A control method and system for a DC converter of an electric fork truck to suppress bilateral disturbance

Abstract

The application discloses a kind of electric fork truck DC converter control method and system for inhibiting bilateral disturbance, the method is first obtained main circuit parameter, to the state variable of independent energy storage element State vector is structured, the state space equation under the state of switch on and off is established, then duty cycle is weighted average with weight to establish average state space model;Then the model is rewritten as standard form with duty cycle as control input, the integral of output voltage error is introduced as augmented state variable, and the augmented state space model containing integrator is constructed;Then the state feedback gain matrix is calculated by configuring the desired closed-loop pole, and the initial values of integrator and state variable are preset to construct the state feedback control law to obtain tracking controller;Finally, input side and output side disturbance test is applied, and the controller suppression performance is evaluated.The application realizes low overshoot, zero static error tracking control of converter under input voltage disturbance and reference voltage change through augmented state modeling and pole placement.

Description

Technical Field

[0001] This invention relates to the field of electric forklift power converter control technology, and more specifically, to a method and system for controlling an electric forklift DC-DC converter to suppress dual-sided disturbances. Background Technology

[0002] The power system of an electric forklift typically consists of a power battery pack and a low-voltage auxiliary power supply. The DC-DC converter is a key component for converting the power battery bus voltage to power the low-voltage system. The stability and control accuracy of its output voltage directly affect the normal operation of low-voltage equipment such as on-board instruments, lighting, and battery management systems. Existing products generally adopt a proportional-integral-derivative (PID) control strategy. This strategy generates a control signal to adjust the output voltage through proportional, integral, and derivative operations on the voltage error. Its structure is simple and easy to implement, and it is widely used in various DC-DC converters. However, this type of proportional-integral-derivative method has inherent defects: parameter tuning depends on engineering experience, and it usually requires repeated trial and error to obtain optimal performance; its ability to suppress input voltage fluctuations and load changes is limited. When the power battery bus voltage drops due to lifting heavy objects or rapid acceleration, or rises due to regenerative braking, the dynamic deviation of the output voltage is large and the recovery time is long.

[0003] To overcome the shortcomings of the aforementioned control algorithms, some technical solutions attempt to improve the main circuit structure and hardware to enhance the flexibility and integration of the DC-DC converter. However, hardware improvements often require additional components, increasing system cost and main circuit complexity. Furthermore, their control core still relies on the traditional proportional-integral-derivative feedback framework, making it difficult to fundamentally improve the converter's dynamic performance and disturbance rejection capability.

[0004] In summary, improving the robustness of the converter to disturbances at both the input and output ends and the accuracy of output voltage control are core requirements for achieving highly reliable power conversion and key indicators for evaluating the performance of electric forklift power systems. However, existing proportional-integral-derivative (PI-DE) control and hardware improvement schemes struggle to balance dynamic performance and steady-state accuracy. How to overcome the limitations of traditional frameworks and construct a new control method that considers both aspects is a pressing technical problem that needs to be solved in the field of DC-DC converter control for electric forklifts. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a control method and system for DC-DC converters of electric forklifts that suppresses two-sided disturbances.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for controlling a DC-DC converter in an electric forklift to suppress two-sided disturbances includes the following steps:

[0008] Step S1: Obtain the component parameters of the main circuit of the DC-DC converter of the electric forklift, construct the state vector with the state variables of the independent energy storage element, establish the state space equations under the power switch on and off states respectively, and then perform weighted averaging with duty cycle as weight to establish the average state space model of the converter.

[0009] Step S2: Rewrite the average state space model into a standard form with duty cycle as the control input, introduce the integral of the output voltage error as an augmented state variable, combine the original state vector with the augmented state variable to form an augmented state vector, and establish an augmented state space model containing the integrator.

[0010] Step S3: Based on the augmented state-space model, calculate the state feedback gain matrix by configuring the desired closed-loop poles, and preset the initial values ​​of the integrator and state variables to construct a state feedback control law with duty cycle as the control input, thereby obtaining the tracking controller.

[0011] Step S4: After the converter enters steady state, input-side disturbance and output-side disturbance are applied respectively, and the tracking controller's suppression performance against the two-sided disturbance is evaluated based on the dynamic response of the output voltage.

[0012] Furthermore, step S1 includes the following steps:

[0013] Step S11: Obtain the parameter values ​​of each component in the main circuit, select the state variables that can describe the energy storage state according to the type of the independent energy storage component, each independent energy storage component corresponds to a state variable, and combine all the state variables in order into a state vector.

[0014] Step S12: Based on the main circuit topology of the converter, Kirchhoff's voltage law and Kirchhoff's current law are used to establish the state space equations of the converter in the power switch on state and the power switch off state, respectively, to obtain the system matrix, input matrix, output matrix and direct transfer matrix in the on state, and the system matrix, input matrix, output matrix and direct transfer matrix in the off state.

[0015] Step S13: Using the duty cycle as the weight, perform a weighted average of the system parameter matrix in the on state and the system parameter matrix in the off state of the power switch to obtain the average state-space model of the converter.

[0016] Furthermore, in step S11, the independent energy storage elements are inductors and capacitors, and the state variables are inductor current and capacitor voltage.

[0017] Furthermore, step S2 includes the following steps:

[0018] Step S21: Rewrite the average state space model into a standard state space form with duty cycle as the control input, and absorb the input voltage as the average input quantity into the input matrix and direct transfer matrix in the standard state space form.

[0019] Step S22: Define the output voltage error based on the reference voltage and the converter output voltage, and define the integral of the output voltage error over time as the integral state, which is used as an augmented state variable;

[0020] Step S23: Augment the integral state to the average state vector to obtain the augmented state vector;

[0021] Step S24: Combine the rewritten average state-space model with the dynamic equations of the integrator to construct an augmented state-space model that includes the integrator.

[0022] Furthermore, in step S24, the expression for the augmented state-space model is:

[0023]

[0024] In the formula, For augmented state vectors; For augmented vectors The first derivative with respect to time; The duty cycle serves as the control input for the system. Reference voltage; The average state matrix in standard state-space form; The average input matrix in standard state-space form; This is the average output matrix in standard state-space form; This is the average direct transfer matrix in standard state-space form.

[0025] Furthermore, step S3 includes the following steps:

[0026] Step S31: Configure the desired poles of the closed-loop augmented system according to the desired settling time, damping ratio and overshoot. Calculate the state feedback gain matrix using the controllability verification matrix containing the augmented system matrix and the augmented input matrix, as well as the desired characteristic polynomial. The state feedback gain matrix contains the feedback gain of the corresponding average state variable and the feedback gain of the corresponding integral state.

[0027] Step S32: Calculate the final value of the average state variable of the converter in steady state and record it as the steady state vector. Based on the steady state vector, the feedback gain of the corresponding average state variable and the feedback gain of the corresponding integral state, calculate the initial preset value of the integrator.

[0028] Step S33: Construct a state feedback control law with the duty cycle as the control input based on the state feedback gain matrix, steady-state duty cycle, and augmented state vector.

[0029] Furthermore, in step S32, the initial preset value of the integrator is calculated based on the steady-state vector and the feedback gain of the corresponding integral state, and the integrator uses this preset value as the initial state when starting up.

[0030] Furthermore, step S4 includes the following steps:

[0031] Step S41: After the converter enters steady state, a step change is applied to the input voltage to simulate the input side disturbance, the dynamic response of the output voltage is observed and recorded, and the maximum dynamic deviation, recovery time and steady-state error of the output voltage are obtained.

[0032] Step S42: During the operation of the converter, a step change is applied to the reference voltage to simulate the output side disturbance, the tracking response of the output voltage is observed and recorded, and the tracking speed, overshoot and steady-state error of the output voltage are obtained.

[0033] Step S43: Based on the test results, evaluate the tracking controller's ability to suppress two-sided disturbances;

[0034] Step S44: Solidify the tracking controller parameters obtained through performance evaluation to obtain the final tracking controller parameter set.

[0035] Furthermore, the DC-DC converter for electric forklifts can be any of the topologies of Buck converter, Boost converter, or Buck-Boost converter.

[0036] The present invention also provides a DC-DC converter control system for electric forklifts that suppresses two-sided disturbances, comprising:

[0037] Memory, used to store computer programs and data;

[0038] A processor is used to implement the steps of the electric forklift DC-DC converter control method for suppressing two-sided disturbances as described above when executing a computer program.

[0039] The beneficial effects of this invention are:

[0040] 1. This invention establishes an average state-space model of an electric forklift DC converter and introduces the integral of the output voltage error as an augmented state variable to construct an augmented state-space model containing an integrator, thereby achieving an accurate description of the converter's dynamic behavior.

[0041] 2. This invention, by presetting the initial values ​​of the integrator and state variables according to the steady-state control law, ensures that the system is in a matched steady-state operating point upon startup. This avoids the startup shock and reverse overshoot caused by the integrator accumulating from zero in traditional methods, and achieves low overshoot and zero steady-state error tracking of the output voltage relative to the reference voltage.

[0042] 3. This invention can significantly improve the dynamic performance and anti-interference capability of DC converters for electric forklifts, providing reliable technical support for high-performance control of converters under complex operating conditions such as input voltage fluctuations and reference voltage changes. Attached Figure Description

[0043] Figure 1 This is a flowchart of a DC-DC converter control method for suppressing two-sided disturbances in an electric forklift, as described in this embodiment.

[0044] Figure 2 This is a main circuit diagram of the Buck converter in this embodiment;

[0045] Figure 3a This is a graph showing the response curves of the output voltage and the reference voltage in this embodiment;

[0046] Figure 3b This is a response curve of the tracking error in this embodiment;

[0047] Figure 3c This is a graph showing the response of the input voltage in this embodiment;

[0048] Figure 4a This is a graph showing the response curves of the actual duty cycle and the theoretical duty cycle in this embodiment;

[0049] Figure 4b This is a response curve of the duty cycle error in this embodiment;

[0050] Figure 5 This is a response curve of the integral state in this embodiment;

[0051] Figure 6a This is a graph showing the response curve of the inductor current in this embodiment;

[0052] Figure 6b This is a graph showing the response of the capacitor voltage in this embodiment;

[0053] Figure 7 This is a graph showing the change in load resistance in this embodiment. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] A control method for an electric forklift DC-DC converter that suppresses two-sided disturbances is proposed. This method first obtains the main circuit parameters of the converter, selects state variables based on independent energy storage elements, and establishes state equations for the power switch's on and off states. Weighted averaging with duty cycle as the weight results in an average state-space model describing the converter's macroscopic dynamic behavior. Then, the output voltage error is defined, and the error integral is introduced as an augmented state variable. The integrator's dynamic equation is combined with the original average state-space model to construct an augmented state-space model including the integrator. Next, the state feedback gain matrix is ​​calculated by configuring the desired closed-loop poles of the augmented system. Initial values ​​of the integrator and state variables are preset according to the steady-state control law, and a state feedback control law with duty cycle as the control input is constructed. Finally, input-side disturbances and reference voltage tracking tests are applied to evaluate the tracking controller performance and ultimately determine the tracking controller parameter set. This method, through the coordinated design of state augmentation, pole placement, and integrator numerical preset, achieves low overshoot and zero steady-state error tracking control of the electric forklift DC-DC converter under input voltage disturbance and reference voltage variation conditions.

[0056] like Figure 1 As shown, the method includes the following steps:

[0057] Step S1: Obtain the parameter values ​​of each component in the main circuit of the DC-DC converter for electric forklift, and select state variables that can describe the energy storage state of the independent energy storage components according to their types to construct a state vector. Each independent energy storage component corresponds to a state variable. Then, based on the main circuit topology, establish the state space equations of the converter in the power switch on and off states respectively. Finally, with the duty cycle as the weight, perform a weighted average of the state space equations in the on and off states to establish the average state space model of the converter.

[0058] Specifically, step S1 includes the following steps:

[0059] Step S11: Obtain the parameter values ​​of each component in the main circuit and select state variables to construct a state vector:

[0060] Obtain key parameters such as inductance, capacitance, load resistance, input voltage, and reference voltage in the main circuit of the DC-DC converter for the electric forklift. Based on the type of independent energy storage element, select state variables that describe its energy storage state. Each independent energy storage element corresponds to one state variable, denoted as the [missing value]. The state variables corresponding to each independent energy storage element are: Combine all state variables in order to form a state vector. , ,in, This refers to the total number of independent energy storage components. Index of the number of independent energy storage components This represents the transpose operator.

[0061] Furthermore, the DC-DC converter for electric forklifts can be any of the topologies of Buck converter, Boost converter, or Buck-Boost converter.

[0062] Step S12: Establish the state equations for the power switch in the on and off states based on the main circuit topology:

[0063] Based on the main circuit topology of the DC-DC converter for electric forklifts, Kirchhoff's voltage law and current law are used to establish the state-space equations of the converter in both the on and off states of the power switch. In the on state of the power switch, the system's state-space equation can be expressed as:

[0064]

[0065]

[0066] With the power switch off, the system's state-space equation can be expressed as:

[0067]

[0068]

[0069] In the formula, , , and This is the system parameter matrix under the power switch on state, specifically the system matrix, input matrix, output matrix, and direct transfer matrix; , , and This is the system parameter matrix under the power switch off state, specifically the system matrix, input matrix, output matrix, and direct transfer matrix; The input vector, i.e., the input voltage. ; The output vector, i.e., the output voltage. ; State vector The first derivative with respect to time, i.e., the rate of change of the state variable.

[0070] Step S13: Using the duty cycle as the weight, perform a weighted average of the system parameter matrices under the on and off states to establish the average state-space model of the converter.

[0071] With duty cycle As weights, for the system matrix in the on state Input matrix Output matrix and direct transfer matrix and the system matrix in the off state. Input matrix Output matrix and direct transfer matrix By performing a weighted average, the average state-space model of the converter is obtained:

[0072]

[0073]

[0074] In the formula, the overline on the variable represents the average value of the variable over one switching cycle; The average state vector; The average input vector; This is the average output vector; The duty cycle has a value that satisfies 0 < ≤1; Represents the average state vector The first derivative with respect to time. This average state-space model is a continuous model describing the macroscopic dynamic behavior of the converter, providing a theoretical basis for the subsequent design of the tracking controller.

[0075] Step S2: Rewrite the average state-space model into a standard form with duty cycle as the control input. Then, introduce the integral of the output voltage error as an augmented state variable. Combine the original state vector with the error integral to form an augmented state vector. Based on the average state-space model obtained in step S1, establish an augmented state-space model including the integrator. This unifies the description of the main circuit dynamics of the original system and the cumulative memory effect of the integrator, enabling the subsequent design of the tracking controller to actively adjust the control quantity using historical error information, thereby eliminating steady-state error.

[0076] Specifically, step S2 includes the following steps:

[0077] Step S21: Rewrite the average state-space model from step S13 into a standard form with duty cycle as the control input:

[0078] To facilitate the design of the tracking controller, the average state-space model is rewritten using duty cycle... To control the input in the standard state-space form, considering the average input vector, i.e., the input voltage ( Let be a constant, and absorb it into the input matrix and the direct transfer matrix to obtain:

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] In the formula, The duty cycle serves as the control input for the system. The average state matrix in standard state-space form is derived from the system matrix under the conducting state. System matrix under shutdown state The result is obtained by weighting the duty cycle. The average input matrix in standard state-space form is derived from the input matrix in the on-state. and the input matrix in the off state The result is obtained by weighting the duty cycle as the weight and then multiplying it by the ratio of the input voltage to the duty cycle. The average output matrix in standard state-space form is derived from the output matrix in the on-state. and the output matrix in the off state The result is obtained by weighting the duty cycle. The average direct transfer matrix in standard state-space form is derived from the direct transfer matrix in the on state. Direct transfer matrix in the off state The result is obtained by weighting the duty cycle as the weight and then multiplying it by the ratio of the input voltage to the duty cycle.

[0086] Step S22, define the output voltage error:

[0087] Based on reference voltage and converter output voltage Define output voltage error , Output voltage error Integration over time As an augmented state variable Integral state It is used to accumulate historical error information, providing memory capability for achieving zero steady-state error control.

[0088] Step S23, introduce the integral state as an augmented state variable:

[0089] Average state vector based on the average state space model The integration state in step S22 Augmentation yields the augmented state vector. , .

[0090] Step S24, construct the augmented state space model:

[0091] The rewritten average state-space model and the dynamic equations of the integrator By combining the equations, we can construct the following augmented state-space model that includes an integrator:

[0092]

[0093]

[0094] In the formula, For augmented state vectors; For augmented state vectors The first derivative with respect to time; The duty cycle serves as the control input for the system. Reference voltage; The average state matrix in standard state-space form; The average input matrix in standard state-space form; This is the average output matrix in standard state-space form; This is the average direct transfer matrix in standard state-space form. This augmented state-space model describes the macroscopic dynamic behavior of the converter's main circuit states and the integral action required to eliminate steady-state errors, providing a complete mathematical foundation for achieving zero steady-state error tracking and suppressing input-side voltage disturbances and output-side load disturbances.

[0095] Step S3: Based on the augmented state-space model obtained in Step S2, the augmented state feedback gain matrix is ​​determined by configuring the closed-loop poles of the augmented system. Initial values ​​for the integrator and state variables are preset, and a tracking controller capable of suppressing two-sided disturbances is designed to achieve zero steady-state error and low overshoot tracking of the output voltage to the reference voltage. After obtaining the tracking controller, proceed to Step S4 for performance evaluation and parameter tuning.

[0096] Specifically, step S3 includes the following:

[0097] Step S31: Configure the desired closed-loop poles and calculate the feedback gain matrix:

[0098] Based on the desired settling time, damping ratio, overshoot, and other converter dynamic performance indicators, a closed-loop augmented system is provided. Configure the desired pole set ,in, The state matrix of the closed-loop augmented system is represented by the following formula, and the state feedback gain matrix is ​​calculated as follows:

[0099]

[0100]

[0101]

[0102] In the formula, The state feedback gain matrix; For the corresponding average state variable Feedback gain; For the corresponding integral state Feedback gain; For matrix pairs The constructed controllability verification matrix, To augment the system matrix, To augment the input matrix, , ; For the expected characteristic polynomial of the closed-loop augmented system, The independent variable of the characteristic polynomial; For augmented state vectors The dimension of is also equal to the expected number of closed-loop poles. For dimensional index, ; For the closed-loop augmented system The desired closed-loop pole, i.e., the first pole in the pole set. Extreme points; superscript This represents the inverse of a matrix.

[0103] Step S32, preset the integrator and the initial values ​​of the state:

[0104] Calculate the final value of the average state variables of the converter under steady-state conditions, i.e., the converter output voltage. equal to reference voltage The average state vector at time t is denoted as the steady-state vector. Calculate the initial preset value of the integrator using the following formula:

[0105]

[0106] In the formula, This is the initial preset value for the integrator; For the corresponding average state variable Feedback gain; For the corresponding integral state The feedback gain. This initial preset value ensures that the integrator and state variables are at matched steady-state values ​​at startup, avoiding startup shocks and reverse overshoot caused by accumulating from zero.

[0107] Step S33, construct the augmented state feedback control law:

[0108] Based on the state feedback gain matrix calculated in step S31 Set the duty cycle according to the following formula. State feedback control law for controlling input:

[0109]

[0110] In the formula, This represents the steady-state duty cycle. This is the augmented state vector.

[0111] Step S4: Based on the tracking controller designed in step S3, the tracking controller's suppression performance against two-sided disturbances is evaluated by applying disturbance tests on the input and output sides. The tracking controller parameters are then fine-tuned based on the evaluation results to finally determine the tracking controller parameter set that meets the design requirements.

[0112] Specifically, step S4 includes the following steps:

[0113] Step S41, Apply input-side perturbation test:

[0114] After the converter enters steady state, a step change is applied to the input voltage to simulate input-side disturbance. The dynamic response of the output voltage is observed and recorded, and performance indicators such as the maximum dynamic deviation, recovery time, and steady-state error of the output voltage are recorded.

[0115] Step S42, Apply output-side perturbation test:

[0116] During converter operation, a step change is applied to the reference voltage to simulate output-side disturbances. The tracking response of the output voltage is observed and recorded, along with performance indicators such as tracking speed, overshoot, and steady-state error.

[0117] Step S43, evaluate the tracking controller's disturbance rejection and tracking performance:

[0118] Based on the test results of steps S41 and S42, evaluate the tracking controller's ability to suppress two-sided disturbances. If all indicators meet the design requirements, proceed to step S44. If not, adjust the desired pole configuration parameters in step S31, recalculate the feedback gain matrix, and repeat steps S32 to S43.

[0119] Step S44 involves solidifying the tracking controller parameters obtained from the performance evaluation to obtain the final tracking controller parameter set. The parameter set includes the state feedback gain matrix. Steady-state duty cycle Integrator initial preset value and average initial values ​​of state variables .

[0120] The present invention also provides a DC-DC converter control system for suppressing two-sided disturbances in electric forklifts, including a memory and a processor, wherein the memory is used to store computer programs and data; and the processor is used to implement the steps of the above-described DC-DC converter control method for suppressing two-sided disturbances in electric forklifts when executing the computer program.

[0121] Example 1: Application of DC-DC converters in electric forklifts

[0122] In this embodiment, the power battery bus voltage is 80V, and the reference voltage is 24V. Figure 2 The Buck converter topology shown is used as an example for detailed explanation. Figure 2 middle, SW is the input voltage, D is the power switch, D is the freewheeling diode, and L is the inductor. R is the capacitor, and R is the load resistance. This is the output voltage. This Buck converter is a step-down DC-DC converter. Its working principle is as follows: the power switch SW switches on and off at a high frequency according to a certain duty cycle. When the power switch SW is on, the input voltage... The power switch SW supplies power to the load resistor R while the inductor L stores energy. When the power switch SW is turned off, the inductor L supplies power to the load resistor R via the freewheeling diode D. The output voltage can be controlled by adjusting the duty cycle. Size.

[0123] Following step S1, establish the average state-space model of the Buck converter:

[0124] Obtain the parameter values ​​of each component in the main circuit and select state variables to construct a state vector. In this embodiment, the parameters of the Buck converter main circuit are set as follows: inductor L = 100μH, capacitor... =100μF, load resistance R=12Ω, input voltage =80V, reference voltage =24V. The above parameters correspond to the following design specifications: output voltage 24V, output current 2A, switching frequency 100kHz. According to the working principle of the Buck converter, the steady-state duty cycle... Selecting the inductor current and capacitor voltage Two state variables are combined to obtain a state vector. , , This is the transpose operator.

[0125] State equations for the power switch's on and off states are established based on the main circuit topology. In this embodiment, the input voltage is selected. Let u be the input vector and u be the output voltage. Let y be the output vector. In the Buck converter with the power switch on, the inductor voltage satisfies... The capacitor current satisfies Rearranging these into matrix form, we can obtain the state-space equation parameter matrix of the system under the power switch on state:

[0126] , , , ,

[0127] in, , , and These are the system matrix, input matrix, output matrix, and direct transfer matrix under the on-state conditions, respectively.

[0128] When the power switch of the Buck converter is off, the inductor voltage satisfies The capacitor current satisfies Rearranging these into matrix form, we can obtain the state-space equation parameter matrix of the system under the power switch off state:

[0129] , , , ,

[0130] in, , , and These are the system matrix, input matrix, output matrix, and direct transfer matrix in the off state, respectively.

[0131] The specific parameters in this embodiment are: L=100μH, Substituting 100μF and R=12Ω into the above matrix, we can obtain the numerical state-space model.

[0132] A weighted average of the system parameter matrices under the on and off states, using duty cycle as the weight, is used to establish the average state-space model of the converter. Due to the Buck converter... = , = The weighted average yields the average state-space model of the Buck converter as follows:

[0133]

[0134]

[0135] In the formula, The average state vector, ; Represents the average state vector The first derivative with respect to time; The average output voltage. ; , and These represent the average values ​​of inductor current, capacitor voltage, and output voltage over one switching cycle.

[0136] The specific parameters in this embodiment are: L=100μH, =100μF, R=12Ω =80V, substituting into the above model, we can obtain the numerical form of the average state-space model.

[0137] Following step S2, establish the augmented state-space model of the Buck converter:

[0138] The average state-space model of the Buck converter is rewritten into a standard state-space form with duty cycle as the control input. The standard state-space model with duty cycle as the control input is calculated as follows:

[0139]

[0140]

[0141] In the formula, The average state vector; Represents the average state vector The first derivative with respect to time; This is the average output voltage; The duty cycle serves as the control input for the system.

[0142] For Buck converters, the output voltage Define the output voltage error , .

[0143] Introducing Integral States As an augmented state variable , integrate state Augmented to average state vector The augmented state vector is obtained. , .

[0144] The augmented state-space model including the integrator is as follows:

[0145]

[0146]

[0147] In the formula, For augmented state vectors; For augmented state vectors The first derivative with respect to time; The duty cycle serves as the control input for the system. This is the reference voltage.

[0148] The specific parameters in this embodiment are: L=100μH, =100μF, R=12Ω =80V, substituting into the above model, we can obtain the numerical form of the augmented state-space model.

[0149] Following step S3, calculate the tracking controller for the Buck converter:

[0150] For Buck converters, set the desired dynamic performance metrics: settling time. ≤2ms, damping ratio =0.9, natural frequency =1.5kHz, natural angular frequency =2π .

[0151] Configure the desired closed-loop poles: , ;in, For the first pair of desired closed-loop poles (conjugate complex pairs) of the closed-loop augmented system. This is the third desired closed-loop pole of the closed-loop augmented system; This indicates taking the real part of a complex number; It is the imaginary unit.

[0152] The state feedback gain matrix was calculated. ,in Corresponding average state variable Feedback gain, , Corresponding integration state Feedback gain.

[0153] For the Buck converter, the reference voltage is known. =24V, load resistance R=12Ω, calculate the steady-state vector. , Calculate the initial preset value of the integrator. =0.00444.

[0154] The above calculation results and steady-state duty cycle Substituting 0.3 into the augmented state feedback control law formula, we obtain the complete control law as follows: .

[0155] Perform the performance evaluation and parameter tuning of the Buck converter according to step S4:

[0156] Input-side disturbance test: Design the tracking controller and build a simulation platform according to steps S1 to S3. At simulation time t=5ms, the input voltage is suddenly increased from 80V to 88V to simulate the instantaneous rise of the power battery bus voltage during regenerative braking of the electric forklift. At simulation time t=10ms, the input voltage is suddenly dropped from 88V to 80V. The output voltage response is observed and the performance indicators are recorded.

[0157] Reference voltage tracking test: At simulation time t=2ms, the reference voltage is reduced from 24V to 23V, and at simulation time t=8ms, the reference voltage is increased from 23V to 24V. The output voltage response is observed and the performance indicators are recorded.

[0158] Based on the above test results, the input voltage disturbance suppression ratio is approximately 0.02, the tracking response time is less than 0.5ms, and the steady-state error is close to 0V. All indicators meet the design requirements, and there is no need to adjust the tracking controller parameters.

[0159] The tracking controller parameters that have passed performance evaluation are solidified to obtain the final tracking controller parameter set.

[0160] The simulation results of this embodiment are as follows: Figures 3a-3c , Figure 4a , Figure 4b , Figure 5 , Figure 6a , Figure 6b and Figure 7 As shown.

[0161] from Figures 3a-3c It can be seen that the output voltage can quickly and without overshoot track changes in the reference voltage, smoothly transitioning during step changes in the reference voltage without reverse overshoot; under step disturbances in the input voltage, the output voltage only produces a small deviation and recovers quickly, with the steady-state error approaching zero, indicating that the tracking controller has good reference voltage tracking capability and input-side disturbance suppression performance. Figure 4a and Figure 4bAs can be seen, the actual duty cycle can accurately track the changes in the theoretical duty cycle, and the duty cycle error converges quickly to zero, indicating that the tracking controller has a fast and accurate control response capability. From Figure 5 Thus, the integral state is preset to an initial value matching the steady state at system startup, avoiding the startup shock and reverse overshoot caused by the accumulation from zero in traditional integrators. The integral state is smoothly adjusted when the reference voltage changes and disturbances occur, ensuring the stability of the tracking controller. Figure 6a and Figure 6b It can be seen that the inductor current and capacitor voltage can quickly adjust to new steady-state values ​​under two-sided disturbances, indicating that the tracking controller can effectively coordinate the dynamic response of state variables. From Figure 7 It can be seen that the load resistance undergoes a step change at the set time, simulating the switching process of the low-voltage load of the electric forklift. The output voltage can still remain stable under this disturbance, verifying the tracking controller's ability to suppress output-side disturbances.

[0162] This embodiment verifies the effectiveness of the method proposed in this invention. Through augmented state-space modeling, pole placement, and integrator initial value presetting, this method achieves low overshoot and zero steady-state error tracking control of the Buck converter under input voltage disturbances, load disturbances, and reference voltage variations, significantly improving the converter's dynamic performance and disturbance rejection capability.

[0163] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A control method for a DC-DC converter in an electric forklift that suppresses two-sided disturbances, characterized in that, Includes the following steps: Step S1: Obtain the component parameters of the main circuit of the DC-DC converter of the electric forklift, construct the state vector with the state variables of the independent energy storage element, establish the state space equations under the power switch on and off states respectively, and then perform weighted averaging with duty cycle as weight to establish the average state space model of the converter. Step S2: Rewrite the average state space model into a standard form with duty cycle as the control input, introduce the integral of the output voltage error as an augmented state variable, combine the original state vector with the augmented state variable to form an augmented state vector, and establish an augmented state space model containing the integrator. Step S3: Based on the augmented state-space model, calculate the state feedback gain matrix by configuring the desired closed-loop poles, and preset the initial values ​​of the integrator and state variables to construct a state feedback control law with duty cycle as the control input, thereby obtaining the tracking controller. Step S4: After the converter enters steady state, input-side disturbance and output-side disturbance are applied respectively, and the tracking controller's suppression performance against the two-sided disturbance is evaluated based on the dynamic response of the output voltage.

2. The method for controlling a DC-DC converter in an electric forklift to suppress two-sided disturbances according to claim 1, characterized in that, Step S1 includes the following steps: Step S11: Obtain the parameter values ​​of each component in the main circuit, select the state variables that can describe the energy storage state according to the type of the independent energy storage component, each independent energy storage component corresponds to a state variable, and combine all the state variables in order into a state vector. Step S12: Based on the main circuit topology of the converter, Kirchhoff's voltage law and Kirchhoff's current law are used to establish the state space equations of the converter in the power switch on state and the power switch off state, respectively, to obtain the system matrix, input matrix, output matrix and direct transfer matrix in the on state, and the system matrix, input matrix, output matrix and direct transfer matrix in the off state. Step S13: Using the duty cycle as the weight, perform a weighted average of the system parameter matrix in the on state and the system parameter matrix in the off state of the power switch to obtain the average state-space model of the converter.

3. The method for controlling a DC-DC converter of an electric forklift to suppress two-sided disturbances according to claim 2, characterized in that, In step S11, the independent energy storage elements are inductors and capacitors, and the state variables are inductor current and capacitor voltage.

4. The method for controlling a DC-DC converter of an electric forklift to suppress two-sided disturbances according to claim 1, characterized in that, Step S2 includes the following steps: Step S21: Rewrite the average state space model into a standard state space form with duty cycle as the control input, and absorb the input voltage as the average input quantity into the input matrix and direct transfer matrix in the standard state space form. Step S22: Define the output voltage error based on the reference voltage and the converter output voltage, and define the integral of the output voltage error over time as the integral state, which is used as an augmented state variable; Step S23: Augment the integral state to the average state vector to obtain the augmented state vector; Step S24: Combine the rewritten average state-space model with the dynamic equations of the integrator to construct an augmented state-space model that includes the integrator.

5. The method for controlling a DC-DC converter of an electric forklift to suppress two-sided disturbances according to claim 4, characterized in that, In step S24, the expression for the augmented state-space model is: In the formula, For augmented state vectors; For augmented vectors The first derivative with respect to time; The duty cycle serves as the control input for the system. Reference voltage; The average state matrix in standard state-space form; The average input matrix in standard state-space form; This is the average output matrix in standard state-space form; This is the average direct transfer matrix in standard state-space form.

6. The method for controlling a DC-DC converter of an electric forklift to suppress two-sided disturbances according to claim 1, characterized in that, Step S3 includes the following steps: Step S31: Configure the desired poles of the closed-loop augmented system according to the desired settling time, damping ratio and overshoot. Calculate the state feedback gain matrix using the controllability verification matrix containing the augmented system matrix and the augmented input matrix, as well as the desired characteristic polynomial. The state feedback gain matrix contains the feedback gain of the corresponding average state variable and the feedback gain of the corresponding integral state. Step S32: Calculate the final value of the average state variable of the converter in steady state and record it as the steady state vector. Based on the steady state vector, the feedback gain of the corresponding average state variable and the feedback gain of the corresponding integral state, calculate the initial preset value of the integrator. Step S33: Construct a state feedback control law with the duty cycle as the control input based on the state feedback gain matrix, steady-state duty cycle, and augmented state vector.

7. The method for controlling a DC-DC converter in an electric forklift to suppress two-sided disturbances according to claim 6, characterized in that, In step S32, the initial preset value of the integrator is calculated based on the steady-state vector and the feedback gain of the corresponding integral state. The integrator uses this preset value as the initial state when it starts up.

8. The method for controlling a DC-DC converter of an electric forklift to suppress two-sided disturbances according to claim 1, characterized in that, Step S4 includes the following steps: Step S41: After the converter enters steady state, a step change is applied to the input voltage to simulate the input side disturbance, the dynamic response of the output voltage is observed and recorded, and the maximum dynamic deviation, recovery time and steady-state error of the output voltage are obtained. Step S42: During the operation of the converter, a step change is applied to the reference voltage to simulate the output side disturbance, the tracking response of the output voltage is observed and recorded, and the tracking speed, overshoot and steady-state error of the output voltage are obtained. Step S43: Based on the test results, evaluate the tracking controller's ability to suppress two-sided disturbances; Step S44: Solidify the tracking controller parameters obtained through performance evaluation to obtain the final tracking controller parameter set.

9. The method for controlling a DC-DC converter of an electric forklift to suppress two-sided disturbances according to claim 1, characterized in that, The DC-DC converter for electric forklifts can be any of the topologies of Buck converter, Boost converter, or Buck-Boost converter.

10. A DC-DC converter control system for an electric forklift that suppresses two-sided disturbances, characterized in that, include: Memory, used to store computer programs and data; A processor for executing a computer program to implement the steps of the electric forklift DC-DC converter control method for suppressing two-sided disturbances as described in any one of claims 1 to 9.

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