Composite control method of wireless power transmission system

Abstract

The invention discloses a composite control method of a wireless power transmission system, the system comprises a transmitting end and a receiving end, and the transmitting end comprises a voltage source, a full-bridge inverter circuit, a transmitting end S network and a transmitting coil; and the receiving end comprises a receiving end S network, a high-frequency rectification filter circuit, a double-tube Buck-Boost circuit and a load RL. The control method can realize compound control of coupling coefficient identification, maximum efficiency tracking and constant voltage output. The problem that in the prior art, when a coupling coil shifts and loads suddenly change, a system cannot carry out efficient and stable output is solved, and compared with existing common PI control, the linear active-disturbance-rejection technology used in the invention is better in control effect.

Description

Technical Field

[0001] The invention relates to a composite control method for a wireless power transmission system, belonging to the technical field of wireless power transmission. Background Art

[0002] Compared with traditional wired power transmission, wireless power transmission technology transmits energy from power source to load in a non-contact manner, which improves the freedom, safety and aesthetics of power cables. It has been widely used in electric vehicles, underwater equipment, smart furniture and other fields. In practical applications, the transmission performance and output characteristics of wireless power transmission systems will be affected by transmission distance and load changes. Therefore, in order to ensure the stable and efficient transmission performance of wireless power transmission systems, it is necessary to study the output control of the system.

[0003] The wireless power transmission system is composed of multiple circuits (including DC source, full-bridge inverter circuit, resonant compensation circuit, electromagnetic coupling mechanism, rectifier circuit, DC-DC converter circuit, etc.), which makes the wireless power transmission system a high-order nonlinear system. In order to achieve stable and efficient power transmission of the system, the system must be controlled in a complex manner. At present, some nonlinear control strategies have been applied to the wireless power transmission system, but the control effect of the wireless power transmission system is not ideal. Summary of the invention

[0004] Purpose of the invention: The present invention aims at the problem of how a wireless power transmission system can achieve stable and efficient power transmission, and proposes a composite control method for a wireless power transmission system. The present invention uses a first-order linear anti-disturbance control controller for the voltage stabilization control of the wireless power transmission system, impedance matching technology is used for optimal efficiency tracking control, and resonant circuit voltage and current sampling is used for coupling coefficient identification. First, the resonant circuit voltage and current are sampled to obtain the coupling coefficient, and the maximum efficiency tracking is achieved by changing the duty cycle of the Buck-Boost circuit at the receiving end, and the collected load voltage is used to perform inverter phase shift control using linear anti-disturbance technology to achieve constant voltage output.

[0005] Technical solution: A composite control method for a wireless power transmission system, wherein the wireless power transmission system comprises a transmitting end and a receiving end, wherein:

[0006] The transmitting end includes a DC voltage source, a full-bridge inverter circuit, a transmitting end S network, and a transmitting coil connected in sequence; an AC signal is input into the transmitting end S network, and the transmitting coil transmits electrical energy to the receiving coil through the transmitting end S network;

[0007] The receiving end includes a receiving coil, a receiving end compensation network, a high-frequency rectification and filtering circuit, a dual-tube Buck-Boost circuit, and a load RL connected in sequence; a transmission channel is formed between the transmitting coil and the receiving coil, the receiving coil receives the electric energy emitted by the transmitting coil, and the transmission efficiency is stabilized through the receiving end compensation network, the high-frequency rectification and filtering circuit converts the received high-frequency alternating current into direct current, and transmits the electric energy to the load RL through the dual-tube Buck-Boost circuit;

[0008] The composite control of the wireless power transmission system includes coupling coefficient identification, maximum efficiency tracking and constant voltage output control of the wireless power transmission system. The steps are as follows:

[0009] (1) Tracking the maximum efficiency of wireless power transmission systems;

[0010] (1.1) Using the mutual inductance model of the wireless power transmission system, the parameters of the wireless power transmission system working in the resonant state are obtained: input power P in , output power P out , angular frequency ω, transmission efficiency η.

[0011]

[0012] In the formula, is the output fundamental voltage effective value of the full-bridge inverter circuit, E dc is the DC voltage of the DC power supply, It represents the impedance of the S network loop at the transmitting end. represents the impedance of the receiving end S network loop, ω=2πf represents the resonant angular frequency of the wireless power transmission system, f represents the resonant frequency of the wireless power transmission system, M is the mutual inductance value between the transmitting coil and the receiving coil, C p L is the transmitter series compensation capacitor. p is the self-inductance of the transmitting coil, C s L is the compensation capacitor in series with the receiving end. s is the receiving coil self-inductance, R L is the equivalent AC load of the wireless power transmission system, E dc is the DC input voltage, R Lopt is the optimal equivalent AC load, θ is the phase shift angle of the full-bridge inverter, j is an imaginary number, R P is the self-resistance of the transmitting coil, R S Represents the self-resistance of the receiving coil.

[0013] (1.2) Change the Buck-Boost duty cycle so that the equivalent load value of the system at any time is equal to the optimal equivalent load value, and the system will always operate at the maximum efficiency point. The optimal duty cycle D in the maximum efficiency tracking mode is:

[0014]

[0015] R in the formula L It can be done through R L =U out / I out Calculate, where R L , U out and I out are the actual load value, the actual load voltage value, and the actual load current value, respectively. When the system load changes, the duty cycle D of the Buck-Boost circuit is adjusted so that the wireless power transmission system always operates at the maximum efficiency point.

[0016] (2) Identification of coupling coefficient of wireless power transmission system

[0017] The coupling coefficient requires information such as the resonant circuit voltage and current. On this basis, after adding the secondary rectifier and Buck-Boost converter, when both the original and secondary sides resonate, the coupling coefficient k can be solved:

[0018]

[0019] I p Represents the loop current of the transmitting coil, R P It is the self-resistance of the transmitting coil. When identifying the coupling coefficient, set D to 0.5, measure the primary input voltage and current, and then you can get the coupling coefficient.

[0020] (3) A linear active disturbance rejection control constant voltage output method for a wireless power transmission system, comprising the steps of:

[0021] (3.1) Using the linear anti-disturbance technology, the wireless power transfer system is regarded as a first-order single-input-single-output system, which can be expressed as:

[0022]

[0023] Where: y = U out is the output voltage; b is the gain of the wireless power transmission system; is the total disturbance of the system; u is the input control quantity of the system.

[0024] (3.2) According to the output voltage U out Design a first-order linear extended state observer LESO for the output voltage U of the wireless power transfer system out And disturbances are observed; the expression of the first-order linear extended state observer LESO is:

[0025]

[0026] Where: z1 is the output voltage U of the wireless power transmission systemout The estimated value of z2 is the total disturbance estimated value of the wireless power transmission system, and β1 and β2 are the adjustable parameters of ESO. According to the bandwidth setting method, the parameters β1=2ω0, ω0 is the LESO bandwidth.

[0027] (3.3) The control quantity u0 formed by the linear proportional controller can be expressed as:

[0028] u0=k p (U ref -z1)

[0029] In the formula, k p is the proportionality coefficient, U ref Represents the reference value of the set voltage; u0 forms the first-order linear anti-disturbance control quantity u after disturbance compensation:

[0030]

[0031] (3.4) The first-order linear anti-disturbance control variable u is converted into a phase shift angle θ, thereby performing voltage regulation control on the wireless power transmission system.

[0032] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0033] (1) The present invention realizes stable and efficient power transmission of the wireless power transmission system based on linear anti-interference technology.

[0034] (2) The present invention uses maximum efficiency tracking technology to enable the wireless power transmission system to identify the coupling coefficient and maintain the maximum efficiency of power transmission when it is subject to external interference such as changes in the mutual inductance of the coupling coil and the load resistance.

[0035] (3) The present invention takes advantage of the linear active disturbance rejection technology and adopts the first-order LESO to first observe part of the disturbance of the system. Then the linear extended state observer in the active disturbance rejection controller observes other disturbances of the system. It can basically observe the total disturbance of the system and perform feedforward compensation, thereby improving the anti-disturbance capability and robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 An exemplary topological structure diagram of a control loop of a composite control strategy for a wireless power transmission system according to an embodiment of the present invention;

[0037] Figure 2 A mutual inductance model of the SS type wireless power transmission system involved in an embodiment of the present invention;

[0038] Figure 3 A control circuit diagram of a Buck-Boost circuit according to an embodiment of the present invention;

[0039] Figure 4 A linear active disturbance rejection control diagram of a wireless power transmission system according to an embodiment of the present invention;

[0040] Figure 5(a) , 5(b) It is a simulation waveform diagram of output voltage under variable load conditions involved in an embodiment of the present invention;

[0041] Figure 6(a) , 6(b) The output voltage simulation waveform diagram under the condition of variable reference voltage value involved in the embodiment of the present invention;

[0042] Figure 7(a) , 7(b) A simulation waveform diagram of system transmission efficiency under variable load conditions involved in an embodiment of the present invention;

[0043] Figure 8 Shown is a simulation waveform diagram of system transmission efficiency under a variable reference voltage condition according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention is further explained below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0045] This embodiment takes the double S-type wireless power transmission system as an example to build a wireless power transmission system model, and constructs a structure for realizing stable and efficient power transmission according to the wireless power transmission system model. The structure of the composite control loop of the entire wireless power transmission system is as follows: Figure 1 As shown:

[0046] Since the S-type resonant topology is simple and can achieve constant current output and a higher power factor, this embodiment adopts the S-type resonant topology, that is, both the primary and secondary sides adopt the S-type compensation topology. Figure 1 As shown, the system includes a DC source, an inverter circuit, a primary side S resonant network, a secondary side S resonant network, a rectifier circuit, and a filter capacitor C connected in sequence. r , dual-tube Buck-Boost circuit and load R L , the primary side S resonant network includes the resonant inductor L p and resonant capacitor C p , the secondary side S resonant network includes the resonant inductor L s and resonant capacitor C s; To realize the coupling coefficient identification function, in this embodiment, the input voltage of the primary S-resonant network and the input circuit are sampled to calculate the coupling coefficient; To realize the maximum efficiency tracking function, in this embodiment, the duty cycle of the secondary double-tube Buck-Boost circuit is adjusted so that the wireless power transmission system always works at the maximum efficiency point. To realize the voltage regulation function, in this embodiment, the linear anti-disturbance technology is used to adjust the phase shift angle of the inverter circuit for voltage regulation.

[0047] for Figure 1 For the wireless power transmission system with double S-type resonant topology shown in the figure, we design a composite control system to control it. This composite control system includes: a voltage detector, a current detector, a first-order linear extended state observer LESO, a linear active disturbance rejection controller LADRC and a PWM drive circuit.

[0048] For the wireless power transmission system with the double S-type resonant topology, the specific process of compound control is as follows:

[0049] (1) Tracking the maximum efficiency of wireless power transmission systems;

[0050] (1.1) Using the mutual inductance model of the wireless power transmission system, the parameters of the wireless power transmission system working in the resonant state are obtained: input power P in , output power P out , angular frequency ω, transmission efficiency η.

[0051]

[0052] In the formula, is the output fundamental voltage effective value of the full-bridge inverter circuit, It represents the impedance of the S network loop at the transmitting end. represents the impedance of the receiving end S network loop, ω=2πf represents the resonant angular frequency of the wireless power transmission system, f represents the resonant frequency of the wireless power transmission system, M is the mutual inductance value between the transmitting coil and the receiving coil, C p L is the transmitter series compensation capacitor. p is the self-inductance of the transmitting coil, C s L is the compensation capacitor in series with the receiving end. s is the receiving coil self-inductance, R L is the equivalent AC load of the wireless power transmission system, E dc is the DC input voltage, R Lopt is the optimal equivalent AC load, θ is the phase shift angle of the full-bridge inverter, E dc is the DC voltage of the DC power supply, R S Represents the self-resistance of the receiving coil.

[0053] (1.2) Change the Buck-Boost duty cycle so that the equivalent load value of the system at any time is equal to the optimal equivalent load value, and the system will always operate at the maximum efficiency point. The optimal duty cycle D in the maximum efficiency tracking mode is:

[0054]

[0055] R in the formula L It can be done through R L =U out / I out Calculate, where R L , U out and I out They are the actual load value, actual load voltage value and actual load current value respectively. Figure 1 The actual output voltage U of the wireless power transmission system shown out ; Detected by current detector Figure 1 The actual output current I of the wireless power transmission system shown out , when the system load changes, the duty cycle D of the Buck-Boost circuit is adjusted so that the wireless power transmission system always operates at the maximum efficiency point.

[0056] (2) Identification of coupling coefficient of wireless power transmission system

[0057] Detected by current sensor Figure 2 The resonant current of the primary S resonant network is shown; it is detected by the voltage detector Figure 2 The input voltage of the primary S resonant network is shown. After adding the secondary rectifier and Buck-Boost converter, when both the primary and secondary sides resonate, the coupling coefficient k can be solved:

[0058]

[0059] I p , R p They represent the loop current of the transmitting coil and the self-resistance of the transmitting coil respectively. When identifying the coupling coefficient, set D to 0.5, measure the primary input voltage and current, and then you can get the coupling coefficient.

[0060] (3) A linear active disturbance rejection control constant voltage output method for a wireless power transmission system, comprising the steps of:

[0061] (3.1) Using the linear anti-disturbance technology, the wireless power transfer system is regarded as a first-order single-input-single-output system, which can be expressed as:

[0062]

[0063] Where: y = Uout is the output voltage; b is the gain of the wireless power transmission system; is the total disturbance of the system; u is the input control quantity of the system.

[0064] (3.2) Collect the load voltage U using the voltage collector out , according to U out Design of a first-order linear extended state observer LESO for the output voltage U of the wireless power transfer system out And disturbances are observed; the expression of the first-order linear extended state observer LESO is:

[0065]

[0066] Where: z1 is the output voltage U of the wireless power transmission system out The estimated value of z2 is the total disturbance estimated value of the wireless power transmission system, and β1 and β2 are the adjustable parameters of ESO. According to the bandwidth setting method, the parameters β1=2ω0, ω0 is the LESO bandwidth.

[0067] (3.3) The control quantity u0 formed by the linear proportional controller can be expressed as:

[0068] u0=k p (U ref -z1)

[0069] Where U ref Indicates the reference value of the set voltage, k p is the proportional coefficient; u0 is the control quantity u formed by disturbance compensation:

[0070]

[0071] (3.4) The first-order linear anti-disturbance control variable u is converted into a phase shift angle θ, thereby performing voltage regulation control on the wireless power transmission system.

[0072] The following simulation experiment is carried out on the technical solution described in this embodiment to illustrate the technical effect of this embodiment.

[0073] Figure 5 is a simulation waveform of the output voltage under variable load conditions, with the output reference voltage set to 20V and the simulation time to 0.4s. When the time is set to 0.2s, the load changes from 15Ω to 20Ω. The two curves in the figure represent the output voltage tracking waveform of the ADRC and the output voltage tracking waveform of the traditional PI controller. By comparing the two, it can be seen that at the beginning of operation and during load switching, the output voltage waveform of the traditional PI controller has an overshoot of 6%, while the ADRC has no overshoot. The traditional PI control system reaches the reference voltage value after approximately 0.125s and 0.325s, respectively, while the ADRC reaches the reference voltage value after approximately 0.1s and 0.3s, respectively. It can be seen that the ADRC method has a shorter adjustment time and is more advantageous.

[0074] Figure 6 is a simulation waveform of the output voltage under the condition of variable reference value. According to theoretical analysis, the closed-loop control system has the characteristics of suppressing external interference. The initial input voltage is 20V at 0s, and 5V interference is added at 0.2s. At the beginning of operation, the traditional PI control system reaches the reference voltage value in about 0.125s, and the overshoot is about 6%; while the self-disturbance rejection control system reaches the reference voltage value in about 0.075s, and there is no overshoot; during the reference value switching process, both have no overshoot, the traditional PI control system reaches the reference voltage value in about 0.1s; and the self-disturbance rejection control system reaches the reference voltage value in about 0.075s. It can be seen that the self-disturbance rejection controller can track the stable value faster.

[0075] Figure 7 is a simulation waveform of the system transmission efficiency under variable load conditions; the simulation time is set to 0.4s. When the time is set to 0.2s, the load changes from 20Ω to 15Ω. The two curves in the figure represent the transmission efficiency when the maximum efficiency tracking control strategy is adopted and the transmission efficiency when the inefficiency tracking control is adopted. Under the inefficiency tracking condition, when the load is 20Ω and 15Ω, the system transmission efficiency is 82.5% and 85.5% respectively, while the transmission efficiency of the system using the efficiency tracking control can reach 90%.

[0076] Figure 8 The simulation waveform of the system transmission efficiency under the condition of changing reference voltage; the simulation time is set to 0.4s. When the time is set to 0.2s, the reference voltage changes from 20V to 15V, and efficiency tracking control is adopted. After the reference voltage changes, the system transmission efficiency can reach 90%.

[0077] By adopting the technical solutions provided in the above embodiments, the present invention has at least the following technical effects:

[0078] The coupling coefficient identification enables the coupling coefficient of the system to be obtained quickly and accurately when the mutual inductance of the system changes.

[0079] Maximum efficiency tracking allows the system to always operate at the maximum efficiency point, making power transmission more efficient.

[0080] The linear anti-disturbance technology enables the system to quickly track the output voltage when the load sense and reference value of the system fluctuate, reducing the system's adjustment time, overshoot and steady-state error, and improving the robustness of the system.

[0081] The composite method for wireless power transmission system proposed in the present invention is universal, that is, the method is not only applicable to the double S-type wireless power transmission system proposed in this embodiment, but also applicable to the control of wireless power transmission systems with other topological structures such as SP and PP.

[0082] The above embodiments, especially any "preferred" embodiments, are possible examples of implementation, and are only proposed for a clear understanding of the principles of the present invention. Many changes and modifications may be made to the above embodiments without substantially departing from the spirit and principles of the technology described in the present invention, and these changes and modifications should also be considered as the scope of protection of the present invention.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite control method for a wireless power transmission system, characterized in that: The steps include: (1) Tracking the maximum efficiency of wireless power transmission systems; (2) Identify the coupling coefficient of the wireless power transmission system; (3) Linear anti-disturbance control constant voltage output method for wireless power transmission system.

2. The composite control method of the wireless power transmission system according to claim 1, characterized in that: The wireless power transmission system comprises a transmitting end and a receiving end, wherein: The transmitting end includes a DC voltage source, a full-bridge inverter circuit, a transmitting end S network, and a transmitting coil connected in sequence; an AC signal is input into the transmitting end S network, and the transmitting coil transmits electrical energy to the receiving coil through the transmitting end S network; The receiving end includes a receiving coil, a receiving end compensation network, a high-frequency rectification and filtering circuit, a dual-tube Buck-Boost circuit, and a load RL connected in sequence; a transmission channel is formed between the transmitting coil and the receiving coil, the receiving coil receives the electric energy emitted by the transmitting coil, and the transmission efficiency is stabilized through the receiving end compensation network, the high-frequency rectification and filtering circuit converts the received high-frequency alternating current into direct current, and transmits the electric energy to the load RL through the dual-tube Buck-Boost circuit; The composite control of the wireless power transmission system includes coupling coefficient identification, maximum efficiency tracking and constant voltage output control of the wireless power transmission system.

3. The composite control method of the wireless power transmission system according to claim 1, characterized in that: Tracking the maximum efficiency of wireless power transfer systems, including: (1.1) Using the mutual inductance model of the wireless power transmission system, the parameters of the wireless power transmission system operating in a resonant state are obtained, including: input power, output power, angular frequency, and transmission efficiency; (1.2) By changing the Buck-Boost duty cycle so that the equivalent load value of the system at any time is equal to the optimal equivalent load value, the system will always operate at the maximum efficiency point; when the system load changes, adjust the duty cycle of the Buck-Boost circuit so that the wireless power transmission system always operates at the maximum efficiency point.

4. The composite control method of the wireless power transmission system according to claim 1, characterized in that: In the identification of the coupling coefficient of the wireless power transmission system, the coupling coefficient requires the voltage and current information of the resonant circuit. After adding the rectifier and Buck-Boost converter on the secondary side, the coupling coefficient can be solved when the original and secondary sides resonate.

5. The composite control method of the wireless power transmission system according to claim 1, characterized in that: A linear auto-disturbance rejection control constant voltage output method for a wireless power transmission system comprises the following steps: (3.1) The wireless power transfer system is regarded as a first-order single-input-single-output system using linear active disturbance rejection technology; (3.2) Designing a first-order linear extended state observer LESO according to the output voltage to observe the output voltage and disturbance of the wireless power transmission system; (3.3) Obtain the control quantity formed by the linear proportional controller, and the control quantity forms a first-order linear anti-disturbance control quantity after disturbance compensation; (3.4) The first-order linear anti-disturbance control quantity is converted into a phase shift angle, so as to perform voltage regulation control on the wireless power transmission system.

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