A series type bidirectional DC / DC converter for high-voltage high-power scenarios, a control method and a power system

Abstract

The application provides a series type bidirectional DC / DC converter, a control method and a power system for a high-voltage and high-power scene, wherein the converter comprises a high-voltage side port connected with a high-voltage DC bus, a low-voltage side port connected with an energy storage battery and first and second power units. The first and second power units each contain at least one group of bidirectional four-switch Buck-Boost circuits. The high-voltage sides of the first and second power units are connected in series to both ends of the high-voltage side port, and the low-voltage sides are connected in series to both ends of the low-voltage side port. The first and second power units realize bidirectional step-down, step-up or step-up / down conversion under the drive of a controller, and share the high-voltage side and low-voltage side port voltages in operation. The application realizes series voltage division through the double-side series connection structure, reduces the voltage stress of the switching device, so that the device with a lower voltage resistance level can be selected in the high-voltage and high-power scene, the cost and parasitic loss are effectively reduced, and the structure is compact.

Description

Technical Field

[0001] This invention relates to the field of power electronic equipment, and in particular to a series bidirectional DC / DC converter, control method, and power system for high-voltage, high-power scenarios. Background Technology

[0002] In high-voltage, high-power scenarios (such as mining trucks), bidirectional energy conversion between the DC bus and the onboard energy storage battery is a core component of the power system. To achieve smooth energy exchange and wide-range voltage matching between the two, a bidirectional DC / DC converter is typically required for buck, boost, or buck-boost regulation. As the hub of energy transmission, the overall performance of this converter directly determines the efficiency and reliability of the entire vehicle's power system.

[0003] Existing bidirectional power conversion solutions typically employ a traditional single-stage four-switch converter topology. However, given the increasing high-voltage DC bus applications in engineering vehicles, the power devices in a single-stage topology must directly withstand the entire bus voltage. To meet stringent voltage withstand requirements, existing solutions must utilize power switches with extremely high voltage ratings. These high-voltage devices not only incur high hardware procurement costs but also inevitably suffer from significant drawbacks such as high parasitic losses, severe electromagnetic interference, and complex drive circuit design, making it difficult to balance system economy with high conversion efficiency.

[0004] In summary, how to effectively reduce the terminal voltage stress of switching devices in high-voltage application scenarios without increasing the complexity of the structure, thereby reducing the overall hardware cost of the system and improving operating efficiency, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a series bidirectional DC / DC converter, control method and power system for high voltage and high power scenarios.

[0006] This invention discloses a series-type bidirectional DC / DC converter for high-voltage, high-power applications, comprising: The high-voltage side port is used to connect to the high-voltage DC bus. The low-voltage side port is used to connect to the energy storage battery; The first power unit and the second power unit each contain at least one set of bidirectional four-switch Buck-Boost circuits. The high-voltage side of the first power unit and the high-voltage side of the second power unit are connected in series to form a high-voltage series branch, which is connected to both ends of the high-voltage side port. The low-voltage side of the first power unit and the low-voltage side of the second power unit are connected in series to form a low-voltage series branch, which is connected to both ends of the low-voltage side port. The first power unit and the second power unit are configured to: realize bidirectional buck, boost or buck-boost conversion between the high-voltage side port and the low-voltage side port under the drive of the controller; and during operation, the voltage of the high-voltage side port is shared by the first power unit and the second power unit, and the voltage of the low-voltage side port is shared by the first power unit and the second power unit.

[0007] Preferably, the bidirectional four-switch Buck-Boost circuit specifically includes: The first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, and the energy storage inductor; The first and second switching transistors are connected in series to form a high-voltage side bridge arm, and a high-voltage side support capacitor is connected in parallel at both ends of the high-voltage side bridge arm; wherein, one end of the first switching transistor is connected to the positive terminal of the high-voltage side support capacitor, the other end of the first switching transistor is connected to one end of the second switching transistor, and the other end of the second switching transistor is connected to the negative terminal of the high-voltage side support capacitor. The fourth and third switches are connected in series to form a low-voltage side bridge arm, and low-voltage side support capacitors are connected in parallel at both ends of the low-voltage side bridge arm; wherein, one end of the fourth switch is connected to the positive terminal of the low-voltage side support capacitor, the other end of the fourth switch is connected to one end of the third switch, and the other end of the third switch is connected to the negative terminal of the low-voltage side support capacitor. The midpoint of the high-voltage side bridge arm is the connection point between the first and second switching transistors, and the midpoint of the low-voltage side bridge arm is the connection point between the fourth and third switching transistors. An energy storage inductor is connected between the midpoint of the high-voltage side bridge arm and the midpoint of the low-voltage side bridge arm.

[0008] Preferably, both the first power unit and the second power unit contain n sets of bidirectional four-switch Buck-Boost circuits connected in parallel; n≥2.

[0009] Preferably, within the same power unit: n sets of bidirectional four-switch Buck-Boost circuits share the high-voltage side support capacitor and the low-voltage side support capacitor; Furthermore, each bidirectional four-switch Buck-Boost circuit has its own independent high-voltage side bridge arm, low-voltage side bridge arm, and energy storage inductor.

[0010] Preferably, the series-type bidirectional DC / DC converter further includes a controller; The controller is electrically connected to each switching transistor in the first and second power units. The controller is configured to control the switching transistors in each group of bidirectional four-switch Buck-Boost circuits to turn on, turn off, or switch at high frequency based on the relationship between the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port, so as to achieve bidirectional energy flow.

[0011] Preferably, the controller is configured to output interleaved PWM modulation drive signals to n sets of circuits connected in parallel within the same power unit, and the drive signals of two adjacent sets of circuits are 360° / n out of phase.

[0012] Preferably, the controller is internally configured with a pressure equalization control loop and a current equalization control loop; The voltage equalization control loop is used to dynamically adjust the duty cycle of the drive signal between the first power unit and the second power unit so that the high voltage side voltage shared by the two units remains equal. The current sharing control loop is used to dynamically adjust the duty cycle of the drive signals among the n bidirectional four-switch Buck-Boost circuits within the same power unit, so that the current shared by each circuit remains equal.

[0013] The second aspect of this application provides a control method for a series-type bidirectional DC / DC converter in high-voltage, high-power scenarios, used to control any of the aforementioned series-type bidirectional DC / DC converters. The control method includes: Obtain the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port; When the converter is in charging mode, transferring energy from the high-voltage side to the low-voltage side, the following control strategy is executed based on the relationship between the high-voltage bus voltage and the energy storage battery voltage: If the high-voltage bus voltage is greater than the energy storage battery voltage, the converter is controlled to operate in Buck mode: the fourth switch is always on, and the first and second switches are complementary in conduction. If the high-voltage bus voltage is less than the energy storage battery voltage, the converter is controlled to operate in Boost mode: the first switch is always on, and the third and fourth switches are complementary in conduction. If the high-voltage bus voltage is close to the energy storage battery voltage, the converter is controlled to operate in Buck-Boost mode: the first and third switches are turned on simultaneously, the second and fourth switches are turned on simultaneously, and they are complementary to the first and third switches in conduction.

[0014] Preferably, when the converter is in a discharge mode that transfers energy from the low-voltage side to the high-voltage side, the control method further includes: If the high-voltage bus voltage is greater than the energy storage battery voltage, the converter is controlled to operate in Boost mode: the fourth switch is always on, and the second and first switches are complementary in conduction. If the high-voltage bus voltage is less than the energy storage battery voltage, the converter is controlled to operate in Buck mode: the first switch is always on, and the fourth and third switches are complementary in conduction. If the high-voltage bus voltage is close to the energy storage battery voltage, the control converter operates in Buck-Boost mode: the second and fourth switches are turned on simultaneously, the first and third switches are turned on simultaneously, and they are complementary to the second and fourth switches.

[0015] A third aspect of this application provides a power system comprising: High-voltage DC bus; Onboard energy storage batteries; and A series bidirectional DC / DC converter for high-voltage, high-power applications, as described above. The high-voltage DC bus is connected to the high-voltage side port of the converter, and the on-board energy storage battery is connected to the low-voltage side port of the converter.

[0016] Compared with existing technologies, the above technical solution has the following advantages: 1. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios provided in this application constructs a cascaded architecture with two sides connected in series. This architecture is achieved by sequentially connecting the high-voltage sides of the first and second power units in series to form a high-voltage series branch, and sequentially connecting their low-voltage sides in series to form a low-voltage series branch. Under this structure, the bus voltage during steady-state operation is shared by the two power units. Since each power unit only bears a portion of the voltage on the high-voltage side port, this directly reduces the voltage stress on the switching devices in the internal bidirectional four-switch Buck-Boost circuit. Based on this series voltage division principle, the system can use power devices with relatively low withstand voltage ratings to replace traditional high-voltage devices, thereby effectively reducing the overall hardware cost and parasitic losses, while maintaining the compactness of the system structure without the need for an additional high-frequency isolation transformer. 2. Regarding the internal circuitry and parallel expansion scheme, the combination of high- and low-voltage side bridge arms and energy storage inductors, supplemented by supporting capacitors on both sides, provides the hardware foundation for bidirectional energy flow, enabling the system to have full-range buck, boost, and buck-boost functions. Based on this, an architecture of multiple sets of bidirectional four-switch Buck-Boost circuits connected in parallel is adopted, which can evenly distribute the total current to each parallel branch, significantly reducing the current load on the switching devices and inductors of a single branch, mitigating the risk of localized heat concentration, and improving operational reliability under heavy load conditions. Furthermore, the design of parallel branches sharing high- and low-voltage side supporting capacitors reduces the number of independent capacitors while ensuring current shunt capacity, further reducing the overall size. 3. Furthermore, by introducing a controller as the logic center, precise control of the switching transistor's on / off state is achieved by comparing the magnitude of the high-voltage bus voltage and the energy storage battery voltage. The controller outputs interleaved PWM modulated drive signals to each parallel circuit group, using phase difference to cancel out the ripple current generated by the independent inductors of each phase, thereby effectively suppressing the total current ripple at the bus end and reducing the filtering pressure. At the same time, the voltage equalization and current equalization control loops configured inside the system work together to dynamically adjust the duty cycle to correct the voltage difference between series units and suppress the current deviation between parallel branches, ensuring uniform distribution of voltage and current and limiting the switching transistor to not exceed its rated withstand voltage and rated current range; 4. Finally, based on the above structure, this application also formulates a complete control strategy for bidirectional energy transfer scenarios of charging and discharging. When the voltage relationship between the high and low voltage ports changes, the controller enables the converter to switch precisely and smoothly between Buck mode, Boost mode, or Buck-Boost mode, matching the corresponding energy conversion path, reducing unnecessary switching frequency, thereby reducing overall switching losses and meeting the needs of regenerative braking or bidirectional battery charging and discharging under actual operating conditions. Ultimately, this converter and its control method are applied to the powertrain system, establishing a physical channel between the high-voltage DC bus and the low-voltage battery, completing the practical application from the core circuit to the entire vehicle powertrain system. Attached Figure Description

[0017] Figure 1 A schematic diagram of the circuit structure of the series-type bidirectional DC / DC converter for high-voltage, high-power scenarios provided in this application; Figure 2 A circuit structure diagram illustrating another implementation of the series-type bidirectional DC / DC converter for high-voltage, high-power scenarios provided in this application. Detailed Implementation

[0018] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0020] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0021] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0022] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0024] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0025] First, let's explain the background of the technical problem: In high-voltage, high-power scenarios, such as the actual application of mining trucks, there are two significant background characteristics: First, the voltage of its high-voltage DC bus is extremely high, usually reaching the 2.4kV (2400V) level; second, because the on-board battery capacity of mining trucks is extremely large and the equipment operates for a long time, the system has extremely high requirements for charging and discharging efficiency (usually above 99%), because even a 1% difference in efficiency will result in a huge difference in electricity costs over the years.

[0026] Please see Figure 1 , Figure 1 This is a schematic diagram of the circuit structure of a series-type bidirectional DC / DC converter for high-voltage, high-power scenarios provided in this application.

[0027] This invention discloses a series-type bidirectional DC / DC converter for high-voltage, high-power applications, comprising: The high-voltage side port is used to connect to the high-voltage DC bus. The low-voltage side port is used to connect to the energy storage battery; The first power unit and the second power unit each contain at least one set of bidirectional four-switch Buck-Boost circuits. The high-voltage side of the first power unit and the high-voltage side of the second power unit are connected in series to form a high-voltage series branch, which is connected to both ends of the high-voltage side port. The low-voltage side of the first power unit and the low-voltage side of the second power unit are connected in series to form a low-voltage series branch, which is connected to both ends of the low-voltage side port. The first power unit and the second power unit are configured to: realize bidirectional buck, boost or buck-boost conversion between the high-voltage side port and the low-voltage side port under the drive of the controller; and during operation, the voltage of the high-voltage side port is shared by the first power unit and the second power unit, and the voltage of the low-voltage side port is shared by the first power unit and the second power unit.

[0028] This application provides a series-type bidirectional DC / DC converter for high-voltage, high-power scenarios. It constructs a cascaded architecture with two sides connected in series: the high-voltage sides of the first and second power units are connected in series to form a high-voltage series branch, and the low-voltage sides are connected in series to form a low-voltage series branch. In this structure, the bus voltage during steady-state operation is shared by the two power units (equivalent to halving the high voltage). Since each power unit only bears a portion of the voltage on the high-voltage side port, this directly reduces the voltage stress on the switching devices in the internal bidirectional four-switch Buck-Boost circuit. Based on this series voltage division principle, the system can use power devices with relatively low withstand voltage ratings (e.g., existing mature 1500V power devices from passenger vehicles can be directly reused) to replace traditional 3300V high-voltage devices, thereby effectively reducing the overall hardware cost and parasitic losses, while maintaining the system's compact structure without the need for an additional high-frequency isolation transformer.

[0029] Furthermore, existing power devices in passenger vehicles are typically designed to carry extremely high currents, while the actual operating current faced by this invention in high-voltage, high-power scenarios is relatively moderate (e.g., around 500A). Therefore, directly reusing passenger vehicle devices not only solves the voltage withstand problem but also creates an appropriate "over-design (redundant design)" in terms of current carrying capacity. This derating state with sufficient current margin further significantly reduces the conduction and switching losses of the devices during actual operation, thereby successfully improving the overall charging and discharging efficiency of the system to over 99%, perfectly meeting the commercial requirements for long-term, high-efficiency operation in high-voltage, high-power scenarios.

[0030] The above is an explanation of the basic concept of this application. The specific implementation methods of each structure will be explained below.

[0031] First, there are no restrictions on the specific implementation of the bidirectional four-switch Buck-Boost circuit.

[0032] In one possible implementation, the bidirectional four-switch Buck-Boost circuit specifically includes: The first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, and the energy storage inductor; The first and second switching transistors are connected in series to form a high-voltage side bridge arm, and a high-voltage side support capacitor is connected in parallel at both ends of the high-voltage side bridge arm; wherein, one end of the first switching transistor is connected to the positive terminal of the high-voltage side support capacitor, the other end of the first switching transistor is connected to one end of the second switching transistor, and the other end of the second switching transistor is connected to the negative terminal of the high-voltage side support capacitor. The fourth and third switches are connected in series to form a low-voltage side bridge arm, and low-voltage side support capacitors are connected in parallel at both ends of the low-voltage side bridge arm; wherein, one end of the fourth switch is connected to the positive terminal of the low-voltage side support capacitor, the other end of the fourth switch is connected to one end of the third switch, and the other end of the third switch is connected to the negative terminal of the low-voltage side support capacitor. The midpoint of the high-voltage side bridge arm is the connection point between the first and second switching transistors, and the midpoint of the low-voltage side bridge arm is the connection point between the fourth and third switching transistors. An energy storage inductor is connected between the midpoint of the high-voltage side bridge arm and the midpoint of the low-voltage side bridge arm.

[0033] This section further clarifies the specific physical connections of the bidirectional four-switch Buck-Boost circuits within the first and second power units. The first and second switches form the high-voltage side arm, while the fourth and third switches form the low-voltage side arm. An energy storage inductor is connected between the midpoints of the two arms. This structure, combined with the parallel high-voltage and low-voltage support capacitors at both ends, provides the hardware foundation for bidirectional energy flow. By controlling the on / off states of the switches on both arms, the inductor periodically stores and releases energy, thereby achieving full-range buck, boost, and buck-boost functions, while also accommodating the wide voltage gain range required by the converter.

[0034] Secondly, the specific structures of the first power unit and the second power unit are also not limited.

[0035] Please see Figure 2 , Figure 2 A circuit structure diagram illustrating another implementation of the series-type bidirectional DC / DC converter for high-voltage, high-power scenarios provided in this application.

[0036] like Figure 2 As shown, further, in one possible implementation, both the first power unit and the second power unit contain n sets of bidirectional four-switch Buck-Boost circuits connected in parallel; n≥2.

[0037] This can be understood as follows: based on a single-phase circuit structure, the first and second power units may also include multiple sets of bidirectional four-switch Buck-Boost circuits connected in parallel. This multi-phase parallel architecture essentially serves as a current shunting mechanism. When high-power energy exchange occurs between the high-voltage DC bus and the energy storage battery, the massive total current is evenly distributed across the parallel branches. In this way, the current load on the switching devices and energy storage inductors on a single branch is significantly reduced, mitigating the risk of localized heat concentration that is easily caused by a single-phase high-current architecture, dispersing the thermal load of the entire converter, and improving the system's operational reliability under heavy load conditions.

[0038] Those skilled in the art will understand that the number of bidirectional four-switch Buck-Boost circuits connected in parallel in the first power unit and the second power unit is not limited. For example, n = 3, 4, 5, 6, etc., and this application does not impose any limitation herein. Meanwhile, as... Figure 1 As shown, in another possible implementation, the first power unit and the second power unit may also include only a bidirectional four-switch Buck-Boost circuit. Those skilled in the art can configure it as needed, and this application does not impose any restrictions here.

[0039] Specifically, in one possible implementation, within the same power unit: n bidirectional four-switch Buck-Boost circuits share the high-voltage side support capacitor and the low-voltage side support capacitor. Furthermore, each bidirectional four-switch Buck-Boost circuit has its own independent high-voltage side bridge arm, low-voltage side bridge arm, and energy storage inductor.

[0040] By retaining independent bridge arms and inductors, each phase circuit can independently perform high-frequency switching operations, achieving independent control of multi-phase current; while the shared support capacitors on both sides open up the voltage nodes of each parallel branch. This design, while ensuring the multi-phase parallel current shunting capability, minimizes the number of independent support capacitors in the system, reduces the overall size of the converter, and makes the multi-phase topology more compact in physical implementation.

[0041] Furthermore, the series-type bidirectional DC / DC converter provided in this application may also include more structures to achieve more functions.

[0042] For example, in one possible implementation, the series-type bidirectional DC / DC converter also includes a controller; The controller is electrically connected to each switching transistor in the first and second power units. The controller is configured to control the switching transistors in each group of bidirectional four-switch Buck-Boost circuits to turn on, turn off, or switch at high frequency based on the relationship between the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port, so as to achieve bidirectional energy flow.

[0043] The controller acts as the logic hub, acquiring real-time data on the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port. By comparing the magnitudes of these two port voltages, the controller determines the operating state of the switching transistors in each bidirectional four-switch Buck-Boost circuit. This provides the system with a hardware-driven underlying logic, enabling the converter to automatically adapt to different operating modes according to actual conditions, ensuring smooth bidirectional energy flow between the bus and the battery.

[0044] Furthermore, in one possible implementation, the controller is configured to output interleaved PWM modulated drive signals to n sets of circuits connected in parallel within the same power unit, with the drive signals of adjacent sets of circuits having a phase difference of 360° / n.

[0045] Based on a multiphase parallel architecture, the controller outputs interleaved PWM modulated drive signals to n groups of circuits connected in parallel within the same power unit, while maintaining the phase difference between the drive signals of adjacent groups of circuits at a corresponding angle. By staggering the switching cycles of each phase circuit on the time axis, the ripple current generated by each phase's independent energy storage inductor cancels out the peaks and troughs when it converges to the shared high-voltage or low-voltage support capacitor. This interleaved modulation principle suppresses the total current ripple at the bus end and reduces the filtering pressure on the DC support capacitor.

[0046] It should be noted that the specific structure of the controller is also not limited.

[0047] In one possible implementation, the controller is internally configured with a pressure equalization control loop and a current equalization control loop; The voltage equalization control loop is used to dynamically adjust the duty cycle of the drive signal between the first power unit and the second power unit so that the high voltage side voltage shared by the two units remains equal. The current sharing control loop is used to dynamically adjust the duty cycle of the drive signals among the n bidirectional four-switch Buck-Boost circuits within the same power unit, so that the current shared by each circuit remains equal.

[0048] Due to parameter differences in actual physical devices, the voltage equalization control loop dynamically adjusts the duty cycle of the drive signals between the first and second power units to correct the voltage difference that may occur in the two-stage series architecture in real time. The current equalization control loop fine-tunes the duty cycle between the n parallel circuits to suppress current deviations between branches. These two closed-loop mechanisms work together to ensure uniform voltage distribution between series units and uniform current distribution between parallel branches, limiting the switching transistors to within their rated voltage and current ranges.

[0049] The above is a complete description of the implementation method of the series-type bidirectional DC / DC converter for high-voltage and high-power scenarios provided in this application.

[0050] Correspondingly, the second aspect of this application provides a control method for a series-type bidirectional DC / DC converter for high-voltage, high-power scenarios, used to control any of the aforementioned series-type bidirectional DC / DC converters. The control method includes: Obtain the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port; When the converter is in charging mode, transferring energy from the high-voltage side to the low-voltage side, the following control strategy is executed based on the relationship between the high-voltage bus voltage and the energy storage battery voltage: If the high-voltage bus voltage is greater than the energy storage battery voltage, the converter is controlled to operate in Buck mode: the fourth switch is always on, and the first and second switches are complementary in conduction. If the high-voltage bus voltage is less than the energy storage battery voltage, the converter is controlled to operate in Boost mode: the first switch is always on, and the third and fourth switches are complementary in conduction. If the high-voltage bus voltage is close to the energy storage battery voltage, the converter is controlled to operate in Buck-Boost mode: the first and third switches are turned on simultaneously, the second and fourth switches are turned on simultaneously, and they are complementary to the first and third switches in conduction.

[0051] This application also provides a control method for a series-type bidirectional DC / DC converter for high-voltage, high-power scenarios: when the high-voltage bus voltage is greater than, less than, or close to the energy storage battery voltage, the controller uses different switching transistor combinations to precisely switch the converter into Buck mode, Boost mode, or Buck-Boost mode. This strategy of automatically switching the normally conducting and complementary conducting states of the switching transistors based on the real-time voltage difference allows the converter to match the corresponding energy conversion path at different voltage platforms throughout the battery charging cycle, reducing unnecessary high-frequency switching transistor actions and thus lowering the overall switching losses of the system.

[0052] Furthermore, in one possible implementation, when the converter is in a discharge mode where energy is transferred from the low-voltage side to the high-voltage side, the control method further includes: If the high-voltage bus voltage is greater than the energy storage battery voltage, the converter is controlled to operate in Boost mode: the fourth switch is always on, and the second and first switches are complementary in conduction. If the high-voltage bus voltage is less than the energy storage battery voltage, the converter is controlled to operate in Buck mode: the first switch is always on, and the fourth and third switches are complementary in conduction. If the high-voltage bus voltage is close to the energy storage battery voltage, the control converter operates in Buck-Boost mode: the second and fourth switches are turned on simultaneously, the first and third switches are turned on simultaneously, and they are complementary to the second and fourth switches.

[0053] This solution supplements the discharge mode, which transfers energy from the low-voltage side to the high-voltage side, with reverse control logic. Corresponding to the charging mode, when the converter needs to feed energy from the energy storage battery back to the high-voltage DC bus, the controller also controls the converter to switch between Boost mode, Buck mode, or Buck-Boost mode based on the voltage relationship between the two ends. This approach allows the converter to maintain a wide voltage regulation capability even when supplying power in reverse, establishing a control link for bidirectional energy flow and meeting the needs of regenerative braking or reverse battery discharge under actual operating conditions.

[0054] A third aspect of this application provides a power system comprising: High-voltage DC bus; Onboard energy storage batteries; and A series bidirectional DC / DC converter for mining trucks, as described above; The high-voltage DC bus is connected to the high-voltage side port of the converter, and the on-board energy storage battery is connected to the low-voltage side port of the converter.

[0055] By applying the aforementioned series-type bidirectional DC / DC converter to the power system, connecting the high-voltage DC bus and the on-board energy storage battery respectively, this solution implements the previous topology and control strategy onto a specific industrial platform. It establishes a physical channel for energy interaction between the high-voltage bus and the low-voltage battery in high-voltage, high-power scenarios, completing the practical application from the core circuit to the entire vehicle power system.

[0056] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A series-type bidirectional DC / DC converter for high-voltage, high-power applications, characterized in that, include: The high-voltage side port is used to connect to the high-voltage DC bus. The low-voltage side port is used to connect to the energy storage battery; The first power unit and the second power unit each contain at least one set of bidirectional four-switch Buck-Boost circuits. The high-voltage side of the first power unit and the high-voltage side of the second power unit are connected in series to form a high-voltage series branch, which is connected to both ends of the high-voltage side port. The low-voltage side of the first power unit and the low-voltage side of the second power unit are connected in series to form a low-voltage series branch, which is connected to both ends of the low-voltage side port. The first power unit and the second power unit are configured to: realize bidirectional buck, boost, or buck-boost conversion between the high-voltage side port and the low-voltage side port under the drive of the controller; and during operation, the voltage of the high-voltage side port is shared by the first power unit and the second power unit, and the voltage of the low-voltage side port is shared by the first power unit and the second power unit.

2. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 1, characterized in that, The bidirectional four-switch Buck-Boost circuit specifically includes: The first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, and the energy storage inductor; The first switch and the second switch are connected in series to form a high-voltage side bridge arm, and a high-voltage side support capacitor is connected in parallel at both ends of the high-voltage side bridge arm; wherein, one end of the first switch is connected to the positive terminal of the high-voltage side support capacitor, the other end of the first switch is connected to one end of the second switch, and the other end of the second switch is connected to the negative terminal of the high-voltage side support capacitor; The fourth switch and the third switch are connected in series to form a low-voltage side bridge arm, and a low-voltage side support capacitor is connected in parallel at both ends of the low-voltage side bridge arm; wherein, one end of the fourth switch is connected to the positive terminal of the low-voltage side support capacitor, the other end of the fourth switch is connected to one end of the third switch, and the other end of the third switch is connected to the negative terminal of the low-voltage side support capacitor. The midpoint of the high-voltage side bridge arm is the connection point between the first switch tube and the second switch tube, and the midpoint of the low-voltage side bridge arm is the connection point between the fourth switch tube and the third switch tube. The energy storage inductor is connected between the midpoint of the high-voltage side bridge arm and the midpoint of the low-voltage side bridge arm.

3. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 2, characterized in that: Both the first power unit and the second power unit contain n sets of the bidirectional four-switch Buck-Boost circuits connected in parallel; n≥2.

4. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 3, characterized in that, Within the same power unit: The n groups of bidirectional four-switch Buck-Boost circuits share the high-voltage side support capacitor and the low-voltage side support capacitor. Furthermore, each of the bidirectional four-switch Buck-Boost circuits has its own independent high-voltage side bridge arm, low-voltage side bridge arm, and energy storage inductor.

5. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 4, characterized in that, The series-type bidirectional DC / DC converter also includes a controller; The controller is electrically connected to each switching transistor in the first power unit and the second power unit. The controller is configured to control the switching transistors in each group of bidirectional four-switch Buck-Boost circuits to turn on, turn off, or switch at high frequency according to the relationship between the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port, so as to realize bidirectional energy flow.

6. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 5, characterized in that, The controller is configured to output interleaved PWM modulation drive signals to the n groups of circuits connected in parallel within the same power unit, wherein the drive signals of adjacent groups of circuits are 360° / n out of phase.

7. The series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 6, characterized in that, The controller is internally configured with a pressure equalization control loop and a current equalization control loop; The voltage equalization control loop is used to dynamically adjust the duty cycle of the drive signal between the first power unit and the second power unit so that the high voltage side voltage shared by the two units remains equal. The current sharing control loop is used to dynamically adjust the duty cycle of the drive signals among the n groups of bidirectional four-switch Buck-Boost circuits within the same power unit, so that the current shared by each group of circuits remains equal.

8. A control method for a series-type bidirectional DC / DC converter for high-voltage, high-power applications, characterized in that, The control method for controlling the series-type bidirectional DC / DC converter according to any one of claims 2-7 includes: Obtain the high-voltage bus voltage at the high-voltage side port and the energy storage battery voltage at the low-voltage side port; When the converter is in charging mode, transferring energy from the high-voltage side to the low-voltage side, the following control strategy is executed based on the relationship between the high-voltage bus voltage and the energy storage battery voltage: If the high-voltage bus voltage is greater than the energy storage battery voltage, the converter is controlled to operate in Buck mode: the fourth switch is always on, and the first and second switches are complementary in conduction. If the high-voltage bus voltage is less than the energy storage battery voltage, the converter is controlled to operate in Boost mode: the first switch is always on, and the third and fourth switches are complementary in conduction; If the high-voltage bus voltage is close to the energy storage battery voltage, the converter is controlled to operate in Buck-Boost mode: the first switch and the third switch are turned on simultaneously, the second switch and the fourth switch are turned on simultaneously, and they are complementary to the first switch and the third switch.

9. The control method for a series-type bidirectional DC / DC converter for high-voltage, high-power scenarios as described in claim 8, characterized in that, When the converter is in a discharge mode that transfers energy from the low-voltage side to the high-voltage side, the control method further includes: If the high-voltage bus voltage is greater than the energy storage battery voltage, the converter is controlled to operate in Boost mode: the fourth switch is always on, and the second switch and the first switch are complementary in conduction. If the high-voltage bus voltage is less than the energy storage battery voltage, the converter is controlled to operate in Buck mode: the first switch is always on, and the fourth switch and the third switch are complementary in conduction; If the high-voltage bus voltage is close to the energy storage battery voltage, the converter is controlled to operate in Buck-Boost mode: the second switch and the fourth switch are turned on simultaneously, the first switch and the third switch are turned on simultaneously, and they are complementary to the second switch and the fourth switch.

10. A power system, characterized in that, include: High-voltage DC bus; Onboard energy storage batteries; as well as A series bidirectional DC / DC converter for high-voltage, high-power scenarios as described in any one of claims 1-7; The high-voltage DC bus is connected to the high-voltage side port of the converter, and the vehicle-mounted energy storage battery is connected to the low-voltage side port of the converter.

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