阅读说明：本技术 一种新能源汽车智能补电方法 (Intelligent electricity supplementing method for new energy automobile ) 是由 郝国庆 陈茜兵 徐嘉 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种新能源汽车智能补电方法,其特征在于：将车辆所处状态分为高压工作状态、低压供电状态、休眠状态,并分别为每种状态提供一种补电策略进行补电控制,并在补电控制策略下为蓄电池充电。本方案通过对车辆所处的各种工况均设置一种自动补电策略,保证了车辆在任何工况下均可以可靠有效的补电,保障了蓄电池电量的可靠补充。(The invention discloses an intelligent power supplementing method for a new energy automobile, which is characterized by comprising the following steps of: the state of the vehicle is divided into a high-voltage working state, a low-voltage power supply state and a dormant state, a power supply strategy is respectively provided for each state to carry out power supply control, and the storage battery is charged under the power supply control strategy. According to the scheme, an automatic power supply strategy is set for various working conditions of the vehicle, so that the vehicle can be reliably and effectively supplied with power under any working conditions, and the reliable supply of the electric quantity of the storage battery is guaranteed.)

1. The intelligent electricity supplementing method for the new energy automobile is characterized by comprising the following steps: the state of the vehicle is divided into a high-voltage working state, a low-voltage power supply state and a dormant state, a power supply strategy is respectively provided for each state to carry out power supply control, and the storage battery is charged under the power supply control strategy.

2. The intelligent power supplementing method for the new energy automobile according to claim 1, characterized in that: when the vehicle is in a high-voltage state, all controllers of the vehicle are awakened to work at the moment, the voltage of a low-voltage storage battery system is detected through a low-voltage detection module, and when the voltage of the low-voltage storage battery system is detected to be less than or equal to a first set threshold value U1, a slow charging relay closing instruction and a high-voltage instruction are issued, so that the DCDC module starts to work to intelligently supplement power for the low-voltage storage battery; when the voltage of the low-voltage battery system is detected to be larger than or equal to a second set threshold value U2, the DCDC stops working, the VCU issues a high-voltage instruction to the DCDC, issues a slow charging relay disconnection instruction to the BMS, and completes the power supplementing action.

3. The intelligent power supplementing method for the new energy automobile according to claim 1 or 2, characterized in that: when a vehicle is in a low-voltage power supply state, a VCU low-voltage detection module is used for detecting the voltage of a low-voltage storage battery system, when the voltage of the low-voltage storage battery system is detected to be less than or equal to a first set threshold value U1, the VCU detects the working states of the DCDC system, the power battery system and the whole vehicle state, if the states of the DCDC system, the power battery system and the whole vehicle are not faulted, the VCU sends a relay actuation instruction to the BMS, sends a high-voltage instruction to the DCDC system, and starts the DCDC system to supplement electric energy to the low-voltage storage battery system;

when the voltage of the low-voltage battery system is detected to be larger than or equal to a second set threshold value U2, the VCU issues a power-off instruction to the DCDC, the DCDC stops working, a relay-off instruction is issued to the BMS, and power supplement is completed.

4. The intelligent power supplementing method for the new energy automobile according to claim 1 or 2, characterized in that: the method comprises the following steps that when a vehicle is in a dormant state, the BMS utilizes a system clock to wake up the BMS regularly to detect the voltage of a low-voltage storage battery system, when the voltage of the low-voltage storage battery system is detected to be less than or equal to a third set threshold value U3, the BMS wakes up a VCU to work, after the VCU works, the DCDC is awakened, the VCU detects a DCDC system, a power battery system and a whole vehicle, if no fault exists, the VCU gives a relay actuation instruction to the BMS, actuates a DCDC loop relay, provides a high-voltage instruction to the DCDC, and starts the DCDC system to supplement electric energy to the low-voltage storage battery system; when the VCU detects that the voltage of the low-voltage storage battery system is larger than or equal to a second set threshold value U2, the VCU gives a power-off instruction to the DCDC, the DCDC stops working, the DCDC powers off, the DCDC loop relay is disconnected, the power supplement action is completed, and the BMS and the VCU enter the dormancy again.

5. The intelligent power supplementing method for the new energy automobile according to claim 4, characterized in that: the BMS utilizes the BMS to time in the BMS in dormancy, and automatically awakens the BMS after the timing time is reached.

6. The intelligent power supplementing method for the new energy automobile according to claim 4 or 5, characterized in that: after the vehicle is powered off and the BMS receives a power-off command of the VCU, the BMS calculates the timing starting time and stores the timing starting time and then sleeps, and the BMS utilizes an internal clock to time after sleeping.

7. The intelligent power supplementing method for the new energy automobile according to claim 5 or 6, characterized in that: establishing a voltage-time equation of the low-voltage battery system according to the relation between the electric energy of the low-voltage battery and the static electric energy consumption of the vehicle, setting the voltage-time equation of the low-voltage battery system in the BMS, detecting the voltage of the low-voltage battery system before the BMS is dormant every time, calculating the time required by the voltage of the low-voltage battery system to reach the DCDC starting voltage according to the voltage-time equation of the low-voltage battery system, and then storing the calculated time plus a time threshold value in the BMS as the timing time.

8. The intelligent power supplementing method for the new energy automobile according to claim 7, characterized in that: if after the BMS is started regularly, when waking up the BMS and detecting that the voltage of the low-voltage battery system is greater than a first set threshold value, the BMS wakes up and starts according to a fixed time period mode to judge whether power supply is needed.

Technical Field

The invention relates to the field of new energy electric automobiles, in particular to an intelligent power supplementing method of a new energy electric automobile.

Background

The problems of environmental pollution and fossil energy consumption are puzzled to people day by day, the development and application of new energy industry can effectively improve the problems of environmental pollution and fossil fuel consumption, the new energy industry is greatly supported by the nation, the new energy industry is rapidly developed along with technological progress, the market proportion of new energy automobiles is on the rise in recent years, the proportion of new energy automobiles is gradually increased in the future, and the field of new energy automobiles is a new direction of automobile development.

New energy automobile and traditional fuel vehicle compare that new energy automobile is with electrical apparatus more to low pressure storage battery system's stability requirement higher, the stable power supply problem of low pressure storage battery also remains to promote, new energy automobile is more to the electric energy comparison reliance with electrical apparatus, if the vehicle does not have intelligent benefit electric control strategy, the vehicle does not use for a long time and causes the feed of low pressure battery system, the vehicle can't start, damage low pressure (12/24VDC) storage battery system, the operating mode of various cars is not fully considered in the new energy electric automobile benefit of prior art, can't satisfy the requirement of vehicle under different operating modes, based on time, this application designs a new electric automobile benefit electric strategy.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an electric automobile automatic power supplementing control method which is used for realizing automatic power supplementing of a vehicle under various working conditions.

In order to achieve the purpose, the invention adopts the technical scheme that: the intelligent power supplementing method for the new energy automobile divides the state of the automobile into a high-voltage working state, a low-voltage power supply state and a dormant state, provides a power supplementing strategy for each state respectively for power supplementing control, and charges a storage battery under the power supplementing strategy.

When the vehicle is in a high-voltage state, all controllers of the vehicle are awakened to work at the moment, the voltage of a low-voltage storage battery system is detected through a low-voltage detection module, and when the voltage of the low-voltage storage battery system is detected to be less than or equal to a first set threshold value U1, a slow charging relay closing instruction and a high-voltage instruction are issued, so that the DCDC module starts to work to intelligently supplement power for the low-voltage storage battery; when the voltage of the low-voltage battery system is detected to be larger than or equal to a second set threshold value U2, the DCDC stops working, the VCU issues a high-voltage instruction to the DCDC, issues a slow charging relay disconnection instruction to the BMS, and completes the power supplementing action.

When a vehicle is in a low-voltage power supply state, a VCU low-voltage detection module is used for detecting the voltage of a low-voltage storage battery system, when the voltage of the low-voltage storage battery system is detected to be less than or equal to a first set threshold value U1, the VCU detects the working states of the DCDC system, the power battery system and the whole vehicle state, if the states of the DCDC system, the power battery system and the whole vehicle are not faulted, the VCU sends a relay actuation instruction to the BMS, sends a high-voltage instruction to the DCDC system, and starts the DCDC system to supplement electric energy to the low-voltage storage battery system;

when the voltage of the low-voltage battery system is detected to be larger than or equal to a second set threshold value U2, the VCU issues a power-off instruction to the DCDC, the DCDC stops working, a relay-off instruction is issued to the BMS, and power supplement is completed.

The method comprises the following steps that when a vehicle is in a dormant state, the BMS utilizes a system clock to wake up the BMS regularly to detect the voltage of a low-voltage storage battery system, when the voltage of the low-voltage storage battery system is detected to be less than or equal to a third set threshold value U3, the BMS wakes up a VCU to work, after the VCU works, the DCDC is awakened, the VCU detects a DCDC system, a power battery system and a whole vehicle, if no fault exists, the VCU gives a relay actuation instruction to the BMS, actuates a DCDC loop relay, provides a high-voltage instruction to the DCDC, and starts the DCDC system to supplement electric energy to the low-voltage storage battery system; when the VCU detects that the voltage of the low-voltage storage battery system is larger than or equal to a second set threshold value U2, the VCU gives a power-off instruction to the DCDC, the DCDC stops working, the DCDC powers off, the DCDC loop relay is disconnected, the power supplement action is completed, and the BMS and the VCU enter the dormancy again.

The BMS utilizes the BMS to time in the BMS in dormancy, and automatically awakens the BMS after the timing time is reached.

After the vehicle is powered off and the BMS receives a power-off command of the VCU, the BMS calculates the timing starting time and stores the timing starting time and then sleeps, and the BMS utilizes an internal clock to time after sleeping.

Establishing a voltage-time equation of the low-voltage battery system according to the relation between the electric energy of the low-voltage battery and the static electric energy consumption of the vehicle, setting the voltage-time equation of the low-voltage battery system in the BMS, detecting the voltage of the low-voltage battery system before the BMS is dormant every time, calculating the time required by the voltage of the low-voltage battery system to reach the DCDC starting voltage according to the voltage-time equation of the low-voltage battery system, and then storing the calculated time plus a time threshold value in the BMS as the timing time.

If after the BMS is started regularly, when waking up the BMS and detecting that the voltage of the low-voltage battery system is greater than a first set threshold value, the BMS wakes up and starts according to a fixed time period mode to judge whether power supply is needed.

The invention has the advantages that: an automatic power supply strategy is set for various working conditions of the vehicle, so that the vehicle can be reliably and effectively supplied with power under any working conditions, and the power of the storage battery can be reliably supplied; under the condition of no fault, the states of the vehicle such as high voltage, dormancy, low voltage and the like are considered, and the power supply requirements of the vehicle under different conditions are ensured; the BMS automatic starting mode is adopted to automatically supplement power for the vehicle in the dormant state, so that the power can be supplemented in time when the vehicle is not used for a long time; adopt calculation mode to set up BMS awakening time, safe and reliable more can be effectual has guaranteed to start intelligent benefit electric program before the battery insufficient voltage.

Drawings

The contents of the expressions in the various figures of the present specification and the labels in the figures are briefly described as follows:

FIG. 1 is a schematic diagram of the VCU and BMS control power supplement of the present invention;

fig. 2 is a schematic diagram of the BDU control power supplement in the invention.

Detailed Description

The following description of preferred embodiments of the invention will be made in further detail with reference to the accompanying drawings.

The invention mainly relates to a new energy vehicle and an intelligent management strategy of a low-voltage storage battery system, realizes a dynamic self-adaptive voltage regulation function of the low-voltage storage battery system of the new energy vehicle, and mainly relates to four systems BMS (power battery management system), DCDC (high-low voltage direct current conversion system), VCU (vehicle control unit) and the low-voltage storage battery system. The power battery system supplies power to the high-voltage electric appliances of the whole vehicle, and the low-voltage battery system is mainly responsible for supplying working power to the low-voltage controller modules and the low-voltage electric appliances of all systems of the vehicle.

Example 1:

strategy one: (adopt VCU, BMS to carry on the systematic complementary electricity control)

Working condition 1:

vehicle high-pressure state: each control of the whole vehicle passes through self-checking, the whole vehicle works normally, the whole vehicle has no fault, a main positive relay and a main negative relay of the vehicle are attracted, the vehicle is connected at high pressure, and the vehicle can run normally.

When the VCU detects that the voltage U of the low-voltage battery system is greater than or equal to U2 (the DCDC cut-off working voltage is set by the manufacturer according to the working voltage requirements of the respective vehicle controllers), the DCDC stops working, the VCU gives a lower high-voltage instruction to the DCDC, and gives a disconnection instruction to the BMS to finish the power supplementing action;

working condition 2:

the vehicle is in the low voltage power supply state (low voltage system circuit is switched on, the low voltage part can work), at this moment, each controller of the vehicle is awakened, the low voltage control part can work normally, and the high voltage part does not work.

The voltage (U) of the low-voltage storage battery system is detected by a VCU low-voltage detection module, when the voltage (U) of the low-voltage storage battery is detected to be less than or equal to U1(DCDC starting threshold voltage), the VCU detects the working state of the DCDC system and the power battery system and the state of the whole vehicle, if the states of the DCDC system, the power battery system and the whole vehicle are not faulted, the VCU sends a relay pull-in instruction to the BMS, sends a high-voltage instruction to the DCDC, starts the DCDC system to supplement the electric energy of the low-voltage storage battery system, maintains the voltage stability of the low-voltage storage battery system, and when the VCU detects that the voltage (U) of the low-voltage storage battery system is detected to be more than or equal to U2(DCDC stopping working voltage), the VCU sends a power-down instruction to the DCDC, stops the operation of the DCDC, sends a BMS disconnection relay instruction to complete the power supplement action;

working condition 3:

the vehicle is in the dormant state (all high and low voltage electrical appliances of vehicle do not work), this moment the vehicle is in the dormant state with electrical appliances, the BMS utilizes the system clock, regularly awaken up the BMS and detect low voltage battery system voltage, when detecting that low voltage battery system voltage U examines and is less than or equal to U3 (DCDC opens the voltage threshold value during dormancy), MBS awakens up the VCU, VCU awakens up DCDC, VCU is to the DCDC system, power battery system, whole car detects, if there is no trouble, VCU assigns relay actuation instruction to the BMS, actuation DCDC return circuit relay, go up high voltage instruction to DCDC, when VCU detects that low voltage battery system voltage U examines and is more than or equal to U2(DCDC cut-off operating voltage), VCU assigns down the power command to DCDC, stop DCDC work, DCDC power down, disconnection DCDC return circuit relay, accomplish the benefit power action.

And (2) strategy two: (Intelligent charging control with integrated BDU)

Working condition 1:

the vehicle is in a high-pressure state: the whole vehicle can normally work after being controlled and self-checked, the whole vehicle has no fault, the vehicle main positive relay and the vehicle main negative relay attract the vehicle to be connected at high pressure, and the vehicle can normally run.

In the state, all controllers of the vehicle are awakened to work normally, and the voltage (U) of the low-voltage battery system is detected by using a BDU low-voltage detection module; when the voltage U of the low-voltage storage battery is detected to be less than or equal to U1(DCDC starting threshold voltage), the BDU detects the working states of the battery system, the DCDC system and the DCDC high-voltage loop, if no fault exists, the BDU actuates the relay to control the upper high voltage of the DCDC to start the electric energy supplement of the low-voltage storage battery system and maintain the voltage stability of the low-voltage storage battery system, and when the voltage U of the low-voltage storage battery is detected to be more than or equal to U2(DCDC stopping working voltage), the BDU controls the lower high voltage of the DCDC to disconnect the relay to finish the charging action;

working condition 2:

the vehicle is in the low pressure power supply state (low pressure system circuit switches on, and the low pressure can work with electrical apparatus part), and each controller of vehicle is awaken up this moment, and low pressure control part can normally work, and the high pressure does not switch on, and high-pressure part does not work.

The voltage (U) of the low-voltage storage battery system is detected by using a BDU low-voltage detection module, when the voltage (U) of the low-voltage storage battery is detected to be less than or equal to U1(DCDC starting threshold voltage), the BDU detects the working states of the DCDC system, the battery system and the DCDC high-voltage loop, and if the DCDC system, the battery system, the DCDC high-voltage loop and the whole vehicle are insulated and have no fault, the BDU controls a relay to attract, controls the upper high voltage of the DCDC and starts the DCDC; the electric energy supplement of the low-voltage storage battery system is started, when the voltage U of the low-voltage storage battery system is detected to be more than or equal to U2 (the cut-off working voltage of the DCDC), the BDU controls the DCDC to give off power, and the DCDC loop relay is disconnected;

working condition 3:

the vehicle is in a dormant state, at which time the vehicle controller is in a dormant state, and the low voltage battery system voltage is detected using the BDU low voltage detection system. The BDU utilizes the system clock, regularly awaken the BDU up and detect low-voltage battery system voltage, when detecting that low-voltage battery system voltage reaches DCDC opening voltage threshold when dormancy, the BDU detects DCDC system, battery system, DCDC high-voltage loop, insulating state, if no trouble, BDU control relay actuation, control DCDC high-voltage is started working, when BDU detects that low-voltage battery system voltage U examines and is greater than or equal to U2(DCDC cut-off operating voltage), BDU control DCDC issues down high-voltage, disconnection DCDC loop relay, the BDU gets into dormancy.

Example 2:

strategy one: (using VCU, BMS control)

Working condition 1:

all controllers of the vehicle pass through self-checking, no abnormity exists, the whole vehicle has no fault, the main positive relay and the main negative relay are attracted, the high-voltage electric appliance can be used for high voltage, and the whole vehicle can normally run.

The voltage of the low-voltage storage battery system is detected by using a VCU low-voltage detection system, the VCU detects the voltage U of the low-voltage storage battery system in real time, if the VCU detects that the voltage U of the low-voltage storage battery system is less than or equal to U1(DCDC starting voltage threshold), the VCU detects the states of the battery system, the DCDC system and the whole vehicle again, and if no fault exists; the VCU sends a relay actuation instruction (actuation slow-charging relay) to the BMS, the actuation action of the slow-charging relay completes the actuation of the relay fed back by the BMS to the VCU, the VCU sends a high-voltage enabling instruction to the DCDC, the DCDC is subjected to high voltage, and the high voltage of the DCDC is completed to feed back high-voltage completion information on the DCDC to the VCU; the method comprises the following steps that a DCDC starts to charge a low-voltage storage battery system, a VCU monitors the voltage of the low-voltage storage battery system during charging, when the voltage U of the low-voltage storage battery system is detected to be equal to or larger than U2(DCDC cut-off working voltage), the VCU gives a power-down stop instruction to the DCDC, the DCDC executes a power-down high-voltage instruction, high-voltage completion information is fed back to the VCU after the high-voltage completion of the DCDC, then the VCU gives a relay disconnection instruction (disconnection slow-charge relay) to the BMS, the BMS relay finishes feeding back the VCU slow-charge relay disconnection information, and the power-supplement operation is finished;

working condition 2:

the low-voltage system of the vehicle is in a conducting state, each controller of the vehicle is in an awakening state, the controller passes through self-checking, no abnormity exists, the whole vehicle has no fault, and the high-voltage part does not work.

The voltage of the low-voltage storage battery system is detected by using a VCU low-voltage detection system, the VCU detects the voltage U of the low-voltage storage battery system in real time, if the VCU detects that the voltage U of the low-voltage storage battery system is less than or equal to U1(DCDC starting voltage threshold), the VCU detects the battery system, the DCDC system and the whole vehicle again, and if no fault exists; the VCU sends a relay pull-in instruction (firstly pulling in the total negative relay and then pulling in the slow charging relay) to the BMS, and after the relay pull-in action is completed, the BMS carries out relay pull-in action on the VCU to complete information feedback; then the VCU issues a high-voltage enabling instruction to the DCDC, the DCDC is subjected to high voltage, the DCDC starts to charge the low-voltage storage battery system, the VCU monitors the voltage of the low-voltage storage battery system during charging, when the voltage U of the low-voltage storage battery system is detected to be more than or equal to U2(DCDC cut-off working voltage), the VCU issues a high-voltage stopping instruction to the DCDC, the DCDC is subjected to high voltage, and after the DCDC finishes the high voltage stopping, high-voltage stopping information is fed back to the VCU; then the VCU sends a relay disconnection instruction to the BMS (firstly disconnecting the total negative relay and then disconnecting the slow charging relay), the BMS completes the relay disconnection action, the relay disconnection completion information is fed back to the VCU, and the power supplement action is completed;

working condition 3:

the high-voltage system of the vehicle is in a disconnected state, the low-voltage system is connected, and the controller is in a dormant state;

the vehicle is in the dormancy state, and each controller dormancy is in order to guarantee that low voltage battery system voltage is stable, prevents that low voltage battery voltage from crossing excessively to cause the battery harm, the unable normal start of vehicle. When the voltage reaches the vicinity of the designed voltage threshold value, the low-voltage battery system is charged, and the stability of the low-voltage battery system is ensured.

The voltage of the low-voltage battery system is detected by a BMS low-voltage detection module, a voltage-time equation (U-T) of the low-voltage battery system is established according to the electric energy of the low-voltage battery and the static electric energy consumption of a vehicle, the voltage of the low-voltage battery system is detected by the BMS before dormancy, the time T1 for the voltage of the low-voltage battery system to reach DCDC starting voltage U1(1+ 0.3) is calculated according to the equation of the low-voltage battery (U-T), the BMS is timed by utilizing an internal clock of the BMS, the BMS is awakened when the BMS timing time reaches T1, and the BMS starts to detect the voltage of the low-voltage battery system: (1) if awakening the BMS to detect the voltage U of the low-voltage battery system, wherein the voltage U is detected to be U1(1+0.1), then the mode of detecting the voltage of the low-voltage battery by the BMS is changed into a timing awakening detection mechanism, namely: the BMS wakes up once every 0.5h to detect the voltage of the low-voltage battery system, and when the BMS detects that the voltage Udetection of the low-voltage battery system is less than or equal to U1 (the threshold value of the DCDC starting voltage), the BMS starts to detect the low-voltage battery system; (2) if the wake-up BMS detects that the voltage U of the low-voltage battery system is less than or equal to U1(1+0.1), the low-voltage battery system is charged;

and charging logic: the BMS reaches the timing time, the BMS is awakened, the BMS awakens a VCU, the VCU performs self-checking, if the self-checking is passed, the VCU awakens the DCDC, the DCDC performs self-checking, after the DCDC self-checking is completed, self-checking completion information of the VCU is fed back, the VCU judges the whole vehicle fault, and if no fault exists (the high-voltage requirement on the DCDC is met); the method comprises the following steps that a VCU sends a relay actuation instruction (firstly actuating a main negative relay and then actuating a slow charging relay) to a BMS, the BMS feeds back relay actuation information to the VCU after finishing relay actuation, then the VCU sends a high-voltage power-on instruction to a DCDC, the DCDC executes a high-voltage instruction, the DCDC feeds back finishing information to the VCU after finishing high voltage, and the DCDC starts to work to supplement electric energy to a low-voltage storage battery system; the VCU detects the voltage of the low-voltage storage battery system during the charging period, and when the voltage U of the low-voltage storage battery is detected to be larger than or equal to U2(DCDC cut-off working voltage), the DCDC stops working; the VCU sends a power-off stopping instruction to the DCDC, the DCDC powers off, and a power-off completion signal is fed back to the VCU after the DCDC finishes powering off; then the VCU sends a relay disconnection instruction to the BMS (firstly disconnecting the slow charging relay and then disconnecting the main negative relay), and the BMS completes the relay disconnection instruction and feeds back relay disconnection information; the VCU gives a sleep command to the DCDC and the BMS, the voltage of the low-voltage storage battery system is detected before the BMS sleeps, the time T1 for the voltage of the low-voltage storage battery to drop to U1(1+ 0.3) is calculated by using a low-voltage storage battery (U-T) equation, the BMS enters timing, the controller sleeps, the charging action is completed, and the next cycle is entered.

And (2) strategy two: (the BMS is separated from the power battery, so that the battery unpacking maintenance condition caused by the battery system fault is avoided, the battery maintenance after-sales cost is reduced, the BMS and the DCDC control system are integrated, controlled and calculated, the vehicle control is more centralized and the control is more efficient.) the BDU is adopted for control

Working condition 1:

the vehicle is in a high-pressure state: the whole vehicle is controlled to pass through self-checking without faults, a main positive relay and a main negative relay of the vehicle are attracted, the vehicle is connected at high pressure, and the vehicle can run normally.

When the BDU detects that the voltage U of the low-voltage storage battery system is not greater than U1 (a DCDC starting voltage threshold), the BDU detects the power battery system, the DCDC working state, the high-voltage system insulation state and the slow charging loop state again if the power battery system, the DCDC working state, the high-voltage system insulation state and the slow charging loop state meet the power-on requirement; the BDU controls the attraction slow-charging relay, and after the attraction of the relay is finished, the BDU controls the high voltage of the DCDC to start working; the BDU detects the voltage of the low-voltage battery system in real time during charging, when the voltage U of the low-voltage battery system is detected to be more than or equal to U2(DCDC cut-off working voltage), the DCDC stops working, the BDU controls the high voltage under the DCDC, and then the BDU disconnects the slow charging relay to finish the charging action;

working condition 2:

the low-voltage system of the vehicle is in a conducting state, the low-voltage electricity utilization part can work normally, all controllers of the vehicle pass through self-checking, no abnormality occurs, and the whole vehicle has no fault;

the method comprises the following steps that voltage of a low-voltage storage battery system is detected by using a BDU low-voltage detection system, the BDU detects the voltage U of the low-voltage storage battery system in real time, if the BDU detects that the voltage U of the low-voltage storage battery system is not larger than U1(DCDC starting threshold voltage), the BDU detects a power battery system, a DCDC, the insulation state of a whole vehicle and the state of a DCDC high-voltage loop, and if no abnormity exists; the BDU attracts the relay (attracts the main negative relay first and then attracts the slow charging relay), after the relay attracts the action, the BDU controls the high voltage on the DCDC, and after the high voltage is achieved, the DCDC starts to work to charge the low-voltage storage battery system; the BDU carries out voltage detection on the low-voltage storage battery system during charging, when the voltage U detection of the low-voltage storage battery system is larger than or equal to U2(DCDC cut-off working voltage), the BDU controls the DCDC to be powered down, and after the power down is finished, the BDU disconnects the main and negative relays firstly and then disconnects the slow charging relay to finish the charging action;

working condition 3:

the high-voltage system of the vehicle is in a disconnected state, the low-voltage system is connected, and the controller is in a dormant state;

each controller of the vehicle is in a dormant state, in order to ensure the voltage stability of a low-voltage battery system and prevent the low-voltage battery system from excessively low voltage to cause battery damage and the vehicle from being started normally, the voltage of the low-voltage battery system needs to be monitored, and the low-voltage battery system is charged when the voltage of the low-voltage battery system reaches a designed voltage threshold value, so that the voltage stability of the low-voltage battery system is ensured.

Voltage detection of the low-voltage battery system:

establishing a low-voltage battery system voltage-time equation (U-T) according to the electric energy of the low-voltage battery and the static electric energy consumption of the vehicle, detecting the voltage of the low-voltage battery system by the BDU before dormancy, and calculating the time T1 (U1: DCDC starting threshold voltage) for the voltage of the low-voltage battery system to drop to U1(1+ 0.3) according to the battery (U-T) equation; the BDU utilizes an internal clock to time, starts to time from the BDU dormancy, wakes up the BDU when the timing time reaches T1, and detects the voltage of the low-voltage battery system; (1) if the BDU detects the voltage U of the low-voltage battery system after awakening and detects that the voltage U is greater than U1(1+0.1), then the BDU detects the voltage of the low-voltage battery by changing a mode into a timing awakening detection mechanism, namely: the BDU wakes up once every 0.5h to detect the voltage of the low-voltage storage battery system; when the BDU detects that the voltage U of the low-voltage storage battery system is less than or equal to U1(1+0.1), the BDU starts to detect the low-voltage battery system; (2) and if the BDU wakes up, detecting that the voltage U of the low-voltage storage battery system is less than or equal to U1(1+0.1), and starting to charge the low-voltage storage battery system.

And (3) charging strategy:

when the voltage of the low-voltage storage battery reaches a charging condition, the BDU detects a power battery system, the whole vehicle insulation condition, a DCDC system and a DCDC high-voltage loop, if no fault exists, the BDU controls a relay to pull in (firstly pulls in a main negative relay and then pulls in a slow charging relay), the relay pulling action is completed, the BDU controls the upper high voltage of the DCDC, the DCDC starts working and charges the low-voltage storage battery system, the BDU detects the voltage of the low-voltage storage battery system during charging, when the voltage U detects that the voltage is not less than U2(DCDC cut-off working voltage), the BDU controls the lower high voltage of the DCDC, the BDU controls a disconnecting relay (firstly disconnects the main negative relay and then disconnects the slow charging relay) after the DCDC finishes the power supply, and the BDU enters a dormancy program; the BDU detects the voltage of the low-voltage storage battery system before dormancy, calculates the time T1 for the voltage of the low-voltage storage battery to drop to U1(1+ 0.3) by using a voltage battery U-T equation, starts timing, enables the BDU controller to enter a dormant state, and completes charging; the next charging cycle is started.

It is clear that the specific implementation of the invention is not restricted to the above-described embodiments, but that various insubstantial modifications of the inventive process concept and technical solutions are within the scope of protection of the invention.