristic of the system itself, multiple resonance operation points may exist at the same time when multiple soft switch operation points exist in the system. The direct current voltage source and the inverter module are replaced by square wave voltage sources, the coupling effect is replaced by two controlled voltage sources, the rectifier bridge is replaced by a square wave source and a direct current source, the equivalent of figure 1 is figure 2,wherein R is 1 And R is 2 Representing the equivalent resistances of the primary and secondary sides, respectively, and M represents the mutual inductance between the transmit and receive coils. Modeling of WPT systems is based on equivalent circuit analysis as shown in fig. 2. To facilitate analysis of system behavior, mapping load resistance to the resistance of the secondary loop is equivalent to R eq Equivalent resistance R eq The approximation is:
the equivalent circuit of fig. 2 is further simplified to fig. 3 according to the equivalent resistance of the load.
The behavior of the equivalent circuit shown in fig. 3 can be described by the following equation according to kirchhoff's law:
ω represents the operating angular frequency of the system.
Will be i in the above formula 2 After the offset, the primary current i is further obtained 1 And inverter output voltage v 1 Ratio G between:
wherein z is 1 Representing primary impedance, z 2 Representing the secondary impedance. z 1 、z 2 The concrete steps are as follows:
in the embodiment, the dynamic behavior of the system is studied mainly according to the relation between the amplitude phase of G and the switching frequency. Simulation experiments show that the number of resonant frequency points of the system is not the only one any more along with the increase of the coupling coefficient. Fig. 4 (a) is a system amplitude-frequency phase graph corresponding to the mutual inductance m=10μh, fig. 4 (b) is a system amplitude-frequency phase graph corresponding to the mutual inductance m=40μh, and it can be seen from comparing fig. 4 (a) and fig. 4 (b) that when the coupling coefficient is large to a certain extent, the number of resonance points of the system becomes 2. As can be seen from fig. 4 (b), the two resonance frequency points are 169.20kHz and 256.34kHz, respectively. If the system amplitudes corresponding to the two resonance frequency points are not much different and can exist stably in the floating frequency mode, the problem that the switching element cannot be switched freely between the two resonance frequencies exists. Multiple resonant frequencies of a multi-resonant system structure are matched to each other to obtain a wide variety of transmission characteristics, as compared with a system having only one resonant frequency.
How to freely switch the autonomous stable frequency of the system without being influenced by the initial value of the system is an important problem to be solved by the invention. In order to solve the problem, this embodiment proposes a self-excitation frequency control method for a string compensation WPT system, as shown in fig. 5, specifically including the steps of:
s1, detecting a coupling coefficient of a string compensation type WPT system, and acquiring the working state of the string compensation type WPT system according to the coupling coefficient;
s2, judging whether the working state of the string compensation type WPT system is single-mode or multi-mode, if so, entering a step S3, and if so, returning to the step S1;
s3, detecting primary side current i of string compensation type WPT system 1 And inverter output voltage v 1 Generating i 1 /v 1 According to the amplitude-frequency phase curve, determining a first resonance frequency point and a second resonance frequency point from low to high;
s4, judging whether the difference between the amplitude of the first resonance frequency point and the amplitude of the second resonance frequency point is larger than a preset value, if so, executing the steps S5 and S6, and if not, executing the step S7;
s5, according to i 1 /v 1 Setting a first threshold and a second threshold for a phase curve in the amplitude-frequency phase curve;
s6, using a first threshold value or a second threshold value as a threshold value for primary side current detection, and controlling a primary side inverter circuit of the string compensation type WPT system to enable the resonant frequency of the system to be stabilized at a first resonant frequency point or a second resonant frequency point;
s7, setting a threshold value of primary side current detection as 0, and adjusting an effective value of a primary side resonance capacitor or a secondary side resonance capacitor of the series compensation type WPT system to control the resonance frequency of the system to be stabilized at a third resonance frequency point or a fourth resonance frequency point;
s8, judging whether the working state of the string compensation type WPT system is changed, if not, continuing to charge until the charging is completed, and if so, returning to the step S1.
For step S4, when the amplitude of the first resonant frequency point and the amplitude of the second resonant frequency point have a relatively large phase difference, frequency switching can be achieved by changing the threshold value of current detection (the first method), where the threshold value refers to the ratio of the current value at the switching point to the current peak value, that is, the phase angle sine values of the two resonant frequency points, and other parameters remain unchanged, and the system is controlled to switch from the multimode region to the single-mode region by selecting the threshold value, so that the problem of jump of the self-excited frequency is solved. Compared with the current zero-crossing detection method, the method has the advantages that the threshold value of current detection is changed, the autonomous stable frequency of the system is not switched when the current crosses zero, but is switched at the set threshold value, so that the phase angle is changed from multiple modes (one to many) to single modes (one to one), the autonomous stable frequency of the system can be freely switched, and the influence of the initial value x of the system is avoided.
The threshold is determined from the phase curve of the system, as shown in fig. 4 (b), with three points of intersection of the phase curve with the zero axis, where the corresponding point at the intermediate frequency is unstable, considering only the other two stable resonance points. The phase positions corresponding to the two extreme points appear in the curve, namely the boundary between single mode and multi-mode, and the magnitude of the threshold critical value can be converted and determined through the phase angle sine values of the two extreme points. It should be noted that, the setting of the threshold takes into account that the free switching of the self-excitation frequency is not affected by the initial value of the system, so as to further improve the transmission characteristic of the wireless power transmission system, so that the threshold is preferably selected to be close to or equal to the threshold, and the threshold is directly selected as the threshold of current detection in this embodiment. By calculation, the threshold values corresponding to the two resonance frequency points 169.20kHz and 256.34kHz shown in FIG. 4 (b) are +0.4 and-0.26 respectively.
For the WPT system shown in fig. 1, when the threshold is set to zero and the initial state of the system is not zero, the autonomous frequency cannot be switched freely, and at this time, the autonomous frequency can be switched freely without being affected by the initial state of the system by setting a suitable threshold σ, so as to verify the effectiveness of the proposed method, the verification result is shown in fig. 6, the waveform with a lower amplitude in the middle part represents the primary side current, and the waveform with a higher amplitude represents the inverter output voltage. As can be seen from fig. 6, when the threshold value σ (tol) = 0 (the initial state of the system is not zero), the autonomous frequency cannot be switched freely, the autonomous stable frequency of the system is 246.61kHz, when the threshold value σ (tol) = +0.4, the autonomous stable frequency of the system is 169.20.40kHz, which is the first resonant frequency point in fig. 4 (b), and when the threshold value σ= -0.26, the autonomous stable frequency of the system is 256.34kHz, which is the second resonant frequency point in fig. 4 (b), which verifies the effectiveness of the first method proposed by the present embodiment.
When the amplitude of the first resonance frequency point is smaller than the amplitude of the second resonance frequency point, a second method is adopted. The second method is primary side or secondary side detuning control, because when the system amplitude values corresponding to two resonance points are not much different, the problem that the system cannot be freely switched between two autonomous stable frequencies of resonance exists, at the moment, the effective capacitance value or inductance value can be adjusted in the primary side or secondary side resonance loop, so that the system is in a detuned state, the amplitude value of one resonance frequency can be weakened in the detuned state, compared with the amplitude value of the other resonance frequency, the autonomous stable frequency of the system can be freely switched according to specific requirements, and the influence of the initial value of the system is avoided. For the string-string compensation WPT system, the secondary side resonant circuit capacitor C is adjusted 2 The value (set to its original value as C s ) The switching of the autonomous stable frequency of the system can be freely controlled and is not influenced by the initial value of the system.
In step S7, when the effective value of the secondary resonant tank capacitor is adjusted to be A times the initial capacitance value, the control systemThe resonance frequency is stabilized at a third resonance frequency point, A is less than 1, and the third resonance frequency point is i after the effective value of the secondary side resonance circuit capacitance is adjusted 1 /v 1 The amplitude of the resonance frequency point with larger amplitude in the amplitude-frequency phase curve. When the effective value of the secondary side resonant circuit capacitor is adjusted to be B times of the initial capacitance value, the resonant frequency of the control system is stabilized at a fourth resonant frequency point, B is more than 1, and the fourth resonant frequency point is i after the effective value of the secondary side resonant circuit capacitor is adjusted 1 /v 1 The amplitude of the resonance frequency point with larger amplitude in the amplitude-frequency phase curve. A. The value of B needs to make the amplitude of the two resonance point frequencies in the amplitude-frequency phase curve after the capacitance value is adjusted have larger amplitude difference.
When the system initial value is an arbitrary value, the verification result is as shown in fig. 7 (a), 7 (b), 8 (a), 8 (b), 9 (a), and 9 (b). FIGS. 7 (a) and 7 (b) are C respectively 2 ＝C s Corresponding amplitude-frequency phase diagram and corresponding system autonomous stable frequency diagram, fig. 8 (a) and 8 (b) are respectively C 2 ＝0.8*C s (i.e., a=0.8) corresponding amplitude-frequency phase diagram and corresponding system autonomous stable frequency diagram, fig. 9 (a) and 9 (b) are C respectively 2 ＝1.2*C s (i.e., b=1.2) a corresponding amplitude-frequency phase plot and a corresponding system autonomous stable frequency plot. As can be seen from fig. 7 (a) and 7 (b), when the threshold tol is uniformly set to 0, there are two resonance frequency points of the system, but the system cannot perform frequency switching, so that the autonomous stable frequency of the system is stabilized at 246.60kHz. As can be seen from fig. 8 (a) and 8 (b), when the secondary resonance capacitance is reduced by 0.8 times the initial capacitance value, two resonance frequency points of the system are changed, and at this time, there is a resonance frequency point (179.61 kHz) with a significantly larger amplitude, and the resonance frequency point is taken as a third resonance frequency point, and the system is switched to the third resonance frequency point (system autonomous stable frequency). As can be seen from fig. 9 (a) and 9 (b), when the secondary resonance capacitance is increased to 1.2 times the initial capacitance value, two resonance frequency points of the system are changed, and at this time, there is a resonance frequency point (239.79 kHz) with a significantly larger amplitude, and the resonance frequency point is taken as a fourth resonance frequency point, so that the system is switched to the fourth resonance frequency point (system autonomous stable frequency). While the systemWhen switching is started, the system is unstable, and the resonance frequency of the system can be seen to slightly come in and go out from the corresponding third resonance frequency point and fourth resonance frequency point.
Comparing 7 (a), 7 (b), 8 (a), 8 (b), 9 (a) and 9 (b), when the threshold tol is uniformly set to 0, the effective value of the secondary side resonant circuit capacitor is changed and adjusted, so that the switching of the autonomous stable frequency of the system can be freely controlled, the switching is not influenced by the initial value of the system, and the effectiveness of the second method provided by the embodiment is verified.
The embodiment of the invention can be applied to the scenes that the positions of receiving ends of unmanned aerial vehicle wireless charging, underwater robot UUV wireless charging and the like are not fixed with changes. For an unmanned aerial vehicle or an underwater robot wireless charging system, a transmitting end and a receiving end cannot be aligned completely in general, and a coupling mechanism often has non-optimal working states such as offset, and the different working states directly determine the power transmission capacity and the transmission efficiency of the current system. Under the condition of large coupling mechanism offset range, free switching of self-excitation frequency is particularly important, and compared with the existing single-resonance frequency system design method, the system offset adaptability can be remarkably improved.
When the multi-resonance system operates normally, the current working state of the system is obtained by detecting the coupling coefficient. In the actual working condition, the offset between the coils of the transmitting end and the receiving end is difficult to directly measure, so that the direct measurement of the coupling coefficient is troublesome. And taking the electric energy transmission characteristic as an optimization target, setting a threshold value by the singlechip or enabling the system to be in a detuned state, so that the system is switched to an ideal proper self-oscillation frequency, and continuously charging until the charging is completed when the position of the coupling mechanism is determined, namely the working state of the system is not changed any more.
Corresponding to the system, the invention also provides a self-excitation frequency control system of the string compensation type WPT system, which comprises a primary side current and voltage acquisition module and a primary side controller;
the primary side current and voltage acquisition module is used for acquiring primary side current i of the string compensation type WPT system 1 And inverter output voltage v 1 And send to the primary side controller;
the primary side controller is configured to perform steps S1 to S8 in the above method.
In summary, the self-excitation frequency control method and system for the string compensation type WPT system provided by the embodiment of the invention acquire the current working state of the system by detecting the coupling coefficient, then take the electric energy transmission characteristic as an optimization target, and switch to the ideal self-excitation oscillation frequency by setting a threshold value or adjusting the resonance capacitance value to enable the system to be in a detuned state, and continuously charge until the charging is completed when the position of the coupling mechanism is determined, namely the working state of the system is not changed any more. The embodiment of the invention realizes the free switching of the self-excitation frequency of the string compensation WPT system, is not influenced by the initial state of the system, is convenient to operate and simple to control, ensures that the system can stably output under the condition of variable coupling coefficient and simultaneously works in weak susceptibility, and can obviously improve the system offset adaptability compared with the existing single-resonance frequency system control method.
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. A self-excitation frequency control method of a string compensation type WPT system is characterized by comprising the following steps:
s1, detecting a coupling coefficient of a string compensation type WPT system, and acquiring the working state of the string compensation type WPT system according to the coupling coefficient;
s2, judging whether the working state of the string compensation type WPT system is single-mode or multi-mode, if so, entering a step S3, and if so, returning to the step S1;
s3, detecting stationPrimary side current i of string compensation type WPT system 1 And inverter output voltage v 1 Generating i 1 /v 1 According to the amplitude-frequency phase curve, determining a first resonance frequency point and a second resonance frequency point from low to high;
s4, judging whether the difference between the amplitude of the first resonance frequency point and the amplitude of the second resonance frequency point is larger than a preset value, if so, executing the steps S5 and S6, and if not, executing the step S7;
s5, according to i 1 /v 1 Setting a first threshold value of a first resonance frequency point and a second threshold value of a second resonance frequency point according to a phase curve in the amplitude-frequency phase curve;
s6, taking the first threshold value or the second threshold value as a threshold value for primary side current detection, and controlling a primary side inverter circuit of the string compensation type WPT system to enable the resonant frequency of the system to be stabilized at the first resonant frequency point or the second resonant frequency point;
and S7, setting a threshold value of primary side current detection to be 0, and adjusting the effective value of a primary side resonance capacitor or a secondary side resonance capacitor of the series-series compensation type WPT system to control the resonance frequency of the system to be stabilized at a third resonance frequency point or a fourth resonance frequency point.
2. The self-excitation frequency control method of a string compensation type WPT system according to claim 1, characterized by: in the step S5, the first threshold is set to be a sine value of a maximum point phase angle of the phase curve in the amplitude-frequency phase curve, and the second threshold is set to be a sine value of a minimum point phase angle of the phase curve in the amplitude-frequency phase curve.
3. The self-excitation frequency control method of a string compensation type WPT system according to claim 2, characterized by: in the step S7, when the effective value of the secondary side resonant tank capacitor is adjusted to be A times of the initial capacitance value, the resonant frequency of the control system is stabilized at a third resonant frequency point, A < 1, which is the adjusted secondary sideI after the effective value of the resonant circuit capacitance 1 //v 1 The amplitude of the resonance frequency point with larger amplitude in the amplitude-frequency phase curve.
4. The self-excitation frequency control method of a string compensation type WPT system according to claim 1, characterized by: in the step S7, when the effective value of the secondary resonant tank capacitor is adjusted to be B times the initial capacitance value, the resonant frequency of the control system is stabilized at a fourth resonant frequency point, B > 1, which is i after the effective value of the secondary resonant tank capacitor is adjusted 1 //v 1 The amplitude of the resonance frequency point with larger amplitude in the amplitude-frequency phase curve.
5. The self-excitation frequency control method of a string compensation type WPT system according to claim 1, characterized by: in the step S1, the coupling coefficients between the coupling mechanisms are estimated in real time by sampling the current of the transmitting end and the dc input voltage and calculating the effective values thereof, and combining other known parameters of the system and derivation formulas of the coupling coefficients.
6. The method for controlling the self-excitation frequency of a string compensation type WPT system according to claim 1, further comprising the step of, after said step S7:
s8, judging whether the working state of the string compensation type WPT system is changed, if not, continuously charging until charging is completed, and if so, returning to the step S1.
7. A self-excitation frequency control system of a string compensation WPT system is characterized in that: the system comprises a primary side current and voltage acquisition module and a primary side controller;
the primary side current and voltage acquisition module is used for acquiring primary side current i of the string compensation type WPT system 1 And inverter output voltage v 1 And sending to the primary side controller;
the primary side controller is configured to perform steps S1 to S7 as claimed in any one of claims 1 to 6.
8. A self-excitation frequency control system of a string compensation type WPT system as claimed in claim 7, wherein: the primary side controller is further configured to perform step S8 of claim 6.
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| CN116885860A (en) * | 2023-09-06 | 2023-10-13 | 哈尔滨理工大学 | Control method of underwater wireless charging system |
| CN116885860B (en) * | 2023-09-06 | 2023-12-29 | 哈尔滨理工大学 | Control method of underwater wireless charging system |
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