Vehicle power supply system and method

Abstract

The present disclosure relates to the technical field of vehicle power supply, in particular to a vehicle power supply system and method, wherein the power supply system comprises: a four-quadrant module, an input end of which is connected with a power supply source; a traction inverter, an input end of which is connected with an output end of the four-quadrant module, and an output end of which is connected with a traction motor; a first bidirectional DC / DC module, one end of which is connected with the input end of the traction inverter; an energy storage unit and a BMS; the energy storage unit is charged in a first time period and discharged in a second time period according to the charging and discharging strategy of the BMS, and the electricity price in the second time period is higher than that in the first time period; the BMS is used to determine the charging and discharging strategy based on the electricity price information, the state information of the energy storage unit and the vehicle working condition, with the target of the lowest electricity cost, the constraint condition of the minimum influence on the service life of the energy storage unit and the target SOC of the energy storage unit in the first time period. The dependence on the power grid power supply source during the peak period of the vehicle can be reduced, and the electricity cost can be reduced.

Description

Technical Field

[0001] This disclosure relates to the field of vehicle power supply technology, and in particular to a vehicle power supply system and method. Background Technology

[0002] Currently, different countries and regions use different power supply systems for rail transit. For example, my country's major railways generally use 25kV AC power supply, while urban subways typically use 1500V DC power supply. In Europe, the mainstream power supply systems are AC25kV, AC15kV, DC1500V, and DC3000V.

[0003] Regardless of the power supply system, most adopt time-of-use pricing policies. When vehicle traction systems consume more electricity during peak hours, it not only increases the burden on the power grid but also raises electricity costs. Therefore, reducing vehicle dependence on the power grid during peak hours and lowering electricity costs is a crucial issue that urgently needs to be addressed. Summary of the Invention

[0004] This disclosure provides a vehicle power supply system and method to address the problem of reducing vehicle dependence on the power grid during peak hours and lowering electricity costs.

[0005] In a first aspect, this disclosure provides a vehicle power supply system, comprising: A four-quadrant module, wherein the input terminal of the four-quadrant module is used to connect to the power supply; A traction inverter, wherein the input terminal of the traction inverter is connected to the output terminal of the four-quadrant module, and the output terminal is connected to the traction motor; The first bidirectional DC / DC module has one end connected to the input terminal of the traction inverter; An energy storage unit and a BMS; the energy storage unit is connected to the BMS and the other end of the first bidirectional DC / DC module, respectively, and is used to charge in a first time period and discharge in a second time period according to the charging and discharging strategy of the BMS, wherein the electricity price in the second time period is higher than the electricity price in the first time period. The BMS is used to determine the charging and discharging strategy based on electricity price information, the status information of the energy storage unit, and vehicle operating conditions, with the goal of minimizing electricity costs, minimizing the impact on the lifespan of the energy storage unit, and the energy storage unit reaching the target SOC in the first time period as constraints.

[0006] Optional, also includes: The communication module is used for communication between this vehicle and other vehicles; The BMS is specifically used for: during the first time period, if this vehicle is the first vehicle to return to the depot and the other vehicles returning to the depot are charged according to the charging current in the charging and discharging strategy, and the sum of the charging currents of all vehicles is greater than the maximum allowable charging current, then based on the electricity price information, the departure time of this vehicle and the other vehicles, the status information of the energy storage unit and the vehicle operating condition, with the goal of minimizing the cost of electricity, and with the constraints of minimizing the impact on the lifespan of the energy storage unit, ensuring that the energy storage unit reaches the target SOC before departure, and that the energy storage unit of the vehicle with the earliest departure time reaches the target SOC first, the charging and discharging strategy of each vehicle is re-determined; The first time period is the period with off-peak electricity prices.

[0007] Optionally, the BMS is further configured to: during the second time period, if the energy storage unit meets the traction power requirements, control the energy storage unit to discharge; and during braking conditions, control the energy storage unit to recover braking energy for charging through the traction inverter and the first bidirectional DC / DC module.

[0008] Optionally, the BMS is further configured to, in the third time period, if the SOC of the energy storage unit is detected to be less than the safe operating threshold, lower the current threshold value corresponding to the regenerative braking and control the energy storage unit to regenerate regenerative braking and charge it through the traction inverter and the first bidirectional DC / DC module; after the energy storage unit regenerates regenerative braking and if the SOC of the energy storage unit is still less than the safe operating threshold, control the energy storage unit to charge it through the four-quadrant module and the first bidirectional DC / DC module. The electricity price in the third period is higher than that in the second period.

[0009] Optionally, the least impact on the lifespan of the energy storage unit includes at least one of the following: The number of charge-discharge cycles of the energy storage unit is within the specified threshold. When the temperature of the energy storage unit is greater than a first temperature threshold, the charging current of the energy storage unit is less than a first current threshold. When the temperature value is greater than the second temperature threshold, the discharge current of the energy storage unit is less than the second current threshold. The charging current of the energy storage unit is the minimum charging current.

[0010] Optional, also includes: Transformer; the primary side of the transformer is used to receive a first power supply and a second power supply, the first power supply and the second power supply being AC power supply; The input terminal of the four-quadrant module is connected to the secondary side of the transformer; the input terminal of the four-quadrant module is also connected to the third power supply and the fourth power supply, which are DC power supplies; the four-quadrant module can be switched to be connected to the first power supply or the second power supply and convert AC power to DC power, or it can be switched to be connected to the third power supply or the fourth power supply and realize the function of DC-DC converter.

[0011] Optionally, the four-quadrant module includes: a first switching device, a second switching device, a third switching device, a fourth switching device, a fifth switching device, a sixth switching device, a seventh switching device, an eighth switching device, a first diode, a second diode, a third diode, a fourth diode, a first capacitor, a second capacitor, a first switching circuit, and a second switching circuit. Wherein, the anode of the first switching device is connected to the anode of the fifth switching device and the first terminal of the first capacitor; the cathode of the fourth switching device is connected to the cathode of the eighth switching device; the cathode of the first switching device is connected to the anode of the second switching device; the anode of the third switching device is connected to the cathode of the second switching device, and the cathode of the third switching device is connected to the anode of the fourth switching device; the cathode of the fifth switching device is connected to the anode of the sixth switching device; the anode of the seventh switching device is connected to the cathode of the sixth switching device, and the cathode of the seventh switching device is connected to the anode of the eighth switching device; the cathode of the second switching device... The cathodes of the fourth, sixth, and eighth switching devices are connected to the power supply. The anode of the first diode is connected to the cathode of the second diode, the anode of the third diode, the cathode of the fourth diode, the second terminal of the first capacitor, and the first terminal of the second capacitor, respectively, and the cathode is connected to the anode of the second switching device. The anode of the second diode is connected to the cathode of the third switching device. The cathode of the third diode is connected to the anode of the sixth switching device. The anode of the fourth diode is connected to the cathode of the seventh switching device. The second terminal of the second capacitor is connected to the cathode of the eighth switching device. The first switching circuit is connected between the cathode of the second switching device and the cathode of the sixth switching device; The second switching circuit is connected to the cathode of the fourth switching device, the cathode of the sixth switching device, the cathode of the eighth switching device, and the power supply, and is used to switch the connection between the switching device and the power supply.

[0012] Optionally, it also includes: a reactor connected between the third power supply, the fourth power supply and the four-quadrant module.

[0013] Optionally, the first power supply is AC 25KV, the second power supply is AC 15KV, the third power supply is DC 1500V, and the fourth power supply is DC 3000V.

[0014] Optional, also includes: An auxiliary converter has its input terminal connected to the output terminal of the four-quadrant module, and its output terminal connected to auxiliary electrical equipment.

[0015] Optional, also includes: The bidirectional charger has its input terminal connected to the output terminal of the auxiliary converter, and its output terminal connected to the battery and DC load.

[0016] Optionally, the bidirectional charger includes: an AC-DC conversion module and a DC conversion module.

[0017] Secondly, this disclosure provides a vehicle power supply method, applied to any of the vehicle power supply systems described above, the method comprising: The BMS determines the charging and discharging strategy based on the electricity price information, the status information of the energy storage unit, and the vehicle operating conditions, with the goal of minimizing the electricity cost, minimizing the impact on the lifespan of the energy storage unit, and the energy storage unit reaching the target SOC in the first time period as constraints. The energy storage unit charges during the first time period and discharges during the second time period according to the charging and discharging strategy of the BMS.

[0018] The technical solution provided in this embodiment includes a four-quadrant module, the input of which is connected to the power supply; a traction inverter, the input of which is connected to the output of the four-quadrant module, and the output of which is connected to the traction motor; a first bidirectional DC / DC module, one end of which is connected to the input of the traction inverter; an energy storage unit; and a BMS. The BMS can determine a charging and discharging strategy based on electricity price information, the status information of the energy storage unit, and vehicle operating conditions, with the goal of minimizing electricity costs, minimizing the impact on the lifespan of the energy storage unit, and ensuring the energy storage unit reaches the target SOC in the first time period. The energy storage unit charges in the first time period and discharges in the second time period according to the BMS's charging and discharging strategy. The electricity price in the second time period is higher than that in the first time period, achieving peak shaving and valley filling, reducing electricity costs, and reducing the vehicle's dependence on the grid power supply during peak hours.

[0019] A transformer is used, with its primary side receiving AC power from the first and second power supplies. The input of the four-quadrant module is connected to the secondary side of the transformer. The input of the four-quadrant module is also connected to the third and fourth power supplies, which provide DC power. The four-quadrant module can switch to connect to either the first or second power supply and convert AC to DC; or it can switch to connect to either the third or fourth power supply, functioning as a DC-DC converter. The input of the traction inverter is connected to the output of the four-quadrant module, and the output is connected to the traction motor. The input of the auxiliary converter is connected to the output of the four-quadrant module, and the output is connected to auxiliary electrical equipment. This system enables four different power supply modes, providing both AC and DC power, adapting well to different circuit requirements and meeting the needs of different countries or regions. When the vehicle passes through a phase break or a de-energized section, an energy storage unit boosts the voltage to a set grid voltage level via a first bidirectional DC / DC converter, ensuring uninterrupted power supply and normal vehicle traction within a certain range.

[0020] Furthermore, a bidirectional charger is adopted. Under normal operating conditions, the bidirectional charger charges and powers the vehicle's DC load and battery. In the event of a traction cut-off or other fault, the battery converts DC power into three-phase AC power to ensure uninterrupted power supply to the vehicle's basic load. Attached Figure Description

[0021] The present disclosure will be described in more detail below based on embodiments and with reference to the accompanying drawings: Figure 1 A circuit diagram of a vehicle power supply system provided in an embodiment of this disclosure; Figure 2 A circuit diagram of a vehicle power supply system operating in AC power supply mode, provided for an embodiment of this disclosure; Figure 3 A circuit diagram of a vehicle power supply system operating in DC power supply mode, provided for an embodiment of this disclosure; Figure 4 A circuit diagram of a vehicle power supply system operating in auxiliary power supply mode, provided in an embodiment of this disclosure; Figure 5 A circuit diagram of a vehicle power supply system operating in battery-assisted power supply mode, provided as an embodiment of this disclosure; Figure 6 A schematic diagram illustrating a period of electricity consumption provided in an embodiment of this disclosure; Figure 7 A circuit diagram of a four-quadrant module in a vehicle power supply system provided for embodiments of this disclosure; Figure 8 for Figure 7The equivalent circuit diagram of the four-quadrant module in AC traction power supply mode is shown. Figure 9 for Figure 7 The equivalent circuit diagram of the four-quadrant module in DC traction power supply mode is shown. Figure 10 A flowchart of a vehicle power supply method provided in an embodiment of this disclosure.

[0022] Figure label: Transformer 1; Four-quadrant module 2; Traction inverter 3; Auxiliary converter 4; Traction motor 5; Reactor 6; Bidirectional charger 7; Battery and DC load 8; First bidirectional DC / DC module 9; Energy storage unit 10; Auxiliary electrical equipment 12; BMS 13.

[0023] In the accompanying drawings, the same parts are referred to by the same reference numerals, and the drawings are not drawn to scale. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of this disclosure, and to fully understand and implement the process of how this disclosure applies technical means to solve technical problems and achieve corresponding technical effects, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. The embodiments of this disclosure and the various features within them can be combined with each other without conflict, and the resulting technical solutions are all within the protection scope of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort should fall within the protection scope of this disclosure.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0027] Regarding the published patents and papers on vehicle main circuits applied to different power supply systems, the main considerations are the compatibility of AC15kV, AC25kV, and DC1500V voltages, but the following issues still exist: Firstly, in some countries and regions, the power supply voltage is DC3000V, while there are few traction system main circuits that are fully compatible with DC3000V, DC1500V, AC15kV, and AC25kV. Secondly, with the emergence of new energy locomotives and electric locomotives traction by power batteries, how to consider the vehicle's traction through the powerless zone by battery and ensure the full absorption of the vehicle's braking energy while being compatible with the main circuit of different power supply systems is also a current research hotspot of the traction system main circuit. Thirdly, the vehicle's auxiliary power supply system charger can only achieve single-phase energy conversion, that is, converting three-phase AC voltage to DC 110V, mainly for DC loads and battery charging. However, when the traction system fails and traction is disconnected, in order to ensure the normal use of essential loads such as vehicle ventilation and emergency lighting, it is also necessary to consider the use of battery power DC 110V to three-phase AC power. Currently, bidirectional power conversion of batteries via chargers is not common.

[0028] Therefore, considering the main circuit of the traction system under different power supply systems and modes, and taking into account the bidirectional energy flow between the traction and auxiliary systems from new energy sources, storage batteries, and power batteries, has certain practical value for realizing vehicle interconnection and improving the efficiency and capacity of rail transportation.

[0029] like Figure 1 As shown, this embodiment provides a vehicle power supply system, including: Four-quadrant module 2, the input terminal of which is used to connect to the power supply.

[0030] Traction inverter 3 has its input terminal connected to the output terminal of four-quadrant module 2, and its output terminal connected to traction motor 5. Traction motor 5 is used to provide running drive force to the wheelsets of the power bogie.

[0031] The first bidirectional DC / DC module 9 has one end connected to the input terminal of the traction inverter 3.

[0032] Energy storage unit 10 and battery management system (BMS) 13; energy storage unit 10 is connected to BMS 13 and the other end of the first bidirectional DC / DC module 9 respectively, and is used to charge in the first time period and discharge in the second time period according to the charging and discharging strategy of BMS 13, wherein the electricity price in the second time period is higher than the electricity price in the first time period.

[0033] BMS13 is used to determine charging and discharging strategies based on electricity price information, energy storage unit status information, and vehicle operating conditions, with the goal of minimizing electricity costs, minimizing the impact on the lifespan of energy storage units, and ensuring that the energy storage units reach the target state of charge (SOC) in the first time period.

[0034] For example, the vehicle power supply system also includes a transformer 1, wherein the primary side of the transformer 1 receives a first power supply and a second power supply, both of which are AC power supplies. The voltages of the first and second power supplies are different. The input terminal of the four-quadrant module 2 is connected to the secondary side of the transformer 1; the input terminal of the four-quadrant module 2 is also connected to a third power supply and a fourth power supply, both of which are DC power supplies. The four-quadrant module 2 has two operating modes: AC traction power supply mode and DC power supply mode. When in AC traction power supply mode, the four-quadrant module 2 switches to connect to either the first or second power supply and converts the AC power to DC power. When in DC power supply mode, the four-quadrant module 2 switches to connect to either the third or fourth power supply, realizing the function of a DC-DC converter.

[0035] In the above scheme, the first power supply and the second power supply can be set according to common power supply systems. In this embodiment, the first power supply is AC 25KV and the second power supply is AC 15KV, so the above scheme can meet both AC 25KV and AC 15KV power supply requirements.

[0036] In the above scheme, the third and fourth power supplies can be set according to common power supply systems. In this embodiment, the third power supply is DC 1500V and the fourth power supply is DC 3000V, so the above scheme can meet both DC 1500V and DC 3000V power supply requirements.

[0037] Based on the above, this embodiment can accept AC 25KV or AC 15KV power supply, as well as DC 1500V or DC 3000V power supply. These four different power supply systems can provide a stable and reliable power supply to the vehicle under different power supply systems.

[0038] The aforementioned vehicles can be rubber-tired vehicles that travel on urban roads, or they can be trams.

[0039] Alternatively, the vehicle provided in this embodiment can be a train, comprising multiple carriages coupled together, with each carriage having a bogie at its bottom for running on rails. This vehicle can be a high-speed train, light rail, or conventional vehicle, etc.

[0040] The vehicle power supply system also includes a reactor 6, which is connected between the third power supply, the fourth power supply and the four-quadrant module 2.

[0041] When the vehicle is in AC traction power supply mode, it is powered by the AC grid (first or second power supply). The four-quadrant module 2 is in rectification mode, converting the AC power supply into DC power, which is then supplied to the traction inverter 3. When the vehicle is in braking mode, the four-quadrant module 2 is in inverter mode, feeding the braking energy back to the grid. When the vehicle is in DC power supply mode, the four-quadrant module 2 becomes a bidirectional DC / DC module. The DC grid voltage (third or fourth power supply) is stabilized near a fixed voltage value by the reactor 6 energized on the line and the four-quadrant module 2, ensuring that the traction inverter 3 can stably drive the traction motor 5 under different DC grid voltages.

[0042] Specifically, when a vehicle enters an AC 15kV or AC 25kV power supply area, the vehicle shall comply with... Figure 2 The main circuit provides traction power. Specifically, AC voltage is transferred from the pantograph via transformer 1, converting AC 15kV or AC 25kV to AC 970V. This AC voltage is then rectified and stabilized at DC 3600V by the rectifier module in the four-quadrant module 2, and finally inverted into a three-phase voltage of 0-2808V by the traction inverter 3 to power the traction motor 5. When the vehicle enters braking mode, the braking energy generated by the traction motor 5 is rectified to DC 3600V by the traction inverter 3, and then inverted back to AC 970V by the four-quadrant module 2 to feed the DC energy back to the grid.

[0043] When the vehicle enters a DC 1500V or DC 3000V power supply area, the vehicle shall... Figure 3 The main circuit provides traction power. Specifically, the DC voltage is supplied from the pantograph via the line reactor 6, then rectified and chopped by the four-quadrant module 2, and finally stabilized at DC 3600V through a DC / DC converter. This DC voltage is then inverted into a three-phase voltage of 0-2808V by the traction inverter 3 to power the motor for normal operation. When the vehicle enters braking mode, the braking energy generated by the motor braking is rectified to DC 3600V by the traction inverter 3, and then stepped down to DC 1500V or DC 3000V by the four-quadrant module before being fed back to the traction network.

[0044] In practical applications, electricity consumption periods can be divided according to electricity prices. For example, electricity consumption periods can include a first period and a second period, with the electricity price in the second period being higher than that in the first period. The energy storage unit 10 can reduce the power supply from the grid during the second period when electricity prices are high by charging in the first period and discharging in the second period. For example, the first period can be a period with off-peak electricity prices, and the second period can be a period with flat electricity prices. Alternatively, the first period can be a period with flat electricity prices, and the second period can be a period with peak electricity prices. Off-peak electricity prices are lower than flat electricity prices, and flat electricity prices are lower than peak electricity prices.

[0045] The charging and discharging strategy includes charging and discharging time and charging and discharging current.

[0046] Specifically, the BMS uses charging and discharging time and charging and discharging current as variables, and calculates the electricity cost within a preset period (e.g., the whole day) based on electricity price information, energy storage unit status information, and vehicle operating conditions. Based on this electricity cost, an objective function is constructed with the goal of minimizing the electricity cost and with the constraints of minimizing the impact on the lifespan of the energy storage unit and ensuring that the energy storage unit reaches the target SOC in the first period. Based on this objective function, the charging and discharging strategy is determined.

[0047] For example, a particle swarm optimization algorithm can be used to solve for the objective function and obtain the charging and discharging strategy with the lowest electricity cost.

[0048] Of course, neural network models and other methods can also be used to determine the charging and discharging strategy.

[0049] The target SOC can be 100% or a first SOC threshold below 100%, which can be set according to the actual situation.

[0050] The status information of an energy storage unit can include its SOC, SOH, and temperature.

[0051] Electricity price information can include electricity prices for different time periods.

[0052] Vehicle operating conditions can include traction conditions, braking conditions, etc.

[0053] The energy storage unit 10 may include a power battery or other auxiliary power sources such as new energy sources.

[0054] By using the constraint of minimizing the impact on the lifespan of the energy storage unit, the impact of the charging and discharging strategy on the lifespan of the energy storage unit can be reduced. For example, minimizing the impact on the lifespan of the energy storage unit includes at least one of the following: First, the number of charge-discharge cycles of the energy storage unit is within the threshold.

[0055] By limiting the number of charge-discharge cycles, excessive wear and tear on energy storage units can be avoided, reducing the impact on their lifespan. The number of cycles threshold can be set according to the actual situation of the energy storage unit.

[0056] Second, when the temperature of the energy storage unit is greater than the first temperature threshold, the charging current of the energy storage unit is less than the first current threshold.

[0057] Third, when the temperature value is greater than the second temperature threshold, the discharge current of the energy storage unit is less than the second current threshold.

[0058] The first temperature threshold and the second temperature threshold can be set according to the actual situation.

[0059] If the temperature of the energy storage unit is too high, charging and discharging with a large current will damage the energy storage unit and affect its lifespan. Therefore, when determining the charging and discharging strategy, the real-time temperature of the energy storage unit should be considered. When the temperature is too high, the charging and discharging current should be constrained and a small current should be used for charging and discharging.

[0060] Fourth, the charging current of the energy storage unit is the minimum charging current.

[0061] During the charging process, while meeting the demand, we should try to reduce the damage to the power battery and the impact on the power grid caused by high current charging by using a slow charging friendly mode. Therefore, in the charging and discharging strategy, we can prioritize the minimum charging current that meets the optimization goal, thereby minimizing the charging current.

[0062] like Figure 4 In the auxiliary power supply mode shown, the energy storage unit also boosts the DC power to the set DC grid voltage through the first bidirectional DC / DC module in the event of main traction failure, and provides uninterrupted power to the traction motor 5 via the traction inverter 3. Simultaneously, when braking energy cannot be fully fed back to the grid during vehicle braking, the intermediate voltage can also be used to recover energy from energy storage units such as the power battery through the first bidirectional DC / DC module 9.

[0063] For example, such as Figure 1 As shown, the vehicle power supply system also includes an auxiliary converter 4. The input terminal of the auxiliary converter 4 is connected to the output terminal of the four-quadrant module 2, and the output terminal of the auxiliary converter 4 is connected to the auxiliary electrical equipment 12 (e.g., Figure 1 Connect the 3AC loads in the system. Auxiliary electrical equipment can include: air conditioners, lighting, door control systems, etc.

[0064] Importantly, when the energy storage unit 10 is not charged to the standard requirement or has a low charge level during vehicle operation, the system can be configured to store the required electrical energy from new energy sources, power batteries, etc., by inverting the grid voltage to an intermediate grid voltage via an auxiliary converter 4 after the vehicle returns to the depot or through an in-depot socket, and then via the first bidirectional DC / DC module 9. Simultaneously, charging of the in-depot energy storage unit 10 can be considered during periods of lower electricity prices at night (i.e., off-peak electricity prices). Then, during peak power periods of high electricity prices the following day, the main grid traction power supply can be switched to the energy storage unit's traction during specific periods, ultimately achieving a significant effect of peak shaving and valley filling, while simultaneously reducing transformer base capacity costs and high-price period payment costs, thereby lowering operating costs.

[0065] The auxiliary traction mode of the energy storage unit in this embodiment has good compatibility with the main traction mode.

[0066] The technical solution provided in this embodiment uses a transformer, whose primary side receives AC power from a first power supply and a second power supply. The input terminal of the four-quadrant module is connected to the secondary side of the transformer. The input terminal of the four-quadrant module is also connected to a third power supply and a fourth power supply, which provide DC power. The four-quadrant module can be switched to connect to the first or second power supply and convert AC power to DC power; or it can be switched to connect to the third or fourth power supply to realize the function of a DC-DC converter. The input terminal of the traction inverter is connected to the output terminal of the four-quadrant module, and the output terminal is connected to the traction motor. The input terminal of the auxiliary converter is connected to the output terminal of the four-quadrant module, and the output terminal is connected to the auxiliary electrical equipment. This realizes four different power supply systems, enabling both AC and DC power supply, which can well adapt to the needs of different lines and meet the needs of different countries or regions.

[0067] In this embodiment, the BMS can determine a charging and discharging strategy based on electricity price information, energy storage unit status information, and vehicle operating conditions, with the goal of minimizing electricity costs and the constraints of minimizing the impact on the lifespan of the energy storage unit and ensuring that the energy storage unit reaches the target SOC in the first time period. According to the charging and discharging strategy of the BMS, the energy storage unit charges in the first time period and discharges in the second time period. The electricity price in the second time period is higher than that in the first time period, achieving the effect of peak shaving and valley filling, reducing electricity costs, and reducing the vehicle's dependence on the grid power supply during peak hours.

[0068] In some embodiments, the vehicle power supply system further includes: The communication module is used for communication between this vehicle and other vehicles. Specifically, BMS is used in the following situations: In the first time period, if this vehicle is the first vehicle to return to the depot and other vehicles returning to the depot are charged according to the charging current in the charging and discharging strategy, and the sum of the charging current of all vehicles is greater than the maximum allowable charging current, then based on the electricity price information, the departure time of this vehicle and other vehicles, the status information of the energy storage unit, and the vehicle operating condition, with the goal of minimizing the cost of electricity, minimizing the impact on the lifespan of the energy storage unit, and prioritizing the energy storage unit to reach the target SOC in the vehicle with the earliest departure time, the charging and discharging strategy of each vehicle is re-determined. The first time period is the period with off-peak electricity prices.

[0069] The communication module can be a wireless communication module. Vehicles establish communication connections through this module, enabling information exchange and transmission.

[0070] During off-peak electricity pricing periods, deep energy storage unit 10 can be used for energy storage. If a vehicle returns to the depot first during these periods, its BMS (Battery Management System) can be designated as the primary BMS to determine a charging / discharging strategy. Based on this strategy, charging commands are sent to the vehicle's energy storage unit for charging. This vehicle is the one with the primary BMS. When other vehicles subsequently return, the primary BMS pre-calculates the sum of the charging currents for all vehicles according to the existing charging / discharging strategy. If the calculated result is less than or equal to the depot's maximum allowable charging current, the existing charging / discharging strategy is sent to the other vehicles. If the calculated result is greater than the depot's maximum allowable charging current, a new charging / discharging strategy needs to be determined.

[0071] To avoid a significant impact on the power grid caused by all vehicles charging during off-peak hours at night, and considering the different departure times of the vehicles, the order of vehicle departures on the following day can be controlled to ensure orderly and staggered charging. Therefore, the main BMS can, based on electricity price information, the departure times of its own vehicle and other vehicles, the status information of the energy storage units, and the vehicle's operating conditions, determine the charging and discharging strategy for each vehicle with the goal of minimizing electricity costs, minimizing the impact on the lifespan of the energy storage units, ensuring that the energy storage units reach the target SOC before departure, and prioritizing the vehicles with the earliest departure times to reach the target SOC. In this way, by comprehensively considering the situation of each vehicle, orderly and staggered charging according to the departure order on the following day is ensured, avoiding a significant impact on the power grid.

[0072] In some embodiments, the BMS is also used to: control the energy storage unit to discharge if the energy storage unit meets the traction power requirements during the second time period; and control the energy storage unit to recover braking energy for charging through the traction inverter and the first bidirectional DC / DC module during braking conditions.

[0073] During periods of flat or peak electricity prices, energy storage units release electrical energy: if the energy storage units can meet the traction power requirements, priority is given to using the electricity stored by the energy storage units during off-peak electricity prices, thereby reducing electricity costs.

[0074] To avoid the impact of excessive discharge on the lifespan of the energy storage unit, if the energy storage unit meets the traction power requirements and the SOC of the energy storage unit is not lower than the second SOC threshold, the discharge of the energy storage unit is controlled.

[0075] Under vehicle braking conditions, the braking energy of the traction motor is also considered to charge the energy storage unit 10 through the traction inverter 3 and the first bidirectional DC-DC9, thereby replenishing the energy storage unit 10 and further reducing electricity costs.

[0076] In some embodiments, the BMS is also used to, in the third time period, if the SOC of the energy storage unit is detected to be less than the safe operation threshold, reduce the current threshold value corresponding to the regenerative braking energy and control the energy storage unit to regenerate the regenerative braking energy for charging through the traction inverter and the first bidirectional DC / DC module; after the energy storage unit regenerates the regenerative braking energy, if the SOC of the energy storage unit is still less than the safe operation threshold, control the energy storage unit to charge through the four-quadrant module and the first bidirectional DC / DC module. The electricity price in the third time period is higher than that in the second time period.

[0077] Here, the second time period is the period with flat electricity prices, the third time period is the period with peak electricity prices, and the first time period is the period with valley electricity prices.

[0078] Under normal circumstances, a relatively large current threshold is set during braking. When a large current exceeding the current threshold is generated during braking, braking energy recovery is performed.

[0079] The specific value of the safe operation threshold can be set according to actual needs.

[0080] When the SOC of the energy storage unit is still less than the safe operating threshold, the energy storage unit can be fast-charged at stations where the vehicle's stop time exceeds a preset duration, specifically when the energy storage unit is charged through the four-quadrant module and the first bidirectional DC / DC module. The fast-charging current can be determined based on the SOC of the energy storage unit and the vehicle's stop time.

[0081] Since the peak electricity price is the highest price of the day, the energy storage unit will not actively charge from the grid during this period in principle.

[0082] In this embodiment, the energy storage unit can be coordinated for charging during peak electricity price periods. When the SOC of the energy storage unit is detected to be less than the safe operating threshold, the current threshold value corresponding to the electric braking energy recovery under braking conditions can be adjusted. Even when a microcurrent is generated during braking, the energy storage unit can be controlled to recover braking energy for charging through the traction inverter and the first bidirectional DC / DC module. If the SOC of the energy storage unit is still less than the safe operating threshold after braking energy recovery, fast charging of the energy storage unit at stations with relatively long vehicle stop times can be considered to ensure safe operation.

[0083] The following uses a train and its energy storage unit, including a power battery pack, as an example to illustrate how the BMS determines the charging and discharging strategy in the vehicle power supply system of this embodiment.

[0084] Assuming that during the electricity consumption period, the first i Electricity price information for the time period is ,but: (1) See Figure 6 Electricity consumption periods are divided into multiple time periods. Figure 6 China and Israel at different times to Indication.

[0085] Assume the first l Train No. i The train power demand during the time period is P l,i Then P l,i A positive value indicates the first l Train No. i The traction power required during the time period, P l,i A negative value indicates the first l Train No. i The braking power provided during the time period is considered, taking into account that the train's braking power can be absorbed by adjacent vehicles and the power battery. Considering the first... l The k-th power battery pack of the train is in the... i The SOC, SOH, and temperature values ​​for the time period were respectively , , Assuming the first l The k-th power battery pack of the train is in the... i The charging and discharging current during the period is The charging and discharging voltage is The corresponding charging and discharging power is A positive value indicates charging power, and a negative value indicates discharging power, as detailed below: (2) Right now, >0 indicates the first l Train No.i Charging power during the period <0 indicates the first l Train No. i The discharge power during the specified time period. Then, the charging cost for all trains on the entire line to be charged from the power grid is considered. f 1 is: (3) Where L represents the total number of trains on the entire line, K represents the number of battery packs per train, and T represents the number of time periods divided according to different electricity prices. This only indicates the voltage during charging from the power grid. This only represents the current used for charging from the power grid. Meanwhile, the cost of electricity absorbed from the power grid for train traction during operation is expressed as follows: f 2: (4) Therefore, the electricity cost for all trains throughout the day can be expressed as F = f 1+ f 2.

[0086] Meanwhile, the power battery must meet at least the following constraints in each time period: (5) in, , Indicates that the power battery is i Periodic charging and discharging The upper limit (such as the upper limit of the target SOC mentioned above) and the lower limit (such as the safe operation threshold mentioned above). , Indicates that the power battery is i Time period The upper and lower limits, , Indicates that the power battery is i Temperature values ​​corresponding to the time period The upper limit value (refer to the above-mentioned first temperature threshold and second temperature threshold settings) and the lower limit value, , Indicates that the power battery is i Permissible number of charge / discharge cycles during a given period The upper limit (such as the above-mentioned number of times threshold) and lower limit, , , , This indicates the upper and lower limits of the charging and discharging voltage and current of the power battery. This represents the upper limit of the total charging and discharging current corresponding to all trains that are charging or discharging in the current period (such as the maximum allowable charging current mentioned above). These state-related currents are all related to the current charging and discharging current of the power battery, and can also be expressed as an implicit function g of the charging and discharging current.

[0087] Of course, other constraints can be added, which will not be listed here.

[0088] Therefore, an optimization objective function is constructed with the goal of minimizing the total electricity cost for the entire train line throughout the day (i.e., minimizing electricity consumption). Considering safety constraints such as battery SOC, safety indicators, and charging / discharging voltage and current, artificial intelligence optimization algorithms, including genetic algorithms, particle swarm optimization, and artificial neural networks, are used to find the optimal charging / discharging strategy that optimizes the objective function. Additionally, other optimization objectives can be incorporated, such as maximizing SOH, etc., which will not be listed here. Furthermore, based on the optimal charging / discharging strategy (i.e., the charging / discharging plan), and considering the actual operating conditions of the train (such as traction failures, entering power-depleted areas, crossing phase-splitting areas, and basic safety indicators of the power battery), the charging / discharging strategy is dynamically optimized and adjusted. For example, this might involve reducing braking energy to set a threshold for power battery energy storage and utilizing station entry time for rapid charging to ensure optimal power battery operation.

[0089] In some embodiments, such as Figure 1 As shown, the vehicle power supply system also includes a bidirectional charger 7. The input terminal of the bidirectional charger 7 is connected to the output terminal of the auxiliary converter 4, and the output terminal of the bidirectional charger 7 is connected to the battery and the DC load 8. The bidirectional charger 7 is used to supply power to the battery and the DC load 8.

[0090] The bidirectional charger includes an AC-DC conversion module and a DC conversion module.

[0091] One implementation involves integrating a second bidirectional DC / DC module (i.e., a DC-DC converter module) into the bidirectional charger 7. When the vehicle is operating normally, the three-phase output voltage of the auxiliary converter 4 is rectified by the bidirectional charger 7 into DC 110V to charge the vehicle battery and DC load 8. In case of traction failure or other fault conditions, to ensure uninterrupted power supply to the vehicle's basic loads such as ventilation and lighting, the battery power is boosted by the second bidirectional DC / DC module of the bidirectional charger and then inverted into three-phase AC voltage to power the vehicle's basic loads.

[0092] For auxiliary power supply from the battery, this embodiment employs a bidirectional charger 7 in the power system of the auxiliary converter 4. This means that the output power of the auxiliary converter 4 can be converted into DC 110V via the bidirectional charger for charging the battery and supplying power to DC loads; it can also convert the energy stored in the battery into three-phase AC power via the bidirectional charger to provide uninterrupted power for basic loads such as ventilation and lighting required for normal vehicle operation. Figure 5 The main circuit provides traction power.

[0093] Furthermore, when vehicle traction fails or malfunctions lead to traction disconnection, in order to ensure uninterrupted power supply for basic loads such as vehicle ventilation and lighting, the battery, when fully charged, can be converted into three-phase AC power by a bidirectional charger including a second bidirectional DC / DC module, converting the battery's DC 110V power into three-phase AC power to ensure the power supply needs of the vehicle's basic operating loads.

[0094] This embodiment also provides an implementation method for the four-quadrant module 2 based on the above technical solution: like Figure 7 As shown, the four-quadrant module includes: a first switching device S1, a second switching device S2, a third switching device S3, a fourth switching device S4, a fifth switching device S5, a sixth switching device S6, a seventh switching device S7, an eighth switching device S8, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first capacitor Cd1, a second capacitor Cd2, a first switching circuit (relay control circuit 1' as shown in the figure) and a second switching circuit (relay control circuit 2' as shown in the figure).

[0095] In this configuration, the anode of the first switching device S1 is connected to the anode of the fifth switching device S5, and the first terminal of the first capacitor Cd1 is connected to it; the cathode of the fourth switching device S4 is connected to the cathode of the eighth switching device S8; the cathode of the first switching device S1 is connected to the anode of the second switching device S2; the anode of the third switching device S3 is connected to the cathode of the second switching device S2, and the cathode of the third switching device S3 is connected to the anode of the fourth switching device S4; the cathode of the fifth switching device S5 is connected to the anode of the sixth switching device S6; the anode of the seventh switching device S7 is connected to the cathode of the sixth switching device S6, and the cathode of the seventh switching device S7 is connected to the anode of the eighth switching device S8; the cathode of the second switching device S2... The cathodes of the fourth switching device S4, the sixth switching device S6, and the eighth switching device S8 are connected to the power supply. The anode of the first diode D1 is connected to the cathode of the second diode D2, the anode of the third diode D3, the cathode of the fourth diode D4, the second terminal of the first capacitor Cd1, and the first terminal of the second capacitor Cd2, respectively, and the cathode is connected to the anode of the second switching device S2. The anode of the second diode D2 is connected to the cathode of the third switching device S3. The cathode of the third diode D3 is connected to the anode of the sixth switching device S6. The anode of the fourth diode D4 is connected to the cathode of the seventh switching device S7. The second terminal of the second capacitor Cd2 is connected to the cathode of the eighth switching device S8. Figure 7 The power supply U is used in the middle N This indicates the power supply, specifically connected to the secondary side of transformer 1 or to the third or fourth power supply.

[0096] The cathode of the second switching device S2 and the power supply U N An inductor L1 and a resistor R are connected in series between them. The anode of the first switching device S1 and the anode of the fifth switching device S5, and the cathode of the fourth switching device S4 and the cathode of the eighth switching device S8, also serve as the output terminals of the four-quadrant module 2, connected to the subsequent load. The voltage of the first capacitor Cd1 is Ud1, and the voltage of the second capacitor Cd2 is Ud2.

[0097] The first switching circuit is connected between the cathode A of the second switching device S2 and the cathode B of the sixth switching device S6. The first switching circuit is a circuit connected by relay contacts. The circuit is considered to be conducting when the normally open contacts of the relay are closed; the circuit is considered to be disconnected when the normally open contacts are open.

[0098] The second switching circuit is connected to the cathodes of the fourth switching device S4, the sixth switching device S6, and the eighth switching device S8, as well as the power supply, and is used to switch the connection between the switching devices and the power supply. The second switching circuit is a circuit with relay contacts, such as a single-pole double-throw structure, with one end connected to the power supply and the other two ends connected to the cathodes of the eighth switching device S8, the fourth switching device S4, and the sixth switching device S6, respectively.

[0099] Each switching device is equipped with an anti-parallel diode.

[0100] When the vehicle is in AC traction power supply mode, relay control circuit 1' is in the equivalent switch open state, and relay control circuit 2' is in the equivalent switch closed at point α and open at point β. Therefore, the cathode of the second switching device S2 and the anode of the seventh switching device S7 are connected to the power supply. Figure 8 As shown. Specifically, when the vehicle is in traction mode, the four-quadrant module 2 is in rectification mode; when the vehicle is in braking mode, the four-quadrant module 2 is in inverter mode, feeding the vehicle's braking energy back to the power grid.

[0101] When the vehicle is in DC traction power supply mode, relay control circuit 1' is in the equivalent switch closed state, and relay control circuit 2' is in the equivalent switch open at point α and closed at point β, as shown below. Figure 9 As shown. At this time, the four-quadrant module 2 is a bidirectional DC / DC module. The DC grid voltage is stabilized near a fixed voltage value by the line reactor 6 and the bidirectional DC / DC module, ensuring that the inverter can stably drive the traction motor under different DC grid voltages.

[0102] The four-quadrant module in this embodiment adopts a three-level structure, which can reduce the insulation withstand voltage requirements of the switching devices and help reduce harmonics. The voltage clamping function can also be achieved by setting the first to fourth diodes.

[0103] The solution provided in this embodiment offers a traction system main circuit compatible with four different power supply systems: AC 25kV, AC 15kV, DC 1500V, and DC 3000V. This ensures that the vehicle can receive uninterrupted power regardless of the power supply system. Simultaneously, the four-quadrant module 2 can stabilize the grid voltage to a set level under different power supply conditions, ensuring a stable and reliable output power supply from the traction inverter 3.

[0104] Furthermore, while ensuring compatibility with traction system main circuits using different power supply systems, new energy sources and power batteries are considered as energy storage units. When the vehicle passes through phase breaks or de-energized sections, the energy storage unit's voltage is boosted to the set grid voltage level by a first bidirectional DC / DC converter, ensuring uninterrupted power supply and normal vehicle traction within a certain range. Simultaneously, during vehicle braking, the voltage is rectified to the set grid voltage by the traction inverter and then stepped down by the first bidirectional DC / DC converter to charge the energy storage unit.

[0105] When a vehicle returns to the depot at night or enters the depot, the voltage is converted to the set grid voltage via the auxiliary converter 4 through the charging socket in the depot. After being stepped down by the first bidirectional DC / DC module 9, the energy storage unit is charged. Through a reasonable charging and discharging control strategy, load peak shaving and valley filling can be achieved, further reducing the cost of transformer base capacity and reducing the electricity bills paid by vehicles during periods of high electricity prices.

[0106] This embodiment also employs a bidirectional charger 7. Under normal operating conditions, the bidirectional charger 7 converts the output power of the auxiliary converter 4 into DC 110V to power the vehicle's DC load and charge the battery. In the event of a traction cut-off or other fault, the battery converts the DC 110V power into three-phase AC power via the bidirectional charger 7 to ensure uninterrupted power supply to the vehicle's basic load.

[0107] In summary, this embodiment comprehensively considers situations where the main traction is powered by the grid and onboard energy storage, such as power batteries, serves as an auxiliary traction and power supply system. It proposes an onboard bidirectional DC / DC power supply system that considers multiple systems and modes. Simultaneously, it considers the optimized utilization of energy on the grid power supply side, the energy storage system side, and the load power consumption side to achieve efficient energy utilization of the system. To ensure the interconnection and interoperability of vehicles operating under different power supply systems and modes, and to improve vehicle transportation efficiency, it provides new solutions for energy optimization scheduling when new energy sources and power batteries are used as auxiliary traction power supplies, as well as for ensuring uninterrupted power supply to the basic load during vehicle traction disconnection and other fault conditions.

[0108] This disclosure also relates to a vehicle power supply method, applied to a vehicle power supply system as described in any of the above embodiments, such as... Figure 10 As shown, the method includes: Step S1001: The BMS determines the charging and discharging strategy based on the electricity price information, the status information of the energy storage unit, and the vehicle operating conditions, with the goal of minimizing the electricity cost, minimizing the impact on the lifespan of the energy storage unit, and the energy storage unit reaching the target SOC in the first time period as constraints.

[0109] Step S1002: The energy storage unit charges during the first time period and discharges during the second time period according to the charging and discharging strategy of the BMS.

[0110] In some embodiments, the vehicle power supply method further includes: If, during the first time period, this vehicle is the first vehicle to return to the depot and the other vehicles returning to the depot are charging according to the charging current in the charging and discharging strategy, and the sum of the charging currents of all vehicles is greater than the maximum allowable charging current, then based on the electricity price information, the departure time of this vehicle and the other vehicles, the status information of the energy storage unit, and the vehicle operating condition, with the goal of minimizing electricity costs, and with the constraints of minimizing the impact on the lifespan of the energy storage unit, ensuring that the energy storage unit reaches the target SOC before departure, and prioritizing the energy storage unit to reach the target SOC among the vehicles with the earliest departure time, the BMS will re-determine the charging and discharging strategy for each vehicle. The first time period is the period with off-peak electricity prices.

[0111] In some embodiments, the vehicle power supply method further includes: During the second time period, if the energy storage unit meets the traction power requirements, the BMS controls the energy storage unit to discharge; and under braking conditions, it controls the energy storage unit to recover braking energy and charge through the traction inverter and the first bidirectional DC / DC module.

[0112] In some embodiments, the vehicle power supply method further includes: In the third time period, if the BMS detects that the SOC of the energy storage unit is less than the safe operation threshold, it lowers the current threshold value corresponding to the regenerative braking and controls the energy storage unit to regenerate braking energy for charging through the traction inverter and the first bidirectional DC / DC module; after the energy storage unit regenerates braking energy, if the SOC of the energy storage unit is still less than the safe operation threshold, it controls the energy storage unit to charge through the four-quadrant module and the first bidirectional DC / DC module. The electricity price in the third period is higher than that in the second period.

[0113] In some embodiments, the minimal impact on the lifespan of the energy storage unit includes at least one of the following: The number of charge-discharge cycles of the energy storage unit is within the specified threshold. When the temperature of the energy storage unit is greater than a first temperature threshold, the charging current of the energy storage unit is less than a first current threshold. When the temperature value is greater than the second temperature threshold, the discharge current of the energy storage unit is less than the second current threshold. The charging current of the energy storage unit is the minimum charging current.

[0114] It should be noted that, in this disclosure, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element limited by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0115] While the embodiments disclosed herein are as described above, the foregoing content is merely for the purpose of facilitating understanding of this disclosure and is not intended to limit this disclosure. Any person skilled in the art to which this disclosure pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope of this disclosure; however, the scope of patent protection of this disclosure shall still be determined by the scope defined in the appended claims.

Claims

1. A vehicle power supply system, characterized in that, include: A four-quadrant module, wherein the input terminal of the four-quadrant module is used to connect to the power supply; A traction inverter, wherein the input terminal of the traction inverter is connected to the output terminal of the four-quadrant module, and the output terminal is connected to the traction motor; The first bidirectional DC / DC module has one end connected to the input terminal of the traction inverter; An energy storage unit and a BMS; the energy storage unit is connected to the BMS and the other end of the first bidirectional DC / DC module, respectively, and is used to charge in a first time period and discharge in a second time period according to the charging and discharging strategy of the BMS, wherein the electricity price in the second time period is higher than the electricity price in the first time period. The BMS is used to determine the charging and discharging strategy based on electricity price information, the status information of the energy storage unit, and vehicle operating conditions, with the goal of minimizing electricity costs, minimizing the impact on the lifespan of the energy storage unit, and the energy storage unit reaching the target SOC in the first time period as constraints.

2. The vehicle power supply system according to claim 1, characterized in that, Also includes: The communication module is used for communication between this vehicle and other vehicles; The BMS is specifically used for: during the first time period, if this vehicle is the first vehicle to return to the depot and the other vehicles returning to the depot are charged according to the charging current in the charging and discharging strategy, and the sum of the charging currents of all vehicles is greater than the maximum allowable charging current, then based on the electricity price information, the departure time of this vehicle and the other vehicles, the status information of the energy storage unit and the vehicle operating condition, with the goal of minimizing the cost of electricity, and with the constraints of minimizing the impact on the lifespan of the energy storage unit, ensuring that the energy storage unit reaches the target SOC before departure, and that the energy storage unit of the vehicle with the earliest departure time reaches the target SOC first, the charging and discharging strategy of each vehicle is re-determined; The first time period is the period with off-peak electricity prices.

3. The vehicle power supply system according to claim 1, characterized in that, The BMS is also used to: during the second time period, if the energy storage unit meets the traction power requirements, control the energy storage unit to discharge; and during braking conditions, control the energy storage unit to recover braking energy and charge it through the traction inverter and the first bidirectional DC / DC module.

4. The vehicle power supply system according to claim 3, characterized in that, The BMS is also used to, in the third time period, if the SOC of the energy storage unit is detected to be less than the safe operation threshold, reduce the current threshold value corresponding to the braking energy recovery, and control the energy storage unit to recover braking energy for charging through the traction inverter and the first bidirectional DC / DC module; after the energy storage unit recovers braking energy, if the SOC of the energy storage unit is still less than the safe operation threshold, control the energy storage unit to charge through the four-quadrant module and the first bidirectional DC / DC module. The electricity price in the third period is higher than that in the second period.

5. The vehicle power supply system according to claim 1, characterized in that, The least impact on the lifespan of the energy storage unit includes at least one of the following: The number of charge-discharge cycles of the energy storage unit is within the specified threshold. When the temperature of the energy storage unit is greater than a first temperature threshold, the charging current of the energy storage unit is less than a first current threshold. When the temperature value is greater than the second temperature threshold, the discharge current of the energy storage unit is less than the second current threshold. The charging current of the energy storage unit is the minimum charging current.

6. The vehicle power supply system according to claim 1, characterized in that, Also includes: Transformer; the primary side of the transformer is used to receive a first power supply and a second power supply, the first power supply and the second power supply being AC power supply; The input terminal of the four-quadrant module is connected to the secondary side of the transformer; the input terminal of the four-quadrant module is also connected to the third power supply and the fourth power supply, which are DC power supplies; the four-quadrant module can be switched to be connected to the first power supply or the second power supply and convert AC power to DC power, or it can be switched to be connected to the third power supply or the fourth power supply and realize the function of DC-DC converter.

7. The vehicle power supply system according to claim 6, characterized in that, The four-quadrant module includes: a first switching device, a second switching device, a third switching device, a fourth switching device, a fifth switching device, a sixth switching device, a seventh switching device, an eighth switching device, a first diode, a second diode, a third diode, a fourth diode, a first capacitor, a second capacitor, a first switching circuit, and a second switching circuit; Wherein, the anode of the first switching device is connected to the anode of the fifth switching device and the first terminal of the first capacitor; the cathode of the fourth switching device is connected to the cathode of the eighth switching device; the cathode of the first switching device is connected to the anode of the second switching device; the anode of the third switching device is connected to the cathode of the second switching device, and the cathode of the third switching device is connected to the anode of the fourth switching device; the cathode of the fifth switching device is connected to the anode of the sixth switching device; the anode of the seventh switching device is connected to the cathode of the sixth switching device, and the cathode of the seventh switching device is connected to the anode of the eighth switching device; the cathode of the second switching device... The cathodes of the fourth, sixth, and eighth switching devices are connected to the power supply. The anode of the first diode is connected to the cathode of the second diode, the anode of the third diode, the cathode of the fourth diode, the second terminal of the first capacitor, and the first terminal of the second capacitor, respectively, and the cathode is connected to the anode of the second switching device. The anode of the second diode is connected to the cathode of the third switching device. The cathode of the third diode is connected to the anode of the sixth switching device. The anode of the fourth diode is connected to the cathode of the seventh switching device. The second terminal of the second capacitor is connected to the cathode of the eighth switching device. The first switching circuit is connected between the cathode of the second switching device and the cathode of the sixth switching device; The second switching circuit is connected to the cathode of the fourth switching device, the cathode of the sixth switching device, the cathode of the eighth switching device, and the power supply, and is used to switch the connection between the switching device and the power supply.

8. The vehicle power supply system according to claim 6, characterized in that, Also includes: A reactor is connected between the third power supply, the fourth power supply, and the four-quadrant module.

9. The vehicle power supply system according to claim 6, characterized in that, The first power supply is AC 25KV, the second power supply is AC 15KV, the third power supply is DC 1500V, and the fourth power supply is DC 3000V.

10. The vehicle power supply system according to claim 1, characterized in that, Also includes: An auxiliary converter has its input terminal connected to the output terminal of the four-quadrant module, and its output terminal connected to auxiliary electrical equipment.

11. The vehicle power supply system according to claim 10, characterized in that, Also includes: The bidirectional charger has its input terminal connected to the output terminal of the auxiliary converter, and its output terminal connected to the battery and DC load.

12. The vehicle power supply system according to claim 11, characterized in that, The bidirectional charger includes an AC-DC conversion module and a DC conversion module.

13. A vehicle power supply method, applied to the vehicle power supply system as described in any one of claims 1 to 12, characterized in that, The method includes: The BMS determines the charging and discharging strategy based on the electricity price information, the status information of the energy storage unit, and the vehicle operating conditions, with the goal of minimizing the electricity cost, minimizing the impact on the lifespan of the energy storage unit, and the energy storage unit reaching the target SOC in the first time period as constraints. The energy storage unit charges during the first time period and discharges during the second time period according to the charging and discharging strategy of the BMS.

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