A DAB bidirectional dual active bridge system suitable for high-power pure electric mine truck

Abstract

The utility model discloses a kind of DAB bidirectional double active bridge systems suitable for high-power pure electric mine truck, the system includes pre-charging loop, voltage acquisition circuit, DAB power conversion circuit and LC resonant circuit;The LC resonant circuit is composed of resonant inductance and resonant capacitor in series, is connected between the first H bridge circuit AC side and the primary side of isolation transformer, and controller controls energy bidirectional transmission by adjusting the phase shift angle between two H bridges;The utility model realizes soft switch of full load range by resonant unit, effectively reduces switching loss, improves efficiency;Symmetrical topology and electrical isolation guarantee system safety and reliability, solve the problem that traditional converter low load efficiency, regulation range is narrow and control is complex, especially suitable for energy balance and range extension between mine truck battery pack.

Description

Technical Field

[0001] This utility model relates to a DAB bidirectional dual active bridge system, and more particularly to a DAB bidirectional dual active bridge system suitable for high-power pure electric mining trucks. Background Technology

[0002] With the widespread application of new energy technologies in the heavy machinery sector, high-power pure electric mining trucks have become an important development direction. These vehicles are typically equipped with multiple large-capacity battery packs to provide driving energy. In actual operation, due to differences in cell characteristics, operating temperature, and load, an imbalance in the state of charge (SOC) can occur between battery packs. If this imbalance is not effectively managed, it will accelerate battery performance degradation, shorten the vehicle's driving range, and introduce safety risks. Currently, the mainstream solution for achieving electrical isolation and bidirectional energy transfer is the isolated bidirectional DC-DC converter. Among them, the dual active bridge (DAB) converter is a recognized advanced topology. Existing technical solutions typically employ a full-bridge phase-shifted DC-DC converter consisting of two full-bridge circuits and a high-frequency transformer; its basic working principle is to adjust the magnitude and direction of transmitted power by controlling the phase shift angle between the primary and secondary full-bridge switches. Existing control strategies mainly include single-phase-shift control (SPS) and extended-phase-shift control (EPS), aiming to achieve soft switching of the switches (such as zero-voltage switching, ZVS) to reduce losses and improve efficiency.

[0003] However, existing traditional DAB converters and their control strategies still have significant shortcomings when applied to complex industrial scenarios such as mining trucks. First, under light load conditions, insufficient loop energy makes it difficult for the hysteresis arm switch of the converter to achieve zero-voltage switching (ZVS), leading to a significant increase in switching losses and a sharp drop in efficiency. Second, due to factors such as the resonant inductor, there is a problem of secondary-side duty cycle loss, limiting the output voltage adjustment range and affecting system performance. Finally, to maintain system stability, the control circuit design is complex, requiring highly precise feedback and regulation mechanisms, which increases system cost and reduces reliability. These problems result in large efficiency fluctuations and slow dynamic response speeds in traditional solutions over a wide load range, making it difficult to meet the high performance and high reliability requirements of mining trucks under harsh operating conditions. Summary of the Invention

[0004] Purpose of the utility model: The purpose of this utility model is to provide a DAB bidirectional dual active bridge system suitable for high-power pure electric mining trucks to solve the problem of low efficiency under light load, broaden the power adjustment range and improve stability, and is suitable for engineering machinery scenarios such as high-power pure electric mining trucks.

[0005] Technical solution: The DAB bidirectional dual active bridge system of this utility model includes: A pre-charging circuit, comprising a main contactor connected in parallel and a branch consisting of a pre-charging contactor and a pre-charging resistor connected in series. A voltage acquisition circuit is configured to acquire voltage signals at the input and output terminals of the pre-charge circuit. The DAB power conversion circuit includes a first H-bridge circuit and a second H-bridge circuit arranged symmetrically, and the first H-bridge circuit and the second H-bridge circuit are connected through an isolation transformer. The primary winding and secondary winding of the isolation transformer are respectively connected to the AC side of the first H-bridge circuit and the second H-bridge circuit; An LC resonant circuit includes a resonant inductor and a resonant capacitor, wherein the resonant inductor and the resonant capacitor are connected in series between the AC side of the first H-bridge circuit and the primary winding of the isolation transformer.

[0006] Preferably, it also includes a busbar support capacitor and a discharge resistor connected in parallel between the positive and negative busbars.

[0007] Preferably, it also includes a current sensor connected in series with the positive busbar for collecting busbar current.

[0008] Preferably, both the first H-bridge circuit and the second H-bridge circuit are composed of four IGBT switching transistors.

[0009] Preferably, it also includes a high-voltage signal indicator light, which is connected to a key measuring point on the busbar and is used to indicate the high-voltage status of the system.

[0010] Preferably, the turns ratio of the isolation transformer is 1:1.

[0011] Preferably, the isolation transformer can be replaced with a Buck-Boost integrated three-terminal converter or a CLLC resonant converter.

[0012] Beneficial Effects: Compared with existing technologies, this utility model has the following advantages: 1. Through the symmetrical H-bridge topology, it ensures that the converter can achieve soft switching (ZVS) across the entire load range, including light loads, significantly reducing switching losses, improving overall system efficiency, and solving the problem of low efficiency under light loads; 2. By combining the resonant unit with the symmetrical H-bridge topology, it improves the performance bottleneck of traditional DABs at the hardware level, achieving advantages such as high efficiency, wide range, high reliability, and simplified control, reducing dependence on complex control algorithms, simplifying control logic, improving the dynamic response speed and reliability of the system, and making it more adaptable to the harsh working conditions of mining trucks; 3. By improving the problem of limited output voltage regulation range caused by duty cycle loss in traditional solutions, it ensures that the system can operate stably and efficiently under wide voltage and wide load conditions; 4. Electrical isolation is achieved through the isolation transformer, increasing the safety and reliability of the system. At the same time, through the optimization of the control strategy, energy input and output are more flexible, adapting to the needs of various application scenarios; 5. It provides a solution for efficient and reliable bidirectional energy transmission for the two battery packs of mining trucks, effectively completing the power battery imbalance adjustment and range extension functions, while ensuring electrical isolation safety. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0014] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0015] Example 1 like Figure 1 As shown in the figure, this embodiment provides a DAB bidirectional dual active bridge system suitable for high-power pure electric mining trucks. It is mainly used to realize bidirectional energy transfer between two battery packs in order to achieve the purpose of balancing power (power battery imbalance adjustment) or extending range.

[0016] The system mainly includes: a pre-charging circuit, a voltage acquisition circuit, an LC resonant circuit, and a DAB power conversion circuit.

[0017] The pre-charge circuit (component 1) includes a main contactor connected in parallel and a branch consisting of a pre-charge contactor and a pre-charge resistor connected in series. The pre-charge circuit is connected to the positive output bus of the first battery pack. Specifically, the main contactor (KM1), pre-charge contactor (KM2), and pre-charge resistor (R1) are connected in parallel and then in series within the bus. When the system is powered on, the controller first controls the pre-charge contactor (KM2) to close, and current slowly charges the subsequent bus support capacitors (C1, C2) through the pre-charge resistor (R1). When the capacitor voltage is detected to be close to the battery voltage, the controller then controls the main contactor (KM1) to close, while simultaneously opening the pre-charge contactor (KM2), completing the safe power-on process. The contactor status signals are fed back to the controller for status monitoring and fault diagnosis.

[0018] The voltage acquisition circuit (component 2) is configured to acquire the voltage signals at the input and output terminals of the pre-charge loop. Using components such as voltage divider resistors, the voltage acquisition circuit measures the voltage signals at the input and output terminals of the pre-charge loop, providing voltage feedback for closed-loop control of the controller. It consists of circuits HV-1 and HV+1, HV-2 and HV+2, HV-3 and HV+3, and HV+4 and HV-4.

[0019] The DAB power conversion circuit (component 6) has a symmetrical topology and uses a full-bridge (H-bridge) circuit. It includes a symmetrically arranged first H-bridge circuit and a second H-bridge circuit, connected by an isolation transformer.

[0020] The first H-bridge circuit consists of four IGBT switches (VQ1, VQ2, VQ3, VQ4), forming a standard full-bridge inverter circuit that inverts the DC power from the first battery pack side into a high-frequency AC square wave. The second H-bridge circuit has the same structure as the first H-bridge circuit, consisting of switches (VQ5, VQ6, VQ7, VQ8), and its function is rectification, restoring the high-frequency AC square wave to DC power to supply the second battery pack.

[0021] The primary and secondary windings of the isolation transformer (component 9) are connected to the AC sides of the first H-bridge circuit and the second H-bridge circuit, respectively. Its turns ratio is designed to be 1:1. Its main function is to achieve electrical isolation between the first and second battery packs, prevent grounding interference and leakage risks, and improve system safety. It also plays a role in energy transfer and voltage transformation.

[0022] The LC resonant circuit (component 8) includes a resonant inductor Lr and a resonant capacitor Cr (component 7). The resonant inductor and resonant capacitor are connected in series between the AC side of the first H-bridge circuit and the primary winding of the isolation transformer (T1). This LC resonant circuit is the key to achieving soft switching in this embodiment. It makes the current flowing through the switching transistor sinusoidal or quasi-sinusoidal, creating the condition for current or voltage to cross zero, enabling the switching transistor to operate at zero voltage (ZVS) or zero current (ZCS), thereby greatly reducing switching losses and electromagnetic interference.

[0023] TA1 and TA2 are current sensors (component 4), connected in series on the positive terminals of the two busbars. They collect the input current and transmit the signal to the controller to achieve precise current closed-loop control and safety protection.

[0024] HO1+ and HO2+ are high-voltage signal indicator lights (component 3), connected to key measuring points, used to visually indicate whether the system is in a live state, providing safety warnings to on-site operators.

[0025] The bus support capacitors (C1, C2) are electrolytic or film capacitors connected in parallel between the bus and ground. Their main function is to filter out high-frequency ripple of the bus voltage, absorb noise generated by the operation of switching devices, and provide local energy buffering for high-frequency conversion. Discharge resistors (R2 and R3, component 5) are connected in parallel with the bus support capacitors. When the system stops, the controller can control the discharge circuit or enable the discharge path through the drive circuit, allowing the electrical energy stored in the capacitors to be quickly consumed through the discharge resistors, ensuring that the bus voltage drops rapidly to a safe level and protecting the safety of maintenance personnel. Working principle: Suppose that energy needs to be transferred from the first battery pack to the second battery pack, the controller (such as a DSP) sends a PWM drive signal to control the four switches of the first H-bridge circuit to operate in a 50% duty cycle, 180° complementary conduction mode, inverting its DC input into a high-frequency AC square wave with an amplitude equal to the voltage of the first battery pack. After passing through the resonant inductor (Lr) and resonant capacitor (Cr), the waveform of this square wave is optimized, and then applied to the primary side of the high-frequency transformer (T1).

[0026] Energy is coupled to the secondary side through a transformer. The controller adjusts the power by controlling the phase shift angle between the four switches of the second H-bridge circuit and their corresponding switches in the first H-bridge circuit. Specifically, the switching timing of the second H-bridge circuit has a controllable phase delay relative to the first H-bridge circuit, and this phase shift angle determines the magnitude and direction of the transmitted power; the larger the phase shift angle, the greater the transmitted power.

[0027] When energy needs to flow in the reverse direction (from the second battery pack to the first battery pack), the controller only needs to change the sign of the phase shift angle, making the control logic simple and symmetrical.

[0028] The beneficial effects of this embodiment are as follows: By introducing an LC resonant circuit, the system successfully achieves zero-switching (ZVS) across the entire load range, remaining effective even under light load conditions. This addresses the low efficiency of traditional DAB circuits under light loads, achieving an overall efficiency that can be stabilized at 98% or even 99%. The symmetrical H-bridge topology, combined with optimized resonant parameters, improves duty cycle loss and broadens the voltage adaptation range. Simultaneously, this hardware foundation reduces reliance on complex control algorithms, resulting in faster system response and higher reliability, making it highly suitable for high-power, all-electric mining cards operating under complex conditions and requiring high reliability.

[0029] Example 2: This embodiment provides a supplementary explanation of the control method of the system described in Embodiment 1.

[0030] The controller executes the following control flow: The system acquires real-time information on the voltage (SOC indication), bus current, and temperature of both battery packs. Based on instructions from the vehicle controller or the built-in battery management strategy, it determines whether energy transfer is needed, and the direction and magnitude of the transfer. A single-phase-shift control (SPS) algorithm is employed. Based on the target transfer power P*, the corresponding phase shift angle is generated by querying a preset "power-phase-shift angle" mapping table or through online calculation. Using the switching timing of the first H-bridge circuit as a reference, the switching timing of the second H-bridge circuit is shifted by the phase shift angle to generate a corresponding PWM drive signal. After amplification by the drive circuit, this signal controls the on / off state of each IGBT.

[0031] The system continuously compares the actual transmitted power with the target power and dynamically fine-tunes the phase shift angle to achieve closed-loop control. Simultaneously, it continuously monitors the system status; if faults such as overcurrent, overvoltage, or overheating occur, it immediately enters protection mode, shuts down the PWM output, disconnects the contactor, and reports the fault information.

Claims

1. A DAB bidirectional dual active bridge system suitable for high-power pure electric mining trucks, characterized in that, include: A pre-charging circuit, comprising a main contactor connected in parallel and a branch consisting of a pre-charging contactor and a pre-charging resistor connected in series. A voltage acquisition circuit is configured to acquire voltage signals at the input and output terminals of the pre-charge circuit. The DAB power conversion circuit includes a first H-bridge circuit and a second H-bridge circuit arranged symmetrically, and the first H-bridge circuit and the second H-bridge circuit are connected through an isolation transformer. The primary winding and secondary winding of the isolation transformer are respectively connected to the AC side of the first H-bridge circuit and the second H-bridge circuit; An LC resonant circuit includes a resonant inductor and a resonant capacitor, wherein the resonant inductor and the resonant capacitor are connected in series between the AC side of the first H-bridge circuit and the primary winding of the isolation transformer.

2. The DAB bidirectional dual active bridge system according to claim 1, characterized in that, It also includes bus support capacitors and discharge resistors connected in parallel between the positive and negative busbars.

3. The DAB bidirectional dual active bridge system according to claim 1, characterized in that, It also includes a current sensor connected in series with the positive bus.

4. The DAB bidirectional dual active bridge system according to claim 1, characterized in that, Both the first H-bridge circuit and the second H-bridge circuit consist of four IGBT switching transistors.

5. The DAB bidirectional dual active bridge system according to claim 1, characterized in that, It also includes a high-voltage signal indicator light, which is connected to a key measuring point on the busbar.

6. The DAB bidirectional dual active bridge system according to claim 1, characterized in that, The turns ratio of the isolation transformer is 1:

1.

7. The DAB bidirectional dual active bridge system according to claim 1, characterized in that, The isolation transformer can be replaced with a Buck-Boost integrated three-terminal converter or a CLLC resonant converter.

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