CN105785270A - Measurement method for measuring energy state operation interval of battery string - Google Patents

Abstract

The present invention provides a method for measuring the energy state of a battery string in an operating range, comprising the following steps: performing a constant power discharge test on the battery string, and determining the energy state of the constant power according to the voltage change rate of the battery string and the battery voltage range The lower limit of operation; the constant power charging test is carried out on the battery string, and the upper limit of the energy state operation of the constant power is determined according to the voltage change rate of the battery string and the battery voltage extreme difference; through the energy state operation The lower limit value and the upper limit value of the energy state operation determine the operation range of the energy state of the battery string. By measuring the battery string charging and discharging voltage and the battery voltage extreme difference, the energy state operating range of the battery string at a certain power can be analyzed and obtained, in order to evaluate the energy state operating range of the available power of the energy storage unit, and master the charging The discharge capacity provides a technical means, and the provision of this parameter (energy state operating range) is of great significance for the precise control of the energy storage unit and the energy storage power station.

Description

A method for measuring the energy state of battery strings in the operating range

technical field

The invention relates to the field of battery state detection, in particular to a method for measuring the energy state of a battery string in an operating interval.

Background technique

With the continuous increase of wind power and photovoltaic projects, energy storage technology, as an effective means to suppress the volatility and intermittency of new energy power generation, has also developed rapidly. The energy storage unit is the basic unit of the energy storage power station. The energy storage unit consists of multiple battery packs connected in series and parallel, as shown in Figure 15.

The SOE (StateOfEnergy, state of energy, hereinafter referred to as SOE) operating range is an important operating parameter of the energy storage unit. The wider the SOE operating range, the more charge and discharge capacity the energy storage unit can provide. The narrower the SOE operating range, the more energy storage units can provide. The less the charge and discharge capacity. Since the energy storage unit is composed of multiple battery strings, the SOE operating range of the energy storage unit is determined by the SOE of the battery strings, so measuring the SOE operating range of the battery strings is an important factor for determining the SOE operating range of the energy storage unit and evaluating the operating capacity of the energy storage unit. parameter. At the same time, since different charging and discharging powers correspond to different SOE operating intervals, the present invention proposes a method for measuring the SOE operating interval of an energy storage lithium battery string for a constant charging and discharging power, which provides a method for measuring the SOE operating interval of an energy storage lithium battery string. refer to.

Contents of the invention

The purpose of the present invention is to provide a method for measuring the SOE operating range of a battery string, by analyzing the voltage curve and the battery voltage range curve for charging and discharging the measured battery string under a constant power condition, the battery string under this power can be obtained The SOE operating range of the battery string provides technical support for evaluating the SOE operating range of the available power of the battery string and mastering the charging and discharging capabilities of the battery string.

The technical solution of the present invention is to provide a battery string SOE operating range measurement method, comprising the following steps:

Carry out a constant power discharge test on the battery string, and determine the lower limit of the energy state operation of the constant power according to the voltage change rate of the battery string and the battery voltage extreme difference;

Carrying out the constant power charging test on the battery string, and determining the upper limit of the constant power energy state operation according to the voltage change rate of the battery string and the battery voltage range;

The operating interval of the energy state of the battery string is determined by the energy state operating lower limit value and the energy state operating upper limit value.

By measuring the battery string charging and discharging voltage and battery voltage extreme difference, the SOE operating range of the battery string at a certain power can be analyzed and obtained, in order to evaluate the SOE operating range of the available power of the energy storage unit, and grasp the charging and discharging capacity of the energy storage unit Technical means are provided, and the provision of the parameter (SOE operating range) is of great significance for the precise control of the energy storage unit and the energy storage power station.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort. In the attached picture:

Fig. 1 is a flow chart of the method for measuring the SOE operating interval in the present invention.

Fig. 2 is the curve of battery string voltage and voltage change rate during constant power discharge in the present invention.

Fig. 3 is the PNGV model battery structure in the present invention.

Fig. 4 is the battery voltage extreme difference curve during constant power discharge in the present invention.

Fig. 5 is a curve of battery string voltage and voltage change rate during constant power charging in the present invention.

Fig. 6 is the extreme difference curve of battery voltage during constant power charging in the present invention.

Fig. 7 is a battery string voltage-power curve during 42kW constant power charging in an embodiment of the present invention.

Fig. 8 is a battery string voltage-SOE curve during 42kW constant power charging in an embodiment of the present invention.

Fig. 9 is a battery string voltage-change rate curve during 42kW constant power charging in an embodiment of the present invention.

Fig. 10 is a battery voltage range-SOE curve during 42kW constant power discharge in an embodiment of the present invention.

Fig. 11 is a voltage-power curve of battery strings during 42kW constant power discharge in an embodiment of the present invention.

Fig. 12 is a battery string voltage-SOE curve during 42kW constant power discharge in an embodiment of the present invention.

Fig. 13 is a curve of battery string voltage-voltage change rate during 42kW constant power discharge in the embodiment of the present invention.

Fig. 14 is a battery voltage range-SOE curve during 42kW constant power charging in an embodiment of the present invention.

Fig. 15 is a schematic diagram of the composition of an energy storage unit in the prior art.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments and descriptions of the present invention are used to explain the present invention, but not to limit the present invention.

Fig. 1 is a flow chart of a battery string SOE operating interval measurement method provided by the present invention, including the following steps:

S101: Carry out a constant power discharge test on the battery string, and determine the lower limit value of the constant power energy state operation according to the voltage change rate of the battery string and the battery voltage range;

S102: Perform the constant power charging test on the battery string, and determine the upper limit of the constant power energy state operation according to the voltage change rate of the battery string and the battery voltage range;

S103: Determine the operating interval of the energy state of the battery string according to the lower limit value of the energy state operation and the upper limit value of the energy state operation.

In an embodiment of the present invention, performing a constant power discharge test on the battery strings, and determining the SOE operation lower limit value of the constant power according to the battery string voltage and the battery voltage range, includes: obtaining during the discharge plateau period The average value of the voltage change rate ΔU _dis within this time period, when the voltage change rate of the battery string at the end of discharge reaches the SOE value corresponding to 2×ΔU _dis , the lower limit of the SOE operation SOE _min1 is determined when the discharge power is determined.

In an embodiment of the present invention, performing a constant power discharge test on the battery strings, determining the SOE operation lower limit value of the constant power according to the voltage of the battery strings and the battery voltage range, also includes: when the battery voltage at the end of the discharge When the extreme difference reaches the limit value U _Rdis , the SOE value corresponding to the battery voltage extreme difference U _Rdis at this time is determined to be the SOE operation lower limit value SOE _min2 at this discharge power.

In an embodiment of the present invention, if SOE _min1 <SOE _min2 , the SOE operation upper limit is SOE _min2 .

If SOE _min1 >SOE _min2 , the upper limit of SOE operation is SOE _min1 .

In an embodiment of the present invention, performing the constant power charging test on the battery string, and determining the SOE operation upper limit of the constant power according to the voltage of the battery string and the battery voltage range, includes: Calculate the average value of the voltage change rate ΔU _ch within this time period. When the voltage change rate of the battery string reaches the SOE value corresponding to 2×ΔU _ch at the end of charging, determine the upper limit of the energy state operation SOE _max1 for the charging power.

In an embodiment of the present invention, performing the constant power charging test on the battery string, determining the SOE upper limit of the constant power operation according to the battery string voltage and the battery voltage range, further includes: when discharging When the battery voltage extreme difference reaches the limit value U _Rch at the end, the SOE value corresponding to the battery voltage extreme difference U _Rch at this time determines the upper limit SOE _max2 of the energy state operation at the charging power.

In an embodiment of the present invention, if SOE _max1 <SOE _max2 , the upper limit of the SOE operation is SOE _max1 .

If SOE _max1 >SOE _max2 , the upper limit of SOE operation is SOE _max2 .

By measuring the battery string charging and discharging voltage and battery voltage extreme difference, the SOE operating range of the battery string at a certain power can be analyzed and obtained, in order to evaluate the SOE operating range of the available power of the energy storage unit, and grasp the charging and discharging capacity of the energy storage unit Technical means are provided, and the provision of the parameter (SOE operating range) is of great significance for the precise control of the energy storage unit and the energy storage power station.

The upper and lower limits of SOE operation will be calculated by describing the charging and discharging processes in detail below.

(1) Determination of the lower limit of SOE operation when the battery string is discharged with constant power P

a) Determine the lower limit of SOE operation according to the battery string voltage

The battery string is discharged with a constant power P, and the battery string voltage change rate is calculated according to the battery string voltage, and the battery string voltage and voltage change rate curves are drawn as shown in Figure 2.

Fig. 3 is the PNGV model battery structure in the present invention. As shown in Figure 3, U _OC is an ideal voltage source, indicating the open circuit voltage of the battery, which is only related to the battery SOE, but not to the battery charge and discharge state; R ₀ is the ohmic internal resistance of the battery, which is only related to metal parts such as battery poles; R _P is the battery polarization resistance, and C _P is the battery polarization capacitance, which is related to the polarization of the battery during charging and discharging; C _b is mainly used to describe the voltage change of the battery in the initial stage of charging or discharging. It can be seen from Fig. 3 that during the battery string discharge process, the battery terminal voltage UI is composed of the battery open circuit voltage U _OC , ohmic voltage U ₀ , capacitor voltage U _b and polarization voltage _UP , as shown in formula 1.

U _I ＝ U _OC -U ₀ -U _b -U _P (1)

Combining Figure 3 and Equation 1, it can be seen that at the end of the discharge process, due to the small change in SOE, U _OC is basically unchanged. At the same time, the discharge current changes little in the constant power charging mode, and U ₀ does not change significantly at the end of discharge , In addition, the energy of C _b has been released at the initial stage of discharge, and U _b is 0 at the end of discharge, so the change of terminal voltage U _I at the end of discharge mainly _reflects the change of polarization voltage UP. At the end of discharge, because the active material of the battery has basically reacted, the discharge capacity is weakened, and the polarization phenomenon is intensified, resulting in a sharp increase in the polarization voltage U _P , which causes a rapid decline in the terminal voltage U _I. Therefore, in the process of charging and discharging with constant power, When the terminal voltage U _I drops rapidly, the battery is difficult to discharge, and the corresponding SOE at this time is the lower limit of the discharge SOE operation of the power.

It can be seen from Figure 2 that the state of the battery is stable during the discharge plateau period, and the voltage change of the battery string voltage per unit time is relatively stable, so the average value ΔU _dis of the voltage change rate within this time period can be obtained. When the voltage change rate of the battery string reaches 2×ΔU _dis at the end of discharge, it is considered that the terminal voltage of the battery string begins to drop rapidly at this time, and the SOE corresponding to the limit value of the voltage change rate 2ΔU _dis is determined by the voltage of the battery string The determined SOE operating lower limit SOE _min1 of the power.

In the actual measurement process, the voltage change rate curve will appear noise as shown in Figure 2, which hinders the determination of the value of the voltage change rate ΔU _dis in the plateau period, and the determination of the position of the voltage change rate limit 2ΔU _dis on the voltage change rate curve. The voltage change rate data can be filtered, the noise on the curve can be eliminated, and the curve can be fitted in sections to obtain a smooth voltage change rate curve, so as to determine the size of ΔU _dis and the position where the voltage change rate limit 2ΔU _dis appears .

b) Determine the lower limit of SOE operation according to the extreme difference of battery voltage

The battery string is discharged with a constant power P, and the battery voltage range change rate is calculated according to the battery voltage range, and the battery voltage range and change rate curve is drawn as shown in Figure 4.

Due to the differences in the discharge performance of the single cells of the battery string, at the end of the discharge, the polarization effect of the poor-performing battery will be more obvious than that of other batteries, and the voltage will drop faster than other batteries, thereby increasing the battery voltage range. When the battery voltage changes rapidly, since the active material of the single battery with the lowest voltage has completed the reaction, it is difficult to continue discharging, which affects the discharge performance of the entire battery string discharge. At this time, the corresponding SOE is the discharge SOE of this power Operating lower limit.

It can be seen from Figure 4 that when the battery voltage extreme difference reaches the limit value U _Rdis at the end of discharge, it is the moment when the active material of the battery with the lowest voltage has basically reacted, and the SOE corresponding to the battery voltage extreme difference U _Rdis at this time is The SOE operating upper limit SOE _min2 of the power determined by the battery voltage extreme difference, the battery voltage extreme difference limit U _Rdis is provided by the manufacturer, and the battery voltage extreme difference limit U _Rdis of different manufacturers is different.

In the actual battery voltage range measurement process, if the battery voltage range curve has "burrs", the data processing method of the voltage change rate can also be used to obtain a smooth battery voltage range curve, so as to determine the limit value of the battery voltage range Where U _{Rdis occurs} on the curve.

c) Determination of the lower limit of battery string SOE operation

Take the larger value of SOE _min1 and SOE _min2 , which is the operating lower limit SOE _min of the battery string SOE under this power.

(2) Determination of the lower limit of SOE operation when the battery string is charged with constant power P

a) Determine the upper limit of SOE operation according to the battery string voltage

Charge the battery string with constant power P, calculate the battery string voltage change rate according to the battery string voltage during the test, and draw the battery string voltage and voltage change rate curve as shown in Figure 5.

Similar to the discharge process, according to Figure 5, the average value of the voltage change rate in the charging platform period ΔU _ch can be obtained, and 2×ΔU _ch is used as the limit value of the battery string voltage change rate in the final charging stage, and the corresponding SOE at this time is both the battery voltage The SOE operation upper limit SOE _max1 under the charging power determined by the extreme difference.

b) Determine the upper limit of SOE operation according to the extreme difference of battery voltage

Charge the battery string with a constant power P, calculate the battery voltage range change rate according to the battery voltage range data during the test, and draw the battery voltage range and change rate curve as shown in Figure 6.

Similar to the discharge process, U _Rch is used as the extreme difference limit of the rechargeable battery voltage, and the corresponding SOE at this time is the SOE operating upper limit SOE _max2 under the charging power determined by the battery voltage extreme difference. Generally, the limit value U _Rdis of the battery voltage extreme difference during the discharge process is the same as the limit value U _Rch of the battery voltage extreme difference during the charge process.

c) Determination of the upper limit of the battery string SOE operation

Taking the smaller value of SOE _max1 and SOE _max2 is the operating upper limit SOE _max of the SOE of the battery string under this power.

To sum up, the SOE operating interval of the battery string is determined by the SOE operating lower limit and the SOE operating upper limit.

The present invention will be specifically described below in conjunction with a specific embodiment, but it should be noted that this specific embodiment is only for better describing the present invention, and does not constitute an improper limitation of the present invention.

Taking a battery string as an example, the determination of the SOE operating range of the battery string is illustrated. The main parameters of the battery string are shown in Table 1.

Table 1 Battery String Parameters

(1) Determination of SOE _min when 42kW constant power discharge

a) Determine SOE _min1 according to battery string voltage

Discharge the battery string with a constant power of 42kW. The battery string voltage-power curve is shown in Figure 7, the battery string voltage-SOE curve is shown in Figure 8, and the battery string voltage-change rate is shown in Figure 9. As shown in Figure 9, the average value of the voltage change rate ΔU _dis in the discharge plateau period is -0.3V/s, and the limit value 2ΔU _dis of the voltage change rate of the battery string at the end of discharge is -0.6V/s. At this time, the battery string voltage U _dis is 634V, and the corresponding battery string operation lower limit SOE _min1 is 12%.

b) Determine SOE _min2 according to battery string voltage

Discharge the battery string with a constant power of 42kW, and the battery voltage range-SOE curve is shown in Figure 10. At the end of discharge, the battery voltage limit U _Rdis is 100mV, and at this time the corresponding battery string operating lower limit SOE _min2 is 17%.

c) Determination of battery string SOE _min

Taking the larger value of SOE _min1 = 12% and SOE _min2 = 17%, the SOE _min of the battery string is 17% at a power of 42kW.

(2) Determination of SOE _max during 42kW constant power charging

a) Determine SOE _max1 according to battery string voltage

Charge the battery string with a constant power of 42kW. The battery string voltage-power curve is shown in Figure 11, the battery string voltage-SOE curve is shown in Figure 12, and the battery string voltage-change rate is shown in Figure 13. As shown in Figure 13, the average value of the voltage change rate ΔU _ch during the charging platform period is 0.3V/s, and the limit value 2ΔU _ch of the voltage change rate of the battery string at the end of charging is 0.6V/s, and the battery string voltage U _ch is 701V at this time , the corresponding battery string operating upper limit SOE _max1 is 87%.

b) Determine SOE _max2 according to battery string voltage

The battery string is charged with a constant power of 42kW, and the battery voltage range-SOE curve is shown in Figure 14. At the end of charging, the battery voltage extreme difference U _Rch is 100mV, and at this time the corresponding battery string operating upper limit SOE _max2 is 87%.

c) Determination of battery string SOE _max

Taking the smaller value of SOE max1 =87% and _SOEmax2 =87%, the SOE _max of the battery string is 87% at a power of 42kW.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (7)

1. A battery string energy state operation interval measurement method, characterized in that, comprising the steps: Carry out a constant power discharge test on the battery string, and determine the lower limit of the energy state operation of the constant power according to the voltage change rate of the battery string and the battery voltage range; Carrying out the constant power charging test on the battery string, and determining the upper limit of the constant power energy state operation according to the voltage change rate of the battery string and the battery voltage range; The operating interval of the energy state of the battery string is determined by the energy state operating lower limit value and the energy state operating upper limit value. 2. The energy state operation interval measuring method according to claim 1, characterized in that, the battery string is subjected to a constant power discharge test, and the energy of the constant power is determined according to the battery string voltage and the battery voltage extreme difference The lower limit value of state operation includes: the average value of the voltage change rate ΔU _dis within the time period is obtained during the discharge plateau period, and when the voltage change rate of the battery string at the end of the discharge reaches the energy state value corresponding to 2×ΔU _dis , determine the Energy state operation lower limit value SOE _min1 when discharging power. 3. The energy state operation interval measurement method according to claim 2, characterized in that, the battery string is subjected to a constant power discharge test, and the energy of the constant power is determined according to the battery string voltage and the battery voltage extreme difference The lower limit value of state operation also includes: when the battery voltage extreme difference reaches the limit value U _Rdis at the end of discharge, the energy state value corresponding to the battery voltage extreme difference U _Rdis at this time, and the energy state operation lower limit value SOE when determining the discharge power _min2 . 4. The energy state operation interval measurement method according to claim 3, characterized in that, If SOE _min1 < SOE _min2 , the upper limit of energy state operation is SOE _min2 ; If SOE _min1 >SOE _min2 , the upper limit of energy state operation is SOE _min1 . 5. The method for measuring the energy state operating interval according to claim 1, wherein the constant power charging test is carried out on the battery string, and the constant power charging test is determined according to the battery string voltage and the battery voltage extreme difference. The upper limit value of the energy state operation of the power includes: the average value of the voltage change rate ΔU _ch within the period of time is obtained during the charging platform period, and the energy state value corresponding to the voltage change rate of the battery string at the end of charging reaches 2×ΔU _ch , to determine the upper limit value SOE _max1 of the energy state operation at the charging power. 6. The method for measuring the energy state operating interval according to claim 5, wherein the constant power charging test is carried out on the battery string, and the constant power charging test is determined according to the battery string voltage and the battery voltage extreme difference. The energy state operating upper limit of the power also includes: when the battery voltage extreme difference reaches the limit value U _Rch at the end of discharge, the energy state value corresponding to the battery voltage extreme difference U _Rch at this time, when the charging power is determined, the energy state is running up Limit SOE _max2 . 7. The energy state operation interval measurement method according to claim 6, characterized in that, If SOE _max1 <SOE _max2 , the upper limit of the energy state operation is SOE _max1 ; If SOE _max1 >SOE _max2 , the upper limit of energy state operation is SOE _max2 .