CN115224952B

CN115224952B - Control method of bidirectional power converter and bidirectional power converter

Info

Publication number: CN115224952B
Application number: CN202211134253.9A
Authority: CN
Inventors: 孙礼貌
Original assignee: If New Energy Technology Jiangsu Co ltd
Current assignee: If New Energy Technology Jiangsu Co ltd
Priority date: 2022-09-19
Filing date: 2022-09-19
Publication date: 2023-01-17
Anticipated expiration: 2042-09-19
Also published as: CN115224952A; WO2024060728A1

Abstract

The application relates to a control method of a bidirectional power conversion device and the bidirectional power conversion device, wherein the bidirectional power conversion device comprises at least one first switching tube, a control output value is determined according to an output parameter of the bidirectional power conversion device, the switching frequency of the first switching tube and the duty ratio of a driving signal of the first switching tube are adjusted according to the control output value, and the first switching tube is controlled to work in a constant-frequency variable-duty-ratio mode in response to the control output value meeting a first preset condition; or, in response to the control output value meeting a second preset condition, controlling the first switching tube to work in a fixed-frequency fixed-duty ratio mode; or, in response to the control output value meeting a third preset condition, controlling the first switching tube to work in a variable-frequency constant-duty-ratio mode. By adopting the mode, the bidirectional power conversion device adopts different control modes according to different conditions, so that the switching loss of the bidirectional power conversion device can be reduced, and the stability of the output voltage of the bidirectional power conversion device is improved.

Description

Control method of bidirectional power converter and bidirectional power converter

Technical Field

The present invention relates to the field of power conversion devices, and in particular, to a method for controlling a bidirectional power conversion device and a bidirectional power conversion device.

Background

A power converter is a kind of power electronic equipment that can convert some kind of current into other kinds of current, and includes a dc converter and an ac converter, etc., for example, the dc converter can convert one kind of dc input into another kind of dc output with different output characteristics. The direct current converter is widely applied to the field of power supplies of motor homes, and can be connected between a high-power storage battery and motor home electric equipment or a charging power supply to realize bidirectional electric energy conversion. The bidirectional full-bridge resonant converter is a known direct-current power conversion device, and when the input voltage range is wide, the gain of the bidirectional full-bridge resonant converter can be changed in a frequency modulation mode, so that the requirement of voltage stabilization is met.

However, this power conversion device is mainly suitable for an application scenario where the battery voltage is high, and thus a design of a small voltage transformation ratio can be realized, for example, when the battery voltage is 48V and the output voltage is 400V, the voltage transformation ratio is about 10 times (48v 400v) at the maximum, or when the battery voltage is 48V and the output voltage is 200V, the voltage transformation ratio is about 5 times (48v 200v). However, when such a converter is used for a 12V-class battery, the voltage conversion ratio is 40 times (12v. In addition, when the frequency modulation control method is adopted, when the input voltage range is wide, in order to meet the requirement of gain, the frequency is raised without limitation, and the switching loss is also greatly improved.

The foregoing description is provided to provide general technical information, and is not necessarily prior art.

Disclosure of Invention

In view of the above, it is necessary to provide a control method for a bidirectional power converter and a bidirectional power converter, which can be applied to a wide voltage range and high voltage transformation ratio scenario to solve at least the problems of high switching loss, low efficiency and power density, and high cost in the related art.

In a first aspect, the present application provides a control method for a bidirectional power conversion apparatus, where the bidirectional power conversion apparatus includes at least one first switching tube, and the control method includes:

determining a control output value according to the output parameters of the bidirectional power conversion device;

adjusting the switching frequency of the first switching tube and the duty ratio of a driving signal of the first switching tube according to the control output value; wherein the content of the first and second substances,

responding to the control output value meeting a first preset condition, and controlling the first switching tube to work in a constant-frequency variable-duty-ratio mode; alternatively, the first and second liquid crystal display panels may be,

responding to the control output value meeting a second preset condition, and controlling the first switching tube to work in a fixed-frequency fixed-duty ratio mode; alternatively, the first and second electrodes may be,

and controlling the first switching tube to work in a variable-frequency constant-duty-ratio mode in response to the control output value meeting a third preset condition.

In a second aspect, the present application further provides a bidirectional power conversion apparatus, which includes a control unit and at least one first switch tube, where the control unit is configured to execute the control method.

As described above, the present application provides a control method of a bidirectional power converter and a bidirectional power converter, the bidirectional power converter including at least one first switching tube, the control method including: determining a control output value according to an output parameter of the bidirectional power conversion device, and adjusting the switching frequency of the first switching tube and the duty ratio of a driving signal of the first switching tube according to the control output value, wherein the first switching tube is controlled to work in a constant-frequency variable-duty-ratio mode in response to the control output value meeting a first preset condition; or, in response to the control output value meeting a second preset condition, controlling the first switching tube to work in a fixed-frequency fixed-duty ratio mode; or, in response to the control output value meeting a third preset condition, controlling the first switching tube to work in a variable-frequency constant-duty-ratio mode.

Has the advantages that: by adopting the mode, different control modes are adopted for the bidirectional power conversion device according to different conditions, the switching loss of the bidirectional power conversion device can be reduced, and the stability of the output voltage of the bidirectional power conversion device is improved.

The above summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. The above summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application. In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. The drawings and written description are not intended to limit the scope of the inventive concepts in any manner, but rather to illustrate the concepts of the application by those skilled in the art with reference to specific embodiments.

FIG. 1 is a schematic diagram of a bidirectional power conversion apparatus according to an embodiment;

fig. 2 is a flowchart of a control method of a bidirectional power conversion apparatus in one embodiment;

fig. 3 is a flowchart of a control method of a bidirectional power conversion apparatus in another embodiment;

fig. 4 is a flowchart of a control method of a bidirectional power conversion apparatus in still another embodiment;

fig. 5 is a flowchart of a control method of a bidirectional power conversion apparatus in still another embodiment;

fig. 6 is a schematic circuit diagram of a bidirectional power conversion apparatus according to an embodiment;

FIG. 7 is a timing diagram illustrating the switching of the switching transistors Q1, Q2 according to one embodiment;

FIG. 8 is a timing diagram of the switching transistors Q3/Q6, Q4/Q5 in one embodiment;

FIG. 9 is a schematic diagram of bridge arm 0 voltage turn-on of the push-pull unit in one embodiment;

FIG. 10 is a schematic diagram of an embodiment of a bridge arm 0 current shutdown of a rectifier bridge circuit;

FIG. 11 is a timing diagram of the switching transistors Q3/Q6, Q4/Q5 of the bridge arms of the bridge circuit of the rectifier bridge according to one embodiment;

FIG. 12 is a timing diagram of the switching transistors Q1, Q2 of the push-pull unit bridge arm in one embodiment;

FIG. 13 is a schematic diagram of an embodiment of bridge arm 0 voltage turn-on of a rectifier bridge circuit;

FIG. 14 is a schematic diagram of an embodiment of a push-pull unit synchronous rectification 0 current turn-off;

FIG. 15 is a flow chart illustrating control of the control unit to obtain control output values according to one embodiment;

fig. 16 is a detailed flowchart of a control method of the bidirectional power converting apparatus according to an embodiment;

FIG. 17 is a flow chart of small pulse modulation in charge mode and discharge mode of a method for controlling a bi-directional power converter in one embodiment;

fig. 18 is a simulation diagram of generating a driving signal of a switching tube of a bidirectional power conversion device in one embodiment.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a component of' 8230; \8230;" does not exclude the presence of another like element in a process, method, article, or apparatus that comprises the element. It will be further understood that, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context indicates otherwise. Also, as used herein, the terms "or," "and/or," "including at least one of the following," and the like, may be construed as being inclusive or meaning any one or any combination. An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.

It should be understood that although the terms first, second, third, etc. may be used herein to describe various parameters or modules, these parameters or modules should not be limited by these terms. These terms are only used to distinguish one type of parameter or module from another. For example, a first parameter may also be referred to as a second parameter, and similarly, a second parameter may also be referred to as a first parameter, without departing from the scope herein. The words "if", as used herein may be interpreted as "at \8230; \8230whenor" when 8230; \8230when or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context. Furthermore, the parts, features and elements that have the same name in different embodiments of the application may have the same meaning or may have different meanings, and the specific meaning thereof should be determined by the explanation thereof in the specific embodiment or further by combining the context in the specific embodiment.

It should be understood that, although the steps in the flowcharts in the embodiments of the present application are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and may be performed in other orders unless explicitly stated herein. Moreover, at least some of the steps in the figures may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, in different orders, and may be performed alternately or at least partially with respect to other steps or sub-steps of other steps.

It should be understood that the specific embodiments described herein are merely illustrative of the present application and do not limit the scope of the claims herein.

In one embodiment, a control method of a bidirectional power conversion apparatus is provided for controlling the bidirectional power conversion apparatus, and the control method may be performed by the bidirectional power conversion apparatus. The bidirectional power conversion device may be a bidirectional DC/DC conversion device or a bidirectional DC/AC conversion device. The bidirectional power conversion device comprises two current flow directions, and takes the bidirectional DC/DC conversion device as an example, the first side of the bidirectional DC/DC conversion device is connected with a storage battery, and the second side of the bidirectional DC/DC conversion device is connected with a load or a charger. The first side of the bidirectional dc converter is the low voltage side and the second side of the bidirectional dc converter is the high voltage side. The first side of the bidirectional dc conversion device serves as a charging and discharging interface for the bidirectional dc conversion device and the battery. The current flow in the bidirectional dc converter may flow from the first side to the second side, i.e. from the battery to the load, when the battery is discharged. Alternatively, the current in the bidirectional dc converter may flow from the second side to the first side, i.e., from the charger to the battery, to charge the battery.

Referring to fig. 1, a schematic structural diagram of a bidirectional power conversion apparatus 100 provided in an embodiment of the present application is shown, where the bidirectional power conversion apparatus 100 includes:

a push-pull unit 110, a first end of the push-pull unit 110 being connected to an output end of the low-voltage battery as a low-voltage side of the bidirectional power conversion apparatus 100;

a resonance unit 120, wherein the resonance unit 120 comprises a high-frequency isolation transformer and a resonance circuit, and a first end of the resonance unit 120 is connected with a second end of the push-pull unit 110;

a full-bridge unit 130, wherein a first end of the full-bridge unit 130 is connected to a second end of the resonance unit 120, and the second end of the full-bridge unit 130 serves as a high-voltage side of the bidirectional power conversion apparatus 100.

In this embodiment, the low voltage battery may be a 12V lithium battery, and the dc bus voltage of the bidirectional power conversion apparatus 100 may be 400V. The bidirectional power conversion device 100 is controlled by the control unit to realize bidirectional automatic control of charging or discharging the low-voltage battery, and the resonance unit 120 is used to realize electrical isolation between the low-voltage battery and the dc bus voltage. The resonant unit 120 includes a resonant circuit and a high-frequency isolation transformer, a primary side of the high-frequency isolation transformer is connected to the second end of the push-pull unit 110, and a secondary side of the high-frequency isolation transformer is connected to the first end of the full-bridge unit 130 through the resonant circuit. The first switching tube may be connected to the primary side of the transformer and/or to the resonant circuit. When the battery discharges, the transformer performs boost conversion, and energy stored by the storage battery is transmitted to the load to supply power to the load. The high-frequency isolation transformer can separate circuits on both sides of the primary side and the secondary side, so that the safety of the device is improved. The resonant circuit can comprise a resonant inductor Lr and a resonant capacitor Cr, and a resonant signal source can realize zero-voltage switching-on and zero-current switching-off of each switching tube in the bidirectional power conversion device through the resonant inductor Lr, the secondary side of the transformer and the resonant capacitor Cr, so that the voltage stress and the current stress of the switching tubes at the switching-on and switching-off moments are reduced to the minimum.

Optionally, the bidirectional power conversion device includes at least one first switching tube, the first switching tube is disposed between the first side and the second side of the bidirectional power conversion device, and the first switching tube has two operating states of on and off. The driving signal of the first switch tube is changed, so that the first switch tube can be in different working states, and the bidirectional power conversion device can be adjusted to be in different working states. Therefore, the control of the working state of the bidirectional power conversion device can be realized through the control of the first switch tube. Furthermore, the number of the first switching tubes can be more than two, the bidirectional power conversion device can also comprise other switching tubes, and the switching tubes work cooperatively to realize functions of rectification, chopping and the like. In one possible embodiment, the first switch tube may be one power switch tube in the push-pull unit 110 or the full-bridge unit 130.

The control method of the bidirectional power conversion device can be executed by a control unit in the bidirectional power conversion device, such as an MCU, or can be executed by additionally arranging a control unit. The control unit is connected with the first switch tube and can also be connected with other switch tubes in the bidirectional power conversion device and used for sending driving signals to the first switch tube and the other switch tubes to control the first switch tube and the other switch tubes.

In this embodiment, as shown in fig. 2, the control method of the bidirectional power conversion apparatus includes the steps of:

and 102, determining a control output value according to the output parameter of the bidirectional power conversion device.

The output parameter of the bidirectional power conversion device may be an actual output power parameter of the bidirectional power conversion device, such as an output voltage value and/or an output current value. The control unit of the bidirectional power conversion device may acquire an actual output voltage value and/or an actual output current value of the bidirectional power conversion device using the sampling unit. The output parameter of the bidirectional power conversion device may be an output parameter of a resonant circuit or an output parameter of a transformer or an output parameter of a push-pull unit, and is not limited herein as long as the implementation is considered by those skilled in the art.

The output parameter of the bidirectional power conversion device may represent a current operating state of the bidirectional power conversion device, for example, the output parameter of the bidirectional power conversion device may represent a current flow direction of the bidirectional power conversion device, or an operating current, an operating voltage, and the like. The control unit obtains the output parameter of the bidirectional power conversion device, and determines a control output value according to the output parameter of the bidirectional power conversion device, wherein the control output value can be the output value of the control unit. The control unit can control the acquired output parameters of the bidirectional power conversion device by using the voltage ring and/or the current ring, and determines a control output value through a control algorithm of the digital PI regulator.

And 104, adjusting the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube according to the control output value.

After the control output value is obtained, the working state of the bidirectional power conversion device can be determined according to the control output value, and on the basis, the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube are adjusted to control the on-off time and the switching frequency of the first switching tube, so that the working frequency and the gain of the bidirectional power conversion device are adjusted, and the efficiency of the bidirectional power conversion device is further changed.

There are various ways of adjusting the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube according to the control output value. As shown in fig. 3, step 104 may include step 204, or step 206, or step 208.

And 204, controlling the first switching tube to work in a constant-frequency variable-duty-ratio mode in response to the control output value meeting a first preset condition.

And step 206, controlling the first switch tube to work in a fixed-frequency fixed-duty-ratio mode in response to the control output value meeting a second preset condition.

And 208, controlling the first switching tube to work in a variable-frequency constant-duty-ratio mode in response to the control output value meeting a third preset condition.

The constant-frequency variable-duty-ratio mode refers to the condition that the switching frequency of the first switching tube is fixed, and the duty ratio of a driving signal of the first switching tube is changed; the fixed-frequency fixed-duty-ratio mode means that the switching frequency of the first switching tube and the duty ratio of a driving signal of the first switching tube are fixed values; the variable-frequency variable-duty-ratio mode means that the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube are changed. When the control output value meets the first preset condition, the second preset condition or the third preset condition, the frequency of the switching tube of the first switching tube is controlled to be different from the driving signal of the first switching tube, the first switching tube is controlled in a targeted mode according to the actual situation of the control output value, the working state of the bidirectional power conversion device is adjusted in a targeted mode, and therefore the efficiency of the bidirectional power conversion device is improved.

In the control method of the bidirectional power conversion device, when the control output value meets the first preset condition, the second preset condition or the third preset condition, the driving signal of the first switching tube is controlled according to different modes respectively, so that the first switching tube is controlled in a targeted manner according to the actual condition of the control output value. In an optional embodiment, the driving signals of the other switching tubes in the bidirectional power conversion device are also controlled correspondingly, and the driving signals may be consistent with the driving signal of the first switching tube, or may be complementary to the switching states, and have a phase difference of 180 °. In the embodiment, when the input voltage range is wide, the problem of overhigh switching loss caused by changing the gain only in a frequency modulation mode can be avoided, the duty ratio adjustment is added on the basis of frequency modulation of the bidirectional power conversion device, the switching loss of the bidirectional power conversion device can be reduced, and the efficiency and the power density of the bidirectional power conversion device can be improved.

In one embodiment, as shown in fig. 3, before step 104, the method for controlling a bidirectional power conversion apparatus further includes step 103.

And 103, judging the working state of the bidirectional power conversion device according to the control output value.

In this embodiment, the working state includes a discharging state and a charging state, where the discharging state of the bidirectional power conversion device means that the low-voltage battery discharges to a load or a circuit on the high-voltage side through the bidirectional power conversion device, and at this time, the bidirectional power conversion device operates in a boost mode; the bidirectional power conversion device is in a charging state, namely a high-voltage side power supply charges a low-voltage battery, and the bidirectional power conversion device works in a voltage reduction mode at the moment.

In the present embodiment, when the control output value is less than zero, the operating state of the bidirectional power conversion device is considered to be the charge mode, and when the control output value is greater than zero, the operating state of the bidirectional power conversion device is considered to be the discharge mode. The working state of the bidirectional power conversion device is judged according to the control output value, whether the charging mode and the discharging mode need to be switched or not is determined without judging the level of the target voltage, namely whether a switching event occurs or not is determined without logic, time delay caused by interruption of receiving the event and initialization of related variables of a control part is avoided, the response and the time rate of the control method of the bidirectional power conversion device are improved, meanwhile, the switching of the charging and discharging process is smoother, and the overshoot phenomenon in the switching process is avoided.

In this embodiment, before the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube are adjusted, the operating state of the bidirectional power conversion device is determined, and then the operating mode of the first switching tube or other devices can be adjusted according to different operating states of the bidirectional power conversion device, so as to improve the reliability of the control method of the bidirectional power conversion device.

In one embodiment, after step 103, in step 104, when the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube are adjusted, in the discharging state, the switching frequency is greater than or equal to a first switching frequency threshold, and the duty ratio of the driving signal of the first switching tube is less than or equal to 50%. Or, in the charging state, the switching frequency is less than or equal to the third switching frequency threshold, and the duty ratio of the driving signal of the first switching tube is less than or equal to 50%.

In this embodiment, the first switching frequency threshold is a minimum switching frequency value preset in the discharging state, and may be set according to a gain curve of the bidirectional power conversion device. In the discharging state, the switching frequency being greater than or equal to the first switching frequency threshold means that the switching frequency may be equal to or greater than a minimum switching frequency value preset in the discharging state. In the discharge state, the duty ratio of the driving signal of the first switching tube is less than or equal to 50%, which means that the duty ratio of the driving signal of the first switching tube may be 0, or may be any value within 0-50%, but not more than 50% at most.

The third switching frequency threshold is a maximum switching frequency value preset in a charging state, and may be set according to a gain curve of the bidirectional power conversion device. In the charging state, the switching frequency being less than or equal to the third switching frequency threshold means that the switching frequency may be equal to or less than a maximum switching frequency value preset in the charging state. In the charging state, the duty ratio of the driving signal of the first switching tube is less than or equal to 50%, which means that the duty ratio of the driving signal of the first switching tube may be 0, or may be any value within 0-50%, but not more than 50% at most.

In the embodiment, by limiting the switching frequency of the first switching tube within the interval from the first switching frequency threshold to the third switching frequency threshold and limiting the duty ratio of the driving signal of the first switching tube within the interval less than or equal to 50%, zero-voltage on and zero-current off of the power device can be realized, the voltage stress and the current stress of the power device at the time of on and off are reduced to the minimum, and the working efficiency of the bidirectional power conversion device can be improved.

In one embodiment, as shown in fig. 6, the bidirectional power conversion device includes a push-pull unit 110, the push-pull unit 110 includes a first switch tube Q1 and a second switch tube Q2, the switching states of the first switch tube Q1 and the second switch tube Q2 are complementary, and the phase difference between the driving signal of the first switch tube Q1 and the driving signal of the second switch tube Q2 is 180 °, synchronous rectification or chopping can be achieved.

Specifically, the control end of the first switch tube Q1 and the control end of the second switch tube Q2 are both connected to the control unit, the first end of the first switch tube Q1 and the first end of the second switch tube Q2 are both connected to the negative electrode of the battery, and when the bidirectional power conversion device includes the high-frequency isolation transformer, the second end of the first switch tube Q1 and the second end of the second switch tube Q2 are respectively connected to the head end and the tail end of the primary winding of the high-frequency isolation transformer. The control unit adjusts the operating states of the first switching tube Q1 and the second switching tube Q2 by adjusting the driving signals sent to the control end of the first switching tube Q1 and the control end of the second switching tube Q2. The driving signal comprises a high-low level signal, and the first switching tube Q1 and the second switching tube Q2 are in a conducting or a cut-off state when receiving the high level or the low level. The control unit controls the working modes of the first switch tube Q1 and the second switch tube Q2 by adjusting the frequency and/or duty ratio of the driving signal. The bidirectional power conversion device may further include a capacitor C1, two ends of the capacitor C1 are respectively connected to two ends of a first side (low voltage side) of the bidirectional power conversion device, and when the first side of the bidirectional power conversion device is connected to a battery, two ends of the capacitor C1 are respectively connected to a positive electrode and a negative electrode of the battery. The push-pull unit 110 has a simple topology and a small number of switching tubes, and can effectively reduce the loss increase caused by the increase of the current stress of the power device under the conditions of low voltage, high power or large voltage transformation ratio.

Further, the bidirectional power conversion apparatus may further include a resonant circuit and a full-bridge unit 130, the secondary winding of the high-frequency isolation transformer is connected to the resonant circuit, the resonant circuit is connected to the full-bridge unit 130, and the full-bridge unit 130 serves as a second side of the bidirectional power conversion apparatus. The primary winding of the transformer is connected to the push-pull unit 110, and the push-pull unit 110 serves as a first side of the bidirectional power conversion device. When the bidirectional power conversion device is in a discharging state, the push-pull unit 110 is used for chopping the output voltage of the battery, and the full-bridge unit 130 is a high-voltage side rectifying circuit; when the bidirectional power conversion device is in a charging state, the full-bridge unit 130 is used for inverting the high-side direct-current voltage, and the push-pull unit 110 is used for synchronously rectifying the output voltage of the high-frequency isolation transformer. The resonant signal source passes through the resonant inductor Lr, the secondary inductor Lm (winding Lm) of the transformer and the resonant capacitor Cr to realize zero-voltage switching-on and zero-current switching-off of the power device of the conversion circuit, so that the voltage stress and the current stress of the power device at the switching-on and switching-off moments are reduced to the minimum.

As shown in fig. 6, the resonant circuit includes a resonant inductor Lr and a resonant capacitor Cr, and the full-bridge unit 130 includes a switching tube Q3, a switching tube Q4, a switching tube Q5, and a switching tube Q6. The control ends of the switching tube Q3, the switching tube Q4, the switching tube Q5 and the switching tube Q6 are all connected with the control unit and receive driving signals from the control unit. The first end of switch tube Q4 and the first end of switch tube Q6 all connect the second end on the second side of two-way power conversion device, and the first end of switch tube Q3 is connected to the second end of switch tube Q4, and the first end of switch tube Q5 is connected to the second end of switch tube Q6, and the first end on the second side of two-way power conversion device is connected to the second end of switch tube Q3 and the second end of switch tube Q5. The first end of the resonance capacitor Cr is connected with the head end of the secondary winding of the transformer, and the second end of the resonance capacitor Cr is connected with the first end of the switch tube Q3 and the second end of the switch tube Q4. A first end of the resonant inductor Lr is connected to the end of the secondary winding of the transformer, and a second end of the resonant inductor Lr is connected to the first end of the switching transistor Q5 and the second end of the switching transistor Q6. The bidirectional power conversion device may further include a capacitor C2, and two ends of the capacitor C2 are respectively connected to the first end and the second end of the second side of the bidirectional power conversion device.

And a switching tube Q3, a switching tube Q4, a switching tube Q5 and a switching tube Q6 in the rectifier bridge circuit form four full-bridge switching bridge arms, are connected with the high-voltage side voltage HV +, HV-, and carry out synchronous rectification or inversion by controlling the on-off of the switching tube Q3, the switching tube Q4, the switching tube Q5 and the switching tube Q6. The resonant circuit is superimposed on the second, i.e. high voltage side of the bi-directional power conversion device, which may optimize the conversion efficiency.

Taking the example that the first side of the bidirectional power conversion device is connected with the storage battery, in this example, according to the duty ratio of the driving signal of the switching tube being 50%, the operation process of the bidirectional power conversion device is described as follows in combination with the structure of the bidirectional power conversion device:

when the battery is discharged:

the push-pull unit 110 includes switching tubes Q1, Q2, and a low-voltage side power supply chops the dc power to convert the dc power into a rectangular wave through the push-pull unit 110.

The resonant unit 120 includes a resonant circuit and primary windings Ls1 and Ls2 of the transformer, and the resonant circuit includes an inductor Lr, a capacitor Cr and a secondary winding Lm of the transformer. The rectangular wave generated by the push-pull unit 110 is converted into a signal input source of the resonant circuit by the step-up conversion through the transformer. The rectangular wave signal passes through the resonant circuit and then enters the high-voltage-side full-bridge unit 130, and the full-bridge unit 130 serves as a rectifying circuit.

The rectifier bridge circuit comprises switching tubes Q3, Q4, Q5 and Q6, and rectangular wave signals enter the rectifier bridge circuit after passing through the resonance circuit. Q3, Q6 and Q1 of the rectifier bridge circuit keep the same switch logic and are switched on or switched off at the same time. Q4, Q5 and Q2 of the rectifier bridge circuit keep the same switching logic and are switched on or switched off simultaneously. Meanwhile, the switching states of Q3 and Q6 are complementary with the switching states of Q4 and Q5, the phase sequence has a difference of 180 degrees, and synchronous rectification is realized, so that the energy on the low-voltage battery side can be converted into a high-voltage side capacitor C2 through a circuit.

In the battery discharge operation mode, the operation time sequence of each power device is described as follows: the switching timing of the push-pull Q1, Q2 is shown in FIG. 7, and the switching timing of the commutations Q3-Q6 is shown in FIG. 8.

As shown in fig. 9, by controlling the switching time of the switching tube, the on-time of the low-voltage sides Q1 and Q2 can be controlled to be 0V (V) at the drain-source voltage of Q1 and Q2 _ds = 0V), zero voltage turn-on is formed, reducing the turn-on of the low-side switching deviceAnd meanwhile, due to the existence of the resonant circuit, the switching device is turned off when the current flowing through the switching tube is reduced to a very low level at the turn-off moment, so that the turn-off loss of the switching device can be effectively reduced.

As shown in fig. 10, the high-voltage side rectifying bridge arm performs synchronous rectification while Q1 and Q2 are switched, and taking the switching tube Q6 as an example, when the power device is turned off, the drain-source current is reduced to 0A, so that zero-current turn-off is realized, and the turn-off loss of the high-voltage side switching device is reduced. Meanwhile, due to the influence of the resonant circuit, the loss of the power device during the turn-on process can be greatly optimized. Therefore, the control mode is integrated, the whole switching loss of the high-voltage side switching device can be effectively reduced, and the battery discharging efficiency is greatly optimized.

When the battery is charged:

as shown in fig. 6, the energy flow direction during battery charging is from the high-voltage side to the low-voltage side.

The full-bridge unit 130 includes switching transistors Q3, Q4, Q5, and Q6, forming an inverter circuit on the high-voltage side, and the high voltage HV generates a rectangular wave signal after passing through the inverter circuit, and the rectangular wave signal serves as an input signal of the resonant circuit.

The resonance circuit comprises an inductor Lr, a capacitor Cr and a secondary winding Lm of the transformer, rectangular wave signals are resonated after passing through the resonance circuit, and the resonance signals enter the transformer to be converted and enter the push-pull unit 110.

The push-pull unit 110 includes switching tubes Q1 and Q2, which form a synchronous rectification circuit together with primary windings Ls1 and Ls2 of the transformer, rectify the ac signal and output it to a capacitor C1, and charge the battery. Q2 maintains the same switching logic as Q3, Q6, while turning on or off. Q1 maintains the same switching logic as Q4, Q5, and is turned on or off at the same time. Meanwhile, the switching state of the Q1 is complementary with that of the Q2, the phase sequence is different by 180 degrees, and synchronous rectification is realized, so that the energy on the high-voltage side can be converted into a capacitor C1 on the low-voltage side through a circuit, and the battery is charged.

In the above charging operation mode, the operation timing of each power device is described as follows: the switching timing of the inverter bridge Q3-Q6 is shown in FIG. 11, and the switching timing of the push-pull synchronous rectifier bridge Q1, Q2 is shown in FIG. 12. Such asAs shown in fig. 13, the on-time of the high-voltage sides Q3, Q4, Q5, Q6 can be controlled to 0V (V) at the drain-source voltage by controlling the switching time of the switching tubes _ds = 0V), a zero voltage turn-on is formed, reducing the turn-on loss of the high-side switching device, and at the turn-off time, the current flowing through the switching tube turns off the switching device when the current drops to a very low level due to the presence of the resonant circuit, thus effectively reducing the turn-off loss of the switching device.

As shown in fig. 14, the low-voltage side rectifier bridge arm performs synchronous rectification while inverting the bridge arm switch, and when the power devices Q1 and Q2 are turned off, the drain-source current is reduced to 0A, so that zero-current turn-off is realized, and turn-off loss of the high-voltage side switching device is reduced. Meanwhile, due to the influence of the resonant circuit, the loss of the power device during the turn-on process can be greatly optimized.

Therefore, by integrating the control modes, soft switching of the low-voltage side switching device and the high-voltage side switching device can be realized, the overall switching loss of the switching devices is reduced, and the discharging and charging efficiency of the battery is greatly optimized.

In one embodiment, after step 204, as shown in fig. 4, the method for controlling a bidirectional power conversion apparatus further includes steps 304 to 308.

And 304, if the duty ratio of the driving signal of the first switching tube is smaller than the duty ratio critical value, accumulating the duty ratios of the continuously sent driving signals to obtain an accumulated value.

The duty ratio critical value is the minimum duty ratio value which enables the first switch tube to drive. And after the first switching tube is controlled to work in the constant-frequency variable duty ratio mode, acquiring the duty ratio of a driving signal of the first switching tube. If the duty ratio of the driving signal of the first switch tube is smaller than the duty ratio critical value, the duty ratio of the driving signal of the first switch tube is considered to be small at the moment, and the driving signal of the duty ratio cannot drive the first switch tube. At this time, the duty ratios of the continuously emitted driving signals are accumulated to obtain an accumulated value.

And step 306, in response to the accumulated value being greater than or equal to the duty ratio critical value, controlling the duty ratio of the driving signal of the first switching tube to be the accumulated value.

When the accumulated value is larger than or equal to the duty ratio critical value, the accumulated value of the duty ratio can meet the requirement, the first switch tube can be driven, the duty ratio of the driving signal of the first switch tube is controlled to be the accumulated value, and the driving signal with the duty ratio as the accumulated value controls the first switch tube to work.

And step 308, clearing the accumulated value.

After the duty ratio of the driving signal for controlling the first switching tube is an accumulated value and the driving signal with the duty ratio as the accumulated value is used for controlling the first switching tube to work, the accumulated value is cleared, and the influence on subsequent steps is avoided.

Optionally, after step 304, the method for controlling a bidirectional power conversion apparatus further includes step 305.

Step 305, in response to the accumulated value being less than the duty cycle threshold value, return to step 304.

When the accumulated value is smaller than the duty ratio critical value, the accumulated value of the duty ratio at the moment is considered to be still insufficient to drive the first switching tube out. At this time, returning to step 304, continuously accumulating the duty ratios of the continuously emitted driving signals to obtain an accumulated value, and executing step 305 or step 306 according to the accumulated value.

In this embodiment, due to the introduction of the duty ratio modulation mode, the duty ratio is very small when the load is light, the required gain is small, the duty ratio of the output is very small, the time is short, and the output is turned off without reaching the turn-on voltage of the switching tube, so that the switching tube cannot output the drive all the time, and when the drive can output, the duty ratio is large, which causes the voltage to oscillate. Therefore, in the no-load or even light-load mode, a small pulse wave-emitting modulation mode is introduced, namely when the duty ratio generated by wave emission of the control unit is small, a plurality of continuous small duty ratios which cannot emit waves are superposed to reach the critical value of normal output driving, and the condition that the controlled voltage is severely vibrated can be avoided by normal wave emission through the small duty ratios.

In one embodiment, as shown in fig. 5, before step 104, the method for controlling a bidirectional power converter further includes step 403.

In step 403, the control output value is converted to a point value.

And after the control output value is obtained, converting the control output value into a point value according to a preset algorithm, and executing subsequent control steps according to the point value.

Correspondingly, in this embodiment, as shown in fig. 5, step 204 includes step 4041 or step 4042.

Step 4041, in the discharging state, if the point value is greater than or equal to the maximum period count value corresponding to the first switching frequency threshold, controlling the switching frequency of the first switching tube to maintain the first switching frequency threshold, and controlling the duty ratio of the driving signal of the first switching tube to change along with the change of the control output value.

The first switching frequency threshold is a preset minimum switching frequency value in a discharging state. In a discharging state, if the point value converted according to the control output value is greater than or equal to the maximum period count value corresponding to the first switching frequency threshold value, controlling the first switching tube to work in a constant-frequency variable duty ratio mode, specifically: and controlling the switching frequency of the first switching tube to maintain a first switching frequency threshold value, namely a preset minimum switching frequency value in a discharging state, and controlling the duty ratio of a driving signal of the first switching tube to change along with the change of the control output value. It should be noted that the duty cycle of the driving signal of the first switching tube does not exceed 50%.

Alternatively, in step 4042, in the charging state, if the point value is less than or equal to the minimum period count value corresponding to the third switching frequency threshold, the switching frequency of the first switching tube is controlled to maintain the third switching frequency threshold, and the duty ratio of the driving signal of the first switching tube is controlled to change with the change of the control output value.

And the third switching frequency threshold value is a preset maximum switching frequency value in a charging state. In a charging state, if the number of points converted according to the control output value is less than or equal to a minimum period count value corresponding to a third switching frequency threshold, controlling the first switching tube to work in a constant-frequency variable duty ratio mode, specifically: and controlling the switching frequency of the first switching tube to maintain a third switching frequency threshold value, namely a preset maximum switching frequency value in a charging state, and controlling the duty ratio of a driving signal of the first switching tube to change along with the change of the control output value. It should be noted that the duty cycle of the driving signal of the first switching tube does not generally exceed 50%. The duty ratio is gradually adjusted from 0 in the charging and discharging switching process, and the switching process is smooth.

In this embodiment, the control output value satisfying the first preset condition means that the point value converted according to the control output value in the discharging state is greater than or equal to the maximum period count value corresponding to the first switching frequency threshold value, or the point value converted according to the control output value in the charging state is less than or equal to the minimum period count value corresponding to the third switching frequency threshold value, where the first switching frequency threshold value is the minimum switching frequency value preset in the discharging state, and the third switching frequency threshold value is the maximum switching frequency value preset in the charging state. That is to say, when the control output value determined according to the output parameter of the bidirectional power conversion device exceeds the preset switching frequency threshold range, the switching frequency is not adjusted any more, but the switching tube is controlled by adopting a fixed-frequency variable-duty-ratio mode, so that when the input voltage range is wide, the problem of overhigh switching loss caused by changing gain only in a frequency modulation mode is avoided, the duty ratio adjustment is added on the basis of frequency modulation of the bidirectional power conversion device, the switching loss of the bidirectional power conversion device can be reduced, and the efficiency and the power density of the bidirectional power conversion device are improved.

In one embodiment, as shown in FIG. 5, step 206 includes step 4061 or step 4062.

Step 4061, in the discharging state, if the point value is less than or equal to the minimum period count value corresponding to the second switching frequency threshold, controlling the switching frequency of the first switching tube to maintain the second switching frequency threshold, and controlling the duty ratio of the driving signal of the first switching tube to maintain 50%.

The second switching frequency threshold is a maximum switching frequency value preset in a discharging state, and can be set according to a gain curve of the bidirectional power conversion device. In a discharging state, if the point value is less than or equal to a minimum period count value corresponding to the second switching frequency threshold, controlling the first switching tube to work in a fixed-frequency fixed-duty-ratio mode, specifically: and controlling the switching frequency of the first switching tube to maintain a second switching frequency threshold value, namely maintaining a preset maximum switching frequency value in a discharging state, and controlling the duty ratio of a driving signal of the first switching tube to maintain 50%.

Or, in step 4062, in the charging state, if the point value is greater than or equal to the maximum cycle count value corresponding to the fourth switching frequency threshold, the switching frequency of the first switching tube is controlled to maintain the fourth switching frequency threshold, and the duty ratio of the driving signal of the first switching tube is controlled to maintain 50%.

The fourth switching frequency threshold is a minimum switching frequency value preset in a charging state, and may be set according to a gain curve of the bidirectional power conversion device. In a charging state, if the point value is greater than or equal to the maximum period count value corresponding to the fourth switching frequency threshold, controlling the first switching tube to operate in the fixed-frequency fixed-duty mode may specifically be: and controlling the switching frequency of the first switching tube to maintain a fourth switching frequency threshold value, namely maintaining a preset minimum switching frequency value in a charging state, and controlling the duty ratio of a driving signal of the first switching tube to maintain 50%.

In this embodiment, the control output value meeting the second preset condition means that the point value converted according to the control output value in the discharging state is less than or equal to the minimum cycle count value corresponding to the second switching frequency threshold value, or the point value converted according to the control output value in the charging state is greater than or equal to the maximum cycle count value corresponding to the fourth switching frequency threshold value, where the second switching frequency threshold value is the maximum switching frequency value preset in the discharging state, and the fourth switching frequency threshold value is the minimum switching frequency value preset in the charging state. That is, when the control output value determined according to the output parameter of the bidirectional power conversion device is near the resonance point of the bidirectional power conversion device, the switching tube is controlled by adopting a fixed-frequency fixed-duty-ratio mode, so that the output voltage meets the voltage stabilization requirement.

In one embodiment, as shown in FIG. 5, step 208 includes step 4081 or step 4082.

Step 4081, in the discharging state, if the point value is smaller than the maximum period count value corresponding to the first switching frequency threshold and larger than the minimum period count value corresponding to the second switching frequency threshold, controlling the switching frequency of the first switching tube to change along with the change of the control output value, and controlling the duty ratio of the driving signal of the first switching tube to maintain 50%.

In the discharge state, if the number of points converted according to the control output value is smaller than the maximum period count value corresponding to the first switching frequency threshold and larger than the minimum period count value corresponding to the second switching frequency threshold, the first switching tube is controlled to work in the variable-frequency constant-duty-ratio mode, specifically: the switching frequency of the first switching tube is controlled to change along with the change of the control output value, and the duty ratio of the driving signal of the first switching tube is controlled to maintain 50%.

Or, in step 4082, in the charging state, if the point value is greater than the minimum period count value corresponding to the third switching frequency threshold and less than the maximum period count value corresponding to the fourth switching frequency threshold, the switching frequency of the first switching tube is controlled to change with the change of the control output value, and the duty ratio of the driving signal of the first switching tube is controlled to maintain 50%.

In a charging state, if the converted point value according to the control output value is greater than a minimum period count value corresponding to a third switching frequency threshold and less than a maximum period count value corresponding to a fourth switching frequency threshold, controlling the first switching tube to work in a variable-frequency constant duty cycle mode, specifically: the switching frequency of the first switching tube is controlled to change along with the change of the control output value, and the duty ratio of the driving signal of the first switching tube is controlled to maintain 50%.

In this embodiment, the control output value satisfying the third preset condition means that the point value converted according to the control output value in the discharging state is smaller than the maximum period count value corresponding to the first switching frequency threshold and larger than the minimum period count value corresponding to the second switching frequency threshold, or the point value converted according to the control output value in the charging state is larger than the minimum period count value corresponding to the third switching frequency threshold and smaller than the maximum period count value corresponding to the fourth switching frequency threshold. That is, when the control output value determined according to the output parameter of the bidirectional power conversion device is within the threshold range of the switching frequency, the switching tube is controlled by adopting a variable-frequency constant duty ratio mode, wherein the duty ratio is constant at 50%, and the switching frequency changes along with the change of the control output value. Thus, in the present embodiment, the switching loss of the bidirectional power converter can be reduced, and the efficiency and power density of the bidirectional power converter can be improved.

In the specific process of adjusting the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube according to the control output value, after the control output value is converted into the point value, the switching frequency of the first switching tube and the duty ratio of the driving signal are adjusted according to the size relationship between the point value and the cycle count values corresponding to the first switching frequency threshold, the second switching frequency threshold, the third switching frequency threshold and the first switching frequency threshold in combination with different charging or discharging states of the bidirectional power conversion device, the switching process is smooth, the control effect is good, the switching loss of the switching tube is low, and the efficiency and the power density of the bidirectional power conversion device can be remarkably improved. It can be understood that the switching tubes included in the bidirectional power conversion device may be regarded as the first switching tube, and the control method of the bidirectional power conversion device according to the present application may control each switching tube in the bidirectional power conversion device.

In one embodiment, step 403 includes step 503:

step 503, determining a point value according to the control output value, the coefficient ratio between the frequency control and the duty ratio control and the counting point corresponding to the interrupt period.

It is to be understood that the manner of converting the control output value into the dot value is not exclusive, and in the present embodiment, the dot value is determined based on the control output value, the coefficient ratio between the frequency control and the duty control, and the count point corresponding to the interrupt period. Further, when the bidirectional power conversion device is in a charging state or a discharging state, the manner of determining the point value according to the control output value, the coefficient ratio between the frequency control and the duty control, and the count point corresponding to the interrupt period is also different. The point value is determined according to equation (1) when the bidirectional power conversion device is in a discharging state, and the point value is determined according to equation (2) when the bidirectional power conversion device is in a charging state:

（1）

（2）

wherein the content of the first and second substances,Cntin the form of a point value, the value of the point,k1、k2respectively representing the coefficient ratio between the frequency control and the duty ratio control in the discharging mode and the charging mode,D_Outin order to control the output value of the motor,PRDsis the counting point corresponding to the interrupt period. According to the formula, the point value corresponding to the control output value when the bidirectional power conversion device is in a charging or discharging state can be calculated, so that subsequent preset condition judgment can be conveniently carried out according to the point value.

For a better understanding of the above embodiments, the following detailed description is given in conjunction with a specific embodiment. In one embodiment, a control method of a bidirectional power conversion apparatus is used to control the bidirectional power conversion apparatus. As shown in fig. 6, the bidirectional power conversion apparatus includes a push-pull unit 110 on a low-voltage battery side, a transformer, a resonant circuit, which is an LLC circuit, and a full-bridge unit 130 on a high-voltage side, where the resonant circuit includes a resonant inductor Lr and a resonant capacitor Cr. The push-pull unit 110 includes switching tubes Q1, Q2, and input terminals LV +, LV-of the bidirectional power conversion device are respectively connected to the positive electrode and the negative electrode of the storage battery, and are used as electrical interfaces for charging and discharging the bidirectional power conversion device and the storage battery, and synchronous rectification or chopping is performed by controlling on and off of Q1 and Q2. The primary component of the transformer includes winding 1 (i.e., ls 1) and winding 2 (i.e., ls 2), and the secondary component of the transformer includes secondary inductance Lm (i.e., winding Lm).

The full-bridge unit 130 on the high-voltage side adopts a full-bridge structure, in order to optimize conversion efficiency, an LLC circuit structure is superposed on the high-voltage side, power devices Q3, Q4, Q5 and Q6 in a rectifier bridge form four full-bridge switch bridge arms and are connected with the high-voltage side voltage HV +, HV-, and synchronous rectification or chopping is carried out by controlling the connection and disconnection of the power devices Q3, Q4, Q5 and Q6. The resonant signal source can realize zero voltage switching-on and zero current switching-off of the power device of the conversion circuit through the resonant inductor Lr and the resonant capacitor Cr, and the voltage stress and the current stress of the power device at the switching-on and switching-off moments are reduced to the minimum.

When the battery is discharged, the low-voltage side power supply chops through the push-pull unit 110, converts direct current into rectangular waves, performs boost conversion through the transformer, and converts the rectangular waves into a signal input source of the resonant circuit. After passing through the resonant circuit, the rectangular wave signal enters the full-bridge unit 130 on the high-voltage side. Q3, Q6 and Q1 of the full bridge unit 130 maintain the same switching logic and are turned on or off at the same time, and Q4, Q5 and Q2 of the rectifier maintain the same switching logic and are turned on or off at the same time. Meanwhile, the switching states of Q3 and Q6 are complementary with the switching states of Q4 and Q5, the phase sequence has a difference of 180 degrees, synchronous rectification is realized, and the energy on the low-voltage battery side can be converted into a high-voltage side capacitor C2 through a circuit.

In the battery discharge operation mode, the operation time sequence of each power device is described as follows: the push-pull Q1, Q2 switching timing is shown in fig. 7, and the commutation Q3, Q4 switching timing is shown in fig. 8. As shown in fig. 9, by controlling the switching time of the switching tube, the on-time of the low-voltage side Q1 and Q2 can be controlled to 2, so as to form zero-voltage on-state, thereby reducing the on-loss of the low-voltage side switching device.

As shown in fig. 10, the high-voltage side rectifier bridge arm performs synchronous rectification while Q1 and Q2 are switched, and when the power device is turned off, the drain-source current is reduced to 0A, so that 0-current turn-off is realized, and turn-off loss of the high-voltage side switching device is reduced. Meanwhile, due to the influence of the resonant circuit, the loss of the power device during the turn-on process can be greatly optimized, so that the discharge efficiency of the battery can be greatly optimized.

When the battery is charged, the rectifier bridge circuit is used as an inverter circuit, and the high voltage HV generates a rectangular wave signal after passing through the inverter circuit, and the signal is used as an input signal of the resonance circuit. The rectangular wave signal resonates after passing through the resonant circuit, and the resonant signal enters the transformer and is converted and enters the push-pull unit 110. The push-pull unit 110 rectifies the ac signal and outputs the rectified ac signal to the capacitor C1, and charges the battery. Wherein, Q2 and Q3, Q6 keep the same switch logic, turn on or turn off at the same time. Q1 maintains the same switching logic as Q4, Q5, and is turned on or off at the same time. The switching state of the Q1 is complementary with the switching state of the Q2, the phase sequence is different by 180 degrees, and synchronous rectification is realized. Thus, the energy of the high-voltage side can be converted into the low-voltage side capacitor C1 through the circuit, and the battery is charged.

In the above charging operation mode, the operation timing sequence of each power device is described as follows:

the switching timing of the switching tubes Q3/Q6, Q4/Q5 is shown in FIG. 11, and the switching timing of Q1, Q2 is shown in FIG. 12. As shown in fig. 13, by controlling the switching time of the switching tubes, the turn-on time of the high-voltage side Q3, Q4, Q5, Q6 can be controlled at the time when the drain-source voltage is 0V (Vds = 0V), so as to form zero-voltage turn-on, thereby reducing the turn-on loss of the high-voltage side switching device.

As shown in fig. 14, the rectifying bridge arm in the low-voltage side push-pull unit 110 performs synchronous rectification while the bridge arm of the inverter circuit is switched, and when the power devices Q1 and Q2 are turned off, the drain-source current is reduced to 0A, so that 0-current turn-off is realized, and the turn-off loss of the high-voltage side switching device is reduced. Meanwhile, due to the influence of the resonant circuit, the loss of the power device during the turn-on process can be greatly optimized, so that the battery charging efficiency is greatly optimized.

The control method of the bidirectional power conversion device is characterized in that duty ratio adjustment is added on the basis of frequency modulation, the duty ratio adjustment is firstly carried out under the limiting frequency, namely under the condition that the gain is minimum, and the frequency modulation is carried out when the duty ratio reaches 50% under the condition that dead zones are ignored. And the charging and discharging mode switching is not judged by the event management part through logic any more, but is controlled through controlling the output value (D _ Out). Referring to fig. 15, the control unit obtains a control flow chart of the control output value, the control unit obtains output parameters of the bidirectional power conversion device, including reference voltage, real-time voltage, reference current, real-time current and the like, a voltage controller in the control unit outputs the reference current according to the reference voltage and the real-time voltage, and a current controller in the control unit outputs the control output value according to the reference current and the real-time current. When the control output value is less than zero, the charging mode is considered, and when the control output value is more than zero, the discharging mode is considered, and the charging and discharging switching process is gradually adjusted by the duty ratio of 0, so that the switching process is smooth.

The control method of the bidirectional power conversion device mainly comprises four steps from sampling to wave sending: firstly, a control unit acquires output variables related to driving through controlling voltage and current; secondly, the variable is used as modulation input, and the frequency and the duty ratio corresponding to each switching tube are output through a control method of a bidirectional power conversion device; thirdly, providing a corresponding solution to the problem of voltage oscillation introduced by the new modulation method; and fourthly, sending the driving signal acquired by the new modulation method into the resonant circuit to enable the resonant circuit to work normally.

Fig. 16 is a flowchart of a control method of the bidirectional power conversion apparatus, in which prdcdischgmax is a TBPRD value of an EPWM module-related register corresponding to a lower frequency limit value in a discharging mode, PRDchgmin is a TBPRD value of an EPWM module-related register corresponding to an upper frequency limit value in the discharging mode, PRDchgmax is a TBPRD value of an EPWM module-related register corresponding to a lower frequency limit value in a charging mode, PRDchgmin is a TBPRD value of an EPWM module-related register corresponding to an upper frequency limit value in the charging mode, PRD and CMPA are a period value and a comparison value respectively sent to the EPWM module register, cnt is a point value, k1 and k2 represent a coefficient ratio between frequency control and duty control, D _ Out is a control output value, and PRDs is a count point corresponding to an interrupt period. The specific steps of the control method of the bidirectional power conversion device are described in the following text:

step 1: judging whether the resonant circuit works in a charging mode or a discharging mode according to the positive and negative of the control output value of the control unit, if the resonant circuit works in the discharging mode, entering the step 2, and if the resonant circuit does not work in the discharging mode, entering the step 8;

step 2: after converting the control output value into corresponding points, entering step 3;

and step 3: if the point value calculated in the step 2 is larger than the limited maximum period count value, the step 4 is carried out, otherwise, the step 5 is carried out;

and 4, step 4: at the moment, the discharge mode works under the condition of constant frequency and variable duty ratio, the frequency is the lowest frequency in the discharge mode, and the duty ratio is changed along with the output value of the controller;

and 5: if the point value calculated by the step 2 is smaller than the limited minimum period count value, entering a step 6, otherwise, entering a step 7;

and 6: at the moment, the constant-frequency constant-duty ratio switching tube performs wave generation;

and 7: at the moment, under the condition that the discharge mode works at variable frequency and constant duty ratio, the frequency changes along with the output value of the controller, and the duty ratio is constant and is 50 percent;

and 8: after converting the output value of the controller into the number of points corresponding to the interrupt period, entering step 9;

and step 9: if the point value calculated in the step 8 is smaller than the limited minimum cycle count value, the step 10 is switched, otherwise, the step 11 is switched;

step 10: at the moment, the charging mode works under the condition of constant frequency and variable duty ratio, the frequency is the highest frequency in the charging mode, and the duty ratio changes along with the output value of the controller;

step 11: if the point value calculated through the step 2 is larger than the limited maximum period count value, the step 12 is entered, otherwise, the step 13 is entered;

step 12: at the moment, the constant-frequency constant-duty ratio switching tube in the charging mode performs wave generation;

step 13: at this time, the charging mode is operated under the condition of variable frequency and constant duty ratio, the frequency is changed along with the change of the control output value, and the duty ratio is constant at 50%.

In addition, in a no-load or even light-load mode, the required gain is small, the duty ratio of output is very small, the time is short, and the output is turned off without reaching the turn-on voltage, so that the switching tube cannot output drive all the time, and when the drive can output, the duty ratio is large, so that the voltage is oscillated. Therefore, under the no-load or even light-load mode, a small pulse wave-emitting modulation mode is introduced. When the duty ratio generated by wave emission of the controller is smaller, the continuous small duty ratios which cannot emit waves are superposed to reach the critical value of normal output driving, and the condition that the controlled voltage is severely vibrated can be avoided by normal wave emission through the small duty ratios.

In this embodiment, in order to avoid the voltage or current oscillation, the discharging mode and the charging mode are respectively added with small pulse modulation after step 4 and step 10, step 4 includes step 4-1 to step 4-3, and step 10 includes step 10-1 to step 10-3. The flow chart of the small pulse modulation in the charging mode and the flow chart of the small pulse modulation in the discharging mode are both shown in fig. 17, in the diagrams, PRD and CMPA are respectively a period value and a comparison value which are sent to an EPWM module register, cntminlim is a count value corresponding to a critical value which can be driven by a switching tube, and CMPATemp is an accumulated value. The flow of the small pulse modulation is described by characters and specifically operated as follows:

step 4-1: when the obtained duty ratio is smaller than a critical value that the switching tube can drive, turning to the step 4-2, otherwise, turning to the step 4-3;

step 4-2: accumulating the small duty ratio, assigning the small duty ratio to a comparison register of the EPWM module, resetting the accumulated value if the accumulated value is larger than a critical value of driving of a switching tube, and otherwise keeping the accumulated value unchanged;

step 4-3: and clearing the accumulated value.

Step 10-1: when the duty ratio obtained by control is smaller than a critical value that the switching tube can drive, switching to a step 10-2, otherwise, switching to a step 10-3;

step 10-2: accumulating the small duty ratio, assigning the small duty ratio to a comparison register of the EPWM module, resetting the accumulated value if the accumulated value is larger than a critical value of driving of a switching tube, and otherwise keeping the accumulated value unchanged;

step 10-3: and clearing the accumulated value.

Referring to fig. 18, a simulation diagram of generating the driving signal of the switching tube in the embodiment of the bidirectional power converter shown in fig. 6 is shown. Wherein Output represents the controller Output value and Cnt is the dot value. hchg (Output, cnt) represents a transfer function for converting the controller Output value into a point value with the interrupt cycle as a reference in the charge mode, f1 (Output, cnt, f _ charge), f2 (Output, cnt, f _ charge), and f3 (Output, cnt, f _ charge) represent transfer functions for obtaining frequencies when the Cnt value is in different limit value interval ranges in the charge mode, respectively, and g1 (Output, cnt, D _ charge), g2 (Output, cnt, D _ charge), and g3 (Output, cnt, D _ charge) represent transfer functions for obtaining duty ratios when the Cnt value is in different limit value interval ranges in the charge mode, respectively; hdischg (Output, cnt) represents a transfer function for converting a controller Output value into a number of points with an interrupt cycle as a reference in the discharging mode, f4 (Output, cnt, f _ charge), f5 (Output, cnt, f _ charge), and f6 (Output, cnt, f _ charge) represent transfer functions for obtaining a frequency when a Cnt value is in a different limit value interval range in the discharging mode, respectively, and g4 (Output, cnt, D _ charge), g5 (Output, cnt, D _ charge), and g6 (Output, cnt, D _ charge) represent transfer functions for obtaining a duty ratio when a Cnt value is in a different limit value interval range in the discharging mode, respectively; p1 (D1) and p2 (D1) respectively indicate transfer functions with respect to duty ratios in the charge mode or the discharge mode when the Cnt value is equal to or smaller than Cntminlim, which is a count value corresponding to a threshold value at which the switching tube can be driven.

In the following formula, PRDchgmax is the TBPRD value of the EPWM module related register corresponding to the lower frequency limit value in the charging mode, and PRDchgmin is the TBPRD value of the EPWM module related register corresponding to the upper frequency limit value in the charging mode; PRDdischgmax is the TBPRD value of the relevant register of the EPWM module corresponding to the lower frequency limit value in the discharge mode, PRDdischgmin is the TBPRD value of the relevant register of the EPWM module corresponding to the upper frequency limit value in the discharge mode, and TBPRD is the value of the time-base period register. In the formula f _Charge Representing the value of the switching frequency in the charging mode, D _Charge Indicating chargingDuty ratio in mode, D _ChgNarrow Indicating the duty cycle under small pulse modulation. f. of _DisCharge Representing the value of the switching frequency in discharge mode, D _DisCharge Denotes the duty ratio in discharge mode, D _DisChgNarrow Indicating the duty cycle under small pulse modulation.

As shown in fig. 18, in the charging mode, the frequency modulation of the charging mode is based on:

the duty ratio regulation basis of the charging mode is as follows:

the charging mode small pulse wave-emitting modulation basis is as follows:

in the discharging mode, the discharging mode frequency modulation is based on:

the duty ratio of the discharge mode is adjusted according to the following steps:

the discharge mode small pulse wave-emitting modulation basis is as follows:

according to the control method of the bidirectional power conversion device, duty ratio adjustment is added on the basis of frequency modulation, the duty ratio adjustment is firstly carried out under the condition of the limit frequency, namely the gain is the minimum, and the frequency modulation is carried out when the duty ratio reaches 50% under the condition of neglecting dead zones. And the charge-discharge mode switching is not judged by the event management part through logic any more, but is controlled through controlling the output value. When the control output value is less than zero, the charging mode is considered, and when the control output value is greater than zero, the discharging mode is considered, the duty ratio is gradually adjusted to be 0 in the charging and discharging switching process, and the switching process is smooth. Under the no-load or even light-load mode, a small pulse wave-emitting modulation mode is introduced. When the duty ratio generated by wave emission of the control unit is smaller, the continuous small duty ratios which cannot emit waves are superposed to reach the critical value of normal output driving, and the condition that the controlled voltage is severely vibrated can be avoided by normal wave emission through the small duty ratios.

Based on the same inventive concept, the embodiment of the present application further provides a control device of a bidirectional power conversion device for implementing the control method of the bidirectional power conversion device. The implementation scheme for solving the problem provided by the apparatus is similar to the implementation scheme described in the above method, so specific limitations in the following embodiments of one or more control apparatuses for a bidirectional power conversion apparatus may refer to the limitations on the control method for the bidirectional power conversion apparatus, and are not described herein again.

In one embodiment, a control device for a bidirectional power conversion device is provided, and the bidirectional power conversion device comprises at least one first switch tube. The control device of the bidirectional power conversion device comprises a control output value acquisition module and a switch tube control module, wherein:

and the control output value acquisition module is used for determining a control output value according to the output parameter of the control device.

The switching tube control module is used for adjusting the switching frequency of the first switching tube and the duty ratio of a driving signal of the first switching tube according to the control output value; wherein, include: controlling a first switching tube to work in a constant-frequency variable duty ratio mode in response to the control output value meeting a first preset condition; or, in response to the control output value meeting a second preset condition, controlling the first switching tube to work in a fixed-frequency fixed-duty-ratio mode; or, in response to the control output value meeting a third preset condition, controlling the first switching tube to work in a variable-frequency constant-duty-ratio mode.

In one embodiment, the control device of the bidirectional power conversion device further includes a working state obtaining module, where the working state obtaining module is configured to determine a working state of the bidirectional power conversion device according to the control output value before the switch control module adjusts the switching frequency of the first switch tube and the duty ratio of the driving signal of the first switch tube according to the control output value, and the working state includes a discharging state and a charging state.

In one embodiment, the control device of the bidirectional power conversion device further includes a duty ratio accumulation module, where the duty ratio accumulation module is configured to, after the switch tube control module controls the first switch tube to operate in the fixed-frequency variable duty ratio mode in response to the control output value satisfying a first preset condition, accumulate duty ratios of the continuously-transmitted driving signals if the duty ratio of the driving signal of the first switch tube is smaller than a duty ratio critical value, so as to obtain an accumulated value; controlling the duty ratio of a driving signal of the first switching tube to be the accumulated value in response to the accumulated value being larger than or equal to the duty ratio critical value; clearing the accumulated value; the duty ratio critical value is the minimum duty ratio value which enables the first switch tube to drive.

The respective modules in the control device of the bidirectional power conversion device may be wholly or partially implemented by software, hardware, and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.

In one embodiment, a bidirectional power conversion apparatus is provided, which includes a control unit and at least one first switch tube, wherein the control unit is configured to perform the steps in the above-mentioned method embodiments.

The bidirectional power conversion device comprises at least one first switching tube, a control output value is determined according to an output parameter of the bidirectional power conversion device, the switching frequency of the first switching tube and the duty ratio of a driving signal of the first switching tube are adjusted according to the control output value, and the first switching tube is controlled to work in a constant-frequency variable-duty-ratio mode in response to the control output value meeting a first preset condition; or, in response to the control output value meeting a second preset condition, controlling the first switching tube to work in a fixed-frequency fixed-duty-ratio mode; or, in response to the control output value meeting a third preset condition, controlling the first switching tube to work in a variable-frequency constant-duty-ratio mode. The duty ratio adjustment is added on the basis of the frequency modulation of the bidirectional power conversion device, so that the switching loss of the bidirectional power conversion device can be reduced, the stability, the efficiency and the power density of the output voltage of the bidirectional power conversion device are improved, and the use is reliable.

In one embodiment, a computer device is further provided, which includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method embodiments when executing the computer program.

In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method embodiments.

The above-mentioned serial numbers of the embodiments of the present application are merely for description and do not represent the merits of the embodiments.

In the present application, the same or similar term concepts, technical solutions and/or application scenario descriptions will be generally described only in detail at the first occurrence, and when the description is repeated later, the detailed description will not be repeated in general for brevity, and when understanding the technical solutions and the like of the present application, reference may be made to the related detailed description before the description for the same or similar term concepts, technical solutions and/or application scenario descriptions and the like which are not described in detail later.

In the present application, each embodiment is described with emphasis, and reference may be made to the description of other embodiments for parts that are not described or illustrated in any embodiment.

The technical features of the technical solution of the present application may be arbitrarily combined, and for brevity of description, all possible combinations of the technical features in the embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, the scope of the present application should be considered as being described in the present application.

Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solution of the present application or portions thereof contributing to the prior art may be embodied in the form of a software product, which is stored in a storage medium (e.g. ROM/RAM, magnetic disk, optical disk) as above and includes several instructions for enabling a terminal device (which may be a power electronic device or an electric device, etc.) to execute the method of each embodiment of the present application.

The above description is only a preferred embodiment of the present application, and not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application, or which are directly or indirectly applied to other related technical fields, are included in the scope of the present application.

Claims

1. A control method of a bidirectional power conversion device, wherein the bidirectional power conversion device comprises at least one first switch tube, the control method comprises:

determining a control output value according to the output parameter of the bidirectional power conversion device;

responding to the control output value meeting a first preset condition, and controlling the first switching tube to work in a constant-frequency variable-duty ratio mode, wherein the first preset condition is that the first switching tube exceeds a preset switching frequency threshold range; alternatively, the first and second electrodes may be,

controlling the first switching tube to work in a fixed-frequency fixed-duty-ratio mode in response to the control output value meeting a second preset condition, wherein the second preset condition is that the first switching tube is positioned near a resonance point of the bidirectional power conversion device; alternatively, the first and second liquid crystal display panels may be,

and responding to a third preset condition that the control output value meets the third preset condition, and controlling the first switching tube to work in a variable-frequency constant duty ratio mode, wherein the third preset condition is that the first switching tube is within a switching frequency threshold range.

2. The control method according to claim 1, wherein before adjusting the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube according to the control output value, the method further comprises:

judging the working state of the bidirectional power conversion device according to the control output value; the operating state includes a discharging state and a charging state.

3. The control method according to claim 2,

in a discharging state, the switching frequency is greater than or equal to a first switching frequency threshold, and the duty ratio of a driving signal of the first switching tube is less than or equal to 50%; alternatively, the first and second electrodes may be,

in a charging state, the switching frequency is less than or equal to a third switching frequency threshold, and the duty ratio of a driving signal of the first switching tube is less than or equal to 50%.

4. The control method according to any one of claims 1 to 3, wherein the controlling the first switching tube to operate in the fixed-frequency variable duty cycle mode in response to the control output value satisfying a first preset condition further comprises:

if the duty ratio of the driving signal of the first switching tube is smaller than a duty ratio critical value, accumulating the duty ratios of the continuously sent driving signals to obtain an accumulated value;

in response to the accumulated value being larger than or equal to the duty ratio critical value, controlling the duty ratio of the driving signal of the first switching tube to be the accumulated value;

clearing the accumulated value; the duty ratio critical value is a minimum duty ratio value which enables the first switch tube to be driven.

5. The control method according to claim 4, characterized by further comprising:

and returning to the step of accumulating the duty ratios of the continuously emitted driving signals in response to the accumulated value being smaller than the duty ratio critical value.

6. The control method according to claim 3, wherein before adjusting the switching frequency of the first switching tube and the duty ratio of the driving signal of the first switching tube according to the control output value, the method further comprises:

converting the control output value into a point value;

the responding to the control output value meeting a first preset condition, the control of the first switch tube to work in a constant-frequency variable-duty-cycle mode comprises the following steps:

in a discharging state, if the point value is greater than or equal to a maximum period counting value corresponding to the first switching frequency threshold value, controlling the switching frequency of the first switching tube to maintain the first switching frequency threshold value, and controlling the duty ratio of a driving signal of the first switching tube to change along with the change of the control output value; the first switching frequency threshold value is a preset minimum switching frequency value in a discharging state;

alternatively, the first and second liquid crystal display panels may be,

in a charging state, if the point value is less than or equal to a minimum period count value corresponding to the third switching frequency threshold, controlling the switching frequency of the first switching tube to maintain the third switching frequency threshold, and controlling the duty ratio of the driving signal of the first switching tube to change along with the change of the control output value; the third switching frequency threshold value is a preset maximum switching frequency value in a charging state;

the converting the control output value to a point value includes:

and determining the point numerical value according to the control output value, the coefficient ratio between the frequency control and the duty ratio control and the counting point corresponding to the interrupt period.

7. The control method according to claim 6, wherein the controlling the first switching tube to operate in the fixed-frequency fixed-duty-cycle mode in response to the control output value satisfying a second preset condition comprises:

in a discharging state, if the point value is less than or equal to a minimum period count value corresponding to a second switching frequency threshold, controlling the switching frequency of the first switching tube to maintain the second switching frequency threshold, and controlling the duty ratio of a driving signal of the first switching tube to maintain 50%; the second switching frequency threshold is a preset maximum switching frequency value in a discharging state;

alternatively, the first and second electrodes may be,

in a charging state, if the point value is greater than or equal to a maximum period count value corresponding to a fourth switching frequency threshold, controlling the switching frequency of the first switching tube to maintain the fourth switching frequency threshold, and controlling the duty ratio of a driving signal of the first switching tube to maintain 50%; and the fourth switching frequency threshold is a preset minimum switching frequency value in a charging state.

8. The control method according to claim 7, wherein the controlling the first switching tube to operate in a variable-frequency constant-duty-cycle mode in response to the control output value satisfying a third preset condition comprises:

in a discharging state, if the point value is smaller than a maximum period count value corresponding to a first switching frequency threshold value and larger than a minimum period count value corresponding to a second switching frequency threshold value, controlling the switching frequency of the first switching tube to change along with the change of the control output value, and controlling the duty ratio of a driving signal of the first switching tube to maintain 50%;

alternatively, the first and second liquid crystal display panels may be,

in a charging state, if the point value is greater than a minimum period count value corresponding to the third switching frequency threshold and less than a maximum period count value corresponding to the fourth switching frequency threshold, the switching frequency of the first switching tube is controlled to change along with the change of the control output value, and the duty ratio of a driving signal of the first switching tube is controlled to maintain 50%.

9. A bidirectional power converter, comprising at least one first switching transistor and a control unit, wherein the control unit is configured to execute the control method according to any one of claims 1 to 8.