CN107122603A - Energy-storage system of accumulator life-span measuring method in a kind of micro-capacitance sensor - Google Patents

Abstract

The present invention is energy-storage system of accumulator life-span measuring method in a kind of micro-capacitance sensor, is characterized in, including in have：The corresponding relation of the depth of discharge and cycle-index and total throughout of lithium battery is analyzed, energy-storage system of accumulator life consumption model is set up；Using the fatigue life gage algorithm in existing engineering field, i.e. " tower top counting method " carries out the interception of charge and discharge cycles to energy-storage system of accumulator, calculating accumulator depth of discharge, charge and discharge cycles obtained from entering, which are substituted into, carries out the measuring and calculating of battery energy storage system life-span in life consumption model.It is simple to be applicable with scientific and reasonable, the advantages of precision of prediction is high.

Description

A life estimation method for battery energy storage system in microgrid

technical field

The invention relates to the technical field of battery energy storage, and relates to a method for measuring and calculating the life of a battery energy storage system in a microgrid.

Background technique

The battery energy storage system in the microgrid mainly matches the power between the micro power supply and the load. Due to the random fluctuation of distributed renewable energy and load, the battery energy storage system will operate in the state of frequent alternating and irregular charging and discharging. It will shorten its service life, increase its investment, and reduce the economy of the microgrid system. Therefore, it is very necessary to grasp its service life when configuring the capacity of the microgrid battery energy storage system. Therefore, it is necessary to construct a corresponding life estimation model to quantitatively analyze its life.

The life of the battery is mainly affected by factors such as temperature, charge and discharge rate, and charge and discharge depth. The life calculation method of the battery energy storage system in the microgrid in the prior art is complex and has low accuracy. How to improve the scientific rationality of the battery energy storage system life calculation method in the microgrid, simplify the process, and further improve the accuracy is a difficult problem that those skilled in the art have been eager to solve, but have not yet been solved.

Contents of the invention

The conception basis of the present invention is that, aiming at the actual situation of the application of the battery energy storage system of the micro-grid, the impact of the discharge depth of the battery and the number of charge and discharge times is mainly considered. It is considered that the total throughput of full charge and full discharge under the rated state of the battery is certain, and this is used to quantitatively characterize the service life of the battery. When the charge and discharge capacity of the battery reaches the total throughput under the rated state, it is considered that the battery life is exhausted. Based on the above ideas, the throughput of the battery under different charge and discharge depths is calculated as the charge and discharge capacity under the rated state, which is used to calculate the life of the battery.

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a scientific, reasonable, simple and applicable, and high prediction accuracy method for measuring and calculating the life of a battery energy storage system in a microgrid.

The technical solution adopted to solve the technical problem is: a method for calculating the life of a battery energy storage system in a microgrid, which is characterized in that it includes the following content:

1) Analysis of the relationship between the depth of charge and discharge of lithium batteries, the number of cycles and the total throughput

According to the analysis of the corresponding relationship between the depth of charge and discharge of the lithium battery, the number of cycles and the total throughput, the total throughput E _Z (x) of the battery at any depth of charge and discharge is obtained as:

E _Z (x)＝N _Z (x)E _N x (1)

In the formula, x is the charge-discharge cycle depth, which is defined as: assume that the initial state of charge of the battery is SOC ₁ , the state of charge is SOC ₂ after first charging and then discharging, and then the battery is firstly discharged and then recharged to charge the battery The state stops after reaching SOC _1. At this time, the charge-discharge cycle depth is |SOC ₁ -SOC ₂ |, where SOC ₁ → SOC ₂ is recorded as the charge-discharge half cycle; N _Z (x) is the maximum cycle when the charge-discharge depth is x times; E _N is the rated capacity of the battery;

To measure the life of the battery, it is necessary to calculate the total throughput under different charge and discharge depths to the throughput of full charge and discharge. For this reason, a conversion factor is introduced:

α(x) is the conversion factor, E _Z (1) is the total throughput when fully charged and fully discharged, E _Z (X) is the total throughput when the charge and discharge depth is X,

Then, for the i-th charging and discharging depth of x, the throughput is calculated as:

E _i (1)=α(x)E _i (x) (3)

E _i (1) is the throughput when the i-th charge and discharge is converted to full charge and full discharge, and E _i (x) is the throughput at any x charge-discharge depth for the i-th time;

Assuming that the battery is charged and discharged M times in a period, and the charge and discharge depths are x ₁ , Λx _i , Λx _m , the total throughput after calculation is:

E _M (1) The total throughput of the storage battery after reduction, E _i ( _xi ) is the total throughput α( _xi ) of the i-th charge and discharge with x as the depth of charge and discharge,

Establish battery life loss estimation model formula (5) for formula (1) - formula (4):

is the life loss coefficient of the battery energy storage system;

2) Using the fatigue life calculation method in the existing engineering field, that is, the "tower top counting method" to calculate the charging and discharging depth of the battery

① Rotate the coordinate axis 90° clockwise, and the rainflow will flow down the slope from the inside of the peak position of the data;

②Rainflow starts to flow from a certain peak point, and stops flowing when it encounters a peak value greater than its initial peak value, and must stop flowing when it meets the rainflow flowing down from above;

③ Take out all the loops according to the trajectory of the rainflow, and record the amplitude of each loop;

According to the count chart on the top of the tower, the full cycle 2-3-2^, 5-6-5^, the half cycle 1-2-2^-4, 4-5-5^-7, 7-8 are obtained, and the statistics show that the battery is The depth of charge and discharge during the working process, so as to realize the life calculation of the battery energy storage system.

The battery energy storage system life estimation method in a micro-grid of the present invention is scientific and reasonable, and can use the external working characteristics of the battery to establish a life estimation model. The charge-discharge cycle is intercepted to realize the life calculation of the battery energy storage system. It has the advantages of being scientific and reasonable, simple and applicable, and high prediction accuracy.

Description of drawings

Figure 1 is a schematic diagram of the corresponding relationship between the charge and discharge depth of the battery energy storage system, the number of cycles, and the total throughput;

Fig. 2 is a schematic diagram of tower top counting;

Figure 3 is a schematic diagram of calculating the life of the battery energy storage system by the tower top counting method;

Figure 4 is a schematic diagram of the charging and discharging cycle of the battery energy storage system.

detailed description

A method for measuring and calculating the life of a battery energy storage system in a microgrid according to the present invention will be further described below using the drawings and embodiments.

A method for measuring and calculating the life of a battery energy storage system in a microgrid according to the present invention includes the following content:

1) The corresponding relationship between the charge and discharge depth of lithium batteries, the number of cycles and the total throughput

As shown in Figure 1, the corresponding analysis of the depth of charge and discharge of the lithium battery, the number of cycles and the total throughput, the total throughput E _Z (x) of the battery at any depth of charge and discharge is obtained as:

E _Z (x)＝N _Z (x)E _N x (1)

In the formula, x is the charge-discharge cycle depth, which is defined as: assume that the initial state of charge of the battery is SOC ₁ , the state of charge is SOC ₂ after first charging and then discharging, and then the battery is firstly discharged and then recharged to charge the battery The state stops after reaching SOC _1. At this time, the charge-discharge cycle depth is |SOC ₁ -SOC ₂ |, where SOC ₁ → SOC ₂ is recorded as the charge-discharge half cycle; N _Z (x) is the maximum cycle when the charge-discharge depth is x times; E _N is the rated capacity of the battery;

To measure the life of the battery, it is necessary to calculate the total throughput under different charge and discharge depths to the throughput of full charge and discharge. For this reason, a conversion factor is introduced:

α(x) is the conversion factor, E _Z (1) is the total throughput when fully charged and fully discharged, E _Z (X) is the total throughput when the charge and discharge depth is X,

Then, for the i-th charging and discharging depth of x, the throughput is calculated as:

E _i (1)=α(x)E _i (x) (3)

E _i (1) is the throughput when the i-th charge and discharge is converted to full charge and full discharge, and E _i (x) is the throughput at any x charge-discharge depth for the i-th time;

Assuming that the battery is charged and discharged M times in a period, and the charge and discharge depths are x ₁ , Λx _i , Λx _m , the total throughput after calculation is:

E _M (1) The total throughput of the storage battery after reduction, E _i ( _xi ) is the total throughput α( _xi ) of the i-th charge and discharge with x as the depth of charge and discharge,

Establish battery life loss estimation model formula (5) for formula (1) - formula (4):

is the life loss coefficient of the battery energy storage system;

2) Using the fatigue life calculation method in the existing engineering field, that is, the "tower top counting method" to calculate the charging and discharging depth of the battery

① Rotate the coordinate axis 90° clockwise, and the rainflow will flow down the slope from the inside of the peak position of the data;

②Rainflow starts to flow from a certain peak point, and stops flowing when it encounters a peak value greater than its initial peak value, and must stop flowing when it meets the rainflow flowing down from above;

③ Take out all the loops according to the trajectory of the rainflow, and record the amplitude of each loop;

As shown in accompanying drawing 2, obtain full cycle 2-3-2^, 5-6-5^, half cycle 1-2-2^-4,4-5-5^-7,7 according to the tower top count chart -8, get the statistics of the charging and discharging depth of the battery during the working process, so as to realize the life calculation of the battery energy storage system.

As shown in Figure 3, the working cycle of the battery energy storage system is intercepted by the "tower top counting method". The abscissa is the peak point, and the ordinate is the remaining capacity of the energy storage system (the relationship between the output of each power source and the load demand of the energy storage system within a 24-hour energy storage cycle), and there are 160 peak points within 24 hours. It can be seen from Figure 3 that the energy storage system charges when the slope is positive, and discharges when the slope is positive. There are 65 cycle periods and 5 cycle half-cycles. The eighth cycle is shown in the lower right corner of Figure 3. The energy storage system is discharged when the capacity reaches 72.865kWh. After the discharge capacity reaches 70.771kWh, the discharge ends. When the system is charged to 72.865kWh, it is a cycle. The discharge depth curve is shown in Figure 4. Show. It can be seen from the figure that the life estimation method of the battery energy storage system can be calculated by the estimation method in this paper, which shows that this estimation method has a good life estimation ability.

The embodiments of the present invention are only used to further illustrate the present invention, are not exhaustive, and do not constitute a limitation on the protection scope of the claims. Those skilled in the art can think of other inventions without creative work according to the enlightenment obtained by the embodiments of the present invention. Substituents that are substantially equivalent are within the protection scope of the present invention.

Claims (1)

1. A method for calculating the life of a battery energy storage system in a microgrid, characterized in that it includes the following: 1) The corresponding relationship between the charge and discharge depth of lithium batteries, the number of cycles and the total throughput According to the corresponding analysis of the charge and discharge depth of the lithium battery, the number of cycles and the total throughput, the total throughput E _Z (x) of the battery at any charge and discharge depth is obtained as: E _Z (x)＝N _Z (x)E _N x (1) In the formula, x is the charge-discharge cycle depth, which is defined as: assume that the initial state of charge of the battery is SOC ₁ , the state of charge is SOC ₂ after first charging and then discharging, and then the battery is firstly discharged and then recharged to charge the battery The state stops after reaching SOC _1. At this time, the charge-discharge cycle depth is |SOC ₁ -SOC ₂ |, where SOC ₁ → SOC ₂ is recorded as the charge-discharge half cycle; N _Z (x) is the maximum cycle when the charge-discharge depth is x times; E _N is the rated capacity of the battery; To measure the life of the battery, it is necessary to calculate the total throughput under different charge and discharge depths to the throughput of full charge and discharge. For this reason, a conversion factor is introduced: <mrow> <mi>&amp;alpha;</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <msub> <mi>E</mi> <mi>Z</mi> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>E</mi> <mi>Z</mi> </msub> <mrow> <mo>(</mo> <mi>X</mi> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> α(x) is the conversion factor, E _Z (1) is the total throughput when fully charged and fully discharged, E _Z (X) is the total throughput when the charge and discharge depth is X, Then, for the i-th charging and discharging depth of x, the throughput is calculated as: E _i (1)=α(x)E _i (x) (3) E _i (1) is the throughput when the i-th charge and discharge is converted to full charge and full discharge, and E _i (x) is the throughput at any x charge-discharge depth for the i-th time; Assuming that the battery is charged and discharged M times in a period, and the charge and discharge depths are x ₁ , Λx _i , Λx _m , the total throughput after calculation is: <mrow> <msub> <mi>E</mi> <mi>M</mi> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>M</mi> </munderover> <mi>&amp;alpha;</mi> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <msub> <mi>E</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow> E _M (1) The total throughput of the storage battery after reduction, E _i ( _xi ) is the total throughput α( _xi ) of the i-th charge and discharge with x as the depth of charge and discharge, Establish battery life loss estimation model formula (5) for formula (1) - formula (4): <mrow> <msubsup> <mi>B</mi> <mrow> <mi>l</mi> <mi>i</mi> <mi>f</mi> <mi>e</mi> </mrow> <mrow> <mi>l</mi> <mi>o</mi> <mi>s</mi> <mi>s</mi> </mrow> </msubsup> <mo>=</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mfrac> <mrow> <msub> <mi>E</mi> <mi>M</mi> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>E</mi> <mi>Z</mi> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>)</mo> </mrow> <mo>&amp;times;</mo> <mn>100</mn> <mi>%</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow> is the life loss coefficient of the battery energy storage system; 2) Using the fatigue life calculation method in the existing engineering field, that is, the "tower top counting method" to calculate the charging and discharging depth of the battery ① Rotate the coordinate axis 90° clockwise, and the rainflow will flow down the slope from the inside of the peak position of the data; ②Rainflow starts to flow from a certain peak point, and stops flowing when it encounters a peak value greater than its initial peak value, and must stop flowing when it meets the rainflow flowing down from above; ③ Take out all the loops according to the trajectory of the rainflow, and record the amplitude of each loop; According to the count chart on the top of the tower, the full cycle 2-3-2^, 5-6-5^, the half cycle 1-2-2^-4, 4-5-5^-7, 7-8 are obtained, and the statistics show that the battery is The depth of charge and discharge during the working process, so as to realize the life calculation of the battery energy storage system.