Method and device for controlling power-on flow of multi-branch battery energy storage system

A battery energy storage system, energy storage system technology, applied in battery circuit devices, circuit devices, secondary battery charging/discharging, etc., can solve the problem of system reliability reduction, affecting the rescue effect, and the reliability of lithium-ion battery energy storage systems. Reduced performance and other issues, to improve reliability and system stability

Active Publication Date: 2015-05-06
BEIJING ELECTRIC VEHICLE
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AI-Extracted Technical Summary

Problems solved by technology

[0004] The disadvantages of the above-mentioned existing lithium-ion battery energy storage systems are: after a single-cell or node open-circuit fault occurs, due to the branchless structure, the battery system as a whole will cut off the external high-voltage output, and it is impossible to realize...
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Method used

Embodiments of the present invention support independent control of power on and off, and improve system stability; combined with future standard modules, it is better to meet the cascade utilization of modules, and branches with different discharge depths can be directly connected to the system;
If the current charging and discharging demand of the lithium-ion battery energy storage system is to charge the energy storage device, then the MBCU sets the lowest voltage branch in the ready state, and issues a zero power request to the external high-voltage system at the same time, the above-mentioned minimum voltage branch The voltage is the lowest voltage; if the voltage difference between the other branch voltage and the lowest voltage is within the set threshold, the other branch is also set to the standby state. Then, the MBCU issues a zero power request to the external high-voltage system, the MBCU enables the power-on command to the SBCU of each branch in the standby state, and each branch in the standby state enters the power-on process. The p...
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Abstract

The invention provides a method and a device for controlling the power-on flow of a multi-branch battery energy storage system. The method mainly comprises the following steps: an MBCU obtains the voltage of each branch according to state information reported by the S-BCU of each branch, the MBCU enable the power-on flow of partial branches of which the voltages exceed the average voltage of the various branches upon judging the imbalance of the voltages of the various branches and when a charging/discharging request is external discharging, and when the charging/discharging request is external charging, the MBCU enables the power-on flow of partial branches of which the voltages are lower than the average voltage of the various branches. According to the method, when the voltages of the branches are in an imbalance state, partial unbalanced branches are enabled to enter the power-on flow firstly by use of the MBCU, and each branch is powered on in different time so that the system stability can be improved. As a plurality of branches connected in parallel, the branches out of order can be flexibly removed without affecting the work of other branches, and therefore, the reliability of the battery energy storage system is improved.

Application Domain

Batteries circuit arrangementsSecondary cells charging/discharging +2

Technology Topic

Electrical batterySystem stability +4

Image

  • Method and device for controlling power-on flow of multi-branch battery energy storage system
  • Method and device for controlling power-on flow of multi-branch battery energy storage system
  • Method and device for controlling power-on flow of multi-branch battery energy storage system

Examples

  • Experimental program(3)

Example Embodiment

[0043] Embodiment one
[0044] The schematic structural diagram of a lithium-ion battery energy storage system provided in this embodiment is as follows: figure 1 As shown, the lithium-ion battery energy storage system is composed of several branches connected in parallel, each branch is composed of several groups of battery modules connected in series, and the battery modules are composed of battery cells connected in series and parallel. Each branch has an independent relay and pre-charging equipment. After the branch is connected in parallel, it is connected to the external high-voltage system through two relays, the main positive and the main total negative. When different branches are in a state of voltage balance, each branch needs to complete the power-on action. When each branch is in an unbalanced state before power-on, the system obtains the current charging and discharging demand through the man-machine interface, and determines the power-on process of the branch according to the charging and discharging demand and the current state of the battery system of each branch.
[0045] The principle schematic diagram of the control method of the power-on process of the lithium-ion battery energy storage system in the embodiment of the present invention is as follows figure 2 As shown, MBCU (Master Battery Management Unit, main battery management unit) is set in the lithium-ion battery energy storage system, and a S-BCU (Subordinate Battery Management Unit, slave battery management unit) is set in each branch, and MBCU passes through The CAN (Controller Area Network, controller area network) network is connected to each S-BCU. Inside each branch, a BMU (Battery Management Unit, battery management unit) is set for each battery module, and the S-BCU passes through the CAN network. Connect with each BMU.
[0046] The functions of each S-BCU include: controlling the enablement of the internal BMU of each branch, controlling the on-off of the relay of each branch, and judging its actual state; monitoring the total voltage and current of each branch, according to M-BCU command, execute branch cut-in, disengage the main circuit command; branch insulation detection, deal with internal short circuit, external short circuit, over temperature, temperature rise too fast fault of each branch, monomer detection fault, monomer Undervoltage fault, insulation fault; estimate branch SOC, etc.
[0047] The functions of MBCU include: responsible for communication function control with the national standard fast charging system; monitoring the overall operating status of the circuit: issuing cut-in and exit commands for each branch, and detecting the insulation of the main circuit; monitoring the working voltage and working current of the main circuit ; The main relay for the control system work, (one positive and one negative, low-side drive).
[0048] The functions of the BMU include: monitoring function, detecting the voltage and temperature of the single battery in the battery module, and realizing the switching of the battery collection mode; execution function: executing the balance command of the battery system, and sending and receiving the bus; logic calculation: calculating the module The highest and lowest voltage; the highest and lowest temperature of the internal battery, and record the highest and lowest voltage; the serial number of the battery cell with the highest and lowest temperature; judge the overvoltage and undervoltage fault of the battery cell in the module, and report the fault to H_BCU.
[0049] The processing flow chart of the control method of the power-on process of the lithium-ion battery energy storage system in the embodiment of the present invention is as follows image 3 As shown, the following processing steps are included:
[0050] Step S310, the MBCU in the multi-branch battery energy storage system acquires the voltage of each branch according to the state information reported by the S-BCU of each branch.
[0051] After the lithium-ion battery energy storage system is started and the MBCU self-checks, it is enabled for each S-BCU. After the SBCU checks itself, enable it for each BMU. After the BMU self-inspection, it detects the state information of each battery module and the battery cells in the battery module according to the set time interval, and reports the detected state information to the S-BCU. The state information can include each battery cell voltage, current and fault information etc. After the S-BCU synthesizes the status information reported by each BMU, it reports the status information of the branch to the MBCU according to the set time interval. The status information includes the total voltage, total current, SOC (state of charge, state of charge) and fault information, etc.
[0052] The MBCU obtains the voltage and fault information of each branch according to the status information reported by the S-BCU of each branch.
[0053] In step S320, the MBCU determines whether the voltages of the branches are balanced, if yes, execute step S360, otherwise, execute step S330.
[0054] Step S330, when the MBCU determines that the voltages of each branch circuit are unbalanced, then the MBCU obtains the current charge and discharge demand of the battery energy storage system, and when the charge and discharge demand is for external discharge, then perform step S340; otherwise, perform step S330. S350.
[0055] Step S340, when the charge and discharge demand is to discharge to the outside, then the MBCU enables some branches whose voltage exceeds the average voltage of each branch to perform the power-on process, and other branches except the part of the branches do not Power-on process.
[0056] If the current charge and discharge demand of the lithium-ion battery energy storage system is external discharge, the MBCU sets the highest voltage branch in the standby state, and the voltage of the above-mentioned highest voltage branch is the highest voltage; if the voltage of other branches is higher than the highest voltage If the pressure difference between them is within the set threshold, the other branch will also be placed in the standby state, and the above-mentioned set threshold can be 1. Then, the MBCU issues a zero power request to the external high-voltage system, the MBCU enables the power-on command to the SBCU of each branch in the standby state, and each branch in the standby state enters the power-on process. The power-on process mainly includes: Each branch in the standby state is connected to an external high-voltage system, and each branch in the standby state is discharged, thereby reducing the voltage of each branch in the standby state.
[0057] Execute step S360.
[0058] Step S350, when the charge and discharge demand is for external charging, the MBCU enables some branches whose voltage is lower than the average voltage of each branch to perform a power-on process, and other branches except the part of the branches do not Go through the power-on process.
[0059] If the current charge and discharge demand of the lithium-ion battery energy storage system is to charge the energy storage device, the MBCU will set the lowest voltage branch in the standby state, and at the same time issue a zero power request to the external high voltage system. The voltage of the above minimum voltage branch is the lowest voltage; if the voltage difference between the other branch voltage and the lowest voltage is within the set threshold, the other branch is also set to the standby state. Then, the MBCU issues a zero power request to the external high-voltage system, the MBCU enables the power-on command to the SBCU of each branch in the standby state, and each branch in the standby state enters the power-on process. The power-on process mainly includes: Each branch in the ready state is connected to an external high-voltage system, and each branch in the ready state is charged, thereby increasing the voltage of each branch in the ready state.
[0060] Step S360, then, after the MBCU determines that the voltage of each branch is in a balanced state according to the state information reported by the S-BCU of each branch, the MBCU enables the power-on command to all the SBCUs, and the branch where each SBCU is located is powered on process. After the power-on process of the lithium-ion battery energy storage system ends, the system resumes the previous power output.

Example Embodiment

[0061] Embodiment two
[0062] When the MBCU determines that a branch is faulty based on the status information reported by the S-BCU of each branch, it will issue a zero power request to the external high-voltage system, and disconnect the relay of the faulty branch after reaching zero power, and a fault will occur branch removed. Since each branch is in parallel state, removing the failed branch will not affect other branches. After removing the faulty branch, restore the charging and discharging power of the system.

Example Embodiment

[0063] Embodiment three
[0064] A schematic structural diagram of a power-on process control device for a multi-branch battery energy storage system provided in this embodiment is as follows: Figure 4 As shown, including: MBCU41, S-BCU42 of each branch and BMU43 of each battery module;
[0065] The S-BCU41 of each branch is used to report the state information of each branch to the MBCU, and the state information includes the voltage of each branch;
[0066] The MBCU42 is used to obtain the voltage of each branch according to the state information reported by the S-BCU of each branch, and to obtain the current charge and discharge demand of the battery energy storage system when it is determined that the voltage of each branch is unbalanced; When the charge and discharge requirement is for external discharge, the power-on process is performed on some branches whose voltage exceeds the average voltage of each branch, and the other branches except the part of the branch do not perform the power-on process; when the When the charging and discharging requirement is external charging, some branches whose voltage is lower than the average voltage of each branch are enabled to perform the power-on process, and the other branches except the said part of the branches do not perform the power-on process.
[0067] Further, the battery energy storage system is composed of several branches connected in parallel, each branch is composed of several groups of battery modules connected in series, and the battery modules are composed of battery cells connected in series and parallel, MBCU is set in the battery energy storage system, An S-BCU is respectively set in each branch, and the MBCU is connected to each S-BCU through a CAN network, and the device also includes a BMU of each battery module;
[0068] The BMU43 of each battery module is used to be installed in each battery module inside each branch, and connected to the S-BCU of each branch through the CAN network; after the battery energy storage system is started, each BMU Detect the battery cells in each battery module according to the set time interval, and report the detected status information to the S-BCU, which includes the voltage and fault information of each battery cell;
[0069] The S-BCU42 of each branch is used to synthesize the state information reported by each BMU, and report the state information of the branch to the MBCU according to the set time interval, the state information includes the voltage of each branch and fault information;
[0070] The MBCU41 is configured to obtain the voltage and fault information of each branch according to the status information reported by the S-BCU of each branch.
[0071] Further, the MBCU41 is configured to set the branch with the highest voltage and the branch whose voltage difference between the voltage and the highest voltage is within a set threshold when the charging and discharging demand is to discharge to the outside. , the highest voltage is the voltage of the highest voltage branch, issuing a zero-power request to the external high-voltage system, enabling a power-on command to the SBCU of each branch in the ready state, and entering the power-on process for each branch in the ready state;
[0072] According to the state information reported by the S-BCU of each branch, after it is determined that the voltage of each branch is in a balanced state, the power-on command is enabled to all SBCUs, and the branch where each SBCU is located performs a power-on process.
[0073]Further, the MBCU41 is configured to set the lowest voltage branch and the branch whose voltage difference between the voltage and the lowest voltage is within a set threshold when the charging and discharging demand is external charging , the lowest voltage is the voltage of the lowest voltage branch, issuing a zero-power request to the external high-voltage system, enabling a power-on command to the SBCU of each branch in the ready state, and entering the power-on process for each branch in the ready state;
[0074] According to the state information reported by the S-BCU of each branch, after it is determined that the voltage of each branch is in a balanced state, the power-on command is enabled to all SBCUs, and the branch where each SBCU is located performs a power-on process.
[0075] Further, the MBCU41 is configured to issue a zero-power request to the external high-voltage system to disconnect the relay of the failed branch when it is determined that a branch fails according to the status information reported by the S-BCU of each branch, Remove the faulty branch.
[0076] The specific process of using the device of the embodiment of the present invention to control the power-on process of the multi-branch battery energy storage system is similar to the foregoing method embodiment, and will not be repeated here.
[0077] To sum up, in the embodiment of the present invention, when the branch voltage is in an unbalanced state, the MBCU is used to enable some unbalanced branches to perform the power-on process first, so that each branch is powered on in a time-sharing manner, thereby improving system stability. .
[0078] In the embodiment of the present invention, by setting multiple parallel-connected branches inside the battery energy storage system, the faulty branch can be removed flexibly without affecting the work of other branches. Combined with the quick-change mechanical structure, when maintaining the faulty branch It does not affect the charging of external devices by the system or the charging of mobile energy storage devices through ground charging equipment, thereby improving the reliability of the battery energy storage system.
[0079] The embodiment of the present invention supports independent control of power on and off, improving system stability; combined with future standard modules, it can better meet the cascade utilization of modules, and branches with different discharge depths can be directly connected to the system;

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