Control method and converter for bidirectional DC-DC converter circuit

Abstract

The present application relates to a control method and converter for a bidirectional DC-DC converter circuit, wherein the control method comprises: obtaining a first control signal, and directly applying the first control signal to the first switch and the fourth switch of the primary full-bridge circuit; phase-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; phase-shifting the first control signal by a target phase angle to obtain a third control signal, and applying the third control signal to the fifth switch and the eighth switch of the secondary full-bridge circuit, wherein the target phase angle is determined by using the Lyapunov stability theory; phase-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, which can provide stable voltage modulation and high-precision control, with few gain parameters, and can adapt to changes in circuit parameters, thereby improving anti-interference and dynamic response performance.

Description

Technical Field

[0001] The present 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 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 surface through the sliding mode controller, and has faster dynamic response speed and stronger robustness; fuzzy logic control can handle parameter perturbations and uncertainties, and can improve the overall performance of the control system by combining fuzzy logic allocation strategies with linear PID or sliding mode control.

[0003] However, the traditional linear PI controller cannot properly adjust the gain when the circuit operating point is switched. The nominal parameter design lookup method based on MLDDC can solve the problem of gain adjustment, but the uncertainty of circuit parameters will affect the design of the lookup method parameters; fuzzy control requires a lot of work to establish the mapping relationship between input and output, and the stability of the fuzzy control closed loop cannot be verified; linear sliding mode control has problems of overshoot and large static error due to the lack of integral terms. Although single integral sliding mode and double integral sliding mode greatly reduce static errors, such controllers require 3-4 adjustable parameters, the parameter adjustment process is complicated, and the stability conditions are harsh. Therefore, the above-mentioned control schemes all have corresponding problems, which are not conducive to promotion 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-mentioned purpose of the present application is achieved through the following technical solutions.

[0006] In a first aspect of the present application, a control method for a bidirectional DC-DC converter circuit is provided, wherein 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, wherein the primary full-bridge circuit includes a first switch, a second switch, a third switch and a fourth switch; and the secondary full-bridge circuit includes a fifth switch, a sixth switch, a seventh switch and an eighth switch.

[0007] The control method is: obtaining a first control signal, and directly applying 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 the fifth switch and the eighth switch of the secondary full-bridge circuit, wherein the target phase angle is determined using the 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.

[0008] In one of the embodiments, the logic for acquiring the target phase angle is as follows: based on the Fourier series of the switching function, a low-frequency harmonic model of the output voltage of the bidirectional DC-DC converter circuit is established to determine the output voltage dynamic equation; an error expression between the output voltage and the reference voltage is established, and the output voltage dynamic equation is substituted into the error expression to obtain the error dynamic equation; a Lyapunov function is defined and differentiated, and the error dynamic equation is substituted into the differentiated Lyapunov function, and the 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.

[0009] In one of the embodiments, the output voltage dynamic equation is derived in the following manner: a differential equation is constructed based on the topology of the bidirectional DC-DC converter circuit.

[0010] The differential equation expression is: ,in, 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 capacitance of the converter circuit.

[0011] Assumptions , define the control variables for ,in, is the total phase shift angle, Divided into and , , is the target phase angle.

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

[0013] In one embodiment, the error dynamic equation is obtained by establishing an 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; the output voltage dynamic equation is substituted into the error expression to determine the error dynamic equation as follows: .

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

[0015] Define the Lyapunov function as ,right Derivation;

[0016] Substituting the error dynamic equation into the derived Lyapunov function, we can obtain:

[0017] ,

[0018] When the conditions are met When , the global stability condition is determined as:

[0019] ;

[0020] The reaching law is obtained from the global stability condition:

[0021] ,

[0022] The target phase angle is solved by the reaching law:

[0023] .

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

[0025] The control method based on the nonlinear backstepping controller of the embodiment of the present application is used for controlling a bidirectional magnetically coupled DC-DC converter 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. The control strategy is easy to implement, can adapt to changes in circuit parameters, and improve the system's anti-interference and dynamic response performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A topological structure of a bidirectional DC-DC converter circuit provided in an embodiment of the present application.

[0027] Figure 2 A schematic diagram of a nonlinear reverse control provided in an embodiment of the present application.

[0028] Figure 3 A schematic diagram of the design of a controller provided in one embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this 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 bidirectional DC-DC converter, the linear PI controller cannot properly adjust the gain when the circuit operating point is switched. The nominal parameter design table method based on MLDDC (bidirectional magnetically coupled DC-DC converter) can solve the problem of gain adjustment. However, the uncertainty of circuit parameters will affect the design of the table lookup method parameters; fuzzy control requires a lot of work to establish the mapping relationship between input and output, and the stability of the fuzzy control closed loop cannot be verified; linear sliding mode control has problems of overshoot and large static error due to the lack of integral terms. Although single integral sliding mode and double integral sliding mode greatly reduce static errors, such controllers require 3-4 adjustable parameters, the parameter adjustment process is complicated, 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 for bidirectional DC-DC converter circuits. The 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 changes in circuit parameters, and improve the system's anti-interference and dynamic response performance.

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

[0035] like Figure 1 As shown, the bidirectional DC-DC converter circuit includes a primary full-bridge circuit H1, a magnetic coupling transformer and a secondary full-bridge circuit H2 connected in sequence, wherein the primary full-bridge circuit H1 includes a first switch T1, a second switch T2, a third switch T3 and a fourth switch T4; the secondary full-bridge circuit H2 includes a fifth switch T5, a sixth switch T6, a seventh switch T7 and an eighth switch T8. The primary full-bridge circuit H1 and the secondary full-bridge circuit H2 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 input inductor L S The first end of the low voltage side power supply is connected to the first end of the input inductor L S The second end is connected to the primary full-bridge circuit H1, that is, the input inductor L S The second end of is connected to the first end of the first switch T1 and the first end of the third switch T3, the first end of the second switch T2 is connected to the second end of the first switch T1 and the first end of the primary coil of the magnetic coupling transformer, the first end of the fourth switch T4 is connected to the second end of the third switch T3 and the second end of the primary coil of the magnetic coupling transformer, and the second end of the second switch T2 is connected to the second end of the fourth switch T4 and 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 T5 is connected to the first end of the seventh switch T7, and 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 T5 through the secondary equivalent inductance L and the secondary equivalent resistance R, and is connected to the first end of the sixth switch T6; the second end of the secondary coil of the magnetic coupling transformer is connected to the second end of the seventh switch T7 and the first end of the eighth switch T8; the second end of the sixth switch T6 is connected to the second end of the eighth switch T8, and is connected to the second end of the high-voltage side power supply; and a capacitor C is also connected between the first and second ends of the high-voltage side power supply.

[0038] The controlled end of the first switch T1 and the controlled end of the fourth switch T4 are connected to the first control end of the controller and receive a first control signal to be turned on or off; the controlled end of the second switch T2 and the controlled end of the third switch T3 are connected to the second control end of the controller and receive a second control signal to be turned on or off; the controlled end of the fifth switch T5 and the controlled end of the eighth switch T8 are connected to the third control end of the controller and receive a third control signal to be turned on or off; the controlled end of the sixth switch T6 and the controlled end of the seventh switch T7 are connected to the fourth control end of the controller and receive a fourth control signal to be turned on or off.

[0039] When the single phase shift modulation (SPSM) mode is used, the switching action of one active bridge has a fixed phase difference with respect to the switching action of another 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 single phase shift modulation mode, by adjusting the phase difference between the primary and secondary sides, the power flow from the low voltage side H1 to the high voltage side H2 can be controlled, or vice versa, the power flow from the high voltage side H2 to the low voltage side H1 can be controlled, and 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, which can be MOSFETs, IGBTs or other types of power electronic devices.

[0041] In order to achieve current continuity, an input inductor L is connected in series on the low-voltage side of the magnetic coupling transformer. S ; Secondary side equivalent inductance The leakage inductance of the primary winding The leakage inductance of the secondary winding And additional inductance Composition, that is , additional inductance Used to adjust the circuit power. The internal resistance of the electromagnetic connection between the primary and secondary sides and , and additional resistors Composition, that is , additional resistance Used to regulate circuit power.

[0042] Leakage inductance is the inductance generated by the magnetic flux in the winding that is not coupled to the magnetic core. The leakage inductance of the magnetically coupled transformer is and , and additional additional inductance It also plays an important role in the operation of MLDDC, and the additional inductance The values ​​and characteristics of these inductance components will affect the dynamic response and stability of the MLDDC, so they need to be carefully considered in the design and control strategy. The specific values ​​are not limited in this embodiment.

[0043] In a first aspect of the present application, a control method for a bidirectional DC-DC converter circuit is provided. Figure 2 , Figure 3 As shown, the specific implementation of 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; 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, wherein the target phase angle is determined by 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.

[0044] The control method applied to the bidirectional DC-DC converter circuit of this embodiment is a control method based on a nonlinear backstepping controller, which is used for controlling a 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, so it is easy to control. This control method can adapt to changes in circuit parameters and improve the anti-interference and dynamic response performance of the system.

[0045] In one embodiment, the logic for acquiring the target phase angle includes: based on the Fourier series of the switching function, establishing a low-frequency harmonic model of the output voltage of the bidirectional DC-DC converter circuit, and determining 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, and obtaining the error dynamic equation; defining and differentiating the Lyapunov function, substituting the error dynamic equation into the derived Lyapunov function, determining the global stability condition of the function according to the Lyapunov stability theory, determining the target phase angle based on the global stability condition, and adjusting the phase shift angle 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] Firstly, the differential equation is constructed based on the topological structure of the bidirectional DC-DC converter circuit.

[0048] The differential equation expression is: ,in, is the phase angle of the converter circuit, which is determined by the converter circuit parameters 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 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 capacitance of the converter circuit.

[0049] Then, assuming , define the control variables for ,in, is the total phase shift angle, Divided into and , and The relationship is , is the target phase angle.

[0050] Finally, we convert the cosine to sine using trigonometric functions to get ,Will Substitute into the differential equation to obtain the output voltage dynamic equation.

[0051] The output voltage dynamic equation is: .

[0052] Optionally, the error dynamic equation is obtained as follows:

[0053] 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;

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

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

[0056] Define the Lyapunov function as ,right Derivation;

[0057] Substituting the error dynamic equation into the derived Lyapunov function, we can obtain:

[0058] ,

[0059] When the conditions are met When , the global stability condition is determined as:

[0060] ;

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

[0062] ,

[0063] The target phase angle and shift phase are solved by the reaching law.

[0064] The target phase angle is:

[0065] ;

[0066] The shift ratio is: .

[0067] The embodiment of the present application utilizes Lyapunov stability theory to determine the required phase shift angle, and achieves phase shift ratio and voltage adjustment by controlling the phase shift angle, thereby achieving smaller overshoot and faster stabilization time during load mutation, thereby significantly improving the dynamic response performance and stability of the system.

[0068] The control method of this embodiment has the following beneficial effects: 1. 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 with extremely low fluctuation when the reference voltage changes and the input voltage changes; 2. Improved load transient response performance and reference voltage tracking performance: In the case of sudden load changes, compared with linear sliding mode control and integral sliding mode control, the proposed backstepping controller has lower overshoot and shorter stabilization time, and the backstepping control has smaller jitter, thereby reducing the steady-state error.

[0069] According to the second aspect of the present application, a converter is provided; the above-mentioned control method applied to the bidirectional DC-DC converter circuit is used to control the bidirectional DC-DC converter circuit, which 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. This control method can adapt to changes in circuit parameters and improve the system's anti-interference and dynamic response performance.

[0070] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims, and the description may be used to interpret the contents 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; The third control signal is phase-shifted by 180° to obtain a fourth control signal, and the fourth control signal is applied to the sixth switch and the seventh switch of the secondary full-bridge circuit.

2. The control method for a bidirectional DC-DC converter circuit according to claim 1, characterized in that: The acquisition logic of the target phase angle includes: Based on the Fourier series of the switching function, a low-frequency harmonic model of the output voltage of the bidirectional DC-DC converter circuit is established to determine 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.

3. The control method for a bidirectional DC-DC converter circuit according to claim 2, characterized in that: The output voltage dynamic equation is derived as follows: Based on the topology of the bidirectional DC-DC converter circuit, construct the differential equation: ， in, 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 capacitance of the converter circuit; Assumptions , define the control variables for ,in, is the total phase shift angle, Divided into and , , is the target phase angle; Convert cosine to sine using trigonometric functions ,Will Substitute into the differential equation to obtain the output voltage dynamic equation: 。 4. The control method for a bidirectional DC-DC converter circuit according to claim 3, 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: .

5. The control method for a bidirectional DC-DC converter circuit according to claim 4, 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: 。 6. 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 5 to control the bidirectional DC-DC converter circuit.

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