A Passive Control Method Based on Buck-Boost Converter

Abstract

The present invention relates to a passive control method based on a Buck-Boost converter, specifically comprising: in a continuous conduction state of the inductor current, a mathematical model of the Buck-Boost converter is established to obtain a system port-controlled Hamiltonian model, based on the system port-controlled Hamiltonian model, starting from energy shaping and damping injection, and combining with an integral link, optimizing the outer loop controller of the traditional cascade and damping configuration, the method of the present invention applies the Buck-Boost converter, establishes a port-controlled Hamiltonian model, designs a cascade damping configuration passive controller, focuses on using the improved fal function of nonlinear feedback control in the inner loop control, and the principle of input-output side power balance to compensate for the expected value of the inductor current of the inner loop control. Through the designed controller, no matter how the resistance value of the resistive load and the constant power load resistance value change, whether there is an external disturbance, the system can operate stably and accurately output to the expected value.

Description

Technical Field

[0001] The invention belongs to the technical field of automatic control, and in particular relates to a passivity control method based on a Buck-Boost converter. Background Art

[0002] A DC-DC converter is a power electronic device that realizes the mutual conversion of electric energy by controlling the duty cycle of switching devices. There are many forms of topological structures. The commonly used topological structure is the Buck-Boost converter. This converter has gradually become a research hotspot due to its simple structure, stable operation, easy control, and fast conversion efficiency. The commonly used control schemes for this are divided into linear control algorithms and nonlinear control algorithms. The linear control algorithm is linearized near the equilibrium point and achieves stable output in its neighborhood; however, there is still room for optimization of dynamic characteristics such as the adjustment time and overshoot of the nonlinear system; and for the situation of constant power load, the stable operation of the system cannot be guaranteed. Therefore, for nonlinear systems, nonlinear control algorithms are mostly used. Such as: sliding mode control, passive control, adaptive control, anti-disturbance control, and backstepping control. Among them, passive control is a global control algorithm based on energy balance. The core of its design principle is to make the impedance part of the system present positive impedance characteristics through energy shaping and damping injection, that is, the system is positive definite; the relationship between the positive definiteness and passivity of the system is proved according to the strict positive real lemma (KYP), and then the local invariance theorem and Lyapunov's second method are used to prove that the passive system is stable.

[0003] However, the existing passive control systems applied to constant power load systems cannot take into account both overshoot and rapidity, and it is difficult to achieve stable output while meeting the requirements of fast response. Summary of the invention

[0004] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the objects of the present invention is to at least solve one or more of the above-mentioned problems in the prior art. In other words, one of the objects of the present invention is to provide a passive control method based on a Buck-Boost converter that meets one or more of the above-mentioned requirements.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A passivity control method based on a Buck-Boost converter, specifically comprising:

[0007] In the continuous conduction state of the inductor current, the mathematical model of the Buck-Boost converter is established, and the system port controlled Hamiltonian model is obtained;

[0008] Based on the system port controlled Hamiltonian model, starting from energy shaping and damping injection, and combining with the integral link, the outer loop controller of the traditional cascade and damping configuration is optimized;

[0009] Using the inner loop controller, the desired current of the system is redefined based on nonlinear feedback control to further enhance the dynamic performance of the system.

[0010] As a preferred implementation, the outer loop controller for optimizing the traditional cascade and damping configuration specifically includes:

[0011] The traditional passive control law is combined with the integral link to optimize the outer loop controller of the traditional cascade and damping configuration.

[0012] As a preferred implementation, an inner loop controller is used to redefine the desired current of the system based on nonlinear feedback control. The specific usage method is:

[0013] The desired current of the system is redefined by improving the fal function based on nonlinear feedback control.

[0014] As a further preferred implementation, the inner loop controller uses the improved nonlinear feedback as the expected value, thereby redefining the expected current of the system.

[0015] As a preferred implementation, the control parameters of the Buck-Boost converter are as follows:

[0016]

[0017] Where e is the difference between the output voltage and the expected voltage. According to the experiment, the parameters β = 5; α = 0.5; δ = 0.01, k i The value is 0.8, A∈(1,π), and B is less than 1. V dis is the voltage across the parasitic resistance V dis =-(R L +(1-u)*R VD +u*R VT )*x 1 ; R L , R VD and R VT They are the inductor, freewheeling diode and internal resistance of MOSFET respectively; the tan function speeds up the system convergence time when the error is large, and the convergence is smoother than the traditional function.

[0018] As a preferred implementation, the fall function of the Buck-Boost converter is specifically:

[0019]

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method of the present invention applies a Buck-Boost converter, establishes a port-controlled Hamiltonian model, designs a cascade damping configuration passive controller, focuses on utilizing the principle of input-output side power balance in inner-loop control, compensates for the expected value of the inductor current of the inner-loop control, and then optimizes the passive outer-loop control through an integral link. No matter how the resistance value of the resistive load and the resistance value of the constant power load change, and whether there is an external disturbance, the system can operate stably and accurately output to the expected value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the structure of a Buck-Boost converter based on passivity control proposed in the present invention;

[0023] Figure 2 It is a schematic diagram of the influence of the relationship between the resistance value of constant power load and resistive load on the system under open-loop control;

[0024] Figure 3 This is a comparison diagram of the errors between the inner loop controller of the present invention and the traditional inner loop controller;

[0025] Figure 4 An output voltage diagram of the controller of the present invention and other controllers;

[0026] Figure 5 It is the phase diagram of the controller of the present invention. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0028] In the following introduction, multiple embodiments of the present application are provided, and different embodiments may be replaced or combined, so the present application may also be considered to include all possible combinations of the same and / or different embodiments described. Therefore, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present application should also be considered to include embodiments containing one or more of A, B, C, and D, all other possible combinations, even though the embodiment may not be clearly described in the following text.

[0029] The following description provides examples and does not limit the scope, applicability or examples set forth in the claims. Changes may be made to the functions and arrangements of the elements described without departing from the scope of the present application. Various processes or components may be appropriately omitted, substituted or added to each example. For example, the described method may be performed in an order different from the order described, and various steps may be added, omitted or combined. In addition, features described in some examples may be combined in other examples.

[0030] The present application provides a passivity control method based on a Buck-Boost converter, specifically comprising:

[0031] When the inductor current is continuously conducted, the mathematical model of the Buck-Boost converter is established, and the system port controlled Hamiltonian model is obtained.

[0032] According to the system port controlled Hamiltonian model, starting from the two parts of energy shaping and damping injection and combining with the integral link, the outer loop controller of the traditional cascade and damping configuration is optimized.

[0033] In one embodiment of the present application, a specific implementation of the above method is provided, which specifically includes the following steps:

[0034] S11. Establish the mathematical model of Buck-Boost circuit in the continuous conduction mode (CCM) of the inductor current

[0035]

[0036] In the formula, x 1 、x 2 is the inductor current and capacitor voltage; R is the resistive load; P is the constant power of CPL; R L , R VD and R VT are the inductor, freewheeling diode and internal resistance of MOSFET respectively; controller u∈[0,1]; V dis is the voltage across the parasitic resistance V dis =-(R L +(1-u)*R VD +u*R VT )*x 1 .

[0037] S12, calculating and obtaining the port controlled Hamiltonian model (PCHD) of the system;

[0038] Let L x1 =z 1 ,C x2 =z 2 PCHD model of Buck-Boost converter:

[0039]

[0040] S13. Calculate the impact of constant power load on the system

[0041] Figure 2 This is a schematic diagram of the influence of the relationship between the constant power load and the resistance value of the resistive load on the system under open-loop control. Figure 2 Analysis, R>R CPL, the system operates in an undamped response state, there is no energy dissipation at the output, and the system oscillates. <R CPL , the system is stable, but the output end consumes a lot of energy. Aiming at the stability and energy consumption problems of Buck-Boost converter, the present invention adopts the port controlled Hamiltonian model (PCHD) and designs a new passive controller to shape the system energy, compensate the energy difference of the system, and maintain the stability of the system.

[0042] S21, Outer loop controller for optimizing passive controller

[0043] To obtain the desired energy function, obtain the desired energy function H d (z) Must meet the following requirements:

[0044]

[0045] In the formula, J d (z): Expected interconnection matrix, satisfying J d (z) = J 1 (z)+J 2 (z); R d (z): Expected damping matrix, satisfying R d (z) = R 1 (z)+R 2 (z).J 2 (z): interconnection injection matrix; R 2 (z): Damping injection matrix. H 2 (z): Injected energy function, satisfying H d (z) = H 1 (z)+H 2 (z); D 2 (z):H 2 (z) coefficient matrix; Without loss of generality, given the passive control law u,J 2 (z),R 2 (z) and D 2 (z) Satisfy:

[0046]

[0047] Substituting equation 2 into equation 4, we can get the traditional passive control law. To enhance the anti-interference capability of the system, we combine the traditional control law with the integral link and optimize the outer loop controller to obtain:

[0048]

[0049] In the formula, i L * The specific form is described in the next section. i The value is 0.8.

[0050] S3. Establish inner loop control of passive controller

[0051] Combination Figure 3 Analysis: 1 、z 2 The determination of the stable operating point is a necessary condition for the design of the passive controller. 1 The expected value, once there is external interference, the output voltage is difficult to reach the accurate value. Therefore, this section mainly requires the z 1 expected value.

[0052] First, find the power balance expression of Buck-Boost converter:

[0053]

[0054] In order to achieve stable output while meeting the requirement of fast response, the present invention uses a new type of fal 1 Compared with the traditional fal function, this fal function can effectively reduce the static error of the system while responding quickly.

[0055]

[0056] In the formula, β=5; α=0.5; δ=0.01; A∈(1,π), B is less than 1. In NLSEF, the conditions of large error and small gain and small error and large gain should be met. Therefore, when e≤δ, If the increase is more than 100 times, it is considered a large gain; A*tan*(B*|e| C ) is slightly less than 1, the present invention selects A = 1.57; B = 0.8, at this time That is, the control amount increases when the error is large; when |e|>1, A sgn 2 |e|, which satisfies the requirement of large error and small gain, thus speeding up the system convergence time; and the tan function makes the system converge more smoothly.

[0057] Figure 3 This is a comparison diagram of the error between the inner loop controller proposed in step S3 of the present invention and the traditional inner loop controller. Figure 3 It can be clearly seen that the convergence time of the improved inner loop controller is faster at startup, which is 3ms, much shorter than the 23ms of the traditional inner loop controller; when the power suddenly changes from 2KW to 1KW in 0.1s, the adjustment time and amplitude change of the controller are greatly improved.

[0058] It can be concluded that the expected value of the inductor current output by the current loop is:

[0059]

[0060] in, The additional error compensation can effectively reduce the static error of the system. Based on the above inner loop controller, the control equation of the passive controller of this application is obtained:

[0061]

[0062] As an improved solution, in an example of the present application, in order to verify the effectiveness of the above method, after the above method, the present embodiment further includes the following method:

[0063] The effectiveness and feasibility of the new passive controller are verified by simulation;

[0064] Specifically include: S41, dynamic performance analysis

[0065] Set the initial conditions and some parameters in the simulation experiment C = 2e-4F; L = 4e-4H; R = 50Ω; P CPL =1KW; R 1 =5Ω; j 1 =1; V in =200V; V o =200V; the new composite controller (passive controller) of the present invention is given by formula 9, and the specific parameters are as follows: A = 1.57; B = 0.8; β = 5; α = 0.5; δ = 0.01; combined Figure 4 Output voltage analysis: The passive controller proposed in this invention is compared with the traditional composite controller (the outer loop is consistent, the inner loop is the traditional fal function), PBC+PI In comparison, this simulation suddenly reduces the constant power load from 2KW to 1KW at 0.1s. Figure 4 This is a comparison diagram of the output voltages of the controller of the present invention and other controllers. It can be seen from the diagram that the present invention has high output accuracy; effectively shortens the time it takes for the system to reach the output voltage; and solves the problem of the inability to coordinate overshoot and rapidity.

[0066] S42. Stability analysis

[0067] Figure 5 is the phase diagram of the controller of the present invention, combined with Figure 5 Phase diagram analysis: The power of the constant power load is 1000W, and the output voltage is 200V, so the equivalent resistance value of the constant power load is 40Ω. At (0, 0.1s), R is 50Ω, that is, R>R CPL , after 0.1s, R drops from 50Ω to 25Ω, that is, R <R CPL When the circuit device parameters are perturbed, the proposed method can still achieve the expected output.

[0068] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A passive control method based on Buck-Boost converter, It is characterized in that Specifically include: In the continuous conduction state of the inductor current, the mathematical model of the Buck-Boost converter is established, and the system port controlled Hamiltonian model is obtained; According to the system port controlled Hamiltonian model, starting from the two parts of energy shaping and damping injection, and combining with the integral link, the outer loop controller of the traditional cascade and damping configuration is optimized; Redefine the inner loop controller of the system based on nonlinear feedback control to obtain the expected current of the system and further enhance the dynamic performance of the system; The outer loop controller for optimizing the traditional cascade and damping configuration specifically includes: The traditional passive control law is combined with the integral link to optimize the outer loop controller of the traditional cascade and damping configuration; the inner loop controller of the system is redefined based on the nonlinear feedback control to obtain the expected current of the system. The specific use method includes: Redefine the expected current of the system based on the improved fal function based on nonlinear feedback control; The inner loop controller uses the improved nonlinear feedback as the expected value, thereby redefining the expected current of the system; The control parameters of the Buck-Boost converter are as follows: Where e is the difference between the output voltage and the expected voltage. According to the experiment, the parameters β = 5; α = 0.5; δ = 0.01, k i The value is 0.8, A∈(1,π), B is less than 1; V dis is the voltage across the parasitic resistance V dis =-(R L +(1-u)*R VD +u*R VT )*x 1 ; R L , R VD and R VT They are the inductor, freewheeling diode and internal resistance of MOSFET respectively; the tan function speeds up the system convergence time when the error is large, and the convergence is smoother than the traditional function; The fall function of the Buck-Boost converter is specifically:

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