Control system and method for smooth switching of cascaded isolation converter

Abstract

The invention relates to a control system and method for smooth switching of a cascaded isolation converter, the system comprises a first-stage circuit and a second-stage circuit, the first-stage circuit and the second-stage circuit are in cascade connection, the first-stage circuit comprises a four-switch converter, the second-stage circuit is a half-bridge LLC converter, and the first-stage circuit is connected with the second-stage circuit. The half-bridge LLC converter comprises a fifth switch, a sixth switch, a seventh switch, an eighth switch, a transformer, a resonant capacitor, a resonant inductor and an output capacitor. By controlling the duty ratios of the eight switches in the control system, different control strategies can be respectively adopted according to different front-end input voltages on the premise of considering efficiency, other working modes can be smoothly switched when the voltages change in a large range, isolation of input and output ends is realized, and rear-end electric equipment is protected.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a control system and method with smooth switching of a cascaded isolation converter. Background Art

[0002] With the rapid development of power electronics technology, in the field of medium and high power DC, applications such as aviation power supply, communication power supply, server power supply, electric vehicle charging and lighting power supply have put forward higher requirements on the output steady state, dynamic response and efficiency of the converter.

[0003] For most converters, the front end of the converter is connected to a high-voltage power battery pack. The power and voltage of the high-voltage power battery pack will decrease significantly with use, so the converter needs to meet a wide voltage input; secondly, to ensure the safety of electricity use in high-voltage input application scenarios, the main power circuit of the module power supply in this application often uses an isolated topology. This structure can achieve electrical isolation between input and output, thereby protecting the load and user equipment. Therefore, how to achieve smooth switching of isolated converters in different working modes while meeting wide voltage input and voltage changes has become one of the urgent problems to be solved. Summary of the invention

[0004] In view of this, the present application proposes a control system for smooth switching of cascaded isolation converters to solve the problems embodied in the above-mentioned background technology.

[0005] According to one aspect of the present application, a control system for smooth switching of a cascade-type isolation converter is provided, comprising: a first-stage circuit and a second-stage circuit, wherein the first-stage circuit and the second-stage circuit are connected in cascade;

[0006] The first-stage circuit includes a four-switch converter, which includes: a first switch, a second switch, a third switch, a fourth switch, and a filter inductor, wherein the first switch and the second switch constitute a front bridge arm, and the third switch and the fourth switch constitute a rear bridge arm, wherein one end of the filter inductor is connected to the midpoint of the bridge arm of the front bridge arm, and the other end of the filter inductor is connected to the midpoint of the bridge arm of the rear bridge arm;

[0007] The second-stage circuit is a half-bridge LLC converter, which includes a fifth switch, a sixth switch, a seventh switch, an eighth switch, a transformer, a resonant capacitor, a resonant inductor, and an output capacitor, wherein the resonant inductor is connected in series with the resonant capacitor and is connected to one end of the transformer and both ends of the sixth switch, and the seventh switch and the eighth switch are connected in series to the other end of the transformer and in parallel with the output capacitor.

[0008] As an optional implementation scheme of the present application, the duty cycles of the first switch and the second switch are complementary;

[0009] The duty cycles of the third switch and the fourth switch are complementary;

[0010] The duty cycles of the fifth switch and the sixth switch are complementary;

[0011] The duty cycles of the seventh switch and the eighth switch are complementary.

[0012] As an optional implementation scheme of the present application, the first stage circuit further includes: an input capacitor and a bus capacitor;

[0013] The input capacitor is connected in parallel with the high-voltage power battery at the front input end of the control system and the front bridge arm;

[0014] The bus capacitor is connected in parallel with the rear bridge arm.

[0015] As an optional implementation scheme of the present application, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are all MOSFET switches.

[0016] As an optional implementation scheme of the present application, the four-switch converter is a Buck-Boost converter.

[0017] The present application also provides a control method for smooth switching of a cascade-type isolation converter, which is used for the control system for smooth switching of the cascade-type isolation converter, comprising:

[0018] Acquire input data of the control system at the current moment, wherein the input data includes input voltage, input current, and inductor current, wherein the inductor current includes filter inductor current and excitation inductor current;

[0019] Compare the input voltage with a preset voltage threshold range, and determine the working mode of the four-switch converter at the next moment according to the judgment result;

[0020] Obtaining a Kalman filter equation corresponding to the working mode;

[0021] Inputting the input data into the Kalman filter equation to obtain corrected input data;

[0022] Performing a prediction calculation on the corrected input data according to a preset cost function to obtain a duty cycle required by a driving circuit of the control system when the control system is in the working mode;

[0023] At the next moment, the four-switch converter switches to the working mode, the drive circuit operates according to the duty cycle, processes the input data, and outputs output data that meets the preset output value.

[0024] As an optional implementation scheme of the present application, the input voltage is compared with a preset voltage threshold range, and the working mode of the four-switch converter at the next moment is determined according to the judgment result, including:

[0025] When the input voltage is less than the minimum voltage value in the preset voltage threshold range, determining that the operation mode of the four-switch converter is the Boost mode at the next moment;

[0026] When the input voltage is greater than the maximum voltage value in the preset voltage threshold range, determining that the working mode of the four-switch converter is Buck mode at the next moment;

[0027] When the input voltage is equal to the minimum voltage value or the maximum voltage value or is between the minimum voltage value and the maximum voltage value, it is determined that the operating mode of the four-switch converter at the next moment is the Buck-Boost mode.

[0028] As an optional implementation scheme of the present application, obtaining the Kalman filter equation corresponding to the working mode includes:

[0029] Obtain mathematical modeling expressions corresponding to Buck mode, Buck-Boost mode and Boost mode respectively;

[0030] Get the mathematical modeling expression of Kalman filter algorithm;

[0031] The mathematical modeling expressions of the Kalman filter algorithm are respectively substituted into the mathematical modeling expressions corresponding to the Buck mode, the Buck-Boost mode and the Boost mode to obtain the corresponding Kalman filter equations.

[0032] As an optional implementation scheme of the present application, predictive calculation is performed on the corrected input data according to a preset cost function to obtain the duty cycle required by the driving circuit of the control system when the control system is in the working mode, including:

[0033] Substituting the input data into the preset cost function, solving the partial derivative of the preset cost function, and obtaining the duty cycle required by the drive circuit of the control system in the working mode.

[0034] The present application also provides an electronic device, comprising:

[0035] processor;

[0036] a memory for storing processor-executable instructions;

[0037] Wherein, the processor is configured to implement the above-mentioned control method for smooth switching of the cascaded isolation converter when executing the executable instructions.

[0038] Beneficial effects of this application:

[0039] The control system and method of the present invention can adopt different control strategies according to the different front-end input voltages while taking efficiency into consideration, and smoothly switch to other working modes when the voltage changes over a large range, thereby improving the dynamic response of the system, and realizing isolation of the input and output ends, thereby protecting the back-end electrical equipment.

[0040] Other features and aspects of the present application will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the present application and, together with the description, serve to explain the principles of the present application.

[0042] Figure 1 A schematic diagram showing the circuit structure of a control system for smooth switching of a cascaded isolation converter according to an embodiment of the present application;

[0043] Figure 2 A flow chart showing a control method for smooth switching of a cascaded isolation converter according to an embodiment of the present application;

[0044] Figure 3 A data change diagram of an embodiment of the present application is shown. DETAILED DESCRIPTION

[0045] Various exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0046] Among them, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application or simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0048] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0049] In addition, in order to better illustrate the present application, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present application.

[0050] Example 1

[0051] Figure 1 FIG. 1 is a schematic diagram showing a circuit structure of a control system for smooth switching of a cascaded isolation converter according to an embodiment of the present application. Figure 1 As shown, it includes: a first-level circuit and a second-level circuit, and the first-level circuit and the second-level circuit are cascaded; the cascade connection of the first-level circuit and the second-level circuit can realize both wide voltage input and voltage isolation.

[0052] The first stage circuit includes a four-switch converter, which includes: a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, and a filter inductor L. The first switch Q1 and the second switch Q2 form a front bridge arm, the third switch Q3 and the fourth switch Q4 form a rear bridge arm, and the input capacitor C in , bus capacitance C bus , wherein one end of the filter inductor L is connected to the midpoint of the bridge arm of the front bridge arm, and the other end of the filter inductor L is connected to the midpoint of the bridge arm of the rear bridge arm;

[0053] The second stage circuit is a half-bridge LLC converter, which includes a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, a transformer T1, a resonant inductor L r , resonant capacitor C r , output capacitor C0, where the resonant inductor L r With the resonant capacitor C rThe fifth switch Q5 and the sixth switch Q6 are connected in series and connected to the primary side of the transformer T1 and both ends of the sixth switch Q6. The seventh switch Q7 and the eighth switch Q8 are connected in series to the secondary side of the transformer T1 and in parallel with the output capacitor C0. The half-bridge LLC converter can realize zero voltage turn-on of the fifth switch Q5 and the sixth switch Q6 and zero current turn-on of the seventh switch Q7 and the eighth switch Q8, thereby improving efficiency and realizing input and output isolation.

[0054] At the other end of the transformer T1 , a resistor R0 is arranged in parallel with the seventh switch Q7 and the eighth switch Q8 to ensure that the subsequent circuit is still in a high-efficiency working range when there is no external load.

[0055] Figure 1 Medium excitation inductance L m In parallel with the primary side of transformer T1, the resonant capacitor C r One end and the excitation inductance L m One end of the resonant inductor L is connected to the sixth switch Q6. r One end is connected to the excitation inductor L m , the primary side of transformer T1 is connected, and the other end is connected to the midpoint of the front bridge arm. r , Excitation inductance L m , resonant capacitor C r A resonant cavity network is formed.

[0056] But in reality, the excitation inductance L m It is built-in transformer T1, that is, the primary side of transformer T1 has inductance when winding, which is different from the resonant inductance L r is the magnetizing inductance L m In this embodiment, the design process of transformer T1 includes the excitation inductance L m .

[0057] As an optional implementation scheme of the present application, the duty cycles of the first switch Q1 and the second switch Q2 are complementary; the duty cycles of the third switch Q3 and the fourth switch Q4 are complementary; the duty cycles of the fifth switch Q5 and the sixth switch Q6 are complementary; and the duty cycles of the seventh switch Q7 and the eighth switch Q8 are complementary.

[0058] The first switch Q1 and the second switch Q2 form a group of switches. The first switch Q1 and the second switch Q2 are turned on alternately. When the first switch Q1 is turned on, the second switch Q2 is turned off. Therefore, the duty ratios of the first switch Q1 and the second switch Q2 are complementary. Similarly, the third switch Q3 and the fourth switch Q4 form a group of switches, the fifth switch Q5 and the sixth switch Q6 form a group of switches, and the seventh switch Q7 and the eighth switch Q8 form a group of switches. In each group of switches, the duty ratios of the two switches are complementary. In this embodiment, an MCU generates four groups of complementary drive signals according to different input conditions, that is, corresponding duty ratios, and then controls the closing and opening of the eight switches.

[0059] As an optional implementation scheme of the present application, the first stage circuit further includes: an input capacitor C in and bus capacitance C bus ; Input capacitance C in Connected in parallel with the high-voltage power battery and the front bridge arm at the front input end of the control system; bus capacitor C bus In parallel with the rear bridge arm.

[0060] Among them, the input capacitor C in Relative to the entire first-stage circuit, the bus capacitor C is set at the front end of the first-stage circuit. bus Set at the back end of the first stage circuit, the input capacitor C in and bus capacitance C bus Both are used for energy storage and filtering.

[0061] As an optional implementation scheme of the present application, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8 are all MOSFET switches.

[0062] In this embodiment, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8 are all N-channel enhancement MOSFETs, which can reduce energy loss when the control system is in the on state, thereby improving the overall efficiency of the circuit. And it has a faster response speed and can quickly respond to changes in the driving signal.

[0063] As an optional implementation of the present application, the four-switch converter is a Buck-Boost converter.

[0064] The front-stage four-switch converter adopts a Buck-Boost converter, and the Buck-Boost converter has three working modes: Buck, Buck-Boost, and Boost.

[0065] In the Buck mode, the first switch Q1, the second switch Q2, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7 and the eighth switch Q8 are closed and opened under the control of the driving circuit, the third switch Q3 is normally closed, and the fourth switch Q4 is normally open.

[0066] In the Buck-Boost mode, the first switch Q1 , the second switch Q2 , the third switch Q3 , the fourth switch Q4 , the fifth switch Q5 , the sixth switch Q6 , the seventh switch Q7 , and the eighth switch Q8 are closed and opened under the control of the driving circuit.

[0067] When in the Boost mode, the third switch Q3, the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7 and the eighth switch Q8 are closed and opened under the control of the driving circuit, the first switch Q1 is normally closed, and the second switch Q2 is normally open.

[0068] The control system can adopt different control strategies according to the front-end input voltage while considering efficiency, and smoothly switch to other working modes when the voltage changes over a large range, and realize the isolation of input and output ends, thus protecting the back-end electrical equipment.

[0069] Example 2

[0070] Figure 2 A flow chart showing a control method for smooth switching of a cascaded isolation converter according to an embodiment of the present application is shown. A control system for smooth switching of a cascaded isolation converter in Example 1, such as Figure 2 As shown, including:

[0071] S100, obtaining input data of the control system at a current moment, the input data including input voltage, input current, and inductor current, wherein the inductor current includes filter inductor current and excitation inductor current;

[0072] In this embodiment, a high-voltage power battery pack is connected to the front end of the converter. The power and voltage of the high-voltage power battery pack will decrease significantly with use. Therefore, the converter needs to meet a wide voltage input. To ensure that the expected output voltage and output current can be obtained when the voltage is constantly changing, this embodiment uses the MCU to collect the input data of the control system at the current moment. The input data includes input voltage, input current, and inductor current. The inductor current includes filter inductor current and excitation inductor current. The input voltage is used to determine which working mode the control system needs to be in at the next moment, thereby obtaining the expected output voltage, output current, and inductor current.

[0073] S200, comparing the input voltage with a preset voltage threshold range, and determining the working mode of the four-switch converter at the next moment according to the judgment result;

[0074] The preset voltage threshold range can be set according to actual conditions, and the input voltage relative to the voltage threshold range is judged to determine the working mode of the four-switch converter to be switched at the next moment.

[0075] S300, obtaining a Kalman filter equation corresponding to the working mode;

[0076] In this embodiment, considering that the noise interference in the environment and the drift of component parameters will affect the collected input data, resulting in deviations in the input data, the input data needs to be corrected. The four-switch converter has three working modes, each of which corresponds to different working conditions. Using a unified correction method for the input data can easily lead to the input data not being able to obtain the expected output voltage, output current, and inductor current in each working mode. Therefore, in this embodiment, each working mode has a corresponding Kalman filter equation to correct the input data.

[0077] S400, inputting the input data into the Kalman filter equation to obtain the corrected input data; after obtaining the Kalman filter equation corresponding to each working mode, the input data is corrected according to the Kalman filter equation corresponding to the working mode used at the next moment. Furthermore, the output data obtained in the working mode can also be sampled and the corresponding Kalman filter equation is used to perform data correction.

[0078] S500, performing prediction calculation on the corrected input data according to a preset cost function to obtain a duty cycle required by a driving circuit of the control system when the control system is in a working mode;

[0079] The preset cost function is solved to obtain the duty cycle that minimizes the cost function, and the minimum duty cycle is input as the duty cycle required for each field effect tube under smooth switching of different modes. The preset cost function can be built into a conventional prediction model, and the corrected input data is input into the conventional prediction model to achieve the purpose of predicting the duty cycle required when the drive circuit of the control system switches the working mode under the working mode of the four-switch converter at the next moment.

[0080] S600, at the next moment, the four-switch converter switches to the working mode, the driving circuit operates according to the duty cycle, processes the input data, and outputs output data that meets the preset output value.

[0081] The predicted duty cycle is output to the corresponding drive circuit for control, and the drive circuit processes the input voltage, input current and inductor current according to the gain effect of the duty cycle to obtain output data output by the drive circuit, wherein the output data includes output voltage, output current and inductor current. In this embodiment, the output data is the output voltage, output current and inductor current that meet the expected output value when the input voltage changes rapidly.

[0082] As an optional implementation scheme of the present application, the input voltage is compared with a preset voltage threshold range and judged, and the working mode of the four-switch converter at the next moment is determined according to the judgment result, including: when the input voltage is less than the minimum voltage value in the preset voltage threshold range, it is determined that the working mode of the four-switch converter at the next moment is Boost mode; when the input voltage is greater than the maximum voltage value in the preset voltage threshold range, it is determined that the working mode of the four-switch converter at the next moment is Buck mode; when the input voltage is equal to the minimum voltage value or the maximum voltage value or is between the minimum voltage value and the maximum voltage value, it is determined that the working mode of the four-switch converter at the next moment is Buck-Boost mode.

[0083] In Buck mode, the first switch Q1 is turned on and the second switch Q2 is turned off. At this time, the input voltage charges the filter inductor L, the filter inductor L stores energy, and provides energy to the load. Its mathematical modeling expression is as follows:

[0084]

[0085] When the second switch Q2 is turned on and the first switch Q1 is turned off, the filter inductor L is discharged and the energy of the load is supplied by the bus capacitor C. bus And filter inductor L are provided at the same time. Its mathematical modeling expression is as follows:

[0086]

[0087] In Buck-Boost mode, when the first switch Q1 and the fourth switch Q4 are turned on and the second switch Q2 and the third switch Q3 are turned off, the input voltage charges the filter inductor L, and the filter inductor L stores energy; the input voltage does not provide energy to the load, and the energy bus capacitor C of the load bus The mathematical modeling expression is as follows:

[0088]

[0089] When the second switch Q2 and the third switch Q3 are turned on and the first switch Q1 and the fourth switch Q4 are turned off, the filter inductor L is discharged and the energy of the load is supplied by the bus capacitor C. bus And filter inductor L are provided at the same time. Its mathematical modeling expression is as follows:

[0090]

[0091] In Boost mode, when the fourth switch Q4 is turned on and the third switch Q3 is turned off, the input voltage charges the filter inductor L, and the filter inductor L stores energy; the input voltage does not provide energy to the load, and the energy bus capacitor C of the load bus The mathematical modeling expression is as follows:

[0092]

[0093] When the third switch Q3 is turned on and the fourth switch Q4 is turned off, the input voltage and the filter inductor L provide energy to the load on the one hand and to the bus capacitor C on the other hand. bus Charging. Its mathematical modeling expression is as follows:

[0094]

[0095] It should be noted that the above mathematical modeling expressions are all continuous functions, which need to be discretized during the control process.

[0096] As an optional implementation scheme of the present application, the Kalman filter equation corresponding to the working mode is obtained, including: obtaining the mathematical modeling expressions corresponding to the Buck mode, Buck-Boost mode and Boost mode respectively; obtaining the mathematical modeling expression of the Kalman filter algorithm; substituting the mathematical modeling expression of the Kalman filter algorithm into the mathematical modeling expressions corresponding to the Buck mode, Buck-Boost mode and Boost mode respectively to obtain the corresponding Kalman filter equation.

[0097] The mathematical modeling of the Kalman filter algorithm is expressed as:

[0098] x k =Ax k-1 +Bu k-1 +w k-1

[0099] Among them, x k is the state matrix, u k is the control matrix, A is the state transfer matrix, B is the state control matrix, w k is the dynamic noise at time k.

[0100] The observation equation is:

[0101] y k =Hx k +v k

[0102] Among them, y k is the observation matrix, H is the observation matrix, v k is the observation noise at time k.

[0103] The Kalman filter algorithm can be divided into two parts: time update and measurement update.

[0104] The expression for time update is:

[0105]

[0106] Among them, P k is the posterior state estimation error covariance matrix, is the prior state estimation error covariance matrix, and Q is the covariance matrix of process noise.

[0107] The main function of time updating is to infer the prior estimate of the state variable and its error covariance at the current moment (i.e., moment k) based on the state estimate at the previous moment (i.e., moment k-1).

[0108] The expression for measuring the update is:

[0109]

[0110] Among them, K k is the Kalman gain, R is the covariance matrix of the measurement noise, is the posterior estimate, is a priori estimate.

[0111] The main function of the measurement update is to use the observations at the current moment to correct the prior estimate obtained in the time update step, thereby obtaining a more accurate posterior estimate.

[0112] Substituting the Kalman filter algorithm into the mathematical modeling expression of each working mode, the Kalman filter equation for each working mode is obtained, random noise is suppressed and sampling deviation is corrected for the collected input data, and the corrected input data is output.

[0113] As an optional implementation scheme of the present application, a predictive calculation is performed on the corrected input data according to a preset cost function to obtain the duty cycle required by the drive circuit of the control system when the control system is in the working mode, including: substituting the input data into the preset cost function, solving the partial derivative of the preset cost function, and obtaining the duty cycle required by the drive circuit of the control system when the control system is in the working mode.

[0114] In this embodiment, the preset cost function is:

[0115]

[0116] Among them, E k represents the error, u k Represents input, E N represents the final error value, Q, R, and F are the weight matrices of error, input, and final error value, respectively.

[0117]

[0118] The duty cycle that minimizes the cost function can be solved, and this duty cycle is the duty cycle required for smooth switching between different modes.

[0119] like Figure 3 , from top to bottom are input voltage, output voltage, inductor current, and output current. The area represents the inductor current, and the solid line in the area represents the output current. Figure 3 It can be seen that when the input voltage changes rapidly, the output voltage, inductor current, and output current are still in line with expectations, reflecting the smooth switching and output between modes.

[0120] Through the above control method, smooth switching and output between various modes can be achieved when the input voltage changes rapidly, thereby improving the response and dynamic characteristics of the control system.

[0121] Example 3

[0122] Furthermore, an electronic device is proposed, comprising:

[0123] processor;

[0124] a memory for storing processor-executable instructions;

[0125] The processor is configured to implement the control method for smooth switching of the cascaded isolation converter of embodiment 2 when executing executable instructions.

[0126] Meanwhile, the electronic device in the embodiment of the present disclosure may also include an input device and an output device, wherein the processor, the memory, the input device and the output device may be connected via a bus or other means, which are not specifically limited here.

[0127] The memory is a computer-readable storage medium for the control method for smooth switching of cascaded isolated converters, and can be used to store software programs, computer executable programs, and various modules, such as the program or module corresponding to the control method for smooth switching of cascaded isolated converters in the embodiment of the present disclosure. The processor executes various functional applications and data processing of the electronic device by running the software program or module stored in the memory.

[0128] The input device can be used to receive input numbers or signals. The signal can be a key signal related to user settings and function control of the device / terminal / server. The output device can include a display device such as a display screen.

[0129] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A control system for smooth switching of cascaded isolation converters, characterized in that: include: A first-stage circuit and a second-stage circuit, wherein the first-stage circuit and the second-stage circuit are connected in cascade; The first-stage circuit includes a four-switch converter, which includes: a first switch, a second switch, a third switch, a fourth switch, and a filter inductor, wherein the first switch and the second switch constitute a front bridge arm, and the third switch and the fourth switch constitute a rear bridge arm, wherein one end of the filter inductor is connected to the midpoint of the bridge arm of the front bridge arm, and the other end of the filter inductor is connected to the midpoint of the bridge arm of the rear bridge arm; The second-stage circuit is a half-bridge LLC converter, which includes a fifth switch, a sixth switch, a seventh switch, an eighth switch, a transformer, a resonant capacitor, a resonant inductor, and an output capacitor, wherein the resonant inductor is connected in series with the resonant capacitor and is connected to one end of the transformer and both ends of the sixth switch, and the seventh switch and the eighth switch are connected in series to the other end of the transformer and in parallel with the output capacitor.

2. The control system for smooth switching of cascaded isolation converters according to claim 1, characterized in that: The duty cycles of the first switch and the second switch are complementary; The duty cycles of the third switch and the fourth switch are complementary; The duty cycles of the fifth switch and the sixth switch are complementary; The duty cycles of the seventh switch and the eighth switch are complementary.

3. The control system for smooth switching of cascaded isolation converters according to claim 1, characterized in that: The first stage circuit also includes: an input capacitor and a bus capacitor; The input capacitor is connected in parallel with the high-voltage power battery at the front input end of the control system and the front bridge arm; The bus capacitor is connected in parallel with the rear bridge arm.

4. The control system for smooth switching of cascaded isolation converters according to claim 2, characterized in that: The first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are all MOSFET switches.

5. The control system for smooth switching of cascaded isolation converters according to claim 1, characterized in that: The four-switch converter is a Buck-Boost converter.

6. A control method for smooth switching of a cascaded isolation converter, used for a control system for smooth switching of a cascaded isolation converter as claimed in any one of claims 1 to 6, characterized in that: include: Acquire input data of the control system at the current moment, wherein the input data includes input voltage, input current, and inductor current, wherein the inductor current includes filter inductor current and excitation inductor current; Compare the input voltage with a preset voltage threshold range, and determine the working mode of the four-switch converter at the next moment according to the judgment result; Obtaining a Kalman filter equation corresponding to the working mode; Inputting the input data into the Kalman filter equation to obtain corrected input data; Performing a prediction calculation on the corrected input data according to a preset cost function to obtain a duty cycle required by a driving circuit of the control system when the control system is in the working mode; At the next moment, the four-switch converter switches to the working mode, the drive circuit operates according to the duty cycle, processes the input data, and outputs output data that meets the preset output value.

7. The control method for smooth switching of cascaded isolation converters according to claim 6, characterized in that: Comparing the input voltage with a preset voltage threshold range, and determining the working mode of the four-switch converter at the next moment according to the judgment result, includes: When the input voltage is less than the minimum voltage value in the preset voltage threshold range, determining that the operation mode of the four-switch converter is the Boost mode at the next moment; When the input voltage is greater than the maximum voltage value in the preset voltage threshold range, determining that the working mode of the four-switch converter is Buck mode at the next moment; When the input voltage is equal to the minimum voltage value or the maximum voltage value or is between the minimum voltage value and the maximum voltage value, it is determined that the operating mode of the four-switch converter at the next moment is the Buck-Boost mode.

8. The control method for smooth switching of cascaded isolation converters according to claim 7, characterized in that: Obtaining the Kalman filter equation corresponding to the working mode includes: Obtain mathematical modeling expressions corresponding to Buck mode, Buck-Boost mode and Boost mode respectively; Get the mathematical modeling expression of Kalman filter algorithm; The mathematical modeling expressions of the Kalman filter algorithm are respectively substituted into the mathematical modeling expressions corresponding to the Buck mode, the Buck-Boost mode and the Boost mode to obtain the corresponding Kalman filter equations.

9. The control method for smooth switching of cascaded isolation converters according to claim 6, characterized in that: Predicting and calculating the corrected input data according to a preset cost function to obtain a duty cycle required by a driving circuit of the control system when the control system is in the working mode includes: Substituting the input data into the preset cost function, solving the partial derivative of the preset cost function, and obtaining the duty cycle required by the drive circuit of the control system in the working mode.

10. An electronic device, characterized in that: include: processor; a memory for storing processor-executable instructions; Wherein, the processor is configured to implement the control method for smooth switching of the cascaded isolation converter as described in any one of claims 6 to 9 when executing the executable instructions.

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