Comprehensive bilateral LCC compensation WPT system output mode regulation and control method

Abstract

The invention provides a comprehensive bilateral LCC compensation WPT system output mode regulation and control method, and relates to the technical field of wireless power transmission. A variable capacitance compensation unit is introduced to a receiving side, a fuzzy-PI composite control strategy is combined, an error and an error change rate are calculated according to output current and voltage signals, the equivalent capacitance of a compensation branch is adjusted in real time, and self-adaptive switching between a constant current mode and a constant voltage mode is achieved; meanwhile, the system resonance condition is maintained when the coupling coefficient changes, the power transmission efficiency and the system stability are improved, and good dynamic response and control robustness are achieved.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission technology, and in particular to a comprehensive bilateral LCC compensation WPT system output mode control method. Background Art

[0002] Existing bilateral LCC-compensated wireless power transfer (WPT) systems generally have three major pain points:

[0003] ① The change in the coil coupling coefficient with displacement or offset causes large fluctuations in output power, efficiency and resonance point, and insufficient anti-offset tolerance;

[0004] ② Constant current (CC) and constant voltage (CV) operating modes usually rely on peripheral switching circuits or single linear control, resulting in structural dispersion and delayed response;

[0005] ③ Traditional pure PI or pure fuzzy control is difficult to take into account both rapid response to large disturbances and high steady-state precision, and is prone to overshoot, undershoot, or even loss of lock when the load changes suddenly or the coupling changes. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a comprehensive bilateral LCC compensated WPT system output mode control method. In response to the problems of the existing bilateral LCC compensated WPT system such as slow mode switching response, sensitive resonance offset and insufficient control accuracy, an output mode control method with adaptive control capability and high robustness is proposed, which significantly improves the stability and dynamic performance of the system.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A comprehensive bilateral LCC-compensated WPT system output mode control method includes:

[0009] A variable capacitance compensation unit is set on the receiving side, and together with the transmitting side LCC network, a resonant circuit is formed;

[0010] Collect output current and output voltage signals to obtain output error and error change rate;

[0011] Inputting the output error and the error change rate into a fuzzy-PI composite controller to generate a duty cycle adjustment amount;

[0012] driving a semiconductor switch connected in parallel to the variable capacitance compensation unit according to the duty cycle adjustment amount, so that the equivalent capacitance is continuously adjustable within a preset range;

[0013] When the output voltage reaches the set threshold, it automatically switches to constant voltage mode and maintains the target voltage; when the output voltage is lower than the threshold, it maintains constant current mode and maintains the target current;

[0014] When the spatial coupling coefficient of the coil changes, the equivalent capacitance is adjusted in real time to keep the system operating frequency constant and the efficiency not lower than a preset threshold.

[0015] Preferably, the fuzzy controller in the fuzzy-PI composite controller adopts a dual-input single-output structure, the two inputs are the error and the error change rate, the inference rule adopts Mamdani-type reasoning, and the defuzzification method is the center of gravity method.

[0016] Preferably, the fuzzy controller adaptively generates a proportional coefficient and an integral coefficient based on the output error obtained in real time; wherein, the output error is the difference between the target output value and the actual output value; when the absolute value of the output error is less than or equal to the set steady-state error tolerance threshold, the fuzzy controller keeps the current proportional coefficient and the integral coefficient unchanged.

[0017] Preferably, before driving the semiconductor switch connected in parallel to the variable capacitance compensation unit according to the duty cycle adjustment amount, the zero-crossing moment of the compensation branch current is detected, and the duty cycle signal is updated at the zero-crossing moment to reduce switching losses and suppress harmonics.

[0018] Preferably, when the spatial coupling coefficient between the transmitting coil and the receiving coil changes, the equivalent capacitance is adjusted in real time to keep the system resonance condition unchanged, keep the operating frequency constant, and ensure that the system efficiency is not lower than a set threshold.

[0019] Preferably, the sampling period of the output error and the error change rate is set synchronously with the PWM modulation period to ensure that the control loop is closed in real time.

[0020] Preferably, a near-field communication or low-power wireless link is provided between the transmitting side and the receiving side for exchanging the current working mode, target reference value and real-time error information. The fuzzy-PI composite controller dynamically updates the control parameters according to the feedback from the receiving side to realize closed-loop collaborative control.

[0021] The present invention discloses the following technical effects:

[0022] The present invention introduces a variable capacitance compensation unit on the receiving side and combines it with a fuzzy-PI composite control strategy. This allows the equivalent capacitance to be dynamically adjusted according to the output error and its rate of change, thereby achieving automatic switching between constant voltage and constant current modes and adapting to different load requirements. At the same time, in response to the resonance offset problem caused by changes in the spatial coupling coefficient of the coil, the method can adjust the compensation parameters in real time to keep the system resonant frequency constant, significantly improving the power transmission efficiency and anti-offset robustness of the system, and ensuring the stability and reliability of the wireless power transmission system under multiple working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A flow chart of a method provided by an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the circuit structure of a WPT system with a bilateral LCC topology according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of the operating waveform of the SCC provided in an embodiment of the present invention;

[0027] Figure 4 The embodiment of the present invention provides 、 and relationship diagram;

[0028] Figure 5 The embodiment of the present invention provides 、 and relationship diagram;

[0029] Figure 6 The embodiment of the present invention provides Graph of the range of change;

[0030] Figure 7 The embodiment of the present invention provides Graph of the range of change;

[0031] Figure 8 A coil structure diagram provided in an embodiment of the present invention;

[0032] Figure 9 A correspondence table between mutual inductance values ​​and offsets provided in an embodiment of the present invention;

[0033] Figure 10 This is an output diagram when a constant voltage provided by an embodiment of the present invention is offset. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The purpose of the present invention is to provide a comprehensive output mode control method for a bilateral LCC compensated WPT system. To address the problems of existing bilateral LCC compensated WPT systems such as slow mode switching response, sensitive resonance offset, and insufficient control accuracy, an output mode control method with adaptive control capability and high robustness is proposed, which significantly improves the stability and dynamic performance of the system.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1 A flow chart of the method provided in the embodiment of the present invention is shown in FIG. Figure 1 As shown, the present invention provides a comprehensive bilateral LCC compensation WPT system output mode control method, including:

[0038] Step 100: Setting a variable capacitance compensation unit on the receiving side and forming a resonant circuit together with the transmitting side LCC network;

[0039] Step 200: Collect output current and output voltage signals to obtain output error and error change rate;

[0040] Step 300: Input the output error and the error change rate into a fuzzy-PI composite controller to generate a duty cycle adjustment value;

[0041] Step 400: driving a semiconductor switch connected in parallel to the variable capacitance compensation unit according to the duty cycle adjustment amount, so that the equivalent capacitance is continuously adjustable within a preset range;

[0042] Step 500: When the output voltage reaches a set threshold, the system automatically switches to a constant voltage mode and maintains the target voltage; when the output voltage is lower than the threshold, the system maintains a constant current mode and maintains the target current;

[0043] Step 600: When the spatial coupling coefficient of the coil changes, the equivalent capacitance is adjusted in real time to keep the system operating frequency constant and the efficiency not lower than a preset threshold.

[0044] Specifically, such as Figure 2 As shown, this embodiment introduces a variable capacitance compensation unit (SCC) composed of MOSFET tubes and capacitors connected in series and parallel based on the traditional double-sided LCC topology to achieve real-time dynamic adjustment of the capacitance value. The system includes two independent SCCs, which are configured on the secondary side to replace the C in the original topology. s and C2, two Mosfet tubes S a and S b connected in series with the capacitor C x Connect in parallel to reduce S a and S b The voltage stress of capacitor C y is used as a voltage divider connected in series. SCC can be implemented to allow continuous tuning of C s_eq and C 2_eq The equivalent capacitance of the SCC unit is used to change the resonant factors m and n. Unlike traditional bilateral LCC networks, this system operates under detuned conditions. The SCC unit precisely controls the conduction angle of the MOSFET tube, achieving continuous capacitance adjustment within a certain range, effectively improving the system's coil coupling tolerance and adaptability. First, utilizing the fully resonant nature of this structure, the KVL operation is used to obtain the following relationship matrix:

[0045]

[0046] Among them, U in is the system input voltage; I in and I out , I p , I s are the currents flowing through the compensation (CX) coil, the transmitting (TX) coil, and the receiving (RX) coil respectively; L1 is the inductance of the transmitting side CX coil; M is the mutual inductance between the TX coil and the RX coil; C1 and C2 are the resonant capacitances of the transmitting side and receiving side CX coils respectively; C p and L p 、C s and L s are the resonant capacitance and inductance of the TX and RX coils respectively; L2 is the inductance of the CX coil on the receiving side; C L is the filter capacitor; R out is the system load; j is a complex unit; ω is the input angular frequency.

[0047] According to the resonance conditions, the characteristics of complete resonance on the transmitting side are maintained, and a resonance factor is introduced on the receiving side. The resonance state of the receiving side is represented by changing the size of the resonance factor.

[0048] ,

[0049] in , .

[0050] Derived input current , output current and output voltage The expression serves as a standard for future parameter settings and selections:

[0051]

[0052]

[0053]

[0054] Then, based on the output characteristics, the output values ​​are sorted and simplified:

[0055]

[0056]

[0057]

[0058]

[0059] in: , .

[0060] To ensure that the output current and voltage are constant and independent of the load, the resistance coefficient needs to be kept constant. The boundary conditions are as follows:

[0061]

[0062] in 0 or .

[0063]

[0064] same, 0 or .

[0065] The output conditions need to be integrated and discussed to ensure that they are adjustable and can meet the working conditions of the adjustable capacitor.

[0066] The working state and working mode of the adjustable capacitor are as follows Figure 3 As shown, the equivalent capacitance can be calculated as:

[0067]

[0068] When finding the relationship between output equivalent capacitance, conduction time, and series-parallel capacitance, three independent variables and one dependent variable are involved. Therefore, it is impossible to express it intuitively through a single graph. Figure 4 and Figure 5 As shown, we first fixed one variable for verification. This method is scientific, effective, and intuitive. The same problem arises when selecting the final parameters at the output. All boundary conditions and output methods need to be discussed together.

[0069] When the constant current condition is used, the focus is on When it is 0, constant voltage mode, focus on for At this time, the relationship between k1 and k2 cannot be ignored. As well as their relationship with the output, the change diagram of the two quantities is as follows: Figure 6 and Figure 7 shown.

[0070] The above is the theoretical method and design steps for maintaining constant current and constant voltage mode at the output end.

[0071] In the analysis of anti-deviability, a simulation model was established using COMSO. Figure 8 As shown, the use of a circular coil can reduce the horizontal offset test.

[0072] With the same design of constant output mode, the offset only needs to control the change of M. The output formula at this time is as follows:

[0073]

[0074]

[0075] in: , , is the change in mutual inductance M caused by the offset in the k direction. k can be x, z, or x and z.

[0076] Comsol was used to simulate the variation of mutual inductance M within the offset distance, obtaining different mutual inductance values ​​corresponding to different offsets. These values ​​were then compared with the controllable ranges of m and n for constant mode switching and their intersection was determined. This allowed the system's anti-offset resistance to be improved by controlling the resonance factor.

[0077] Different offset positions correspond to different mutual inductance values, such as Figure 9 shown.

[0078] Optionally, this embodiment also designs a fuzzy and PI hybrid controller, which uses the fuzzy controller to achieve fast nonlinear large-range adjustment to cope with complex nonlinear conditions such as sudden load changes and changes in coupling coefficients; at the same time, the PI controller is used to fine-tune the steady-state control to ensure the system's fast dynamic response and high steady-state precision.

[0079] Fuzzy control adopts a dual-input single-output approach and a parallel control method. Error and error change rate are used as inputs to the fuzzy controller.

[0080]

[0081]

[0082]

[0083]

[0084] According to the variation range of output current and voltage, the error range and error variation rate range of the output terminal are reasonably set. Then the normalization coefficient is effectively selected. Different fuzzy controllers output different k p and k i . Four groups of fuzzy control need to be introduced.

[0085] The fuzzy control rules are shown in the table below.

[0086] Table 1 Constant current mode Rules Table

[0087] #timg# NB NM NS ZE PS PM PB NB PB PB PB PM PS ZE ZE NM PB PB PM PS ZE NS NS NS PB PM PS ZE NS NM NB ZE PM PS ZE ZE PS PM PM PS PS ZE NS PS PM PB PB PM ZE NS NM PM PB PB PB PB ZE NS NB PB PB PB PB

[0088] Table 2 Constant current mode Rules Table

[0089] #timg# NB NM NS ZE PS PM PB NB PB PB PM PS ZE ZE ZE NM PB PM PS ZE NS NS NS NS PM PS ZE NS PS PS NS ZE PS ZE NS ZE PS ZE PS PS PS NS PS ZE PS PM PB PM ZE NS PS ZE PM PB PB PB ZE ZE ZE PS PB PB PB

[0090] Table 3 Constant voltage mode Rules Table

[0091] #timg# NB NM NS ZE PS PM PB NB PB PB PM PS ZE NS NB NM PB PM PS ZE NS NM NB NS PM PS ZE NS PS NM NM ZE PS ZE NS ZE NS ZE PS PS ZE NS PS PS PS PM PB PM NS NM PM PB PM PB PB PB NB NS NM PB PM PB PB

[0092] Table 4 Constant voltage mode Rules Table

[0093] #timg# NB NM NS ZE PS PM PB NB PB PB PM PS ZE ZE ZE NM PB PM PS ZE NS NS NS NS PM PS ZE NS PS PS NS ZE PS ZE NS ZE PS ZE PS PS ZE NS PS PS PS PM PB PM ZE NS PS PM PM PB PB PB ZE ZE ZE PB PB PB PB

[0094] After the parameters enter the fuzzy rules, the corresponding fuzzy output is generated. The Mamdani method is used for reasoning, and the fuzzy reasoning rules are as follows:

[0095] if e = and =

[0096] then = =

[0097] In the formula , , , They are defined as, , , The fuzzy domain on .

[0098] The precise amount is output to the accumulator, so the result must be defuzzified. The area centroid method is used for defuzzification:

[0099]

[0100] After fuzzy rule inference and defuzzification, the output signal is fed into the PI control module for fine-tuning. This output serves as the duty cycle control variable for the PWM signal, acting on the MOSFET switch connected in parallel with the variable capacitor. The system incorporates rising and falling edge zero-crossing detection technology, capturing the instantaneous polarity transitions of the variable capacitor branch current in real time. This technology, in conjunction with the PI control module's output, adjusts the MOSFET's on- and off-times to precisely achieve dynamic tuning of the variable capacitor, effectively improving the system's steady-state performance and transient response speed, while enhancing its robustness to load fluctuations and parameter changes.

[0101] The simulation data is exported as a control signal to reduce the amount of calculation of DSP28335 and improve the calculation speed.

[0102] As an optional implementation, the simulation parameter selection of this embodiment is shown in Tables 5 and 6.

[0103] Table 5 System parameters

[0104] type parameter Numerical #timg# Input voltage 20V #timg# Transmitter coil inductance 50.4uH #timg# Transmitter side capacitor 138.5 nF #timg# Transmitting coil equivalent resistance 0.1Ω #timg# Receiving coil inductance 34.8uF #timg# Receiving coil variable capacitance x 50 nF #timg# Receiving coil variable capacitance y 500 nF #timg# Receiving coil equivalent resistance 0.03Ω #timg# Primary compensation inductor 25.3 uH #timg# Primary compensation capacitor 190.1nF #timg# Primary side compensation inductor equivalent resistance 0.05Ω #timg# Secondary side compensation inductor 7.1uH #timg# Compensation capacitor variable capacitor x 20 nF #timg# Compensation capacitor variable capacitor y 400 nF #timg# Secondary side compensation inductor equivalent resistance 0.04Ω #timg# Coupling coefficient 0.29 #timg# System frequency 85kHz

[0105] Table 6 Coil parameters

[0106] structure parameter Transmitter coil radius 125mm Receiver coil radius 100mm Diameter of Litz wire 2.24mm Initial distance between the transmitting coil and the receiving coil 50mm

[0107] In this example, the target current is set to 2A and the target voltage is set to 6V. The output current response of this system in constant current mode is shown below. During startup, the controller rapidly increases the current from 0A to approximately 3.0A (+1.0A overshoot), achieving peak value in approximately 1ms. It then converges to the setpoint of 2.00A after a damped oscillation of 5.04ms. Thereafter, the steady-state ripple remains within ±0.01A. When a small disturbance is applied at 20ms, the current drops to 1.45A (–0.55A deviation) and rebounds to 2.07A (+0.07A). However, the control loop re-locks the current within the ±0.02A error band within 2.65ms. A larger disturbance occurs at 39.6ms, causing the current amplitude to expand to 1.01A–2.72A, but it still recovers to near the setpoint within 4.65ms. The above results show that the proposed fuzzy+PI hybrid control can not only achieve fast tracking at the millisecond level, but also has strong suppression capabilities for disturbances of different amplitudes and high-precision steady-state performance. It is very suitable for wireless power transmission scenarios with strict requirements on output current stability.

[0108] Furthermore, this embodiment demonstrates the controller's mode switching and constant voltage (CV) response when the voltage rises to 6V: At approximately 150ms, the reference voltage jumps to 6V, and the system detects that the output voltage has reached the mode switching threshold, automatically switching from constant current to constant voltage control. During this transition, the output voltage peaks at 7.86V and valleys at 5.96V (with a peak-to-valley swing of 1.90V), but converges to 6.00V±0.02V in just 1.02ms. When subjected to another sudden load change at 179.6ms, the voltage fluctuates to 5.93V–7.50V, but recovers to the steady-state range within 2.10ms. Subsequent steady-state ripple is also suppressed to ±0.02V. This demonstrates that this fuzzy + PI control strategy not only maintains extremely fast dynamic response during mode switching but also demonstrates excellent robustness and high precision during the constant voltage phase, fully meeting the dual requirements of output voltage accuracy and stability for wireless power transmission systems.

[0109] The controller uses DSP28335, which directly reads the fuzzy PI data generated during simulation to reduce the amount of calculation. Figure 10 shown.

[0110] Under constant voltage mode operating conditions, when the relative position of the system coil undergoes a certain degree of offset disturbance, the output voltage will fluctuate slightly within a short period of time, with an amplitude of approximately 0.15V to 0.37V. Subsequently, the system responds quickly through a closed-loop regulation strategy that combines fuzzy control and PI control. Through precise duty cycle modulation and dynamic adjustment of the variable capacitor, the output voltage can quickly converge in a very short time, stabilize near the target constant voltage value of 6V, and keep the steady-state ripple within a very small range. The above results fully demonstrate that the hybrid control strategy adopted by this system has excellent anti-disturbance capability and good dynamic recovery performance. It can effectively suppress the output voltage fluctuation problem caused by coil position offset, significantly improve the steady-state accuracy and dynamic response characteristics of the wireless power transmission system, and meet the strict technical requirements for high stability in actual application scenarios.

[0111] The present invention proposes a comprehensive bilateral LCC compensated wireless power transmission system output mode control technology, which effectively solves the problems existing in the prior art, such as insufficient coil coupling tolerance, inconsistent mode switching structure, and poor system adaptability.

[0112] Based on the traditional bilateral LCC topology, this invention introduces a variable capacitance compensation unit (SCC) consisting of a MOSFET and a capacitor connected in series and parallel. This system proposes a resonant factor, enabling real-time dynamic adjustment of the compensation capacitance value, effectively improving the system's steady-state and dynamic performance under disturbances such as position offsets. Regarding the control strategy, this invention creatively proposes a hybrid control scheme combining fuzzy and PI control. The fuzzy control module rapidly responds to a wide range of nonlinear disturbances, while the PI module performs detailed steady-state corrections, ensuring excellent stability and dynamic response characteristics of the output current and voltage. A fuzzy PI control method is used to control the output signal and precisely adjust the MOSFET duty cycle, thereby achieving precise dynamic tuning of the variable capacitance.

[0113] Simulation and experimental results demonstrate the excellent performance of the proposed control strategy under disturbances such as output mode switching and coil position offsets. In constant current mode, the controller rapidly eliminates overshoot caused by these disturbances. In constant voltage mode, the output voltage quickly stabilizes to the target voltage of 6V after an offset disturbance, with a fluctuation amplitude of only 0.15 to 0.37V. This proposed technical solution has broad application prospects in the field of wireless power transmission, significantly improving system efficiency and stability in practical applications such as wireless charging of electric vehicles and portable devices.

[0114] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0115] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A comprehensive bilateral LCC compensated WPT system output mode control method, characterized by: include: A variable capacitance compensation unit is set on the receiving side, and together with the transmitting side LCC network, a resonant circuit is formed; Collect output current and output voltage signals to obtain output error and error change rate; Inputting the output error and the error change rate into a fuzzy-PI composite controller to generate a duty cycle adjustment amount; driving a semiconductor switch connected in parallel to the variable capacitance compensation unit according to the duty cycle adjustment amount, so that the equivalent capacitance is continuously adjustable within a preset range; When the output voltage reaches the set threshold, it automatically switches to constant voltage mode and maintains the target voltage; when the output voltage is lower than the threshold, it maintains constant current mode and maintains the target current; When the spatial coupling coefficient of the coil changes, the equivalent capacitance is adjusted in real time to keep the system operating frequency constant and the efficiency not lower than a preset threshold; When the spatial coupling coefficient between the transmitting coil and the receiving coil changes, the equivalent capacitance is adjusted in real time to maintain the system resonance condition unchanged, keep the operating frequency constant, and ensure that the system efficiency is not lower than the set threshold; a near-field communication or low-power wireless link is provided between the transmitting side and the receiving side for exchanging the current operating mode, target reference value and real-time error information; the fuzzy-PI composite controller dynamically updates the control parameters according to the feedback from the receiving side to achieve closed-loop collaborative control.

2. The comprehensive bilateral LCC-compensated WPT system output mode control method according to claim 1 is characterized in that: The fuzzy controller in the fuzzy-PI composite controller adopts a dual-input single-output structure, the two inputs are the error and the error change rate, the inference rule adopts Mamdani-type inference, and the defuzzification method is the center of gravity method.

3. The comprehensive bilateral LCC-compensated WPT system output mode control method according to claim 2 is characterized in that: The fuzzy controller adaptively generates a proportional coefficient and an integral coefficient based on an output error acquired in real time; wherein the output error is the difference between a target output value and an actual output value; when the absolute value of the output error is less than or equal to a set steady-state error tolerance threshold, the fuzzy controller maintains the current proportional coefficient and the integral coefficient unchanged.

4. The comprehensive bilateral LCC-compensated WPT system output mode control method according to claim 1 is characterized in that: Before driving the semiconductor switch connected in parallel to the variable capacitance compensation unit according to the duty cycle adjustment amount, the zero-crossing moment of the compensation branch current is detected, and the duty cycle signal is updated at the zero-crossing moment to reduce switching loss and suppress harmonics.

5. The comprehensive bilateral LCC compensated WPT system output mode control method according to claim 1 is characterized in that: The sampling period of the output error and the error change rate is set synchronously with the PWM modulation period to ensure that the control loop is closed in real time.

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