KR20200021368A - Battery Management system based on Cell Charge up Current - Google Patents

Abstract

The present invention relates to a battery management system based on a charge current for controlling charge and discharge to make charge/discharge voltages of a plurality of charge cells uniform when charging the charge cells connected in parallel constituting a battery. According to the present invention, the battery management system utilizes: a battery state of charge (SOC) measurement algorithm including a charge/discharge current measurement algorithm for cells, a charge quantity comparison algorithm for cells, and a voltage and charge quantity measurement algorithm for cells; a battery state of health (SOH) measurement algorithm including an impedance measurement system for cells, an aging measurement algorithm for cells, and a temperature measurement algorithm for cells; and a battery pack monitoring algorithm including a voltage and current comparison/measurement algorithm for cells, and a voltage and current comparison/measurement algorithm for a battery pack. It is possible to improve a battery charge/discharge difference from 5-10% to 3-5% through active battery management based on a cell charge current, thus resulting in a longer battery life and stabilization of a system with such a battery. These enable a high volume of an energy storage system.

Description

Battery Management System based on Cell Charge up Current}

The present invention relates to a battery management system based on a charge current, and more particularly, when charging or discharging a plurality of series connected charge cells constituting a battery, charging and discharging are performed such that the charge / discharge voltage of the charge cells becomes uniform. It is for controlling, and the battery charge / discharge deviation is 5% to 10%, through the active battery management based on the cell charging current to improve to 3% to 5%, so that the life of the battery The present invention relates to a battery management system based on a charging current, which is long and can be stabilized such that a battery-embedded system can be stabilized.

In general, due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing, and the most actively researched fields are power generation and storage using electrochemistry.

A representative example of an electrochemical device using such electrochemical energy is a secondary battery, and its use area is gradually increasing.

The battery pack including the secondary battery as a unit cell is used as a power source for various devices such as an electric vehicle, an electric bicycle, a power tool, and a portable computer, and a plurality of battery cells are provided to secure voltage and capacity required for each device. It is usually connected in series.

In order to charge such a battery pack, a method of applying a current in a state in which the battery cells are connected in series and charging the battery pack in general is used.

However, the battery cells included in the battery pack have a certain difference in capacity and internal resistance due to manufacturing errors, and when charging a batch without consideration for this, charging unevenness occurs, some battery cells Are overcharged, and some battery cells may not be fully charged.

Due to the charging non-uniformity, the capacity of some battery cells may not be fully utilized, and the capacity of the battery pack may be reduced, or the battery life may be shortened due to overcharging or over-discharging of some battery cells.

Conventionally, in order to solve this problem, by using the battery management system (BMS) built in the battery pack, after measuring the voltage of each of the battery cells in the charging process, when the battery cells are voltage imbalance, high voltage A battery cell balancing method has been used in which the voltage between the battery cells is balanced by discharging specific battery cells.

As described above, in order to discharge a specific battery cell during charging, it is necessary to connect a resistor and a transistor to each battery cell and control the same through the BMS. Therefore, the configuration of the battery pack is complicated and the control logic of the BMS is complicated. .

In addition, since the balancing of the battery cells is induced, the energy efficiency is reduced by the amount of discharge, and the battery pack is overheated due to the heat generated during the discharge.

Therefore, even when balancing battery cells when charging a battery pack, high energy efficiency, preventing overheating of the battery pack, and development of a technology for simplifying the configuration of the battery pack are required.

Republic of Korea Patent Application Publication No. 10-2007-0111587

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is to control the charging and discharging so that the charging / discharging voltage of the charging cells becomes uniform when charging or discharging a plurality of charge cells connected in series. A battery state of charge (SOC) measurement algorithm including a charge and discharge current measurement algorithm of each cell, a charge comparison algorithm of each cell, a voltage and a charge measurement algorithm of each cell, an impedance measurement algorithm of each cell, Battery State (SOH) measurement algorithm including aging measurement algorithm of each cell and temperature measurement algorithm of each cell, voltage and current comparison measurement algorithm of each cell, and voltage and current comparison measurement of battery pack The battery pack monitoring algorithm including the algorithm, and active based on the cell charging current Battery management allows battery charge / discharge deviations to improve from 5% to 10%, to 3% to 5%, resulting in longer battery life and stabilization of the system in which these batteries are embedded. (ESS) can be large-capacity, large-capacity battery cell balancing is possible due to control of balancing current over 5A through FET and multi-coupled Flayback Transformer and FET and efficiencies by using storage energy in coupled inductor, and coupled inductor The cost reduction and reliability increase due to the reduced number of parts, and the product size can be reduced due to the small number of parts, thereby providing a charge current-based battery management system that can secure price competitiveness.

The charge current-based battery management system of the present invention for achieving the above object is provided with a balancing control unit for controlling the operation of the FET consisting of the P MOSFET and the N MOSFET serving as a control switch; The balancing execution part composed of one bidirectional flyback transformer is connected to the internal winding, and one side of the balancing execution part is connected between the battery cell and the battery cell, and the other side of the balancing execution part is connected between the P MOSFET and the N MOSFET. Provided; A monitoring unit configured to monitor current and voltage for each battery cell and transmit the same to the balancing control unit; Since P MOSFET and N MOSFET, two control switches are controlled simultaneously by one control signal, and the operation is always divided into odd battery cells and even battery cells to control the balancing of adjacent battery cells to prevent battery cell imbalance. It features.

The charge current based battery management system measures the total voltage and current of the battery after initialization, and then measures the voltage and current of each battery cell; Then, the maximum charge amount, the minimum charge amount, and the average charge amount of the even-numbered battery cells are measured; Then, the maximum charge amount, the minimum charge amount, and the average charge amount of the odd-numbered battery cells are measured; Subsequently, the maximum charge amount, the minimum charge amount relative to the average charge amount of the charge amount is determined from the charge amount of each battery cell to select the battery cells requiring balancing; Subsequently, after performing balancing on the selected battery cells, balancing may be performed by continuously selecting the maximum charge amount and the minimum charge amount as compared with the average charge amount.

The battery management system based on the charging current measures the life of the battery cell by measuring a change in the internal impedance of each battery cell; By using NTC device whose resistance value changes with temperature, it is possible to measure the overall temperature affected by heat generated by internal impedance and external environment during charging / discharging of battery cells.

According to the battery management system based on the charging current of the present invention as described above, when charging or discharging a plurality of series connected charging cells constituting the battery, the charging and discharging voltage of the charging cells is uniformed. A battery state of charge (SOC) measurement algorithm including a charge and discharge current measurement algorithm of each cell, a charge comparison algorithm of each cell, and a voltage and charge measurement algorithm of each cell, Battery-of-state (SOH) measurement algorithm including impedance measurement algorithm, aging measurement algorithm of each cell and temperature measurement algorithm of each cell, voltage, current comparison measurement algorithm of each cell and voltage of battery pack Using battery pack monitoring algorithms, including current comparison measurement algorithms, Active battery management allows battery charge / discharge deviations to improve from 5% to 10%, to 3% to 5%, resulting in longer battery life and system built-in battery Energy storage device (ESS) can be stabilized, and large capacity battery cell can be achieved by controlling the balancing current of 5A or more through the coupled inductor and multi-coupled Flayback Transformer and FET, and increasing the balancing efficiency by using the stored energy in the coupled inductor. Balancing is possible, cost reduction and reliability are increased by reducing the number of parts by the coupled inductor, and product size can be reduced due to the small number of parts, which can secure price competitiveness.

1 is a view showing a conventional active balancing circuit,
2 is a diagram illustrating a battery management system based on a charging current according to an embodiment of the present invention.
3 is a view showing the overall configuration including a battery management system based on the charging current according to an embodiment of the present invention,
4 and 5 are views showing the configuration of a battery management system based on the charging current according to an embodiment of the present invention,
6 is a diagram illustrating an active balancing circuit constituting a battery management system based on a charging current according to an embodiment of the present invention.
7 is a flowchart illustrating balancing control through a battery management system based on a charging current according to an embodiment of the present invention.
8 is a view showing a state of measuring the battery charge amount, battery life, temperature in the charge current-based battery management system according to an embodiment of the present invention,
9 is a diagram illustrating a balancing control result when charging through a battery management system based on a charging current according to an embodiment of the present invention.
10 is a diagram illustrating a balancing control result when discharging through a battery management system based on a charge current according to an embodiment of the present invention.
11 is a view showing a battery management system based on a charging current according to another embodiment of the present invention.
12 is a view for explaining an operation of a battery cell constituting a battery management system based on charging current according to another embodiment of the present invention.
13 is a view for explaining the operation of the monitoring unit constituting the battery management system based on the charging current according to another embodiment of the present invention,
14 is a diagram for describing balancing control through a battery management system based on a charging current according to another embodiment of the present invention.
15 is a flowchart for describing balancing control through a battery management system based on a charging current according to another embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

As shown in FIGS. 2 to 6, the battery management system based on the charging current according to an embodiment of the present invention includes a multi-coupled flyback transformer having a COUPLED INDUCTOR and a FET, and an integrated control board, which is configured as a BMS module. .

The battery cell that can be balanced in the battery management system is 12 channels (ch), the cell voltage measurement range is 0 ~ 4Vdc, the cell package voltage measurement range is 0 ~ 48Vdc (Max), the deviation voltage range between cells 0 ~ 50mVpp, the test battery capacity can be equipped with a performance of 48V 20Ah.

The battery management system manages each battery cell by monitoring and balancing basic 12 battery cells, and configures 12 battery cells as a unit pack.

The battery cell may be a lithium ion based battery cell such as lithium ion based NMC lithium ion, lithium ion iron phosphate, or lithium ion nickel.

As a function of the battery management system, safety functions, control and monitoring functions, standby functions, security and algorithm functions are further added.

As a safety feature, the risks that arise from undetected abnormal high voltages present in the car chassis and from fire or explosion of high-voltage batteries, which are the causes of the most dangerous faults in the battery system, are the effects of old cables or accidents. The causes of such high voltage batteries include, for example, battery overcharging in the public network or due to energy recovery, premature aging of the battery due to the release of explosive gases, faulty liquid inflow and short circuit due to rainwater, faulty repair, etc. Misuse and poor thermal management errors.

With regard to safety, the main switch (main relay) plays an important role in preventing high voltage-related accidents and ensuring that the BMS electronics have an appropriate error response.

If an error occurs, the switch must be opened by the BMS module within an appropriate error response time (eg less than 10ms).

Non-critical fault safety conditions indicate that in the event of a failure of the BMS microcontroller (MCU), an independent external safety device, such as a window watchdog, causes the main switch relay to safely maintain two high voltage contacts to the drive, even if the controller logic is completely wrong. (Plus / minus) is guaranteed to open all.

The BMS also includes other safety features such as leakage current monitoring and main switch relay monitoring.

As a control and monitoring function, the BMS controls and monitors an electronic balancing slave installed in the battery stack.

The balancing IC acts as the electronic front end of the individual high voltage battery cells, electrically isolated from the BMS, performing general balancing of the individual cell stacks and precise sensing of single cell voltages.

A balancing IC typically manages a cluster of up to 12 individual battery cells.

Clusters of related quantities connected in series generate high intermediate circuit voltages of up to several hundred volts of inverter control required for inverter electric drive in electric vehicles.

As a standby function, the BMS requires a special low power base that allows the BIC to wake the system in the same way as a timer while requiring very low MCU power consumption in the μA range to record specific individual battery cell data in BMS mode of operation. Provides standby function.

As a security and algorithmic function, replacing individual cells in existing battery clusters or assembling used batteries from dismantled discrete components hides potential safety hazards such as safety-related errors or even explosions or fires.

Thus, appropriate protection modules, such as Infineon's Origa chip, can be installed directly into individual cell clusters.

However, as a low-cost alternative, logical protection for battery individual data can be integrated into the MCU in the form of a hardware security module (HSM).

For reference, as a circuit for performing the existing active balancing, (a) of FIG. 1 shows a BUCK & BOOSTOR balancing method using a plurality of inductors and FETs, resulting in an increased cost due to excessive use of parts. The circuit structure of each battery cell is complicated by the use of the FLYBACK TRANSFORMER, and the cost increases accordingly. In FIG. 1C, the control is complicated by the structure in which each battery cell is connected to one transformer.

On the contrary, the battery management system according to the present invention can maintain the cell of the large capacity battery more uniformly, reduce the cost, and improve the product life and reliability to secure the competitiveness of the product and the current of the battery cell. 12CH bidirectional FLYBACK 4A current active balancing by charge level.

In order to perform the balancing in the battery management system according to the present invention, as shown in Figures 3 to 6, a balancing control unit (MCU) for controlling the operation of the FET consisting of the P MOSFET and the N MOSFET serving as a control switch is provided In addition, a balancing unit (Cell Balancing Parts) consisting of one bidirectional flyback transformer is connected to an internal winding. One side of the balancing unit is connected between the battery cell and the battery cell, and the other side of the balancing unit is a P MOSFET. And is connected between the N MOSFET.

It is equipped with a monitoring unit (Cell Monitoring) that monitors the current and voltage for each battery cell and transfers it to the balancing control unit. Since the P MOSFET and the N MOSFET, two control switches are simultaneously controlled by one control signal. It is controlled to prevent the battery cell imbalance by balancing the adjacent battery cells by dividing the odd-numbered battery cells and the even-numbered battery cells.

The battery management system according to the present invention measures the total voltage and current of the battery after initialization, and then measures the voltage and current of each battery cell, and then the maximum charge amount, minimum charge amount, and average charge amount of even-numbered battery cells. The maximum charge amount, the minimum charge amount, and the average charge amount of the odd-numbered battery cells are measured, and then the maximum charge amount, the minimum charge amount compared to the average charge amount of the charge amount of each battery cell are determined, and the battery that needs to be balanced. After the cell is selected, balancing is performed on the selected battery cell, and then the maximum charge amount and the minimum charge amount are continuously selected as compared with the average charge amount to perform balancing.

The battery management system according to the present invention performs measurement of battery SOC, SOH, and THERMAL. The battery management system measures the change in internal impedance of the battery cell, and calculates the SOH by calculating the equation 1 and FIG. 8.

Subsequently, the charging amount of the entire battery pack is measured based on the current evaluated by the control algorithm, and by using the NTC element whose resistance value varies with temperature, the heat and external environment generated by the internal impedance during the charge / discharge of the battery cell are determined. Measure the overall temperature affected.

The battery management system according to the present invention has a protection operation function of overcharge voltage (OVP), overdischarge voltage (UVP), high temperature cutoff (OTP), low temperature cutoff (UTP), overcharge current (OCCP), overdischarge current (ODCP) and In addition, it performs the cell balancing function and provides the function of controlling the battery status information, etc. measured by the BMS through the cell balancing program as follows.

1) Over Voltage Alarm / Protection

While monitoring the cell voltage, if any cell reaches the Over Voltage Alarm first, OVA Status Bit is set and a warning is sent.When the cell voltage keeps rising and reaches Over Voltage Protection, the OVP Status Bit is set and the BUZZER operates. Send out a beep.

If all cell voltage reaches OVP Release Voltage after OVA / OVP operation, OVA / OVP Bit is cleared and BUZZER warning sound stops.

2) Under Voltage Alarm / Protection

While monitoring the cell voltage, if any of the cells reaches the Under Voltage Alarm first, the UVA Status Bit will be set and a warning will be sent.If the Cell voltage continues to fall and the Under Voltage Protection is reached, the UVP Status Bit will be set and the BUZZER will operate. Send out a beep.

If all cell voltage reaches UVP Release Voltage after UVA / UVP operation, UVA / OVP Bit is cleared and BUZZER warning sound stops.

3) Over Charge Current Protection

While monitoring the current during charging, if OCCP Status Bit is detected above the Over Charge Current Protection set in the parameter, the OCCP Status Bit is set and the BUZZER operates to emit a warning sound.

4) Over Discharge Current Protection

While monitoring current during discharging, if current over Over Discharge Current Protection set in parameter is detected, ODCP Status Bit is set and BUZZER operates to emit a warning sound.

5) Charge High Temperature Protection

While monitoring the cell temperature, if any of the cell temperature is above the Charge Hi Temp Protection setting value, the CHTP Status Bit is set and the BUZZER operates to emit a warning sound.

6) Charge Low Temperature Protection

While monitoring the cell temperature, if any of the cell temperature is lower than the Charge Low Temp Protection setting value first, the CLTP Status Bit is set and the BUZZER operates to emit a warning sound.

7) Discharge High Temperature

While monitoring the cell temperature, if any of the cell temperature is above the Discharge Hi Temp Protection setting value, the DHTP Status Bit is set and the BUZZER operates to emit a warning sound.

8) Cell Balancing

When a cell voltage reaches the set voltage, CELL balancing starts. When a certain cell voltage reaches the set value MAX, LOAD operates to discharge the CELL to the set value MIN and then charge the CELL again.

This operation is repeated and the FAN continues to operate in the charging mode when balancing the cells.

If all the CELL voltages meet the set value, LOAD operates when the charging current continues to flow. When the charging current reaches ZERO, it stops after about 10 minutes.

9) SOC calculation

The initial SOC is 100% when charging over a certain voltage, and the SOC calculation is calculated using the current integration method (measured by integrating the measured current in 1 second increments).

After that, when the BMS is turned off, the OCV voltage is used to read the table value and compare with the current integrated value.

9 is a test result showing a balanced state at the time of charging through the battery management system according to the present invention, and FIG. 10 is a test result showing a balanced state at the time of discharging through the battery management system according to the present invention.

Battery management system according to the present invention, using a bi-directional coupled multi flyback active balancing method, as shown in Table 1, compared to the existing active balancing method (see Fig. 1), as compared to the existing active balancing method (50) reduced by about 50% It can be significantly reduced, the number of semiconductors for the switch is reduced by 50% than the method of Figure 1 (a), the cost is reduced by using a smaller quantity than the method of Figure 1 (b) and (c).

In addition, the battery management system according to the present invention reduces the power loss in the switch semiconductor because the voltage to be controlled is low, and the product life and reliability is improved in proportion thereto.

In general, it is possible to maintain the cells of a large capacity battery more evenly, reduce the cost, and improve the product life and reliability to secure product competitiveness.

In the battery management system based on the charging current according to another embodiment of the present invention, as shown in FIGS. 11 to 15, each battery cell receives a small current through the P MOSFET after the charging is completed. In order to solve the problem that the actual balancing effect is reduced due to the RECOVERY phenomenon of the battery cell voltage because it requires a considerable time to perform the discharging method and perform the balancing accordingly, and it is a small current. By allowing the current to flow and progressing in a flashing manner to improve the heating problem, the balancing effect can be obtained greatly, and the balancing time can be saved.

The battery management system based on the charge current according to another embodiment of the present invention includes a battery discharge circuit composed of a P MOSFET and a high density low resistance for flowing a large current, and in order to increase the battery balancing effect, the middle flashes In this way, the battery discharge proceeds.

First, as an operation mode and operation description of the battery cell peripheral circuit, as shown in FIG. 12, the voltage for each battery cell is monitored by the battery cell monitoring IC LT6804 through lines C12 and C11 such as R437 and R436.

Basically, each of the 12 battery cells is monitored for voltage by the LT6804 IC, and the monitored voltage is transferred to the MCU via the ISOLATOR.

The monitored voltage is pre-programmed by an algorithm, i.e., to keep the voltage deviation value between battery cells within a certain range, the MCU sends a balancing command through the ISOLATOR.

The LT6804 receives commands from the MCU and initiates discharge for battery cells that require battery cell balancing.

P-type FETs such as Q411 and Q412 are connected to each battery, and the FET's GATE is connected to LT6804 like S11 and S12, and the FET is turned ON / OFF by keeping the PORT high and low.

When the P-type FET is turned on, the energy stored in the battery discharges through RA or RB, and the voltage of the selected battery cell drops through the discharge. As described above, when the P-type FET is within the programmed battery cell deviation value, The FET is turned off.

This repeated process adjusts the voltage of each battery cell.

As the signal voltage LEVEL SHIFT operation mode, as shown in Fig. 13, the 3.3V voltage is required on the MONITORING side and 5V is required on the MCU side, and the signal voltage of the same LEVEL is required on both sides.

Therefore, it is necessary to transmit signals with different voltages, what is needed is an isolated ISOLATOR such as UM302, and a SIGNAL CLOCK such as SCK, thus transferring data in both directions through nCS.

As shown in FIGS. 14 and 15 as the battery balancing process operation, the U101 operates with 16MHZ CLOCK SIGNAL with ATMEGA90CAN, and the MCU voltage is driven at 5V.

Initializes and monitors each battery during the initial and execution of charging and discharging, continuously monitors and continuously monitors when each cell voltage is within the programmed cell deviation.

Subsequently, when the deviation between cells with respect to the lowest battery cell voltage is out of a predetermined range, balancing is started from the most out of the out of battery cells.

Subsequently, when the balancing voltage falls within a predetermined deviation voltage, the balancing is stopped, and the battery cell that is out of balance is next balanced.

Subsequently, balancing is performed sequentially in the same manner, and when all battery cells are brought in within a predetermined range, a continuous monitoring step is performed.

The balancing current is about 1.5A, and the balancing program is operated when charging more than 85%. The balancing program is operated for 1 minute, and the maximum discharge current flows to allow each cell voltage deviation to fall within a predetermined range.

According to the battery management system based on the charging current of the present invention as described above, when charging or discharging a plurality of series connected charging cells constituting the battery, the charging and discharging voltage of the charging cells is uniformed. A battery state of charge (SOC) measurement algorithm including a charge and discharge current measurement algorithm of each cell, a charge comparison algorithm of each cell, and a voltage and charge measurement algorithm of each cell, Battery-of-state (SOH) measurement algorithm including impedance measurement algorithm, aging measurement algorithm of each cell and temperature measurement algorithm of each cell, voltage, current comparison measurement algorithm of each cell and voltage of battery pack Using battery pack monitoring algorithms, including current comparison measurement algorithms, Active battery management allows battery charge / discharge deviations to improve from 5% to 10%, to 3% to 5%, resulting in longer battery life and system built-in battery Energy storage device (ESS) can be stabilized, and large capacity battery cell can be achieved by controlling the balancing current of 5A or more through the coupled inductor and FET through the Multi Coupled Flayback Transformer and increasing the balancing efficiency by using the stored energy in the coupled inductor. Balancing is possible, cost reduction and reliability are increased by reducing the number of parts by the coupled inductor, and product size can be reduced due to the small number of parts, which can secure price competitiveness.

In the above description has been described by presenting a preferred embodiment of the present invention, the present invention is not necessarily limited thereto, and those skilled in the art to which the present invention pertains should be within the scope of the technical spirit of the present invention. It will be readily appreciated that various substitutions, modifications and variations can be made.

Claims (3)

A balancing control unit for controlling the operation of the FET composed of the P MOSFET and the N MOSFET serving as the control switch;
The balancing execution part composed of one bidirectional flyback transformer is connected to the internal winding. One side of the balancing execution part is provided between the battery cell and the battery cell, and the other side of the balancing execution part is connected between the P MOSFET and the N MOSFET. Provided;
A monitoring unit configured to monitor current and voltage for each battery cell and transmit the same to the balancing control unit;
Since P MOSFET and N MOSFET, two control switches are controlled simultaneously by one control signal, and the operation is always divided into odd battery cells and even battery cells so that balancing of adjacent battery cells is performed to prevent battery cell imbalance. A charging current based battery management system. The system of claim 1, wherein the charging current based battery management system comprises: measuring the total voltage and current of the battery after initialization, and then measuring the voltage and current of each battery cell; Then, the maximum charge amount, the minimum charge amount, and the average charge amount of the even-numbered battery cells are measured; Then, the maximum charge amount, the minimum charge amount, and the average charge amount of the odd-numbered battery cells are measured; Subsequently, the maximum charge amount, the minimum charge amount relative to the average charge amount of the charge amount is determined from the charge amount of each battery cell to select the battery cells requiring balancing; Subsequently, after performing balancing on the selected battery cells, the charging current-based battery management system is configured to perform balancing by selecting a maximum charge amount and a minimum charge amount continuously in comparison with the average charge amount. The system of claim 2, wherein the charge current based battery management system comprises: measuring a change in the internal impedance of each battery cell to measure the life of the battery cell; Charge current-based battery management system, characterized by measuring the overall temperature affected by the heat generated by the internal impedance and the external environment during the charging / discharging of the battery cell using an NTC element whose resistance value changes with temperature.

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