Loop controller, system, method, storage medium for a three-level dc-dc converter

Abstract

This invention discloses a loop controller, system, method, and storage medium for a three-level DC-DC converter. The invention provides a fault-tolerant control scheme when the output inductor current is uncertain during light-load operation in continuous mode. First, the charging and discharging modes are analyzed to make a rough judgment on the current direction. Then, the PWM signal supplied to the switching transistors is adjusted according to the charging and discharging modes. When the voltage of the flying capacitor is found to be far from the half-bus, the duty cycle of the corresponding switching transistor's PWM signal is adjusted in a timely manner to switch the charging and discharging state, ensuring that the voltage of the three-level flying capacitor always operates within the range near the half-bus. This invention can switch directions in a timely manner when abnormal operating modes occur without affecting the normal operation of the converter, ensuring that each switching transistor operates within the normal voltage stress range.

Description

Technical Field

[0001] This invention relates to the field of DC-DC bidirectional converters, and more particularly to a three-level DC-DC converter, loop controller, system, method, and storage medium. Background Technology

[0002] Three-level DC-DC bidirectional converters have many advantages over traditional two-level circuits, such as halved voltage stress on the switching transistors, lower inductor current ripple, and smaller inductor size. However, three-level DC-DC bidirectional converters have a large number of switching transistors, making control complex. The control scheme for balancing the flying capacitor is a major challenge, which has hindered the development of three-level circuits with flying capacitors.

[0003] Existing three-level flying capacitor voltage balancing control schemes are mostly used for unidirectional control applications. In this case, the direction of the inductor current is determined, and there is no need to consider the direction of the current; therefore, the control of the flying capacitor voltage is also unidirectional. However, in some bidirectional applications, the charging and discharging states are completely opposite. Therefore, the control strategy of unidirectional converters is not suitable for bidirectional converters. In bidirectional conversion, when operating in continuous current mode under light load conditions, the direction of the inductor current is uncertain after filtering due to sampling deviation and switching ripple. Therefore, misjudgment of the flying capacitor control direction is easy to occur. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art, which is that the direction of the flying capacitor control is prone to misjudgment when operating in continuous current mode under light load in bidirectional conversion. The present invention provides a three-level DC-DC converter and loop controller, system, method and storage medium.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] On one hand, a control method for a three-level DC-DC converter is provided, wherein the three-level DC-DC converter includes a first switch, a second switch, a third switch, and a fourth switch sequentially connected between the positive and negative terminals of a bus capacitor, and a flying capacitor is connected between the connection points of the first and second switches and the connection points of the third and fourth switches, characterized in that the method includes:

[0007] Mode determination steps: The current operating mode is determined based on the output inductor current of the three-level DC-DC converter and the filtered battery current of the three-level DC-DC converter. The operating mode includes charging mode and discharging mode.

[0008] Switch duty cycle adjustment steps: If the flying capacitor voltage of the flying capacitor is greater than the half bus capacitor voltage in charging mode, then increase the PWM signal duty cycle of the second switch and decrease the PWM signal duty cycle of the first switch; If the flying capacitor voltage is greater than the half bus capacitor voltage in discharging mode, then decrease the PWM signal duty cycle of the second switch and increase the PWM signal duty cycle of the first switch.

[0009] The PWM signals of the first and fourth switching transistors are complementary, as are the PWM signals of the second and third switching transistors.

[0010] Furthermore, in the control method described in this invention, the step of adjusting the duty cycle of the switching transistor specifically includes:

[0011] A preliminary PWM signal is obtained based on the real-time acquisition of the output inductor current and battery current.

[0012] The first difference is obtained by subtracting the half-bus capacitor voltage from the real-time collected flying capacitor voltage, and the first difference is input into the PI controller to obtain the first control quantity.

[0013] The adjustment amount is obtained by multiplying the first control quantity by the adjustment factor. The adjustment factor is 1 in charging mode and -1 in discharging mode.

[0014] The adjustment amount is added to the initial PWM signal to obtain the PWM signal of the first switching transistor;

[0015] The second difference is obtained by subtracting the adjustment amount from the initial PWM signal, and the second difference is shifted by 180 degrees to obtain the PWM signal of the second switching transistor.

[0016] Furthermore, in the control method described in this invention, a preliminary PWM signal is obtained based on the real-time acquired output inductor current and battery current, specifically including:

[0017] The reference current is subtracted from the battery current to obtain a third difference value, and the third difference value is input into the PI controller to obtain a second control quantity;

[0018] The output inductor current is subtracted from the second control value to obtain the fourth difference value. The fourth difference value is input into the PI controller to obtain the third control value, which serves as the initial PWM signal.

[0019] Furthermore, in the control method described in this invention, the mode determination step specifically includes:

[0020] The system pre-determines whether the battery current is greater than zero. If it is, it determines that the system is currently in charging mode; otherwise, it determines that the system is currently in discharging mode.

[0021] In charging mode, it is determined in real time whether the latest obtained first control quantity is greater than the preset value. If it is, it is determined that the current mode is switched to discharging mode.

[0022] In discharge mode, it is determined in real time whether the latest obtained first control quantity is greater than the preset value. If it is, it is determined that the current mode is switched to charging mode.

[0023] Secondly, a loop controller for a three-level DC-DC converter is constructed. The three-level DC-DC converter includes a first switch, a second switch, a third switch, and a fourth switch sequentially connected between the positive and negative terminals of a bus capacitor. A flying capacitor is connected between the connection points of the first and second switches and the connection points of the third and fourth switches. The loop controller includes:

[0024] The original loop control module is used to output PWM signals to the first switch, the second switch, the third switch, and the fourth switch.

[0025] The loop control adjustment module is used to adjust the PWM signal of the original loop control module, including: determining the current operating mode based on the output inductor current of the three-level DC-DC converter and the filtered battery current of the three-level DC-DC converter, wherein the operating mode includes charging mode and discharging mode; in the charging mode, when the flying capacitor voltage of the flying capacitor is greater than the half bus capacitor voltage, increasing the duty cycle of the PWM signal of the second switch and decreasing the duty cycle of the PWM signal of the first switch; and in the discharging mode, when the flying capacitor voltage is greater than the half bus capacitor voltage, decreasing the duty cycle of the PWM signal of the second switch and increasing the duty cycle of the PWM signal of the first switch corresponding to the flying capacitor voltage, wherein the PWM signals of the first switch and the fourth switch are complementary, and the PWM signals of the second switch and the third switch are complementary.

[0026] Furthermore, in the loop controller described in this invention, the original loop control module includes a preliminary PWM signal generation module and a phase shifter, and the original loop control module includes a first subtractor, a first PI controller, a charge / discharge mode determination module, a multiplier, a second subtractor, an adder, a first inverter, and a second inverter;

[0027] The preliminary PWM signal generation module is used to obtain a preliminary PWM signal based on the real-time acquired output inductor current and battery current, and input it into the second subtractor and adder;

[0028] The first subtractor is used to subtract the half-bus capacitor voltage from the real-time acquired flying capacitor voltage to obtain a first difference value and input it into the first PI controller.

[0029] The first PI controller derives a first control value based on the first difference and inputs it into the multiplier;

[0030] The charging / discharging mode determination module is used to set and input an adjustment factor into the multiplier. In the charging mode, the adjustment factor is 1, and in the discharging mode, the adjustment factor is -1.

[0031] The multiplier is used to multiply the first control quantity by the adjustment factor to obtain the adjustment quantity, and then input it into the second subtractor and adder.

[0032] The adder is used to add the adjustment amount to the initial PWM signal to obtain the PWM signal of the first switching transistor;

[0033] The second subtractor is used to subtract the adjustment amount from the initial PWM signal to obtain a second difference value and input it into the phase shifter;

[0034] The phase shifter is used to shift the second difference by 180 degrees to obtain the PWM signal of the second switching transistor;

[0035] The first inverter is used to invert the PWM signal of the first switching transistor to obtain the PWM signal of the fourth switching transistor;

[0036] The second inverter is used to invert the PWM signal of the second switch to obtain the PWM signal of the third switch.

[0037] Furthermore, in the loop controller described in this invention, the preliminary PWM signal generation module specifically includes a third subtractor, a fourth subtractor, a second PI controller, and a third PI controller.

[0038] The third subtractor is used to subtract the battery current from the reference current to obtain a third difference and input it into the second PI controller.

[0039] The second PI controller is used to obtain a second control quantity based on the third difference and input it into the fourth subtractor;

[0040] The fourth subtractor is used to subtract the output inductor current from the second control quantity to obtain a fourth difference value and input it into the third PI controller.

[0041] The third PI controller is used to obtain a third control quantity based on the fourth difference, and the third control quantity is used as the initial PWM signal and input to the second subtractor and adder.

[0042] Furthermore, in the loop controller described in this invention, the charging / discharging mode determination module is specifically used to pre-determine whether the battery current is greater than zero. If it is, it determines that the current mode is charging; otherwise, it determines that the current mode is discharging. In the charging mode, it determines in real time whether the latest obtained first control quantity is greater than a preset value. If it is, it determines that the current mode is switching to discharging. In the discharging mode, it determines in real time whether the latest obtained first control quantity is greater than a preset value. If it is, it determines that the current mode is switching to charging.

[0043] In three aspects, a control system for a three-level DC-DC converter is constructed, including a data acquisition module and the loop controller. The data acquisition module is used to acquire the flying capacitor voltage, the half-bus capacitor voltage, the output inductor current of the three-level DC-DC converter, and the battery current in real time.

[0044] Fourthly, a computer-readable storage medium is constructed, wherein the computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the control method described above.

[0045] Five aspects, constructing a computer-readable storage medium storing a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the control method as described in any of the preceding claims.

[0046] The three-level DC-DC converter, loop controller, system, method, and storage medium of the present invention have the following beneficial effects: The present invention provides a control scheme with fault tolerance when the inductor current is uncertain during light-load operation in continuous mode. First, the charging and discharging mode is analyzed to make a rough judgment on the current direction. Then, the PWM signal given to the switching transistor is adjusted according to the charging and discharging mode. When it is found that the voltage of the flying capacitor is far away from the half bus, the duty cycle of the PWM signal of the corresponding switching transistor is adjusted in time to switch the charging and discharging state, so that the voltage of the three-level flying capacitor always operates in the range near the half bus. When the working mode is abnormal, the present invention can switch the direction in time without affecting the normal operation of the converter, ensuring that each switching transistor operates within the normal voltage stress range. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort:

[0048] Figure 1This is a schematic diagram of the three-level DC-DC converter of the present invention;

[0049] Figure 2 This is a flowchart of the control method for a three-level DC-DC converter;

[0050] Figure 3 This is a flowchart of the steps for adjusting the duty cycle of the switching transistor;

[0051] Figure 4 This is a flowchart of the pattern determination steps;

[0052] Figure 5 This is a schematic diagram of the loop control model within the loop controller. Detailed Implementation

[0053] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete. It should be understood that the embodiments of the present invention and the specific features thereof are detailed descriptions of the technical solutions of this application, and not limitations thereof. Where there is no conflict, the embodiments of the present invention and the technical features thereof can be combined with each other.

[0054] Example 1

[0055] refer to Figure 1 The three-level DC-DC converter of the present invention includes a first switch Q1, a second switch Q2, a third switch Q3 and a fourth switch Q4, an inductor L1, and the switches Q1-Q4 are controlled by a control system, which includes a data acquisition module and a loop controller.

[0056] The first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 are sequentially connected between the positive and negative terminals of the bus capacitor C30. A flying capacitor C1 is connected between the connection point of the first switch Q1 and the second switch Q2 and the connection point of the third switch Q3 and the fourth switch Q4. The connection point of the second switch Q2 and the third switch Q3 is connected to the negative terminal of the bus capacitor C3 through inductor L1 and filter capacitor C2. The first switch Q1 and the second switch Q2 operate alternately, as do the third switch Q3 and the fourth switch Q4. The first switch Q1 and the fourth switch Q4 are complementary and mutually conductive, as are the second switch Q2 and the third switch Q3.

[0057] The acquisition module is used to acquire, in real time, the flying capacitor voltage Vflycap, the half-bus capacitor voltage Vbus / 2, the output inductor current Ind, and the battery current Ibat. The acquired information is then sent to the loop controller, which executes the method of this invention.

[0058] For details, please refer to Figure 2 The method includes:

[0059] S101, Mode determination step: Determine the current working mode based on the output inductor current Ind and battery current Ibat of the three-level DC-DC converter. The working mode includes charging mode and discharging mode.

[0060] S102. Steps for adjusting the duty cycle of the switching transistor:

[0061] If the flying capacitor voltage Vflycap of the flying capacitor C1 is greater than the half bus capacitor voltage Vbus / 2 in the charging mode, then the duty cycle of the PWM signal of the second switch Q2 is increased and the duty cycle of the PWM signal of the first switch Q1 is decreased.

[0062] If the flying capacitor voltage Vflycap is greater than the half bus capacitor voltage Vbus / 2 in the discharge mode, then the duty cycle of the PWM signal of the second switch Q2 is reduced and the duty cycle of the PWM signal of the first switch Q1 is increased.

[0063] It should be noted that in step S102, no matter how the PWM signals of the first switch Q1 and the second switch Q2 change, the PWM signals of the first switch Q1 and the fourth switch Q4 are always complementary, and the PWM signals of the second switch Q2 and the third switch Q3 are always complementary.

[0064] The following is combined Figure 3 Step S102 will be described in detail, and step S102 specifically includes:

[0065] S1021: Subtract the battery current Ibat from the reference current Ibat_Ref to obtain the third difference D3, and input the third difference D3 into the PI controller to obtain the second control quantity Ind_Ref;

[0066] A PI controller, also known as a proportional-integral controller, takes the error between the given signal and the feedback signal as its input. The integral is the sum of the errors and then multiplied by the integral coefficient, while the proportional is the error multiplied by the proportional coefficient. The sum of these two is the output of the PI controller.

[0067] S1022: Subtract the output inductor current Ind of the three-level DC-DC converter from the second control quantity Ind_Ref to obtain the fourth difference value D4. Input the fourth difference value D4 into the PI controller to obtain the third control quantity. The third control quantity is used as the initial PWM signal PWM_out.

[0068] In the prior art, the initial PWM signal PWM_out is generally used directly as the PWM signal Q1_PWM of the first switch Q1, and the initial PWM signal PWM_out is shifted 180 degrees as the PWM signal Q2_PWM of the second switch Q2. However, the present invention does not do this. Instead, the initial PWM signal PWM_out is adjusted in different ways through the following steps S1023-S1025 to adjust the PWM signal of the switch.

[0069] S1023: Subtract the half-bus capacitor voltage Vbus / 2 from the real-time collected flying capacitor voltage Vflycap to obtain the first difference D1, and input the first difference D1 into the PI controller to obtain the first control quantity Fly_output;

[0070] S1024: Multiply the first control quantity Fly_output by the adjustment factor to obtain the adjustment quantity M1. The adjustment factor is 1 in charging mode and -1 in discharging mode.

[0071] S1025: Add the adjustment amount M1 to the preliminary PWM signal PWM_out to obtain the PWM signal Q1_PWM of the first switch Q1; subtract the adjustment amount M1 from the preliminary PWM signal PWM_out to obtain the second difference D1; shift the second difference D1 by 180 degrees to obtain the PWM signal Q2_PWM of the second switch Q2; invert the PWM signal Q1_PWM of the first switch Q1 to obtain the PWM signal Q4_PWM of the fourth switch Q4; invert the PWM signal Q2_PWM of the second switch Q2 to obtain the PWM signal Q3_PWM of the third switch Q3.

[0072] refer to Figure 4 The following is a detailed description of step S101, which specifically includes:

[0073] S1011: Pre-determine whether the battery current Ibat is greater than zero. If it is, determine that the current is in charging mode; otherwise, determine that the current is in discharging mode.

[0074] S1012: In charging mode, determine in real time whether the latest obtained first control quantity Fly_output is greater than a preset value. If it is, determine that the current mode is switched to discharging mode.

[0075] S1013: In discharge mode, determine in real time whether the latest obtained first control quantity Fly_output is greater than the preset value. If it is, determine that the current mode is switched to charging mode.

[0076] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods.

[0077] Example 2

[0078] This embodiment is a... Figure 1 The specific details of the loop controller are disclosed. (See reference...) Figure 5 The loop controller includes a primary loop control module 100 and a loop control adjustment module 200. Primary loop control module 100.

[0079] The original loop control module 100 is a loop control model in the prior art, used to output PWM signals to the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4.

[0080] This embodiment is essentially an adjustment and improvement of the existing loop control model. The loop control adjustment module 200 is the improved part of this embodiment relative to the existing loop control model. It is used to adjust the PWM signal of the original loop control module 100, including: determining the current working mode based on the output inductor current Ind and the battery current Ibat of the three-level DC-DC converter. The working mode includes charging mode and discharging mode. In the charging mode, when the flying capacitor voltage Vflycap of the flying capacitor C1 is greater than the half bus capacitor voltage Vbus / 2, the duty cycle of the PWM signal of the second switch Q2 is increased and the duty cycle of the PWM signal of the first switch Q1 is decreased. In the discharging mode, when the flying capacitor voltage Vflycap is greater than the half bus capacitor voltage Vbus / 2, the duty cycle of the PWM signal of the second switch Q2 is decreased and the duty cycle of the PWM signal of the first switch Q1 corresponding to the flying capacitor voltage Vflycap is increased. The PWM signals of the first switch Q1 and the fourth switch Q4 are complementary, and the PWM signals of the second switch Q2 and the third switch Q3 are complementary.

[0081] More specifically, the original loop control module 100 includes a preliminary PWM signal generation module 101 and a phase shifter. The original loop control module 100 includes a first subtractor, a first PI controller, a charge / discharge mode determination module, a multiplier, a second subtractor, an adder, a first inverter, and a second inverter.

[0082] The preliminary PWM signal generation module 101 is used to obtain a preliminary PWM signal PWM_out based on the real-time acquired output inductor current Ind and battery current Ibat, and input it into the second subtractor and adder.

[0083] The first subtractor is used to subtract the half-bus capacitor voltage Vbus / 2 from the real-time acquired flying capacitor voltage Vflycap to obtain a first difference D1 and input it into the first PI controller.

[0084] The first PI controller obtains a first control quantity Fly_output based on the first difference D1 and inputs it into the multiplier;

[0085] The charging / discharging mode determination module is used to set and input an adjustment factor into the multiplier. In the charging mode, the adjustment factor is 1, and in the discharging mode, the adjustment factor is -1.

[0086] The multiplier is used to multiply the first control quantity Fly_output by the adjustment factor to obtain the adjustment quantity M1, and then input it into the second subtractor and adder.

[0087] The adder is used to add the adjustment amount M1 to the initial PWM signal PWM_out to obtain the PWM signal Q1_PWM of the first switch Q1.

[0088] The second subtractor is used to subtract the adjustment amount M1 from the initial PWM signal PWM_out to obtain a second difference D1 and input it into the phase shifter;

[0089] The phase shifter is used to shift the second difference D1 by 180 degrees to obtain the PWM signal Q2_PWM of the second switch Q2;

[0090] The first inverter is used to invert the PWM signal Q1_PWM of the first switch Q1 to obtain the PWM signal Q4_PWM of the fourth switch Q4;

[0091] The second inverter is used to invert the PWM signal Q2_PWM of the second switch Q2 to obtain the PWM signal Q3_PWM of the third switch Q3.

[0092] Furthermore, the preliminary PWM signal generation module specifically includes a third subtractor, a fourth subtractor, a second PI controller, and a third PI controller.

[0093] The third subtractor is used to subtract the battery current Ibat from the reference current Ibat_Ref to obtain a third difference D3 and input it into the second PI controller.

[0094] The second PI controller is used to obtain the second control quantity Ind_Ref based on the third difference D3 and input it into the fourth subtractor;

[0095] The fourth subtractor is used to subtract the output inductor current Ind from the second control quantity Ind_Ref to obtain a fourth difference value D4 and input it into the third PI controller.

[0096] The third PI controller is used to obtain a third control quantity based on the fourth difference D4, and the third control quantity is used as the initial PWM signal PWM_out and input to the second subtractor and adder.

[0097] Furthermore, the charging / discharging mode determination module is specifically used to pre-determine whether the battery current Ibat is greater than zero. If it is, it determines that the current mode is charging; otherwise, it determines that the current mode is discharging. In charging mode, it determines in real time whether the latest obtained first control quantity Fly_output is greater than a preset value. If it is, it determines that the current mode is switching to discharging mode. In discharging mode, it determines in real time whether the latest obtained first control quantity Fly_output is greater than a preset value. If it is, it determines that the current mode is switching to charging mode.

[0098] Example 3

[0099] refer to Figure 1 This embodiment is... Figure 1 The control system of the three-level DC-DC converter is disclosed in detail. The system includes an acquisition module and a loop controller as described in Embodiment 2. The acquisition module is used to acquire the flying capacitor voltage Vflycap, the half bus capacitor voltage Vbus / 2, the output inductor current Ind, and the battery current Ibat in real time.

[0100] Specifically, the acquisition module includes:

[0101] The flying capacitor voltage acquisition module is connected to both ends of the flying capacitor C1 and is used to acquire the flying capacitor voltage Vflycap across the flying capacitor C1 in real time.

[0102] The bus capacitor voltage acquisition module is connected to both ends of the bus capacitor C3 to acquire the bus capacitor voltage Vbus, and then obtain the half bus capacitor voltage Vbus / 2.

[0103] The output inductor current acquisition module, connected in series with inductor L1, is used to acquire the output inductor current Iind of the three-level DC-DC converter;

[0104] The battery current acquisition module is connected to the battery terminal and is used to acquire the filtered battery current Ibat from the three-level DC-DC converter.

[0105] The voltage sampling module and current sampling module mentioned above can be implemented based on traditional sampling techniques, and will not be expanded upon here.

[0106] Example 4

[0107] This embodiment discloses a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the steps of the control method as described in Embodiment 1. The specific implementation process is described in Embodiment 1 and will not be repeated here.

[0108] In summary, the loop controller, system, method, and storage medium of the three-level DC-DC converter of the present invention have the following beneficial effects: The present invention provides a control scheme with fault tolerance when the inductor current is uncertain during light-load operation in continuous mode. First, the charging and discharging mode is analyzed to make a rough judgment on the current direction. Then, the PWM signal given to the switching transistor is adjusted according to the charging and discharging mode. When it is found that the voltage of the flying capacitor is far away from the half bus, the duty cycle of the PWM signal of the corresponding switching transistor is adjusted in time to switch the charging and discharging state, so that the voltage of the three-level flying capacitor always operates in the range near the half bus. When the working mode is abnormal, the present invention can switch the direction in time without affecting the normal operation of the converter, ensuring that each switching transistor operates within the normal voltage stress range.

[0109] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0110] The terms "first," "second," and other ordinal numbers used in this specification are used to describe various constituent elements, but these constituent elements are not limited by these terms. The purpose of using these terms is solely to distinguish one constituent element from others. For example, without departing from the scope of the invention, a first constituent element may be named a second constituent element, and similarly, a second constituent element may be named a first constituent element. The term "connected" or "linked" includes not only directly connecting two entities but also indirectly connecting them through other entities that have beneficial improvement effects.

[0111] The foregoing description relates to various modules. These modules typically include hardware and / or combinations of hardware and software (e.g., embedded software). It should be noted that the division of these modules in the above description is for clarity. However, in actual implementation, the boundaries between the various modules may be blurred. For example, any or all functional modules herein may share various hardware and / or software elements. As another example, any and / or all functional modules herein may be wholly or partially implemented by a shared processor executing software instructions. Furthermore, various software sub-modules executed by one or more processors may be shared among various software modules. Accordingly, unless expressly required, the scope of this invention is not limited by mandatory boundaries between various hardware and / or software elements.

[0112] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A control method for a three-level DC-DC converter, the three-level DC-DC converter comprising a first switch (Q1), a second switch (Q2), a third switch (Q3), and a fourth switch (Q4) sequentially connected between the positive and negative terminals of a bus capacitor (C3), wherein a flying capacitor (C1) is connected between the connection point of the first switch (Q1) and the second switch (Q2) and the connection point of the third switch (Q3) and the fourth switch (Q4), characterized in that, The method includes: Mode determination steps: The current operating mode is determined based on the output inductor current (Iind) of the three-level DC-DC converter and the filtered battery current (Ibat) of the three-level DC-DC converter. The operating mode includes charging mode and discharging mode. Switch duty cycle adjustment steps: If the flying capacitor voltage (Vflycap) of the flying capacitor (C1) is greater than the half bus capacitor voltage (Vbus / 2) in charging mode, then increase the PWM signal duty cycle of the second switch (Q2) and decrease the PWM signal duty cycle of the first switch (Q1); if the flying capacitor voltage (Vflycap) is greater than the half bus capacitor voltage (Vbus / 2) in discharging mode, then decrease the PWM signal duty cycle of the second switch (Q2) and increase the PWM signal duty cycle of the first switch (Q1). Among them, the PWM signals of the first switch (Q1) and the fourth switch (Q4) are complementary, and the PWM signals of the second switch (Q2) and the third switch (Q3) are complementary.

2. The control method according to claim 1, characterized in that, The duty cycle adjustment steps for the switching transistor specifically include: The initial PWM signal (PWM_out) is obtained based on the real-time acquisition of the output inductor current (Iind) and battery current (Ibat); The first difference (D1) is obtained by subtracting the half bus capacitor voltage (Vbus / 2) from the real-time acquired flying capacitor voltage (Vflycap). The first difference (D1) is then input into the PI controller to obtain the first control quantity (Fly_output). The adjustment amount (M1) is obtained by multiplying the first control quantity (Fly_output) by the adjustment factor. The adjustment factor is 1 in charging mode and -1 in discharging mode. The initial PWM signal (PWM_out) is added to the adjustment amount (M1) to obtain the PWM signal (Q1_PWM) of the first switching transistor (Q1); Subtract the adjustment amount (M1) from the initial PWM signal (PWM_out) to obtain the second difference (D2), and shift the second difference (D2) by 180 degrees to obtain the PWM signal (Q2_PWM) of the second switch (Q2).

3. The control method according to claim 2, characterized in that, The initial PWM signal (PWM_out) is obtained based on the real-time acquired output inductor current (Iind) and battery current (Ibat), specifically including: Subtracting the battery current (Ibat) from the reference current (Ibat_Ref) yields a third difference (D3), which is then input into the PI controller to obtain a second control value (Iind_Ref). Subtracting the output inductor current (Iind) from the second control quantity (Iind_Ref) yields a fourth difference (D4). The fourth difference (D4) is then input into the PI controller to obtain a third control quantity, which serves as the initial PWM signal (PWM_out).

4. The control method according to claim 3, characterized in that, The pattern determination step specifically includes: It is determined in advance whether the battery current (Ibat) is greater than zero. If it is, it is determined that the current mode is charging; otherwise, it is determined that the current mode is discharging. In charging mode, it is determined in real time whether the latest obtained first control quantity (Fly_output) is greater than the preset value. If it is, it is determined that the current mode is switched to discharging mode. In discharge mode, it is determined in real time whether the latest obtained first control quantity (Fly_output) is greater than the preset value. If it is, it is determined that the current mode is switched to charging mode.

5. A loop controller for a three-level DC-DC converter, the three-level DC-DC converter comprising a first switch (Q1), a second switch (Q2), a third switch (Q3), and a fourth switch (Q4) sequentially connected between the positive and negative terminals of a bus capacitor (C3), wherein a flying capacitor (C1) is connected between the connection point of the first switch (Q1) and the second switch (Q2) and the connection point of the third switch (Q3) and the fourth switch (Q4), characterized in that, The loop controller includes: The original loop control module (100) is used to output PWM signals to the first switch (Q1), the second switch (Q2), the third switch (Q3) and the fourth switch (Q4); The loop control adjustment module (200) is used to adjust the PWM signal of the original loop control module (100), including: determining the current operating mode based on the output inductor current (Iind) of the three-level DC-DC converter and the filtered battery current (Ibat) of the three-level DC-DC converter, wherein the operating mode includes charging mode and discharging mode; when the flying capacitor voltage (Vflycap) of the flying capacitor (C1) is greater than the half bus capacitor voltage (Vbus / 2) in the charging mode, increasing the P of the second switch (Q2). The duty cycle of the PWM signal of the first switch (Q1) is reduced, and when the flying capacitor voltage (Vflycap) is greater than the half bus capacitor voltage (Vbus / 2) in the discharge mode, the duty cycle of the PWM signal of the second switch (Q2) is reduced and the duty cycle of the PWM signal of the first switch (Q1) corresponding to the flying capacitor voltage (Vflycap) is increased. The PWM signals of the first switch (Q1) and the fourth switch (Q4) are complementary, and the PWM signals of the second switch (Q2) and the third switch (Q3) are complementary.

6. The loop controller according to claim 5, characterized in that, The original loop control module (100) includes a preliminary PWM signal generation module (101) and a phase shifter. The original loop control module (100) includes a first subtractor, a first PI controller, a charge / discharge mode determination module, a multiplier, a second subtractor, an adder, a first inverter, and a second inverter. The preliminary PWM signal generation module (101) is used to obtain a preliminary PWM signal (PWM_out) based on the real-time acquired output inductor current (Iind) and battery current (Ibat), and input it into the second subtractor and adder; The first subtractor is used to subtract the half-bus capacitor voltage (Vbus / 2) from the real-time acquired flying capacitor voltage (Vflycap) to obtain a first difference (D1) and input it into the first PI controller. The first PI controller obtains a first control quantity (Fly_output) based on the first difference (D1) and inputs it into the multiplier; The charging / discharging mode determination module is used to set and input an adjustment factor into the multiplier. In the charging mode, the adjustment factor is 1, and in the discharging mode, the adjustment factor is -1. The multiplier is used to multiply the first control quantity (Fly_output) by the adjustment factor to obtain the adjustment quantity (M1), and then input it into the second subtractor and adder; The adder is used to add the adjustment amount (M1) to the initial PWM signal (PWM_out) to obtain the PWM signal (Q1_PWM) of the first switching transistor (Q1); The second subtractor is used to subtract the adjustment amount (M1) from the initial PWM signal (PWM_out) to obtain a second difference (D2) and input it into the phase shifter; The phase shifter is used to shift the second difference (D2) by 180 degrees to obtain the PWM signal (Q2_PWM) of the second switch (Q2); The first inverter is used to invert the PWM signal (Q1_PWM) of the first switch (Q1) to obtain the PWM signal (Q4_PWM) of the fourth switch (Q4); The second inverter is used to invert the PWM signal (Q2_PWM) of the second switch (Q2) to obtain the PWM signal (Q3_PWM) of the third switch (Q3).

7. The loop controller according to claim 6, characterized in that, The preliminary PWM signal generation module specifically includes a third subtractor, a fourth subtractor, a second PI controller, and a third PI controller. The third subtractor is used to subtract the battery current (Ibat) from the reference current (Ibat_Ref) to obtain a third difference (D3) and input it into the second PI controller; The second PI controller is used to obtain a second control quantity (Iind_Ref) based on the third difference (D3) and input it into the fourth subtractor; The fourth subtractor is used to subtract the output inductor current (Iind) from the second control quantity (Iind_Ref) to obtain a fourth difference (D4) and input it into the third PI controller; The third PI controller is used to obtain a third control quantity based on the fourth difference (D4), and the third control quantity is used as the initial PWM signal (PWM_out) and input to the second subtractor and adder.

8. The loop controller according to claim 6, characterized in that, The charging / discharging mode determination module is specifically used to pre-determine whether the battery current (Ibat) is greater than zero. If it is, it determines that the current mode is charging; otherwise, it determines that the current mode is discharging. In charging mode, it determines in real time whether the latest obtained first control quantity (Fly_output) is greater than a preset value. If it is, it determines that the current mode is switching to discharging mode. In discharging mode, it determines in real time whether the latest obtained first control quantity (Fly_output) is greater than a preset value. If it is, it determines that the current mode is switching to charging mode.

9. A control system for a three-level DC-DC converter, characterized in that, It includes a data acquisition module and a loop controller as described in any one of claims 5-8, wherein the data acquisition module is used to acquire in real time the flying capacitor voltage (Vflycap), the half bus capacitor voltage (Vbus / 2), the output inductor current (Iind) of the three-level DC-DC converter, and the battery current (Ibat).

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the control method as described in any one of claims 1 to 4 above.

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