Dual Phase-Shift Control Method, Storage Medium, Bidirectional DCDC Controller and Converter

Abstract

The present invention discloses a dual-phase-shift control method, a storage medium, a bidirectional DCDC controller and a converter. The method includes: obtaining the actual output voltage and the target output voltage of the bidirectional DCDC conversion circuit; obtaining the internal phase-shift duty ratio according to the actual output voltage and the target output voltage, where the internal phase-shift duty ratio is used to indicate the inter-bridge phase-shift duty ratio of the high-voltage leading side; obtaining the pre-determined external phase-shift duty ratio, where the external phase-shift duty ratio is used to indicate the inter-bridge phase-shift duty ratio between the high-voltage leading side and the low-voltage lagging side; controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio. This method can enable the conversion circuit to have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirements, and has a high control accuracy. At the same time, it does not need to involve parameters such as phase-shift inductance and switching frequency, has little dependence on parameters, and has high robustness.

Description

Technical Field

[0001] The present invention relates to the technical field of battery energy storage, and particularly relates to a dual phase-shift control method for a bidirectional DCDC conversion circuit, a computer-readable storage medium, a bidirectional DCDC controller, and a bidirectional DCDC converter. Background Art

[0002] Energy storage devices are generally composed of storage batteries. The bidirectional DCDC converter connected to the energy storage device functions to perform voltage conversion, manage and protect the battery, and at the same time enable bidirectional energy flow. The bidirectional DCDC converter has the characteristics of high power density, fast dynamic response, easy implementation of soft switching, bidirectional power flow, small volume, high efficiency, low cost, and simple structure. By reasonably and effectively controlling the on and off of the switching tubes in the bidirectional DCDC converter, the transmission of its output voltage, current, and power can be controlled. Different energy storage devices have different voltage levels, and the battery voltage changes with the change of the battery charge. This requires the bidirectional DCDC converter to have a wide voltage range and electrical isolation. Therefore, the phase-shift control strategy is increasingly widely applied to the control of the bidirectional DCDC converter.

[0003] However, the traditional phase-shift control uses a mathematical model under ideal conditions, has a large dependence on parameters, there are errors in the solution process, the optimal solution expression is relatively complex, and the real-time performance and robustness are relatively poor, which cannot meet the actual engineering applications. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related technologies to some extent. To this end, the first object of the present invention is to propose a dual phase-shift control method for a bidirectional DCDC conversion circuit. This method can enable the bidirectional DCDC conversion circuit to have smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and less computational effort, can meet the real-time requirements, and has high control accuracy. At the same time, it does not need to involve parameters such as phase-shift inductance and switching frequency, has a small dependence on parameters, and high robustness.

[0005] The second object of the present invention is to propose a computer-readable storage medium.

[0006] The third object of the present invention is to propose a bidirectional DCDC controller.

[0007] The fourth object of the present invention is to propose a bidirectional DCDC converter.

[0008] To achieve the above object, an embodiment of the first aspect of the present invention provides a dual-phase-shift control method for a bidirectional DCDC conversion circuit. The bidirectional DCDC conversion circuit includes a high-voltage leading side and a low-voltage lagging side. The method includes: obtaining the actual output voltage and the target output voltage of the bidirectional DCDC conversion circuit; obtaining an internal phase-shift duty ratio according to the actual output voltage and the target output voltage, where the internal phase-shift duty ratio is used to indicate the inter-bridge phase-shift duty ratio of the high-voltage leading side; obtaining a pre-determined external phase-shift duty ratio, where the external phase-shift duty ratio is used to indicate the inter-bridge phase-shift duty ratio between the high-voltage leading side and the low-voltage lagging side; and controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio.

[0009] According to the dual-phase-shift control method for a bidirectional DCDC conversion circuit of the embodiment of the present invention, by obtaining the actual output voltage and the target output voltage of the bidirectional DCDC conversion circuit, obtaining the internal phase-shift duty ratio according to the actual output voltage and the target output voltage, obtaining the pre-determined external phase-shift duty ratio, and controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio. Thus, the bidirectional DCDC conversion circuit can have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirements, and has a high control accuracy. At the same time, it does not need to involve parameters such as phase-shift inductors and switching frequencies, has a small dependence on parameters, and has high robustness.

[0010] According to an embodiment of the present invention, obtaining the internal phase-shift duty ratio according to the actual output voltage and the target output voltage includes: obtaining the voltage difference between the target output voltage and the actual output voltage; and performing PI regulation on the voltage difference to obtain the internal phase-shift duty ratio.

[0011] According to an embodiment of the present invention, performing PI regulation on the voltage difference to obtain the internal phase-shift duty ratio includes: obtaining the internal phase-shift duty ratio at the previous control moment; if the internal phase-shift duty ratio at the previous control moment is greater than the upper limit value, performing PI regulation on the negative voltage difference to obtain the internal phase-shift duty ratio at the current control moment; if the internal phase-shift duty ratio at the previous control moment is less than the lower limit value, performing PI regulation on the positive voltage difference to obtain the internal phase-shift duty ratio at the current control moment.

[0012] According to an embodiment of the present invention, the pre-determined external phase-shift duty ratio is the external phase-shift duty ratio when the transmission power of the bidirectional DCDC conversion circuit reaches the maximum.

[0013] According to an embodiment of the present invention, the value range of the pre-determined external phase-shift duty ratio is 0.3 to 0.5.

[0014] According to an embodiment of the present invention, the method further includes: correcting the pre-determined external phase-shift duty ratio according to the internal phase-shift duty ratio.

[0015] According to an embodiment of the present invention, correcting a pre-determined external phase-shift duty ratio according to an internal phase-shift duty ratio includes: obtaining a duty ratio difference between the internal phase-shift duty ratio and the pre-determined external phase-shift duty ratio; performing sliding mode control on the duty ratio difference to obtain a correction amount of the external phase-shift duty ratio; and adding the correction amount to the pre-determined external phase-shift duty ratio to obtain a corrected external phase-shift duty ratio.

[0016] According to an embodiment of the present invention, the high-voltage leading side includes a first full-bridge circuit, and the low-voltage lagging side includes a second full-bridge circuit. Controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio includes: the control waveforms of the first upper-bridge arm switch tube and the first lower-bridge arm switch tube of the first full-bridge circuit are complementary, the control waveforms of the second upper-bridge arm switch tube and the second lower-bridge arm switch tube of the first full-bridge circuit are complementary, and the phases of the control waveforms of the first upper-bridge arm switch tube and the second upper-bridge arm switch tube differ by the internal phase-shift duty ratio; the control waveforms of the third upper-bridge arm switch tube and the third lower-bridge arm switch tube of the second full-bridge circuit are complementary, the control waveforms of the fourth upper-bridge arm switch tube and the fourth lower-bridge arm switch tube of the second full-bridge circuit are complementary, and the phases of the control waveforms of the third upper-bridge arm switch tube and the first upper-bridge arm switch tube differ by the external phase-shift duty ratio.

[0017] According to an embodiment of the present invention, controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio further includes: the control waveforms of the third upper-bridge arm switch tube and the fourth lower-bridge arm switch tube are the same, and the control waveforms of the third lower-bridge arm switch tube and the fourth upper-bridge arm switch tube are the same; or, the phases of the control waveforms of the third upper-bridge arm switch tube and the fourth upper-bridge arm switch tube differ by the internal phase-shift duty ratio.

[0018] To achieve the above object, an embodiment of the second aspect of the present invention proposes a computer-readable storage medium, on which a dual-phase-shift control program for a bidirectional DCDC conversion circuit is stored. When the dual-phase-shift control program for the bidirectional DCDC conversion circuit is executed by a processor, the dual-phase-shift control method for the bidirectional DCDC conversion circuit as described above is implemented.

[0019] According to the computer-readable storage medium of the embodiment of the present invention, through the above dual-phase-shift control method for the bidirectional DCDC conversion circuit, the bidirectional DCDC conversion circuit can have a small current stress, can achieve soft-switching characteristics, reduce switching losses, and at the same time requires few signals to be collected and has a small amount of calculation, can meet the real-time requirement, and has a high control accuracy. At the same time, it does not need to involve parameters such as phase-shift inductance and switching frequency, has little dependence on parameters, and has high robustness.

[0020] To achieve the above object, an embodiment of the third aspect of the present invention provides a bidirectional DCDC controller, including: a memory, a processor, and a dual-phase-shift control program of a bidirectional DCDC conversion circuit stored in the memory and executable on the processor. When the processor executes the program, the dual-phase-shift control method as described above is implemented.

[0021] According to the bidirectional DCDC controller of the embodiment of the present invention, through the dual-phase-shift control method of the above-mentioned bidirectional DCDC conversion circuit, the bidirectional DCDC conversion circuit can have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirement, and has a high control accuracy. At the same time, it does not need to involve parameters such as phase-shifting inductance and switching frequency, has little dependence on parameters, and has high robustness.

[0022] To achieve the above object, an embodiment of the fourth aspect of the present invention provides a bidirectional DCDC converter, including: a bidirectional DCDC conversion circuit and the foregoing bidirectional DCDC controller.

[0023] According to the bidirectional DCDC converter of the embodiment of the present invention, through the foregoing bidirectional DCDC controller, the bidirectional DCDC conversion circuit can have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirement, and has a high control accuracy. At the same time, it does not need to involve parameters such as phase-shifting inductance and switching frequency, has little dependence on parameters, and has high robustness.

[0024] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0025] Figure 1 It is a structural block diagram of a dual-phase-shift control algorithm in the prior art;

[0026] Figure 2 It is a topology diagram of a bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0027] Figure 3 It is a flowchart of a dual-phase-shift control method for a bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0028] Figure 4 It is a relationship curve diagram between the transmission power of traditional single-phase-shift control and the phase-shift duty ratio;

[0029] Figure 5 It is a three-dimensional relationship curve diagram between the transmission power of dual-phase-shift control and the phase-shift duty ratio;

[0030] Figure 6 The structural block diagram of the dual-phase-shift control of the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0031] Figure 7 The control waveform diagram of the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0032] Figure 8 The control waveform diagram of the bidirectional DCDC conversion circuit according to another embodiment of the present invention;

[0033] Figure 9 The simulation waveform diagram of the primary current of the high-frequency transformer in the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0034] Figure 10 The simulation waveform diagram of the secondary current of the high-frequency transformer in the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0035] Figure 11 The simulation waveform diagram of the target output voltage and the actual output voltage of the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0036] Figure 12 The error diagram of the actual output voltage of the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0037] Figure 13 The simulation waveform diagram of the secondary voltage of the high-frequency transformer in the bidirectional DCDC conversion circuit according to an embodiment of the present invention;

[0038] Figure 14 The simulation waveform diagram of the primary voltage of the high-frequency transformer in the bidirectional DCDC conversion circuit according to an embodiment of the present invention. Detailed implementation manners

[0039] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0040] It should be noted that phase-shift control refers to controlling the power transmission in a circuit by changing the phase difference between different switching devices without changing the on-time or off-time duty cycle of the switching devices. Phase-shift control is easy to implement soft switching, has a small system inertia, and a fast dynamic response. Currently, the main phase-shift control strategies include traditional phase-shift control (i.e., single phase-shift control), dual phase-shift control, extended phase-shift control, and triple phase-shift control. Among them, traditional phase-shift control has a small inertia, good dynamic performance, simple control, and is easy to implement soft switching. This method is commonly used in dual-active full-bridge bidirectional DCDC converters. However, when the voltage ratio is mismatched, the peak value of the inductor current will be very large, which easily leads to an increase in the current stress of the switching devices, an increase in the reactive circulating power, i.e., the converter's return power, an increase in power loss, and a decrease in efficiency. The triple phase-shift control has more variables and requires the analysis of multiple states, which is relatively complex and reduces the dynamic performance of the converter. Compared with the triple phase-shift control, the dual phase-shift control has only two degrees of freedom, fewer states, simpler control, and is easy to implement. Moreover, compared with the single phase-shift control, the dual phase-shift control significantly reduces the converter's return power and the current stress of the switching devices, increases the range of zero-voltage switching (ZVS) of the switching devices, and improves the converter's efficiency. Therefore, this application mainly focuses on dual phase-shift control.

[0041] In the related art, a phase-shift control method based on the minimum return power is provided. As Figure 1 shown, this phase-shift control method is to control the sampling chip by the control system to collect the output voltage V2 and the output current i2, and determine the converter transmission power P2 through the output voltage V2 and the output current i2; divide the transmission power P2 by the maximum transmission power P N of the converter to obtain the per-unit transmission power P; according to different value ranges of the per-unit transmission power P, calculate the inner phase-shift angle d1 according to the minimum return power; subtract the given output voltage V 2ref from the output voltage V2, and obtain the outer phase-shift angle d2 through a PI controller; generate pulses according to the inner phase-shift angle d1 and the outer phase-shift angle d2, and keep the output voltage V2 constant by closed-loop adjusting the value of the outer phase-shift angle d2. In this method, the inner phase-shift angle d1 needs to first find the mathematical model of the return power through mathematical modeling, and then find the optimal solution expression through the minimum return power method. Since the mathematical model under ideal conditions is adopted, it has a large dependence on parameters, there are errors in the solution process, the optimal solution expression is relatively complex, and the real-time performance and robustness are relatively poor, which cannot meet the actual engineering applications.

[0042] In the related art, a dual-phase-shift modulation method for an isolated bidirectional full-bridge DC-DC converter is also provided. Specifically, the relationship between the internal and external phase-shift angles of the isolated bidirectional full-bridge DC-DC converter is re-constrained. The internal phase-shift angle D1-1 of the left-side switching tubes is made equal to the inter-bridge phase-shift angle D2 and used as a modulation degree of freedom, and the internal phase-shift angle D1-2 of the right-side switching tubes is used as another modulation degree of freedom for modulation. In this phase-shift control method, since the internal phase-shift angle D1-1 of the left-side switching tubes is made equal to the inter-bridge phase-shift angle D2 and used as a modulation degree of freedom, and the transmitted power is mainly related to the inter-bridge phase-shift angle D2, when the internal phase-shift angle D1-1 of the left-side switching tubes is forced to be equal to the inter-bridge phase-shift angle D2, the discharge time of the resonant inductor increases and the charging time decreases, resulting in this method being only applicable to non-heavy-load power transmission with a per-unit transmitted power less than 0.667.

[0043] To solve the above technical problems, the present application provides a dual-phase-shift control method for a bidirectional DCDC conversion circuit, which can enable the bidirectional DCDC conversion circuit to have a small current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirement, and has a high control accuracy. At the same time, it does not need to involve parameters such as phase-shift inductors and switching frequencies, has a small dependence on parameters, and has high robustness. In addition, when it is applied to a high-power and high-voltage energy storage system with multiple battery strings in parallel for voltage boosting, it can achieve voltage equalization control, realize full charge and full discharge of the battery strings, and solve the problem of internal circulating current caused by voltage differences between battery strings due to aging, parameter differences, etc. in a multiple-battery-string parallel energy storage system.

[0044] It should be noted that with reference to Figure 2As shown, the bidirectional DCDC conversion circuit of the present application includes a high-voltage leading side and a low-voltage lagging side, wherein the high-voltage leading side includes a first full-bridge circuit, an input-side parallel capacitor C1 and an LC series resonant circuit, and the low-voltage lagging side includes a second full-bridge circuit, an output-side parallel capacitor C2 and an output-side filter inductor L1, and the high-voltage leading side is connected to the low-voltage lagging side through a high-frequency transformer. Among them, the first full-bridge circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a first upper bridge arm switch tube Q1 and a first lower bridge arm switch tube Q2, and there is a first connection point A between the two, and the second bridge arm includes a second upper bridge arm switch tube Q3 and a second lower bridge arm switch tube Q4, and there is a second connection point B between the two. The LC series resonant circuit includes a resonant inductor Ls (also called a phase shift inductor) and a resonant capacitor C, one end of the resonant capacitor C is connected to the first connection point A, the other end of the resonant capacitor C is connected to one end of the resonant inductor Ls, the other end of the resonant inductor Ls is connected to one end of the primary side of the high-frequency transformer, and the other end of the primary side of the high-frequency transformer is connected to the second connection point B. The second full-bridge circuit includes a third bridge arm and a fourth bridge arm, the third bridge arm includes a third upper bridge arm switch tube Q5 and a third lower bridge arm switch tube Q6, and there is a third connection point C between the two, and the fourth bridge arm includes a fourth upper bridge arm switch tube Q7 and a fourth lower bridge arm switch tube Q8, and there is a fourth connection point D between the two. One end of the secondary side of the high-frequency transformer is connected to the third connection point C, and the other end of the secondary side of the high-frequency transformer is connected to the fourth connection point D.

[0045] When the bidirectional DCDC conversion circuit is working, the duty cycle of the control waveforms of all switch tubes can be 50% (or other values, which are only exemplary here), and the upper and lower bridge arm switch tubes of the same bridge arm are complementary to each other. At the same time, the dual phase shift control method of the bidirectional DCDC conversion circuit of the present application can be used to adjust the phase shift duty cycle (also called phase shift angle) between the control waveforms of the different bridge arm switch tubes to control the size and direction of the transmission power of the bidirectional DCDC conversion circuit. The bidirectional DCDC conversion circuit transfers energy through an LC series resonant circuit, staggers the phase of the terminal voltage of the switch tube and the current flowing through, realizes zero voltage conduction or zero current shutdown of the switch tube, reduces the switching loss of the conversion circuit, and makes the current of the high-frequency transformer close to a sine wave to reduce current harmonics, thereby reducing the core loss of the transformer. At the same time, the output current ripple of the conversion circuit can be improved through the filtering effect of the output side filter inductor L1.

[0046] The double phase shift control method of the bidirectional DCDC conversion circuit of the present application is described in detail below with reference to the accompanying drawings.

[0047] Figure 3 FIG. 1 is a flow chart of a dual phase shift control method of a bidirectional DCDC conversion circuit according to an embodiment of the present invention. Figure 3As shown, the dual-phase-shift control method for the bidirectional DCDC conversion circuit may include the following steps:

[0048] Step S101: Obtain the actual output voltage and the target output voltage of the bidirectional DCDC conversion circuit.

[0049] Specifically, when the bidirectional DCDC conversion circuit is operating, the actual output voltage of the bidirectional DCDC conversion circuit, that is, the output voltage of the low-voltage lagging side, can be collected by controlling a sampling chip. In the Figure 2 example shown, it is the voltage between LUDC+ and LUDC-. The target output voltage can be determined according to the actual situation.

[0050] Step S102: Obtain the inner-phase-shift duty cycle according to the actual output voltage and the target output voltage. The inner-phase-shift duty cycle is used to indicate the inter-bridge phase-shift duty cycle of the high-voltage leading side.

[0051] It should be noted that the inner-phase-shift duty cycle in this application refers to the inter-bridge phase-shift duty cycle of the high-voltage leading side. Specifically, it refers to Figure 2 the phase difference between the control waveforms of the switching tubes of the first bridge arm and the corresponding switching tubes of the second bridge arm in the example shown, and can be obtained through the actual output voltage and the target output voltage of the bidirectional DCDC conversion circuit.

[0052] In some embodiments, obtaining the inner-phase-shift duty cycle according to the actual output voltage and the target output voltage includes: obtaining the voltage difference between the target output voltage and the actual output voltage; performing PI (Proportion Integral) regulation on the voltage difference to obtain the inner-phase-shift duty cycle. In specific implementation, it can be obtained by adjusting through a PI controller. The input of the PI controller is the voltage difference between the target output voltage and the actual output voltage of the bidirectional DCDC conversion circuit, and the output is the inner-phase-shift duty cycle, and the output inner-phase-shift duty cycle is limited within the range of [0,1].

[0053] Further, to prevent the output of the PI controller from continuously increasing beyond the normal range and entering the saturation region, an anti-integral saturation algorithm can be added to the PI controller. Optionally, performing PI regulation on the voltage difference to obtain the inner phase-shifted duty ratio includes: obtaining the inner phase-shifted duty ratio at the previous control moment; if the inner phase-shifted duty ratio at the previous control moment is greater than the upper limit value, performing PI regulation on the negative voltage difference to obtain the inner phase-shifted duty ratio at the current control moment; if the inner phase-shifted duty ratio at the previous control moment is less than the lower limit value, performing PI regulation on the positive voltage difference to obtain the inner phase-shifted duty ratio at the current control moment. That is to say, when the PI controller calculates the inner phase-shifted duty ratio, it first determines whether the inner phase-shifted duty ratio at the previous control moment has exceeded the limit range [0, 1]. If it exceeds the upper limit value "1", then at the current control moment, only the negative voltage difference is accumulated, and the positive voltage difference is ignored; if it exceeds the lower limit value "0", then at the current control moment, only the positive voltage difference is accumulated, and the negative voltage difference is ignored, thereby preventing the inner phase-shifted duty ratio from staying in the saturation region for a long time.

[0054] Step S103, obtain a pre-determined outer phase-shifted duty ratio, where the outer phase-shifted duty ratio is used to indicate the phase-shifted duty ratio between the high-voltage leading side and the low-voltage lagging side of the bridge.

[0055] It should be noted that the outer phase-shifted duty ratio in this application refers to the phase-shifted duty ratio between the high-voltage leading side and the low-voltage lagging side of the bridge, specifically referring to Figure 2 the phase difference between the control waveforms of the switching tubes of the first bridge arm and the corresponding switching tubes of the third bridge arm in the shown example, which is a fixed value and can be obtained in advance by analyzing the transmission power of the bidirectional DCDC conversion circuit.

[0056] Specifically, it is known that the transmission power of the traditional phase-shifted control bidirectional DCDC conversion circuit is:

[0057]

[0058] Among them, P sps is the transmission power of the bidirectional DCDC conversion circuit, n is the transformer turns ratio, V1 is the input voltage of the bidirectional DCDC conversion circuit, V2 is the actual output voltage of the bidirectional DCDC conversion circuit, D is the phase-shifted duty ratio between the high-voltage leading side and the low-voltage lagging side of the bridge, f s is the switching frequency, and L s is the resonant inductor.

[0059] If the maximum transmission power of the bidirectional DCDC conversion circuit is used as the reference value, the per-unit value P s ' ps of the transmission power of the traditional phase-shifted control can be obtained:

[0060]

[0061] From the above relationship and the properties of traditional phase-shift control, it can be seen that the reverse transmission power and forward transmission power characteristics of the bidirectional DCDC conversion circuit are the same, and the positive or negative of the bridge-to-bridge phase-shift duty cycle D between the high-voltage leading side and the low-voltage lagging side determines the direction of the transmission power, and the absolute value determines the magnitude of the transmission power. When the absolute value of the bridge-to-bridge phase-shift duty cycle D between the high-voltage leading side and the low-voltage lagging side is 0.5, the transmission power is the largest, as Figure 4 shown, where the abscissa represents the bridge-to-bridge phase-shift duty cycle and the ordinate represents the per-unit value of the transmission power. It can be understood that the larger the transmission power, the higher the conversion efficiency of the bidirectional DCDC conversion circuit, that is, the smaller the switching loss and the smaller the energy loss.

[0062] For double phase-shift control, taking the phase-shift duty cycle 0 ≤ D1 ≤ D2 ≤ 1 as an example, the transmission power of the bidirectional DCDC conversion circuit is as follows:

[0063]

[0064] where D1 is the inner phase-shift duty cycle and D2 is the outer phase-shift duty cycle.

[0065] If the maximum transmission power is taken as the reference value and it is normalized, the per-unit value of the transmission power can be obtained as follows:

[0066] P sps ' = 2(-D1 2 + 2D1D2 - D1 - 2D2 2 + 2D2)(4)

[0067] Based on formula (4), a three-dimensional relationship diagram between the transmission power of double phase-shift control and the phase-shift duty cycle can be obtained, as Figure 5As shown, when the transmission power reaches the maximum value, the external phase-shift duty cycle D2 is approximately 0.5, while the internal phase-shift duty cycle D1 has an infinite number of solutions within the range of [0, 1]. Therefore, while setting the external phase-shift duty cycle D2 to 0.5, by performing PI regulation based on the voltage difference between the target output voltage and the actual output voltage of the bidirectional DCDC conversion circuit to obtain the internal phase-shift duty cycle D1, the actual output voltage can accurately track the target output voltage in real time, thereby obtaining the optimal solution of the internal phase-shift duty cycle D1. Therefore, in this application, for the external phase-shift duty cycle D2, it can be obtained according to the relationship between the transmission power and the phase-shift duty cycle in traditional phase-shift control and the relationship between the transmission power and the phase-shift duty cycle in dual-phase-shift control. Specifically, it can be determined according to the external phase-shift duty cycle when the transmission power of the bidirectional DCDC conversion circuit reaches the maximum, that is, the predetermined external phase-shift duty cycle is the external phase-shift duty cycle when the transmission power of the bidirectional DCDC conversion circuit reaches the maximum. Optionally, the value range of the predetermined external phase-shift duty cycle is 0.3 to 0.5. For the internal phase-shift duty cycle D1, it can be obtained by performing PI regulation based on the voltage difference between the target output voltage and the actual output voltage.

[0068] It should be noted that by first setting the external phase-shift duty cycle D2 to the external phase-shift duty cycle when the transmission power reaches the maximum, it can ensure that the maximum voltage output by the bidirectional DCDC conversion circuit is within the voltage range required for the battery to achieve full charge and discharge with equal current and constant voltage. For example, a certain string of batteries needs to reach 1000V to start, but now this string of batteries only has 980V. Therefore, the bidirectional DCDC conversion circuit needs to output 20V for compensation. If the bidirectional DCDC conversion circuit can only be adjusted between 0 and 10V, obviously this function cannot be achieved. Therefore, using the external phase-shift duty cycle at the maximum transmission rate as the external phase-shift duty cycle D2, and then performing PI regulation based on the voltage difference between the target output voltage and the actual output voltage of the bidirectional DCDC conversion circuit to obtain the internal phase-shift duty cycle D1 can minimize the peak current on the primary side of the transformer and maximize the transmission efficiency of the switching tube.

[0069] Further, in order to make the robustness of the dual-phase-shift control better, the externally determined phase-shift duty ratio may be corrected according to the internally determined phase-shift duty ratio. Optionally, correcting the externally determined phase-shift duty ratio according to the internally determined phase-shift duty ratio includes: obtaining the duty ratio difference between the internally determined phase-shift duty ratio and the externally determined phase-shift duty ratio; performing sliding mode control on the duty ratio difference to obtain the correction amount of the externally determined phase-shift duty ratio; and adding the correction amount to the externally determined phase-shift duty ratio to obtain the corrected externally determined phase-shift duty ratio. That is to say, in order to make the robustness of the dual-phase-shift control better, the relationship between the internally determined phase-shift duty ratio and the externally determined phase-shift duty ratio can be established through sliding mode control, that is, taking the difference between the internally determined phase-shift duty ratio and the externally determined phase-shift duty ratio as the input of the sliding mode controller, taking the correction amount of the externally determined phase-shift duty ratio as the output of the sliding mode controller, and finally adding the correction amount to the externally determined phase-shift duty ratio to obtain the corrected externally determined phase-shift duty ratio.

[0070] Specifically, referring to Figure 6 as shown, the target output voltage and the actual output voltage of the bidirectional DCDC conversion circuit can be used as the input quantities of the anti-integral saturation PI controller, and the output quantity is used as the internally determined phase-shift duty ratio D1. At the same time, the internally determined phase-shift duty ratio D1 and the externally determined phase-shift duty ratio are used as the input quantities of the sliding mode controller, and the correction amount of the externally determined phase-shift duty ratio is used as the output quantity of the sliding mode controller. Then, the sum of the externally determined phase-shift duty ratio and the correction amount is used as the final externally determined phase-shift duty ratio D2.

[0071] Step S104, controlling the bidirectional DCDC conversion circuit according to the internally determined phase-shift duty ratio and the externally determined phase-shift duty ratio.

[0072] Specifically, after obtaining the internally determined phase-shift duty ratio and the externally determined phase-shift duty ratio in the foregoing manner, pulse generation can be performed based on the two phase-shift duty ratios to Figure 2 control the switching tubes in the first full-bridge circuit and the second full-bridge circuit in, realize the soft-switching characteristics of the bidirectional DCDC conversion circuit, reduce the switching loss, improve the transmission efficiency, and at the same time ensure a high control accuracy.

[0073] In some embodiments, the bidirectional DCDC conversion circuit is controlled according to the internal phase-shift duty ratio and the external phase-shift duty ratio, including: the control waveforms of the first upper-bridge-arm switch tube and the first lower-bridge-arm switch tube of the first full-bridge circuit are complementary, the control waveforms of the second upper-bridge-arm switch tube and the second lower-bridge-arm switch tube of the first full-bridge circuit are complementary, and the phase difference between the control waveforms of the first upper-bridge-arm switch tube and the second upper-bridge-arm switch tube is the internal phase-shift duty ratio; the control waveforms of the third upper-bridge-arm switch tube and the third lower-bridge-arm switch tube of the second full-bridge circuit are complementary, the control waveforms of the fourth upper-bridge-arm switch tube and the fourth lower-bridge-arm switch tube of the second full-bridge circuit are complementary, and the phase difference between the control waveforms of the third upper-bridge-arm switch tube and the first upper-bridge-arm switch tube is the external phase-shift duty ratio. Further, optionally, controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio further includes: the control waveforms of the third upper-bridge-arm switch tube and the fourth lower-bridge-arm switch tube are the same, the control waveforms of the third lower-bridge-arm switch tube and the fourth upper-bridge-arm switch tube are the same; or, the phase difference between the control waveforms of the third upper-bridge-arm switch tube and the fourth upper-bridge-arm switch tube is the internal phase-shift duty ratio.

[0074] Specifically, referring to Figure 2 、 Figures 7 - 8 shown, when controlling the bidirectional DCDC conversion circuit, the switching frequencies of all switch tubes can be set to be the same, and the duty ratios are all 50%; at the same time, the control waveforms of the first upper-bridge-arm switch tube Q1 and the first lower-bridge-arm switch tube Q2 are complementary, the control waveforms of the second upper-bridge-arm switch tube Q3 and the second lower-bridge-arm switch tube Q4 are complementary, the control waveforms of the third upper-bridge-arm switch tube Q5 and the third lower-bridge-arm switch tube Q6 are complementary, the control waveforms of the fourth upper-bridge-arm switch tube Q7 and the fourth lower-bridge-arm switch tube Q8 are complementary, and a dead time is set between the upper and lower bridge-arm switch tubes of the same bridge arm, and this dead time accounts for the first ratio of half of the conduction period T hs For example, the range of the first ratio is [0, 0.1] to avoid short circuit caused by the simultaneous conduction of the upper and lower bridge-arm switch tubes of the same bridge arm; at the same time, the phase difference between the switch tubes of the first bridge arm and the corresponding switch tubes of the second bridge arm is set to be the internal phase-shift duty ratio D1, that is, the time when the second upper-bridge-arm switch tube Q3 lags behind the first upper-bridge-arm switch tube Q1 is D1T hs , and the time when the second lower-bridge-arm switch tube Q4 lags behind the first lower-bridge-arm switch tube Q2 is D1T hs ; at the same time, the phase difference between the switch tubes of the first bridge arm and the corresponding switch tubes of the third bridge arm is set to be the external phase-shift duty ratio D2, that is, the time when the third upper-bridge-arm switch tube Q5 lags behind the first upper-bridge-arm switch tube Q1 is D2T hs , and the time when the third lower-bridge-arm switch tube Q6 lags behind the first lower-bridge-arm switch tube Q2 is D2T hs ; at the same time, referring to Figure 7As shown, the control waveforms of the third lower-bridge arm switch Q6 and the fourth upper-bridge arm switch Q7 are the same, and the control waveforms of the third upper-bridge arm switch Q5 and the fourth lower-bridge arm switch Q8 are the same. Or, referring to Figure 8 As shown, it is set that the phase difference between the switch tubes of the fourth bridge arm and the corresponding switch tubes of the third bridge arm is shifted inward by the duty ratio D1, that is, the time when the fourth upper-bridge arm switch Q7 lags behind the third upper-bridge arm switch Q5 is D1T hs , and the time when the fourth lower-bridge arm switch Q8 lags behind the third lower-bridge arm switch Q6 is D1T hs .

[0075] To verify the actual effect of this application, the steady-state value of the voltage on the high-voltage leading side, that is, the input voltage V1, can be set to 1178V, the steady-state value of the load voltage on the low-voltage lagging side, that is, the actual output voltage V2, can be set to 10V, the parallel capacitor C1 on the input side is 10uf, the parallel capacitor C2 on the output side is 10000uF, and the switching frequency f s is 50kHz, the turns ratio n of the high-frequency transformer is 50, and the resonant inductor L s is 200uH, the filter inductor L1 on the low-voltage side is 3uH, and then simulation is carried out to obtain the simulation results as Figures 9 - 14 shown. Among them, Figure 9 is the waveform diagram of the primary current of the high-frequency transformer, Figure 10 is the waveform diagram of the secondary current of the high-frequency transformer, Figure 11 is the relationship diagram between the actual output voltage and the target output voltage, Figure 12 is the waveform diagram of the actual output voltage error, Figure 13 is the waveform diagram of the secondary voltage of the high-frequency transformer, Figure 14 is the waveform diagram of the primary voltage of the high-frequency transformer. It can be seen from Figures 9 - 14 that when the voltage on the high-voltage leading side of the bidirectional DCDC conversion circuit is 1146V and the target output voltage is 10V by using the method provided in this application, the maximum output voltage error is 0.00445V, the primary current is 2.23A, the secondary current is 75.96A, the primary voltage is 1146V, and the secondary voltage is 22.90V. The current stress of the conversion circuit is small and the tracking accuracy is high.

[0076] In summary, according to the double-phase-shift control method of the bidirectional DCDC conversion circuit in the embodiments of the present invention, not only can the soft-switching characteristics be realized, the switching loss can be reduced, and the transmission efficiency can be improved, but also the signals to be collected are few and the amount of calculation is smaller, which can meet the real-time requirements of the embedded system and has high control accuracy. In addition, no parameters such as resonant inductance and switching frequency need to be involved, only the turns ratio of the transformer and the voltage transmission ratio are required, and the dependence on parameters is low and the robustness is higher.

[0077] In some embodiments, embodiments of the present invention further provide a computer-readable storage medium, on which a dual-phase-shift control program for a bidirectional DCDC conversion circuit is stored. When the dual-phase-shift control program for the bidirectional DCDC conversion circuit is executed by a processor, the dual-phase-shift control method for the bidirectional DCDC conversion circuit as described above is implemented.

[0078] According to the computer-readable storage medium of the embodiments of the present invention, through the dual-phase-shift control method for the bidirectional DCDC conversion circuit as described above, the bidirectional DCDC conversion circuit can have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirement, and has a high control accuracy. At the same time, parameters such as phase-shifted inductance and switching frequency do not need to be involved, the dependence on parameters is small, and the robustness is high.

[0079] In some embodiments, embodiments of the present invention further provide a bidirectional DCDC controller, including: a memory, a processor, and a dual-phase-shift control program for a bidirectional DCDC conversion circuit stored on the memory and executable on the processor. When the processor executes the program, the dual-phase-shift control method as described above is implemented.

[0080] According to the bidirectional DCDC controller of the embodiments of the present invention, through the dual-phase-shift control method for the bidirectional DCDC conversion circuit as described above, the bidirectional DCDC conversion circuit can have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirement, and has a high control accuracy. At the same time, parameters such as phase-shifted inductance and switching frequency do not need to be involved, the dependence on parameters is small, and the robustness is high.

[0081] In some embodiments, embodiments of the present invention further provide a bidirectional DCDC converter, including a bidirectional DCDC conversion circuit and the aforementioned bidirectional DCDC controller.

[0082] According to the bidirectional DCDC converter of the embodiments of the present invention, through the aforementioned bidirectional DCDC controller, the bidirectional DCDC conversion circuit can have a smaller current stress, can achieve soft-switching characteristics, reduce switching losses, while requiring fewer signals to be collected and having a small amount of computation, can meet the real-time requirement, and has a high control accuracy. At the same time, parameters such as phase-shifted inductance and switching frequency do not need to be involved, the dependence on parameters is small, and the robustness is high.

[0083] Note that the logic and / or steps represented in the flowchart or described otherwise herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in combination with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection part with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other suitable processing as necessary, and then stored in a computer memory.

[0084] It should be understood that various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0085] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0086] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed 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 such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0087] In the present invention, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "coupled", "fixed", etc. should be construed broadly. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0088] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A dual-phase-shift control method for a bidirectional DCDC conversion circuit, characterized in that The bidirectional DCDC conversion circuit includes a high-voltage leading side and a low-voltage lagging side, and the method includes: Obtain the actual output voltage and the target output voltage of the bidirectional DCDC conversion circuit; Obtain an internal phase-shift duty ratio according to the actual output voltage and the target output voltage, where the internal phase-shift duty ratio is used to indicate the inter-bridge phase-shift duty ratio of the high-voltage leading side. Among them, obtaining the internal phase-shift duty ratio according to the actual output voltage and the target output voltage includes: obtaining the voltage difference between the target output voltage and the actual output voltage; performing PI regulation on the voltage difference through a PI controller to obtain the internal phase-shift duty ratio, where the input of the PI controller is the voltage difference and the output is the internal phase-shift duty ratio; Performing PI regulation on the voltage difference to obtain the internal phase-shift duty ratio includes: obtaining the internal phase-shift duty ratio at the previous control moment; if the internal phase-shift duty ratio at the previous control moment is greater than the upper limit value, performing PI regulation on the negative voltage difference to obtain the internal phase-shift duty ratio at the current control moment; if the internal phase-shift duty ratio at the previous control moment is less than the lower limit value, performing PI regulation on the positive voltage difference to obtain the internal phase-shift duty ratio at the current control moment; Obtain a pre-determined external phase-shift duty ratio, where the external phase-shift duty ratio is used to indicate the inter-bridge phase-shift duty ratio between the high-voltage leading side and the low-voltage lagging side. Among them, the pre-determined external phase-shift duty ratio is the external phase-shift duty ratio when the transmission power of the bidirectional DCDC conversion circuit reaches the maximum; Control the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio; The method further includes: Correct the pre-determined external phase-shift duty ratio according to the internal phase-shift duty ratio; The correcting the pre-determined external phase-shift duty ratio according to the internal phase-shift duty ratio includes: Obtain the duty ratio difference between the internal phase-shift duty ratio and the pre-determined external phase-shift duty ratio; Perform sliding mode control on the duty ratio difference to obtain the correction amount of the external phase-shift duty ratio; Superimpose the correction amount on the pre-determined external phase-shift duty ratio to obtain the corrected external phase-shift duty ratio.

2. The dual phase-shift control method for the bidirectional DCDC conversion circuit according to claim 1, wherein The value range of the pre-determined external phase-shift duty ratio is 0.3 to 0.

5.

3. The dual-phase-shift control method for the bidirectional DCDC conversion circuit according to claim 1, wherein The high-voltage leading side includes a first full-bridge circuit, and the low-voltage lagging side includes a second full-bridge circuit. Controlling the bidirectional DCDC conversion circuit according to the internal phase-shift duty ratio and the external phase-shift duty ratio includes: The control waveforms of the first upper-bridge-arm switch tube and the first lower-bridge-arm switch tube of the first full-bridge circuit are complementary, the control waveforms of the second upper-bridge-arm switch tube and the second lower-bridge-arm switch tube of the first full-bridge circuit are complementary, and the phases of the control waveforms of the first upper-bridge-arm switch tube and the second upper-bridge-arm switch tube differ by the internal phase-shift duty ratio; The control waveforms of the third upper-bridge-arm switch tube and the third lower-bridge-arm switch tube of the second full-bridge circuit are complementary, the control waveforms of the fourth upper-bridge-arm switch tube and the fourth lower-bridge-arm switch tube of the second full-bridge circuit are complementary, and the phase difference between the control waveforms of the third upper-bridge-arm switch tube and the first upper-bridge-arm switch tube is the external phase-shifted duty cycle.

4. The dual-phase-shift control method for the bidirectional DCDC conversion circuit according to claim 3, wherein, Controlling the bidirectional DCDC conversion circuit according to the internal phase-shifted duty cycle and the external phase-shifted duty cycle further includes: The control waveforms of the third upper-bridge-arm switch tube and the fourth lower-bridge-arm switch tube are the same, and the control waveforms of the third lower-bridge-arm switch tube and the fourth upper-bridge-arm switch tube are the same; or, The phase difference between the control waveforms of the third upper-bridge-arm switch tube and the fourth upper-bridge-arm switch tube is the internal phase-shifted duty cycle.

5. A computer-readable storage medium, characterized in that, It stores a dual-phase-shift control program for a bidirectional DCDC conversion circuit. When the dual-phase-shift control program of the bidirectional DCDC conversion circuit is executed by a processor, it implements the dual-phase-shift control method for the bidirectional DCDC conversion circuit according to any one of claims 1-4.

6. A bidirectional DCDC controller, characterized in that Comprising: A memory, a processor, and a dual-phase-shift control program for a bidirectional DCDC conversion circuit stored on the memory and executable on the processor. When the processor executes the program, it implements the dual-phase-shift control method for the bidirectional DCDC conversion circuit according to any one of claims 1-4.

7. A bidirectional DCDC converter, characterized in that, Comprising: A bidirectional DCDC conversion circuit and the bidirectional DCDC controller according to claim 6.

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