KR101261149B1 - Method for estimating state of charge of battery - Google Patents

Abstract

Disclosed is a method of estimating remaining battery capacity (SOC), which allows the battery sensor to accurately calculate the remaining capacity when the battery sensor is first connected to the battery.
The method for estimating the remaining capacity of the disclosed battery may include: checking whether the battery is in an initial connection state and determining whether the battery is in a discharge state or a charge state when the connection state is an initial connection state; Measuring the battery voltage when the discharge state is determined and comparing it with a predetermined stabilization determination voltage to determine whether to stabilize the battery; Calculating a magnitude of a voltage drop by calculating a magnitude of a discharged current; Calculating an open circuit voltage using the calculated voltage drop voltage and the measured voltage; After calculating the initial remaining capacity corresponding to the calculated open circuit voltage, and calculating the final remaining capacity by calculating the initial remaining capacity and the predetermined destabilization coefficient.

Description

Method for estimating remaining battery capacity {Method for estimating state of charge of battery}

The present invention relates to estimating the remaining capacity of a battery (SOC), and more particularly, to a method of estimating the remaining capacity of a battery to accurately calculate the remaining capacity when the battery sensor is first connected to the battery. .

In general, hybrid vehicles and fuel cell hybrid vehicles that use batteries as energy buffers, as well as pure electric vehicles that use only batteries as energy sources, are one of the main components of vehicle quality. In particular, since the battery serves as an auxiliary energy source for a vehicle that assists in outputting the engine or accumulates the generated energy, the control technology is very important.

Electric vehicles using high voltage batteries, such as hybrid vehicles and fuel cell vehicles, are equipped with a battery management system (BMS) that manages the overall condition of the battery. It prevents premature shortening and supports generation control and driving control by notifying SOC information of battery to vehicle controller performing comprehensive control.

The main functions of the battery management system include estimating the remaining capacity of the battery and detecting full charge, balancing the voltage between each cell module, controlling the maximum charge and discharge voltage according to the remaining capacity of the battery, safety management and diagnosis, and cooling control. Can be mentioned. Among them, the most important technology for driving a vehicle is calculating the battery's remaining capacity.

Accurate estimation of the remaining capacity of the battery enables accurate implementation of a hybrid system that charges the battery when surplus energy is generated and discharges when a high output is needed to meet the required output, thereby maximizing energy reduction and vehicle operation efficiency. Because it can.

If the remaining capacity is calculated incorrectly, it can lead to a dangerous situation as well as a reduction in the operational efficiency of the vehicle. For example, if the actual capacity is 80% but the calculated capacity is 30%, the vehicle controller may determine that charging is necessary and overcharge the battery, or vice versa. As a result, the battery may be ignited or exploded by the overcharge or overdischarge as described above, resulting in a very dangerous situation.

The prior art for measuring the initial remaining capacity of the battery is disclosed in Korean Patent Laid-Open Publication No. 10-1998-0012690 (published on April 30, 1998) (name of the invention: the initial remaining capacity measuring device of the electric vehicle battery).

The disclosed prior art can measure and confirm the remaining capacity of the current battery immediately before starting the vehicle by using the method of calculating the initial remaining capacity of the battery by calculating the battery potential and the battery temperature measured when the battery sensor is first connected to the battery. It would be.

1. Publication No. 10-1998-0012690 (published Apr. 30, 1998)

However, the above conventional technology does not consider various environments and simply calculates the remaining capacity using only the measured voltage when the battery sensor measuring the voltage of the battery is first connected to the battery. have.

In particular, the state of charge according to the battery open circuit voltage, the degree of voltage drop between the actual battery voltage and the sensor, the internal resistance value of the battery, and whether the first connected battery is stabilized absolutely affect the estimation of the remaining capacity. It is not optimal for estimating the remaining capacity because it does not consider this various environmental information.

In addition, since the conventional technology estimates the remaining capacity of the battery by applying the same remaining capacity calculation logic at all times regardless of whether the battery and the battery sensor are initially connected, it cannot be regarded as an optimal remaining capacity estimation.

Accordingly, the present invention has been proposed to solve various problems occurring in the method of estimating the remaining capacity of the conventional battery as described above.

An object of the present invention is to provide a method for estimating the remaining capacity of a battery to accurately calculate the remaining capacity when the battery sensor is first connected to the battery.

Another object of the present invention is to accurately calculate the remaining capacity when the battery sensor is first connected to the battery, to prevent the control error caused by the incorrect remaining capacity, loss caused by not performing the control due to the incorrect remaining capacity The present invention provides a method for estimating the remaining capacity of a battery so as to prevent the occurrence of the problem.

According to a preferred embodiment of the present invention for achieving the above objects "method of estimating the remaining capacity of the battery",

Checking whether the battery is in an initial connection state, and determining whether the battery is in a discharge state or a charge state when the connection state is an initial connection state;

Measuring the battery voltage when the discharge state is determined and comparing it with a predetermined stabilization determination voltage to determine whether to stabilize the battery;

Calculating a magnitude of a voltage drop by calculating a magnitude of a discharged current;

Calculating an open circuit voltage using the calculated voltage drop voltage and the measured voltage;

And after calculating the initial residual capacity corresponding to the calculated open circuit voltage, calculating the final residual capacity by calculating the initial residual capacity and a predetermined destabilization coefficient.

In addition, the "method of estimating the remaining capacity of the battery" according to the present invention,

Setting the initial remaining capacity to a specific value in the charging state as a result of the checking;

Counting a charging time after determining an initial connection charging time setting value;

The method may further include classifying and applying remaining capacity calculation logic according to the charging current size.

The step of applying the remaining capacity calculation logic separately,

A first remaining capacitance calculation logic is applied when the charging current is present between the first and second reference currents, and a second residual when the charging current is present between the second reference current and the third reference current. Capacitance calculation logic is applied, and when the charging current is equal to or less than the third reference current, a third remaining capacity calculation logic is applied.

In addition, the "method of estimating the remaining capacity of the battery" according to the present invention,

After calculating the last remaining capacity, the method further includes the step of entering a sleep mode if the sleep state, and counting the sleep time.

In addition, the "method of estimating the remaining capacity of the battery" according to the present invention,

If the connection state of the battery is not the first connection state, by checking whether a specific sleep time has elapsed, determining that the battery is stabilized when the specific sleep time has elapsed, and further comprising updating the remaining capacity.

According to the present invention described above, there is an advantage that can accurately calculate the remaining capacity in the initial connection state of the battery and the battery sensor.

It also prevents problems with control errors due to inaccurate information on the initial connection of the battery and battery sensor, and also prevents loss caused by not performing battery charge and discharge control under the assumption that the information is incorrect. There are advantages to it.

1 is a schematic configuration diagram of an apparatus for estimating remaining capacity of a battery to which the present invention is applied;
2 is a flowchart showing a method of estimating remaining capacity of a battery according to the present invention;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a schematic configuration diagram of an apparatus for estimating remaining capacity of a battery to which the present invention is applied, and includes a battery 110, a battery sensor 120, a battery management system 130, and a vehicle controller 140. The battery sensor 120 may be included in the battery management system 130.

The battery sensor 120 measures the voltage of the battery 110, and the battery management system 130 collectively manages the overall state of the battery in an electric vehicle using a high voltage battery, such as a hybrid vehicle or a fuel cell vehicle. As a management role, the present invention performs a method of estimating the initial remaining capacity of the battery. The vehicle controller 140 is connected to the battery management system 130 to prevent the early reduction of the battery life, to perform a comprehensive control, the remaining capacity (SOC) information of the battery transmitted from the battery management system 130 Therefore, power generation control and driving control are performed.

2 is a flowchart illustrating a method for estimating remaining capacity of a battery according to the present invention, and checking whether the battery is connected to the battery for the first time, and checking whether the battery is in the discharge state or the charged state when the connection state is the first connection (S101). S105); Measuring the battery voltage in the discharged state when the result of the checking is determined, and determining whether the battery is stabilized by comparing with a predetermined stabilization determination voltage (S107 to S111); Calculating a magnitude of a voltage drop by calculating a magnitude of a discharged current (S113); Calculating an open circuit voltage using the calculated voltage drop voltage and the measured voltage (S115); Calculating an initial residual capacity after calculating an initial residual capacity corresponding to the calculated open circuit voltage, and calculating a final residual capacity by calculating the initial residual capacity and a predetermined destabilization coefficient (S117); After the final remaining capacity is calculated, a sleep mode is entered, and the sleep time is counted (S119 to S121).

In addition, preferably the "method of estimating the remaining capacity of a battery" according to the present invention,

Setting the initial remaining capacity to a specific value when it is in a charged state (S127 to S129); Counting a charging time after determining an initial connection charging time setting value (S131 ˜ S135); The method further comprises the step of applying the remaining capacity calculation logic according to the charging current size (S137 ~ S139).

The step of applying to distinguish the remaining capacity calculation logic,

A first remaining capacitance calculation logic applied when the charging current is present between the predetermined first and second reference currents, and a first applied when the charging current is present between the predetermined second reference current and a third reference current. 2 remaining capacity calculation logic; And a third remaining capacity calculation logic applied when the charging current is equal to or smaller than the third reference current.

Further, more preferably "method of estimating remaining capacity of a battery" according to the present invention,

If the battery is not connected for the first time, check whether the specific sleep time has elapsed, determine that the battery has stabilized when the specific sleep time has elapsed, and measure the voltage of the battery to update the remaining capacity. It further comprises the step (S123 ~ S125).

In the method of estimating the remaining capacity of the battery according to the present invention, the battery sensor 120 first measures the voltage of the battery 110 when the battery 110 is connected, and transmits the voltage to the battery management system 130.

The battery management system 130 determines a state such as whether the battery 110 and the battery sensor 120 are initially connected, and the accuracy of the remaining capacity (SOC) when the battery sensor 120 is first connected to the battery 110. In order to improve the performance of the battery by considering the environmental information such as the state of charge according to the battery open circuit voltage, the degree of voltage drop between the actual battery voltage and the battery sensor, the internal resistance of the battery, and the first connected battery may not be stabilized. The remaining capacity is estimated. The estimated remaining capacity value is transferred to the vehicle controller 140 so that power generation control and travel control are performed.

Hereinafter, a method of estimating the remaining capacity in the battery management system 130 will be described in detail.

First, when the battery voltage is measured and transferred from the battery sensor 120 in step S101, it is checked whether the battery sensor 120 and the battery 110 are connected for the first time. This confirmation can be confirmed with the initialization, and can be determined by searching the initialization count value Ini_cnt.

If it is determined that the battery sensor and the battery are first connected as a result of this determination, the flow advances to step S103 to set the initialization count (Ini_cnt) to 1 (Ini_cnt = 1).

Next, the process moves to step S103 to check whether the battery is in a discharge state. Normally, the first connection, but the discharge state, to determine whether the actual discharge. This can be confirmed whether or not the discharge by measuring the current (I).

If it is determined that the discharge state is the result of the check, the process proceeds to step S107 to check whether the initialization count value is 1, and if the verification count value is 1, the process proceeds to step S109 and sets the initialization count value to 0 (Ini_cnt = 0).

Thereafter, the process moves to step S111 to measure the voltage to determine whether the battery is stabilized. That is, the voltage is measured to be the measured voltage Vm, and the measured voltage is compared with the stabilization determination voltage Vk for determining whether the battery is stabilized. If the stabilization determination voltage is greater than the measured voltage, the battery is not stabilized. If not, the flow proceeds to step S113 to calculate the degree of voltage drop according to the magnitude of the discharge current.

For example, since the internal resistance value R1 or R2 of the battery is known, the voltage drop Vd is calculated by calculating the internal resistance value and the measured current I (Vd = I × R1, Vd = I × R2). ).

In operation S115, the open circuit voltage V is calculated using the dropped voltage Vd and the measured voltage Vm (V = Vm + Vd).

When the open circuit voltage calculation is completed, go to S117 to calculate the initial remaining capacity SOCm = aV + b corresponding to the calculated open circuit voltage, and the predetermined destabilization coefficient X from the calculated initial remaining capacity SOCm. %) Is calculated (SOCm-X%) to calculate the final remaining capacity (SOC).

In this way, the final remaining capacity accurately calculated at the time of initial battery connection is transferred to the vehicle controller 140 to be used for power generation control and driving control.

In step S119, the vehicle controller 140 determines whether the vehicle controller 140 continues to request the remaining capacity information, that is, whether it is in the sleep state. If it is in the sleep state, the process moves to step S121 to enter the sleep mode, and the sleep time is determined. Count (slp_t_cnt ++).

On the other hand, when the battery and the battery sensor are initially connected but in the charged state, the process proceeds to step S127 and checks whether the initialization count is 1 (Ini_cnt = 1). Is set to a specific value (SOC = A%), which means that the initial remaining capacity is initially set to a certain value since no information can be trusted if it is the first connection but charging.

After that, the process moves to step S131 to measure the current (I). If the current is greater than 0, the process moves to step S133 to determine the initial connection charge time setting value Tmin. That is, it is checked whether the charging time chg_t_cnt is smaller than the charging time setting value Tmin, and if the charging time is smaller than the charging time setting value, the process moves to step S135 to count the charging time.

In addition, it proceeds to step S137 to check whether the charging current (I) is greater than the first reference current (M), if the charging current (I) is greater than the first reference current (M) the magnitude of the charging current The remaining capacity is estimated by selectively applying various remaining capacity calculation logics.

For example, when the charging current I is present between the predetermined first reference current M and the second reference current N (M≥I> N), a first remaining capacity calculation logic is applied and the charging is performed. When the current exists between the second reference current N and the third reference current P, which are predetermined (N≥I> P), a second remaining capacity calculation logic is applied, and the charging current is applied to the third reference. If the current P is less than or equal to (I≤P), the third remaining capacity calculation logic is applied.

In addition, the present invention may not be perfect as the method for calculating the remaining capacity as described above, if the battery is not the first connection state, go to step S123 to check whether the sleep time (slp_t_cnt) is a predetermined battery stabilization time (K) has elapsed. When the sleep time has passed the stabilization time, it is determined that the battery is stabilized, and the process proceeds to step S125 to perform voltage measurement again to calculate the remaining capacity once again.

According to the present invention, the battery and the battery sensor can accurately calculate the remaining capacity in the initial connection state, it is possible to prevent the problem of generating a control error due to incorrect information in the initial connection, it is assumed that the information is incorrect It is also possible to prevent the loss caused by not performing the control itself.

110: battery 120: battery sensor
130: battery management system 140: vehicle controller

Claims (5)

In the method for estimating the remaining capacity (SOC) of the battery,
(a) checking whether the battery is in an initial connection state and checking whether the connection state is a discharge state or a charge state when the connection state is the first connection state;
(b) measuring the battery voltage when the discharge state is discharged and comparing the battery with a predetermined stabilization determination voltage to determine whether the battery is stabilized;
(c) calculating the magnitude of the voltage drop by calculating the magnitude of the discharged current;
(d) calculating an open circuit voltage using the calculated voltage drop voltage and the measured voltage;
(e) calculating an initial remaining capacity after calculating an initial remaining capacity corresponding to the calculated open circuit voltage, and calculating a final remaining capacity by calculating the initial remaining capacity and a predetermined destabilization coefficient. Estimation method.
The method of claim 1, further comprising: setting an initial remaining capacity to a specific value when the connection state is determined as a result of checking the connection state;
Counting a charging time after determining an initial connection charging time setting value;
The method for estimating the remaining capacity of a battery, characterized in that it further comprises the step of applying the remaining capacity calculation logic according to the magnitude of the charging current. The method of claim 2, wherein the step of applying the remaining capacity calculation logic separately,
The first remaining capacitance calculation logic is applied when the charging current is present between the first and second reference currents, and when the charging current is present between the second reference current and the third reference current. 2. A method of estimating remaining capacity of a battery, wherein the remaining capacity calculation logic is applied, and a third remaining capacity calculation logic is applied when the charging current is equal to or smaller than the third reference current.
The method according to claim 1,
And calculating a final remaining capacity, and entering a sleep mode when the sleep state is in a sleep state, and counting a sleep time.
The method according to claim 1,
(f) is provided between the steps (a) and (b), and if the connection state of the battery is not the first connection state, it is determined whether a specific sleep time has elapsed. It is determined that the stabilization, and updating the remaining capacity further comprises the step of estimating the remaining capacity of the battery.

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