Anti-interference system and control method based on wireless power transmission of BUCK circuit

Abstract

The present invention relates to wireless power transmission technology, and more specifically to an anti-interference system and method for a buck circuit wireless power transmission system. The method comprises establishing a buck circuit mathematical model; designing a model predictive control method based on the system discrete mathematical model, utilizing a desired output sequence and system disturbance for feedforward compensation, wherein the feedback compensation is composed of the state quantities of the system at the current moment and the previous moment, and a control increment sequence is generated; designing a relatively simple mathematical model based on the system order, and designing a disturbance observer, treating all system uncertainties as disturbances for estimation and compensation; and feeding back the estimated value of the disturbance observer to a model predictive controller for rolling optimization, thereby enhancing the robustness of the wireless power transmission system. Under conditions of system perturbation, parameter uncertainty, and load mutation, the control method can better control the system, improve its response speed and robustness, and improve the transmission efficiency of the wireless power transmission system.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless power transmission, and in particular relates to an anti-interference system and a control method for wireless power transmission based on a BUCK circuit. Background Art

[0002] Wireless Power Transfer (WPT) technology has a wide range of applications due to its reliability, safety, and flexibility. Based on the principle of electromagnetic induction, this technology enables non-physical contact power transmission from power supply equipment to power-consuming equipment. Compared with traditional contact power supply methods, it avoids shortcomings such as poor contact, leakage risks, and poor environmental adaptability. It is not limited by harsh external environments and is widely used in some special scenarios, such as electric vehicles, underwater power supply, and rail transit.

[0003] WPT systems are high-order nonlinear systems, making their mathematical models difficult to accurately establish. Therefore, modeling and analyzing WPT systems with downstream DC / DC circuits facilitates the design of simplified control strategies. Buck circuits, a commonly used circuit topology in WPT systems, have a direct impact on wireless power transmission efficiency. Due to the complex application scenarios of wireless power transmission technology, system parameters are easily affected by the environment. In practical applications, sudden load changes can cause the output voltage of the Buck circuit to deviate from the set value. Traditional control methods struggle to achieve system outputs that meet practical requirements, often resulting in sluggish closed-loop control system response and side effects such as oscillation. However, in some dynamic wireless charging scenarios, the system must quickly reach rated power. Therefore, more effective Buck circuit control methods are needed to enable the system to quickly enter steady state and quickly recover from it in the presence of unknown external disturbances, thereby optimizing the system's dynamic performance.

[0004] Model Predictive Control (MPC) has attracted widespread attention in the power electronics field due to its ability to handle constraints on state variables, manipulated variables, and output variables. MPC is a powerful technology that can meet the high performance and efficiency requirements of today's power converters. However, due to the difficulty in establishing accurate models for wireless power transmission systems and their susceptibility to environmental influences in some specific application scenarios, the performance of predictive control has deteriorated, reducing system robustness. Summary of the Invention

[0005] In view of the problems existing in the background technology, the present invention provides an output voltage control method of a wireless power transmission system based on a disturbance observer and model predictive control.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: an anti-interference system based on wireless power transmission of BUCK circuit, the system includes: Buck main circuit and control circuit, Buck main circuit includes Buck circuit input voltage U1, switch tube V g , freewheeling diode D, inductor L, capacitor C1 and resistor R; the control circuit includes a disturbance observer and a model predictive controller; the output of the control circuit is connected to the switch tube V g The gate of the Buck circuit input voltage U1 positive electrode and the switch tube V g The drain is connected to the switch tube V g The source is connected to the inductor L and the cathode of the freewheeling diode D. The other end of the inductor L is connected to the capacitor C1 and the resistor R. The other end of the capacitor C1, the other end of the resistor R and the freewheeling diode V g The positive terminal is connected to the negative terminal of U1.

[0007] A method for controlling an anti-interference system based on wireless power transmission using a buck circuit comprises the following steps:

[0008] Step 1: Equivalent the input end of the WPT system's post-stage Buck link to an ideal constant current source to obtain the equivalent circuit topology of the Buck converter.

[0009] Step 2: Establish an average switch model in the continuous conduction mode;

[0010] Step 3: Set the prediction time domain to N p , the control time domain is N m , and generally N m ≤N p , derive the system prediction equation;

[0011] Step 4: Select the objective function and obtain the control increment;

[0012] Step 5: Take the low-pass filter in the disturbance observer as a second-order low-pass filter:

[0013]

[0014] Where T is the filtering time of the filter;

[0015] Step 6: Use the second-order pure differential link of the Buck circuit nominal model Design a disturbance observer and obtain the estimated value of the disturbance observer on the system

[0016] Step 7: The disturbance observer estimates the disturbance to the system As the control quantity d(k), the final control increment is obtained, and then sent to the modulation module to obtain the driving signal of the switch tube, so that the control system can obtain a stable output voltage.

[0017] In the above-mentioned anti-interference system control method based on wireless power transmission of the BUCK circuit, the implementation of step 2 includes:

[0018] Establish an average switch model under continuous conduction mode;

[0019]

[0020] Among them, U o is the system output voltage, U1 is the voltage across the capacitor filter C0, i L is the inductor L current, u is the switching function, and the expression is: Where T is the switching period and D is the duty cycle;

[0021] Define output voltage error x1 = U ref -U o , output error change rate Among them, U ref is the output voltage setting value, the second-order state equation of the system is:

[0022]

[0023] Rewrite it as follows:

[0024]

[0025] Where, C c =[1 0];

[0026] By discretizing it, the discrete state equation of the system is obtained as follows:

[0027]

[0028] The transformation relationship between discrete-time model and continuous-time model is as follows:

[0029]

[0030] Where, T s is the system sampling time;

[0031] Convert the discrete state equation into incremental form:

[0032]

[0033] Where,

[0034] In the above-mentioned anti-interference system control method based on wireless power transmission of the buck circuit, the implementation of step 3 includes:

[0035] Assume Δu(k+i)=0,i=N m ,N m +1,…,N p -1, Δd(k+i)=0,i=1,2,…,N p -1; Use the current measurement value of the system to predict the future state of the system, and define N p Step-by-step prediction output vector N m The step input vector is

[0036] The output prediction equation is:

[0037] Y p (k+1|k)=S x Δx(k)+Iy c (k)+S d Δd(k)+S u ΔU(k);

[0038] Where,

[0039]

[0040]

[0041] In the above-mentioned anti-interference system control method based on wireless power transmission of the buck circuit, the implementation of step 4 includes:

[0042] Step 4.1, select the objective function:

[0043]

[0044] Where, is the weighting factor for the jth component error of the predictive control output at prediction time i, is the weighting factor for the jth component of the control increment at the prediction time i, and r(k+i) is the reference input sequence component;

[0045] Step 4.2, the control increment expression is:

[0046] Δu(k)=K mpc E p (k+1|k)

[0047] Where, the predictive control gain is The weighting matrix is

[0048] y c (k) = C cSubstituting x(k) and Δx(k)=x(k)-x(k-1) into the control increment expression, we obtain:

[0049] Δu(k)=K mpc R(k+1)-K mpc (S x +IC c )x(k)-K mpc S d Δd(k)+K mpc S x x(k-1)

[0050] Where, the reference input sequence is

[0051] In the above-mentioned anti-interference system control method based on wireless power transmission of the buck circuit, the implementation of step 6 includes:

[0052] All other system terms are considered as system disturbances, estimated and fed back to the model predictive controller; the state space equation of the Buck circuit is:

[0053]

[0054] Where x1 is the output voltage of the Buck circuit, u1 is the system input, and the system disturbance is

[0055] Equivalently transfer the system disturbance to the output terminal, and assume that the total disturbance of the system is:

[0056] D l (k) = D m (k)+D e (k)

[0057] Where D m (k)=[G p (z)-G n (z)][u1(k)+D(k)] is the internal disturbance of the system, D e (k)=D(k)G p (z) is the external disturbance of the system;

[0058] The output voltage transfer function is:

[0059] Y(k)=G n (z)u1(k)+D l (k).

[0060] The disturbance observer estimates the system disturbance as:

[0061]

[0062] Arranged:

[0063]

[0064] Compared to existing technologies, this invention proposes a method for controlling the output voltage of a wireless power transmission system based on a disturbance observer and model predictive control. In the presence of sudden load changes, the total disturbance is estimated and compensated in real time, thereby achieving closed-loop control of the WPT system and improving the system's dynamic characteristics. To address the impact of load changes on predictive control in WPT systems, a disturbance observer is introduced, incorporating the disturbance estimate into the rolling optimization process of the MPC (Multi-Purpose Programming) algorithm, thereby improving the performance of model predictive control and effectively enhancing the response speed and robustness of the WPT system. This control method can effectively control the system under conditions of system perturbations, parameter uncertainty, and sudden load changes, while also improving its response speed and robustness and enhancing the transmission efficiency of the wireless power transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is a circuit structure diagram of an anti-interference system for wireless power transmission based on a Buck circuit according to an embodiment of the present invention;

[0066] Figure 2 is the equivalent circuit topology of the Buck converter;

[0067] Figure 3 This is the block diagram of the model predictive control system based on disturbance observer;

[0068] Figure 4 This is the equivalent control block diagram of the disturbance observer;

[0069] Figure 5 This is a comparison diagram of system simulation experiment results. DETAILED DESCRIPTION

[0070] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0071] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0072] The present invention will be further described below with reference to specific examples, but they are not intended to limit the present invention.

[0073] The WPT system is a complex, nonlinear, high-order system, making controller design for the entire system extremely difficult. This embodiment only controls the output voltage of the Buck circuit in the latter stage, greatly simplifying system modeling and controller design. This embodiment establishes a mathematical model of the Buck circuit and designs a model predictive control method based on the system's discrete mathematical model. Feedforward compensation is performed using the desired output sequence and system disturbances. Feedback compensation consists of the system's current and previous state variables, and a control increment sequence is generated. A relatively simple mathematical model is designed based on the system order, and a disturbance observer is designed. System uncertainties are treated as disturbances for estimation and compensation. The disturbance observer's estimated value is fed back to the model predictive controller for rolling optimization, making the wireless power transmission system more robust. This control method can effectively control the system under conditions of system perturbation, parameter uncertainty, and sudden load changes, improving its response speed and robustness, and thus the transmission efficiency of the wireless power transmission system.

[0074] This embodiment is realized by the following technical solution: an anti-interference system of a wireless power transmission system of a BUCK circuit, including a Buck main circuit and a control circuit. The Buck main circuit includes a Buck circuit input voltage U1, a switch tube V g , freewheeling diode D, inductor L, capacitor C and resistor R. The control circuit includes a disturbance observer and a model predictive controller.

[0075] like Figure 1 The figure shows the circuit structure of the anti-interference system of the wireless power transmission system based on the Buck circuit. The WPT system uses a DD-type coil, which has better lateral offset capability. The resonant network topology is SS-type. The energy is transferred to the secondary side through the primary side compensation network. The secondary side compensation network is rectified by a full bridge and then output through the Buck circuit. There is a coupling relationship between the primary and secondary side coils, and energy transmission without physical connection is achieved through a high-frequency alternating frequency magnetic field. in The DC power supply of the system, four switch tubes Q1~Q4 form a full-bridge inverter circuit, C p 、L p and C s 、L s The SS type resonant network is formed, and the four diodes D1 to D4 form a full-bridge rectifier circuit. C0 is used as a capacitor filter. The secondary side voltage after rectification is U1, and the switch tube V g , freewheeling diode D, inductor L, capacitor C1 and load R constitute the Buck circuit.

[0076] The output of the control circuit is connected to the switch tube V g The gate of U1 and the positive electrode of the switch tube V g The drain is connected to the switch tube V gThe source is connected to the inductor L and the cathode of the freewheeling diode D. The other end of the inductor L is connected to the capacitor C1 and the resistor R. The other end of the capacitor C1, the other end of the resistor R and the freewheeling diode V g The positive terminal is connected to the negative terminal of U1. The MPC output value and the actual load voltage output value serve as the two input signals of the disturbance observer. The system disturbance estimated by the disturbance observer is fed back to the MPC for rolling optimization to obtain the control increment. This is sent to the modulation module to obtain the drive signal of the switching tube, thereby controlling the stable output of the system.

[0077] like Figure 3 As shown in the figure, it is a system control block diagram based on disturbance observer and MPC control, r(k) is the output voltage setting value, u1(k) is the control signal, D(k) is the system disturbance, G p (z) is the actual model of the controlled object, y(k) is the system output, G n (z) is the nominal model of the controlled object, Q(z) is the low-pass filter, The system disturbance estimated by the disturbance observer.

[0078] S1,i r is the rectified current output by the secondary coil. The magnitude of this current is only related to the primary output voltage amplitude and the coil coupling coefficient. Therefore, the input end of the post-stage Buck link of the WPT system is equivalent to an ideal constant current source, and the equivalent circuit topology of the Buck converter is obtained as follows: Figure 2 As shown in the figure, U1 is the voltage across the filter capacitor C0, i L is the inductor L current, by adjusting the switch tube V g The duty cycle controls the load output voltage U o .

[0079] S2, the Buck circuit is studied in the continuous current conduction mode. When the switch is closed, the Buck circuit model is: When the switch is disconnected, the model is: The average switching model is obtained as:

[0080]

[0081] Where u is the switching function, the expression is:

[0082]

[0083] Where T is the switching period and D is the duty cycle.

[0084] Define output voltage error x1 = U ref -U o , output error change rate Among them, Uref is the output voltage setting value, the second-order state equation of the system is:

[0085]

[0086] Further rewritten as follows:

[0087]

[0088] Where, C c =[1 0].

[0089] By discretizing it, the discrete state equation of the system is obtained as follows:

[0090]

[0091] The discrete-time model and the continuous-time model have the following transformation relationship:

[0092]

[0093] Where, T s is the system sampling time.

[0094] Convert the discrete state equation into incremental form:

[0095]

[0096] Where,

[0097] S3, set the prediction time domain to N p , the control time domain is N m , and generally N m ≤N p To derive the system prediction equation, assume that Δu(k+i)=0,i=N m ,N m +1,…,N p -1; Δd(k+i)=0,i=1,2,…,N p -1.

[0098] At this point, the system's current measurement value can be used to predict the system's future state:

[0099]

[0100] The controlled output can also be predicted by the output equation:

[0101]

[0102] Define N p The step-by-step prediction output vector is N m The step input vector is Then the output prediction equation is:

[0103] Y p (k+1|k)=S x Δx(k)+Iy c (k)+S d Δd(k)+S u ΔU(k)

[0104] Where,

[0105]

[0106]

[0107] S4, select the following objective function:

[0108]

[0109] Where, is the weighting factor for the jth component error of the predictive control output at prediction time i, is the weighting factor for the jth component of the control increment at prediction time i, and r(k+i) is the reference input sequence component.

[0110] The control increment expression is:

[0111] Δu(k)=K mpc E p (k+1|k)

[0112] Where, the predictive control gain is The weighting matrix is

[0113] y c (k) = C c Substituting x(k) and Δx(k)=x(k)-x(k-1) into the equation, we can derive the control increment:

[0114] Δu(k)=K mpc R(k+1)-K mpc (S x +IC c )x(k)-K mpc S d Δd(k)+K mpc S x x(k-1)

[0115] Where, the reference input sequence is

[0116] S5. Since the ideal model of the Buck circuit is a second-order system, the low-pass filter in the designed disturbance observer is usually a second-order one:

[0117]

[0118] Where T is the filtering time of the filter.

[0119] S6, the nominal model of the Buck circuit is a second-order pure differential link Design a disturbance observer. Treat all other system terms as system disturbances, estimate them, and feed them back to the forward channel for disturbance compensation. At this point, the state space equation of the Buck circuit is:

[0120]

[0121] Where x1 is the output voltage of the Buck circuit, u1 is the system input, and the system disturbance is

[0122] Will Figure 2 In the system control block diagram shown, the system disturbance is equivalent to the output end, and the system lumped disturbance is assumed to be:

[0123] D l (k) = D m (k)+D e (k)

[0124] Where D m (k)=[G p (z)-G n (z)][u1(k)+D(k)] is the internal disturbance of the system, D e (k)=D(k)G p (z) is the external disturbance of the system.

[0125] Depend on Figure 4 The equivalent control block diagram of the disturbance observer is shown in FIG. 1 , and the output voltage transfer function is obtained as follows:

[0126] Y(k)=G n (z)u1(k)+D l (k)

[0127] The disturbance observer estimates the system disturbance:

[0128]

[0129] Arranging the above formula, we get:

[0130]

[0131] Assume that the observation error of the disturbance observer is The expression is:

[0132]

[0133] According to the final value theorem, we can get:

[0134]

[0135] Obviously, when the low-pass filter Q(z) parameter is 1, the observation error of the disturbance observer can be made zero. From the above calculations, it can be seen that the designed disturbance observer can estimate and compensate for the disturbances generated by the system to ensure the stability of the system output.

[0136] S7, the disturbance observer estimates the system disturbance As the control quantity d(k), the final control increment can be obtained, and then sent to the modulation module to obtain the driving signal of the switch tube, thereby controlling the system to obtain a stable output voltage.

[0137] To verify the effectiveness of this control strategy, this example built a wireless power transmission system model in Matlab / Simulink. The MPC+DOB composite control method was applied to control the output voltage of the buck link in the latter stage of the WPT system circuit. The total system disturbance was estimated and compensated in real time. The control effects of the MPC+DOB control method on the system output were compared with those of the MPC control method.

[0138] The SS type WPT system topology is adopted, the resonant frequency is 100kHz, the DC input voltage is 24V, and the system parameters are shown in Table 1.

[0139] Table 1 WPT system design parameters

[0140]

[0141]

[0142] Figure 5 The figure shows the comparison results of the system simulation experiment. At 0.5s, the secondary side output load suddenly changes from 20Ω to 40Ω. It can be seen that the MPC+DOB control method has a faster response speed, stronger disturbance suppression capability and control performance. This control method achieves better anti-interference characteristics than the MPC method in both steady state and transient state, improving the response speed and robustness of the WPT system.

[0143] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the present invention specification should be included in the protection scope of the present invention.

Claims

1. An anti-interference control method for wireless power transmission based on a BUCK circuit. The control method is implemented based on the following system. The system includes a Buck main circuit and a control circuit. The Buck main circuit includes a Buck circuit input voltage U1, a switch tube V g , freewheeling diode D, inductor L, capacitor C1 and resistor R; the control circuit includes a disturbance observer and a model predictive controller; the output of the control circuit is connected to the switch tube V g The gate of the Buck circuit input voltage U1 positive electrode and the switch tube V g The drain is connected to the switch tube V g The source is connected to the inductor L and the cathode of the freewheeling diode D. The other end of the inductor L is connected to the capacitor C1 and the resistor R. The other end of the capacitor C1, the other end of the resistor R and the freewheeling diode V g The positive electrode is connected to the negative electrode of U1; its characteristics are: The control method comprises the following steps: Step 1: Equivalent the input end of the WPT system's post-stage Buck link to an ideal constant current source to obtain the equivalent circuit topology of the Buck converter. Step 2: Establish an average switch model in the continuous conduction mode; Step 3: Set the prediction time domain to N p , the control time domain is N m , and generally N m ≤N p , derive the system prediction equation; Step 4: Select the objective function and obtain the control increment; Step 5: Take the low-pass filter in the disturbance observer as a second-order low-pass filter: Where T is the filtering time of the filter; Step 6: Use the second-order pure differential link of the Buck circuit nominal model Design a disturbance observer and obtain the estimated value of the disturbance observer on the system The specific steps are as follows: All other system terms are considered as system disturbances, estimated and fed back to the model predictive controller; the state space equation of the Buck circuit is: Where, state x1 is the Buck circuit output voltage error x1=U ref -U o , u1 is the system input, system disturbance Equivalently transfer the system disturbance to the output terminal, and assume that the total disturbance of the system is: D l (k)=D m (k)+D e (k) Where D m (k)=[G p (z)-G n (z)][u1(k)+D(k)] is the internal disturbance of the system, D e (k)=D(k)G p (z) is the external disturbance of the system; The output voltage transfer function is: Y(k)=G n (z)u1(k)+D l (k) The disturbance observer estimates the system disturbance as: Arranged: Step 7: The disturbance observer estimates the disturbance to the system As the control quantity d(k), the final control increment is obtained, and then sent to the modulation module to obtain the driving signal of the switch tube, so that the control system can obtain a stable output voltage.

2. The anti-interference system control method based on BUCK circuit wireless power transmission according to claim 1, characterized in that: The implementation of step 2 includes: Establish an average switch model under continuous conduction mode; Among them, U o is the system output voltage, i L is the inductor L current, u is the switching function, and the expression is: Where T is the switching period and D is the duty cycle; Define output voltage error x1 = U ref -U o , output error change rate Among them, U ref is the output voltage setting value, the second-order state equation of the system is: Rewrite it as follows: Where, C c =[1 0]; By discretizing it, the discrete state equation of the system is obtained as follows: The transformation relationship between discrete-time model and continuous-time model is as follows: Where, T s is the system sampling time; Convert the discrete state equation into incremental form: Where, 3. The anti-interference system control method based on BUCK circuit wireless power transmission according to claim 2, characterized in that: The implementation of step 3 includes: Assume Δu(k+i)=0,i=N m ,N m +1,…,N p -1, Δd(k+i)=0,i=1,2,…,N p -1; Use the current measurement value of the system to predict the future state of the system, and define N p Step-by-step prediction output vector N m The step input vector is The output prediction equation is: Y p (k+1|k)=S x Δx(k)+Ιy c (k)+S d Δd(k)+S u ΔU(k); Where, 4. The anti-interference system control method based on BUCK circuit wireless power transmission according to claim 3, characterized in that: The implementation of step 4 includes: Step 4.1, select the objective function: Where, is the weighting factor for the jth component error of the predictive control output at prediction time i, is the weighting factor for the jth component of the control increment at the prediction time i, and r(k+i) is the reference input sequence component; Step 4.2, the control increment expression is: Δu(k)=K mpc E p (k+1|k) Where, the predictive control gain is The weighting matrix is y c (k) = C c Substituting x(k) and Δx(k)=x(k)-x(k-1) into the control increment expression, we obtain: Δu(k)=K mpc R(k+1)-K mpc (S x +IC c )x(k)-K mpc S d Δd(k)+K mpc S x x(k-1) Where, the reference input sequence is

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