KR20050048028A - Method of calculating state of charge for supercapacitor - Google Patents

Abstract

Disclosed is a method of estimating energy storage of a supercapacitor. In the method of estimating the energy storage amount of the disclosed supercapacitor, the method of estimating the energy storage amount of the supercapacitor in the power system to which the supercapacitor is applied is an initial energy storage estimation method using an open voltage according to Equation 3 below.

[Equation 3]

Where {C} _ {b}; Capacitance [F]

 {V} _ {sc}; Supercapacitor bank voltage,

; Max operating voltage

According to the present invention, the reliability of the energy storage amount (SOC) estimate is improved, the energy storage amount can be estimated quickly, and the safety is enhanced by overvoltage protection.

Description

Estimation of energy storage of supercapacitors {METHOD OF CALCULATING STATE OF CHARGE FOR SUPERCAPACITOR}

The present invention relates to a method of estimating energy storage of a supercapacitor, and more particularly, to a method of estimating energy storage of a supercapacitor for improving reliability of a state of charge (SOC) estimate.

Existing environmentally friendly vehicles (EVs, HEVs, and FCEVs) that use batteries as energy sources are critical to knowing the energy storage capacity (SOC) of an energy source in order to control efficient vehicle energy flow. Therefore, there are many algorithms for determining the energy storage of a battery, but the basic principle is to integrate the current value charged / discharged in the battery.

However, a supercapacitor, which is attracting attention as a new energy source, does not have an appropriate algorithm for estimating energy storage.

On the other hand, the supercapacitor is a device capable of inputting and outputting a large current, unlike a battery, and is not affected by the magnitude of the charge / discharge current value, but is an energy storage device in which the magnitude of the stored voltage value is very important. Overvoltage charge protection of the supercapacitor is important.

In addition, in order to determine the energy storage amount of the supercapacitor, there are the following problems when integrating a current value charged / discharged into an existing energy source (battery).

If the current integration error increases during the operation of the supercapacitor, an energy storage correction or reset algorithm is required, and if an energy storage drop occurs, the system may stop working. If used to manage supercapacitors, overvoltage damage may occur.

In addition, since the supercapacitor is an energy storage device having a very fast dynamic characteristic compared to a battery, a fast estimation of the energy storage value is required, but the method of integrating the current value has a slow dynamic characteristic.

In the energy storage estimation method, as shown in FIG. 1, a power disconnection unit (PDU) 1 between a supercapacitor bank 11 and a bi-directional DC / DC converter 12 input terminal 1 is shown. According to On / Off of (13), it is divided into two modes.

First, an initial energy storage estimation method (before PDU1 (13) ON) using an open circuit voltage is given by Equation 1 below.

[Equation 1]

,

The energy storage estimation method (After PDU1 (13) ON) in the operation mode is given by Equation 2 below.

[Formula 2]

Where {i} _ {sc}; Supercapacitor bank (11) terminal current

Here, the current signal is 1) during monitoring (Boost mode), {i} _ {sc} = (-) (Negative)

2) During generating (buck mode), {i} _ {sc} = (+) (Positive)

And {V} _ {sc}; Voltage of the supercapacitor bank 11,

; Maximum operating voltage, {C} _ {b}; Capacitance [F]

The conventional method as described above is a method of integrating a current value, but since the current does not flow in the initial state (PDU1 (13) off state), integration is impossible. In this case, the energy store needs to use the stored energy store just before the system is turned off, or find a new one.

The present invention was created to solve the above problems, by applying a capacitor storage energy equation that does not require integration to improve the reliability of the estimated energy storage value, to estimate the fast energy storage amount, and to improve safety by overvoltage protection The purpose of the present invention is to provide a method for estimating the energy storage of a supercapacitor.

Energy storage amount estimation method of the supercapacitor of the present invention for achieving the above object, the initial energy storage amount estimation method using the open voltage of the method of estimating the energy storage amount of the supercapacitor in the power system to which the supercapacitor is applied It is characterized by thing by three.

[Equation 3]

Where {C} _ {b}; Capacitance [F]

 {V} _ {sc}; Supercapacitor bank voltage,

; Max operating voltage

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to the description, the supercapacitor is not significantly influenced by the magnitude of the charge / discharge current value unlike the battery, but is an energy storage element in which the magnitude of the stored voltage value is very important, and overvoltage charging protection of the supercapacitor during operation is important.

The method for estimating the energy storage amount of a supercapacitor according to the present invention proposes an effective energy storage amount estimation method using a supercapacitor characteristic in which stored energy depends on a voltage value and enables fast charging / discharging of high power.

In the method of estimating the energy storage amount of a supercapacitor according to the present invention, an energy storage amount is obtained by using an instantaneous voltage (Vsc) value without using a method of integrating a conventional current value and utilizing characteristics as an energy source having fast dynamic characteristics. Estimate

This will be described in more detail as follows.

In the method of estimating the energy storage amount of the supercapacitor according to the present invention, referring to FIG. 1 and FIG. 2, the PDU1 (which serves to cut off the power of the system between the supercapacitor bank 11 and the bidirectional converter 12) According to On / Off of 13), it is divided into two modes.

First, among the methods of estimating the energy storage of the supercapacitor in the power system to which the supercapacitor is applied, the initial energy storage estimation method using the open voltage is based on Equation 3 below.

[Equation 3]

Where {C} _ {b}; Capacitance [F]

 {V} _ {sc}; Supercapacitor bank (11) voltage,

; Max operating voltage

In the method of estimating the energy storage amount of the supercapacitor in the power system to which the supercapacitor is applied, the energy storage amount estimating method in the power system operation is given by Equation 4 below.

[Expression 4]

Here, the current signal is 1) at the time of monitoring (boost mode), {i} _ {sc} = (−)

2) During generating (buck mode), {i} _ {sc} = (+)

And {i} _ {sc}; Supercapacitor bank (11) terminal current

 {V} _ {sc}; Supercapacitor bank (11) voltage,

; Maximum operating voltage,

 {R} _ {c}; Equivalent Series Resistance (ESR)

On the other hand, the battery is a device that can not know the exact energy storage value only by the voltage value, but the capacitor can estimate the energy storage value using the voltage value (Vsc) measured across the capacitor because the stored energy depends on the voltage value.

The energy stored in the capacitor can be obtained by multiplying the current value by the time, but the current value is not known in the PDU1 (13) off state, and only the capacitor terminal voltage is known. Used as capacitor storage energy type.

Using Equation 3 above, this equation can be used instantaneously without the need for integration over time.

The reason why the initial SOC and the operation SOC are distinguished is explained.

The energy storage amount (SOC) is obtained, and the reason for the division into the on / off state of the PDU 1 is to distinguish between the case where there is a current flow and the case there is no current flow in the system. However, when using the method of estimating the energy storage amount of the supercapacitor according to the present invention, it is possible to generalize to the case of the estimation method (Equation 4 above) which is an operation SOC.

That is, since the initial SOC has a current value of zero, the initial SOC estimation equation and the operating SOC estimation equation are the same. In the conventional estimation method, the current value is divided into two modes in order to distinguish the integral over time from being impossible when the PDU1 13 is off.

Among the contents suggested by the conventional estimation method, only the operation SOC estimation method is a conventional estimation method, and there may be various methods for the initial SOC estimation method.

As described above, the method of estimating the energy storage amount of the supercapacitor according to the present invention is a SOC reset when the current integration error increases during system operation, which is a problem of the conventional method of using the integral of the charge / discharge current {i} _ {sc}. The instantaneous voltage (Vsc) of the supercapacitor was used to solve the problem that the algorithm is needed and the dynamic characteristics of the SOC estimate are slow.

Accordingly, there is no problem of SOC drop during system operation due to error accumulation because no current integration is performed. By using the instantaneous voltage (Vsc) value, the overvoltage protection of the system is possible, and the dynamic characteristics of the SOC estimation value suitable for the system requiring fast response characteristics are fast. In addition, since there is no integration process, the burden on the controller can be reduced.

On the other hand, Figure 3 is a circuit diagram showing a control structure of a parallel hybrid power system to which a supercapacitor is applied.

As described above, the method of estimating the energy storage amount of the supercapacitor according to the present invention has the following effects.

Reliability of energy storage (SOC) estimates is improved, fast energy storage can be estimated, and overvoltage protection enhances safety.

This reduces the controller burden associated with reducing energy storage calculations and eliminates the need for additional processes.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

1 is a schematic system configuration diagram applying a supercapacitor.

2 is a power flow diagram of the system after the PDU1 relay is turned on.

3 is a circuit diagram illustrating a control structure of a parallel hybrid power system to which a supercapacitor is applied.

<Description of the symbols for the main parts of the drawings>

11.Supercapacitor Bank

12. Bidirectional Converter

13. PDU1

Claims (2)

The method of estimating the energy storage amount of the supercapacitor by using an open voltage among the methods of estimating the energy storage amount of the supercapacitor in the power system to which the supercapacitor is applied is based on Equation 3 below. [Equation 3] Where {C} _ {b}; Capacitance [F]  {V} _ {sc}; Supercapacitor bank voltage, ; Max operating voltage The method of estimating the energy storage amount of the supercapacitor in the power system to which the supercapacitor is applied, the method of estimating the energy storage amount of the supercapacitor according to Equation 4 below. [Expression 4] Here, the current signal is 1) at the time of monitoring (boost mode), {i} _ {sc} = (−) 2) During generating (buck mode), {i} _ {sc} = (+) And {i} _ {sc}; Supercapacitor Bank Terminal Current  {V} _ {sc}; Supercapacitor bank voltage, ; Maximum operating voltage,  {R} _ {c}; Equivalent Series Resistance