[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.
