High-voltage electrical system of dual-power battery and charging and discharging method

Abstract

The invention discloses a high-voltage electrical system of a dual-power battery and a charging and discharging method. The first power battery is connected with the motor through a first switch group; the second power battery is connected with the motor through a second switch group; the bidirectional direct-current converter is located between the first switch group and the first power battery and connected to the first power battery in parallel, and the forward target output voltage of the bidirectional direct-current converter is set as the sampling voltage of the second power battery; when the first switch group is switched on and the second switch group is switched off, the first power battery independently supplies power to the motor through the bidirectional direct-current converter, and the bidirectional direct-current converter outputs forward power; and when the forward output voltage of the bidirectional DC converter is stabilized at the target output voltage, the first switch group and the second switch group are closed, and the first power battery and the second power battery supply power to the motor at the same time. Through the boost or buck mode of the bidirectional DC converter, the motor input voltage is balanced, the heat loss is reduced, and the energy utilization rate is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicles, in particular to a high-voltage electrical system of a dual-power battery and a charging and discharging method. BACKGROUND

[0002] With the wide application of unmanned vehicles, the types of unmanned vehicles are increasingly diverse, covering unmanned shuttle vehicles, unmanned delivery vehicles, unmanned express vehicles, unmanned medical vehicles and other types. In order to reduce the research and development cost, these vehicles usually adopt a combination of a general chassis and a personalized cabin. Since there are many components arranged on the chassis and the space is relatively compact, and the cabin needs to be independently operated and powered, a scheme of arranging one power battery on the chassis and one power battery on the cabin is usually adopted. However, after the two power batteries work separately for a period of time, if they are combined for use, the voltage of the two power batteries may not be consistent: one battery has a higher voltage, and the other battery has a lower voltage. If the two batteries are directly connected in parallel at this time, since the internal resistance of the power battery is small (usually only a few tens of milliohms), even if the voltage difference between the two batteries is only a few tens of volts, the current generated when the high-voltage battery charges the low-voltage battery can be as high as thousands of amperes. Such a large current not only causes serious safety hazards, but also can cause the battery to overheat or even explode, endangering the safety of the vehicle and personnel.

[0003] Currently, some power battery combination systems adopt a priority discharging strategy. The basic principle is to let the battery with a higher voltage supply power to the motor first, until the voltage difference between the two power batteries is reduced to within a preset range, and then the two batteries are connected in parallel for use. However, when the voltage difference between the two power batteries is outside the preset range, only one power battery supplies power to the motor, which limits the input power and still causes safety hazards due to the voltage difference between the two power batteries.

[0004] Some other power battery combination systems adopt a discharging equalization strategy. The basic principle is to consume the excess power in the battery with a higher voltage through a discharging resistor until the voltages of the two power batteries are equal, and then connect the two batteries in parallel for use. Although this method can solve the voltage difference problem of the two power batteries, it has many disadvantages. If a high-resistance small-power resistor is used for discharging, the discharging current is small and the equalization time is long; if a low-resistance high-power resistor is used for discharging, the resistor is large in size and expensive, and a special cooling device needs to be provided, which greatly increases the cost. In addition, no matter which resistor is used, the excess power in the battery with a higher voltage will be consumed in the form of heat on the resistor, reducing the energy utilization rate. SUMMARY

[0005] The present application provides a high-voltage electrical system of a dual-power battery and a charging and discharging method, which can solve the technical problem of low energy utilization rate in the current power battery combination technology.

[0006] To achieve the above object, in a first aspect, the application provides a high-voltage electrical system of a dual-power battery, comprising: a motor.

[0007] a first power battery connected to the motor through a first switch group.

[0008] a second power battery connected to the motor through a second switch group.

[0009] a bidirectional DC converter arranged in parallel with the first power battery between the first switch group and the first power battery, and a forward target output voltage of the bidirectional DC converter being set as a sampling voltage of the second power battery.

[0010] When the first switch group is closed and the second switch group is opened, the first power battery supplies power to the motor through the bidirectional DC converter, and the bidirectional DC converter outputs power in a forward direction.

[0011] When the forward output voltage of the bidirectional DC converter is stabilized at the target output voltage, the first switch group and the second switch group are closed, and the first power battery and the second power battery supply power to the motor at the same time.

[0012] Further, in an embodiment, the first power battery has a BMS1, the second power battery has a BMS2, the bidirectional DC converter and the motor each have a control unit, and the BMS1, the BMS2 and the control unit are connected to a vehicle controller through a CAN network.

[0013] In a second aspect, the application provides a charging method of a dual-power battery, comprising: obtaining a sampling voltage of a second power battery.

[0014] setting a forward target output voltage value of a bidirectional DC converter as the sampling voltage of the second power battery, wherein the bidirectional DC converter is arranged in parallel with a first power battery.

[0015] only using the first power battery to supply power to the motor through the bidirectional DC converter, and the bidirectional DC converter outputs power in a forward direction.

[0016] When the forward output voltage of the bidirectional DC converter is stabilized at the target output voltage, using the first power battery and the second power battery to supply power to the motor at the same time.

[0017] Further, in an embodiment, the bidirectional DC converter obtains the sampling voltage of the second power battery through a CAN network, and a vehicle controller sends an instruction to control the bidirectional DC converter to output power in a forward direction.

[0018] Further, in an embodiment, the sampling voltage of the first power battery is obtained, and when the bidirectional DC converter outputs power in a forward direction: If the sampling voltage of the first power battery is higher than the sampling voltage of the second power battery, the bidirectional DC converter works in a forward buck state at this time.

[0019] If the sampling voltage of the first power battery is lower than the sampling voltage of the second power battery, the bidirectional DC converter works in a forward boost state at this time.

[0020] Further, in an embodiment, the sampling voltage of the second power battery is obtained in real time, and the bidirectional DC converter is controlled in real time to adjust the output voltage of the bidirectional DC converter to follow the sampling voltage of the second power battery.

[0021] Further, in an embodiment, if the sampling voltage of the first power battery is lower than a normal working threshold value, the first power battery stops supplying power to the motor, and the second power battery alone supplies power to the motor.

[0022] Further, in an embodiment, if the sampling voltage of the second power battery is lower than a normal working threshold value, the second power battery stops supplying power to the motor, the bidirectional DC converter outputs power in a forward direction, the input voltage and the output voltage are equal, and the first power battery alone supplies power to the motor.

[0023] In a third aspect, the application provides a discharging method of double power batteries, the discharging method comprising: When the vehicle is in a braking state, the sampling voltage of the first power battery and the output voltage of the motor are obtained.

[0024] The reverse target output voltage value of the bidirectional DC converter is set as the sum of the sampling voltage of the first power battery and a preset voltage increase.

[0025] The motor directly charges the second power battery through a constant current charging mode.

[0026] When the reverse output voltage of the bidirectional DC converter is stabilized at the target output voltage, the bidirectional DC converter outputs power in a reverse direction, and the motor charges the first power battery and the second power battery.

[0027] Further, in an embodiment, the sampling voltage of the first power battery and the output voltage of the motor are obtained, and when the bidirectional DC converter outputs power in a reverse direction: If the output voltage of the motor is higher than the sum of the sampling voltage of the first power battery and a preset voltage increase, the bidirectional DC converter works in a reverse buck state at this time.

[0028] If the output voltage of the motor is lower than the sum of the sampling voltage of the first power battery and a preset voltage increase, the bidirectional DC converter works in a reverse boost state at this time.

[0029] The beneficial effects brought by the technical solutions provided by the embodiments of the present application include: The bidirectional DC converter of the present application is located between the first switch group and the first power battery, and is connected in parallel with the first power battery. The forward target output voltage of the bidirectional DC converter is set as the sampling voltage of the second power battery. When the first switch group is closed and the second switch group is disconnected, the first power battery supplies power to the motor alone through the bidirectional DC converter, and the bidirectional DC converter outputs power in the forward direction. When the forward output voltage of the bidirectional DC converter stabilizes at the target output voltage, the first switch group and the second switch group are closed, and the first power battery and the second power battery supply power to the motor at the same time. By connecting the bidirectional DC converter between one power battery and the motor, when the two power batteries are used in combination to charge the motor, the bidirectional DC converter realizes the balance of the input voltage at the motor end through the boost or buck function. The bidirectional DC converter controls the size of the output voltage by adjusting the duty cycle of its switch, which can significantly reduce the loss of electrical energy in the form of heat energy and improve the energy utilization rate. In addition, the boost and buck process of the bidirectional DC converter is completed in microseconds, which can reduce the time of voltage balance and also avoid the use of additional heat dissipation equipment, reducing the cost of the equipment. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The structure diagram of the high-voltage electrical system of the dual power battery of the embodiments of the present application.

[0031] Figure 2 The flowchart of the charging method of the dual power battery of the embodiments of the present application.

[0032] Figure 3 The flowchart of the discharging method of the dual power battery of the embodiments of the present application. DETAILED DESCRIPTION

[0033] In order to enable personnel in the technical field to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0034] First, some technical terms in the present application are explained and described in order to facilitate the understanding of the present application by those skilled in the art.

[0035] Bidirectional DC converter: a high-efficiency power conversion device that can achieve bidirectional DC power transmission, with characteristics of high efficiency, energy saving, economy, practicality, etc. Its working principle is based on switching power supply technology, which adjusts the input and output voltage by controlling the on-off time of the switch. The basic structure of the bidirectional DC converter includes a control circuit, a capacitor inductor group, a bidirectional switch and a DC bus. During transmission, the direction and size of the current on the DC bus can be controlled.

[0036] In order to make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be described in further detail below with reference to the drawings.

[0037] In a first aspect, the embodiments of the present application provide a high-voltage electrical system of a dual-power battery.

[0038] In an embodiment, referring to Figure 1 The high-voltage electrical system includes a motor, a first power battery, a second power battery, and a bidirectional DC converter.

[0039] The first power battery is connected to the motor through a first switch group. In this embodiment, the first switch group includes two switches K1 and K2, which are respectively arranged on the branch connected to the positive and negative poles of the first power battery.

[0040] The second power battery is connected to the motor through a second switch group. In this embodiment, the second switch group includes two switches K3 and K4, which are respectively arranged on the branch connected to the positive and negative poles of the second power battery.

[0041] The bidirectional DC converter is located between the first switch group and the first power battery, and is connected in parallel to the first power battery. The forward target output voltage of the bidirectional DC converter is set as the sampling voltage of the second power battery.

[0042] When the first switch group is closed (i.e. K1 and K2 are closed) and the second switch group is open (i.e. K3 and K4 are open), the first power battery supplies power to the motor through the bidirectional DC converter, and the bidirectional DC converter outputs power in the forward direction.

[0043] When the forward output voltage of the bidirectional DC converter stabilizes at the target output voltage, the first switch group and the second switch group are closed (i.e. K1, K2, K3 and K4 are all closed), and the first power battery and the second power battery supply power to the motor at the same time.

[0044] In this embodiment, a bidirectional DC converter is connected between the first power battery and the motor. When the two power batteries are used in combination to charge the motor, the bidirectional DC converter completes voltage boosting or voltage dropping at a microsecond level to balance the input voltage of the motor. The bidirectional DC converter can realize voltage balancing by precisely adjusting the switching duty cycle of the bidirectional DC converter, greatly reducing heat loss and improving energy utilization. At the same time, the additional heat dissipation device is saved, which reduces the cost and shortens the balancing time.

[0045] Further, in an embodiment, referring to FIG. 1, the first power battery has a BMS (Battery Management System) 1, the second power battery has a BMS 2, the bidirectional DC converter and the motor each have a control unit, and the BMS 1, the BMS 2 and the control unit are connected to a vehicle controller through a CAN network. Figure 1

[0046] Further, in an embodiment, a specific application method for charging the motor based on the high-voltage electrical system is provided. The specific steps of the charging method are as follows: The first control unit of the motor sends a charging signal to the vehicle controller through the CAN network.

[0047] After receiving the charging signal, the vehicle controller sends a forward command to the second control unit of the bidirectional DC converter through the CAN network to set the bidirectional DC converter to a forward working state.

[0048] The BMS 1 of the first power battery and the BMS 2 of the second power battery send a first sampling voltage of the first power battery and a second sampling voltage of the second power battery to the second control unit of the bidirectional DC converter through the CAN network, and the bidirectional DC converter sets the second sampling voltage as a target output voltage.

[0049] K1 and K2 are closed, and K3 and K4 are disconnected, so that the first power battery charges the motor through the bidirectional DC converter. The bidirectional DC converter outputs power in a forward direction, and the second control unit of the bidirectional DC converter controls the voltage conversion state of the bidirectional DC converter according to the size relationship between the first sampling voltage and the second sampling voltage. Specifically: When the first sampling voltage is higher than the second sampling voltage, the bidirectional DC converter works in a forward voltage dropping state, and the forward output voltage of the bidirectional DC converter is lower than the first sampling voltage.

[0050] When the first sampling voltage is lower than the second sampling voltage, the bidirectional DC converter works in a forward voltage boosting state, and the forward output voltage of the bidirectional DC converter is higher than the first sampling voltage.

[0051] ​When the forward output voltage of the bidirectional DC converter is equal to the target output voltage, K1, K2, K3, and K4 are closed, and the first power battery and the second power battery jointly charge the motor.

[0052] Further, in an embodiment, a specific application method for discharging the motor based on the high-voltage electrical system is provided, and the specific steps of the discharging method are as follows: The first control unit of the motor sends a discharging signal to the vehicle controller through the CAN network.

[0053] After receiving the discharging signal, the vehicle controller sends a reverse command to the second control unit of the bidirectional DC converter through the CAN network, and sets the bidirectional DC converter to a reverse working state.

[0054] The BMS of the first power battery sends the first sampling voltage of the first power battery to the second control unit of the bidirectional DC converter through the CAN network, and the first control unit of the motor sends the output voltage of the motor to the second control unit of the bidirectional DC converter through the CAN network, and the bidirectional DC converter sets the sum of the first sampling voltage and the preset voltage increment as the target output voltage.

[0055] K3 and K4 are closed, and K1 and K2 are opened, and the motor directly charges the second power battery in a constant current charging mode, and at the same time, the second control unit of the bidirectional DC converter controls the voltage conversion state of the bidirectional DC converter according to the size relationship between the sum of the first sampling voltage and the preset voltage increment and the output voltage of the motor, and specifically: When the output voltage of the motor is higher than the sum of the first sampling voltage and the preset voltage increment, the bidirectional DC converter works in a reverse buck state, and at this time, its reverse output voltage is lower than the output voltage of the motor.

[0056] When the output voltage of the motor is lower than the sum of the first sampling voltage and the preset voltage increment, the bidirectional DC converter works in a reverse boost state, and at this time, its reverse output voltage is higher than the output voltage of the motor.

[0057] When the reverse output voltage of the bidirectional DC converter is equal to the target output voltage, K1, K2, K3, and K4 are closed, and the motor simultaneously charges the first power battery and the second power battery.

[0058] In this embodiment, if the sampling voltage of the first power battery is directly used as the reverse target output voltage, the charging voltage may be insufficient due to actual voltage fluctuations or line loss and other factors, thereby affecting the charging efficiency. The voltage increment can provide a safety margin to ensure that the output voltage of the bidirectional DC converter is always higher than the sampling voltage of the first power battery, thereby ensuring the reliability and stability of the charging process.

[0059] In a second aspect, the embodiments of the present application provide a charging method of a dual-power battery.

[0060] In an embodiment, referring to Figure 2 The charging method comprises the following steps: S1, obtaining a sampling voltage of the second power battery.

[0061] S2, setting a forward target output voltage value of the bidirectional DC converter as the sampling voltage of the second power battery, wherein the bidirectional DC converter is connected in parallel to the first power battery.

[0062] S3, only using the first power battery to supply power to the motor through the bidirectional DC converter, and the bidirectional DC converter outputs power in the forward direction.

[0063] S4, when the forward output voltage of the bidirectional DC converter is stabilized at the target output voltage, using the first power battery and the second power battery to supply power to the motor at the same time.

[0064] In the embodiment, in the single-battery power supply working condition, the bidirectional DC converter is used to quickly raise or lower the voltage of the first power battery to be equal to the sampling voltage of the second power battery, and the second power battery is connected in parallel after the output voltage is stabilized. Since the voltage raising or lowering process is completely controlled by the duty cycle and no resistance is consumed, the heat loss can be significantly reduced, and the energy utilization rate can be improved. The microsecond-level adjustment can greatly shorten the voltage equalization time, save the additional heat dissipation device, and reduce the cost. In addition, the strategy of stabilizing the voltage first and then connecting in parallel avoids the circulating current impact that may be caused by direct connection in parallel, and improves the system reliability and the battery life.

[0065] As shown in Figure 1 In an embodiment, in combination with a high-voltage electrical system of a dual-power battery, the first power battery is connected to the motor through a first switch group, the first switch group comprises switches K1 and K2, the second power battery is connected to the motor through a second switch group, the second switch group comprises switches K3 and K4, and the bidirectional DC converter is located between the first switch group and the first power battery and is connected in parallel to the first power battery.

[0066] Further, in an embodiment, in the step S1, the bidirectional DC converter obtains the sampling voltage of the second power battery through a CAN network, and a vehicle controller sends a command to control the bidirectional DC converter to output power in the forward direction.

[0067] Further, in an embodiment, in the step S3, the bidirectional DC converter first obtains the sampling voltage of the first power battery through the CAN network, sets the sampling voltage of the second power battery as the target output voltage, closes K1 and K2, and disconnects K3 and K4, so that only the first power battery is used to supply power to the motor through the bidirectional DC converter, the bidirectional DC converter is in forward power output, and the size of the forward output voltage is changed by comparing the sampling voltage of the first power battery with the sampling voltage of the second power battery. If the sampling voltage of the first power battery is higher than the sampling voltage of the second power battery, the bidirectional DC converter works in a forward bucking state, the output voltage of the bidirectional DC converter is lower than the sampling voltage of the first power battery, and the voltage difference between the output voltage and the sampling voltage of the second power battery is continuously reduced during the bucking process.

[0068] If the sampling voltage of the first power battery is lower than the sampling voltage of the second power battery, the bidirectional DC converter works in a forward boosting state, the output voltage of the bidirectional DC converter is higher than the sampling voltage of the first power battery, and the voltage difference between the output voltage and the sampling voltage of the second power battery is continuously reduced during the boosting process.

[0069] In the embodiment, the bidirectional DC converter can automatically select the boosting or bucking working state by comparing the terminal voltages of the two batteries in real time in the unidirectional power supply stage, so that the output voltage is smoothly approximated to the voltage of the second battery, the current loop impact during parallel connection is avoided, the process only relies on duty ratio adjustment, no resistor energy is consumed, heat loss is significantly reduced, an additional heat dissipation device is saved, voltage transition is stable, motor side ripple and noise are simultaneously reduced, the service life of the battery and power device is prolonged, and the system reliability and economy are simultaneously improved.

[0070] Further, in an embodiment, in the step S4, when the forward output voltage of the bidirectional DC converter is stabilized at the target output voltage, K1, K2, K3 and K4 are closed, and the first power battery and the second power battery are used to supply power to the motor at the same time.

[0071] Further, in an embodiment, in the charging method, the bidirectional DC converter obtains the sampling voltage of the second power battery in real time through the CAN network, takes the sampling voltage of the second power battery as the output voltage, and controls and adjusts the bidirectional DC converter in real time so that the output voltage of the bidirectional DC converter follows the sampling voltage of the second power battery.

[0072] In the embodiment, in the charging method, the boosting or bucking working state of the bidirectional DC converter is controlled and adjusted in real time according to the size relationship between the sampling voltage of the first power battery and the sampling voltage of the second power battery, so that the output voltage of the bidirectional DC converter follows the sampling voltage of the second power battery, and the input voltage of the motor is balanced.

[0073] Further, in an embodiment, during the charging process, if the sampling voltage of the first power battery is lower than the normal working threshold, the first power battery stops supplying power to the motor, and the bidirectional DC converter stops working, and then the second power battery alone supplies power to the motor.

[0074] Further, in an embodiment, during the charging process, if the sampling voltage of the second power battery is lower than the normal working threshold, the second power battery stops supplying power to the motor, the bidirectional DC converter outputs power in the forward direction, and the input voltage and the output voltage are equal, and then the first power battery alone supplies power to the motor. This embodiment considers the case that the second power battery is insufficient in power.

[0075] In a third aspect, the embodiments of the present application provide a discharging method of a dual-power battery.

[0076] In an embodiment, referring to FIG. 1, Figure 3 The discharging method comprises: A1, obtaining the sampling voltage of the first power battery and the output voltage of the motor when the vehicle is in the braking state.

[0077] A2, setting the reverse target output voltage value of the bidirectional DC converter as the sum of the sampling voltage of the first power battery and a preset voltage increase.

[0078] A3, the motor directly charges the second power battery in the constant current charging mode.

[0079] A4, when the reverse output voltage of the bidirectional DC converter is stabilized at the target output voltage, the bidirectional DC converter outputs power in the reverse direction, and the motor charges the first power battery and the second power battery.

[0080] In this embodiment, by synchronously sampling the first power battery terminal voltage and the motor output voltage in the braking working condition, and by taking the voltage of the first power battery and the preset voltage increase as the reverse target of the bidirectional DC converter, the converter is always slightly higher than the voltage of the first power battery in the reverse boosting process, so that the motor directly charges the second power battery in the constant current mode first without generating a circulating current impact, and then the energy is distributed to the first power battery after the reverse output voltage is stabilized. This sequential charging strategy not only fully utilizes the motor feedback energy, but also avoids the voltage inversion that may occur when the two batteries are connected at the same time, improves the braking energy recovery efficiency, and only relies on the duty cycle control for the whole boosting regulation without additional resistance energy consumption, so that the system temperature rise is low, the heat dissipation device can be saved, the vehicle cost and weight are reduced, and the reliability and economy of the vehicle energy management system are improved.

[0081] Further, in an embodiment, as shown in FIG. 2, Figure 1As shown, the first power battery is connected with the motor through the first switch group, in this embodiment, the first switch group includes switch K1 and switch K2, the second power battery is connected with the motor through the second switch group, the second switch group includes switch K3 and switch K4, the bidirectional DC converter is located between the first switch group and the first power battery, and is connected in parallel with the first power battery.

[0082] Further, in an embodiment, the bidirectional DC converter obtains the sampling voltage of the first power battery and the output voltage of the motor through the CAN network, K3 and K4 are closed, and K1 and K2 are disconnected, the motor directly charges the second power battery in the constant current charging mode, at the same time, the bidirectional DC converter sets the sum of the sampling voltage of the first power battery and the preset voltage increment as the target output voltage, the bidirectional DC converter reversely outputs power, and the size of the reverse output voltage is changed by comparing the sum of the sampling voltage of the first power battery and the preset voltage increment with the output voltage of the motor. If the output voltage of the motor is higher than the sum of the sampling voltage of the first power battery and the preset voltage increment, at this time, the bidirectional DC converter works in the reverse buck state, in the buck process of the bidirectional DC converter, the output voltage of the bidirectional DC converter is lower than the output voltage of the motor, and the voltage difference between the output voltage of the bidirectional DC converter and the sum of the sampling voltage of the first power battery and the preset voltage increment is continuously reduced.

[0083] If the output voltage of the motor is lower than the sum of the sampling voltage of the first power battery and the preset voltage increment, at this time, the bidirectional DC converter works in the reverse boost state, in the boost process of the bidirectional DC converter, the output voltage of the bidirectional DC converter is higher than the output voltage of the motor, and the voltage difference between the output voltage of the bidirectional DC converter and the sum of the sampling voltage of the first power battery and the preset voltage increment is continuously reduced.

[0084] In this embodiment, by comparing the size of the output voltage of the motor and the sum of the sampling voltage of the first power battery and the preset voltage increment in real time in the brake energy recovery stage, the bidirectional DC converter can automatically switch to the reverse buck or boost state according to the voltage difference. In the buck state, the output voltage of the converter gradually decreases, and the difference between the output voltage and the target voltage is continuously reduced, thereby avoiding the risk of overcharging of the power battery caused by the excessively high output voltage of the motor. In the boost state, the output voltage of the converter gradually increases, thereby ensuring that the energy output by the motor can be efficiently transmitted to the power battery, and avoiding the low energy recovery efficiency caused by the excessively low voltage. This dynamic adjustment mode enables the bidirectional DC converter to accurately control the energy flow, maximally recover the brake energy, and improve the energy utilization rate of the vehicle.

[0085] Further, in an embodiment, when the reverse output voltage of the bidirectional DC converter is stabilized at the target output voltage in the step S4, K1, K2, K3 and K4 are closed, the bidirectional DC converter reversely outputs power, and the motor charges the first power battery and the second power battery.

[0086] Further, in an embodiment, when the vehicle is in a braking state, the bidirectional DC converter outputs power in reverse, and the bidirectional DC converter can also be configured to have an input voltage equal to an output voltage, at which time the motor directly charges the first power battery and the second power battery in a constant current charging mode.

[0087] The application introduces a bidirectional DC converter in parallel between the first power battery and the motor, and uses a real-time sampling voltage of the second power battery as a forward target and a sum of a sampling voltage of the first power battery and a boost voltage as a reverse target, to achieve microsecond-level boost / buck balancing, avoid circulating current impact and heat loss caused by direct parallel connection, and significantly improve energy utilization and system safety. In addition, in the braking energy recovery stage, the second battery is preferentially charged in a constant current mode, and after the voltage is stabilized, the first battery is simultaneously supplemented with energy, so that feedback energy is distributed in order, voltage inversion is prevented, and recovery efficiency is maximized, thereby further enhancing vehicle endurance and running stability.

[0088] It should be noted that the above-mentioned application embodiment serial numbers are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0089] The terms "comprising" and "having" and any variations thereof in the specification and claims of the application and the above-mentioned drawings are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device. The terms "first", "second" and "third" and the like descriptions are used to distinguish different objects, and do not represent the order or limit the types of "first", "second" and "third".

[0090] In the description of the embodiments of the application, "exemplary", "for example" or "for instance" is used to mean as an example, illustration or description. Any embodiment or design scheme described as "exemplary", "for example" or "for instance" in the embodiments of the application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the use of "exemplary", "for example" or "for instance" is intended to present the relevant concept in a specific manner.

[0091] In the description of the embodiments of the application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in the text only describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone, in addition, in the description of the embodiments of the application, "multiple" means two or more than two.

[0092] In some of the processes described in the implementation examples of the present application, multiple operations or steps occur in a specific order. However, it should be understood that the operations or steps can occur in a different order than described or in parallel. The order or sequence of these operations should not be construed as a limitation. Furthermore, the outlined processes can include more, fewer, or only those of the specific steps. Additionally, one or more of the operations or steps can be performed concurrently or with partial concurrence. It is to be understood that the foregoing description is exemplary of the various implementations of the present application.

[0093] Those skilled in the art can clearly understand the above-mentioned embodiment method from the description of the above embodiments, which can be realized by software and necessary general hardware platform, of course, it can also be realized by hardware, but in many cases, the former is a better implementation. Based on such understanding, the technical solutions of the present application can be embodied in the form of a software product, which is stored in a storage medium (such as a ROM / RAM, a magnetic disk, or an optical disc) and includes a plurality of instructions for causing a terminal device to execute the methods described in the various embodiments of the present application.

[0094] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A high voltage electrical system for a dual power battery, characterized in that, include: Electric motor; The first power battery is connected to the motor via the first switch group; The second power battery is connected to the motor via the second switch group; A bidirectional DC-DC converter is located between the first switch group and the first power battery, and is connected in parallel to the first power battery. The forward target output voltage of the bidirectional DC-DC converter is set as the sampling voltage of the second power battery. When the first switch group is closed and the second switch group is open, the first power battery supplies power to the motor separately through the bidirectional DC-DC converter, and the bidirectional DC-DC converter outputs positive power. When the forward output voltage of the bidirectional DC-DC converter stabilizes at the target output voltage, the first and second switch groups are closed, and the first and second power batteries simultaneously supply power to the motor.

2. The high voltage electrical system of a dual power battery as claimed in claim 1, characterized in that, The first power battery has a BMS1, the second power battery has a BMS2, the bidirectional DC-DC converter and the motor each have a control unit, and the BMS1, BMS2 and control unit are all connected to the vehicle controller via a CAN network.

3. A method of charging a dual power battery, characterized by, The charging method includes: Obtain the sampling voltage of the second power battery; The forward target output voltage value of the bidirectional DC-DC converter is set as the sampling voltage of the second power battery, wherein the bidirectional DC-DC converter is connected in parallel with the first power battery; The motor is powered solely by the first power battery via a bidirectional DC-DC converter, with the bidirectional DC-DC converter outputting positive power. When the forward output voltage of the bidirectional DC-DC converter stabilizes at the target output voltage, the first power battery and the second power battery simultaneously power the motor.

4. The charging method of a dual power battery according to claim 3, wherein, The bidirectional DC-DC converter obtains the sampling voltage of the second power battery through the CAN network, and the vehicle controller sends commands to control the forward power output of the bidirectional DC-DC converter.

5. The method of charging a dual power cell of claim 3, wherein, Obtain the sampling voltage of the first power battery when the bidirectional DC-DC converter is outputting power in the forward direction: If the sampling voltage of the first power battery is higher than the sampling voltage of the second power battery, the bidirectional DC-DC converter will operate in the forward buck state. If the sampling voltage of the first power battery is lower than the sampling voltage of the second power battery, the bidirectional DC-DC converter operates in the positive boost state.

6. The method of charging a dual power cell of claim 3, wherein, The sampling voltage of the second power battery is acquired in real time, and the bidirectional DC-DC converter is controlled and adjusted in real time so that its output voltage follows the sampling voltage of the second power battery.

7. The method of charging a dual power cell of claim 3, wherein, If the sampling voltage of the first power battery is lower than its normal operating threshold, the first power battery stops supplying power to the motor, and the second power battery supplies power to the motor alone.

8. The method of charging a dual power cell of claim 3, wherein, If the sampling voltage of the second power battery is lower than its normal operating threshold, the second power battery stops supplying power to the motor, the bidirectional DC-DC converter outputs positive power, and the input voltage and output voltage are equal, and the first power battery supplies power to the motor alone.

9. A method of discharging a dual power battery, characterized by, The discharge method includes: When the vehicle is braking, the sampled voltage of the first power battery and the output voltage of the motor are obtained; The reverse target output voltage value of the bidirectional DC-DC converter is set to the sum of the sampling voltage of the first power battery and the preset voltage boosting voltage; The motor directly charges the second power battery using a constant current charging method. When the reverse output voltage of the bidirectional DC-DC converter stabilizes at the target output voltage, the bidirectional DC-DC converter outputs reverse power, and the motor charges the first and second power batteries.

10. The method of claim 9, wherein the discharging of the dual power cell is performed by a controller. Obtaining a sampling voltage of the first power battery and an output voltage of the motor, when the bidirectional DC converter outputs power reversely: If the output voltage of the motor is higher than the sum of the sampling voltage of the first power battery and a preset voltage increasing voltage, the bidirectional DC converter works in a reverse buck state at this time; If the output voltage of the motor is lower than the sum of the sampling voltage of the first power battery and the preset voltage increasing voltage, the bidirectional DC converter works in a reverse boost state at this time.

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