CN100487970C - Multilayer distributed battery managing system based on CAN bus - Google Patents

Abstract

The multiple layers distribution type battery management system includes one upper layer battery management ECU (electric control unit) and multiple lower layer battery management ECUs. Characters are that connection between one upper layer battery management ECU and multiple lower layer battery management ECUs is realized through lower layer CAN bus network. The invented battery management system provides functions of estimating charged state of battery, controlling temperature of battery package through air-cooling, and balanced controlling consistency of battery parameters. Features of the invention are: compact connection between inside and outside, high anti-interference, and high reliability.

Description

A multi-layer distributed battery management system based on CAN bus

technical field

The invention belongs to a storage battery management system for electric vehicles, in particular to a distributed battery management system, in particular to a CAN bus-based multi-layer distributed battery management system.

Background technique

Facing the pressure of environmental pollution, global warming and energy shortage, governments and enterprises of various countries have invested a lot of manpower and material resources in the research and development of electric vehicles. The three types of electric vehicles currently being developed are pure electric vehicles, hybrid electric vehicles, and fuel cell electric vehicles. The storage battery will inevitably become the auxiliary or main energy source for electric vehicles. Commonly used power batteries include lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries. They have the characteristics of large capacity, small size, and good power performance, so they have become the first choice for electric vehicle research and development. Usually, 10 single batteries are connected in series to form a battery pack, and multiple battery packs are connected in series to form a battery pack (depending on the value of the high voltage on the vehicle). During the use of electric vehicles, overcharging and overdischarging of the battery will cause damage to the deterioration of battery performance and greatly reduce battery life. And how to use it safely and effectively according to the characteristics of the battery used, that is, the design of the battery management system BMS (Battery Management System), becomes the key. On the one hand, the BMS is responsible for real-time detection and control of the temperature of each battery pack in the battery pack. When the temperature of the battery pack is too high, the fan is driven to cool the battery pack. It is responsible for estimating the current battery capacity in real time, that is, the state of charge (SOC), and balancing the voltage of each battery pack, judging whether there is an abnormal battery unit, and sending an alarm signal. The accuracy of the SOC estimation method has become one of the bottlenecks in the research and development of electric vehicles, and no major breakthrough has been made worldwide.

Contents of the invention

The technical problem to be solved by the present invention is to provide a kind of optical fiber CAN (Control Area Network controller local area network) bus network interface with external other ECU (electronic control unit) communication, and the twisted pair CAN bus communication is used inside the system based on the CAN bus A multi-layer distributed battery management system to overcome the above-mentioned defects.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: the present invention includes an upper battery management ECU (electronic control unit) and a plurality of lower battery pack ECUs, in order to realize the detection of each battery pack voltage, the voltage output terminals of each battery pack It is connected to the voltage detection input terminal of the corresponding lower battery pack ECU. In order to realize the detection of the temperature of each battery pack, a temperature sensor is installed on each battery pack, and the output of each battery pack temperature sensor is connected to the temperature detection input terminal of the corresponding lower battery pack ECU. , the output end of the overall battery pack is also connected with a voltage sensor and a current sensor for detecting the output of the overall battery. The outputs of these two sensors are respectively connected with the voltage and current detection input ends of the upper battery management ECU. Its characteristics are: an upper layer The battery management ECU (electronic control unit) and multiple lower battery pack ECUs (electronic control units) are connected through the CAN bus network;

The above-mentioned upper battery management ECU is composed of a CAN1 chip (such as SJA1000), A/D (analog/digital) converter, clock and power-off protection circuit, and a DSP (digital signal processor) microcontroller embedded in CAN2, wherein the DSP The data bus D0-D7 of the microcontroller is respectively connected to the address/data bus AD0-AD7 of the CAN1 chip, and the real clock DS12887 chip is also an 8-bit address data bus time-division multiplexing device, and its read-write access method is the same as that of the SJA1000 in the system , also mount it on the peripheral I/O bus of the DSP. The real-time clock is mainly used to protect the SOC results in power failure and record the time to ensure the accuracy of the SOC algorithm. The DSP microcontroller communicates through the optical fiber CAN through the built-in CAN2 chip. The module outputs the control signal, the input terminal of the A/D converter is connected with the output terminal Us of the overall battery pack voltage sensor and the output terminal Ui of the current sensor, and the CAN1 chip communicates with the underlying CAN bus network in two directions;

The above-mentioned DSP microcontroller also outputs a fan control signal for battery cooling, and outputs a control signal for battery balancing control;

Each of the lower battery pack ECUs (Electronic Control Unit) is composed of a microcontroller P89C591 embedded in CAN3 and a photoelectric isolator. Among them, the six analog input terminals of the microcontroller P89C591 are connected to the voltage signals of each battery pack, and a data line is connected to The temperature measurement signal of the battery pack is connected, and its output communicates bidirectionally with the internal twisted pair lower layer CAN bus network through the embedded CAN3 through the photoelectric isolator;

The above-mentioned upper layer CAN bus network is an active optical fiber star network, and the lower layer CAN bus network is a twisted pair CAN bus network.

The present invention has an optical fiber CAN bus network interface for communication with other external ECUs; in order to realize the collection of battery characteristic parameters, a plurality of analog input ports are provided, which are respectively: the total voltage signal of the battery, the output current signal of the battery, and the voltage of each battery pack Signal, battery body surface temperature signal; in order to facilitate battery heat dissipation and realize battery fan control, a fan-controlled digital output port is set; in order to realize battery balance control, a balance control digital output port is set; battery management system hardware includes An upper battery management ECU (electronic control unit) and multiple lower battery ECUs (the number of lower ECUs is determined by the number of battery packs in the battery pack); the upper battery management ECU and multiple lower battery ECUs form an internal CAN network, The underlying twisted pair CAN bus network is used for communication. The upper layer battery management ECU communicates with other node ECUs through the upper layer optical fiber CAN network through the optical fiber CAN interface. Both the upper battery management ECU and the lower battery pack ECU use embedded microprocessors. The embedded microprocessor in the upper battery management ECU realizes the collection and A/D conversion of the total voltage and current information of the battery, and the battery SOC (battery state of charge) algorithm; the embedded processor in the lower battery pack ECU realizes the control of the battery pack. The voltage and temperature signals are A/D converted. The CAN bus-based multi-layer distributed battery management system of the present invention adopts CAN bus network communication for internal and external communication, so that the internal and external connections of the system are simple and have strong anti-interference performance. Because this system adopts the algorithm combining open circuit voltage and ampere-hour integration, it can estimate the remaining capacity SOC of the battery more accurately.

Description of drawings

Fig. 1 is a structural principle block diagram of an embodiment of the present invention.

Figure 2 is a circuit structure diagram of the upper battery management ECU.

Figure 3 is a circuit structure diagram of the lower battery pack ECU.

Fig. 4 is the circuit structure diagram of optical fiber CAN bus communication.

Figure 5 digital temperature sensor interface circuit diagram.

Fig. 6 is a flow chart of the SOC algorithm of the embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but these embodiments should not be construed as limiting the present invention.

The embodiment of the present invention shown in Figure 1, it has the optical fiber CAN interface that communicates with other ECU in the electric vehicle, in order to realize the collection of storage battery characteristic parameter, a plurality of analog quantity input ports are set, and they are respectively: storage battery total voltage signal , the output current signal of the battery, the voltage signal of each battery pack, and the surface temperature signal of each battery pack; in order to facilitate the heat dissipation of the battery and realize the control of the battery fan, a digital output port controlled by the fan is set; in order to ensure the consistency of the battery parameters, the battery Balance control, set a balance control digital output port.

The present invention includes an upper battery management ECU (electronic control unit) and 4 lower battery pack ECUs; the battery pack used in the present invention is composed of 24 battery packs. The system configures a lower battery pack ECU for every 6 battery packs to realize battery pack information detection, that is, the lower battery pack ECU ₁ -ECU ₄ . The 4 lower battery pack ECUs and the upper battery management ECU form a twisted pair CAN bus network. The upper battery management ECU has a dual CAN controller structure, one CAN1 controller and the lower battery pack ECU form the twisted pair CAN network inside the battery management system, and the other embedded CAN2 controller forms the vehicle optical fiber CAN bus with other ECUs in the vehicle Network, its network topology is star, the transmission medium is plastic optical fiber, and all CAN networks adopt CAN2.0B transmission protocol.

As shown in FIG. 2 , the upper battery management ECU of the embodiment of the present invention is mainly composed of a DSP control unit, an external CAN controller unit, an A/D sampling unit, a real-time clock and a power-down protection unit. The chip used by DSP is TMS320LF2407, the external expansion CAN1 control model is SJA1000, the 12-bit high-precision double-integral A/D converter ICL7109 is used for A/D, and the real-time clock and power-down protection are completed by chip DS12887. In this embodiment, the interfaces between the above three devices and the DSP all adopt the I/O bus access mode of the DSP. Among them, the reading and writing of the CAN1 controller SJA1000 and the real clock and the power-down protection adopt the chip DS12887, which adopts the method of timing simulation through the I/O port.

As shown in Fig. 3, the embedded microcontroller adopted by the lower battery pack ECU of the embodiment of the present invention is a P87C591 single-chip microcomputer, and its internal hardware integrates a CAN controller and an A/D analog-to-digital conversion module. Each battery pack ECU manages 6 battery packs, and its function is to measure the voltage and temperature information of the 6 battery packs, and send the information to the upper battery management ECU through the twisted pair CAN bus. The voltage of the 6-way battery pack is respectively connected to the 6-way A/D input port of the embedded microcontroller P87C591 after the voltage regulation circuit. The signal wires of the 6 temperature sensors are connected to the same I/O port of the embedded microcontroller P87C591.

As shown in Figure 4, the CAN2 controller integrated with the DSP chip in the upper battery management ECU and other ECUs in the vehicle form the upper optical fiber CAN bus network, and the communication medium uses plastic optical fiber. The TX end of the sending pin of the CAN2 controller enhances the driving capability through the 75451 chip, and then connects with the plastic optical fiber through the electro-optical conversion module HFBR1528. Other ECU signals are converted into electrical signals through optical fiber transmission through the photoelectric conversion module HFBR2528 and connected to the receiving pin RX of the CAN2 controller.

As shown in FIG. 5 , the temperature sensor used in the embodiment of the present invention is a one-line digital temperature sensor with a model number of DS18B20. The sensor has an accuracy of ±0.5°C and a temperature conversion result resolution of 0.0625°C in 12-bit mode. The sensor is simple to connect, and there are 3 wires in total, which are power wire, ground wire and data wire. In each lower battery pack ECUi, the temperature sensors on the six battery packs are hung on the I/O port of a single-chip microcomputer P89C591 at the same time, and are distinguished by the solidified ID of the chip. The use of the temperature sensor makes the connection between the battery and the management system simple.

As shown in FIG. 6 is a software flowchart of the SOC algorithm of the embodiment of the present invention. The SOC algorithm is divided into two parts in this embodiment. One part is to estimate the initial capacity value Cap of the SOC, that is, the capacity when the battery starts to work. The other part is to estimate the SOC value during battery work. Since the selected Ni-MH battery has a capacity of 12Ah, 12Ah is to discharge for 1 hour at a current of 12 amps. For the convenience of calculation, the total capacity of 12Ah is converted into CapO=43200 ampere seconds. Since the open circuit voltage of the battery in a steady state has a certain corresponding relationship with the SOC value. Define the SOC value: (1) Initial capacity estimation method: When the battery does not work within 12 hours, use the open circuit voltage to estimate the initial SOC capacity, otherwise use the SOC value saved before the last power failure as the initial capacity of the battery. (2) Dynamic capacity estimation method: When the battery is in the running state, the initial capacity is taken as the initial value of the battery capacity, and the dynamic capacity of the SOC is estimated by the ampere-hour integration method (or power accumulation method), and the power accumulation is performed every 200ms to determine the battery capacity. Current capacity for dynamic work.

According to actual tests, the battery management system of the embodiment of the present invention has simple internal and external connections, stable and reliable operation, and the SOC algorithm can estimate the SOC value more accurately.

The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims (8)

1. A multi-layer distributed battery management system based on CAN bus, including an upper-layer battery management ECU and multiple lower-layer battery pack ECUs. The voltage detection input terminal of the battery pack ECU is connected. In order to realize the detection of the temperature of each battery pack, a temperature sensor is installed on each battery pack, and the output of each battery pack temperature sensor is connected to the temperature detection input terminal of the corresponding lower battery pack ECU. The output terminal of the battery pack is also connected with a voltage sensor and a current sensor for detecting the output of the whole battery. The outputs of these two sensors are respectively connected with the voltage and current detection input terminals of the upper battery management ECU. It is characterized in that: an upper battery management ECU It is connected with multiple lower battery pack ECUs through the CAN bus network. 2. A multi-layer distributed battery management system based on CAN bus as claimed in claim 1, characterized in that: the upper battery management ECU consists of a CAN1 chip, A/D converter, clock and power-off protection circuit and A DSP microcontroller embedded in CAN2 is formed, and the clock and power-off protection circuit adopts the DS12887 chip, in which the data bus D0-D7 of the DSP microcontroller is respectively connected with the address/data bus AD0-AD7 of the CAN1 chip, and the DS12887 chip is 8 bits The device with time-division multiplexing of address data bus has the same read and write access mode as the CAN1 chip in the system. The DS12887 chip is also mounted on the peripheral I/O bus of the DSP. The DS12887 chip is mainly used for power-down protection SOC results and recording Time, to ensure the accuracy of the SOC algorithm, the DSP microcontroller outputs the control signal through the built-in CAN2 chip through the optical fiber CAN communication module, the input terminal of the A/D converter is connected with the output terminal Us of the overall battery pack voltage sensor and the output terminal Ui of the current sensor connected. 3. A multi-layer distributed battery management system based on CAN bus as claimed in claim 2, characterized in that: the DSP microcontroller also outputs a fan control signal for cooling the battery, and outputs a fan control signal for the battery Control signal for equalization control. 4. A multi-layer distributed battery management system based on CAN bus as claimed in claim 1, characterized in that: each lower battery pack ECU is composed of a microcontroller embedded in CAN3 and a photoelectric isolator, wherein the microcontroller The analog input terminal of the controller is connected to the voltage signal of each battery pack, a data line is connected to the temperature measurement signal of the battery pack, and the output of the microcontroller communicates bidirectionally with the lower CAN bus network through the embedded CAN3 through the photoelectric isolator. 5. A multi-layer distributed battery management system based on CAN bus as claimed in claim 2, characterized in that: the transmission pin TX end of the CAN2 chip of the upper ECU optical fiber CAN network enhances the driving capability through the 75451 chip, and then After the electro-optical conversion module HFBR1528 is connected to the plastic optical fiber, other ECU signals are transmitted through the optical fiber and converted into electrical signals through the photoelectric conversion module HFBR2528, and then connected to the receiving pin RX of the CAN2 chip. 6. A multi-layer distributed battery management system based on CAN bus as claimed in claim 4, characterized in that: the temperature sensor adopts a digital temperature sensor, and the microcontroller embedded in CAN3 is an embedded microprocessor P89C591, The signal terminals of multiple temperature sensors are connected to the same I/O port of the embedded microprocessor P89C591. 7. A multi-layer distributed battery management system based on CAN bus as claimed in claim 2, characterized in that: the microcontroller DSP in the upper battery management ECU adopts an embedded DSP chip TMS320LF2407, and the CAN1 chip adopts external expansion SJA1000. 8. A multi-layer distributed battery management system based on CAN bus as claimed in claim 4, wherein the microcontroller embedded in CAN3 is a P87C591 single-chip microcomputer.

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