Analytic optimization of burst mode light load efficiency improvement method for three active bridge converter and related device

Abstract

The application discloses a three-active-bridge converter analytic optimization burst mode light-load efficiency improvement method and related device, comprising: the burst mode of the three-active-bridge converter is divided into an on state and an off state, the time lengths of the on state and the off state are respectively t on and t off Wherein, the on state is sequentially divided into a first pulse stage, a quasi-steady state stage and a last pulse stage; the time length of the off state is determined according to the load, the method and the related device can be applied to the three-active-bridge converter with multiple secondary side ports, improve the light-load efficiency of the three-active-bridge converter, and the control quantity has an analytic solution, so that the simplicity of control is ensured.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology DC / DC converters, and relates to an analytical optimization method and related apparatus for improving the efficiency of a three-active-bridge converter under light load in burst mode. Background Technology

[0002] With the increasing development of DC microgrids, triple-active-bridge (TAB) converters, with their integrated structure, excellent electrical isolation performance, and soft-switching characteristics, have been widely used in communication base stations, electric vehicle charging, and data center power supply. Traditional single-phase-shift modulation strategies only adjust the phase shift angle between ports. Under light loads, this results in large circulating current and loss of soft switching, leading to low efficiency under light loads. Therefore, an intra-port phase shift angle can be introduced to form a multi-phase-shift modulation strategy, reducing circulating current and expanding the soft-switching range, thereby improving efficiency under light loads. However, multi-phase-shift modulation strategies have high control complexity, often requiring lookup tables or online optimization. This places high demands on the controller's storage space or computing power, limiting the practical application of multi-phase-shift modulation strategies in industry.

[0003] Burst mode is an effective way to improve the efficiency of a converter under light load. During the burst turn-on phase, the converter operates in a quasi-steady-state manner, with its instantaneous power transfer exceeding the average output power, thus allowing the system to operate in a higher efficiency range. During the burst turn-off phase, all power devices are turned off, resulting in almost no power loss. The output voltage rises slightly during the turn-on phase and falls slightly during the turn-off phase. Although the ripple is slightly larger than in continuous operation mode, a stable DC output voltage can be maintained through the filtering effect of the output capacitor. By alternating between the turn-on and turn-off phases, the average efficiency of the converter under light load conditions can be significantly improved, even approaching the peak efficiency.

[0004] To address the issue of improving efficiency under light loads in dual-active-bridge (DAB) converters, domestic and international scholars have proposed optimizing burst modes. This involves adding a first pulse and a last pulse to the quasi-steady-state and off-state conditions to eliminate DC bias current. However, this method requires online iterative calculation to obtain the optimal switching sequence, which not only increases the computational burden on the controller but also causes the pulse widths of the first and last pulses to vary with load and voltage gain. Theoretically, two secondary-side ports with different loads and voltages should have different first and last pulse widths, but they share a primary side, leading to inconsistent primary-side switching pulses. Therefore, this type of method cannot be applied to three-active-bridge converters with multiple secondary-side ports. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an analytical optimization method and related apparatus for improving the efficiency of a three-active-bridge converter under light load in burst mode. This method and apparatus can be applied to a three-active-bridge converter with multiple secondary ports to improve the light load efficiency of the three-active-bridge converter. At the same time, the control quantity has an analytical solution to ensure the simplicity of control.

[0006] To achieve the above objectives, this invention discloses an analytical optimization method for improving the efficiency of a three-active-bridge converter under light load conditions in burst mode, comprising: The burst mode of the three-phase active bridge converter is divided into an on state and an off state, with the durations of the on state and the off state being respectively... t on and t off The on-state is divided into three phases: the initial pulse phase, the quasi-steady-state phase, and the final pulse phase; the off-state duration is... Determined based on the weight of the load.

[0007] Furthermore, the first pulse stage and the last pulse stage are used to ensure that the inductor current is not biased. The first pulse width and the last pulse width of the primary and secondary sides of the three active bridge converter are both 1 / 4 of a switching cycle.

[0008] Furthermore, the phase shift angles of the first and last pulses on the secondary side of the three active bridge converter pass through the phase shift angle during the quasi-steady state period. and Calculated.

[0009] Furthermore, the duration of the shutdown state for: (2) in, T s For the switching cycle, I o,full To provide full-load output current, I o This is the actual output current. N burst The number of periods in the quasi-steady-state phase. P steady * This represents the equivalent transmission power during the quasi-steady-state phase.

[0010] Furthermore, the smaller value among the turn-off times calculated for each secondary port of the three-active-bridge converter is selected as the uniform turn-off time for each secondary port in the three-active-bridge converter.

[0011] Furthermore, when the load current at the two output ports of the three active bridge converter is detected... I o,2 and Io,3 All are below the preset threshold I th When this happens, the three-phase active bridge converter enters burst mode, according to the user-defined settings. P steady * and N burst and the samples obtained I o,2 and I o,3 Calculate the turn-off time of each of the two output ports of the three active bridge converter. t off,2 and t off,3 The smaller of the two values ​​is selected as the uniform off-time of the two output ports of the three active bridge converter.

[0012] Furthermore, the output voltage sample value of one output port 2 of the three active bridge converter is... V 2 and its reference value V 2,ref The error between the inputs is used to generate the phase shift angle during the quasi-steady-state operation phase using a proportional-integral controller, and the phase shift angles of the first and last pulses are calculated.

[0013] Furthermore, when the load current at any output port of the three active bridge converter exceeds the threshold... I th When this happens, the three active bridge converters switch to single-phase-shift modulation mode.

[0014] This invention discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the analytical optimization burst mode light load efficiency improvement method for a three-active-bridge converter.

[0015] This invention discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter.

[0016] The present invention has the following beneficial effects: The analytical optimization method and related devices for improving efficiency under light load in burst mode of the three active bridge converter described in this invention, in specific operation, have the following durations for the on and off states: t on and t off The on-state is divided into three phases: the initial pulse phase, the quasi-steady-state phase, and the final pulse phase; the off-state duration is... Based on the load intensity, the switching sequence in burst mode can be rationally configured without introducing online optimization or iterative calculations, thereby effectively eliminating the DC bias problem of inductor current. Compared with multi-phase modulation and traditional burst mode that rely on lookup tables or online optimization, this invention significantly reduces the computational complexity and storage resource consumption of the digital controller. Simultaneously, during the burst turn-on phase, the three active bridge converter always operates in a high-efficiency quasi-steady-state operating range, and during the burst turn-off phase, all switching devices are turned off, thus effectively reducing losses under light load conditions. In summary, this invention improves the light-load efficiency of the three active bridge converter while maintaining the simplicity of the control strategy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1a This is the topology diagram of a dual active bridge converter; Figure 1b This is the topology diagram of a three-active-bridge converter; Figure 2a The waveform diagram of the dual active bridge converter under 80% load is shown. Figure 2b The waveform diagram of the dual active bridge converter under 15% load is shown. Figure 3a The efficiency curve of the dual active bridge converter is shown. Figure 3b A schematic diagram of the soft-switching range of a dual active bridge converter; Figure 4 The waveform diagrams for burst modes of dual active bridge converters in existing literature are shown. Figure 5 Waveform diagram of the burst mode of the proposed three active bridge converter; Figure 6 This is a control block diagram for the burst mode of a three-active-bridge converter. Figure 7a The waveform diagrams are experimental waveforms of the burst mode of the three active bridge converter. Port 3 is the output voltage of 180 V with 14% load, and port 2 is the output voltage of 220 V with 10% load. Figure 7b The waveform diagrams are experimental waveforms of the three active bridge converter under traditional single-phase-shift modulation. Port 3 outputs 180 V with 14% load; Port 2 outputs 220 V with 10% load. Figure 8aThis is a comparison of the experimental efficiency curves of the three active bridge converter in burst mode and traditional phase-shift modulation. The operating conditions are: port 2, 180V output voltage, 14% load; port 3, 220V output voltage. The horizontal axis represents the load of port 3. Figure 8b This is a comparison of the experimental efficiency curves of the three active bridge converter in burst mode and traditional phase-shift modulation. The operating conditions are: port 2, 220V output voltage, 20% load; port 3, 180V output voltage. The horizontal axis represents the load of port 3. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0023] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0024] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0027] Example 1 refer to Figure 1a and Figure 1b By extending a port on the secondary side of the dual active bridge converter and replacing the dual-winding transformer in the dual active bridge converter with a three-winding transformer, a three active bridge converter is obtained.

[0028] refer to Figure 2a and Figure 2b For a dual active bridge converter, under heavy load (taking 80% load as an example), all switches can achieve zero-voltage-switching (ZVS), resulting in high converter efficiency. However, under light load (taking 15% load as an example), the switches on the secondary side cannot achieve soft switching, leading to higher circulating current and lower converter efficiency. A three-phase active bridge converter is derived from a dual active bridge converter and therefore exhibits similar properties.

[0029] refer to Figure 3aThe experimental results show that the dual active bridge converter has a peak efficiency of 96.1% near 60% load; however, the efficiency is less than 90% below 25% load. The first reason is that the proportion of auxiliary circuit losses to total losses increases under light load; the second reason is that the circulating current power is relatively large; and the third reason is that the soft-switching characteristics are easily lost under light load.

[0030] refer to Figure 3b Assuming voltage conversion ratio k The definition of k = V i / NV o ,in, V i Input voltage, N The transformer turns ratio V o For the output voltage, when k When the value equals 1, the converter can achieve soft switching across the entire load range; however, when... k When the deviation is 1, the converter loses soft switching under light load.

[0031] refer to Figure 4 Existing literature categorizes the burst modes of dual active bridge converters into on-state and off-state. The on-state is further divided into the first pulse stage, the quasi-steady-state stage, and the last pulse stage. The first and last pulse stages are used to ensure that the inductor current is unbiased. The pulse widths of these stages are obtained through online optimization by the controller, and the pulse widths vary with the load and output voltage. Therefore, this method is only applicable to dual active bridge converters and cannot be extended to triple active bridge converters. This is because triple active bridge converters have two different output ports, which should theoretically have different pulse widths, yet they share a primary-side port. Furthermore, online pulse width optimization requires high computing power from the controller, making it difficult to apply in practical engineering.

[0032] refer to Figure 5 The burst mode of the three active bridge converter described in this invention is divided into an on state and an off state, and the durations of the on state and the off state are respectively... t on and t off The activation state is divided into three phases: the initial pulse phase, the quasi-steady-state phase, and the final pulse phase. The quasi-steady-state phase has the following cycle count: N burst The equivalent transmission power in the quasi-steady-state phase is P steady *The first and last pulse phases are used to ensure that the inductor current is unbiased. The first and last pulse widths of both the primary and secondary sides of the three-phase active bridge converter are 1 / 4 of a switching cycle. This fixed width ensures that the proposed burst mode is applicable to three-phase active bridge converters with multiple secondary ports. Based on the time-domain model, the phase shift angles of the first and last pulses on the secondary side have analytical solutions, derived from the phase shift angles during the quasi-steady-state period. and The calculation yields the result shown in equation (1): (1) refer to Figure 6 The control block diagram of a three-phase active bridge converter in burst mode. Assume each switching cycle is... T s Full-load output current is I o,full The actual output current is I o The duration of the shutdown state is determined based on the load. for: (2) Since all secondary ports in a three-phase active bridge converter share the same primary side, only a uniform turn-off duration can be selected in actual control.

[0033] In the same P steady * Under these conditions, the lighter the load, the longer the shutdown duration. When a longer shutdown duration is selected, the secondary side with a heavier load needs to increase its equivalent transmission power, which may lead to… P steady * If the value exceeds 1, it cannot be achieved; when a shorter shutdown duration is selected, the secondary port with a lighter load corresponds to... P steady * It remains within the feasible range of 0 to 1. Therefore, the smaller value among the turn-off times calculated from each secondary port of the three active bridge converter is selected as the unified turn-off time.

[0034] When the load current at the two output ports of the three active bridge converter is detected I o,2 and I o,3 All are below the preset threshold I th When this happens, the three-phase active bridge converter enters burst mode, according to the user-defined settings. P steady * and N burst and the samples obtained I o,2and I o,3 Calculate the turn-off time of each of the two output ports of the three active bridge converter. t off,2 and t off,3 The smaller of the values ​​is selected as the uniform off-time. The output voltage sample value of port 2 is then used. V 2 and its reference value V 2,ref The error between the inputs is used to a proportional-integral (PI) controller to generate the phase shift angle during the quasi-steady-state operation phase. The phase shift angles of the first and last pulses are calculated using equation (1) to eliminate DC bias. The control process of port 3 is the same as that of port 2. When the load current of any output port exceeds the threshold... I th When this happens, the three active bridge converters switch to single-phase-shift modulation mode.

[0035] refer to Figure 7a and Figure 7b A comparison of the waveforms of the burst mode and single-phase-shift modulation strategy of the three active bridge converter shows that the equivalent load during the quasi-steady state period of the burst mode is about 60%, which is close to the peak efficiency point, while the load under single-phase-shift modulation is 10%. Therefore, the burst mode has higher efficiency than single-phase-shift modulation.

[0036] refer to Figure 8a and Figure 8b The three active bridge converter has a significantly higher light load efficiency in burst mode than the traditional single phase-shift modulation, with the efficiency increasing from 89.81% to 92.59% under 10% load, an increase of 2.78%.

[0037] Example 2 A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the analytical optimization method for improving the efficiency of a three-active-bridge converter under light load in burst mode. For example, the method includes: the burst mode of the three-active-bridge converter is divided into an on-state and an off-state, the durations of which are respectively... t on and t off The on-state is divided into three phases: the initial pulse phase, the quasi-steady-state phase, and the final pulse phase; the off-state duration is... The location is determined based on the workload. The memory may include main memory, such as high-speed random access memory (RAM), or non-volatile memory, such as at least one disk storage device. The processor, network interface, and memory are interconnected via an internal bus, which can be an industry-standard architecture bus, a peripheral component interconnection standard bus, or an extended industry-standard architecture bus. The bus can be categorized as an address bus, data bus, or control bus. The memory stores programs; specifically, the program may include program code, which includes computer operation instructions. The memory may include main memory and non-volatile memory, and provides instructions and data to the processor.

[0038] Example 3 A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the analytical optimization method for improving the efficiency of a three-active-bridge converter under light load in burst mode. For example, the method includes: the burst mode of the three-active-bridge converter is divided into an on-state and an off-state, the durations of which are respectively... t on and t off The on-state is divided into three phases: the initial pulse phase, the quasi-steady-state phase, and the final pulse phase; the off-state duration is... The determination is based on the workload. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0039] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0040] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0041] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0042] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0043] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0044] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0045] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for analytically optimizing burst-mode light-load efficiency improvement of a three-active-bridge converter, characterized in that, include: The burst mode of the three-phase active bridge converter is divided into an on state and an off state, with the durations of the on state and the off state being respectively... t on and t off The on-state is divided into three phases: the initial pulse phase, the quasi-steady-state phase, and the final pulse phase; the off-state duration is... Determined based on the weight of the load.

2. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 1, characterized in that, The first pulse stage and the last pulse stage are used to ensure that the inductor current is not biased. The first pulse width and the last pulse width of the primary and secondary sides of the three active bridge converter are both 1 / 4 of a switching cycle.

3. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 1, characterized in that, The phase shift angles of the first and last pulses on the secondary side of the three-phase active bridge converter during the quasi-steady-state period. and Calculated.

4. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 1, characterized in that, Duration of shutdown for: （2） in, T s For the switching cycle, I o,full To provide full-load output current, I o This is the actual output current. N burst The number of periods in the quasi-steady-state phase. P steady * This represents the equivalent transmission power during the quasi-steady-state phase.

5. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 4, characterized in that, The smaller value among the turn-off times calculated for each secondary port of the three-active-bridge converter is selected as the uniform turn-off time for each secondary port in the three-active-bridge converter.

6. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 4, characterized in that, When the load current at the two output ports of the three active bridge converter is detected I o,2 and I o,3 All are below the preset threshold I th When this happens, the three-phase active bridge converter enters burst mode, according to the user-defined settings. P steady * and N burst and the samples obtained I o,2 and I o,3 Calculate the turn-off time of each of the two output ports of the three active bridge converter. t off,2 and t off,3 The smaller of the two values ​​is selected as the uniform off-time of the two output ports of the three active bridge converter.

7. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 4, characterized in that, Sample the output voltage value at one output port 2 of the three active bridge converter. V 2 and its reference value V 2,ref The error between the inputs is used to generate the phase shift angle during the quasi-steady-state operation phase using a proportional-integral controller, and the phase shift angles of the first and last pulses are calculated.

8. The analytical optimization method for improving efficiency under light load in burst mode of a three-active-bridge converter according to claim 4, characterized in that, When the load current at any output port of the three-phase active bridge converter exceeds the threshold I th When this happens, the three active bridge converters switch to single-phase-shift modulation mode.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the analytical optimization method for improving efficiency under light load in burst mode for a three-active-bridge converter as described in any one of claims 1-8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the analytical optimization method for improving efficiency under light load in burst mode for a three-active-bridge converter as described in any one of claims 1-8.

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