DC-DC converter control method and system based on adaptive droop control

Abstract

The invention belongs to but is not limited to the technical field of electrical control, and particularly relates to a DC-DC converter control method and system based on adaptive droop control, and the method comprises the steps: deducing a corresponding mathematical model before designing a controller of an interleaved multi-level boost converter; the original nonlinear model can be converted into a regular linear form by using the new state variable; the converted reduced-order model is equivalent to the differential homomorphism of the reduced-order model, a control target can be changed, and the total storage energy gradually tracks a reference value of the reduced-order model; aiming at a state variable and a disturbance quantity in an established system model, designing a self-adaptive sliding-mode observer which can compensate a disturbance influence in a feedforward mode; controlling a state variable by using a sliding mode controller based on a disturbance observer; a phase current balance compensator is designed, wherein simple and effective phase current balance compensation is adopted in a closed-loop interleaving multi-level boost converter system; a typical distributed control strategy, namely droop control, is added in the system.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the field of electrical control technology, and in particular relates to a DC-DC converter control method and system based on adaptive droop control. Background Art

[0002] As the global energy crisis and environmental problems are increasing day by day, renewable energy sources such as fuel cells, photovoltaic power generation and wind power are developing continuously and are widely used in more-electric aircraft technology. Among them, fuel cells are clean, efficient and low-noise, but their low output voltage and "soft" output voltage characteristics make it difficult to meet the requirements of DC bus voltage. Therefore, in order to connect the fuel cell to the DC bus, a high boost DC-DC converter is required, and it should have low input current ripple to extend the life of the fuel cell and improve the working efficiency. The interleaved parallel multi-level boost converter can operate under low input current ripple and high input current saturation boundary, and has high boost gain, self-voltage balancing characteristics and low component voltage stress. It is suitable for the interface converter of the fuel cell in the DC microgrid of more-electric aircraft.

[0003] Many active loads in the MUAC DC microgrid system are constant power loads, such as motor drives. Constant power loads have the characteristics of negative incremental impedance and high nonlinearity, which will significantly affect the system stability. In addition, the high bandwidth characteristics of constant power loads and their potential large power changes will bring large signal interference to the system, further affecting the stability of the system. Therefore, in order to reduce the negative impact of constant power loads on the DC microgrid and ensure the stability of the system, it is particularly important to design a control scheme for the source-side interface converter such as the interleaved parallel multi-level boost converter.

[0004] In recent years, scholars have developed some advanced nonlinear control technologies to maintain the large signal stability of DC microgrids with constant power load systems, such as sliding mode control, model predictive control, passivity control, backstepping control, etc. They have certain advantages such as robustness, stability, and flexibility. However, they are mainly used in traditional DC-DC converters, and the system model is relatively complex.

[0005] In a DC microgrid, DC-DC converters are connected in parallel, and how to achieve accurate power distribution between each converter is a key issue. Since DC power sources are relatively dispersed and inconvenient to communicate, droop control that only uses local information without global communication can achieve high-reliability power distribution and meet the needs of DC microgrids.

[0006] In view of the above analysis, the technical problems that need to be solved urgently in the existing technology are: the existing large-signal-based control strategy is mainly used for traditional buck or boost converters, and the modeling process of the DC microgrid and complex converter interface and the corresponding large-signal-based control strategy need further research. At the same time, the existing control strategy rarely considers the situation where the load carried by the staggered parallel multi-level boost converter system is a constant power load, and there is little research on the stability of the staggered parallel multi-level boost converter system under large-signal interference such as load disturbance. In addition, how to achieve accurate power distribution between the parallel converters is a very important issue. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a DC-DC converter control method and system based on adaptive droop control, which is used to provide a control strategy based on adaptive droop to stabilize a DC microgrid system interfaced with an interleaved parallel multi-level boost converter, which not only ensures the steady-state operation of the system under constant power conditions, but also enhances the robustness of the system while meeting the rapidity requirements.

[0008] The present invention is implemented as follows: a DC-DC converter control method based on adaptive droop control, comprising:

[0009] S1, establish a reduced-order model of the interleaved parallel multilevel boost converter: before designing the controller of the interleaved parallel multilevel boost converter, its corresponding mathematical model is derived; considering the high complexity and cascade structure of the interleaved parallel multilevel boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model; and the M-phase interleaved network is transformed into a single-phase network equivalent to an input inductor, and the generalized reduced-order model of the interleaved parallel multilevel boost converter is obtained;

[0010] S2, transform the established reduced-order model: the derived reduced-order model of the interleaved parallel multilevel boost converter is not convenient for controller design due to its inherent nonlinear characteristics; considering the stored energy and input power of the interleaved parallel multilevel boost converter, the original nonlinear model can be transformed into a regular linear form by using new state variables; the transformed reduced-order model is equivalent to its differential isomorphism, which can change the control target so that the total stored energy asymptotically tracks its reference value;

[0011] S3, design of adaptive sliding mode observer: design of adaptive sliding mode observer based on the state variables and disturbances in the established system model, which can compensate for disturbances in a feedforward manner;

[0012] S4, sliding mode controller design: Use a sliding mode controller based on a disturbance observer to control the state variables; the addition of a disturbance observer can improve the response speed of the control system to external disturbances; according to the sliding mode control theory, the sliding mode surface and sliding mode control law of the sliding mode control are obtained;

[0013] S5, Phase current balance compensator design: Due to the deviation of circuit parameters and duty cycle, using the total input current as the state variable may lead to the problem of imbalance between phase currents, increase the ripple of input current, and reduce the conversion efficiency. To solve these problems, a simple and effective phase current balance compensation is adopted in the closed-loop interleaved parallel multi-level boost converter system.

[0014] S6, adding droop control: In order to achieve accurate power distribution between various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

[0015] In order to achieve accurate power distribution among various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

[0016] Furthermore, the mathematical model of the interleaved parallel multi-level boost converter system obtained in S1 based on the state space averaging method is:

[0017]

[0018] Where: M is the number of inductors in the interleaved network; i Li Indicates that the current passes through the i th The inductor phase, i.e. Li(i=1, 2, ···, M)E represents the nominal value of the input voltage, v c1 represents the voltage of the first output capacitor (C1) of the voltage multiplier (VM) network, d i is the duty cycle of the first phase;

[0019] The M-phase interleaved network is equivalent to an input inductor of L eq The generalized reduced-order model of the interleaved multilevel boost converter is obtained by using a single-phase network:

[0020]

[0021] Among them, i o is the output current, represents the DC bus voltage, C represents the value of the capacitor in the N-level VM network, L eq =L / M is the equivalent input inductance.

[0022] Further, S2 is specifically:

[0023] Convert the original nonlinear model into a regular linear form:

[0024]

[0025] Wherein, x1 represents the nominal value of the total energy stored in the converter; x2 represents the converter input power, and H = N + M (N-1);

[0026] Time derivative of the new state variable:

[0027]

[0028] Among them, v represents the intermediate control law; u1 and u2 are unmeasurable disturbances, and the corresponding expressions are:

[0029]

[0030] The expression of the actual control law d is:

[0031]

[0032] After model conversion, the reduced-order model is equivalent to its differential isomorphism, which changes the control target so that the total stored energy x1 asymptotically tracks its reference value

[0033] Furthermore, the adaptive sliding mode observer obtained in S3 is:

[0034]

[0035] in, for u i The estimated value of ui is the disturbance error, k ui is the adaptive gain, γ ui A user-defined positive scalar.

[0036] Further, S4 is specifically:

[0037] The designed sliding surface is:

[0038] s x =a x e x1 +e x2

[0039] Among them, α x is a positive constant;

[0040] Using the estimation of the adaptive sliding mode observer, the designed sliding mode control rate is:

[0041]

[0042] Among them, K s1 and K s2is the positive SMC gain.

[0043] Further, S5 is specifically:

[0044] The proportional integral (PI) technology is used to design the phase current balance compensator, and its expression is:

[0045]

[0046] in, k p and k i is the positive controller gain.

[0047] Furthermore, the adaptive droop control expression in S6 is:

[0048]

[0049] Another object of the present invention is to provide a DC-DC converter control system based on adaptive droop control for implementing the DC-DC converter control method based on adaptive droop control, comprising:

[0050] Reduced-order model building module: Before designing the controller of the interleaved parallel multilevel boost converter, its corresponding mathematical model is derived; considering the high complexity and cascade structure of the interleaved parallel multilevel boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model; and the M-phase interleaved network is transformed into a single-phase network equivalent to an input inductor to obtain a generalized reduced-order model of the interleaved parallel multilevel boost converter;

[0051] Reduced-order model conversion module: The derived reduced-order model of the interleaved parallel multilevel boost converter is not convenient for controller design due to its inherent nonlinear characteristics; considering the stored energy and input power of the interleaved parallel multilevel boost converter, the original nonlinear model can be converted into a regular linear form using new state variables; the converted reduced-order model is equivalent to its differential isomorphism, which can change the control target so that the total stored energy asymptotically tracks its reference value;

[0052] Adaptive sliding mode observer design module: Design an adaptive sliding mode observer based on the state variables and disturbances in the system model, which can compensate for disturbances in a feedforward manner;

[0053] Sliding mode controller design module: Use the sliding mode controller based on disturbance observer to control the state variables; the addition of disturbance observer can improve the response speed of the control system to external disturbances; according to the sliding mode control theory, the sliding mode surface and sliding mode control law of sliding mode control are obtained;

[0054] Phase current balance compensator design module: Due to the deviation of circuit parameters and duty cycle, using the total input current as the state variable may lead to the problem of imbalance between phase currents, increase the ripple of input current, and reduce conversion efficiency. To solve these problems, a simple and effective phase current balance compensation is adopted in the closed-loop interleaved parallel multi-level boost converter system.

[0055] Droop control addition module: In order to achieve accurate power distribution between various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

[0056] Another object of the present invention is to provide a computer device, the computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the DC-DC converter control method based on adaptive droop control.

[0057] Another object of the present invention is to provide an information data processing terminal, which includes the DC-DC converter control system based on adaptive droop control.

[0058] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0059] First, the present invention aims at the deficiencies of the prior art and provides a large signal stabilization control strategy based on adaptive droop to stabilize the multi-electric aircraft DC microgrid system with staggered parallel multi-level boost converter interface. It not only ensures the steady-state operation of the system under constant power conditions, but also effectively eliminates the influence of constant power load on DC bus voltage, realizes the current balance and voltage balance between phases in the converter, and has strong system robustness while meeting the rapidity requirements. Moreover, it can maintain the bus voltage and realize accurate power distribution of each unit without the need for communication between the power supply units.

[0060] Second, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0061] (1) The positive technical effects and significant technical advances of the present invention also include:

[0062] 1. A unified reduced-order model of the interleaved parallel multilevel boost converter is obtained. Its order does not change with the order of the generalized model, the switching capacitor level and the interleaving phase, and is fixed at 2nd order.

[0063] 2. For the DC microgrid system with interleaved parallel multi-level boost converters, a sliding mode control strategy based on an adaptive sliding mode observer is designed to ensure the large signal stability of the system. Compared with the existing methods, the proposed control strategy can handle a wider range of disturbances and improve the robustness of the regulated system to unknown disturbances.

[0064] 3. A phase current balance compensator based on proportional integral is designed to keep the current equal between phases.

[0065] 4. A distributed control strategy between multiple parallel converters in a DC microgrid system is designed, and the droop control method is used for each converter to achieve the goals of current sharing and maintaining bus voltage.

[0066] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0067] Existing large-signal-based nonlinear control methods are mainly used for traditional buck or boost converters. The modeling process of the DC microgrid and complex converter interface designed by the present invention and the corresponding large-signal-based control strategy fill this gap. The technical solution adopted by the present invention is: Advanced control method: The present invention adopts a sliding mode control method based on an adaptive disturbance observer, which can more effectively cope with large-signal disturbances, improve control accuracy and system response speed, and adaptive droop control can more accurately achieve current sharing between distributed power generation units and improve the accuracy of power distribution.

[0068] (3) The technical solution of the present invention has significant innovation and practicality in the technical field of the industry at home and abroad. The research of the present invention is aimed at staggered parallel multi-level boost converters, focusing on studying the stability of staggered parallel multi-level boost converters in DC microgrids under large signal interference conditions such as constant power load and input voltage fluctuations. In order to simplify the design of the control scheme, the present invention obtains a reduced-order model of the converter, which reduces the complexity of the converter model and proposes a new design idea for the optimization of the control scheme. The control method used can make the output voltage quickly follow its reference value, significantly improving the system response speed and stability. Based on the complex converter controller, the present invention adopts adaptive droop coefficient allocation, which can better perform bus voltage regulation and precise power distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is a typical DC microgrid structure diagram corresponding to the present invention provided by an embodiment of the present invention;

[0070] Figure 2 1 is a topological structure diagram of an M-phase N-level interleaved parallel multi-level boost converter circuit provided by an embodiment of the present invention;

[0071] Figure 3is a flow chart of a DC-DC converter control method based on adaptive droop control provided by an embodiment of the present invention;

[0072] Figure 4 is a DC bus voltage waveform diagram when the input voltage of the present invention changes provided by an embodiment of the present invention;

[0073] Figure 5 It is a DC bus voltage waveform diagram when the load power of the present invention changes provided by an embodiment of the present invention;

[0074] Figure 6 is a power distribution waveform diagram of the converter of the present invention provided by an embodiment of the present invention;

[0075] Figure 7 It is a structural diagram of a DC-DC converter control system based on adaptive droop control provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0077] The present invention is based on a typical DC microgrid, such as Figure 1 shown. Figure 2 This is a topological structure diagram of an M-phase N-level interleaved parallel multi-level boost converter circuit corresponding to the present invention.

[0078] The controller design method of the DC microgrid interleaved parallel multi-level boost converter based on the adaptive observer provided in the embodiment of the present invention specifically comprises the following steps:

[0079] Step 1: Build a reduced-order model of the interleaved multilevel boost converter

[0080] Before designing the controller of the interleaved parallel multilevel boost converter, its corresponding mathematical model should be derived. Considering the high complexity and cascade structure of the interleaved parallel multilevel boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model. The M-phase interleaved network can be transformed into a single-phase network equivalent to an input inductor. Therefore, a generalized reduced-order model of the interleaved parallel multilevel boost converter can be obtained.

[0081] Step 2: Transform the established reduced-order model

[0082] The derived reduced-order model of the interleaved parallel multilevel boost converter is not convenient for controller design due to its inherent nonlinear characteristics. Considering the stored energy and input power of the interleaved parallel multilevel boost converter, the original nonlinear model can be transformed into a regular linear form using new state variables. The transformed reduced-order model is equivalent to its differential isomorphism and can change the control objective so that the total stored energy asymptotically tracks its reference value.

[0083] Step 3: Design an adaptive sliding mode observer

[0084] Aiming at the state variables and disturbances in the established system model, an adaptive sliding mode observer is designed, which can compensate for the disturbance effects in a feedforward manner.

[0085] Step 4: Sliding Mode Controller Design

[0086] The state variables are controlled by a sliding mode controller based on a disturbance observer. The addition of a disturbance observer can improve the response speed of the control system to external disturbances. According to the sliding mode control theory, the sliding mode surface and sliding mode control law of the sliding mode control are obtained.

[0087] Step 5: Phase current balance compensator design

[0088] Due to the deviation of circuit parameters and duty cycle, using the total input current as the state variable may lead to the problem of imbalance between phase currents, increase the ripple of input current and reduce conversion efficiency. To solve these problems, a simple and effective phase current balance compensation is adopted in the closed-loop interleaved parallel multi-level boost converter system.

[0089] Step 6: Adding Droop Control

[0090] In order to achieve accurate power distribution among various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

[0091] Figure 3 The system control block diagram of the present invention describes the main steps of the scheme of the present invention:

[0092] Before designing the controller, the corresponding mathematical model of the DC-DC converter should be derived. Considering the high complexity and cascade structure of the interleaved parallel multi-level boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model. The M-phase interleaved network can be transformed into a single-phase network equivalent to an input inductor. Therefore, a generalized reduced-order model of the interleaved parallel multi-level boost converter can be obtained.

[0093]

[0094] In formula (1), M is the number of inductors in the interleaved network; i Li Indicates that the current passes through the i th The inductor phase, i.e. Li(i=1, 2, ···, M)E represents the nominal value of the input voltage, v c1 represents the voltage of the first output capacitor (C1) of the voltage multiplier (VM) network, d i is the duty cycle of the first phase.

[0095] Assuming that each inductor has the same inductance L, and the PWM switching signal for each phase is generated using the same duty cycle d and the desired phase shift, the model given in (1) can be simplified to:

[0096]

[0097] In formula (2), is the total input current, L eq =L / M is the equivalent input inductance. Based on this, the M-phase interleaved network can be equivalent to an input inductance of L eq Therefore, a generalized reduced-order model of an interleaved multilevel boost converter can be obtained.

[0098]

[0099] In formula (3), i o is the output current, represents the DC bus voltage, and C represents the value of the capacitor in the N-level VM network.

[0100] Taking into account the deviation between the inductor and capacitor and the input source voltage in practical applications, the reduced-order model given in equation (3) is rewritten as:

[0101]

[0102] Step 2 is as follows:

[0103] Convert the original nonlinear model (3) into a regular linear form:

[0104]

[0105] In formula (5), x1 represents the nominal value of the total energy stored in the converter; x2 represents the converter input power, and H=N+M(N-1).

[0106] Combining equations (4) and (5), we get the time derivative of the new state variable:

[0107]

[0108] In formula (6), v represents the intermediate control law; u1 and u2 are unmeasurable disturbances, and their corresponding expressions are:

[0109]

[0110] The expression of the actual control law d is:

[0111]

[0112] After model transformation, the reduced-order model (4) is equivalent to its differential isomorphism (6), which changes the control objective so that the total stored energy x1 asymptotically tracks its reference value

[0113] According to formula (5), we can get:

[0114]

[0115] From the principle of input / output power balance, we can get:

[0116] i in (E+ΔE)=P out (10)

[0117] In formula (8), P out Represents the total output power of the converter.

[0118] Therefore, the total input current i in The reference value can be defined as:

[0119]

[0120] When the system is in steady state, the disturbance u1 is:

[0121] u 1ss =-v bus i o +i in ΔE=i in ΔE-P out (12)

[0122] Through the above analysis, and It can be determined as:

[0123]

[0124] Step 3 is as follows:

[0125] Define the following variables:

[0126]

[0127] In formula (14), and x i and u i The estimated value of h ui and λ ui (i=1,2) is a positive constant, and λ ui Satisfy the condition 0<λ ui <1.

[0128] Using the variables defined in equation (12), we design the estimated disturbance u i Adaptive sliding mode observer:

[0129]

[0130] Adaptive gain via:

[0131]

[0132] In formula (14),

[0133]

[0134] In formula (15), sgn(·) represents the sign (sgn) function, and the observer gain β ui , γ ui , η ui , σ 0ui , α 0ui , ε ui , τ ui and l ui A user-defined positive scalar.

[0135] Combining equation (6) and equation (12), we get the adaptive sliding mode observer:

[0136]

[0137] Step 4 is as follows:

[0138] In steady state, the disturbance equation can be obtained as:

[0139]

[0140] The control ratios are established using estimates of the following reference values ​​of the state variables:

[0141]

[0142] According to formula (18), the error variable is defined as:

[0143]

[0144] Combining equation (6) and equation (19), the designed sliding surface is:

[0145] s x =a x e x1 +e x2 (twenty two)

[0146] In formula (20), α x Is a normal number.

[0147] Using the estimation of the adaptive sliding mode observer, the designed sliding mode control rate is:

[0148]

[0149] In formula (21), K s1 and K s2 is the positive SMC gain.

[0150] Step 5 is as follows:

[0151] Considering that constant power load may cause oscillation in the DC microgrid system, the proportional integral (PI) technology is used to design the phase current balance compensator, and its expression is:

[0152]

[0153] In formula (22), k p and k i is the positive controller gain.

[0154] Step 6 is as follows:

[0155] Droop control is introduced in the DC microgrid system of the more-electric aircraft. When the droop coefficient is much larger than the line impedance, the relationship between the output current and the droop coefficient can be obtained as follows:

[0156]

[0157] In formula (25), i oi is the output current of each unit converter. oi The expected output current When they are inconsistent, the error between them is defined as:

[0158]

[0159] In formula (26), k i is the corresponding current ratio.

[0160] In order to achieve accurate power distribution between converters in the DC microgrid, PI control is used to continuously update the droop coefficient.

[0161] ΔR droop =k d (K pd (t)e i (t)+∫k id (t)e i (t)dt)(27)

[0162]

[0163] Design adaptive droop control expression as:

[0164]

[0165] like Figure 7 As shown, the DC-DC converter control system based on adaptive droop control provided by the embodiment of the present invention is characterized by comprising:

[0166] Reduced-order model building module: Before designing the controller of the interleaved parallel multilevel boost converter, its corresponding mathematical model is derived; considering the high complexity and cascade structure of the interleaved parallel multilevel boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model; and the M-phase interleaved network is transformed into a single-phase network equivalent to an input inductor to obtain a generalized reduced-order model of the interleaved parallel multilevel boost converter;

[0167] Reduced-order model conversion module: The derived reduced-order model of the interleaved parallel multilevel boost converter is not convenient for controller design due to its inherent nonlinear characteristics; considering the stored energy and input power of the interleaved parallel multilevel boost converter, the original nonlinear model can be converted into a regular linear form using new state variables; the converted reduced-order model is equivalent to its differential isomorphism, which can change the control target so that the total stored energy asymptotically tracks its reference value;

[0168] Adaptive sliding mode observer design module: Design an adaptive sliding mode observer based on the state variables and disturbances in the system model, which can compensate for disturbances in a feedforward manner;

[0169] Sliding mode controller design module: Use the sliding mode controller based on disturbance observer to control the state variables; the addition of disturbance observer can improve the response speed of the control system to external disturbances; according to the sliding mode control theory, the sliding mode surface and sliding mode control law of sliding mode control are obtained;

[0170] Phase current balance compensator design module: Due to the deviation of circuit parameters and duty cycle, using the total input current as the state variable may lead to the problem of imbalance between phase currents, increase the ripple of input current, and reduce conversion efficiency. To solve these problems, a simple and effective phase current balance compensation is adopted in the closed-loop interleaved parallel multi-level boost converter system.

[0171] Droop control addition module: In order to achieve accurate power distribution between various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

[0172] An application embodiment of the present invention provides a computer device, which includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor executes the steps of a DC-DC converter control method based on adaptive droop control.

[0173] An application embodiment of the present invention provides an information data processing terminal, which includes a DC-DC converter control system based on adaptive droop control.

[0174] 1. Specific application fields or related products of the present invention.

[0175] Example 1: Control of DC-DC converter for a DC microgrid system of a multi-electric aircraft

[0176] Background: In the technology of more electric aircraft, primary energy sources such as fuel cells are gradually used to replace traditional fuel generators in auxiliary power generation units. In the DC microgrid system of more electric aircraft, power sources such as fuel cells are connected to the bus through DC-DC converters. Due to the trend of aircraft electrification, the power electronics of airborne equipment has been reduced, which reduces the stability of the power system. It is necessary to design an effective stabilization control solution for the converter.

[0177] Example 2: Control of a high-gain DC-DC converter for an electric vehicle charger

[0178] Background: Electric vehicle technology currently has two major problems: low charging efficiency and short usable mileage. As a portable fast charger for electric vehicles, on-board high-gain DC-DC converters can solve the problem of electric vehicles' power outage endurance. Since the power electronics of on-board electrical equipment reduces the stability of the power system, it is necessary to design an effective stabilization control solution for the converter.

[0179] 2. Relevant evidence of the technical effects obtained by the embodiments of the present invention.

[0180] In MATLAB / Simulink, the control method proposed in the present invention is simulated and verified to confirm its effectiveness. All simulations are carried out under the condition of staggered parallel multi-level boost converter with constant power load. The important parameters of the controller used in the simulation are: the droop coefficient ratio of the three converters is 1:1:1; the bus voltage is 270V; and the converter input voltage is 50V.

[0181] First, verify the existence of a sudden change in input voltage. Figure 4 As shown, the input voltage amplitude changes in steps every 0.1s, and the proposed controller still stabilizes the output voltage at its reference value.

[0182] Then we verified the situation when the load power changes. Figure 5 As shown in the figure, the load power changes every 0.1s. After the output voltage fluctuates, it quickly returns to the reference value.

[0183] Figure 6 It is demonstrated that accurate power distribution can be achieved through adaptive droop control under the condition of multiple converter groups in parallel, with power distribution according to a droop coefficient ratio of 1:1:1.

[0184] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0185] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A DC-DC converter control method based on adaptive droop control, characterized in that: include: S1, establish the reduced-order model of the interleaved parallel multilevel boost converter: before designing the controller of the interleaved parallel multilevel boost converter, its corresponding mathematical model is derived; considering the high complexity and cascade structure of the interleaved parallel multilevel boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model; The M-phase interleaved network is transformed into a single-phase network equivalent to an input inductor, and the generalized reduced-order model of the interleaved parallel multi-level boost converter is obtained; S2, transform the established reduced-order model: the derived reduced-order model of the interleaved parallel multilevel boost converter is not convenient for controller design due to its inherent nonlinear characteristics; considering the stored energy and input power of the interleaved parallel multilevel boost converter, the original nonlinear model can be transformed into a regular linear form by using new state variables; the transformed reduced-order model is equivalent to its differential isomorphism, which can change the control target so that the total stored energy asymptotically tracks its reference value; S3, design of adaptive sliding mode observer: design of adaptive sliding mode observer based on the state variables and disturbances in the established system model, which can compensate for disturbances in a feedforward manner; S4, sliding mode controller design: Use a sliding mode controller based on a disturbance observer to control the state variables; the addition of a disturbance observer can improve the response speed of the control system to external disturbances; according to the sliding mode control theory, the sliding mode surface and sliding mode control law of the sliding mode control are obtained; S5, Phase current balance compensator design: Due to the deviation of circuit parameters and duty cycle, using the total input current as the state variable may lead to the problem of imbalance between phase currents, increase the ripple of input current, and reduce the conversion efficiency. To solve these problems, a simple and effective phase current balance compensation is adopted in the closed-loop interleaved parallel multi-level boost converter system. S6, adding droop control: In order to achieve accurate power distribution between various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system. In order to achieve accurate power distribution among various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

2. The DC-DC converter control method based on adaptive droop control according to claim 1, characterized in that: The mathematical model of the interleaved parallel multi-level boost converter system obtained in S1 based on the state space averaging method is: Where: M is the number of inductors in the interleaved network; i Li Indicates that the current passes through the i th The inductor phase, i.e., Li, i = 1, 2, ···, M, E represents the nominal value of the input voltage, v c1 represents the voltage of the first output capacitor of the voltage multiplier network, d i is the duty cycle of the first phase; The M-phase interleaved network is equivalent to an input inductor of L eq The generalized reduced-order model of the interleaved multilevel boost converter is obtained by using a single-phase network: Among them, i o is the output current, represents the DC bus voltage, C represents the value of the capacitor in the N-level VM network, L eq =L / M is the equivalent input inductance.

3. The DC-DC converter control method based on adaptive droop control according to claim 1, characterized in that: S2 is specifically: Convert the original nonlinear model into a regular linear form: Wherein, x1 represents the nominal value of the total energy stored in the converter; x2 represents the converter input power, and H = N + M (N-1); Time derivative of the new state variable: Among them, v represents the intermediate control law; u1 and u2 are unmeasurable disturbances, and the corresponding expressions are: The expression of the actual control law d is: After model conversion, the reduced-order model is equivalent to its differential isomorphism, which changes the control target so that the total stored energy x1 asymptotically tracks its reference value 4. The DC-DC converter control method based on adaptive droop control according to claim 1, characterized in that: The adaptive sliding mode observer obtained in S3 is: in, for u i The estimated value of ui is the disturbance error, k ui is the adaptive gain, γ ui A user-defined positive scalar.

5. The DC-DC converter control method based on adaptive droop control according to claim 1, characterized in that: S4 is specifically: The designed sliding surface is: s x =a x and x1 +and x2 Among them, α x is a positive constant; Using the estimation of the adaptive sliding mode observer, the designed sliding mode control rate is: Among them, K s1 and K s2 is the positive SMC gain.

6. The DC-DC converter control method based on adaptive droop control according to claim 1, characterized in that: S5 is as follows: The proportional integral (PI) technology is used to design the phase current balance compensator, and its expression is: in, k p and k i is the positive controller gain.

7. The DC-DC converter control method based on adaptive droop control according to claim 1, characterized in that: The adaptive droop control expression in S6 is:

8. A DC-DC converter control system based on adaptive droop control that implements the DC-DC converter control method based on adaptive droop control as claimed in any one of claims 1 to 7, characterized in that: include: Reduced-order model building module: Before designing the controller of the interleaved parallel multilevel boost converter, its corresponding mathematical model is derived; considering the high complexity and cascade structure of the interleaved parallel multilevel boost converter, the modeling process is divided into two steps. First, the M-phase interleaved network is analyzed using Kirchhoff's law to obtain its average model; and the M-phase interleaved network is transformed into a single-phase network equivalent to an input inductor to obtain the generalized reduced-order model of the interleaved parallel multilevel boost converter; Reduced-order model conversion module: The derived reduced-order model of the interleaved parallel multilevel boost converter is not convenient for controller design due to its inherent nonlinear characteristics; considering the stored energy and input power of the interleaved parallel multilevel boost converter, the original nonlinear model can be converted into a regular linear form using new state variables; the converted reduced-order model is equivalent to its differential isomorphism, which can change the control target so that the total stored energy asymptotically tracks its reference value; Adaptive sliding mode observer design module: Design an adaptive sliding mode observer based on the state variables and disturbances in the system model, which can compensate for disturbances in a feedforward manner; Sliding mode controller design module: Use the sliding mode controller based on disturbance observer to control the state variables; the addition of disturbance observer can improve the response speed of the control system to external disturbances; according to the sliding mode control theory, the sliding mode surface and sliding mode control law of sliding mode control are obtained; Phase current balance compensator design module: Due to the deviation of circuit parameters and duty cycle, using the total input current as the state variable may lead to the problem of imbalance between phase currents, increase the ripple of input current, and reduce conversion efficiency. To solve these problems, a simple and effective phase current balance compensation is adopted in the closed-loop interleaved parallel multi-level boost converter system. Droop control addition module: In order to achieve accurate power distribution between various ports in the DC microgrid, a typical decentralized control strategy, namely droop control, is added to the system.

9. A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the DC-DC converter control method based on adaptive droop control as claimed in any one of claims 1 to 7.

10. An information data processing terminal, comprising the DC-DC converter control system based on adaptive droop control according to claim 8.

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