Robust sliding mode control method and system for BOOST converter under constant power load

Abstract

The invention belongs to the technical field of power electronic equipment, and particularly provides a robust sliding mode control method and system for a BOOST converter under a constant power load, and the method comprises the steps: building a bivariate state space model under the BOOST converter; according to the bivariate state space model, constructing a fuzzy controller in a robust sliding mode control framework, and introducing a current compensation mechanism to obtain a robust sliding mode control model; determining a robust sliding mode control structure according to the robust sliding mode control model; and the robust sliding mode control structure is adopted to control the constant power output of the BOOST converter. A fuzzy controller is constructed in a robust sliding mode control framework, a current compensation mechanism is introduced, bus voltage oscillation is effectively restrained, and meanwhile it is ensured that a converter stably outputs constant power.

Description

Technical Field

[0001] This disclosure relates to the field of power electronic equipment technology, and in particular to a robust sliding mode control method and system for a BOOST converter under constant power load. Background Technology

[0002] Due to the development of power electronics technology, cascaded DC / DC converter systems are showing an increasing trend in power systems. Among them, DC microgrid systems have received widespread attention. Figure 2 This demonstrates a typical traditional DC microgrid structure. The main structure consists of cascaded DC / DC converters. The preceding DC / DC converter provides constant power to the load. The subsequent closed-loop controlled DC / DC converter acts as a constant-power load (converter-point-of-load converter, CPL), absorbing constant power from the bus and exhibiting constant-power load characteristics. Its negative impedance characteristic can cause system instability. Furthermore, the constant-voltage load in the microgrid requires a constant voltage to operate. The CPL converter can have an unstable effect on the preceding converter operating in continuous conduction mode, causing bus voltage oscillations, which poses a challenge to power system stability control.

[0003] Robust sliding mode control (SMT) is gaining increasing attention as a novel control strategy. SMT controllers are designed based on output power, inductor current, output voltage, and input voltage. During modeling, SMT controllers require high model accuracy because precise values ​​for the switching transistors and circuit internal resistances are difficult to obtain, yet even small changes in these values ​​can cause the capacitor sampling voltage to deviate from the reference value. Therefore, it is necessary to design a novel robust sliding mode control method to address the instability caused by CPL converters and improve the applicability of the method. Summary of the Invention

[0004] This disclosure aims to at least solve one of the technical problems existing in the prior art, and proposes a robust sliding mode control method and system for BOOST converters under constant power load.

[0005] In a first aspect, this disclosure provides a robust sliding mode control method for a BOOST converter under constant power load, including:

[0006] S1. Establish a bivariate state-space model under the BOOST converter;

[0007] S2. Based on the bivariate state-space model, a fuzzy controller is constructed within the robust sliding mode control framework, and a current compensation mechanism is introduced to obtain the robust sliding mode control model.

[0008] S3. Based on the robust sliding mode control model, establish the robust sliding mode control structure;

[0009] S4. The robust sliding mode control structure is used to control the constant power output of the BOOST converter.

[0010] Preferably, S1 specifically includes:

[0011] Based on the state variables of the BOOST converter circuit and the switch conduction state, a bivariate state-space model in BOOST mode is established. The state variables of the BOOST converter include inductor current and output capacitor voltage.

[0012] Preferably, the bivariate state-space model is as follows:

[0013]

[0014] In the formula, x1 is the inductor current, x2 is the capacitor voltage, E is the input voltage, P is the output power, D is the duty cycle, L is the inductance value, and C is the capacitance value.

[0015] Preferably, the construction process of the robust sliding mode control model in S2 specifically includes:

[0016] The control objective is to maintain the stability of the output voltage while keeping the power constant; therefore, the sliding surface S is designed as follows:

[0017] S = x1x2-x r1 x r2

[0018] Where x1 is the inductor current, x2 is the capacitor voltage, and x r1 x is the inductor reference current. r2 The reference voltage is the capacitor reference voltage; the reference voltage is the desired bus voltage, which is a system parameter. The reference current is the desired power divided by the bus voltage plus the compensated internal resistance loss current.

[0019] The sliding mode reaching law is:

[0020]

[0021] In the formula, λ and K are adjustable parameters that are greater than zero, and the symbolic function sgn(s) represents the switching control function;

[0022] The inductor reference current is:

[0023]

[0024] In the formula, P is the constant power and E is the input voltage.

[0025] Preferably, in step S2, to reduce the deviation, the inductor reference current is compensated, and the compensated inductor reference current x kr1 for:

[0026]

[0027] In the formula, r is the internal resistance.

[0028] Preferably, the compensation mechanism in S2 is a fuzzy control rule, specifically including:

[0029] When the output voltage is less than the reference voltage, that is, the internal resistance is less than its true value, in order to eliminate the deviation, the output voltage deviation is reduced by increasing the internal resistance.

[0030] When the output voltage is greater than the reference voltage, that is, the internal resistance value is greater than its true value, the output voltage deviation is reduced by decreasing the internal resistance in order to eliminate the deviation.

[0031] Preferably, the output D(t) of the robust sliding membrane control structure in S3 is:

[0032]

[0033] Where λ and K are adjustable parameters greater than zero, the symbolic function sgn(s) represents the switching control function, x1 is the inductor current, x2 is the capacitor voltage, P is the constant power, E is the input voltage, L is the inductance value, and C is the capacitor value.

[0034] The present invention also provides a robust sliding mode control system for a BOOST converter under constant power load, the system being used to implement the robust sliding mode control method for a BOOST converter under constant power load as described in any of claims 1 to 7, the system comprising:

[0035] The first building module is configured to establish a bivariate state-space model under the BOOST converter;

[0036] The second construction module is configured to construct a fuzzy controller within the robust sliding mode control framework based on the bivariate state space model, introduce a current compensation mechanism, and obtain a robust sliding mode control model.

[0037] The structure determination module is configured to establish a robust sliding mode control structure based on the robust sliding mode control model.

[0038] The output module is configured to control the constant power output of the BOOST converter using the robust sliding mode control structure.

[0039] The present invention also provides an electronic device, comprising:

[0040] One or more processors;

[0041] A memory is configured to store computer-executable instructions, which, when executed, cause the processor to perform a robust sliding mode control method for a BOOST converter under constant power load as described in any one of claims 1-7.

[0042] The present invention also provides a storage medium for storing computer-executable instructions, which, when executed, implement the steps of the robust sliding mode control method for a BOOST converter under constant power load as described in any one of claims 1-7.

[0043] Beneficial effects: By constructing a fuzzy controller within a robust sliding mode control framework and introducing a current compensation mechanism, the bus voltage oscillation is effectively suppressed, while ensuring the converter outputs a stable and constant power. Attached Figure Description

[0044] Figure 1 A schematic diagram of robust sliding mode control of a BOOST converter under constant power load provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of a typical traditional DC microgrid structure mentioned in the background section.

[0046] Figure 3 The capacitor voltage waveform diagram provided in the embodiment of the present invention;

[0047] Figure 4 The load power curve of the control strategy proposed for sampling provided in the embodiments of the present invention;

[0048] Figure 5 This is a voltage curve diagram corresponding to a sudden change in constant power load provided in an embodiment of the present invention;

[0049] Figure 6 The inductor reference current and actual current curves are provided for embodiments of the present invention. Detailed Implementation

[0050] To enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this document.

[0051] according to Figure 2 It can be seen that traditional DC microgrids with constant power loads need to have the following characteristics:

[0052] A typical microgrid consists of a front-end DC / DC boost converter, a back-end converter, and a constant-voltage load. The source power for the DC / DC boost converter can be photovoltaic cells, fuel cells, etc., and its core function is to regulate the DC bus voltage within a set range. The DC bus is connected to a constant-voltage load, an R-type load with a point-of-load converter at the front end. The combination of a fixed resistor R and the point-of-load converter constitutes a constant-power load, with a constant load power (the magnitude of which can be arbitrarily set by the user).

[0053] The characteristics of a constant power load can be expressed as follows:

[0054]

[0055] In the formula, P represents constant power, iCPL represents CPL drive current, and VB represents bus voltage.

[0056] The BOOT converter samples the robust sliding diaphragm control controller. The controller output is the duty cycle driven by Q1. The BOOST circuit operates in continuous mode, and the duty cycle driven by Q2 is the inverse of the duty cycle driven by Q1.

[0057] This invention provides a robust sliding mode control method for a current-compensated BOOST converter under constant power load. Figure 1 This is a schematic diagram of a robust sliding mode control method for a current-compensated BOOST converter under constant power load according to an embodiment of the present invention. Figure 1 As shown, the robust sliding mode control method for a BOOST converter under constant power load according to an embodiment of the present invention includes:

[0058] S1. Establish a bivariate state-space model of the BOOST converter;

[0059] S2. Based on the state-space model, a fuzzy controller was designed within the robust sliding mode control framework, and a current compensation mechanism was introduced to establish a robust sliding mode control model.

[0060] S3. Based on the robust sliding mode control model, establish the robust sliding mode control structure.

[0061] S4. The robust sliding mode control structure is used to perform constant power output control under the BOOST converter.

[0062] This method constructs a fuzzy controller within a robust sliding mode control framework and introduces a current compensation mechanism, which effectively suppresses bus voltage oscillations while ensuring the converter outputs constant power stably.

[0063] A further solution is as follows: In step S1, a bivariate state-space model in BOOST mode is established based on the state variables of the BOOST circuit and the switch conduction state. The state variables of the BOOST converter include inductor current and output capacitor voltage.

[0064] The bivariate state-space model is as follows:

[0065]

[0066] In the formula, x1 is the inductor current, x2 is the capacitor voltage, E is the input voltage, P is the output power, and D is the duty cycle.

[0067] In step S2:

[0068] Based on the bivariate state-space model of the BOOST converter, a robust sliding mode control model based on current compensation is constructed, specifically as follows:

[0069] The control objective is to maintain output voltage stability while keeping the power constant. The sliding surface is designed as follows:

[0070] S = x1x2-x r1 x r2

[0071] Where x1 is the inductor current, x2 is the capacitor voltage, and x r1 x is the inductor reference current. r2 The reference voltage is the capacitor reference voltage. The reference voltage is the desired bus voltage, a system parameter. The reference current is the desired power divided by the bus voltage, plus the compensated internal resistance loss current.

[0072] The sliding mode reaching law is:

[0073]

[0074] In the formula, λ and K are adjustable parameters that are greater than zero, and the symbolic function sgn() represents the switching control function.

[0075] The reference current is:

[0076]

[0077] In the formula, P represents the constant power of the power.

[0078] Since the precise values ​​of the switching transistor internal resistance and line internal resistance of the entire system, namely the BOOST converter, are difficult to obtain, but their small changes can cause the capacitor sampling voltage to deviate from the reference value, this invention defines this voltage deviation Vloss as the input variable of fuzzy control, and the output variable as the equivalent internal resistance r. The membership function of the fuzzy variable is selected as a triangle. The basic universe of discourse of the normalized input variable is [-1,1], and the fuzzy subset of the input linguistic variable is taken as negative large, negative small, zero, positive small, and positive large, denoted as {NB,NS,ZE,PS,PB}. The basic universe of discourse of the normalized output variable is [0,1], and the fuzzy subset of the input linguistic variable is taken as minimal, small, medium, large, and maximal, denoted as {KP,KS,Z,DS,DB}.

[0079] Table 1 shows the fuzzy control rules as follows:

[0080] Vloss NB NS ZE PS PB r DB DS Z KS KP

[0081] The compensation mechanism in S2 uses fuzzy control rules. The principle of fuzzy control rules is as follows: when the output voltage is less than the reference voltage, it means that the internal resistance is less than its true value. To eliminate the deviation, the internal resistance is increased, thereby reducing the output voltage deviation. When the output voltage is greater than the reference voltage, it means that the internal resistance is greater than its true value. To eliminate the deviation, the internal resistance is decreased, thereby reducing the output voltage deviation.

[0082] Compensated reference current x r1 for:

[0083]

[0084] In the formula, r is the internal resistance.

[0085] In step S3:

[0086] Based on the robust sliding mode control model, the controller structure is established, specifically including:

[0087] The controller input and output relationship is as follows:

[0088]

[0089] Based on the robust sliding mode control structure, constant power output control is performed under the BOOST converter. The sampling unit calculates the difference between the product of the capacitor voltage and the inductor current and the product of the capacitor reference voltage and the compensated inductor reference current; this difference gives the value of the sliding surface S. After passing through the robust sliding mode controller, the resulting control quantity is compared with the triangular carrier information of the switching frequency to generate a PWM wave. By adding a loss compensation mechanism to the robust sliding mode control, a constant power is provided to the load while ensuring stable output voltage.

[0090] The verification of the proposed control method is as follows:

[0091] exist Figure 1 In the simplified model of a typical DC microgrid system shown, the BOOST converter is connected to a 50V DC power supply, the bus voltage is 200V, and the load is a 1kW constant power load. In conventional modeling, the internal resistances of the switching devices and circuits are usually ignored due to their small size. However, sliding mode control requires high model accuracy. Assuming the internal resistances of the power devices and circuits are both 0.22Ω, the simulation results are as follows... Figure 3 As shown, ignoring these internal resistances would cause the output voltage to drop to approximately 184V.

[0092] To improve the applicability of robust sliding mode control in BOOST converters under constant power loads, this embodiment designs a fuzzy controller within the robust sliding mode control framework and introduces a current compensation mechanism. Figure 4 The display shows the changes in a constant power load. The constant power load increases by 50% at 0.2s and returns to 1kW at 2.5s; then the load power decreases by 50% at 0.4s and returns to 1kW again at 4.5s.

[0093] Figure 5 The output voltage waveform of the BOOST converter using the robust sliding mode control method proposed in this invention under a constant power load is shown. The results show that when the constant power load undergoes a sudden change, the output voltage will show a small spike at the step moment under the action of the controller (within ±3.3V of the reference value).

[0094] Figure 6 The inductor reference current and actual waveform are shown under a constant power load, employing the robust sliding mode control method for the BOOST converter proposed in this invention. The results demonstrate that the proposed control method can ensure consistency between the reference current and the actual current.

[0095] By employing the embodiments of the present invention, the following beneficial effects are achieved:

[0096] A fuzzy controller is designed within the robust sliding mode control framework, and a current compensation mechanism is introduced to stabilize the output voltage while ensuring constant power, thereby improving the operational stability of the BOOST converter.

[0097] This invention also provides a robust sliding mode control system for a BOOST converter under constant power load. The system can be used to implement the aforementioned robust sliding mode control method for a BOOST converter under constant power load. The system includes:

[0098] The first building module is configured to establish a bivariate state-space model under the BOOST converter;

[0099] The second construction module is configured to construct a fuzzy controller within the robust sliding mode control framework based on the bivariate state space model, introduce a current compensation mechanism, and obtain a robust sliding mode control model.

[0100] The structure determination module is configured to establish a robust sliding mode control structure based on the robust sliding mode control model.

[0101] The output module is configured to control the constant power output of the BOOST converter using the robust sliding mode control structure.

[0102] This invention also provides an electronic device, comprising:

[0103] One or more processors;

[0104] A memory is configured to store computer-executable instructions, which, when executed, cause the processor to perform the robust sliding mode control method for a BOOST converter under constant power load as described above.

[0105] This invention also provides a storage medium for storing computer-executable instructions, which, when executed, implement the steps of the robust sliding mode control method for a BOOST converter under constant power load as described above.

[0106] It should be noted that the computer-readable medium disclosed herein may be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium may be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0107] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A robust sliding mode control method for a BOOST converter under constant power load, characterized in that, include: S1. Establish a bivariate state-space model under the BOOST converter; S2. Based on the bivariate state-space model, a fuzzy controller is constructed within the robust sliding mode control framework, and a current compensation mechanism is introduced to obtain the robust sliding mode control model. S3. Based on the robust sliding mode control model, establish the robust sliding mode control structure; S4. The robust sliding mode control structure is used to control the constant power output of the BOOST converter.

2. The robust sliding mode control method for a BOOST converter under constant power load according to claim 1, characterized in that, S1 specifically includes: Based on the state variables of the BOOST converter circuit and the switch conduction state, a bivariate state-space model in BOOST mode is established. The state variables of the BOOST converter include inductor current and output capacitor voltage.

3. The robust sliding mode control method for a BOOST converter under constant power load according to claim 1, characterized in that, The bivariate state-space model is as follows: In the formula, x1 is the inductor current, x2 is the capacitor voltage, E is the input voltage, P is the output power, D is the duty cycle, L is the inductance value, and C is the capacitance value.

4. The robust sliding mode control method for a BOOST converter under constant power load according to claim 1, characterized in that, The construction process of the robust sliding mode control model in S2 specifically includes: The control objective is to maintain the stability of the output voltage while keeping the power constant; therefore, the sliding surface S is designed as follows: S=x1x2-x r1 x r2 Where x1 is the inductor current, x2 is the capacitor voltage, and x r1 x is the inductor reference current. r2 This is the reference voltage for the capacitor; The sliding mode reaching law is: In the formula, λ and K are adjustable parameters that are greater than zero, and the symbolic function sgn(s) represents the switching control function; The inductor reference current is: In the formula, P is the constant power and E is the input voltage.

5. The robust sliding mode control method for a BOOST converter under constant power load according to claim 4, characterized in that, In step S2, to reduce the deviation, the inductor reference current is compensated, and the compensated inductor reference current x kr1 for: In the formula, r is the internal resistance.

6. The robust sliding mode control method for a BOOST converter under constant power load according to claim 5, characterized in that, The compensation mechanism in S2 is a fuzzy control rule, specifically including: When the output voltage is less than the reference voltage, that is, the internal resistance is less than its true value, in order to eliminate the deviation, the output voltage deviation is reduced by increasing the internal resistance. When the output voltage is greater than the reference voltage, that is, the internal resistance value is greater than its true value, the output voltage deviation is reduced by decreasing the internal resistance in order to eliminate the deviation.

7. The robust sliding mode control method for a BOOST converter under constant power load according to claim 1, characterized in that, The output D(t) of the robust sliding control structure in S3 is: Where λ and K are adjustable parameters greater than zero, the symbolic function sgn(s) represents the switching control function, x1 is the inductor current, x2 is the capacitor voltage, P is the constant power, E is the input voltage, L is the inductance value, and C is the capacitor value.

8. A robust sliding mode control system for a BOOST converter under constant power load, characterized in that, The system can be used to implement the robust sliding mode control method for a BOOST converter under constant power load as described in any of claims 1 to 7. The system includes: The first building module is configured to establish a bivariate state-space model under the BOOST converter; The second construction module is configured to construct a fuzzy controller within the robust sliding mode control framework based on the bivariate state space model, introduce a current compensation mechanism, and obtain a robust sliding mode control model. The structure determination module is configured to establish a robust sliding mode control structure based on the robust sliding mode control model. The output module is configured to control the constant power output of the BOOST converter using the robust sliding mode control structure.

9. An electronic device, characterized in that, include: One or more processors; A memory is configured to store computer-executable instructions, which, when executed, cause the processor to perform a robust sliding mode control method for a BOOST converter under constant power load as described in any one of claims 1-7.

10. A storage medium for storing computer-executable instructions, characterized in that, When the computer-executable instructions are executed, they implement the steps of the robust sliding mode control method for a BOOST converter under constant power load as described in any one of claims 1-7.

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