Control Method and Converter Applied to Bidirectional DC-DC Converter Circuit

Abstract

The present application relates to a control method and a converter applied to a bidirectional DC-DC converter circuit. The control method is as follows: obtain a first control signal and directly apply the first control signal to the first switch and the fourth switch of the primary full-bridge circuit; shift the first control signal by 180° to obtain a second control signal and apply the second control signal to the second switch and the third switch of the primary full-bridge circuit; shift the first control signal by a target phase angle to obtain a third control signal and apply the third control signal to the fifth switch and the eighth switch of the secondary full-bridge circuit, where the target phase angle is determined by using the Lyapunov stability theory; shift the third control signal by 180° to obtain a fourth control signal and apply the fourth control signal to the sixth switch and the seventh switch of the secondary full-bridge circuit, which can provide stable voltage modulation and high-precision control, with fewer gain parameters, and can adapt to circuit parameter changes, improving the anti-interference ability and dynamic response performance.

Description

Technical Field

[0001] This application relates to the technical field of converter circuit control, and in particular, to a control method and a converter applied to a bidirectional DC-DC converter circuit. Background Art

[0002] In the control scheme of a bidirectional DC-DC converter, PI control is the most common control method, which adjusts the output voltage through proportional and integral links to keep it stable; sliding mode control, as a variable structure control, forces the system state to slide along the sliding mode surface through a sliding mode controller, having a faster dynamic response speed and stronger robustness; fuzzy logic control can handle parameter perturbations and uncertainties. By combining a fuzzy logic allocation strategy with linear PID or sliding mode control, the comprehensive performance of the control system can be improved.

[0003] However, for a traditional linear PI controller, it cannot appropriately adjust the gain when the circuit operating point changes. The look-up table method designed based on the nominal parameters of MLDDC can solve the problem of gain adjustment. However, the uncertainty of circuit parameters will affect the design of the look-up table method parameters; fuzzy control requires a lot of work to establish the input-output mapping relationship, and the stability of the fuzzy control closed-loop cannot be verified and proved; linear sliding mode control has problems of overshoot and large static error due to the absence of an integral term. Although single-integral sliding mode and double-integral sliding mode greatly reduce the static error, such controllers require 3 - 4 adjustable parameters, the parameter adjustment process is complex, and the stability conditions are harsh. Therefore, the above several control schemes all have corresponding problems and are not conducive to popularization and application. Summary of the Invention

[0004] Based on this, it is necessary to provide a control method and a converter applied to a bidirectional DC-DC converter circuit that can solve the above technical problems.

[0005] The above object of this application is achieved through the following technical solutions.

[0006] In the first aspect of this application, a control method applied to a bidirectional DC-DC converter circuit is provided. The bidirectional DC-DC converter circuit includes a primary full-bridge circuit, a magnetic coupling transformer, and a secondary full-bridge circuit connected in sequence. The primary full-bridge circuit includes a first switch, a second switch, a third switch, and a fourth switch; the secondary full-bridge circuit includes a fifth switch, a sixth switch, a seventh switch, and an eighth switch.

[0007] The control method is as follows: Obtain a first control signal and directly apply the first control signal to the first switch and the fourth switch of the primary full-bridge circuit; shift the first control signal by 180° to obtain a second control signal and apply the second control signal to the second switch and the third switch of the primary full-bridge circuit; shift the first control signal by a target phase angle to obtain a third control signal and apply the third control signal to the fifth switch and the eighth switch of the secondary full-bridge circuit, where the target phase angle is determined using the Lyapunov stability theory; shift the third control signal by 180° to obtain a fourth control signal and apply the fourth control signal to the sixth switch and the seventh switch of the secondary full-bridge circuit.

[0008] In one embodiment, the acquisition logic of the target phase angle is as follows: Based on the Fourier series of the switching function, establish a low-frequency harmonic model of the output voltage of the bidirectional DC-DC converter circuit and determine the output voltage dynamic equation; establish an error expression between the output voltage and the reference voltage, substitute the output voltage dynamic equation into the error expression to obtain an error dynamic equation; define a Lyapunov function and take the derivative, substitute the error dynamic equation into the differentiated Lyapunov function, and determine the global stability condition of the function according to the Lyapunov stability theory. Based on the global stability condition, determine the target phase angle.

[0009] In one embodiment, the output voltage dynamic equation is derived as follows: Based on the topological structure of the bidirectional DC-DC converter circuit, construct a differential equation.

[0010] The differential equation expression is: , where is the phase angle of the converter circuit, , is the impedance, , is the switching frequency, is the inductance value of the input inductor of the converter circuit, is the resistance value of the input inductor, is the cosine function related to the phase angle of the converter circuit, is the turns ratio of the magnetic coupling transformer, is the input voltage on the low-voltage side of the converter circuit, is the DC current of the converter circuit, is the output voltage of the converter circuit, is the value of the DC side capacitor of the converter circuit.

[0011] Assume , define the control variable as , where is the total phase shift angle. Substitute into and , , is the target phase angle.

[0012] Convert the cosine to sine through trigonometric functions to obtain . Substitute into the differential equation to obtain the output voltage dynamic equation: .

[0013] In one embodiment, the error dynamic equation is obtained as follows: Establish an error expression between the output voltage and the reference voltage of the bidirectional DC-DC converter circuit: , where is the output voltage of the converter circuit, is the reference voltage, is the error between the output voltage and the reference voltage of the converter circuit; Substitute the output voltage dynamic equation into the error expression to determine the error dynamic equation as .

[0014] In one embodiment, the method for determining the target phase angle includes:

[0015] Define the Lyapunov function as , and take the derivative of ;

[0016] Substitute the error dynamic equation into the derivative of the Lyapunov function to obtain:

[0017] ,

[0018] When the condition is satisfied, the global stability condition is determined as:

[0019] ;

[0020] Obtain the reaching law from the global stability condition:

[0021] ,

[0022] Solve the target phase angle from the reaching law:

[0023] .

[0024] In the second aspect of the present application, a converter is provided, including a bidirectional DC-DC converter circuit; The control method applied to the bidirectional DC-DC converter circuit described in the above embodiment is used to control the bidirectional DC-DC converter circuit.

[0025] The control method based on a non - linear backstepping controller in the embodiments of the present application is used for the control of a bidirectional magnetic - coupled DC - DC converter circuit, which can provide stable voltage modulation and high - precision control. Moreover, only two gain parameters, namely the phase - shift angle and the switching frequency, need to be adjusted. The control strategy is easy to implement, can adapt to changes in circuit parameters, and improve the anti - interference ability and dynamic response performance of the system. Brief Description of the Drawings

[0026] Figure 1 It is the topological structure of the bidirectional DC - DC converter circuit provided by an embodiment of the present application.

[0027] Figure 2 It is the schematic diagram of the non - linear backstepping control provided by an embodiment of the present application.

[0028] Figure 3 It is the schematic diagram of the design of the controller provided by an embodiment of the present application. Detailed Embodiments

[0029] To make the above - mentioned objects, features, and advantages of the present application more obvious and understandable, the following provides a detailed description of the specific embodiments of the present application. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0030] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art belonging to the technical field of the present application. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] In the traditional control scheme of the bidirectional DC-DC converter, the linear PI controller cannot appropriately adjust the gain when the circuit operating point changes. Designing a look-up table method based on the nominal parameters of the MLDDC (bidirectional magnetic-coupled DC-DC converter) can solve the problem of gain adjustment. However, the uncertainty of circuit parameters will affect the design of the look-up table method parameters; fuzzy control requires a lot of work to establish the input-output mapping relationship, and the stability of the fuzzy control closed-loop cannot be verified and proven; linear sliding mode control has the problems of overshoot and large static error due to the absence of an integral term. Although single-integral sliding mode and double-integral sliding mode greatly reduce the static error, such controllers require 3-4 adjustable parameters, the parameter tuning process is complex, and the stability conditions are harsh.

[0033] Based on the problems existing in the above-mentioned control schemes, it is necessary to provide a control method and converter applied to the bidirectional DC-DC converter circuit. This control method is a nonlinear backstepping control method based on a nonlinear backstepping controller, which can provide stable voltage modulation and high-precision control, and only needs to adjust two gain parameters. The control strategy is easy to implement, can adapt to the changes of circuit parameters, and improve the anti-interference ability and dynamic response performance of the system.

[0034] To better understand the nonlinear backstepping control method, the bidirectional DC-DC converter circuit is introduced below.

[0035] As Figure 1 shown, the bidirectional DC-DC converter circuit includes a primary full-bridge circuit H 1 , a magnetic coupling transformer, and a secondary full-bridge circuit H 2 , where the primary full-bridge circuit H 1 includes a first switch T 1 , a second switch T 2 , a third switch T 3 , and a fourth switch T 4 ; the secondary full-bridge circuit H 2 includes a fifth switch T 5 , a sixth switch T 6 , a seventh switch T 7 , and an eighth switch T 8 . The primary full-bridge circuit H 1 and the secondary full-bridge circuit H 2 are active bridges, the magnetic coupling transformer is a high-frequency magnetic coupling transformer, and the turns ratio is n.

[0036] In the specific topology, two active bridges are connected through a magnetic coupling transformer. On the low-voltage side of the magnetic coupling transformer, the first end of the input inductor L S is connected to the first end of the low-voltage side power supply, and the second end of the input inductor L S is connected to the primary full-bridge circuit H 1Connection, i.e., the input inductor L S The second end of S is connected to the first end of the first switch T 1 The first end of 1 is connected to the first end of the third switch T 3 The first end of 3 is connected to the first end of the second switch T 2 The first end of 2 is connected to the second end of the first switch T 1 The first end of 1 is connected to the second end of the first switch T and the first end of the primary coil of the magnetic coupling transformer 4 The first end of 4 is connected to the second end of the third switch T 3 The first end of 3 is connected to the second end of the primary coil of the magnetic coupling transformer 2 The second end of 2 is connected to the second end of the fourth switch T 4 The second end of 4 is connected to the second end of the low - voltage side power supply

[0037] On the high - voltage side of the magnetic coupling transformer, the first end of the fifth switch T 5 The first end of 5 is connected to the first end of the seventh switch T 7 The first end of 7 is connected to the first end of the high - voltage side power supply; the first end of the secondary coil of the magnetic coupling transformer is connected to the second end of the fifth switch T through the secondary equivalent inductor L and the secondary equivalent resistor R 5 The first end of 5 is connected to the second end of the fifth switch T and the first end of the sixth switch T 6 The second end of the secondary coil of the magnetic coupling transformer is connected to the second end of the seventh switch T 7 And the first end of the eighth switch T 8 The first end of 6 is connected to the second end of the sixth switch T 6 The second end of 6 is connected to the second end of the eighth switch T 8 And the second end of the high - voltage side power supply. A capacitor C is also connected between the first end and the second end of the high - voltage side power supply

[0038] The control terminal of the first switch T 1 And the control terminal of the fourth switch T 4 Are connected to the first control terminal of the controller to receive the first control signal for conduction or cut - off; the control terminal of the second switch T 2 And the control terminal of the third switch T 3 Are connected to the second control terminal of the controller to receive the second control signal for conduction or cut - off; the control terminal of the fifth switch T 5 And the control terminal of the eighth switch T 8 Are connected to the third control terminal of the controller to receive the third control signal for conduction or cut - off; the control terminal of the sixth switch T 6 And the control terminal of the seventh switch T 7 Are connected to the fourth control terminal of the controller to receive the fourth control signal for conduction or cut - off

[0039] When the single-phase-shift modulation (SPSM) mode is adopted, there is a fixed phase difference between the switching actions of one active bridge and those of the other active bridge. This phase difference can be positive or negative. A positive phase shift means that the voltage peak on the primary side appears before the voltage peak on the secondary side. This phase relationship affects the current waveform through the magnetically coupled transformer, and thus affects the power transfer characteristics of the entire bidirectional DC-DC converter.

[0040] In the single-phase-shift modulation mode, by adjusting the phase difference between the primary side and the secondary side, the power flow from the low-voltage side H 1 to the high-voltage side H 2 can be controlled, or conversely, the power flow from the high-voltage side H 2 to the low-voltage side H 1 can be controlled. The power flow direction depends on the required application and system configuration. The adjustment of the phase difference and voltage amplitude is achieved by controlling the switching devices in the active bridge, and these switching devices can be MOSFETs, IGBTs or other types of power electronic devices.

[0041] To achieve continuous current, an input inductor L is connected in series on the low-voltage side of the magnetically coupled transformer S ; the equivalent inductance on the secondary side is composed of the leakage inductance of the primary winding and the leakage inductance of the secondary winding as well as an additional inductance , that is , and the additional inductance is used to regulate the circuit power. The equivalent resistance on the secondary side is composed of the internal resistance of the electromagnetic connection between the primary side and the secondary side and , as well as an additional resistance , that is , and the additional resistance

[0042] is used to regulate the circuit power. The leakage inductance is the inductance generated by the magnetic flux that is not coupled to the magnetic core in the winding. The leakage inductances and of the magnetically coupled transformer, as well as the additional additional inductance also play important roles in the operation of the MLDDC, and the additional additional inductance is used to regulate the power of the MLDDC. The values and characteristics of these inductance elements affect the dynamic response and stability of the MLDDC, so they need to be carefully considered in the design and control strategies, and no specific numerical limitations are given in this embodiment.

[0043] In the first aspect of this application, a control method applied to a bidirectional DC-DC converter circuit is provided. As Figure 2 、 Figure 3As shown in the figure, the specific implementation method of this control method is as follows: Obtain the first control signal and directly apply the first control signal to the first switch and the fourth switch of the primary full-bridge circuit; Phase-shift the first control signal by 180° to obtain the second control signal and apply the second control signal to the second switch and the third switch of the primary full-bridge circuit; Phase-shift the first control signal by the target phase angle to obtain the third control signal and apply the third control signal to the fifth switch and the eighth switch of the secondary full-bridge circuit, where the target phase angle is determined using the Lyapunov stability theory; Phase-shift the third control signal by 180° to obtain the fourth control signal and apply the fourth control signal to the sixth switch and the seventh switch of the secondary full-bridge circuit.

[0044] The control method applied to the bidirectional DC-DC converter circuit in this embodiment is a control method based on a non-linear backstepping controller, which is used for the control of the bidirectional magnetically coupled DC-DC converter (MLDDC) circuit, can provide stable voltage modulation and high-precision control, and only needs to adjust two gain parameters, namely the phase-shift angle and the switching frequency, which is easy to control. This control method can adapt to the changes of circuit parameters, improve the anti-interference ability and dynamic response performance of the system.

[0045] In one embodiment, the acquisition logic of the target phase angle includes: Based on the Fourier series of the switching function, establish the low-frequency harmonic model of the output voltage of the bidirectional DC-DC converter circuit and determine the output voltage dynamic equation; Establish the error expression between the output voltage and the reference voltage, substitute the output voltage dynamic equation into the error expression to obtain the error dynamic equation; Define the Lyapunov function and take the derivative, substitute the error dynamic equation into the differentiated Lyapunov function, determine the global stability condition of the function according to the Lyapunov stability theory, and based on the global stability condition, determine the target phase angle, and adjust the phase-shift ratio and the output voltage by controlling the phase-shift angle.

[0046] In the specific implementation steps, the output voltage dynamic equation is derived as follows:

[0047] First, based on the topology of the bidirectional DC-DC converter circuit, construct a differential equation.

[0048] The differential equation expression is: , where, is the phase angle of the converter circuit, which is determined by the parameters of the converter circuit and is usually a fixed value, , is the impedance, , is the switching frequency, is the inductance value of the input inductor of the converter circuit, is the resistance value of the input inductor, is the cosine function related to the phase angle of the converter circuit, is the turns ratio of the magnetic coupling transformer, is the input voltage of the low-voltage side of the converter circuit, is the DC current of the converter circuit, is the output voltage of the converter circuit, is the value of the DC-side capacitor of the converter circuit.

[0049] Then, assume , define the control variable as , where is the total phase shift angle, divide into and , The relationship between and is ,

[0050] Finally, convert the cosine to sine through trigonometric functions to obtain , substitute into the differential equation to obtain the output voltage dynamic equation.

[0051] The output voltage dynamic equation is: .

[0052] Optionally, the way to obtain the error dynamic equation is:

[0053] Establish an error expression between the output voltage of the bidirectional DC-DC converter circuit and the reference voltage: , where is the output voltage of the converter circuit, is the reference voltage, is the error between the output voltage of the converter circuit and the reference voltage;

[0054] Substitute the output voltage dynamic equation into the error expression to determine the error dynamic equation: .

[0055] Optionally, the method for determining the target phase angle includes:

[0056] Define the Lyapunov function as , and take the derivative of ;

[0057] Substitute the error dynamic equation into the derivative of the Lyapunov function, and we can get:

[0058] ,

[0059] When the condition is satisfied, determine the global stability condition as:

[0060] ;

[0061] The reaching law is obtained from the global stability condition:

[0062] ,

[0063] Solve the target phase angle and phase shift ratio from the reaching law.

[0064] The target phase angle is:

[0065] ;

[0066] The phase shift ratio is: .

[0067] In the embodiment of the present application, the Lyapunov stability theory is used to determine the required phase shift angle, and the phase shift ratio and voltage adjustment are achieved by controlling the phase shift angle, so as to achieve smaller overshoot and faster settling time during load mutation, significantly improving the dynamic response performance and stability of the system.

[0068] The control method of this embodiment has the following beneficial effects: First, enhanced anti-interference ability: The designed backstepping controller can track the reference voltage well under various working conditions of different loads, and can achieve stable voltage regulation under the conditions of reference voltage change and input voltage change, and has extremely low fluctuations; Second, improved load transient response performance and reference voltage tracking performance: In the case of load mutation, compared with linear sliding mode control and integral sliding mode control, the proposed backstepping controller has lower overshoot and shorter settling time, and the backstepping control has smaller chattering, thus reducing the steady-state error.

[0069] According to the second aspect of the present application, a converter is provided; by using the above control method applied to the bidirectional DC-DC converter circuit to control the bidirectional DC-DC converter circuit, stable voltage modulation and high-precision control can be provided, and only two gain parameters, namely the phase shift angle and the switching frequency, need to be adjusted. This control method can adapt to the change of circuit parameters and improve the anti-interference ability and dynamic response performance of the system.

[0070] The technical features of the above embodiments can be combined arbitrarily. For the sake of brief description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0071] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A control method for a bidirectional DC-DC converter circuit, characterized in that: The bidirectional DC-DC converter circuit comprises a primary full-bridge circuit, a magnetic coupling transformer and a secondary full-bridge circuit connected in sequence, wherein the primary full-bridge circuit comprises a first switch, a second switch, a third switch and a fourth switch; the secondary full-bridge circuit comprises a fifth switch, a sixth switch, a seventh switch and an eighth switch; The control method is: Obtain a first control signal, and directly apply the first control signal to the first switch and the fourth switch of the primary full-bridge circuit; Shifting the first control signal by 180° to obtain a second control signal, and applying the second control signal to the second switch and the third switch of the primary full-bridge circuit; Shifting the first control signal by a target phase angle to obtain a third control signal, and applying the third control signal to a fifth switch and an eighth switch of the secondary full-bridge circuit, wherein the target phase angle is determined by Lyapunov stability theory; Shifting the third control signal by 180° to obtain a fourth control signal, and applying the fourth control signal to the sixth switch and the seventh switch of the secondary full-bridge circuit; The acquisition logic of the target phase angle includes: Based on the Fourier series of the switching function, an output voltage low-frequency harmonic model of the bidirectional DC-DC converter circuit is established to determine the output voltage dynamic equation; wherein the output voltage dynamic equation is derived in the following manner: based on the topological structure of the bidirectional DC-DC converter circuit, a differential equation is constructed: , is the phase angle of the converter circuit, , is the impedance, , is the switching frequency, is the inductance value of the input inductor of the converter circuit, is the resistance value of the input inductor, is the cosine function related to the phase angle of the converter circuit, is the turns ratio of the magnetic coupling transformer, is the input voltage on the low voltage side of the converter circuit, is the DC current of the converter circuit, is the output voltage of the converter circuit, is the value of the DC side capacitor of the converter circuit; assuming , define the control variables for ,in, is the total phase shift angle, Divided into and , , is the target phase angle; converting cosine to sine through trigonometric function to obtain ,Will Substitute into the differential equation to obtain the output voltage dynamic equation: ; Establishing an error expression between the output voltage and the reference voltage, substituting the output voltage dynamic equation into the error expression to obtain an error dynamic equation; A Lyapunov function is defined and derived, the error dynamic equation is substituted into the derived Lyapunov function, a global stability condition of the function is determined according to the Lyapunov stability theory, and the target phase angle is determined based on the global stability condition.

2. The control method for a bidirectional DC-DC converter circuit according to claim 1, characterized in that: The error dynamic equation is obtained as follows: Establish the error expression between the output voltage of the bidirectional DC-DC converter circuit and the reference voltage: ,in, is the output voltage of the converter circuit, is the reference voltage, is the error between the output voltage of the converter circuit and the reference voltage; Substitute the output voltage dynamic equation into the error expression to determine the error dynamic equation: .

3. The control method for a bidirectional DC-DC converter circuit according to claim 2, characterized in that: The method for determining the target phase angle comprises: Define the Lyapunov function as ,right Derivation; Substituting the error dynamic equation into the derived Lyapunov function, we can obtain: , When the conditions are met When , the global stability condition is determined as: ; The reaching law is obtained from the global stability condition: ， The target phase angle is solved by the reaching law: 。 4. A converter, characterized in that: It comprises a bidirectional DC-DC converter circuit; and uses the control method applied to the bidirectional DC-DC converter circuit as described in any one of claims 1 to 3 to control the bidirectional DC-DC converter circuit.

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