CN103887853B - A kind of Li-ion batteries piles balance control method - Google Patents

Abstract

The invention discloses a kind of Li-ion batteries piles balance control method.By the inner parameter of batteries monomer battery and the accurate estimation of SOC value, as the reference quantity of battery pack balancing control algolithm; By the safety problem that Balance route scheme solution battery pack super-charge super-discharge may bring, improve life-span and the performance of battery pack.The present invention can carry out Balance route to the operating state of lithium power battery pack, performance, sets up the active equalization control method based on SOC estimated value, adopts electronic technology and Computer Control Technology to design intelligent lithium power battery pack balance control method.The enforcement of invention achievement is for promoting that the popularization of lithium dynamical battery, the energy storage capability improving lithium power battery pack, utilance and cycle life have important realistic meaning, overcome the shortcoming of lithium power battery pack balance control system simultaneously, promote the application based on the new energy electric motor vehicle technology of lithium dynamical battery and popularization.

Description

A kind of Li-ion batteries piles balance control method

Technical field

The present invention relates to a kind of control method, more specifically, it relates to a kind of Li-ion batteries piles balance control method.

Background technology

New Energy Industry is that national economy is strategic, advanced sector, to spurring economic growth, industry restructuring, promotion industrial repositioning upgrading, breaks through energy bottleneck constraint and has a very important role.Since nineteen nineties, lithium ion battery is as one of the developing direction of New Energy Industry, be subject to the attention of more and more domestic and international researcher, and achieve great progress, China is in " 15 " and the Eleventh Five-Year Plan period development power energy storage lithium ion battery is listed in key research project, nearly 1,000,000,000 yuan of funds intensity.Be devoted to research lithium ion battery at present both at home and abroad as auxiliary power source, strive for obtaining more quantum jump at large-scale applied environments such as space flight, military project, renewable energy system energy storage.

Lithium ion battery has following excellent performance characteristics: voltage is high, specific energy is large, have extended cycle life, security performance is good, self discharge is little, but because Li-ion batteries piles is modularization, so the new problem such as security performance and battery cycle life can be involved in actual applications, if these problems can not get timely solution, it will govern the application of lithium power battery pack in new-energy automobile.

Summary of the invention

The object of the invention is to overcome deficiency of the prior art, provide a kind of rational in infrastructure, control precision is high, the Li-ion batteries piles balance control method that discharge and recharge is effective.

This Li-ion batteries piles balance control method:

Step 1, data processing and monomer SOC calculated value; Calculate the method for residual capacity in conjunction with Ah counting method (Ah method), definition lithium-ion battery monomer SOC calculation expression is as follows:

In formula, Q ₀for cell rated capacity, t ₀for initial samples time point, integration formula represent from initial samples time t ₀to the capability value that any time point t battery is filled with or releases, SOC (t) is real-time cell SOC value, SOC (t ₀) be initial SOC value, h is discharge and recharge coefficient, and I (t) is battery charging and discharging electric current;

Ah method is defined as follows: the remaining capacity value in cell moment is that initial capacity value adds the capability value being filled with or releasing, and uses integration formula represent t ₀to the electricity that t battery is filled with or releases.

Step 1-1, in conjunction with lithium ion battery second-order circuit equivalent model, founding mathematical models equation is:

${\stackrel{\·}{V}}_f=-\frac{1}{R_f{C}_f}{V}_f+\frac{1}{C_f}{I}_B---\left(2\right)$

${\stackrel{\·}{V}}_S=-\frac{1}{R_S{C}_S}{V}_S+\frac{1}{C_S}{I}_B---\left(3\right)$

In formula, R _f, C _frepresent polarization parameter respectively, R _s, C _srepresent concentration difference parameter respectively, V _frepresent polarizing voltage, V _srepresent concentration difference voltage; I _bfor equivalent electric circuit charging and discharging currents;

Step 1-2, obtains internal resistance parameter value accurately by lithium-ion battery tester, draws the dynamic electric voltage calculated value in polarization resistance and concentration difference internal resistance by expression formula (2) and (3);

Step 1-3, the cell voltage obtained by battery parameter test module, electric current and temperature value, obtain cell SOC dynamic calculation expression formula by expression formula (3):

$\stackrel{\·}{V_{SOC}}=-\frac{1}{R_{sd}{C}_b}{V}_{SOC}+\frac{1}{C_b}{I}_B---\left(4\right)$

In formula, V _sOCfor battery equivalent electric circuit total voltage, it represents the functional relation of SOC value of battery; R _sdrepresent the total internal resistance of cell equivalence, C _bfor equivalent total capacitance;

Step 1-4, by expression formula (4), monomer battery voltage/current parameters value that integrating step 1-2 measures, calculates real-time cell SOC value;

Step 2, the real-time SOC value of the cell utilizing step 1 to obtain carries out cell charge and discharge balancing;

Step 2-1, carries out cell sequence according to the SOC value that step 1 obtains, and arranging SOC minimum threshold is 0.4 to judge;

Step 2-2, detects the cell quantity n that SOC value is greater than 0.4, if n≤6, carries out Balance route initialize routine;

Step 2-3, after step 2-2 initialization, calculates SOC value difference between each cell; Cell SOC value is less than 1, and difference is greater than 0.2, opens the corresponding relay of balancing control circuit; If cell SOC value is respectively SOC (Bj), j=1,2 ..., 6;

(1) neighboring unit cell SOC difference is calculated:

ΔSOC(1,2)＝SOC(B1)-SOC(B2)

ΔSOC(2,3)＝SOC(B2)-SOC(B3)

……

(2) utilize Robust filtering device to judge the difference DELTA SOC (k, k+1) calculated, eliminate pseudo error value; If measurement difference is Δ SOC (i), i=1,2 ... 5, the weight coefficient of difference is { P _i, then obtain thresholding computing formula according to least square method:

ΣP _iΔSOC ²(i)＝min

(3) introduce the M estimation criterion in robust computational methods, thresholding computing formula is:

Σρ(ΔSOC(i))＝min

ρ (Δ SOC (i))=P in formula _iΔ SOC ²(i); Make parameter expression wherein ρ ' (Δ SOC (i)) gets the result of calculation that minimum value obtains for thresholding computing formula, then weight factor computing formula is:

(4) recalculate cell SOC value difference weight coefficient, can obtain average weight coefficient is in formula represent i-th difference weight coefficient P _iwith weight factor w _imultiplied value, when meeting, least-squares estimation thresholding formula is as follows, can error in judgement value be effective error:

$\mathrm{\Σ}\stackrel{-}{P}{\mathrm{\ΔSOC}}^2\left(i\right)=min$

(5) pseudo error value is rejected, if the difference number of Δ SOC (i) >=0.2 is greater than 2, namely need the cell of balanced discharge more than 3, then to the sequence that Δ SOC (i) carries out from big to small, first 2 cells that difference is larger carry out balance policy control;

(6) judging needing 2 cells carrying out balance policy control to carry out again SOC value size, if SOC (Bj) is comparatively large, opening corresponding relay switch;

(7) other cell SOC value of Real-Time Monitoring and corresponding Δ SOC (i), circulation is carried out judging until SOC≤0.4, carries out cell electric discharge or charge supplementing, and completes the object of balance charge/discharge;

Step 2-4, judges whether cycle-index i exceedes serial battery maximum, if wait for, if not, continue to calculate cell SOC value and SOC difference, carry out the rate-determining steps of next Balance route switch.

The invention has the beneficial effects as follows: by the inner parameter of batteries monomer battery and the accurate estimation of SOC value, as the reference quantity of battery pack balancing control algolithm; By the safety problem that Balance route scheme solution battery pack super-charge super-discharge may bring, improve life-span and the performance of battery pack.The present invention can carry out Balance route to the operating state of lithium power battery pack, performance, sets up the active equalization control method based on SOC estimated value, adopts electronic technology and Computer Control Technology to design intelligent lithium power battery pack balance control method.The enforcement of invention achievement is for promoting that the popularization of lithium dynamical battery, the energy storage capability improving lithium power battery pack, utilance and cycle life have important realistic meaning, overcome the shortcoming of lithium power battery pack balance control system simultaneously, promote the application based on the new energy electric motor vehicle technology of lithium dynamical battery and popularization.

Accompanying drawing explanation

Fig. 1 is SOC algorithm for estimating flow chart;

Fig. 2 is the balance module circuit theory diagrams based on SOC;

Fig. 3 is master control program flow chart;

Fig. 4 is OCV-SOC discharge and recharge matched curve;

Fig. 5 is the voltage-contrast figure of cell (10) discharge test 6 time points;

Fig. 6 is cell (6) equalizing charge control effects figure.

Embodiment

Below in conjunction with drawings and Examples, the present invention is described further.Although the present invention will be described in conjunction with preferred embodiment, should know, and not represent and limit the invention in described embodiment.On the contrary, the present invention will contain can be included in attached claims limit scope of the present invention in alternative, modified model and equivalent.

Battery pack balancing control program:

Step 1, data processing and monomer SOC calculated value.The present invention calculates the method for residual capacity in conjunction with Ah method, and definition lithium-ion battery monomer SOC calculation expression is as follows:

In formula, SOC (t) is real-time cell SOC value, SOC (t ₀) be initial SOC value, h is discharge and recharge coefficient, and I (t) is battery charging and discharging electric current.

Step 1-1, the present invention is in conjunction with lithium ion battery second-order circuit equivalent model, and founding mathematical models equation is:

${\stackrel{\·}{V}}_f=-\frac{1}{R_f{C}_f}{V}_f+\frac{1}{C_f}{I}_B---\left(2\right)$

${\stackrel{\·}{V}}_S=-\frac{1}{R_S{C}_S}{V}_S+\frac{1}{C_S}{I}_B---\left(3\right)$

In formula, R _f, C _fand R _s, C _srepresent polarization parameter and concentration difference parameter respectively, V _fand V _srepresent polarizing voltage and concentration difference voltage.

Step 1-2, utilizes lithium-ion battery tester to obtain internal resistance parameter value accurately, draws the dynamic electric voltage calculated value in polarization resistance and concentration difference internal resistance by expression formula (2) and (3);

Step 1-3, the outside batteries parametric testing module utilizing the present invention to design is as Fig. 3, and the cell voltage obtained, electric current and temperature value, obtain cell SOC dynamic calculation expression formula by expression formula (3):

$\stackrel{\·}{V_{SOC}}=-\frac{1}{R_{sd}{C}_b}{V}_{SOC}+\frac{1}{C_b}{I}_B---\left(4\right)$

In formula, V _sOCfor battery equivalent electric circuit total voltage, it represents the functional relation of SOC value of battery.

Step 1-4, by expression formula (4), monomer battery voltage/current parameters value that integrating step 1-2 measures, calculates real-time cell SOC value.

Step 2, the real-time SOC value of the cell utilizing step 1 to obtain carries out cell charge and discharge balancing, realizes general flow chart as shown in Figure 1, and equalizing circuit hardware circuit diagram as shown in Figure 2.

Step 2-1, Fig. 1 show, and carry out cell sequence according to the SOC value that step 1 obtains, and arranging SOC minimum threshold is 0.4 to judge.

Step 2-2, detects the cell quantity n that SOC value is greater than 0.4, if n≤6, carries out Balance route initialize routine.

Step 2-3, after step 2-2 initialization, calculates SOC value difference between each cell.Cell SOC value is less than 1 (SOC≤1), and difference is greater than 0.2 (Δ SOC >=0.2), opens the corresponding relay of balancing control circuit, switch S 1-S6 as shown in Figure 2.For equalization discharge, suppose that cell SOC value is respectively SOC (Bj), j=1,2 ..., 6.

(1) neighboring unit cell SOC difference is calculated:

ΔSOC(1,2)＝SOC(B1)-SOC(B2)

ΔSOC(2,3)＝SOC(B2)-SOC(B3)

……

(2) utilize Robust filtering device to judge the difference DELTA SOC (k, k+1) calculated, eliminate pseudo error value.Suppose that measuring difference is Δ SOC (i), i=1,2 ... the weight coefficient of 5 differences is { P _i, then obtain thresholding computing formula according to least square method:

ΣP _iΔSOC ²(i)＝min

(3) introduce the M estimation criterion in robust computational methods, thresholding computing formula is:

Σρ(ΔSOC(i))＝min

Order weight factor computing formula is:

(4) recalculate cell SOC value difference weight coefficient, can obtain when meeting, least-squares estimation thresholding formula is as follows, can error in judgement value be effective error:

$\mathrm{\Σ}\stackrel{-}{P}{\mathrm{\ΔSOC}}^2\left(i\right)=min$

(5) pseudo error value is rejected, if the difference number of Δ SOC (i) >=0.2 is greater than 2, namely need the cell of balanced discharge more than 3, then to the sequence that Δ SOC () carries out from big to small, first 2 cells that difference is larger carry out balance policy control;

(6) judging needing 2 cells carrying out balance policy control to carry out again SOC value size, if SOC (Bj) is comparatively large, opening relay switch Si (i=1,2 ..., 6), open K0 simultaneously, and in succession open K1-K3 according to external voltage and capacity requirement;

(7) other cell SOC value of Real-Time Monitoring and corresponding Δ SOC (), circulation is carried out judging until SOC≤0.4, carries out cell electric discharge or charge supplementing, and completes the object of balance charge/discharge.

Step 2-4, according to Fig. 2 and step 2-3, the monomer SOC value based on filter calculating is the basis of Balance route process, strategy major control three relay switches, cell connecting valve S1-S6, discharge resistance connecting valve K0, export total voltage control switch K1-K4.

Step 2-5, judges whether cycle-index i exceedes serial battery maximum, if wait for, if not, continue to calculate cell SOC value and SOC difference, carry out the rate-determining steps of next Balance route switch.

Be illustrated in figure 1 SOC algorithm for estimating flow chart:

(1) Balance route hardware circuit and control program mainly design according to cell SOC value, and control the start and stop of relevant relay, and workflow is as follows:

(2) battery pack is started working, and waits for cell discharge and recharge Warning Mark, namely judges whether normal work according to cell size of current;

(3) if without Warning Mark, continue to wait for, if the normal charge/discharge operation of battery, utilize battery three parameters to carry out the estimation of cell SOC value, and sort according to the SOC value of each battery;

(4) loop initialization number of times i=0, for judging the open and close number of times of Balance route switch;

(5) judge whether cycle-index i exceedes serial battery maximum, if wait for, if not, continue to calculate the SOC value between cell;

(6) cell SOC value is greater than 1, and difference is greater than 0.2, opens the corresponding relay of balancing control circuit, and carrying out discharges or charge supplements, and completes the object of balance charge/discharge.

Be illustrated in figure 2 Balance route decision-making module and charge and discharge control protection hardware circuit diagram:

This modular circuit comprises relay switch Si, DC/DC voltage inverter, balanced discharge network and power-off protecting circuit.According to the actual characteristic of monomer lithium ion battery, the present invention devises composite balancing control hardware circuit with low cost, to be convenient to industrialization realization.

(1) form: the relay network that equalizing circuit forms primarily of relay switch, discharge resistance network, balanced DC/DC power supply voltage converter are formed.

(2) operation principle: the control signal obtained according to higher level's Balance route decision-making module, controls 10 monomer lithium ion batteries whether in discharge and recharge hardware circuit.

(3) innovative point: based on real-time cell SOC value, premised on discharge based on battery cell SOC value strategy, equalizing resistance control of discharge strategy, output voltage control strategy three control modules, reach the object of 10 monomer lithium ion battery balance charge/discharges, improve battery pack gross power, extending battery life.Resistance R is as balanced discharge resistance, and switch ki control inputs, to the total voltage of DC/DC inverter, is finally supplied to load as general supply.

Be illustrated in figure 3 master control program module scheme, main control module scheme practical function is as follows:

(1) initialization collector, equalizing circuit and main control chip, gathers battery current, voltage and temperature data;

(2) according to the battery cell voltage/current state information gathered, judge battery current state, if battery current is not equal to 0, can judge battery operated at charging and discharging state, carry out the SOC numerical computations based on Ah method of estimation;

(3), under charge/discharge operation state, continue to judge electric current, if be greater than 0, then battery operated in discharge condition, if be less than 0, then battery operated middle charged state;

(4) according to the SOC value of battery of the battery cell information gathered, loop current size and real-time estimation, under batteries charging or discharge condition, determine whether to open Balance route algorithm, thus realize the charging of battery, discharge achieve effective control and management, ensure the use safely and efficiently of battery;

(5) utilize SPI communication module and CAN to carry out host computer to communicate.

Actual battery group balance control method is tested:

Step 1, set up lithium ion battery external parameter computation model, charge-discharge test arranges current value I _b=1500mA (discharge-rate is 1C).

Step 1-1, according to dynamic end voltage tester data, battery charging and discharging capacitance values, utilize experimental data to carry out obtaining second-order equation matching based on the MATLAB curve of least square, Fig. 4 is charging curve comparison diagram and discharge curve comparison diagram.Simulation parameter is calculated as follows, and wherein parameter a represents electric discharge OCV-SOC parametric fitting results, and parameter b represents charging OCV-SOC parametric fitting results, can try to achieve fit equation such as formula shown in (5) and (6).

a＝36.1425-198.4752263.2273

b＝1.0e+003*0.9296-5.57978.3471

Electric discharge: V _oC(SOC)=36.1425-198.472SOC+263.2273SOC ²(5)

Charging: V _oC(SOC)=929.6-5579.7SOC+8347.1SOC ²(6)

SOC=[0-1], OCV are mV unit.

Step 1-2, according to repeatedly charge-discharge test, chooses wherein three secondary data utilize lithium-ion battery tester, obtains the Ohmic resistance R of equivalent-circuit model ₀, polarization parameter R _f, C _fwith concentration difference parameter R _s, C _sbe worth as follows:

(1) first time discharge cycle parameter value:

R ₀＝(3.3779-3.3333)V/0.75A＝0.0446V/0.75A＝0.0595Ω

R _f＝91.23mW，R _s＝84.17mW

(2) second time discharge cycle parameter value:

R ₀＝(3.3537-3.3097)/0.75A＝0.044V/0.75A＝0.0587Ω

R _f＝74.81mW，R _s＝78.52mW

(3) third time discharge cycle parameter value:

R ₀＝(3.3469-3.3026)/0.75A＝0.0443V/0.75A＝0.0590Ω

R _f＝63.85mW，R _s＝70.23mW

(4) charging-discharging cycle mean parameter:

Time constant t _f=[78.50s, 85.23s, 83.16s] t _s=[585.8s, 641.3s, 627.6s]

Concentration polarization internal resistance:

Electric current/concentration polarization resistance product R _fc _f=[68.42536,56.1043,47.8860]

Electric current/electrochemical polarization resistance product R _sc _s=[63.1276,58.8902,52.6750]

Resistance parameter R ₀=59.1m Ω, R _f=76.63mW, R _s=77.64mW

Step 2, cell SOC dynamic estimation value, charge-discharge test arranges current value I _b=3000mA (discharge-rate is 1C).

Step 2-1, according to equivalent circuit theory and expression formula (2) and (3), releasing cell terminal voltage expression formula is:

V _B＝V _OC(SOC)-R ₀I _B-V _f-V _S

Step 2-2, according to real-time cell voltage, electric current and temperature value that cell tester records, integrating step 1 calculates Inside Parameter Value, expression formula (5) and (6), obtains SOC estimated value as table 1:

Table 12C discharge test ohmic internal resistance/voltage/SOC relation data

Step 3, based on the Balance route of SOC value

The real-time SOC value of the cell utilizing step 2-2 to obtain sorts to battery, and arranging SOC minimum threshold is 0.4 to judge, implements the Balance route scheme that the present invention proposes.

Fig. 5 represents the magnitude of voltage of battery pack balancing discharge and recharge cell 6 time points.Setup Experiments electric discharge 10min, leaves standstill 5min, and charging 10min, as a charge and discharge cycles.Get 10 battery samples, at t ₀, t ₁, t ₂, t ₃, t ₄, t ₅6 time points carry out the measurement of battery terminal voltage, obtain drawing a conclusion:

(1) before electric discharge starts, cell initial voltage V (t ₀) there are differences, battery #2 terminal voltage maximum (3.43V), battery #7 voltage minimum (3.35V), difference maximum is 80mV;

(2) discharge starting point voltage V (t ₁+), battery #2 terminal voltage maximum (3.198V), battery #2 terminal voltage minimum (2.988V), difference maximum is 200mV;

(3) discharge mid-life voltage V (t ₂) and electric discharge voltage V (t in latter stage ₃-), cell terminal voltage difference maximum is respectively 100mV and 80mV, and as seen along with the work of balance controller, battery discharge terminal voltage is tending towards identical;

(4) discharge voltage V (t in latter stage ₄) and standing period voltage V (t ₅), maximum difference only has about 5mV-10mV, represents that the accuracy of equalization of the equalizing circuit cell of the present invention's design can reach 5mV-20mV.

Fig. 6 represents in 6 cell equalizing charge control procedures, voltage curve.Abscissa is time (0-500s), and ordinate is cell terminal voltage value.In figure curve and data known, the charging initial stage there is notable difference in 6 monomer battery voltage values; Along with the prolongation in charging interval, balance control system carries out charge balancing control according to the real-time SOC value of cell, reaches the object that cell terminal voltage difference reduces; About when charging 350s, 6 cell terminal voltage differences are minimum; Charging end time section, battery terminal voltage rises instantaneously, occurs voltage differences, and 3 batteries converge on about 4.0V, and 3 batteries converge on about 3.8V.Illustrate that equalizing circuit hardware designs and equalization algorithm have good control effects for the discharge and recharge under lithium ion battery normal operating conditions.

The technical indicator drawn:

(1) electronic load

Power bracket: 10KW current range: 50A, 100A, 200A, 400A, 1000A voltage range: 100V, 200V, 400V

(2) battery capacity and SOC estimation precision

Range of capacity: 1.5Ah ~ 15AhSOC estimated accuracy: 5%

(3) monomer battery voltage protection

Cell under-voltage protection value: 2.75V cell overvoltage protection value: 3.9V or 4.25V

(4) cell overcurrent protection value

3A (can recover)

(5) cell parameter measurement precision

Voltage control precision: 0.5%FS current control accuracy: 0.5%FS

(6) battery pack balancing controls

Battery balanced precision: 5mV-20mV cell euqalizing current: 1.5A (MAX15A)

(7) battery pack temperature controls

Battery pack temperature protection value: 65 DEG C of nominal operation ambient temperatures :-20 DEG C ~ 50 DEG C

Nominal operation envionmental humidity: <80%.

Claims (1)

1. a Li-ion batteries piles balance control method, is characterized in that:

Step 1, data processing and monomer SOC calculated value; Calculate the method for residual capacity in conjunction with Ah counting method (Ah method), definition lithium-ion battery monomer SOC calculation expression is as follows:

In formula, Q ₀for cell rated capacity, t ₀for initial samples time point, integration formula represent from initial samples time t ₀to the capability value that any time point t battery is filled with or releases, SOC (t) is real-time cell SOC value, SOC (t ₀) be initial SOC value, h is discharge and recharge coefficient, and I (t) is battery charging and discharging electric current;

Step 1-1, in conjunction with lithium ion battery second-order circuit equivalent model, founding mathematical models equation is:

${\stackrel{\&CenterDot;}{V}}_f=-\frac{1}{R_f{C}_f}{V}_f+\frac{1}{C_f}{I}_B---\left(2\right)$

${\stackrel{\&CenterDot;}{V}}_S=-\frac{1}{R_S{C}_S}{V}_S+\frac{1}{C_S}{I}_B---\left(3\right)$

In formula, R _f, C _frepresent polarization parameter respectively, R _s, C _srepresent concentration difference parameter respectively, V _frepresent polarizing voltage, V _srepresent concentration difference voltage; I _bfor equivalent electric circuit charging and discharging currents;

Step 1-2, obtains internal resistance parameter value accurately by lithium-ion battery tester, draws the dynamic electric voltage calculated value in polarization resistance and concentration difference internal resistance by expression formula (2) and (3);

Step 1-3, the cell voltage obtained by battery parameter test module, electric current and temperature value, obtain cell SOC dynamic calculation expression formula by expression formula (3):

$\stackrel{\&CenterDot;}{V_{SOC}}=-\frac{1}{R_{sd}{C}_b}{V}_{SOC}+\frac{1}{C_b}{I}_B---\left(4\right)$

In formula, V _sOCfor battery equivalent electric circuit total voltage, it represents the functional relation of SOC value of battery; R _sdrepresent the total internal resistance of cell equivalence, C _bfor equivalent total capacitance;

Step 1-4, by expression formula (4), monomer battery voltage/current parameters value that integrating step 1-2 measures, calculates real-time cell SOC value;

Step 2, the real-time SOC value of the cell utilizing step 1 to obtain carries out cell charge and discharge balancing;

Step 2-1, carries out cell sequence according to the SOC value that step 1 obtains, and arranging SOC minimum threshold is 0.4 to judge;

Step 2-2, detects the cell quantity n that SOC value is greater than 0.4, if n≤6, carries out Balance route initialize routine;

Step 2-3, after step 2-2 initialization, calculates SOC value difference between each cell; Cell SOC value is less than 1, and difference is greater than 0.2, opens the corresponding relay of balancing control circuit; If cell SOC value is respectively SOC (Bj), j=1,2 ..., 6;

(1) neighboring unit cell SOC difference is calculated:

ΔSOC(1,2)＝SOC(B1)-SOC(B2)

ΔSOC(2,3)＝SOC(B2)-SOC(B3)

……

(2) utilize Robust filtering device to judge the difference DELTA SOC (k, k+1) calculated, eliminate pseudo error value; If measurement difference is Δ SOC (i), i=1,2 ... 5, the weight coefficient of difference is { P _i, then obtain thresholding computing formula according to least square method:

ΣP _iΔSOC ²(i)＝min

(3) introduce the M estimation criterion in robust computational methods, thresholding computing formula is:

Σρ(ΔSOC(i))＝min

ρ (Δ SOC (i))=P in formula _iΔ SOC ²(i); Make parameter expression wherein ρ ' (Δ SOC (i)) gets the result of calculation that minimum value obtains for thresholding computing formula, then weight factor computing formula is:

(4) recalculate cell SOC value difference weight coefficient, can obtain average weight coefficient is in formula represent i-th difference weight coefficient P _iwith weight factor w _imultiplied value, when meeting, least-squares estimation thresholding formula is as follows, can error in judgement value be effective error:

$\mathrm{\&Sigma;}\stackrel{\&OverBar;}{P}{\mathrm{\&Delta;SOC}}^2\left(i\right)=min$

(5) pseudo error value is rejected, if the difference number of Δ SOC (i) >=0.2 is greater than 2, namely need the cell of balanced discharge more than 3, then to the sequence that Δ SOC (i) carries out from big to small, first 2 cells that difference is larger carry out balance policy control;

(6) judging needing 2 cells carrying out balance policy control to carry out again SOC value size, if SOC (Bj) is comparatively large, opening corresponding relay switch;

(7) other cell SOC value of Real-Time Monitoring and corresponding Δ SOC (i), circulation is carried out judging until SOC≤0.4, carries out cell electric discharge or charge supplementing, and completes the object of balance charge/discharge;

Step 2-4, judges whether cycle-index i exceedes serial battery maximum, if wait for, if not, continue to calculate cell SOC value and SOC difference, carry out the rate-determining steps of next Balance route switch.