An electrical architecture for electric vehicle battery packs capable of rapid charging

Abstract

The present invention relates to an electrical architecture of an electric vehicle battery pack capable of fast charging, comprising a battery, a charging switch, a discharging switch, a DC bus, an on-board charging unit and a DC fast charging interface. The three charging switches and the four discharging switches are all electrical switches. It is characterized in that: the battery unit has two battery modules, the on-board charging unit has two on-board charging ports, and the DC bus unit has two sets of DC bus bars; the discharge switch is used to turn off the charging switch conduction, the two battery modules are connected in series, and the DC fast charging interface is used to charge quickly; the charging switch is used to turn off the discharge switch conduction, the two battery modules are separated, and the two sets of DC bus bars are discharged independently (or in common or in parallel); after the car is parked, the discharge switch and the charging switch are all turned off, and the two battery modules can be charged slowly through two on-board charging ports. Its advantages: 1. Series high-voltage fast charging, discrete low-voltage safe discharge; 2. Power redundancy and power supply redundancy, easy drive redundancy, and active balancing.

Description

Technical Field

[0001] The invention relates to an electrical architecture of an electric vehicle battery pack capable of rapid charging, belonging to the technical field of electric vehicles. Background Art

[0002] The three core technologies of electric vehicles are multi-energy powertrain control system, motor and its drive system (referred to as power system), and battery and its management system (referred to as battery system).

[0003] The two key components of electric vehicles are the battery system and the power system. The battery system includes battery packs, electrical switches and battery management systems (BMS); the power system includes electric motors, motor drivers and reducers. The power system of electric vehicles is mainly divided into three types according to the number of motors used: single motor system, dual motor system and four motor system.

[0004] Most of the current electric vehicle battery systems are equipped with a battery pack. The battery pack adopts an integrated electrical architecture, that is, the charging and discharging are at the same bus voltage, and the switching control of charging and discharging is realized by an electrical switch. At present, the mainstream batteries used in electric vehicles are lithium-ion batteries, and lithium-ion batteries mainly have two types of cells: ternary lithium and lithium iron phosphate. A large number of cells are connected in parallel and series to form a matrix structure, that is, multiple cells are first connected in parallel to form a single cell with the required Ah capacity, and then several single cells are connected in series to form a battery pack with the required kWh capacity. The functions of the battery management system (BMS) are: collecting parameters such as voltage, current and temperature of the battery cell, data transmission and storage, estimating battery capacity, overcharge / overdischarge / overload protection, charge and discharge control, balance control, insulation detection, thermal management, and data communication with the vehicle controller, motor controller and charging pile.

[0005] The national standard "GB / T 31466-2015 Voltage levels of high-voltage systems for electric vehicles" stipulates that the battery system can adopt six nominal voltage levels: 144V, 288V, 317V, 346V, 400V, and 576V. Correspondingly, the national standard "GB / T 18488.1-2015 Drive motor system for electric vehicles" stipulates that the DC bus voltage of the motor system can take the following levels: 36V, 48V, 60V, 80V, 120V, 144V * , 168V, 192V, 216V, 240V, 264V, 288V * 、312V * 、336V * , 360V, 384V *, 408V, 540V, 600V, 650V, 700V, 750V (marked with * are preferred levels). At the same time, in the national standard "GB / T 18487.1-2015 Electric Vehicle Conductive Charging System", four DC charging voltage levels are given: 200~500V, 350~700V, 500~950V, and above 950V (determined by the vehicle manufacturer and the power supply equipment manufacturer through consultation).

[0006] According to relevant statistics, the battery voltage of electric commercial vehicles is relatively higher than that of electric passenger vehicles, and the battery voltage of later-produced vehicles is higher than that of earlier-produced vehicles. At present, it has jumped from the initial 300V to 800V. The battery voltage of electric vehicles from different manufacturers or different models of the same manufacturer is also often different. Power systems close to 800V are mainly used in electric trucks and buses. Recently, internationally renowned car companies have successively launched passenger cars with 800V systems, such as: Mercedes-Benz ProjectOne, Porsche 919Hybrid and Mission, Audi AICON, Koenigsegg Regera, Fisker's E Motion, etc.

[0007] The same is true for DC charging piles, that is, the output voltage of later construction is higher than that of earlier construction; the earlier ones are compatible from 200V to 500V, and the later ones have been compatible from 200V to 750V, and will develop towards 950V and higher voltages in the future.

[0008] The two main factors affecting the development of electric vehicles are driving range and charging time. The first problem (driving range) has been solved (the energy / power density of battery cells has been greatly improved, and the capacity of battery packs can meet the driving range of about 400km; companies such as CATL have mass-produced high-rate charging cells). The only problem that needs to be solved now is the problem of fast charging, which has even become the focus of a new round of technological competition between China and foreign countries.

[0009] Recently, China and Japan have jointly formulated charging standards to achieve high-power charging. The main technical indicators for high-power charging have been initially proposed, with a charging voltage of 800V to 1000V, a charging current of 125A to 250A without cooling, and a charging power of ≥120kW; a charging current of 400A to 500A with cooling, and a charging power of ≥320kW. From the perspective of technical standards, high-power charging has a relatively clear dividing line, that is, the charging current standard is defined at around 250A. European and American companies plan to first achieve high-power charging of more than 150kW around 2018, and high-power charging of 350kW and above around 2020.

[0010] It can be seen that the development goal of DC high-power charging for electric vehicles is to charge the battery pack with a charging power of 350kW or above, charge (80-90)% of the power in 10-15 minutes, and charge the battery pack in a single-gun conduction mode. Then, the purpose of increasing the voltage of the battery pack for electric vehicles is to charge quickly. Although the 800V power system can achieve fast charging, its disadvantages are also very obvious: first, the insulation problem is a challenge; secondly, the increase in voltage leads to an increase in the size of the motor and electrical components (for example, the size of the motor driver may increase by 10%); thirdly, this is a new concept for passenger cars, and all core components need to be redesigned; in addition, there are few companies that can provide 800V related components, and the industrial chain needs to be redeveloped.

[0011] In short, the wide range of battery voltage and the tendency towards high voltage pose great risks to the insulation safety of electric vehicles, and bring great disadvantages to the development and standardization of core components such as drivers and motors, as well as the development of the entire industrial chain. At the same time, it also seriously affects the charging efficiency, final design, mutual compatibility, development and construction, and operation and maintenance of charging piles.

[0012] In summary, the development of the electric vehicle industry not only relies on the three core technologies, but also requires the coordinated compatibility and synchronous development of charging technology and facility construction. How to solve the problems of fast charging and insulation safety of electric vehicles, solve the situation where car companies, charging pile companies and charging facility construction units cannot develop in a standardized and coordinated manner, and promote the healthy development of the industrial chain are key issues for my country to achieve electric vehicle overtaking and become an automobile power. Summary of the invention

[0013] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and design an electrical architecture for an electric vehicle battery pack that can be quickly charged, which can satisfactorily solve the problems of fast charging and safe operation of electric vehicles, the development of the industrial chain, and the coordination and compatibility of electric vehicles and charging piles; it can be universally applicable to electric passenger cars and commercial vehicle series, and can be used for single-motor and multi-motor topologies; it unifies and standardizes the (battery / drive / motor / charging) voltage platform, complies with the existing relevant national standards, in order to become the industry standard and national standard for the electrical architecture of electric vehicle battery packs.

[0014] The technical solution of the present invention is as follows:

[0015] An electrical architecture of an electric vehicle battery pack capable of rapid charging, comprising a battery unit (1), a charging switch unit (2), a discharging switch unit (3), a DC bus unit (4), an on-board charging unit (5) and a DC fast charging interface (6). The charging switch unit (2) comprises a switch K01, a switch K02 and a switch K03, and the discharging switch unit (3) comprises a switch K11, a switch K12, a switch K21 and a switch K22; the switches K01, K02, K03 and the switches K11, K12, K21 and K22 are all electrical switches, using a DC contactor, and having two electrical terminals, respectively referred to as a front end and a rear end. The battery unit (1) has two battery modules, namely a battery module ① and a battery module ②, and the two battery modules have the same cell model, number of strings and capacity. The DC bus unit (4) has two sets of DC buses, namely a DC bus ① and a DC bus ②. The vehicle-mounted charging unit (5) has two vehicle-mounted charging ports, namely, vehicle-mounted charging port ① and vehicle-mounted charging port ②. The connection relationship is: the positive and negative poles of the battery module ① are respectively connected to the positive and negative poles of the vehicle-mounted charging port ①, and the positive and negative poles of the battery module ② are respectively connected to the positive and negative poles of the vehicle-mounted charging port ②. The positive pole of the battery module ① is connected to the rear end of the switch K01, and the front end of the switch K01 is connected to the positive pole of the DC fast charging interface (6); the negative pole of the battery module ① is connected to the front end of the switch K03, and the rear end of the switch K03 is connected to the positive pole of the battery module ②; the negative pole of the battery module ② is connected to the front end of the switch K02, and the rear end of the switch K02 is connected to the negative pole of the DC fast charging interface (6). The positive pole of the battery module ① is connected to the front end of the switch K11, and the rear end of the switch K11 is connected to the positive pole of the DC bus ①; the negative pole of the battery module ① is connected to the front end of the switch K12, and the rear end of the switch K12 is connected to the negative pole of the DC bus ①. The positive pole of battery module ② is connected to the front end of switch K21, and the rear end of switch K21 is connected to the positive pole of DC bus ②; the negative pole of battery module ② is connected to the front end of switch K22, and the rear end of switch K22 is connected to the negative pole of DC bus ②. There are three types of connection relationships between DC bus ① and DC bus ②: the first is independent, that is, DC bus ① and DC bus ② have no direct electrical connection; the second is common ground, that is, the negative pole of DC bus ① is connected to the negative pole of DC bus ②, and the positive pole of DC bus ① is not connected to the positive pole of DC bus ②; the third is parallel connection, that is, the negative pole of DC bus ① is connected to the negative pole of DC bus ②, and the positive pole of DC bus ① is connected to the positive pole of DC bus ②.

[0016] The on-board charging unit (5) is used for the on-board charger to slowly charge the battery unit (1). The DC fast charging interface (6) is used for the DC charging pile to quickly charge the battery unit (1). The charging switch unit (2) and the discharging switch unit (3) are used for switching control and on-off control of the charging and discharging states of the battery unit (1). The DC bus ① and the DC bus ② of the DC bus unit (4) can each carry 1 or 2 motor drivers. When each carries 2 motor drivers, it is suitable for a four-motor power system. When each carries 1 motor driver, it is suitable for a dual-motor power system and a single-motor power system; for a single-motor power system, the two motor drivers can drive one motor in parallel, or they can "jointly" drive a dual three-phase or six-phase motor (that is, each motor driver drives a set of three-phase windings). If two sets of DC bus bars are connected in parallel, they can jointly carry 1, 2, or 4 motor drivers, which are respectively suitable for single-motor, dual-motor, and four-motor power systems.

[0017] When the electric vehicle is in a driving state, the switches (K01, K02, K03) of the charging switch unit (2) are turned off, and the switches (K11, K12, K21, K22) of the discharging switch unit (3) are turned on, so that the two battery modules of the battery unit (1) are separated and powered by two sets of DC buses in an independent, common or parallel manner at a relatively low voltage (i.e., the battery module voltage). Therefore, it is convenient to better achieve electrical insulation and improve operational safety. It is also possible to achieve power redundancy and power supply redundancy, thereby improving operational reliability. By adjusting the output power difference of the motor drivers on the two DC buses (or time-sharing operation), active balancing of the two battery modules during the discharge process can be achieved.

[0018] When the electric vehicle is in a fast charging state, the switches (K11, K12, K21, K22) of the discharge switch unit (3) are turned off, and the switches (K01, K02, K03) of the charging switch unit (2) are turned on, so that the two battery modules of the battery unit (1) are connected in series and charged together by the DC fast charging interface (6) at a relatively high voltage (i.e., twice the battery module voltage). Therefore, it is conducive to fast charging, and the charging power is doubled for the same charging current. When the electric vehicle is in a slow charging state, the switches of the charging switch unit (2) and the discharge switch unit (3) are all turned off, and the two battery modules are independently slow-charged by the two on-board charging ports. By adjusting the charging power difference of the two on-board charging ports, active balancing of the two battery modules during the slow charging process can be achieved.

[0019] When the electric vehicle is in a parking state, the switches (K11, K12, K21, K22) of the discharge switch unit (3) and the switches (K01, K02, K03) of the charge switch unit (2) are all turned off, and the two battery modules are completely independently isolated to achieve electrical safety.

[0020] The nominal voltage of the battery module of the battery unit (1) can preferably be 400V as recommended by the national standard GB / T 31466-2015; corresponding to the DC bus voltage level of 384V recommended by the national standard GB / T 18488.1-2015 * , 408V. Based on this, the most mature and common 600-650V power semiconductor devices can be used to design motor drivers. When the battery modules are charged in series, the nominal voltage value is 800V, which meets the high-power charging voltage platform conditions and corresponds to the DC charging voltage level of 500-950V in the national standard GB / T 18487.1-2015. For this electrical architecture, the output voltage level of the high-power DC charging pile should be 500V-950V, which is conducive to high-efficiency and fast charging, and improves the versatility and standardization of the charging pile.

[0021] This electrical architecture is common to electric passenger cars and commercial vehicles, and is applicable to single-motor and multi-motor power systems. The electric motor can be an AC asynchronous motor, a permanent magnet synchronous motor, or other new motors.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The electrical architecture adopts "series charging and discrete discharge" of battery modules. It has the dual advantages of fast charging (relatively high voltage) and standard power supply (relatively low voltage); it can achieve fast and efficient high-power charging, and improve electrical safety and reliability.

[0024] 2. The electrical architecture realizes power redundancy and power supply redundancy, which facilitates drive redundancy; it can also achieve active balancing between battery modules.

[0025] 3. The electrical architecture can unify and standardize the (battery / drive / motor / charging) voltage platform. Based on mature devices, technologies and insulation requirements, it is conducive to the standardization and serialization of battery packs, drives, motors and power platforms.

[0026] 4. This electrical architecture is universally applicable to electric passenger cars and commercial vehicles, and is applicable to single-motor and multi-motor topologies. It satisfactorily solves the problems of fast charging and safe operation of electric vehicles, and the problem of coordinated development of electric vehicles and charging piles. It is conducive to the development of the existing industrial chain and can become the industry standard and national standard for the electrical architecture of electric vehicle battery packs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the electrical architecture diagram of the existing electric vehicle battery pack. The voltage platform for charging and discharging a single battery pack is the same.

[0028] Figure 2This is an electrical architecture diagram of an electric vehicle battery pack that can be quickly charged. The battery modules are connected in series for charging and separately for discharging.

[0029] Figure 3 This is an electrical architecture diagram of an electric vehicle battery pack that can be quickly charged. The battery modules are charged in series and discharged at the same ground.

[0030] Figure 4 This is an electrical architecture diagram of an electric vehicle battery pack that can be quickly charged. The battery modules are charged in series and discharged in parallel.

[0031] In the figure, 1 is a battery unit, 2 is a charging switch unit, 3 is a discharging switch unit, 4 is a DC bus unit, 5 is an on-board charging unit, 6 is a DC fast charging interface; K01, K02, K03, K11, K12, K21, K22 are electrical switches. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings in accordance with the best embodiment.

[0033] like Figure 2 to Figure 4As shown, an electrical architecture of a battery pack for electric vehicles capable of fast charging is composed of a battery unit (1), a charging switch unit (2), a discharging switch unit (3), a DC bus unit (4), an on-board charging unit (5) and a DC fast charging interface (6). The charging switch unit (2) includes switches (K01, K02, K03), and the discharging switch unit (3) includes switches (K11, K12, K21, K22); the switch is an electrical switch, having two electrical terminals, referred to as the front end and the rear end (if one end is referred to as the front end, the other end is referred to as the rear end, for ease of explanation), and preferably adopts a DC contactor. It is characterized in that: the battery unit (1) has two battery modules (i.e., battery module ① and battery module ②), and the two battery modules have the same battery cell model, number of strings and capacity. The DC bus unit (4) has two sets of DC bus bars (i.e., DC bus bar ① and DC bus bar ②). The on-board charging unit (5) has two on-board charging ports (i.e., on-board charging port ① and on-board charging port ②). The connection relationship is as follows: the positive and negative electrodes of battery module ① are respectively connected to the positive and negative electrodes of vehicle-mounted charging port ①, and the positive and negative electrodes of battery module ② are respectively connected to the positive and negative electrodes of vehicle-mounted charging port ②. The positive electrode of battery module ① is connected to the rear end of switch K01, and the front end of K01 is connected to the positive electrode of DC fast charging interface (6); the negative electrode of battery module ① is connected to the front end of switch K03, and the rear end of K03 is connected to the positive electrode of battery module ②; the negative electrode of battery module ② is connected to the front end of switch K02, and the rear end of K02 is connected to the negative electrode of DC fast charging interface (6). The positive electrode of battery module ① is connected to the front end of switch K11, and the rear end of K11 is connected to the positive electrode of DC bus ①; the negative electrode of battery module ① is connected to the front end of switch K12, and the rear end of K12 is connected to the negative electrode of DC bus ①. The positive pole of battery module ② is connected to the front end of switch K21, and the rear end of K21 is connected to the positive pole of DC bus ②; the negative pole of battery module ② is connected to the front end of switch K22, and the rear end of K22 is connected to the negative pole of DC bus ②. The negative pole of DC bus ① and the negative pole of DC bus ② can be connected, that is, the two groups of DC buses are grounded (such as Figure 3 ); further, the positive electrode of the DC bus ① and the positive electrode of the DC bus ② can be connected, that is, two sets of DC buses are connected in parallel (such as Figure 4 ).

[0034] The on-board charging unit (5) is used for the on-board charger to slowly charge the battery unit (1). The DC fast charging interface (6) is used for the DC charging pile to quickly charge the battery unit (1). The charging switch unit (2) and the discharging switch unit (3) are used for switching control and on-off control of the charging and discharging states of the battery unit (1). The DC bus ① and the DC bus ② of the DC bus unit (4) can each carry 1 or 2 motor drivers. When each carries 2 motor drivers, it is suitable for a four-motor power system. When each carries 1 motor driver, it is suitable for a dual-motor power system and a single-motor power system; for a single-motor power system, the two motor drivers can drive one motor in parallel, or they can "jointly" drive a dual three-phase or six-phase motor (that is, each motor driver drives a set of three-phase windings). If two sets of DC bus bars are connected in parallel, they can jointly carry 1, 2, or 4 motor drivers, which are respectively suitable for single-motor, dual-motor, and four-motor power systems.

[0035] When the electric vehicle is in a driving state, the switches (K01, K02, K03) of the charging switch unit (2) are turned off, and the switches (K11, K12, K21, K22) of the discharging switch unit (3) are turned on, so that the two battery modules of the battery unit (1) are separated and connected independently (such as Figure 2 ) or common ground (such as Figure 3 ) or in parallel (such as Figure 4 ) to supply power at a relatively low voltage (i.e., battery module voltage). This facilitates better electrical insulation and improves operational safety. It can also achieve power redundancy and power supply redundancy to improve operational reliability. By adjusting the output power difference of the motor drivers on the two DC buses (or working in time-sharing mode), active balancing of the two battery modules during discharge can be achieved.

[0036] When the electric vehicle is in a fast charging state, the switches (K11, K12, K21, K22) of the discharge switch unit (3) are turned off, and the switches (K01, K02, K03) of the charging switch unit (2) are turned on, so that the two battery modules of the battery unit (1) are connected in series and charged together by the DC fast charging interface (6) at a relatively high voltage (i.e., twice the battery module voltage). Therefore, it is conducive to fast charging, and the charging power is doubled for the same charging current. When the electric vehicle is in a slow charging state, the switches of the charging switch unit (2) and the discharge switch unit (3) are all turned off, and the two battery modules are independently slow-charged by the two on-board charging ports. By adjusting the charging power difference of the two on-board charging ports, active balancing of the two battery modules during the slow charging process can be achieved.

[0037] When the electric vehicle is in a parking state, the switches (K11, K12, K21, K22) of the discharge switch unit (3) and the switches (K01, K02, K03) of the charge switch unit (2) are all turned off, and the two battery modules are completely independently isolated to achieve electrical safety.

[0038] The nominal voltage of the battery module of the battery unit (1) can preferably be 400V as recommended by the national standard GB / T 31466-2015; corresponding to the DC bus voltage level of 384V recommended by the national standard GB / T 18488.1-2015 * , 408V. Based on this, the most mature and common 600-650V power semiconductor devices can be used to design motor drivers. When the battery modules are charged in series, the nominal voltage value is 800V, which meets the high-power charging voltage platform conditions and corresponds to the DC charging voltage level of 500-950V in the national standard GB / T 18487.1-2015. For this electrical architecture, the output voltage level of the high-power DC charging pile should be 500V-950V, which is conducive to high-efficiency and fast charging, and improves the versatility and standardization of the charging pile.

[0039] Battery module design example: If a ternary lithium-ion battery cell (nominal voltage 3.7V, voltage range 2.8V ~ 4.25V) is selected, the battery module uses 108 (or 112) battery cells in series and a nominal voltage of 400V (or 410V); if a lithium iron phosphate battery cell (nominal voltage 3.2V, voltage range 2.5V ~ 3.65V) is selected, the battery module uses 126 (or 128) battery cells in series and a nominal voltage of 400V (or 410V).

[0040] This electrical architecture is common to electric passenger cars and commercial vehicles, and is applicable to single-motor and multi-motor power systems. The electric motor can be an AC asynchronous motor, a permanent magnet synchronous motor, or other new motors.

Claims

1. An electrical architecture of a battery pack for an electric vehicle capable of fast charging, comprising a battery unit (1), a charging switch unit (2), a discharging switch unit (3), a DC bus unit (4), an on-board charging unit (5) and a DC fast charging interface (6); the charging switch unit (2) comprises a switch K01, a switch K02 and a switch K03, and the discharging switch unit (3) comprises a switch K11, a switch K12, a switch K21 and a switch K22; the switches K01, K02, K03 and the switches K11, K12, K21 and K22 are all electrical switches, using a DC contactor, and having two electrical terminals, respectively referred to as a front end and a rear end; the characteristics are: The battery unit (1) has two battery modules, namely, battery module ① and battery module ②, and the two battery modules have the same battery cell model, number of strings and capacity; the DC bus unit (4) has two sets of DC bus bars, namely, DC bus bar ① and DC bus bar ②; the on-board charging unit (5) has two on-board charging ports, namely, on-board charging port ① and on-board charging port ②; the connection relationship is: the positive pole and negative pole of the battery module ① are respectively connected to the positive pole and negative pole of the on-board charging port ①, and the positive pole and negative pole of the battery module ② are respectively connected to the positive pole and negative pole of the on-board charging port ②; the positive pole of the battery module ① is connected to the rear end of the switch K01, and the front end of the switch K01 is connected to the positive pole of the DC fast charging interface (6); the negative pole of the battery module ① is connected to the front end of the switch K03, and the rear end of the switch K03 is connected to the positive pole of the battery module ②; the negative pole of the battery module ② is connected to the front end of the switch K02, and the rear end of the switch K02 is connected to the negative pole of the DC fast charging interface (6) ; The positive pole of battery module ① is connected to the front end of switch K11, and the rear end of switch K11 is connected to the positive pole of DC bus ①; the negative pole of battery module ① is connected to the front end of switch K12, and the rear end of switch K12 is connected to the negative pole of DC bus ①; the positive pole of battery module ② is connected to the front end of switch K21, and the rear end of switch K21 is connected to the positive pole of DC bus ②; the negative pole of battery module ② is connected to the front end of switch K22, and the rear end of switch K22 is connected to the negative pole of DC bus ②; there are three types of connection relationships between DC bus ① and DC bus ②: the first is independent, that is, DC bus ① and DC bus ② have no direct electrical connection; the second is common ground, that is, the negative pole of DC bus ① is connected to the negative pole of DC bus ②, and the positive pole of DC bus ① is not connected to the positive pole of DC bus ②; the third is parallel connection, that is, the negative pole of DC bus ① is connected to the negative pole of DC bus ②, and the positive pole of DC bus ① is connected to the positive pole of DC bus ②.

Images