CN105676131A - Vanadium cell dynamic state of charge (SOC<d>)estimation method based on charging/discharging energy efficiency - Google Patents

Abstract

A vanadium cell SOC<d> estimation method based on charging/discharging energy efficiency is characterized in that the cell working is divided into a charging process and a discharging process, and correspondingly, the cell energy is divided into the charging-side energy and the discharging-side energy; the charging-side energy is mapped into the discharging-side energy by the charging/discharging efficiency of a cell under different currents to obtain the static state of charge(SOC<s>) of the cell; the SOC<d> of the cell are estimated under the loads by taking the reference load discharging capacity as the reference energy and according to the SOC<s> and the discharging capacities of the cell under different loads. The method comprises the concrete steps of (1) adopting different currents to charge the cell respectively to obtain the efficiencies of the cell under different currents to thereby obtain the SOC<s> of the cell; (2) adopting different loads to discharge the cell to obtain the function relationships of different load releasable energy relative to a reference load to thereby obtain the SOC<d> of the cell.

Description

A kind of vanadium cell dynamic battery charge state estimation method based on charge-discharge energy efficiency

Technical field

The present invention relates to a kind of all-vanadium flow battery SOC (battery charge state) evaluation method, be mainly used in direct-current grid, battery charged side energy be mapped to discharge side by relationship between efficiency and obtain battery static state SOC_s, using baseline load discharge capacity as reference energy, according to static SOC_sWith the dynamic SOC under this load of the discharge capacity estimation battery of battery under different loads_d。

Background technology

Energy and environment are two hang-ups of world today's facing, and this two hang-up of solution that appears as of micro-capacitance sensor provides new thinking. The low capacity electric power system that micro-capacitance sensor is made up of Distributed-generation equipment, energy storage device, load and relevant control, protection equipment etc. As the important component part of micro-capacitance sensor, energy storage device, for stabilizing power and the energy hunting of micro-grid system, improves stability and the schedulability of system, improves the aspects such as the quality of power supply and play an important role. All-vanadium flow battery with its with environmental friendliness, have extended cycle life, safe and reliable, the advantages such as extensive energy storage can be realized, obtain increasing application.

SOC estimation is one of core content of battery management system research, and the power directly affecting battery controls and energy management. The problem that the research of SOC is required to two aspects of reflection: 1. determine that can battery work on, i.e. static charge electricity condition SOC_sResearch; 2. reflection battery maintains the time of current operating state, i.e. dynamic state-of-charge SOC_dResearch.

All-vanadium flow battery is applied in micro-capacitance sensor, mainly stabilize power and the energy hunting of system, the stability of raising system and schedulability, absorb unnecessary energy and power at system capacity, power time unnecessary, fill up energy and the power shortage of system when system capacity, power disappearance. Therefore, energy storage device is always at charge or discharge state, and its research can also be divided into charging and discharging two parts. Research for discharge portion at present adopts constant-current discharge more; And many employings constant current constant voltage pattern when charging, adopt constant current mode to be charged to certain voltage, then adopt constant current mode to be charged, until electric current drops to certain value. In direct-current grid, time battery operated, operating mode is more complicated, during charging, electric current is moment change, and when discharging, need to connect DC/DC more, and the factor such as the SOH of charge-discharge magnification, temperature, cycle-index, battery also can affect the precision of SOC estimation, the operating condition that the method that therefore present invention proposes is more suitable in micro-capacitance sensor battery.

Summary of the invention:

It is an object of the invention to, according to vanadium cell application conditions in direct-current grid, it is proposed that the method for a kind of applicable all-vanadium flow battery SOC estimation.

The technical scheme is that the dynamic SOC of the vanadium cell based on charge-discharge energy efficiency_dEvaluation method, is divided into charging process and discharge process by battery operated, and the energy content of battery is divided into charged side energy and discharge side energy accordingly; By the efficiency for charge-discharge of battery under different electric currents, charged side energy is mapped as discharge side energy, it is thus achieved that battery static state SOC_s; Using baseline load discharge capacity as reference energy, according to static SOC_sWith the dynamic SOC under this load of the discharge capacity estimation battery of battery under different loads_d, concretely comprise the following steps:

(1) adopt different electric current respectively battery to be charged, it is thus achieved that the efficiency of battery under different electric currents, and then obtain battery static state SOCs;

1) starting vanadium cell, use charger to adopt constant current constant voltage pattern that vanadium cell is charged, until being full of, making vanadium cell keep rotating hot stand-by duty; Stand 10 minutes, then carry out 1C electric discharge with reference load, until it reaches stop electric discharge during electric discharge cut-off condition, obtain battery charge reference energy W_cnWith electric discharge reference energy W_dn。

2) stand 10 minutes, then it is charged with different electric current 0.1-1C 5-8 charging current (such as 30A, 40A, 50A, 60A, 70A, 80A) altogether respectively, when voltage reaches the moment stopping charging that upper limit current starts to reduce, obtain the rechargeable energy W under battery difference electric current_c; Stand 10 minutes, then carry out 1C electric discharge with reference load, until it reaches electric discharge cut-off condition stops electric discharge, obtains the discharge energy W under the different electric currents of battery_d;

3) efficiency of battery under battery difference electric current is tried to achieve by formula (1):

$\mathrm{\&eta;}\left(i\right)=\frac{W_c}{W_d}\&times;100\%---\left(1\right)$

By battery efficiency η (i) matching under different electric currents, obtain the function of battery efficiency under different electric current:

η=f (i (t)) (2)

4) calculate and obtain battery charging power in the unit interval and be:

W_c(t)=u (t) i (t) Δ t (3)

Being mapped to discharge side is:

W_d(t)=f (i (t)) u (t) i (t) Δ t (4)

Integration obtains the energy being mapped to discharge side in a period of time in battery charging process:

$W_d={\&Integral;}_{t_0}^{t}f\left(i\right(t\left)\right)\&CenterDot;u\left(t\right)i\left(t\right)dt---\left(5\right)$

Can be calculated battery static SOCs now is:

${\mathrm{SOC}}_s=\frac{W_d}{W_{dn}}\&times;100\%---\left(6\right)$

(2) adopt different loads that battery is discharged, it is thus achieved that the functional relationship of different loads releasable energy relative reference load, and then obtain the dynamic SOC of battery_d;

1) starting vanadium cell, use charger to adopt constant current constant voltage pattern that vanadium cell is charged, until being full of, making vanadium cell keep rotating hot stand-by duty;

2) stand 10 minutes, then respectively to discharge with 0.1-1C 5-8 discharge current (0.6kW, 1.2kW, 1.8kW, 2.4kW, 3.0kW) altogether under different loads, until stopping electric discharge when reaching electric discharge cut-off condition, it is thus achieved that unequally loaded discharge energy W_dR; Discharge energy under different loads is carried out data fitting, obtains the function expression f (R) of battery discharging energy under different loads;

A) dump energy of battery when obtaining battery with load R electric discharge end can be calculated by through type (7):

W_R=W_dn-f(R)(7)

According to battery static state SOC_sCalculate and obtain the energy that battery current time stores:

W_r=W_dn·SOC_s(8)

It is then possible to adopt the energy that a certain load R discharging time is released when obtaining battery the present situation:

Δ W=W_r-W_R(9)

Dynamic SOC when battery now discharges can be obtained with load R_dFor:

${\mathrm{SOC}}_d=\frac{\mathrm{\&Delta;}W}{W_{dR}}---\left(10\right)$

The method have the benefit that the present invention applies to all-vanadium flow battery SOC estimation method in direct-current grid, be divided into charging process and discharge process by battery operated, accordingly the energy content of battery is divided into charged side energy and discharge side energy.By the efficiency for charge-discharge of battery under different electric currents, charged side energy is mapped as discharge side energy, it is thus achieved that battery static state SOC_s; Using baseline load discharge capacity as reference energy, according to static SOC_sWith the dynamic SOC under this load of the discharge capacity estimation battery of battery under different loads_d。

Accompanying drawing illustrates:

Fig. 1 all-vanadium flow battery test platform;

Fig. 2 static state SOC_sEstimation result;

The dynamic SOC of Fig. 3_dEstimation result.

Detailed description of the invention:

As shown in Figure 1, battery adopts the 3kW/3kWh all-vanadium flow battery with Shenli Science and Technology Co Ltd, Shanghai's R & D Cooperation to all-vanadium flow battery test platform, and its voltage power supply ranges for 39-52V, and discharge cut-off voltage is 39V. Upper computer detection and data collecting system can realize the Real-time Collection of voltage and current, and acquisition precision is 0.1V and 0.1A respectively. DC/DC changer adopts Shanghai Wen Kai power-supply device company limited WYJ-3000W48V changer, output voltage 0-48V. Load is 48V lamp plate, including 60 bulbs that specification is 48V/60W, by switching directly composition in parallel.

1, adopt different electric current respectively battery to be charged, it is thus achieved that the efficiency of battery under different electric currents, and then obtain battery static state SOCs.

1) starting vanadium cell, use charger to adopt constant current constant voltage pattern that vanadium cell is charged, until being full of, making vanadium cell keep rotating hot stand-by duty; Stand 10 minutes, then discharge with reference load 0.6kW, until it reaches stop electric discharge during electric discharge cut-off condition, obtain battery charge reference energy W_cnWith electric discharge reference energy W_dn。

2) stand 10 minutes, be then charged with different electric currents (30A, 40A, 50A, 60A, 70A, 80A) respectively, when voltage reaches the moment stopping charging that upper limit current starts to reduce, obtain the rechargeable energy W under battery difference electric current_c; Stand 10 minutes, then discharge with 0.6kW, until it reaches electric discharge cut-off condition stops electric discharge, obtains the discharge energy W under the different electric currents of battery_d。

3) available formula (1) tries to achieve the efficiency of battery under battery difference electric current:

$\mathrm{\&eta;}\left(i\right)=\frac{W_c}{W_d}\&times;100\%---\left(1\right)$

By battery efficiency η (i) matching under different electric currents, obtain the function of battery efficiency under different electric current:

η=f (i (t)) (2)

4) calculate and obtain battery charging power in the unit interval and be:

W_c(t)=u (t) i (t) Δ t (3)

Being mapped to discharge side is:

W_d(t)=f (i (t)) u (t) i (t) Δ t (4)

Integration can obtain the energy being mapped to discharge side in a period of time in battery charging process:

$W_d={\&Integral;}_{t_0}^{t}f\left(i\right(t\left)\right)\&CenterDot;u\left(t\right)i\left(t\right)dt---\left(5\right)$

Can be calculated battery static SOCs now is:

${\mathrm{SOC}}_s=\frac{W_d}{W_{dn}}\&times;100\%---\left(6\right)$

Fig. 2 is all-vanadium flow battery static state SOC_sEstimation result.

2, adopt different loads that battery is discharged, it is thus achieved that the functional relationship of different loads releasable energy relative reference load, and then obtain the dynamic SOC of battery_d。

A) starting vanadium cell, use charger to adopt constant current constant voltage pattern that vanadium cell is charged, until being full of, making vanadium cell keep rotating hot stand-by duty;

B) stand 10 minutes, then discharge with different loads (0.6kW, 1.2kW, 1.8kW, 2.4kW, 3.0kW) respectively, until it reaches stop electric discharge during electric discharge cut-off condition, it is thus achieved that unequally loaded discharge energy W_dR; Discharge energy under different loads is carried out data fitting, obtains the function expression f (R) of battery discharging energy under different loads;

C) dump energy of battery when obtaining battery with load R electric discharge end can be calculated by through type (7):

W_R=W_dn-f(R)(7)

According to battery static state SOC_sCalculate and obtain the energy that battery current time stores:

W_r=W_dn·SOC_s(8)

It is then possible to adopt the energy that a certain load R discharging time is released when obtaining battery the present situation:

Δ W=W_r-W_R(9)

Dynamic SOC when battery now discharges can be obtained with load R_dFor:

${\mathrm{SOC}}_d=\frac{\mathrm{\&Delta;}W}{W_{dR}}---\left(10\right)$

Accompanying drawing 3 is the dynamic SOC of all-vanadium flow battery_dEstimation result.

Above in conjunction with accompanying drawing, embodiments of the present invention are explained in detail, but the present invention is not limited to above-mentioned embodiment, in the ken that those of ordinary skill in the art possess, it is also possible to make a variety of changes under the premise without departing from present inventive concept.

Claims (1)

1. based on the dynamic SOC of the vanadium cell of charge-discharge energy efficiency_dEvaluation method, is characterized in that being divided into charging process and discharge process by battery operated, the energy content of battery is divided into charged side energy and discharge side energy accordingly; By the efficiency for charge-discharge of battery under different electric currents, charged side energy is mapped as discharge side energy, it is thus achieved that battery static state SOC_s; Using baseline load discharge capacity as reference energy, according to static SOC_sWith the dynamic SOC under this load of the discharge capacity estimation battery of battery under different loads_d, concretely comprise the following steps:

(1) adopt different electric current respectively battery to be charged, it is thus achieved that the efficiency of battery under different electric currents, and then obtain battery static state SOCs;

1) starting vanadium cell, use charger to adopt constant current constant voltage pattern that vanadium cell is charged, until being full of, making vanadium cell keep rotating hot stand-by duty; Stand 10 minutes, then carry out 1C electric discharge with reference load, until it reaches stop electric discharge during electric discharge cut-off condition, obtain battery charge reference energy W_cnWith electric discharge reference energy W_dn。

2) stand 10 minutes, then it is charged with different electric current 0.1-1C 5-8 charging current (30A, 40A, 50A, 60A, 70A, 80A) altogether respectively, when voltage reaches the moment stopping charging that upper limit current starts to reduce, obtain the rechargeable energy W under battery difference electric current_c; Stand 10 minutes, then carry out 1C electric discharge with reference load, until it reaches electric discharge cut-off condition stops electric discharge, obtains the discharge energy W under the different electric currents of battery_d;

3) efficiency of battery under battery difference electric current is tried to achieve by formula (1):

By battery efficiency η (i) matching under different electric currents, obtain the function of battery efficiency under different electric current:

η=f (i (t)) (2)

4) calculate and obtain battery charging power in the unit interval and be:

(3)

W_c(t)=u (t) i (t) Δ t

Being mapped to discharge side is:

(4)

W_d(t)=f (i (t)) u (t) i (t) Δ t

Integration obtains the energy being mapped to discharge side in a period of time in battery charging process:

Can be calculated battery static SOCs now is:

(2) adopt different loads that battery is discharged, it is thus achieved that the functional relationship of different loads releasable energy relative reference load, and then obtain the dynamic SOC of battery_d;

1) starting vanadium cell, use charger to adopt constant current constant voltage pattern that vanadium cell is charged, until being full of, making vanadium cell keep rotating hot stand-by duty;

2) stand 10 minutes, then discharge with different load 0.1-1C 5-8 discharge current (0.6kW, 1.2kW, 1.8kW, 2.4kW, 3.0kW) altogether respectively, until stopping electric discharge when reaching electric discharge cut-off condition, it is thus achieved that unequally loaded discharge energy W_dR; Discharge energy under different loads is carried out data fitting, obtains the function expression f (R) of battery discharging energy under different loads;

3) dump energy of battery when obtaining battery with load R electric discharge end can be calculated by through type (7):

W_R=W_dn-f(R)(7)

According to battery static state SOC_sCalculate and obtain the energy that battery current time stores:

W_r=W_dn·SOC_s(8)

It is then possible to adopt the energy that a certain load R discharging time is released when obtaining battery the present situation:

Δ W=W_r-W_R(9)

Dynamic SOC when battery now discharges can be obtained with load R_dFor:

。