Nonlinear robust control method and device for dc-dc converter

Abstract

The application belongs to the technical field of power electronics, and provides a nonlinear robust control method and device for a DC-DC converter. The method comprises the following steps: obtaining an output voltage of the DC-DC converter and feeding back the output voltage to a terminal sliding mode controller; calculating a voltage error between a reference voltage and the output voltage of the DC-DC converter by the terminal sliding mode controller; generating a first control signal according to a preset fractional-order nonlinear sliding mode surface, a linear sliding mode surface and a relationship of the voltage error, and taking the first control signal as a reference current of a linear controller to form a voltage loop; obtaining an output current of the DC-DC converter and feeding back the output current to the linear controller; generating a second control signal by the linear controller in combination with the reference current and acting on a set power switch tube of the DC-DC converter to form a current loop; and finally realizing a double-loop nonlinear robust control of the DC-DC converter based on the reference voltage, the output voltage and the output current in cooperation, so as to ensure a good transient response.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and particularly relates to a nonlinear robust control method and device for a DC-DC converter. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] To improve the voltage transfer efficiency and transient response of DC-DC converters, changes in control and modulation strategies are typically employed. Regarding control strategies, traditional strategies include linear control and traditional sliding contact control. Traditional linear control results in slow dynamic response and overshoot when the load changes abruptly or the input voltage fluctuates. While current technologies combine linear control with traditional sliding contact control, these two approaches only address uncertainties in phase and control law matching, still exhibiting relatively slow convergence and chattering (i.e., high-frequency oscillations), leading to poor output voltage stability of the DC-DC converter. Summary of the Invention

[0004] To address the technical problems mentioned above, this invention provides a nonlinear robust control method and apparatus for a DC-DC converter, which can ensure the stability of the converter's output voltage.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a nonlinear robust control method for a DC-DC converter.

[0007] In one or more embodiments, a nonlinear robust control method for a DC-DC converter includes:

[0008] The output voltage of the DC-DC converter is acquired and fed back to the terminal sliding mode controller. The terminal sliding mode controller calculates the voltage error between the reference voltage and the output voltage of the DC-DC converter. Based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, a first control signal is generated and used as the reference current of the linear controller to form a voltage loop.

[0009] The output current of the DC-DC converter is obtained and fed back to the linear controller. The linear controller combines the reference current to generate a second control signal and applies it to the set power switch of the DC-DC converter to form a current loop. Finally, a dual-loop nonlinear robust control of the DC-DC converter based on the coordinated action of the reference voltage, the output voltage and the output current of the DC-DC converter is realized.

[0010] In other embodiments, a control method for a DC-DC converter is applicable to a dual-bridge DC-DC converter, the control method for the DC-DC converter comprising:

[0011] The output voltage of the DC-DC converter is acquired and fed back to the terminal sliding mode controller. The terminal sliding mode controller calculates the voltage error between the reference voltage and the output voltage of the DC-DC converter. Based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, a first control signal is generated and used as the reference current of the linear controller to form a voltage loop.

[0012] The output current of the DC-DC converter is obtained and fed back to the linear controller. The linear controller combines the reference current to generate and use it as the external shift ratio signal of the converter to form a current loop.

[0013] By utilizing the relationship between the preset inner shift ratio and the outer shift ratio in the phase shift controller, the inner shift ratio signal of the DC-DC converter is obtained, thereby realizing dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage and the output current of the DC-DC converter.

[0014] A second aspect of the present invention provides a DC-DC converter.

[0015] A DC-DC converter includes: a power switching transistor, an outer loop terminal sliding mode controller, and an inner loop linear controller;

[0016] The terminal sliding mode controller is used to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter, and to generate a first control signal based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, and use it as the reference current of the linear controller to form a voltage loop.

[0017] The linear controller is used to generate a second control signal based on the output current of the DC-DC converter and the reference current, and apply it to the set power switch of the DC-DC converter to form a current loop, thereby achieving dual-loop nonlinear robust control of the DC-DC converter based on the coordinated action of the reference voltage, the output voltage of the DC-DC converter, and the output current.

[0018] A DC-DC converter includes a power switch, a phase shift controller, an outer loop terminal sliding mode controller, and an inner loop linear controller.

[0019] The terminal sliding mode controller is used to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter, and to generate a first control signal based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, and use it as the reference current of the linear controller to form a voltage loop.

[0020] The linear controller is used to generate a second control signal based on the output current of the DC-DC converter and the reference current, and use it as an outward shift comparison signal of the DC-DC converter to form a current loop;

[0021] The phase-shift controller is used to obtain the inner shift ratio signal of the DC-DC converter by utilizing the relationship between the inner shift ratio and the outer shift ratio preset in the phase-shift controller, thereby realizing dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage and the output current of the DC-DC converter.

[0022] In one or more embodiments, a DC-DC converter as described above is coupled to a power generation system, an energy storage system, or an electric vehicle power supply.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) This invention uses a terminal sliding mode controller to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter. Then, based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, it uses the terminal sliding mode control strategy to obtain the first control signal as the reference current of the linear controller, forming a voltage loop. The linear controller is then used as the inner loop of the DC-DC converter to control the output current, realizing chatter-free robust control and dual-loop control that converge within a finite time. Under the condition of changing the input and output voltages and changing the load of the DC-DC converter, the stability of the output voltage is guaranteed.

[0025] (2) For dual-bridge DC-DC converters, the relationship between the inner shift ratio and the outer shift ratio is determined based on the phase shift controller and the topology of the DC-DC converter. Then, the terminal sliding mode controller, linear controller and phase shift controller are combined to calculate the inner shift ratio and the outer shift ratio of the converter. This improves the voltage transmission efficiency of the DC-DC converter and speeds up the response speed of the DC-DC converter, so that the DC-DC converter can quickly enter a stable state.

[0026] (3) The control strategy of the DC-DC converter of the present invention is suitable for the fast response charging and discharging requirements of the battery side in battery testing, and can be widely used in power generation systems, energy storage systems and electric vehicle charging and discharging fields.

[0027] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 This is the main circuit topology diagram of a dual active bridge converter (DAB);

[0030] Figure 2 This is a flowchart of the control method for the converter according to Embodiment 1 of the present invention;

[0031] Figure 3 This is a control principle diagram of the converter according to Embodiment 1 of the present invention;

[0032] Figure 4 This is a flowchart of the control method for the converter in Embodiment 2 of the present invention;

[0033] Figure 5 This is a control principle diagram of the converter in Embodiment 2 of the present invention;

[0034] Figure 6 This is the block diagram of a traditional single-phase-shift dual-closed-loop PI linear control for a DAB converter;

[0035] Figure 7 This is a block diagram of the TSM-PI dual closed-loop control for a single-phase shift DAB converter;

[0036] Figure 8 It refers to the transient response of the three controllers, PI-PI, SM-PI, and TSM-PI, when the input voltage increases;

[0037] Figure 9 It refers to the transient response of the three controllers, PI-PI, SM-PI, and TSM-PI, when the output voltage increases;

[0038] Figure 10 It refers to the transient response of three types of controllers: PI-PI, SM-PI, and TSM-PI, when the load changes.

[0039] Figure 11 This is a voltage and current waveform diagram of a dual-phase shift DAB converter. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] Terminology Explanation:

[0044] DAB: Dual Active Bridge;

[0045] PI: Proportional-Integral;

[0046] PID stands for Proportional-Integral-Derivative.

[0047] TSM: Terminal Sliding Mode;

[0048] EPS: Extended Phase-Shift.

[0049] The DC-DC converter topologies of this invention include, but are not limited to, buck, boost, buck-boost, flyback, and dual active bridge converters.

[0050] The following example uses a dual active bridge converter. When the duty cycle of the dual active bridge converter is calculated by combining a terminal sliding mode controller and a linear controller, the resulting duty cycle is used to implement single phase shift control (SPWM) of the dual active bridge converter to adjust the phase shift angle of the output voltage of the primary or secondary H-bridge.

[0051] Figure 1 The main circuit topology of a dual active bridge converter (DAB) is given. The DAB converter consists of two H-bridge converters (designated as H1 bridge converter and H2 bridge converter) connected by a transformer. Figure 1 In the high-frequency isolation transformer, the primary-to-secondary turns ratio is set to k, where k = 1:n; U ini1 and i2 represent the input voltage (DC power supply) and input current of the DAB converter, respectively; the H1 bridge converter consists of an H-bridge composed of power switches S1 to S4 and a supporting capacitor C1 connected in parallel on the input side; the H2 bridge converter consists of an H-bridge composed of power switches S5 to S8 and a filter capacitor C2 connected in parallel on the output side; where R represents the load, U... o i o These represent the output voltage and current of the DAB converter, respectively; L s U is the equivalent inductance of the transformer; ab For the primary side of the DAB converter; U cd i1 is the secondary voltage of the DAB converter; i2 is the secondary current of the DAB converter; i c This is the current flowing into the filter capacitor C2.

[0052] Figure 2 This invention provides a nonlinear robust control method for a DC-DC converter, which is generally applicable to various topologies. Figure 3 The following describes a converter, using a DAB converter as an example. Figure 2 The diagram shows the principle block diagram of the nonlinear robust control method for the DC-DC converter.

[0053] The following is combined with Figure 2 and Figure 3 The following is a detailed implementation process of the nonlinear robust control method for a DC-DC converter, which includes:

[0054] S11: Obtain the output voltage of the DC-DC converter and feed it back to the terminal sliding mode controller. The terminal sliding mode controller calculates the voltage error between the reference voltage and the output voltage of the DC-DC converter. Based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, it generates a first control signal and uses it as the reference current of the linear controller to form a voltage loop.

[0055] Figure 3 In the middle, the reference voltage is U ref Its value is the desired voltage matched to the specific reference of the DC-DC converter. The voltage error is set as e; the expression for the voltage error is:

[0056] e = U ref -U o (1)

[0057] The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error here is as follows:

[0058] The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the weighted sum of the integral of the voltage error and the voltage error.

[0059] Let the fractional-order nonlinear sliding surface be σ, and the linear sliding surface be s. The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error is expressed as follows:

[0060]

[0061] Where c1, c2, λ1, and λ2 are all numbers greater than zero, and are all weighted values, i.e., gains; p and q are both odd numbers, and satisfy...

[0062] By differentiating fractional-order nonlinear sliding surfaces and linear sliding surfaces, we can achieve the following: and All values ​​are 0, allowing the system to converge to the sliding surface within a finite time:

[0063]

[0064] Combining this with the energy equation of the DC-DC converter, the output of the terminal sliding mode controller is obtained, and this output is used as the input reference current I of the linear controller. SM :

[0065]

[0066] Where α is a constant coefficient that is greater than zero.

[0067] exist Figure 3 In this context, the linear controller is a PI controller.

[0068] It should be noted that the linear controller can also be a PID controller. Those skilled in the art can set it according to the actual situation, which will not be described in detail here.

[0069] S12: Obtain the output current of the DC-DC converter and feed it back to the linear controller. The linear controller combines the reference current to generate a second control signal and applies it to the set power switch of the DC-DC converter to form a current loop. Finally, it realizes the dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage and the output current of the DC-DC converter.

[0070] For example, Figure 3 The duty cycle obtained is used to achieve single-phase shift control of the dual active bridge converter, so as to adjust the phase shift angle of the secondary side H-bridge output voltage.

[0071] It is understood that in other embodiments, Figure 3The duty cycle obtained can also be used to adjust the phase shift angle of the primary H-bridge output voltage.

[0072] In addition, depending on the actual situation, the DAB converter can be converted to other converters for corresponding duty cycle calculation, which will not be elaborated here.

[0073] The traditional integral sliding mode formula is s=c1e+c2∫(e)dt; although this traditional integral sliding mode control can eliminate the smoothness of phase and control law, it can only handle the uncertainty of matching, the convergence speed is relatively slow, and there is chattering, that is, high-frequency oscillation, which leads to the inability to achieve accurate voltage in DAB voltage control, increases positioning error, and reduces control performance.

[0074] The terminal sliding mode controller in this embodiment adopts a fractional-order-based... The nonlinear sliding surface provides a faster convergence rate of the system state around the equilibrium point, i.e., finite-time convergence. Essentially, it makes the sliding surface σ and its (n-1)th derivative disappear, thus eliminating the flutter caused by discontinuous control at σ. n The alternating induction in the middle essentially eliminates the chattering effect. Therefore, the terminal sliding mode controller in this embodiment can obtain better sliding mode accuracy and achieve chatter-free robust control with finite-time convergence.

[0075] In this embodiment, the terminal sliding mode controller is used as the outer loop of the converter to control the output voltage, and the linear controller is used as the inner loop of the DC-DC converter to control the output current. Even when the input and output voltages of the DC-DC converter change and the load changes, the stability of the output voltage can still be guaranteed.

[0076] In another embodiment, the duty cycle of the converter is calculated by combining the terminal sliding mode control strategy, the linear control strategy, and the phase-shift control strategy. Here, the phase-shift control strategy can be either the extended phase-shift control (EPS) strategy or the dual phase-shift control (DPS) strategy. Figure 4 A flowchart of the corresponding nonlinear robust control method for the DC-DC converter is given. Figure 5 The following example of a converter is given: the DAB converter. Figure 4 The corresponding principle block diagram.

[0077] It should be noted here that, Figure 4 The proposed nonlinear robust control method for DC-DC converters is applicable to dual-bridge DC-DC converters, such as dual active bridge converters (DAB) and dual-bridge series resonant converters (DBSRC).

[0078] The following is combined Figure 4 and Figure 5 The specific implementation process of the terminal sliding mode dual-loop control method in this embodiment is given, which includes:

[0079] S21: Obtain the output voltage of the DC-DC converter and feed it back to the terminal sliding mode controller. The terminal sliding mode controller calculates the voltage error between the reference voltage and the output voltage of the DC-DC converter. Based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, it generates a first control signal and uses it as the reference current of the linear controller to form a voltage loop.

[0080] Figure 4 In the middle, the reference voltage is U ref Its value is the desired voltage matched to the specific reference of the converter. The voltage error is set as e; the expression for the voltage error is the same as that in formula (1).

[0081] The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error here is as follows:

[0082] The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the weighted sum of the integral of the voltage error and the voltage error.

[0083] Let the fractional-order nonlinear sliding surface be σ and the linear sliding surface be s. The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error is expressed as formula (2).

[0084] By differentiating fractional-order nonlinear sliding surfaces and linear sliding surfaces, we can achieve the following: and All are 0, so that the system can converge to the sliding surface in a finite time. The derivatives of the corresponding fractional nonlinear sliding surface and linear sliding surface are shown in Equation (3).

[0085] Combining this with the converter's energy equation:

[0086]

[0087] Among them, P o P and E represent average power and output power, respectively; C This represents the energy of the filter capacitor on the output side.

[0088] The reduced-order equation of the DAB converter is obtained as follows:

[0089]

[0090] Where I and U are the instantaneous current value on the secondary side of the DAB converter and the instantaneous voltage value across the load, respectively.

[0091] By combining the reduced-order equations of the DAB converter, the output of the terminal sliding mode control strategy is obtained, and this output is used as the input reference current I of the linear control strategy. SM As shown in formula (4).

[0092] exist Figure 5 In this context, the linear controller is a PI controller.

[0093] It should be noted that a PID controller can also be used as a linear controller. Those skilled in the art can set it up according to the actual situation, which will not be described in detail here.

[0094] S22: Obtain the output current of the DC-DC converter and feed it back to the linear controller. The linear controller combines the reference current to generate and use it as the external shift ratio signal of the converter to form a current loop.

[0095] S23: By utilizing the relationship between the preset inner shift ratio and the outer shift ratio in the phase shift controller, the inner shift ratio signal of the DC-DC converter is obtained, thereby realizing the dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage of the DC-DC converter, and the output current.

[0096] The relationship between the inner shift ratio and the outer shift ratio is characterized by the input voltage, output voltage of the converter, and the turns ratio of the transformer in the DC-DC converter.

[0097] In determining the relationship between the inner and outer shift ratios, different phase-shift control strategies control different converter topologies, resulting in different specific expressions for the inner and outer shift ratios. The following explanation uses the Extended Phase Shift Control (EPS) strategy to control a DAB converter as an example. Specifically, the EPS / Dual Phase Shift Control (DPS) strategy can determine the specific expressions for the inner and outer shift ratios for other dual-bridge converter topologies based on its control characteristics.

[0098] Figure 11 The voltage and current waveforms of the dual-phase shift DAB converter are given. Figure 11 It can be seen that there are six switching modes within one switching cycle. In the first switching mode, only power switches S1, S3, S6, and S7 are turned on, while the other power switches are turned off; in the second switching mode, only power switches S1, S2, S6, and S7 are turned on, while the other power switches are turned off; in the third switching mode, power switches S1, S2, S5, and S8 are turned on, while the other power switches are turned off; in the fourth switching mode, power switches S2, S4, S5, and S8 are turned on, while the other power switches are turned off; in the fifth switching mode, power switches S3, S4, S5, and S8 are turned on, while the other power switches are turned off; in the sixth switching mode, power switches S3, S4, S6, and S7 are turned on, while the other power switches are turned off.

[0099] Under the Extended Phase Shift Control (EPS) strategy, the inductor current of the DAB converter can be expressed as:

[0100]

[0101] Average power (P) delivered using EPS modulation o ) is represented as:

[0102]

[0103] Where n represents the transformer turns ratio, Ls represents the equivalent inductance, f represents the switching frequency, and D1 and D2 are the inner and outer shift ratios of the DAB converter, respectively.

[0104] The relationship between D1 and D2 is as follows:

[0105]

[0106] Where k is represented by the input and output voltages of the DAB converter and n.

[0107] In this embodiment, the internal and external phase shift ratios are adjusted using an EPS control strategy, which reduces the backhaul power and improves the conversion efficiency.

[0108] This embodiment combines PI control strategy with voltage-current dual closed-loop control, ensuring the stability of output voltage and improving dynamic response speed. It can still maintain robust dynamic performance under different input and output conditions, thus improving the stability of the system.

[0109] The two-level DAB under the control method of this embodiment was simulated. The DAB circuit parameters and simulation parameters are shown in Table 1 and Table 2, respectively.

[0110] Table 1 Simulation Parameters

[0111]

[0112]

[0113] Table 2 Controller Parameters

[0114] parameter <![CDATA[c1]]> 5 <![CDATA[c2]]> 40.521 <![CDATA[λ1]]> 0.03 <![CDATA[λ2]]> 15 p 7 q 5 <![CDATA[K p ]]> 0.1 <![CDATA[K i ]]> 0.1 α <![CDATA[1×10 -7 ]]>

[0115] Figure 6 This is a block diagram of a traditional single-phase-shift dual-closed-loop PI linear control for a DAB converter; Figure 6 Two PI controllers are used to realize traditional single-phase-shifting dual-closed-loop PI linear control. Figure 7 This is a block diagram of the TSM-PI dual closed-loop control for a single-phase shift DAB converter according to an embodiment of the present invention.

[0116] Figure 8 The transient responses of three controllers—PI-PI, SM-PI, and TSM-PI—are presented when the input voltage increases. Figure 9 The transient responses of three controllers—PI-PI, SM-PI, and TSM-PI—are presented when the output voltage increases. Figure 10 The transient responses of three controllers—PI-PI, SM-PI, and TSM-PI—are presented when the load changes.

[0117] exist Figure 8 In (a) of the diagram, when the input voltage increases from 80V to 100V, the PI-PI controller changes the input voltage U. in During this period, the output voltage U o During the restabilization process, a voltage fluctuation of 1V will occur. Figure 8 In (b) of the diagram, when the input voltage increases from 80V to 100V, the SM-PI controller adjusts the input voltage U... in During this period, the output voltage U o During the restabilization process, a voltage fluctuation of 3V will occur. Figure 8 In (c) of the diagram, when the input voltage increases from 80V to 100V, the TSM-PI controller adjusts the input voltage U... in During this period, the output voltage U o During the restabilization process, the amplitude of voltage fluctuations is almost zero.

[0118] exist Figure 9 In (a) of the diagram, when the output voltage increases from 90V to 120V, the PI-PI controller sets the output voltage U... o The re-stabilization response time is 4ms. Figure 9 In (b), when the output voltage increases from 90V to 120V, the SM-PI controller sets the output voltage U... o The re-stabilization response time is 15ms. Figure 9 In step (c), when the output voltage increases from 90V to 120V, the TSM-PI controller sets the output voltage U... o The re-stabilization response time is 3.5ms.

[0119] exist Figure 10 In (a) of the diagram, when the load decreases from 30Ω to 15Ω, the PI-PI controller adjusts the input voltage U. in During this period, the output voltage U o During the restabilization process, a voltage fluctuation of 7V will occur, with a response time of 80ms. Figure 10 In (b), when the load decreases from 30Ω to 15Ω, the SM-PI controller adjusts the input voltage U. in During this period, the output voltage Uo During the restabilization process, a voltage fluctuation of 6.6V will occur, with a response time of 2ms. Figure 10 In (c), when the load decreases from 30Ω to 15Ω, the TSM-PI controller operates at a variable input voltage U. in During this period, the output voltage U o During the restabilization process, a voltage fluctuation of 5V will occur, with a response time of 2ms.

[0120] A comparison of response speed and output voltage stability shows that the TSM-PI controller of this invention is faster and has no overshoot.

[0121] In one or more embodiments, a DC-DC converter is also provided, comprising: a power switch, an outer loop terminal sliding mode controller, and an inner loop linear controller;

[0122] The terminal sliding mode controller is used to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter, and to generate a first control signal based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, and use it as the reference current of the linear controller to form a voltage loop.

[0123] The linear controller is used to generate a second control signal based on the output current of the DC-DC converter and the reference current, and apply it to the set power switch of the DC-DC converter to form a current loop, thereby achieving dual-loop nonlinear robust control of the DC-DC converter based on the coordinated action of the reference voltage, the output voltage of the DC-DC converter, and the output current.

[0124] The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error is as follows:

[0125] The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the weighted sum of the integral of the voltage error and the voltage error.

[0126] It should be noted here that the linear controller is either a PI controller or a PID controller.

[0127] In other embodiments, a DC-DC converter is also provided, which includes a power switch, a phase shift controller, an outer loop terminal sliding mode controller and an inner loop linear controller.

[0128] The terminal sliding mode controller is used to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter, and to generate a first control signal based on the relationship between the preset fractional-order nonlinear sliding surface, the linear sliding surface and the voltage error, and use it as the reference current of the linear controller to form a voltage loop.

[0129] The linear controller is used to generate a second control signal based on the output current of the DC-DC converter and the reference current, and use it as an outward shift comparison signal of the DC-DC converter to form a current loop;

[0130] The phase-shift controller is used to obtain the inner shift ratio signal of the DC-DC converter by utilizing the relationship between the inner shift ratio and the outer shift ratio preset in the phase-shift controller, thereby realizing dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage and the output current of the DC-DC converter.

[0131] The DC-DC converter topology in this embodiment is a dual-bridge converter, such as a dual active bridge converter (DAB) or a dual-bridge series resonant converter (DBSRC).

[0132] The DC-DC converter described above can be applied to electric vehicle charging stations. For example, an electric vehicle charging station includes a bidirectional isolated AC-DC input stage, the DC-DC converter of this invention, and an intermediate battery storage system. The intermediate battery storage system provides the energy required for ultra-fast charging, avoids grid power ripple, and can also be used in smart grid applications. The intermediate storage battery has a higher energy capacity; during ultra-fast charging of the vehicle battery, the maximum discharge current of each intermediate storage battery does not exceed 3C-4C, enabling a long lifespan for the fixed battery. The AC-DC input stage can consist of a T-type inverter and a DC-DC converter system, providing isolation and balancing of the fixed battery voltage.

[0133] In other embodiments, when the DC-DC converter is also a bidirectional DC-DC converter, it can also be applied to power generation systems. Taking a solar photovoltaic power generation system as an example, when there is sufficient sunlight, photovoltaic panels generate a large amount of electrical energy. However, due to variations in sunlight intensity and duration, the output power of the photovoltaic panels also fluctuates. To solve this problem, a bidirectional DC-DC converter can be combined with an energy storage device (such as a battery) to achieve energy storage and regulation. When the output power of the photovoltaic panels exceeds the load demand, the excess electrical energy is stored in the battery; when the output power of the photovoltaic panels is insufficient, the battery supplies power to the load through the bidirectional DC-DC converter. This energy storage and release process not only ensures the stable operation of the power system but also improves energy utilization efficiency.

[0134] In other embodiments, when the DC-DC converter is also a bidirectional DC-DC converter, it can also be applied to energy storage systems. The bidirectional DC-DC converter controls the output voltage and current by adjusting the duty cycle of the switching devices (i.e., the ratio of the switching device's on-time to the cycle time). In charging mode, the converter converts the high-voltage DC power from the grid into low-voltage DC power suitable for charging the energy storage device; in discharging mode, the converter converts the low-voltage DC power from the energy storage device into the high-voltage DC power required by the grid. This flexible energy conversion method makes the bidirectional DC-DC converter a promising candidate for applications in energy storage systems. In distributed energy systems, the bidirectional DC-DC converter can achieve complementarity and optimized utilization between different energy forms. For example, in microgrids, the converter can integrate and efficiently utilize multiple renewable energy sources such as solar and wind power; in smart buildings, the converter can achieve energy exchange and optimized management between solar power generation, energy storage devices, and the grid. In electric vehicles, the bidirectional DC-DC converter can achieve energy exchange between the power battery and the grid, providing stable power support for the electric vehicle. Meanwhile, during regenerative braking, the converter can also recover braking energy, improving energy utilization efficiency.

[0135] It should be noted that, in other embodiments, the converter of the present invention can also be applied to other electronic devices for power conversion, as needed by those skilled in the art.

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nonlinear robust control method for a DC-DC converter, characterized in that, include: The output voltage of the DC-DC converter is acquired and fed back to the terminal sliding mode controller. The terminal sliding mode controller calculates the voltage error between the reference voltage and the output voltage of the DC-DC converter. Based on the preset relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error, a first control signal is generated and used as the reference current for the linear controller to form a voltage loop. The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error is as follows: The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the integral of the voltage error and the weighted sum of the voltage error. Let the fractional-order nonlinear sliding surface be... The linear sliding surface is The relationship between fractional-order nonlinear sliding surface, linear sliding surface, and voltage error is expressed as follows: in, , , and Both p and q are positive numbers and are weighted values, i.e., gains; both p and q are odd numbers and satisfy the following conditions: ; By differentiating fractional-order nonlinear sliding surfaces and linear sliding surfaces, we can achieve the following: and All values ​​are 0, allowing the system to converge to the sliding surface within a finite time: Combining this with the energy equation of the DC-DC converter, the output of the terminal sliding mode controller is obtained, and this output is used as the input reference current of the linear controller. : in, A constant coefficient that is greater than zero; The output current of the DC-DC converter is obtained and fed back to the linear controller. The linear controller combines the reference current to generate a second control signal and applies it to the set power switch of the DC-DC converter to form a current loop. Finally, a dual-loop nonlinear robust control of the DC-DC converter based on the coordinated action of the reference voltage, the output voltage and the output current of the DC-DC converter is realized.

2. A DC-DC converter, characterized in that, include: Power switching transistors, outer loop terminal sliding mode controllers, and inner loop linear controllers; The terminal sliding mode controller is used to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter, and to generate a first control signal based on the preset relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error, which serves as the reference current for the linear controller to form a voltage loop; the relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error is as follows: The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the integral of the voltage error and the weighted sum of the voltage error. Let the fractional-order nonlinear sliding surface be... The linear sliding surface is The relationship between fractional-order nonlinear sliding surface, linear sliding surface, and voltage error is expressed as follows: in, , , and Both p and q are positive numbers and are weighted values, i.e., gains; both p and q are odd numbers and satisfy the following conditions: ; By differentiating fractional-order nonlinear sliding surfaces and linear sliding surfaces, we can achieve the following: and All values ​​are 0, allowing the system to converge to the sliding surface within a finite time: Combining this with the energy equation of the DC-DC converter, the output of the terminal sliding mode controller is obtained, and this output is used as the input reference current of the linear controller. : in, A constant coefficient that is greater than zero; The linear controller is used to generate a second control signal based on the output current of the DC-DC converter and the reference current, and apply it to the set power switch of the DC-DC converter to form a current loop, thereby achieving dual-loop nonlinear robust control of the DC-DC converter based on the coordinated action of the reference voltage, the output voltage of the DC-DC converter, and the output current.

3. A control method for a DC-DC converter, characterized in that, A control method for a dual-bridge DC-DC converter, comprising: The output voltage of the DC-DC converter is acquired and fed back to the terminal sliding mode controller. The terminal sliding mode controller calculates the voltage error between the reference voltage and the output voltage of the DC-DC converter. Based on the preset relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error, a first control signal is generated and used as the reference current for the linear controller to form a voltage loop. The relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error is as follows: The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the integral of the voltage error and the weighted sum of the voltage error. Let the fractional-order nonlinear sliding surface be... The linear sliding surface is The relationship between fractional-order nonlinear sliding surface, linear sliding surface, and voltage error is expressed as follows: in, , , and Both p and q are positive numbers and are weighted values, i.e., gains; both p and q are odd numbers and satisfy the following conditions: ; By differentiating fractional-order nonlinear sliding surfaces and linear sliding surfaces, we can achieve the following: and All values ​​are 0, allowing the system to converge to the sliding surface within a finite time: Combining this with the energy equation of the DC-DC converter, the output of the terminal sliding mode controller is obtained, and this output is used as the input reference current of the linear controller. : in, A constant coefficient that is greater than zero; The output current of the DC-DC converter is obtained and fed back to the linear controller. The linear controller combines the reference current to generate and use it as the external shift ratio signal of the converter to form a current loop. By utilizing the relationship between the preset inner shift ratio and the outer shift ratio in the phase shift controller, the inner shift ratio signal of the DC-DC converter is obtained, thereby realizing dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage and the output current of the DC-DC converter.

4. The control method for the DC-DC converter as described in claim 3, characterized in that, The phase-shifting controller is an extended phase-shifting controller or a dual phase-shifting controller.

5. A DC-DC converter, characterized in that, This includes power switching transistors, phase shift controllers, outer loop terminal sliding mode controllers, and inner loop linear controllers; The terminal sliding mode controller is used to calculate the voltage error between the reference voltage and the output voltage of the DC-DC converter, and to generate a first control signal based on the preset relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error, which serves as the reference current for the linear controller to form a voltage loop; the relationship between the fractional-order nonlinear sliding surface, the linear sliding surface, and the voltage error is as follows: The fractional-order nonlinear sliding surface is the weighted sum of the fractional integral of the linear sliding surface and the linear sliding surface; the linear sliding surface is the integral of the voltage error and the weighted sum of the voltage error. Let the fractional-order nonlinear sliding surface be... The linear sliding surface is The relationship between fractional-order nonlinear sliding surface, linear sliding surface, and voltage error is expressed as follows: in, , , and Both p and q are positive numbers and are weighted values, i.e., gains; both p and q are odd numbers and satisfy the following conditions: ; By differentiating fractional-order nonlinear sliding surfaces and linear sliding surfaces, we can achieve the following: and All values ​​are 0, allowing the system to converge to the sliding surface within a finite time: Combining this with the energy equation of the DC-DC converter, the output of the terminal sliding mode controller is obtained, and this output is used as the input reference current of the linear controller. : in, A constant coefficient that is greater than zero; The linear controller is used to generate a second control signal based on the output current of the DC-DC converter and the reference current, and use it as an outward shift comparison signal of the DC-DC converter to form a current loop; The phase-shift controller is used to obtain the inner shift ratio signal of the DC-DC converter by utilizing the relationship between the inner shift ratio and the outer shift ratio preset in the phase-shift controller, thereby realizing dual-loop nonlinear robust control of the DC-DC converter based on the coordination of the reference voltage, the output voltage and the output current of the DC-DC converter.

6. A DC-DC converter as described in claim 2 or 5, characterized in that, The DC-DC converter is coupled to a power generation system, energy storage system, or electric vehicle power supply.

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