Traction system circuit and power supply mode switching method thereof

Abstract

The present application discloses a traction system circuit and a power supply mode switching method thereof, wherein the traction system circuit includes: a high-voltage box, the high-voltage box includes a KMM contactor; a traction inverter module, one end of the traction inverter module is connected to the KMM contactor, the traction inverter module includes a DC / DC chopper module and an inverter module, and the DC / DC chopper module is integrated into the inverter module; a TCU traction controller, the TCU traction controller is connected to the traction inverter module and the high-voltage box respectively, the TCU traction controller detects high-voltage box data and traction inverter module data, and adjusts the KMM contactor state according to the high-voltage box data and traction inverter module data; an on-board energy storage module, the on-board energy storage module is connected to the DC / DC chopper module; the TCU traction controller determines whether the traction inverter module data and the high-voltage box data cross zero according to a dual closed-loop control algorithm based on a target current and a ramp function, and controls the KMM contactor to close or open to change the vehicle power supply mode.

Description

Technical Field

[0001] The present application relates to the technical field of urban rail vehicle traction systems, and in particular to a traction system circuit and a power supply mode switching method thereof. Background Art

[0002] Trams are the fastest-growing form of rail transit in the world today. They have the advantages of large capacity, low cost, low pollution, low energy consumption, punctual operation, high safety and beautiful appearance. They are an important carrier of urban transportation, urban and rural rail transit and tourist attractions.

[0003] Tramways offer flexible routes, requiring neither elevated, enclosed lines nor underground tunnels. They operate along urban arterials, densely populated areas, urban-rural intermodal routes, and scenic tourist routes. Tram lines often cross urban roads at grade, allowing for both separate and mixed right-of-way. Suburban lines, on the other hand, have relatively few intersections. Due to the complexity of surface routes and the need for aesthetic appeal, trams in areas with dense grade crossings often use onboard energy storage systems, such as batteries or supercapacitors, for power supply in areas without grid connections. In less critical areas, overhead grids are used for power supply, representing grid connections.

[0004] In areas with grid power, the grid provides power to the vehicle's traction and auxiliary power systems via pantographs. Simultaneously, when the energy storage system's capacity is insufficient, it draws power from the grid via charging equipment to meet operational power needs in areas without grid power. In areas without grid power, the pantograph is disconnected from the grid, and the vehicle's traction and auxiliary power systems are powered by an onboard energy storage system. This energy storage system can be a lithium battery, supercapacitor, or other device. Due to energy constraints, the vehicle can operate at a reduced load. Switching between onboard energy storage and grid power is both a key and challenging aspect of new energy vehicles.

[0005] Commonly used new energy vehicle circuit topologies such as Figure 1 As shown. The existing topology and switching method have the following disadvantages: low integration, requiring the use of a separate bidirectional DC / DC conversion device, and the converter is independent of the energy storage system and traction system. The interconnection lines between the DC / DC controller, BMS, and TCU are complex, making reliable integrated control impossible. Before the vehicle switches the power supply mode, the high-voltage power supply of the traction system and auxiliary power system is shut down and restarted after the switch is completed. The vehicle's dynamic performance is limited, and the shutdown of the on-board air conditioner and other equipment affects passenger comfort. The pantograph needs to be lowered, which may cause arcing and damage to the pantograph and contact network, affecting its service life. Frequent VVVF pre-charging actions increase the system's failure rate and reduce the life of the contactor. The existing technology proposes methods for entering and leaving the grid, but only proposes entry and exit timing without any substantive methods. The only reduced power operation also has many limitations in actual operation, and there is a risk of accidents such as impact and short circuit caused by the large voltage difference between the grid and the battery.

[0006] The current power supply mode conversion technology for new energy vehicles has its limitations, which restricts the further promotion of new energy systems in rail transit. The DC-DC converter and VVVF cannot effectively form an integrated whole. The power supply interruption during switching affects train power and passenger comfort. The frequent switching action reduces the service life of the device. Some seamless switching methods cannot solve the existing problems.

[0007] Therefore, an effective method to solve the seamless switching between tram energy storage systems and grid power supply has become more urgent. Summary of the Invention

[0008] The embodiments of the present application provide a traction system circuit and a power supply mode switching method thereof, which at least solve the problems of low traction system integration, vehicle power performance limitation caused by vehicle power supply mode switching, high system failure rate and short contactor life.

[0009] The present invention provides a traction system circuit and a power supply mode switching method thereof, wherein the traction system circuit includes:

[0010] A high-voltage box, comprising a KMM contactor;

[0011] A traction converter module, one end of which is connected to the KMM contactor. The traction converter module includes a DC / DC chopper module and an inverter module, and the DC / DC chopper module is integrated into the inverter module.

[0012] a TCU traction controller, the TCU traction controller being connected to the traction converter module and the high-voltage box, respectively, detecting high-voltage box data and traction converter module data, and adjusting the KMM contactor state according to the high-voltage box data and the traction converter module data;

[0013] An on-board energy storage module connected to the DC / DC chopper module;

[0014] When a vehicle enters an off-grid area from a grid-connected area, the DC / DC chopper module switches to a BOOST state or a BUCK state according to the vehicle state, and the grid and the on-board energy storage module supply power to the vehicle in parallel. The TCU traction controller determines whether the traction converter module data crosses zero based on the dual closed-loop control algorithm based on the target current and ramp function, and controls the KMM contactor to open based on the determination result. After the grid power supply is interrupted, the on-board energy storage module continues to supply power to the vehicle.

[0015] When the vehicle enters the grid-connected area from the off-grid area, the DC / DC chopper module is converted to a BOOST state or a BUCK state according to the vehicle state, the on-board energy storage module supplies power to the vehicle, and the TCU traction controller determines whether the traction converter module data and the high-voltage box data pass through the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function. After controlling the KMM contactor to close according to the judgment result, the power supply of the on-board energy storage module is interrupted, and the grid supplies power to the vehicle.

[0016] In the above-mentioned traction system circuit, the high-voltage box further includes:

[0017] Pantograph voltage sensor TV0, the pantograph voltage sensor TV0 is connected to the KMM contactor, the TV0 sensor collects the high-voltage box data and transmits the high-voltage box data to the TCU traction controller, the TCU traction controller transmits the high-voltage box data to the traction inverter module, wherein the high-voltage box data includes the pantograph voltage up.

[0018] In the above traction system circuit, the traction converter module further includes:

[0019] A network current sensor TA, wherein the network current sensor TA collects data of a first traction converter module, wherein the data of the first traction converter module includes an actual value in of a grid current;

[0020] The grid voltage sensor TV1 is connected to one end of the grid current sensor TA. The grid voltage sensor TV1 collects data of the second traction converter module. The data of the second traction converter module includes the actual value ufc of the FC voltage and the actual value un of the grid voltage.

[0021] In the above-mentioned traction system circuit, the DC / DC chopper module includes:

[0022] A current sensor CH is used to collect data of a third traction converter, wherein the data of the third traction converter includes a battery current ib.

[0023] In the above-mentioned traction system circuit, the DC / DC chopper module further includes a DC / DC driver, a current inner loop controller, a voltage control outer loop, a current control outer loop and a state conversion switch;

[0024] Mode switch S2 and target voltage selection switch S3;

[0025] One end of the current inner loop controller is provided with the DC / DC working mode switch S1 , the other end of the current inner loop controller is provided with an outer loop control mode switch S2 , and the current control outer loop is provided with the target voltage selection switch S3 .

[0026] The present invention also provides a power supply mode switching method, the power supply mode switching method comprising:

[0027] The steps of switching the grid power supply mode to the energy storage system power supply mode are as follows: when the vehicle enters the non-grid area from the grid area, the vehicle receives the signal indicating that the vehicle has entered the non-grid area, switches the DC / DC drive state to the BOOST state or the BUCK state according to the vehicle state, and then determines whether the actual grid current value in crosses the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function. The TCU traction controller controls the KMM contactor to open according to the first judgment result, thereby completing the switch from the grid power supply mode to the energy storage system power supply mode;

[0028] The steps of switching the energy storage system power supply mode to the grid power supply mode are as follows: when the vehicle enters the grid-connected area from the non-grid area, after the vehicle receives the signal of entering the grid-connected area from the non-grid area, the vehicle determines whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function; the TCU traction controller controls the KMM contactor to close it according to the second judgment result, and then determines whether the actual grid current value in passes through the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function; the TCU traction controller converts the DC / DC drive state to the BUCK state according to the third judgment result, thereby completing the conversion from the energy storage system power supply mode to the grid power supply mode.

[0029] In the above power supply mode switching method, the step of switching the grid power supply mode to the energy storage system power supply mode further includes:

[0030] When the vehicle is in the traction state or the inertia state, the KMM contactor is closed, the TCU traction controller converts the DC / DC drive state to the BOOST state via the DC / DC operating mode switch S1, enables the voltage control outer loop via the outer loop control mode switch S2, and sets the target voltage in the stable phase to the rated voltage via the target voltage selection switch S3. Then, according to the dual closed-loop control algorithm based on the target current and the ramp function, it is determined whether the actual grid current value in crosses the zero point. After the TCU traction controller controls the KMM contactor to open based on the first determination result, the conversion from the grid power supply mode to the energy storage system power supply mode is completed.

[0031] In the above power supply mode switching method, the step of switching the grid power supply mode to the energy storage system power supply mode further includes:

[0032] When the vehicle is in a braking state, the KMM contactor is closed, and the TCU traction controller converts the DC / DC drive state to the BUCK state through the DC / DC operating mode switch S1, enables the current control outer loop through the outer loop control mode switch S2, and sets the target voltage of the stable phase to the rated voltage through the target voltage selection switch S3. Then, the TCU traction controller determines whether the actual grid current value in crosses the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function. Based on the third judgment result, the TCU traction controller converts the DC / DC drive state to the BOOST state through the DC / DC operating mode switch S1, enables the voltage control outer loop through the outer loop control mode switch S2, and controls the KMM contactor to open, thereby completing the conversion from the grid power supply mode to the energy storage system power supply mode.

[0033] In the above power supply mode switching method, the step of switching the energy storage system power supply mode to the grid power supply mode further includes:

[0034] When the vehicle state is a traction state or an inertia state, the KMM contactor is opened, the TCU traction controller converts the DC / DC drive state to the BOOST state via the DC / DC operating mode switch S1, adopts the voltage control outer loop via the outer loop control mode switch S2, and adopts the pantograph voltage up as the target following voltage via the target voltage selection switch S3. A determination is made as to whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. After the TCU traction controller controls the KMM contactor to close based on the second determination result, a determination is made as to whether the actual grid current value in passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. After the TCU traction controller converts the DC / DC drive state to the BUCK state based on the third determination result, the transition from the energy storage system power supply mode to the grid power supply mode is completed.

[0035] In the above power supply mode switching method, the step of switching the energy storage system power supply mode to the grid power supply mode further includes:

[0036] When the vehicle is in the braking state, the DC / DC drive is switched to the BUCK state via the DC / DC operating mode switch S1, the current control outer loop is adopted via the outer loop control mode switch S2, and the pantograph voltage up is adopted as the target following voltage via the target voltage selection switch S3. A determination is made as to whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. After the TCU traction controller controls the KMM contactor to close based on the second determination result, a determination is made as to whether the actual grid current value in passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. Based on the third determination result, the TCU traction controller switches the DC / DC drive state to the BOOST state, thereby completing the transition from the energy storage system power supply mode to the grid power supply mode.

[0037] Compared with related technologies, the present invention proposes a traction system circuit and a power supply mode switching method thereof, deeply analyzes the characteristics of current hybrid power supply trains, and proposes an integrated new energy traction system electrical topology, which has a better integration level in the existing technology; the present invention fully considers the vehicle operation characteristics, and creatively proposes a method for seamless switching of train power supply modes under various states, which minimizes the impact on train performance; according to the vehicle operation state and the power supply seamless switching characteristics, a current / voltage dual-loop control algorithm based on the target mode is proposed, which integrates the traction system, DC / DC, energy storage system, and vehicle state into one to achieve overall control; considering the system stability during switching, a switching method to improve current impact is proposed, and a ramp function is used to make the target current cross the zero point within the effective time.

[0038] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0040] Figure 1 It is a circuit topology of a new energy vehicle according to the prior art of the embodiment of the present application;

[0041] Figure 2 is an integrated traction system circuit topology according to an embodiment of the present application;

[0042] Figure 3 is a control flow chart of a dual closed-loop control algorithm based on target current and ramp function according to an embodiment of the present application;

[0043] Figure 4 This is a flow chart of a handover strategy from a network area to a non-network area according to an embodiment of the present application;

[0044] Figure 5 This is a flow chart of a handover strategy from a no-network area to a network area according to an embodiment of the present application;

[0045] Figure 6 is a display diagram of a current ramp control function according to an embodiment of the present application;

[0046] Figure 7 This is a state switch conversion logic diagram when a network area enters a non-network area traction state according to an embodiment of the present application;

[0047] Figure 8 This is a state switch conversion logic diagram when a network area enters a non-network area braking state according to an embodiment of the present application;

[0048] Figure 9 This is a state switch conversion logic diagram when a no-network area enters a network area traction state according to an embodiment of the present application;

[0049] Figure 10 This is a logic diagram of the state switch conversion when the no-network area enters the braking state of the network area according to an embodiment of the present application.

[0050] Wherein, the accompanying drawings are marked as follows:

[0051] TV0: grid voltage sensor;

[0052] TA1: Network flow sensor;

[0053] KM1: main isolation contactor;

[0054] KMQ: IGBT electronic switch;

[0055] FL: filter reactor;

[0056] FC: filter support capacitor;

[0057] TV1: FC capacitor voltage sensor;

[0058] CTU: U-phase current sensor;

[0059] CTW: W-phase current sensor;

[0060] M: Traction motor. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0062] Obviously, the drawings described below are merely examples or embodiments of the present application. Those skilled in the art can, without inventive effort, apply the present application to other similar scenarios based on these drawings. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, changes in design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in this application.

[0063] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0064] Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the technical field to which this application belongs. The words "one", "a", "the" and the like used in this application do not indicate a limit on quantity and may indicate the singular or plural. The terms "include", "comprise", "have" and any variations thereof used in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units that are inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The word "multiple" used in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0065] The present invention proposes a traction system circuit and a power supply mode switching method thereof, which at least solves the problems of low traction system integration, vehicle power performance limitation caused by vehicle power supply mode switching, high system failure rate and short contactor life.

[0066] The following will illustrate the embodiments of the present application by taking the traction system circuit and its power supply mode switching method as an example.

[0067] Example 1

[0068] This embodiment provides a traction system circuit. Figure 2 , Figure 2 This is an integrated traction system circuit topology according to an embodiment of the present application, such as Figure 2 As shown, the traction system circuit includes:

[0069] High voltage box, which includes KMM contactor;

[0070] Traction converter module: one end of the traction converter module is connected to the KMM contactor. The traction converter module includes a DC / DC chopper module and an inverter module. The DC / DC chopper module is integrated into the inverter module.

[0071] TCU traction controller, TCU traction controller is connected to the traction converter module and high-voltage box respectively. TCU traction controller detects the high-voltage box data and traction converter module data, and adjusts the KMM contactor state according to the high-voltage box data and traction converter module data;

[0072] On-board energy storage module, connected to the DC / DC chopper module;

[0073] When a vehicle enters an off-grid area from a grid-connected area, the DC / DC chopper module switches to BOOST or BUCK mode based on the vehicle's status. The grid and on-board energy storage module supply power to the vehicle in parallel. The TCU traction controller uses a dual closed-loop control algorithm based on target current and ramp function to determine whether the traction converter module data crosses zero. Based on the judgment result, it controls the KMM contactor to open, and the grid power supply is interrupted. The on-board energy storage module continues to supply power to the vehicle.

[0074] When a vehicle enters a grid-connected area from an off-grid area, the DC / DC chopper module switches to BOOST or BUCK state according to the vehicle status, and the on-board energy storage module supplies power to the vehicle. The TCU traction controller determines whether the traction inverter module data and the high-voltage box data cross the zero point based on the dual closed-loop control algorithm based on the target current and ramp function. Based on the judgment result, the KMM contactor is controlled to close, and the power supply of the on-board energy storage module is interrupted, and the grid supplies power to the vehicle.

[0075] In an embodiment, the high voltage box further comprises:

[0076] Pantograph voltage sensor TV0, pantograph voltage sensor TV0 is connected to the KMM contactor, the TV0 sensor collects high-voltage box data and transmits the high-voltage box data to the TCU traction controller, the TCU traction controller transmits the high-voltage box data to the traction inverter module, where the high-voltage box data includes the pantograph voltage up.

[0077] In an embodiment, the traction converter module further comprises:

[0078] A network current sensor TA collects data from a first traction converter module, wherein the data from the first traction converter module includes an actual value in of a grid current;

[0079] The grid voltage sensor TV1 is connected to one end of the grid current sensor TA. The grid voltage sensor TV1 collects data of the second traction converter module. The data of the second traction converter module includes the actual value of the FC voltage ufc and the actual value of the grid voltage un.

[0080] In an embodiment, the DC / DC chopping module comprises:

[0081] A current sensor CH, the current sensor CH collects data of the third traction converter, wherein the data of the third traction converter includes a battery current ib;

[0082] The DC / DC chopper module also includes a DC / DC driver, a current inner loop controller, a voltage control outer loop, a current control outer loop and a state conversion switch;

[0083] Among them, the state conversion switch includes a DC / DC working mode switch S1, an outer loop control mode switch S2 and a target voltage selection switch S3;

[0084] Among them, one end of the current inner loop controller is provided with a DC / DC working mode switch S1, the other end of the current inner loop controller is provided with an outer loop control mode switch S2, and the current control outer loop is provided with a target voltage selection switch S3.

[0085] In a specific embodiment, Figure 2 As shown, the traction system circuit will consist of IGBT Q7, Q8, and FL2 forming a bidirectional buck / boost circuit. The DC / DC and traction three-phase inverter will be integrated into one power module and controlled by the TCU.

[0086] The high-voltage box consists of the pantograph voltage sensor TV0, bus contactor KMM, etc., and is controlled by the TCU;

[0087] The traction converter module, VVVF, consists of a network current sensor TA, a network voltage sensor TV1, an isolation contactor KM1, a pre-charge contactor KM2, a pre-charge resistor R1, an FC voltage sensor TV2, a line filter reactor FL1, a support filter capacitor FC, a BUCK / BOOST chopper circuit, an energy storage reactor FL2, an energy storage battery voltage sensor TV2, a three-phase inverter, and a controller TCU.

[0088] Among them, TCU controls the high-voltage box, DCDC, and inverter as a whole to achieve more efficient and safe power supply switching, energy storage system charging and discharging control, and traction transmission control, and has the hardware conditions for implementing efficient integrated control strategies.

[0089] The vehicle power supply of the present invention has two modes. The power grid supplies power to the traction system through a pantograph. The rated voltage is Un, and the fluctuation range is 0.7Un~1.3Un. The energy storage unit (voltage range is 0.2Un~0.6Un) stabilizes the output voltage through the DC / DC integrated in the traction inverter.

[0090] Example 2

[0091] Please refer to Figures 3 to 6 , Figure 3 is a control flow chart of a dual closed-loop control algorithm based on target current and ramp function according to an embodiment of the present application; Figure 4 This is a flow chart of a handover strategy from a network area to a non-network area according to an embodiment of the present application; Figure 5 This is a flow chart of a handover strategy from a no-network area to a network area according to an embodiment of the present application; Figure 6 : is a current ramp control function display diagram according to an embodiment of the present application. Figures 3 to 6 As shown, the power supply mode switching method of the invention is applicable to the above-mentioned high-voltage circuit system, and the power supply mode switching method includes:

[0092] The steps for switching from the grid power supply mode to the energy storage system power supply mode are as follows: When the vehicle enters the non-grid area from the grid area, after receiving the signal that the vehicle has entered the non-grid area, the DC / DC drive state is switched to the BOOST state or the BUCK state according to the vehicle state. Then, a dual closed-loop control algorithm based on the target current and the ramp function is used to determine whether the actual grid current value in crosses the zero point. The TCU traction controller controls the KMM contactor to open according to the first judgment result, completing the switch from the grid power supply mode to the energy storage system power supply mode.

[0093] The steps for switching the energy storage system power supply mode to the grid power supply mode are as follows: when the vehicle enters the grid-connected area from the non-grid area, after receiving the signal of entering the grid-connected area from the non-grid area, the vehicle determines whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through zero according to the dual closed-loop control algorithm based on the target current and ramp function. After the TCU traction controller controls the KMM contactor to close it according to the second judgment result, it determines whether the actual grid current value in passes through zero according to the dual closed-loop control algorithm based on the target current and ramp function. After the TCU traction controller switches the DC / DC drive state to the BUCK state according to the third judgment result, the conversion from the energy storage system power supply mode to the grid power supply mode is completed.

[0094] In an embodiment, the step of switching the grid power supply mode to the energy storage system power supply mode further includes:

[0095] When the vehicle is in the traction state or the inertia state, the KMM contactor is closed, and the TCU traction controller switches the DC / DC drive state to the BOOST state through the DC / DC working mode switch S1, enables the voltage control outer loop through the outer loop control mode switch S2, and sets the target voltage of the stable phase to the rated voltage through the target voltage selection switch S3. Then, the dual closed-loop control algorithm based on the target current and the ramp function is used to determine whether the actual value of the grid current in crosses the zero point. After the TCU traction controller controls the KMM contactor to open based on the first judgment result, the transition from the grid power supply mode to the energy storage system power supply mode is completed.

[0096] When the vehicle is in a braking state, the KMM contactor closes, and the TCU traction controller switches the DC / DC drive state to a BUCK state through the DC / DC working mode switch S1, enables the current control outer loop through the outer loop control mode switch S2, and sets the target voltage in the stable phase to the rated voltage through the target voltage selection switch S3. Then, the TCU traction controller determines whether the actual grid current value in crosses zero based on a dual closed-loop control algorithm based on the target current and a ramp function. Based on the third judgment result, the TCU traction controller switches the DC / DC drive state to a BOOST state through the DC / DC working mode switch S1, enables the voltage control outer loop through the outer loop control mode switch S2, and controls the KMM contactor to open, completing the transition from the grid power supply mode to the energy storage system power supply mode.

[0097] In specific implementations, before switching from the grid-connected area NET1 to the off-grid area EPT, the vehicle is initially powered by the grid. Contactors KMM, KM1, and KME are closed, and the vehicle is in one of the following states: traction, coasting, or braking. The network current TA varies depending on the vehicle's state. Before switching from the off-grid area EPT to the grid-connected area NET2, the vehicle is initially powered by the battery. Contactors KMM are open, KM1 and KME are closed, and the vehicle is in one of the following states: traction, coasting, or braking. The battery current CH varies depending on the vehicle's state: positive, negative, or no current. TV0 monitors the pantograph voltage in real time.

[0098] like Figure 4 As shown, the process steps for switching from the grid power supply mode to the energy storage system power supply mode are as follows:

[0099] Step 1: When a vehicle enters a non-networked area from a networked area, after receiving the signal indicating that the vehicle has entered a non-networked area, the vehicle switches the DC / DC driver state to BOOST or BUCK according to the vehicle state. If the vehicle state is traction or inertia, the DC / DC driver state is switched to BOOST. If the vehicle state is braking, the DC / DC driver state is switched to BUCK.

[0100] Step 2: A dual closed-loop control algorithm based on the target current and ramp function is used to determine whether the actual grid current value in has crossed zero. If it has crossed zero when the vehicle is in traction or inertia mode, the TCU traction controller controls the KMM contactor to open, completing the transition from grid power supply mode to energy storage system power supply mode. When the vehicle is in braking mode, the DC / DC drive state is switched to BOOST mode, and the KMM contactor is controlled to open, completing the transition from grid power supply mode to energy storage system power supply mode.

[0101] like Figure 5 As shown, the process steps for switching the energy storage system power supply mode to the grid power supply mode are as follows:

[0102] Step 1: When a vehicle enters a networked area from a non-networked area, after receiving the signal from the vehicle, the DC / DC driver state is switched to BOOST or BUCK according to the vehicle state. If the vehicle state is traction or inertia, the DC / DC driver state is switched to BOOST. If the vehicle state is braking, the DC / DC driver state is switched to BUCK.

[0103] Step 2: When the vehicle is in the traction or inertia state, the DC / DC BOOST state forward output control strategy with the FC voltage / TV1 grid voltage as the target is used to determine whether the target voltage difference between the second traction converter module data and the pantograph voltage UP crosses zero. When the vehicle is in the braking state, the DC / DC BUCK state reverse output control strategy with the FC voltage / TV1 grid voltage as the target is used to determine whether the target voltage difference between the second traction converter module data and the pantograph voltage UP crosses zero.

[0104] Step 3: If the zero point is exceeded, the TCU traction controller controls the KMM contactor to close it;

[0105] Step 4: A dual closed-loop control algorithm based on the target current and ramp function is used to determine whether the actual grid current value in crosses zero. If it does, the TCU traction controller switches the DC / DC drive state to the BUCK state, completing the transition from energy storage system power supply mode to grid power supply mode. If the vehicle is in the braking state, the TCU switches the DC / DC drive state to the BOOST state, completing the transition from energy storage system power supply mode to grid power supply mode.

[0106] The DC / DC converter is a bidirectional, non-isolated converter. When the BUCK converter steps down the voltage, it can draw power from the grid to charge the battery. The BOOST converter converts the low voltage of the battery into a high voltage that can be received by the VVVF / traction converter and AUX / auxiliary power supply. The main control parameters are the battery current CH, the battery voltage TV3, and the energy storage output voltage, namely the FC voltage TV2.

[0107] The dual closed-loop control algorithm based on target current and ramp function is used to control the target current TA. When entering the off-grid area from the grid, the target current ramp function is used to gradually reduce TA to 0, achieving a smooth and impact-free transition from zero grid current to battery power supply, and uninterrupted load power supply.

[0108] The DCDC BOOST state forward output control strategy targets the FC voltage / TV1 grid voltage. This is a dual-loop control algorithm based on the target ramp function voltage. This strategy controls the voltage difference between the FC voltage / TV1 grid voltage and the pantograph voltage TV0 to within -ΔU, meaning that the TV1 grid voltage is less than the TV0 pantograph voltage to prevent battery energy from backflowing into the grid. Setting ΔU to 40V satisfies this requirement.

[0109] The DCDC buck state input reverse control strategy targets the FC voltage / TV1 grid voltage. This strategy, a dual-loop control algorithm based on a target ramp function voltage, does not control the output voltage in the buck state. Instead, it raises or lowers the FC voltage / TV1 grid voltage by controlling the battery charging energy. When the battery charging energy exceeds the regenerative braking energy, the FC voltage / TV1 grid voltage is lowered; when the battery charging energy is less than the regenerative braking energy, the FC voltage / TV1 grid voltage is raised. This strategy maintains the voltage difference between the FC voltage / TV1 grid voltage and the pantograph voltage TV0 within -ΔU, meaning that the TV1 grid voltage is lower than the pantograph voltage TV0 to prevent battery energy from backflowing into the grid. A ΔU setting of 40V satisfies this requirement.

[0110] like Figure 3 As shown, Figure 3 is a control flow chart of a dual closed-loop control algorithm based on target current and ramp function according to an embodiment of the present application;

[0111] DC / DC control is the core of power switching. The TCU executes the traction algorithm while also implementing energy management strategies and energy storage system charging and discharging strategies. The DC / DC uses a current / voltage dual-loop control algorithm based on a target ramp function.

[0112] The control system uses a double closed loop system with the energy storage system current as the inner loop and the target current or voltage as the outer loop; the current inner loop can effectively improve the stability of the control system, suppress the fluctuation of battery charging and discharging, and improve the safety of battery use. b The current sensor CH collects the current; the outer loop is the final control target and is also the given value i of the inner loop. bref * ; Current control loop target value i nref * ,This link is a transient link and is only used as a power supply conversion stage to prevent the grid current from changing too fast and causing impact on the system;

[0113] The voltage control loop has two target values ​​u nref1 * 、u nref2 * ;u nref1 *It is the reference value for controlling the grid voltage when entering the grid area from the non-grid area. This reference value follows the pantograph voltage, i.e. u nref1 * =u p , pantograph voltage u p Detected by voltage sensor TV0, the actual value of grid voltage u n Detected by sensor TV1, the actual value of grid current i n Detected by sensor TA, the actual value of FC voltage u fc Detected by sensor TV1, it should be noted that when S1 of DCDC works in BUCK mode, that is, the train is in braking state, u n The size of i b Negatively correlated, i b The larger the u, the more energy is extracted from the FC. n and u fc Therefore, when designing PID, it is necessary to reverse the polarity of each deviation link; u nref2 * It is the FC voltage reference value after successfully entering the no-grid zone. The traction system and auxiliary power system are voltage source loads. The rated voltage in the traction phase is Un, and the rated voltage in the braking phase is 1.1Un. After completing the conversion and entering the stable state, it is necessary to control the stability of the FC voltage so that the traction system can operate with full functionality. Considering that a proper voltage increase can reduce system losses without affecting the performance of the traction system, and considering the optimal gain point of the BUCK, the present invention sets the reference target voltage u in the traction and braking states to nref2 * All are set to 1.1Un. When the power supply conversion is completed and the KMM contactor is opened, the system enters the u loop from the current loop. nref2 * The voltage loop is used as the reference to complete the conversion from current source to voltage source.

[0114] like Figure 6 As shown, Figure 6 This is a display diagram of the current ramp control function according to an embodiment of the present application; when the grid area enters the off-grid area and KMM is not turned on, the grid and energy storage system supply power to the load in parallel, and the DC / DC controller controls u n and u fc The grid current gradually increases and decreases until it reaches 0 and is completely taken over by the battery. In this process, the parallel voltage source conversion is too fast, which can easily lead to system oscillation and battery feeding to the grid, causing overcurrent fault and battery failure. The purpose of introducing the ramp function is to make the grid current i n Gradually and stably reach the "zero" point, Δi is generally ±20A to ensure that KMM is shut down with zero current.

[0115] The signal to enter the no-grid is usually sent 30m in advance. The ramp function needs to be completed at the highest speed and before entering the no-grid. The maximum speed of the tram is generally not more than 80km / s. The actual maximum grid current is 800A. Considering the system instruction transmission delay and DC / DC state conversion delay, the ramp function slope can be set to 1000A / s, leaving 0.5s for system response time. The control beat step is 1000 / n, where n is the beat number. It should be noted that during regenerative braking, the network current is i n Negative value, the beat step is reversed.

[0116] The off-grid area enters the grid area, and the KMM closes after zero-voltage control. n Follow u p The control system switches from the voltage outer loop to the current outer loop. The control strategy for the current outer loop is similar to that for entering a non-grid zone from a grid-connected area. The difference is that during this phase, the vehicle no longer enters the current outer loop when braking, because the battery can absorb regenerative energy without returning it to the grid.

[0117] Example 3

[0118] Please refer to Figures 7 to 10 , Figure 7 This is a state switch conversion logic diagram when a network area enters a non-network area traction state according to an embodiment of the present application; Figure 8 This is a state switch conversion logic diagram when a network area enters a non-network area braking state according to an embodiment of the present application; Figure 9 This is a state switch conversion logic diagram when a no-network area enters a network area traction state according to an embodiment of the present application; Figure 10 This is a state switch conversion logic diagram when the no-network area enters the braking state of the network area according to the embodiment of the present application. Figures 3 to 10 As shown, the state transition switch logic is as follows:

[0119] Among them, S1, S2, and S3 are state conversion switches of the control process. S1 is the DC / DC working mode switch. The selector value 1 represents the BOOST boost power supply state, the selector value 2 represents the BUCK buck charging state, and 0 represents the shutdown state. S2 is the outer loop control mode switch. The selector value 1 represents the use of the voltage loop, and the selector value 2 represents the use of the current loop. S3 is the target voltage selection switch in the voltage outer loop. The selector value 1 represents the use of the pantograph voltage u p As the target following voltage, the selector value 2 represents the use of the rated grid voltage as the target voltage in the stabilization phase.

[0120] like Figure 7 As shown, the state conversion switch logic when the network area enters the non-network area and traction is as follows:

[0121] At time t0, the vehicle is in a grid-connected area, the S1 switch is in the BUCK or BOOST state, the S2 switch is in the current mode or voltage mode, the S3 switch is in the Uref2 voltage reference mode, the KMM contactor is closed, the grid voltage up is normal, the battery current ib is normal, and the in grid current is normal;

[0122] At t1, the vehicle receives a signal from a networked area to a non-networked area, and the system starts switching;

[0123] From t1 to t2, the power supply mode begins to switch. The S1 switch is in a non-BUCK and BOOST state, i.e., it is gradually closed in preparation for switching. The S2 switch is in a non-current mode and voltage mode, i.e., it is gradually closed in preparation for switching. The S3 switch is in a non-Uref1 and Uref2 voltage reference mode, i.e., it is gradually closed in preparation for switching. The KMM contactor is closed, the grid voltage up is normal, the battery current ib gradually decreases to 0, and the grid current in is normal.

[0124] From t2 to t3, each switch delays and waits to ensure safe switching of the system;

[0125] From t3 to t4, the state switches start to switch, S1 is in the BOOST state, S2 is in the current mode, S3 is in the Uref2 voltage reference mode, the KMM contactor is closed, the grid voltage up is normal, the battery current ib is controlled to increase in a positive direction according to the current ramp control function to gradually take over the grid current, and the grid current in gradually decreases;

[0126] From t4 to t5, the switches in each state are maintained, with the S1 switch in the BOOST state, the S2 switch in the current mode, and the S3 switch in the Uref2 voltage reference mode. The KMM contactor is closed, the grid voltage up is normal, the battery current ib takes over the grid current, and the grid current in crosses the zero point in a positive and stable manner.

[0127] From t5 to t6, the state switches start to switch: S1 is in BOOST mode, S2 is in voltage mode, S3 is in Uref2 voltage reference mode, KMM contactor opens, grid voltage up is normal, battery current ib is in battery traction power supply state, grid current in is zero, and the transition from grid-connected area to non-grid-connected area is completed;

[0128] At t7, the power supply of the power grid is interrupted and the train officially enters the power-free zone;

[0129] Among them, it should be noted that if the battery capacity is insufficient, the traction system needs to operate at a reduced power during conversion.

[0130] like Figure 8 As shown, the switching logic when the grid area enters the non-grid area and brakes is as follows:

[0131] At time t0, the vehicle is in a grid-connected area, the S1 switch is in the BUCK or BOOST state, the S2 switch is in the current mode or voltage mode, the S3 switch is in the Uref2 voltage reference mode, the KMM contactor is closed, the grid voltage up is normal, the battery current ib is normal, and the in grid current is normal;

[0132] At t1, the vehicle receives a signal from a networked area to a non-networked area, and the system starts switching;

[0133] From t1 to t2, the power supply mode begins to switch. The S1 switch is in a non-BUCK and BOOST state, i.e., it is gradually closed in preparation for switching. The S2 switch is in a non-current mode and voltage mode, i.e., it is gradually closed in preparation for switching. The S3 switch is in a non-Uref1 and Uref2 voltage reference mode, i.e., it is gradually closed in preparation for switching. The KMM contactor is closed, the grid voltage up is normal, the battery current ib gradually decreases to 0, and the grid current in is normal.

[0134] From t2 to t3, each switch delays and waits to ensure safe switching of the system;

[0135] From t3 to t4, the state switches start to switch, S1 is in the BUCK state, S2 is in the current mode, S3 is in the Uref2 voltage reference mode, the KMM contactor is closed, the grid voltage up is normal, the battery current ib is controlled to increase negatively according to the current ramp control function to gradually take over the grid current, and the negative grid current in gradually decreases;

[0136] From t4 to t5, the switches in each state are maintained, with the S1 switch in the BUCK state, the S2 switch in the current mode, and the S3 switch in the Uref2 voltage reference mode. The KMM contactor is closed, the grid voltage up is normal, the battery current ib takes over the grid current, and the grid current in crosses the zero point stably in the negative direction.

[0137] From t5 to t6, the state switches start to switch, S1 switch is in BOOST state, S2 switch is converted to voltage mode, S3 switch is in Uref2 voltage reference mode, KMM contactor is open, grid voltage up is normal, battery current ib is in battery braking charging state, grid current in is zero, and the transition from grid-connected area to non-grid-connected area is completed;

[0138] At t7, the power supply of the power grid is interrupted and the train officially enters the power-free zone;

[0139] Among them, it should be noted that if the battery capacity is insufficient, the traction system needs to operate at a reduced power during conversion.

[0140] like Figure 9 As shown, the state switch conversion logic when the grid area enters the non-grid area and brakes is as follows:

[0141] At time t0, the vehicle is in a grid-connected area, the S1 switch is in the BUCK or BOOST state, the S2 switch is in the current mode or voltage mode, the S3 switch is in the Uref2 voltage reference mode, the KMM contactor is closed, the grid voltage up is normal, the battery current ib is normal, and the in grid current is normal;

[0142] At t1, the vehicle receives a signal from a networked area to a non-networked area, and the system starts switching;

[0143] From t1 to t2, the power supply mode begins to switch. The S1 switch is in a non-BUCK and BOOST state, i.e., it is gradually closed in preparation for switching. The S2 switch is in a non-current mode and voltage mode, i.e., it is gradually closed in preparation for switching. The S3 switch is in a non-Uref1 and Uref2 voltage reference mode, i.e., it is gradually closed in preparation for switching. The KMM contactor is closed, the grid voltage up is normal, the battery current ib gradually decreases to 0, and the grid current in is normal.

[0144] From t2 to t3, each switch delays and waits to ensure safe switching of the system;

[0145] From t3 to t4, the state switches start to switch, S1 is in the BUCK state, S2 is in the current mode, S3 is in the Uref2 voltage reference mode, the KMM contactor is closed, the grid voltage up is normal, the battery current ib is controlled to increase negatively according to the current ramp control function to gradually take over the grid current, and the negative grid current in gradually decreases;

[0146] From t4 to t5, the switches in each state are maintained, with the S1 switch in the BUCK state, the S2 switch in the current mode, and the S3 switch in the Uref2 voltage reference mode. The KMM contactor is closed, the grid voltage up is normal, the battery current ib takes over the grid current, and the grid current in crosses the zero point stably in the negative direction.

[0147] From t5 to t6, the state switches start to switch, S1 switch is in BOOST state, S2 switch is converted to voltage mode, S3 switch is in Uref2 voltage reference mode, KMM contactor is open, grid voltage up is normal, battery current ib is in battery braking charging state, grid current in is zero, and the transition from grid-connected area to non-grid-connected area is completed;

[0148] At t7, the power supply of the power grid is interrupted and the train officially enters the power-free zone;

[0149] Among them, it should be noted that if the battery capacity is insufficient, the traction system needs to operate at a reduced power during conversion.

[0150] like Figure 10 As shown, the state switch conversion logic when entering the grid area from the grid area and braking is as follows:

[0151] From t0 to t1, the vehicle is in the off-grid area, the S1 switch is in the BUCK state, the S2 switch is in the voltage mode, the S3 switch is in the Uref2 voltage reference mode, the KMM contactor is open, the grid voltage up returns to normal from 0, the battery current ib is normal, and the in grid current is 0;

[0152] At t1, the vehicle receives a signal from a no-network area to a network area, and the system starts switching;

[0153] From t1 to t2, the power supply mode starts to switch. The S1 switch is in the BUCK state, the S2 switch is in the voltage mode, and the S3 switch is in the Uref2 voltage reference mode ready for switching. The KMM contactor is open, the grid voltage up is normal, the battery current ib is normal, and the in grid current is 0.

[0154] From t2 to t3, the mode switches begin to transition. Switch S1 is in the BUCK state, switch S2 is in the voltage mode, and switch S3 switches to the Uref1 voltage reference mode. The KMM contactor opens, the grid voltage is normal, the battery current ib fluctuates with the reverse voltage control mode, the in grid current is 0, un gradually follows up, and ufc gradually follows up.

[0155] From t3 to t4, the switches in each state are maintained. Switch S1 is in the BUCK state, switch S2 is in the voltage mode, and switch S3 is in the Uref1 voltage reference mode. The KMM contactor is open, the grid voltage up is normal, the battery current ib fluctuates with the reverse voltage following control mode, the in grid current is 0, un is stable and follows up, and ufc is stable and follows up.

[0156] From t4 to t5, the state switches are switched. Switch S1 is in the BUCK state, switch S2 is in the current mode, and switch S3 is in the Uref1 voltage reference mode. The KMM contactor is closed, the grid voltage up is normal, and the battery current ib is controlled to decrease negatively according to the current ramp control function to be gradually taken over by the grid current. The grid current in passively increases negatively to take over the battery power supply. Un is clamped to up, and UFC is clamped to up.

[0157] From t5 to t6, all states are maintained. Switch S1 is in BOOST mode, switch S2 is in current mode, S3 is in Uref1 voltage reference mode, KMM contactor is closed, grid voltage up is normal, battery current ib is stable and passes through zero, grid current in is normal, un is clamped to up, and ufc is clamped to up.

[0158] From t6 to t7, the power supply of the power grid was restored and the train officially entered the grid-connected area.

[0159] In summary, the traction system circuit and power supply mode switching method proposed in the invention provide seamless switching of power supply modes for similar vehicle models, and are not limited to the form of energy storage systems such as supercapacitors, lithium batteries, hydrogen fuel, etc., providing an effective solution that will bring good economic and social benefits. The present invention deeply analyzes the integrated control strategy, proposes an integrated topological structure of the new energy train traction system, energy storage system, and vehicle system, integrates energy and power-related subsystems, and provides an integrated strategy implementation platform for solving the cooperative relationship between the vehicle coupled power supply system and the power system, which also promotes the reduction of equipment types and the freeing up of equipment space in the vehicle; the present invention finely controls the switching of vehicle power modes, and realizes free conversion in various scenarios such as traction, braking, coasting, switching from grid to no grid, and switching from no grid to grid. The vehicle runs smoothly and without impact, greatly improving the application scope of the hybrid power supply system in rail transit vehicles; accurately proposes a current / voltage dual-loop control algorithm based on the target mode, solves the difficulties of complex bidirectional DC / DC drive objects and changeable target modes, and realizes the internal stable operation of the integrated system and smooth switching of external vehicle power supply modes; the present invention improves system stability, improves the problem of current impact during switching, and proposes a control method using a ramp function to cross the target current "zero point", which has good practicality.

[0160] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be subject to the scope of protection of the appended claims.

Claims

1. A traction system circuit, characterized in that: The traction system circuit includes: A high-voltage box, comprising a KMM contactor; A traction converter module, one end of which is connected to the KMM contactor. The traction converter module includes a DC / DC chopper module and an inverter module, and the DC / DC chopper module is integrated into the inverter module. a TCU traction controller, the TCU traction controller being connected to the traction converter module and the high-voltage box, respectively, detecting high-voltage box data and traction converter module data, and adjusting the KMM contactor state according to the high-voltage box data and the traction converter module data; An on-board energy storage module, the on-board energy storage module being connected to the DC / DC chopper module; When a vehicle enters an off-grid area from a grid-connected area, the KMM contactor closes, the DC / DC chopper module switches to BOOST or BUCK mode according to the vehicle state, and the grid and the on-board energy storage module supply power to the vehicle in parallel. The TCU traction controller opens the KMM contactor based on the data from the high-voltage box and the traction converter module, interrupting the grid power supply and continuing to supply power to the vehicle with the on-board energy storage module. When the vehicle enters the grid-connected area from the off-grid area, the KMM contactor opens, the DC / DC chopper module switches to BOOST state or BUCK state according to the vehicle state, the on-board energy storage module supplies power to the vehicle, and the TCU traction controller closes the KMM contactor based on the high-voltage box data and the traction converter module data, the power supply of the on-board energy storage module is interrupted, and the grid supplies power to the vehicle; The high-voltage box also includes: Pantograph voltage sensor TV0, the pantograph voltage sensor TV0 is connected to the KMM contactor, the TV0 sensor collects the high-voltage box data and transmits the high-voltage box data to the TCU traction controller, the TCU traction controller transmits the high-voltage box data to the traction inverter module, wherein the high-voltage box data includes the pantograph voltage up.

2. The traction system circuit according to claim 1, characterized in that: The traction converter module further includes: A network current sensor TA, wherein the network current sensor TA collects data of a first traction converter module, wherein the data of the first traction converter module includes an actual value in of a grid current; The grid voltage sensor TV1 is connected to one end of the grid current sensor TA. The grid voltage sensor TV1 collects data of the second traction converter module. The data of the second traction converter module includes the actual value of the FC voltage ufc and the actual value of the grid voltage un.

3. The traction system circuit according to claim 1, characterized in that: The DC / DC chopping module includes: A current sensor CH is used to collect data of a third traction converter, wherein the data of the third traction converter includes a battery current ib.

4. The traction system circuit according to claim 1, characterized in that: The DC / DC chopping module also includes a DC / DC driver, a current inner loop controller, a voltage control outer loop, a current control outer loop and a state conversion switch; The state conversion switch includes a DC / DC working mode switch S1, an outer loop control mode switch S2 and a target voltage selection switch S3; One end of the current inner loop controller is provided with the DC / DC working mode switch S1 , the other end of the current inner loop controller is provided with an outer loop control mode switch S2 , and the current control outer loop is provided with the target voltage selection switch S3 .

5. A power supply mode switching method, characterized in that: Based on the traction system circuit according to claim 1, the power supply mode switching method includes: The steps of switching the grid power supply mode to the energy storage system power supply mode are as follows: when the vehicle enters the non-grid area from the grid area, the vehicle receives the signal indicating that the vehicle has entered the non-grid area, switches the DC / DC drive state to the BOOST state or the BUCK state according to the vehicle state, and then determines whether the actual grid current value in crosses the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function. The TCU traction controller controls the KMM contactor to open according to the first judgment result, thereby completing the switch from the grid power supply mode to the energy storage system power supply mode; The steps of switching the energy storage system power supply mode to the grid power supply mode are as follows: when the vehicle enters the grid-connected area from the non-grid area, after the vehicle receives the signal of entering the grid-connected area from the non-grid area, the vehicle determines whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function; the TCU traction controller controls the KMM contactor to close it according to the second judgment result, and then determines whether the actual grid current value in passes through the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function; the TCU traction controller converts the DC / DC drive state to the BUCK state according to the third judgment result, thereby completing the conversion from the energy storage system power supply mode to the grid power supply mode.

6. The power supply mode switching method according to claim 5, characterized in that: The step of switching the grid power supply mode to the energy storage system power supply mode further includes: When the vehicle is in the traction state or the inertia state, the KMM contactor is closed, the TCU traction controller converts the DC / DC drive state to the BOOST state via the DC / DC operating mode switch S1, enables the voltage control outer loop via the outer loop control mode switch S2, and sets the target voltage in the stable phase to the rated voltage via the target voltage selection switch S3. Then, according to the dual closed-loop control algorithm based on the target current and the ramp function, it is determined whether the actual grid current value in crosses the zero point. After the TCU traction controller controls the KMM contactor to open based on the first determination result, the conversion from the grid power supply mode to the energy storage system power supply mode is completed.

7. The power supply mode switching method according to claim 6, wherein: The step of switching the grid power supply mode to the energy storage system power supply mode further includes: When the vehicle is in a braking state, the KMM contactor is closed, and the TCU traction controller converts the DC / DC drive state to the BUCK state through the DC / DC operating mode switch S1, enables the current control outer loop through the outer loop control mode switch S2, and sets the target voltage of the stable phase to the rated voltage through the target voltage selection switch S3. Then, the TCU traction controller determines whether the actual grid current value in crosses the zero point according to the dual closed-loop control algorithm based on the target current and the ramp function. Based on the third judgment result, the TCU traction controller converts the DC / DC drive state to the BOOST state through the DC / DC operating mode switch S1, enables the voltage control outer loop through the outer loop control mode switch S2, and controls the KMM contactor to open, thereby completing the conversion from the grid power supply mode to the energy storage system power supply mode.

8. The power supply mode switching method according to claim 7, characterized in that: The step of switching the energy storage system power supply mode to the grid power supply mode further includes: When the vehicle state is a traction state or an inertia state, the KMM contactor is opened, the TCU traction controller converts the DC / DC drive state to the BOOST state via the DC / DC operating mode switch S1, adopts the voltage control outer loop via the outer loop control mode switch S2, and adopts the pantograph voltage up as the target following voltage via the target voltage selection switch S3. A determination is made as to whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. After the TCU traction controller controls the KMM contactor to close based on the second determination result, a determination is made as to whether the actual grid current value in passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. After the TCU traction controller converts the DC / DC drive state to the BUCK state based on the third determination result, the transition from the energy storage system power supply mode to the grid power supply mode is completed.

9. The power supply mode switching method according to claim 7, wherein: The step of switching the energy storage system power supply mode to the grid power supply mode further includes: When the vehicle is in the braking state, the DC / DC drive is switched to the BUCK state via the DC / DC operating mode switch S1, the current control outer loop is adopted via the outer loop control mode switch S2, and the pantograph voltage up is adopted as the target following voltage via the target voltage selection switch S3. A determination is made as to whether the target voltage difference between the second traction converter module data and the pantograph voltage up passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. After the TCU traction controller controls the KMM contactor to close based on the second determination result, a determination is made as to whether the actual grid current value in passes through the zero point based on the dual closed-loop control algorithm based on the target current and the ramp function. Based on the third determination result, the TCU traction controller switches the DC / DC drive state to the BOOST state, thereby completing the transition from the energy storage system power supply mode to the grid power supply mode.

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