Primary side control method and device of SS-WPT system without secondary side communication
Patent Information
- Application Number
- CN202611203119.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-10
- Publication Date
- 2026-10-30
Smart Images
Figure CN123019266A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wireless power transmission technology, and in particular to a primary-side control method and apparatus for an SS-WPT system that does not require secondary-side communication. Background Technology
[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.
[0003] In AGV wireless charging systems, the SS compensation topology (primary-side series-secondary-side series) is widely used. The primary-side transmitter is buried in the ground at the charging position, and the secondary-side receiver is installed on the AGV chassis. Wireless power transmission is achieved through magnetic coupling between the primary and secondary coils. Since the AGV is not always docked at the charging position, the primary side needs to autonomously determine whether the receiver is in place. In practical engineering applications, the inductance of the primary coil and the compensation capacitor deviate from their design values due to temperature changes, component aging, and manufacturing tolerances, causing the primary-side resonant frequency to drift and affecting the accuracy of the system's operating point. Similarly, the secondary-side coil inductance and the compensation capacitor also suffer from the same drift problem. When the actual resonant frequency of the secondary side deviates from the resonant frequency of the primary side, detuning occurs. If this is not detected, it will lead to significant deviations in subsequent parameter estimation and control.
[0004] Furthermore, the mutual inductance between the primary and secondary sides changes with the AGV's docking position, directly affecting the relationship between the receiver's output current and the transmitter's voltage, requiring precise estimation under actual operating conditions. However, this system faces strict constraints: the controller can only contact the primary circuit and cannot obtain information such as secondary voltage, current, and temperature; it is not allowed to establish a secondary communication link via radio frequency or infrared, nor can it utilize additional instruments such as frequency sweep meters, LCR meters, or impedance analyzers; the available hardware is limited to H-bridge inverters controlled by MCUs or DSPs, primary current sensors, and ADC sampling modules. Under these constraints, existing methods have many shortcomings. Frequency sweeping methods require traversing frequency points, which is time-consuming and results in excessive current at resonant points, posing safety hazards. Feedback schemes relying on secondary communication require additional communication links, increasing system cost and failure rate. Auxiliary coil detection methods require additional hardware and installation space, making them unsuitable for compact applications. Inverter frequency scanning methods typically require obtaining phase difference information between voltage and current, increasing signal processing complexity. Design schemes based on the assumption of symmetry between primary and secondary side parameters are difficult to implement in practice. Manufacturing tolerances and aging can cause the inductance and capacitance parameters of the primary and secondary sides to be unequal, introducing systematic errors into the symmetry assumption. In addition, existing technologies generally ignore secondary side detuning and fail to consider the resonant frequency shift caused by secondary capacitor aging and temperature drift, resulting in serious deviations in parameter estimation under detuned conditions. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a primary-side control method and apparatus for an SS-WPT system that eliminates the need for secondary-side communication. By injecting square wave voltages of different fundamental frequencies into the primary-side resonant circuit, the current amplitudes of multiple odd harmonics are extracted to achieve analytical solutions for the primary-side inductance and compensation capacitor. Harmonic consistency verification determines the receiver's presence. Based on an asymmetric input impedance model, the measured impedance amplitudes of multiple harmonics are fitted to jointly estimate the coupling coefficient, total secondary-side resistance, and secondary-side detuning factor. Precise control of the receiver's output current is achieved by fixing the primary-side resonant frequency and adjusting only the DC bus voltage using a feedforward control law. This invention solves the problem of achieving precise charging current control by independently performing parameter identification, presence detection, joint estimation of mutual inductance and secondary-side detuning, and without relying on secondary-side communication or phase information, all from the primary side.
[0006] On the one hand, a primary-side control method for an SS-WPT system without secondary-side communication is provided, including: A first square wave voltage with a first fundamental frequency is injected into the primary resonant circuit. The primary current is collected and the current amplitudes of at least three odd harmonics are extracted. The measured impedance amplitudes of each harmonic are calculated. The primary inductance and primary compensation capacitor are solved using the measured impedance amplitudes of the first group of harmonics among the at least three odd harmonics. The primary-side inductor and primary-side compensation capacitor are verified for consistency using the measured impedance amplitude of the second group of harmonics among the at least three odd harmonics, in order to determine whether the receiving end is in place. Once the receiver is determined to be in place, the DC bus voltage is reduced and a second square wave voltage with a second fundamental frequency is injected. The primary current is collected again and the current amplitudes of at least three odd harmonics are extracted. The corresponding measured impedance amplitudes are calculated, and the measured impedance amplitudes are fitted based on the asymmetric input impedance model. The coupling coefficient, the total resistance of the secondary side, and the detuning factor of the secondary side are jointly estimated. The DC bus voltage is restored and the output frequency is switched to the actual resonant frequency of the primary side and kept unchanged. Only the DC bus voltage is adjusted. The output current of the receiving end is controlled according to the feedforward control law based on the primary side inductance, primary side compensation capacitor, coupling coefficient, secondary side total resistance and secondary side detuning factor.
[0007] Furthermore, the first group of harmonics consists of the 1st and 3rd harmonics, and the second group of harmonics consists of the 5th harmonic.
[0008] Furthermore, the fundamental frequency of the first square wave voltage is set such that at least three odd harmonic frequencies are lower than the primary resonant frequency.
[0009] Furthermore, the second fundamental frequency satisfies This makes the third harmonic frequency equal to the actual resonant frequency of the primary side, where, The primary resonant frequency, It is the fundamental frequency of the square wave.
[0010] Furthermore, the consistency verification includes: determining the receiver's position by using the error between the measured impedance amplitude and the predicted impedance amplitude of the second set of harmonics; when the error exceeds a preset first threshold, the receiver is determined to be in place; the predicted impedance amplitude is determined by A5_pred=(9A3). The value is calculated as 2A1) / 5, where A1 and A3 are the measured impedance amplitudes of the 1st and 3rd harmonics in the first group of harmonics, respectively.
[0011] Furthermore, the consistency verification also includes: when the primary-side inductor or the primary-side compensation capacitor deviates from the reference value by more than a preset second threshold, it is determined that the receiver is in place.
[0012] Furthermore, the measured impedance amplitude is fitted based on the asymmetric input impedance model, and the coupling coefficient, total secondary resistance, and secondary detuning factor are jointly estimated, specifically as follows: With the primary inductor Primary-side compensation capacitor Primary resistance Secondary inductor and nominal value of secondary capacitor Given a known quantity, with coupling coefficient Total resistance of the secondary side and secondary side detuning factor For the parameters to be estimated, construct an asymmetric input impedance model: ; in, , , , , ; Using the measured impedance amplitude at three harmonic frequencies as the target, the parameters to be estimated are fitted to minimize the sum of squared errors between the impedance amplitude output by the model and the measured impedance amplitude, thereby obtaining the coupling coefficient, the total resistance of the secondary side, and the detuning factor of the secondary side.
[0013] Furthermore, the DC bus voltage is restored and the output frequency is switched to and kept constant at the primary side's actual resonant frequency. Only the DC bus voltage is adjusted. Based on the primary side inductance, primary side compensation capacitor, coupling coefficient, secondary side total resistance, and secondary side detuning factor, the receiver output current is controlled according to the feedforward control law, specifically: The output frequency is the actual resonant frequency of the primary side. Under the given conditions, the secondary reactance is: ; The primary input impedance amplitude is: ; Based on the target output current The required DC bus voltage is calculated according to the following feedforward control law: ; The output current of the receiving end is controlled by the DC bus voltage.
[0014] Furthermore, during the charging process, power transmission is periodically paused and the joint estimation is performed again to update the coupling coefficient, secondary side total resistance, and secondary side detuning factor, and the feedforward control law is refreshed according to the updated parameters.
[0015] On the other hand, a primary-side control device for an SS-WPT system that does not require secondary-side communication is provided, comprising: H-bridge inverter, used to output square wave voltage to the primary resonant circuit; A current sensor is used to collect the primary current. The ADC module is used to sample the DC bus voltage and the primary current. The controller, which is connected to the H-bridge inverter, the current sensor and the ADC module respectively, is configured to perform the method as described in the first aspect.
[0016] The above technical solution has the following advantages or beneficial effects: (1) Without adding any hardware, this invention reuses the existing H-bridge inverter and current sensor on the primary side and utilizes the characteristic that square wave voltage naturally contains odd harmonics to simultaneously acquire impedance information at multiple frequency points with a single excitation. This enables analytical identification of primary side LC parameters, receiver presence detection, and joint estimation of mutual inductance, secondary side total resistance, and secondary side detuning factor. It eliminates the dependence on secondary side communication links and additional auxiliary coils, reducing system cost and failure rate. At the same time, this invention only needs to acquire the primary side current amplitude and does not need to acquire voltage-current phase difference information, avoiding complex phase detection links and reducing the requirements for ADC sampling and signal processing. This allows it to run in real time on a low-cost MCU or DSP platform. The LC identification link is solved directly using analytical formulas, and the parameter estimation link is implemented using an offline three-dimensional lookup table combined with trilinear interpolation, resulting in extremely low computational complexity.
[0017] (2) The present invention adopts an asymmetric input impedance model, which does not require the primary and secondary side parameters to be equal. The differences in primary and secondary side parameters caused by actual manufacturing tolerances and aging are naturally included in the model, eliminating the systematic error caused by the traditional symmetric assumption. Furthermore, the secondary side detuning factor is included as an independent parameter in the joint estimation, which can effectively identify the resonant frequency shift of the secondary side capacitor caused by aging and temperature drift. Under detuning conditions, the accuracy of mutual inductance estimation and charging control can still be maintained.
[0018] (3) This invention establishes a closed-loop architecture covering the entire lifecycle from standby detection to charging control. During charging, the inverter output frequency is fixed at the actual resonant frequency of the primary side, and the output current of the receiving end is controlled only by adjusting the DC bus voltage, resulting in minimal reactive power and the highest system efficiency. At the same time, it supports periodically pausing power transmission and re-executing parameter estimation during charging, tracking the changes in mutual inductance, secondary total resistance, and secondary detuning factor in real time, and refreshing the feedforward control law to ensure control accuracy under all operating conditions. Attached Figure Description
[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0020] Figure 1 This is a circuit topology diagram of the SS-compensated WPT system in Embodiment 1 of the present invention; Figure 2 This is a flowchart of the method in Embodiment 1 of the present invention. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. Those skilled in the art should understand that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.
[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0023] Example 1 This embodiment provides a primary-side control method for an SS-WPT system that does not require secondary-side communication, such as... Figure 1 As shown, this embodiment is applicable to wireless power transfer systems with SS (Series-Series, primary-secondary series) compensation, where the primary and secondary parameters are independent and symmetry is not required. The primary side is supplied by the DC bus voltage. The power supply generates a high-frequency AC voltage via an H-bridge inverter, which is then applied to the inductor of the primary winding. Primary-side compensation capacitor and primary equivalent series resistance The circuit is a series resonant circuit; the secondary side consists of the secondary coil inductance.
[0024] capacitance and secondary equivalent series resistance The series resonant circuit is formed and a full-bridge rectifier is used as the load. Power is supplied via magnetic coupling between the primary and secondary sides through a mutual inductance M. The controller can only access the primary circuit, and the only measurable quantity is the DC bus voltage. and the instantaneous value of the primary current It is impossible to obtain any electrical information from the secondary side.
[0025] In this system architecture, the primary and secondary resonant frequencies are defined independently. Primary resonant angular frequency. And the corresponding frequencies are:
[0026] The secondary resonant angular frequency and its corresponding frequency are:
[0027] System design timeline This ensures that the resonant frequencies on both sides are consistent, which is a prerequisite for efficient power transmission with SS compensation.
[0028] However, in actual engineering, manufacturing tolerances, temperature drift, and capacitor aging will lead to... and The values deviate from the design values, and the two may no longer be equal. This is because the measurable quantities on the primary side are only those identified during the IDLE period. Based on this, the actual primary-side resonant frequency can be calculated. All frequency normalizations described below in this invention are based on Rather than the design value.
[0029] To quantify the degree of deviation of the secondary resonant frequency from the primary resonant frequency, a secondary detuning factor is defined. This is the ratio of the actual resonant frequency of the secondary side to the actual resonant frequency of the primary side.
[0030] when When the resonant frequencies of the secondary and primary sides are the same, it is called resonant alignment. when At this time, the secondary resonant frequency is too high, corresponding to the secondary compensation capacitor. Too small, secondary edge is on the original edge It is tolerant; when At that time, the secondary resonant frequency is too low, corresponding to Too large, secondary side is on the original side It is sensual; when When this occurs, it indicates that the secondary side is detuned. If detuning is ignored (assuming...) ), will lead to The estimation and feedforward control law produce a deviation, therefore Must with , Estimate them together.
[0031] To facilitate the description of the frequency positions of each harmonic relative to the primary resonant point under square wave excitation, parameters are defined. The calculation method is as follows:
[0032] in, The primary resonant frequency, This is the fundamental frequency of the square wave (set by the MCU). Square wave number... Second-rate( The harmonic frequencies of odd harmonics . The frequency positions of each harmonic of the square wave relative to the resonant point of the primary side are determined, in order to N Taking =12 as an example, at this time = / 12, the 1st, 3rd, and 5th harmonic frequencies are 0.083 0.25 and 0.42 All frequencies are located below the primary resonant frequency, making the circuit capacitive; while... N Taking 3 as an example, = The frequencies of the 1st, 3rd, and 5th harmonics are 0.33 Hz, ... , and 1.67 The third harmonic is exactly equal to the primary resonant frequency, while the first and fifth harmonics are located in the capacitive and inductive regions, respectively.
[0033] Based on the above frequency and location characteristics N The value of is designed to serve two different phases. When N When the frequency is between 10 and 15, all harmonics are much lower than the primary resonant frequency, falling within the capacitive region, resulting in small current and negligible primary resistance. Suitable for safe identification during idle periods , And detect whether the receiver is in place. When N When the value is 3, the third harmonic falls at the primary resonant point, maximizing the sensitivity of the mutual inductance M. Simultaneously, the first and fifth harmonics are located in the capacitive and inductive regions, respectively, providing a basis for subsequent joint estimation of M. and Provide the necessary constraints. In fact, N=3 is the only integer that can simultaneously satisfy all the conditions that a harmonic exists at the primary resonant point, that a capacitive probe and an inductive probe exist, and that only the lowest three odd harmonics are used.
[0034] To further represent the system's transfer characteristics, under the SS-compensated topology, the input voltage... Current to the primary side The transfer function is:
[0035] in, This is the reflected impedance from the secondary side to the primary side through mutual inductance.
[0036] Convert to frequency domain form ( Define primary-side reactance. With secondary side reactance :
[0037] in, Given the actual value of the secondary-side compensation capacitor, the input impedance can be expressed as:
[0038] use (Based on primary-side resonant frequency normalization) and express:
[0039] Secondary side reactance is Define export ( , ):
[0040] From this, we can derive the following physical meaning: When At that time, the primary reactance (Primary-side resonance). ;when and hour, To achieve bilateral resonance; when At that time, residual reactance exists on the secondary side at the primary resonant point.
[0041] Figure 1 This is an overall flowchart of the method according to Embodiment 1 of the present invention. The method includes the following steps: S101: Inject a first square wave voltage with a first fundamental frequency into the primary resonant circuit, collect the primary current and extract the current amplitude of at least three odd harmonics, calculate the measured impedance amplitude of each harmonic, and use the measured impedance amplitude of the first group of harmonics among the at least three odd harmonics to solve for the primary inductance and the primary compensation capacitor. S102: Verify the consistency of the primary-side inductor and primary-side compensation capacitor by using the measured impedance amplitude of the second group of at least three odd harmonics to determine whether the receiver is in place. S103: After determining that the receiver is in place, reduce the DC bus voltage and inject a second square wave voltage with a second fundamental frequency. Collect the primary current again and extract the current amplitude of at least three odd harmonics. Calculate the corresponding measured impedance amplitude. Fit the measured impedance amplitude based on the asymmetric input impedance model and jointly estimate the coupling coefficient, secondary total resistance, and secondary detuning factor. S104: Restore the DC bus voltage and switch the output frequency to the actual resonant frequency of the primary side and keep it unchanged. Only adjust the DC bus voltage. Control the output current of the receiving end according to the feedforward control law based on the primary side inductance, primary side compensation capacitor, coupling coefficient, secondary side total resistance and secondary side detuning factor.
[0042] The control method proposed in this invention is divided into four stages in chronological order, and all tasks are completed solely by electrical measurements at the transmitting end.
[0043] Specifically, firstly, in step S101, primary-side parameter identification is performed. During the idle detection phase, the receiver is not in position, and the primary-side resonant circuit is an independent RLC series circuit, without the influence of secondary-side reflection impedance. The MCU controls the H-bridge inverter to inject a signal with the first fundamental frequency into the primary-side resonant circuit. First wave The fundamental frequency of this square wave voltage is set to in Choose an integer between 10 and 15 such that the 1st, 3rd, and 5th harmonic frequencies of the square wave are all much lower than the primary resonant frequency. , Within this frequency range, the primary circuit exhibits high capacitive impedance, resulting in low current and preventing resonant overcurrent; simultaneously, the capacitive region conditions... This allows the absolute value sign in the impedance magnitude equation to be directly removed, and the primary resistance... R p The error is negligible (less than 0.1%), and the influence of the reflection impedance on the primary current is extremely weak, ensuring the safety and accuracy of the identification.
[0044] The Fourier series of a square wave contains only odd harmonics:
[0045] in, The fundamental angular frequency of the square wave is shown in Table 1.
[0046] Table 1.
[0047]
[0048] The MCU obtains the ADC sampled values using the Goertzel algorithm or FFT. Extract the current amplitudes of the 1st, 3rd, and 5th harmonics. , Only the current amplitude is needed, not phase information. Utilizing and by DC bus voltage The calculated first Second harmonic voltage amplitude Define the measured impedance amplitude Under the conditions of the tolerant zone Analytical solution of primary inductance and primary side capacitor and the primary-side equivalent series resistance .
[0049] The MCU controls the H-bridge inverter to inject a signal with the first fundamental frequency into the primary resonant circuit. The first square wave voltage, the fundamental frequency of which is set to... = / N 1, of which N 1 is an integer between 10 and 15. Within this frequency range... much smaller The harmonic frequencies are all much lower than the primary resonant frequency, and its technical advantages are reflected in the following four aspects. First, the circuit exhibits capacitive high impedance, resulting in low current and preventing resonant overcurrent, thus ensuring the safety of the identification process. Second, because... ( )satisfy First, the absolute value sign in the impedance amplitude equation can be directly removed, simplifying the subsequent analytical solution process. Second, in the capacitive region, the amplitude of the primary reactance... ,neglect The introduced error is less than This significantly reduces model complexity without affecting recognition accuracy. Fourth, under low-frequency conditions, Even if the receiver is accidentally in place, the effect of the reflected impedance on the primary current is extremely weak, ensuring the accuracy of the identification results during the idle detection phase and preventing significant deviations due to accidental coupling on the secondary side.
[0050] Based on this, define intermediate variables. (Inductive reactance of the primary coil inductance at fundamental frequency) and (Capacitive reactance of the primary-side compensation capacitor at the fundamental frequency).
[0051] Capacity zone conditions ( ): .
[0052] When there is no receiver, the first The total impedance amplitude of the second harmonic is the same as the primary impedance amplitude. (neglect ):
[0053] use and Analytical solution (system of two linear equations in two variables):
[0054] in, Given the fundamental angular frequency of a square wave, this analytical solution process involves only four arithmetic operations: addition, subtraction, multiplication, and division. It has no truncation error, no iterative convergence issues, and extremely low computational complexity. The main sources of error in the analytical solution include: current amplitude caused by ADC quantization noise. Measurement error, DC bus voltage Harmonic voltage amplitude due to measurement accuracy Calculation error, and neglecting primary-side resistance Introduced systematic error ( ).
[0055] Primary-side equivalent series resistance Through the 5th harmonic ( The residuals can be used to infer the value from the quality factor. Value estimation: In the capacitive region, ,in, , To ignore The theoretical value of reactance.
[0056] At this point, step S101 has completed the parameter setting of the primary edge. , and The identification provides an accurate parameter basis for subsequent in-situ detection at the receiver.
[0057] In step S102, the second stage, the same set of measurement data from step S101 is used for receiver presence detection without additional excitation. The basic principle is that the detection is multiplexed during the IDLE period (…). The same set of measurement data (square wave) requires no additional excitation. Without a receiver, the primary side is a simple RLC series circuit. The primary inductance and compensation capacitor, derived from the 1st and 3rd harmonics, must be able to predict the response of the 5th harmonic: the three harmonic equations are self-consistent because a single RLC loop has no other degrees of freedom. With a receiver, the reflection impedance... Superimposed on the primary impedance, it changes the equivalent impedance at each harmonic, in a receiver-less model (ignoring...) Forcibly fitting the three harmonic data will yield pseudo-parameters, leading to a breakdown of self-consistency. Furthermore, the validity of this criterion is independent of whether the original secondary side parameters are symmetric. This means that self-consistency is broken, regardless of whether the secondary side parameter is equal to the primary side parameter.
[0058] When consistency error Exceeding the first threshold , or the solution ( The deviation from its design value (or long-term moving average) exceeds the second threshold. When the receiver is in place, it is determined that the receiver is present. Based on this, the fifth harmonic impedance amplitude is predicted using the intermediate variables X and Y obtained from solving the first and third harmonic equations:
[0059] Calculate the consistency error :
[0060] Criterion A is triggered to determine that the receiver is in place. To preset the first threshold, it needs to be calibrated based on the ADC accuracy and noise level. In this embodiment, a typical value is preferred. .
[0061] As a supplement, even under weak coupling conditions, criterion A is not triggered ( (Too small) The reflected impedance will still be disturbed when there is a receiving end. The solution to the equation makes the identified pseudo , fake If the deviation from its long-term sliding average or design value exceeds a preset second threshold... When this occurs, criterion B is triggered, which also determines that the receiver is in place, i.e.:
[0062] in, , This is the original design value (or the long-term moving average of the IDLE period). To avoid deviation from the threshold, this embodiment preferably uses a typical value. (Component tolerances) + Temperature drift + Measurement error margin).
[0063] The two criteria are logical OR relations; either trigger determines that the receiver is in place.
[0064] Criterion A is an active detection criterion that detects changes in circuit topology. Criterion B is a supplementary criterion; under weak coupling, criterion A may miss some changes, but deviations of pseudo-parameters from design values can still capture anomalies. The two criteria complement each other to ensure reliable detection even under weak coupling conditions.
[0065] It should be noted that, Square wave excitation is suitable for detecting the presence of the receiver (criterion B is independent). Size), but not suitable for precise estimation. Therefore, the coupling coefficient at this frequency Relationship with consistency error (asymptotic expansion) , ):
[0066] when hour, This is lower than the typical noise level of an ADC. Furthermore, although secondary-side detuning will alter the frequency characteristics of the reflected impedance, thus affecting the sensitivity of criterion A, as long as... (Receiver in place), reflected impedance Criterion A or criterion B will trigger the condition. The distinction between "in-situ but detuned" and "in-situ and resonantly aligned" is completed in the parameter estimation stage of the subsequent step S103.
[0067] In step S103, after step S102 determines that the receiver is in place, the parameter estimation stage begins.
[0068] Specifically, to ensure measurement safety, the DC bus voltage is first set to... To 5%~10% of the rated value, the MCU controls the H-bridge inverter to inject a second fundamental frequency into the primary resonant circuit. The second square wave voltage, the second fundamental frequency is set to ( This makes the third harmonic frequency exactly equal to the actual resonant frequency of the primary side. This maximizes the measurement of mutual inductance. The sensitivity (Fisher information at the resonant point) is in the capacitive region. (times); 1st harmonic ( (Located in the receptive zone, for) and Insensitive, used for independent verification of primary-side characteristic impedance ; 5th harmonic ( ( ) is in the inductive region, and its reflected impedance component is related to and The function dependency mode differs from that of the third harmonic, and together with the third harmonic, it provides decoupling. , and Required independent constraints It is the only integer that can simultaneously satisfy all the conditions of the existence of harmonics located at the primary resonant point, the existence of capacitive and inductive probes, and the use of only the lowest three odd harmonics.
[0069] After acquiring the instantaneous value of the primary current again, the MCU extracts the current amplitudes of the 1st, 3rd, and 5th harmonics using the Goertzel algorithm or FFT. And calculate the corresponding measured impedance amplitude. .
[0070] Primary inductance identified during the idle detection phase Primary resistance Primary reactance Secondary side reactance Design value of secondary coil inductance and the actual value of the secondary compensation capacitor Given a known quantity, with coupling coefficient ( , (mutual inductance), total secondary resistance ( For the secondary coil resistance, (Equivalent load resistance) and secondary side detuning factor For the parameters to be estimated, construct an asymmetric input impedance model: ; in, , , , , Secondary side detuning factor , This is the actual resonant angular frequency of the secondary side; Indicates resonant alignment. Indicates secondary side detuning; through The actual capacitance value on the secondary side can be calculated in reverse. It is used for assessing the health status of secondary limbs.
[0071] At that time, the first Subharmonic angular frequency Normalized frequency squared At this frequency configuration, the primary-side reactance is (depending only on known quantities). ):
[0072] Secondary side reactance is (dependent on the parameters to be estimated) and known design values ).Depend on definition ,have Substituting, we get:
[0073] The reflection impedance is:
[0074] The total input impedance is:
[0075] The amplitude of the model output (measured value) Amplitude information only):
[0076] Under square wave excitation with N=3, the three odd harmonics each play a different role in parameter estimation.
[0077] First harmonic ( The normalized squared frequency of ) = , = It is located in the capacitive region. At this frequency point, The reflection impedance is weak, therefore the first harmonic is weak. and Neither is sensitive; they are mainly used to verify model consistency. (The accuracy of the substitution) serves as a self-checking function.
[0078] 3rd harmonic ( )of =1, = It falls precisely at the primary resonant point. At this time, the primary reactance... , Simplified to .when The reflection impedance is purely resistive. Give directly The ratio when The reflected impedance contains a reactance component, thus carrying information about delta (δ). Therefore, the third harmonic... Maximum sensitivity, while output is received modulation.
[0079] 5th harmonic ( )of = , = It is located in the sensory region. At this frequency point... , The reflection impedance is the strongest, and the reflection resistance is the highest. and Proportional to the reflected reactance and Proportional and right and The dependency mode differs from that of the third harmonic, which is for separation. and Additional independent constraints are provided.
[0080] In summary, the first harmonic is used for self-testing, the third harmonic provides highly sensitive M information and carries δ information, and the fifth harmonic degeneracy is eliminated. The combined effect of the three harmonics ensures (…). , , The unique determination of ) in the three-dimensional parameter space.
[0081] Sensitivity analysis further supports the above frequency selection in theory.
[0082] Sensitivity of M: Definition ,exist Looking for nearby right Relative sensitivity:
[0083] exist ( harmonic): ,like but :
[0084] exist ( ): , The resonant point carries Information is a tolerant area times. The necessity of introducing And change.
[0085] Sensitivity: in Expand nearby:
[0086] exist : , This indicates that during resonant alignment The first-order sensitivity is zero, and it needs to be determined by... Provide independent constraints.
[0087] exist ( ): , The sensitivity is non-zero. yes The main information channel.
[0088] The optimality of N=3 is verified through exhaustive enumeration: square wave harmonic position constraints. The following conditions must be met simultaneously: (i) There exists a harmonic located at... (i) The primary resonant point; (ii) There are harmonics located in the capacitive region ( (iii) Harmonics exist in the inductive region ( (iv) Use only (The lowest three odd harmonics have the highest signal-to-noise ratio).
[0089]
[0090] Proof (exhaustive search, The choice depends only on the frequency position and is independent of symmetry.
[0091] Based on the measured impedance amplitudes at the three harmonic frequencies We substitute these values into a three-parameter least squares problem to solve it. The three data points exactly match the three parameters to be estimated.
[0092] in, , , .
[0093] Cost function in It exhibits unimodal and benign characteristics in space, and its three isosurfaces are nearly orthogonal. Isosurfaces: Main constraints Combinatorial relationships; isosurfaces: with Combination and Separation and ; Isosurfaces: Cross-validation Accuracy of substitution In engineering implementation, this least-squares fitting is achieved through an offline-computed three-dimensional lookup table. Achieve online Solve this problem. Look up the table using... (Impedance amplitude after removing the primary resistance at the resonant point). (Inductive point impedance amplitude). (Capacitive point impedance amplitude) is the input. The MCU can obtain the estimation result by online table lookup and trilinear interpolation, without iteration. Each dimension of the three-dimensional lookup table... Grid, total storage approximately Entries (each entry is 12 bytes, corresponding to...) MB), recommended to use per dimension Grid point ( k entries MB (mainstream DSP on-chip Flash can meet the requirements) or external SPI Flash storage with a large grid table.
[0094] If storage resources are limited, it is also possible Obtained from a two-dimensional lookup table with initial values Then, using the Gauss-Newton method 1 2-step refinement . exist Within the range, the iterative convergence is rapid. A sequential estimation strategy is adopted: first, the ratio of the measured impedance amplitudes of the 3rd and 5th harmonics is used. right Sensitive feature locking Candidate intervals, then with =1 is the initial value obtained from a two-dimensional lookup table. Initialize the values, then refine them using the Gauss-Newton method for one to two iterations. It may converge to the final solution after 2 to 3 Levenberg-Marquardt iterations.
[0095] Least squares fit residuals Used for model self-consistency diagnosis. When Less than the first threshold When the model is self-consistent and the three-parameter estimation is reliable, it enters the charging phase; when Between the first threshold With the second threshold When the values are between, it indicates a slight deviation (e.g., R). p Not allowed or L s (Slight drift), enter charging and record alarm; when Exceeding the second threshold When this occurs, it indicates a severe mismatch (such as a secondary coil failure or L). s (Severe deviation from design value), charging is prohibited and the system returns to idle detection state, where the threshold is... Based on the system noise level calibration, in this embodiment, the first threshold J1 is preferably 5% to 10% of the baseline residual, and the second threshold... The preferred value is 25% to 30% of the baseline residual.
[0096] In particular, if only estimates ( , t) and fixed =1 If the threshold is exceeded, it indicates that there is a detuning on the secondary side. This will significantly increase, and this signal constitutes an independent criterion for detecting secondary-side detuning; therefore, it should be upgraded to include... Three-parameter estimation. Through The actual capacitance value of the secondary side can be calculated in reverse, which can be used for secondary side health status assessment: (32); During the N=3 square wave measurement, a series of measures were taken to ensure safety. First, the DC bus voltage was reduced to 5%~10% of its rated value, so that the resonant point current was approximately equal to... This ensures that the current remains within a safe range. Secondly, the measurement time is only [time required]. One fundamental frequency period, when the fundamental frequency At kHz, the corresponding time is approximately 140 to 280 microseconds, which is considered a short-time measurement. Simultaneously, the MCU monitors the primary-side current cycle by cycle. The peak value is immediately shut off once it exceeds the set threshold. In terms of measurement sequence, the first harmonic is measured first. ), confirm characteristic impedance and primary resistance After aligning with the idle detection period (IDLE), measure the 3rd and 5th harmonics. Furthermore, if the 3rd harmonic is located at ( Input impedance magnitude Significant deviation based on The assumed expected range will issue an early warning of detuning.
[0097] In step S104, after the parameter estimation in step S103 is completed and the residual diagnosis is passed, the charging control stage begins.
[0098] First, switch the inverter output frequency to the primary resonant frequency. And remain unchanged (by identification) (Confirmed) No frequency modulation is performed during charging; the only control variable is the DC bus voltage. At this frequency, the primary resonant frequency is... At the location, the original side reactance Secondary side reactance If the secondary resonators are aligned ( The circuit is purely resistive, resulting in minimal reactive power and maximum efficiency. If... There is residual reactance on the secondary side. Efficiency decreases slightly, but the feedforward control law remains effective (because...). (Already estimated).
[0099] To achieve the desired value of the rectified output current at the receiving end. Tracking control, according to feedforward control law Calculate the required DC bus voltage to ensure the rectified output current at the receiving end. Tracking Expectations There is no secondary-side communication throughout the entire process. At the primary-side resonant frequency, the input impedance is:
[0100] in, for The abbreviation of .
[0101] The amplitude of the primary current is (when sinusoidal modulation) Square wave time ):
[0102] Secondary side induced voltage Secondary current .
[0103] The rectified output DC current is (full-bridge rectifier, CCM):
[0104] The complete forward transfer function is (taking square wave excitation as an example, fundamental wave amplitude) ):
[0105] Solve by inverse equation above :
[0106] in:
[0107] The parameters required for this control law are all identified or estimated values: , This is an estimate of the idle period. (Depend on (conversion) and The joint estimation result of step S103, This is the design value for the secondary inductance. This is the set value.
[0108] When the secondary resonance is aligned hour, The control law simplifies to:
[0109] in, It is the primary resonant angular frequency. The target output current.
[0110] All of the above control processes do not require secondary-side communication, and only the amplitude of the primary-side current needs to be collected without voltage-current phase difference information. The ADC sampling rate only needs to meet the requirement that the Nyquist frequency is higher than 5 times the fundamental frequency.
[0111] During charging, online parameter tracking can be performed periodically: briefly stopping power transmission and reducing... Switch to Square wave, retest Re-evaluation , and The system tracks changes in mutual inductance caused by minute movements of the AGV, drift in the secondary resonant frequency caused by temperature changes, and changes in the total secondary resistance caused by changes in battery charging state. After updating the feedforward control law, the system restores the primary resonant frequency operation.
[0112] As an alternative, the perturbation-observation method can be used for online tracking without interrupting charging: small changes (1%~2%), monitoring rate of change Online tracking The change. If If the change exceeds a preset threshold, it will trigger. During repeated testing, the frequency remained constant. In this embodiment, the preset threshold is preferably 5% of the reference impedance value, that is, when When the change exceeds 5% of the baseline value, a retest is triggered. In practical applications, the value can be adjusted within the range of 3% to 10% depending on the system noise level and measurement accuracy.
[0113] It should be noted that the main control error comes from , and Estimation bias. In the strongly coupled region ( ):
[0114] Right now right and (pass Sensitive to Not sensitive.
[0115] In the weak coupling region ( ):
[0116] Right now right , , All three are sensitive. However, at this time, the AGV is not precisely aligned, so the control precision requirement is correspondingly reduced.
[0117] The estimation error not only affects the secondary reactance Also through The accuracy of the estimation indirectly affects the control quantity, therefore M and The joint solution is of great significance for ensuring control accuracy.
[0118] In summary, the MCU or DSP controller in this embodiment is configured with three operating modes: the first is the identification mode, corresponding to the idle detection phase, in which case... N 1. Selecting values from 10 to 15, the controller outputs a square wave with a fundamental frequency much lower than the primary resonant frequency. Since the fundamental frequency is much lower than the primary resonant frequency, the amplitude of the multi-harmonic current is extracted and used for the primary side. The first type is the analysis and identification, and the second type is the estimation mode, corresponding to the parameter estimation stage, at which time... N The controller outputs a square wave with a 3rd harmonic frequency equal to the primary resonant frequency. The amplitudes of the 1st, 3rd, and 5th harmonic currents are extracted for joint estimation. (or ), and The third mode is the charging mode, which corresponds to the charging control phase. In this mode, the controller output frequency is fixed at the actual resonant frequency of the primary side. The resonant sine wave or resonant square wave is obtained by adjusting the DC bus voltage alone. Controlling output power. The three modes mentioned above cover the complete workflow from standby detection, parameter identification, online estimation to charging control.
[0119] Example 2 This embodiment provides a primary-side control device for an SS-WPT system that does not require secondary-side communication, including: H-bridge inverter, used to output square wave voltage to the primary resonant circuit; A current sensor is used to collect the primary current. The ADC module is used to sample the DC bus voltage and primary current. The controller is connected to the H-bridge inverter, the current sensor, and the ADC module, and is configured to execute the method as described in Example 1.
[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A primary-side control method for an SS-WPT system that does not require secondary-side communication, characterized in that, include: Inject a first square wave voltage with a first fundamental frequency into the primary resonant circuit, collect the primary current and extract the current amplitude of at least three odd harmonics, and calculate the measured impedance amplitude of each harmonic. The primary inductance and primary compensation capacitor are solved using the measured impedance amplitude of the first group of harmonics among the at least three odd harmonics. The primary-side inductor and primary-side compensation capacitor are verified for consistency using the measured impedance amplitude of the second group of harmonics among the at least three odd harmonics, in order to determine whether the receiving end is in place. Once the receiver is determined to be in place, the DC bus voltage is reduced and a second square wave voltage with a second fundamental frequency is injected. The primary current is collected again and the current amplitudes of at least three odd harmonics are extracted. The corresponding measured impedance amplitudes are calculated, and the measured impedance amplitudes are fitted based on the asymmetric input impedance model. The coupling coefficient, the total resistance of the secondary side, and the detuning factor of the secondary side are jointly estimated. The DC bus voltage is restored and the output frequency is switched to the actual resonant frequency of the primary side and kept unchanged. Only the DC bus voltage is adjusted. The output current of the receiving end is controlled according to the feedforward control law based on the primary side inductance, primary side compensation capacitor, coupling coefficient, secondary side total resistance and secondary side detuning factor.
2. The method according to claim 1, characterized in that, The first group of harmonics consists of the 1st and 3rd harmonics, and the second group of harmonics consists of the 5th harmonic.
3. The method according to claim 1, characterized in that, The fundamental frequency of the first square wave voltage is set such that at least three odd harmonic frequencies are lower than the primary resonant frequency.
4. The method according to claim 1, characterized in that, The second fundamental frequency satisfies This makes the third harmonic frequency equal to the actual resonant frequency of the primary side, where, The primary resonant frequency, It is the fundamental frequency of the square wave.
5. The method according to claim 1, characterized in that, The consistency verification includes: determining the receiver's position by comparing the measured impedance amplitude with the predicted impedance amplitude of the second set of harmonics; when the error exceeds a preset first threshold, the receiver is determined to be in place; and the predicted impedance amplitude is verified by A. 5_pred =(9A3 The value is calculated as 2A1) / 5, where A1 and A3 are the measured impedance amplitudes of the 1st and 3rd harmonics in the first group of harmonics, respectively.
6. The method according to claim 1, characterized in that, The consistency verification also includes: when the primary-side inductor or the primary-side compensation capacitor deviates from the reference value by more than a preset second threshold, it is determined that the receiver is in place.
7. The method according to claim 1, characterized in that, The measured impedance amplitude is fitted based on the asymmetric input impedance model, and the coupling coefficient, total secondary resistance, and secondary detuning factor are jointly estimated, specifically as follows: With the primary inductor Primary-side compensation capacitor Primary resistance Secondary inductor and nominal value of secondary capacitor Given a known quantity, with coupling coefficient Total resistance of the secondary side and secondary side detuning factor For the parameters to be estimated, construct an asymmetric input impedance model: ； in, , , , , ; Using the measured impedance amplitude at three harmonic frequencies as the target, the parameters to be estimated are fitted to minimize the sum of squared errors between the impedance amplitude output by the model and the measured impedance amplitude, thereby obtaining the coupling coefficient, the total resistance of the secondary side, and the detuning factor of the secondary side.
8. The method according to claim 1, characterized in that, The DC bus voltage is restored and the output frequency is switched to and kept constant at the primary side's actual resonant frequency. Only the DC bus voltage is adjusted. Based on the primary side inductance, primary side compensation capacitor, coupling coefficient, secondary side total resistance, and secondary side detuning factor, the receiver output current is controlled according to the feedforward control law, specifically as follows: The output frequency is the actual resonant frequency of the primary side. Under the given conditions, the secondary reactance is: ； The primary input impedance amplitude is: ； Based on the target output current The required DC bus voltage is calculated according to the following feedforward control law: ； The output current of the receiving end is controlled by the DC bus voltage.
9. The method according to claim 1, characterized in that, During charging, power transmission is periodically paused and the joint estimation is performed again to update the coupling coefficient, secondary side total resistance, and secondary side detuning factor, and the feedforward control law is refreshed based on the updated parameters.
10. A primary-side control device for an SS-WPT system that does not require secondary-side communication, characterized in that, include: H-bridge inverter, used to output square wave voltage to the primary resonant circuit; A current sensor is used to collect the primary current. The ADC module is used to sample the DC bus voltage and the primary current. The controller is connected to the H-bridge inverter, the current sensor, and the ADC module, respectively, and is configured to perform the method as described in any one of claims 1 to 9.