CN103715733A - Triangle connection cascade energy storage system two stage equalization control method - Google Patents

Abstract

The invention provides a triangle connection cascade energy storage system two stage equalization control method. The method comprises the steps that 1, SOC and SOH information of each link of a chained energy storage system is acquired; 2, rechargeable power and dischargeable power of each link are respectively calculated; 3, total rechargeable power and dischargeable power of each line and the whole system are calculated; 4, power distribution and control are carried out on each line; and 5, on the basis that the power of each line is determined, the voltage of each link is distributed according to the proportion of the rechargeable/dischargeable power of each link, and power distribution according to the proportion can be realized. According to the invention, the maximization of the capacity utilization rate of the energy storage system is used as a goal, namely simultaneous complete charging and discharging are carried out on batteries of all links; a safe operation boundary is considered, so that the requirement of the energy storage system for an equalization ability in different operation conditions and SOC states can be reasonably reflected; and an equalization performance is optimized in a range which can be realized.

Description

A kind of triangle connects cascade energy-storage system two-stage balance control method

Technical field

What the present invention relates to is energy-storage system balance control method, and a kind of two-stage SOC equalization methods that is applied to triangle cascade energy-storage system specifically, for high capacity cell energy storage occasion.Belong to battery energy storage field.

Background technology

Cascade energy-storage system is with its modular construction, and under Same Efficieney, the feature that voltage is high, electric current is little, current harmonics is little and efficiency is high, receives publicity day by day.The mutual decoupling zero of control of cascade energy-storage system three lines that triangle connects, its control method is simple compared with the control method of Y-connection, and this topological structure has the two-stage equalization function to battery equally.

The equilibrium of cascade energy-storage system is controlled to research both at home and abroad at present few.2008, Japanese scholars Akagi etc. are at < < A transformerless battery energy storage system based on a multilevel cascade PWM converter[C] .Power Electronics Specialists Conference, IEEE, in 2008:4798-4804 > >, propose the cascade energy storage PCS for battery energy storage, and power control and battery pack SOC balance control method are studied.In literary composition, energy-storage system mutually in balanced control to adopt inject deviation voltage signal, make mutually in the power of each chain link and the deviation of power average be proportional to the SOC of chain link and the deviation of this phase SOC average; Alternate balanced control of energy-storage system adopts injection residual voltage method, makes respectively the upper secondary power producing mutually be proportional to the SOC of each phase and the deviation of three-phase SOC average.Domestic Liu's Wenhuas etc. are controlled [J] at < < large capacity chain type battery energy storage system and charge and discharge balancing thereof. power system automation apparatus, 2011,31 (3): in 6-11 > >, adopted the method for direct control zero-sequence current to realize alternate SOC equilibrium.In above-mentioned equalization methods, controlling target is all that equal power is directly proportional to the deviate of SOC.This take eliminate the simple and easy to understand of control strategy that SOC deviation is direct target, but also have the following disadvantages: the static equilibrium that 1) is applicable to energy-storage system, for the energy-storage system in dynamic operation, this control strategy does not consider that the ability of equalization and integral body discharge and recharge contacting of time.For the energy-storage system in actual motion, ability of equalization reasonable value is not only relevant to the deviation of SOC, also relevant to the absolute value of SOC.2) the SOC secure border while not considering actual motion.In order to guarantee the safe operation of battery, based on SOC estimation error often large (nearly 10%) and battery charging and discharging both end voltage variation reason greatly, the range of operation of restriction SOC in service is no more than 10%-90%.SOC value is apart from SOC upper lower limit value during apart from difference, and its demand to the ability of equalization is different.Currently only consider that the control method of SOC deviation size cannot reflect the difference of controlling in above-mentioned situation.3) do not consider the factor of the capacity volume variance of battery in same energy-storage system.Along with the aging of energy-storage system battery in service and after damaging, change, the SOH of battery is in different states, and the battery of same SOC is but being stored the electric weight of different sizes, is storing the battery of same charge in different SOC states.The simple control of carrying out with SOC and SOC deviation may cause in unidirectional charging or discharge process of energy-storage system, and forward and reverse balanced situation repeatedly appears in the battery that capacity is less, has increased the weight of balanced burden, has reduced efficiency.4) more important point is, the cascade energy-storage system connecting for triangle, and due to " phase " that do not exist physically, residual voltage injection method can not be applicable to the equilibrium of energy-storage system and control.

Summary of the invention

The present invention is directed to the deficiency that prior art exists, propose to be connected cascade energy-storage system two-stage balance control method based on chargeable capacity with triangle that can discharge capacity.The method turns to target with energy storage system capacity utilance maximum, the battery of all chain links is full of electricity simultaneously and is discharged simultaneously, consider safe operation border simultaneously, can more reasonably embody energy-storage system demand to the ability of equalization under different operating conditions and SOC state, optimization equalization performance in attainable scope.

For achieving the above object, the invention provides a kind of triangle and connect cascade energy-storage system two-stage balance control method, described method comprises the steps:

The first step: SOC, the SOH information of obtaining each chain link of chain type energy-storage system

In chain type energy-storage system, each chain link is comprised of battery unit and power cell, battery unit is by battery management system (BMS) management, and power cell is controlled by PCS controller as the part of power conversion system (Power Conversion System, PCS).PCS controller regularly obtains SOC state and the SOH state of the battery unit that each power cell is corresponding from BMS, the time interval is from 0.1s-10min.Obtain manner can be communication modes, can be also analog quantity mode, specifically by the interface between PCS and BMS, is determined.

Second step: calculate each chain link chargeable electric weight and can discharge electricity amount

The rated capacity of the SOC obtaining according to the first step, SOH information and battery unit, calculate respectively each chain link chargeable electric weight and can discharge electricity amount.

Can discharge electricity amount:

Q _f(x,n)--(SOC _x,n-SOC _down)XSOH _x,nxC _N

Chargeable electric weight:

Q _c(x,n)＝(SOC _up-SOC _x,n)XSOH _x,nXC _N

In formula, soc _upand SOC _downrepresent respectively the SOC up-and-down boundary of battery operation, o≤SOC _down<SOC _up≤ 1.Subscript f represents electric discharge, and c represents charging, and x represents one of ab, bc, ca tri-lines, and n represents the chain link numbering in a certain line.C _nfor battery rated capacity.

The 3rd step: calculate the total chargeable electric weight of each line and whole system and can discharge electricity amount

That calculates ab, bc and ca tri-lines can discharge electricity amount:

$Q_{f,\mathrm{ab}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{f(\mathrm{ab},n)}$

$Q_{f,\mathrm{bc}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{f(\mathrm{bc},n)}$

$Q_{f,\mathrm{ca}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{f(\mathrm{ca},n)}$

In formula, subscript f represents electric discharge, and n represents n chain link in this line.N is the chain number of every line.

Calculate three lines total can discharge electricity amount:

Q _f,sum＝Q _f,ab+Q _f,bc+Q _f,ca

Calculate ab, bc and ca tri-lines charge capacity separately:

$Q_{c,\mathrm{ab}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{c(\mathrm{ab},n)}$

$Q_{c,\mathrm{bc}}=\frac{1}{N}\underset{n=1}{\overset{1}{\mathrm{\&Sigma;}}}{Q}_{c(\mathrm{bc},n)}$

$Q_{c,\mathrm{ca}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{c(\mathrm{ca},n)}$

In formula, subscript c represents charging, and n represents n chain link in this line.N is the chain number of every line.

Calculate ab, bc and the total chargeable electric weight of ca tri-lines:

Q _c,sum＝Q _c,ab+Q _c,bc+Q _c,ca

The 4th step: the distribution of each linear heat generation rate and control

According to the ratio of the put/charge capacity of each line, according to gross power instruction Psum, distribute power as follows:

During electric discharge, the discharge power instruction of ab, bc and ca tri-lines is respectively:

$P_{\mathrm{ab}}=\frac{Q_{f,\mathrm{ab}}}{Q_{f,\mathrm{ab}}+Q_{f,\mathrm{bc}}+Q_{f,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{bc}}=\frac{Q_{f,\mathrm{bc}}}{Q_{f,\mathrm{ab}}+Q_{f,\mathrm{bc}}+Q_{f,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{ca}}=\frac{Q_{f,\mathrm{ca}}}{Q_{f,\mathrm{ab}}+Q_{f,\mathrm{bc}}+Q_{f,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

During charging, the charge power instruction of ab, bc and ca tri-lines is respectively:

$P_{\mathrm{ab}}=\frac{Q_{c,\mathrm{ab}}}{Q_{c,\mathrm{ab}}+Q_{c,\mathrm{bc}}+Q_{c,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{bc}}=\frac{Q_{c,\mathrm{bc}}}{Q_{c,\mathrm{ab}}+Q_{c,\mathrm{bc}}+Q_{c,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{ca}}=\frac{Q_{c,\mathrm{ca}}}{Q_{c,\mathrm{ab}}+Q_{c,\mathrm{bc}}+Q_{c,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

Ab, bc and ca tri-line current sizes:

$\left|I_{\mathrm{ab}}\right|=\frac{P_{\mathrm{ab}}}{U_{\mathrm{sab}}}$

$\left|I_{\mathrm{bc}}\right|=\frac{P_{\mathrm{bc}}}{U_{\mathrm{sbc}}}$

$\left|I_{\mathrm{ca}}\right|=\frac{P_{\mathrm{ca}}}{U_{\mathrm{sca}}}$

Ab, bc are identical with three line voltage-phases separately with ca tri-line current phase places.

Control three line current differences and can realize the power proportions between three lines, realize the equilibrium between three lines.

The terminal voltage Uab of three lines, Ubc and Uca are respectively:

${\stackrel{\&CenterDot;}{U}}_{\mathrm{ab}}={\stackrel{\&CenterDot;}{U}}_{\mathrm{sab}}+{\stackrel{\&CenterDot;}{U}}_{\mathrm{Lab}}$

${\stackrel{\&CenterDot;}{U}}_{\mathrm{bc}}={\stackrel{\&CenterDot;}{U}}_{\mathrm{sbc}}+{\stackrel{\&CenterDot;}{U}}_{\mathrm{Lbc}}$

${\stackrel{\&CenterDot;}{U}}_{\mathrm{ca}}={\stackrel{\&CenterDot;}{U}}_{\mathrm{sca}}+{\stackrel{\&CenterDot;}{U}}_{\mathrm{Lca}}$

The 5th step: the distribution of chain link power and control

On the definite basis of each linear heat generation rate, according to each chain link can charge/discharge electric weight the voltage of each chain link of pro rate, can realize power division proportionally.

During charging, ab, bc and ca tri-linear chain economize on electricitys are pressed according to Q _{c (ab, n)}, Q _{c (bc, n)}, Q _{c (ca, n)}pro rate is as follows:

$U_{\mathrm{ab},n}=\frac{Q_{c(\mathrm{ab},n)}}{N\&times;Q_{c,\mathrm{ab}}}\&times;U_{\mathrm{ab}}$

$U_{\mathrm{bc},n}=\frac{Q_{c(\mathrm{bc},n)}}{N\&times;Q_{c,\mathrm{bc}}}\&times;U_{\mathrm{bc}}$

$U_{\mathrm{ca},n}=\frac{Q_{c(\mathrm{ca},n)}}{N\&times;Q_{c,\mathrm{ca}}}\&times;U_{\mathrm{ca}}$

During electric discharge, ab, bc and ca tri-linear chain economize on electricitys are pressed according to Q _{f (ab, n)}, Q _{f (bc, n)}, Q _{f (ca, n)}pro rate is as follows:

$U_{\mathrm{ab},n}=\frac{Q_{f(\mathrm{ab},n)}}{N\&times;Q_{f,\mathrm{ab}}}\&times;U_{\mathrm{ab}}$

$U_{\mathrm{bc},n}=\frac{Q_{f(c,n)}}{N\&times;Q_{f,\mathrm{bc}}}\&times;U_{\mathrm{bc}}$

$U_{\mathrm{ca},n}=\frac{Q_{f(\mathrm{ca},n)}}{N\&times;Q_{f,\mathrm{ca}}}\&times;U_{\mathrm{ca}}$

In formula, U _{ab, n}, U _{bc, n}, U _{ca, n}the AC voltage that represents respectively n chain link of ab, bc, ca tri-lines.Subscript ab, bc, ca represent ab, bc and ca tri-lines, and n represents the numbering of chain link in this line, and N represents the chain number of every line.

The voltage of controlling each chain link controlled the power proportions of each chain link, realized the equilibrium of chain internode.

Compare with existing method for balancing powers, the invention has the beneficial effects as follows:

The present invention has considered the SOC border of battery operation, is beneficial to the protection to battery; Consider the SOH of battery, embodied the impact of cell degradation, balanced control is more reasonable.Balanced control be take all batteries and is full of simultaneously, discharges simultaneously as target, and target is distincter, reasonable.The power control ability that can bring into play to greatest extent PCS, improves balanced effect.Finally reach the object that improves battery capacity utilance and extending battery life.

Accompanying drawing explanation

By reading the detailed description of non-limiting example being done with reference to the following drawings, it is more obvious that other features, objects and advantages of the present invention will become:

Fig. 1 is that the triangle of one embodiment of the invention connects cascade energy-storage system structured flowchart.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.Following examples will contribute to those skilled in the art further to understand the present invention, but not limit in any form the present invention.It should be pointed out that to those skilled in the art, without departing from the inventive concept of the premise, can also make some distortion and improvement.These all belong to protection scope of the present invention.

Embodiment

The present embodiment is 2MW battery energy storage system, rated voltage 10kV, and triangle connects, and every line N=20 chain link connects reactance 20mH.

In the present embodiment, in the operation of battery SOC, be limited to 0.9, under operation, be limited to 0.1.The SOH of battery is 0.9, rated capacity 400Ah.

In the present embodiment, will be by the monomer series-connected rated voltage 960V that forms of 300 joint 3.2V/400Ah ferric phosphate lithium cell, the batteries of rated capacity 400Ah.

The process of the present embodiment is as follows:

The first step: SOC, the SOH information of obtaining each chain link of chain type energy-storage system

PCS obtains the three lines SOC information of totally 60 chain links by the every 3s of communication modes from BMS, and the SOH of chain batteries is 0.9, SOC operation bound and is respectively 0.9 and 0.1, and rated capacity is 400AH.Three line SOC information are as follows: SOC _ab=[0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31,0.31]

SOC _bc=[0.26,0.3,0.32,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3]

SOC _ca=[0.3,0.28,0.3,0.36,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3]

Second step: calculate each chain link chargeable electric weight and can discharge electricity amount

The rated capacity of the SOC obtaining according to step 1, SOH information and battery unit, calculate respectively each chain link chargeable electric weight and can discharge electricity amount.

Calculating each chain link of three lines can discharge electricity amount:

Q _f,ab=[75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6,75.6]AH

Q _f,bc=[57.6,72,79.2,72,72,72,72,72,72,72,72,72,72,72,72,72,72,72,72,72]AH

Q _f,ca=[72,64.8,72,93.6,72,72,72,72,72,72,72,72,72,72,72,72,72,72,72,72]AH

Calculate the chargeable electric weight of each chain link of three lines:

Q _c,ab=[212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4,212.4]AH

Q _c,bc=[230.4,216,208.8,216,216,216,216,216,216,216,216,216,216,216,216,216,216,216,216,216]AH

Q _c,ca=[216,223.2,216,194.4,216,216,216,216,216,216,216,216,216,216,216,216,216,216,216,216]AH

The 3rd step: calculate the total chargeable electric weight of three lines and whole system and can discharge electricity amount

Calculate the chargeable electric weight of every line:

Q _c,ab=212.4AH

Q _c,bc=216.36AH

Q _c,ca=215.28AH

Calculate total chargeable electric weight:

Q _c=212.4AH+216.36AH+215.28AH=644.04AH

That calculates every line can discharge electricity amount:

Q _f,ab=75.6AH

Q _f,bc=71.64AH

Q _f,ca=72.72AH

Calculate total can discharge electricity amount:

Q _f=75.6AH+71.64AH+72.72AH=219.96AH

The 4th step: the distribution of each linear heat generation rate and control

When the power instruction that PCS receives is 900kW charging, three line current phase places are identical with three line voltages.According to the chargeable electric weight of three lines, distribute power as follows:

Pab=212.4/644.04*900kW=296.8kW

Pbc=216.36/644.04*900kW=302.4kW

Pca=215.28/644.04*900kW=300.8kW

Three line current sizes:

Iab=29.68A

Ibc=30.24A

Ica=30.08A

Ab, bc and the pressure drop of tri-grid-connected reactance power frequencies of ca are respectively 186.4V, 189.9V and 188.9V, the phase place corresponding line voltage 90 degree electrical degrees that lag behind.

Tri-end output voltages of Uab, Ubc and Uca are respectively:

Uab=Usab+U _Lab=10000V-j186.4V=10001.74∠-1.07

Ubc=Usbc+U _Lac=10000V-j189.9V=10001.8∠-1.09

Uca=Usca+U _Laa=10000V-j188.9V=10001.78∠-1.08

Wherein angle is with respect to corresponding line voltage phase angle.

When the power instruction that PCS receives is 600kW electric discharge, three line current phase places are contrary with three line voltages.According to the chargeable electric weight of three lines, distribute power as follows:

Pab=75.6/219.96*600kW=206.2kW

Pbc=71.64/219.96*600kW=195.4kW

Pca=72.72/219.96*600kW=198.4kW

Three line current sizes:

Iab=20.62A

Ibc=19.54A

Ica=19.84A

Ab, bc and the pressure drop of tri-grid-connected reactance power frequencies of ca are respectively 129.5V, 122.7V and 124.6V.The leading corresponding line voltage 90 degree electrical degrees of phase place.

Tri-end output voltages of Uab, Ubc and Uca are respectively:

Uab=Usab+U _Lab=10000V+j129.5V=10000.8∠0.74

Ubc=Usbc+U _Lac=10000V+j122.7V=10000.75∠0.70

Uca=Usca+U _Laa=10000V+j124.6V=10000.78∠0.71

Wherein angle is with respect to corresponding line voltage phase angle.

The 5th step: the distribution of chain link power and control

The power that distributes each chain link on the definite basis of each linear heat generation rate, according to each chain link can charge/discharge electric weight Q _{c (a, n)}/ Q _{f (a, n)}, Q _{c (b, n)}/ Q _{f (b, n)}, Q _{c (c, n)}/ Q _{f (c, n)}ratio, distribute power as follows:

Each chain link charge power when PCS gross power is 900kW charging:

P _c,ab=[14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84,14.84]kW

P _c,bc=[16.10,15.09,14.59,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09]kW

P _c,ca=[15.09,15.59,15.09,13.58,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09,15.09]kW

Each chain link voltage:

U _c,ab=[500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09,500.09]V

U _c,bc=[532.45,499.17,482.53,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17,499.17]V

U _c,ca=[501.67,518.39,501.67,451.51,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67,501.67]V

Each chain link discharge power when PCS gross power is 600kW electric discharge:

P _f,ab=[10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.31,10.3110.31,10.31,10.31,10.31,10.31,10.31]kW

P _f,bc=[7.86,9.82,10.80,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82]kW

P _f,ca=[9.82,8.84,9.82,12.77,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82,9.82]kW

Each chain link voltage:

U _f,ab=[500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04,500.04]V

U _f,bc=[402.01,502.51,552.76,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51,502.51]V

U _f,ca=[495.05,445.54,495.05,643.56,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05,495.05]V

The voltage of controlling each chain link controlled the power that discharges and recharges of each chain link.

Above specific embodiments of the invention are described.It will be appreciated that, the present invention is not limited to above-mentioned specific implementations, and those skilled in the art can make various distortion or modification within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (3)

1. triangle connects a cascade energy-storage system two-stage balance control method, it is characterized in that, described method comprises the steps:

The first step: SOC, the SOH information of obtaining each chain link of chain type energy-storage system;

Second step: the rated capacity of the SOC obtaining according to the first step, SOH information and battery unit, calculate respectively each chain link chargeable electric weight and can discharge electricity amount; Wherein:

Can by following formula, obtain by discharge electricity amount:

Q _t(x,n)＝(SOC _x,n-SOC _down)XSOH _x,nxC _N

Chargeable electric weight obtains by following formula:

Q _c(x,n)＝(SOC _up-SOC _x,n)XSOH _x,nXC _N

In formula, soc _upand SOC _downrepresent respectively the SOC up-and-down boundary of battery operation, o≤SOC _down<SOC _up≤ 1, subscript f represents electric discharge, and c represents charging, and x represents one of ab, bc, ca tri-lines, and n represents the chain link numbering in a certain line, C _nfor battery rated capacity;

The 3rd step: the chargeable electric weight of each chain link obtaining according to second step and can discharge electricity amount, calculates the total chargeable electric weight of each line and whole system and can discharge electricity amount;

Calculate ab, bc and ca tri-lines separately can discharge electricity amount:

$Q_{f,\mathrm{ab}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{f(\mathrm{ab},n)}$

$Q_{f,\mathrm{bc}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{f(\mathrm{bc},n)}$

$Q_{f,\mathrm{ca}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{f(\mathrm{ca},n)}$

In formula, subscript f represents electric discharge, and n represents n chain link in this line, the chain number that N is every line;

Calculate three lines total can discharge electricity amount:

Q _f,sum＝Q _f,ab+Q _f,be+Q _f,ca

Calculate ab, bc and ca tri-lines charge capacity separately:

$Q_{c,\mathrm{ab}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{c(\mathrm{ab},n)}$

$Q_{c,\mathrm{bc}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{c(\mathrm{bc},n)}$

$Q_{c,\mathrm{ca}}=\frac{1}{N}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{c(\mathrm{ca},n)}$

In formula, subscript c represents charging, and n represents n chain link in this line, the chain number that N is every line; Calculate ab, bc and the total chargeable electric weight of ca tri-lines:

Q _c,sum=Q _c,ab+Q _c,bc+Q _c,ca；

The 4th step: the result obtaining according to above-mentioned steps, carry out distribution and control that each line discharges and recharges power: according to the ratio of the put/charge capacity of each line, according to gross power instruction P _sum, distribute power as follows: during electric discharge, the discharge power instruction of ab, bc and ca tri-lines is respectively:

$P_{\mathrm{ab}}=\frac{Q_{f,\mathrm{ab}}}{Q_{f,\mathrm{ab}}+Q_{f,\mathrm{bc}}+Q_{f,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{bc}}=\frac{Q_{f,\mathrm{bc}}}{Q_{f,\mathrm{ab}}+Q_{f,\mathrm{bc}}+Q_{f,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{ca}}=\frac{Q_{f,\mathrm{ca}}}{Q_{f,\mathrm{ab}}+Q_{f,\mathrm{bc}}+Q_{f,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

During charging, the charge power instruction of ab, bc and ca tri-lines is respectively:

$P_{\mathrm{ab}}=\frac{Q_{c,\mathrm{ab}}}{Q_{c,\mathrm{ab}}+Q_{c,\mathrm{bc}}+Q_{c,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{bc}}=\frac{Q_{c,\mathrm{bc}}}{Q_{c,\mathrm{ab}}+Q_{c,\mathrm{bc}}+Q_{c,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

$P_{\mathrm{ca}}=\frac{Q_{c,\mathrm{ca}}}{Q_{c,\mathrm{ab}}+Q_{c,\mathrm{bc}}+Q_{c,\mathrm{ca}}}\&times;P_{\mathrm{sum}}$

Ab, bc and ca tri-line current sizes:

$\left|I_{\mathrm{ab}}\right|=\frac{P_{\mathrm{ab}}}{U_{\mathrm{sab}}}$

$\left|I_{\mathrm{bc}}\right|=\frac{P_{\mathrm{bc}}}{U_{\mathrm{sbc}}}$

$\left|I_{\mathrm{ca}}\right|=\frac{P_{\mathrm{ca}}}{U_{\mathrm{sca}}}$

Ab, bc are identical with three line voltage-phases separately with ca tri-line current phase places;

Control three line current differences and can realize the power proportions between three lines, realize the equilibrium between three lines;

The terminal voltage of three lines

with

be respectively:

${\stackrel{\&CenterDot;}{U}}_{\mathrm{ab}}={\stackrel{\&CenterDot;}{U}}_{\mathrm{sab}}+{\stackrel{\&CenterDot;}{U}}_{\mathrm{Lab}}$

${\stackrel{\&CenterDot;}{U}}_{\mathrm{bc}}={\stackrel{\&CenterDot;}{U}}_{\mathrm{sbc}}+{\stackrel{\&CenterDot;}{U}}_{\mathrm{Lbc}}$

${\stackrel{\&CenterDot;}{U}}_{\mathrm{ca}}={\stackrel{\&CenterDot;}{U}}_{\mathrm{sca}}+{\stackrel{\&CenterDot;}{U}}_{\mathrm{Lca}};$

The 5th step: the distribution of chain link power and control

On the definite basis of each linear heat generation rate, according to each chain link can charge/discharge electric weight the voltage of each chain link of pro rate, realize power division proportionally.

2. triangle according to claim 1 connects cascade energy-storage system two-stage balance control method, it is characterized in that, in the described first step: in chain type energy-storage system, each chain link is comprised of battery unit and power cell, battery unit is managed by battery management system, power cell is controlled by power conversion system controller as a part for power conversion system, power conversion system controller regularly obtains SOC state and the SOH state of the battery unit that each power cell is corresponding from battery management system, the time interval is from 0.1s-10min.

3. triangle according to claim 1 connects cascade energy-storage system two-stage balance control method, it is characterized in that, in described the 5th step, is specially:

During charging, ab, bc and ca tri-linear chain economize on electricitys are pressed according to Q _{c (ab, n)}, Q _{c (bc, n)}, Q _{c (ca, n)}pro rate is as follows:

$U_{\mathrm{ab},n}=\frac{Q_{c(\mathrm{ab},n)}}{N\&times;Q_{c,\mathrm{ab}}}\&times;U_{\mathrm{ab}}$

$U_{\mathrm{bc},n}=\frac{Q_{c(\mathrm{bc},n)}}{N\&times;Q_{c,\mathrm{bc}}}\&times;U_{\mathrm{bc}}$

$U_{\mathrm{ca},n}=\frac{Q_{c(\mathrm{ca},n)}}{N\&times;Q_{c,\mathrm{ca}}}\&times;U_{\mathrm{ca}}$

During electric discharge, ab, bc and ca tri-linear chain economize on electricitys are pressed according to Q _{f (ab, n)}, Q _{f (bc, n)}, Q _{f (ca, n)}pro rate is as follows:

$U_{\mathrm{ab},n}=\frac{Q_{f(\mathrm{ab},n)}}{N\&times;Q_{f,\mathrm{ab}}}\&times;U_{\mathrm{ab}}$

$U_{\mathrm{bc},n}=\frac{Q_{f(c,n)}}{N\&times;Q_{f,\mathrm{bc}}}\&times;U_{\mathrm{bc}}$

$U_{\mathrm{ca},n}=\frac{Q_{f(\mathrm{ca},n)}}{N\&times;Q_{f,\mathrm{ca}}}\&times;U_{\mathrm{ca}}$

In formula, U _{ab, n}, U _{bc, n}, U _{ca, n}the AC voltage that represents respectively n chain link of ab, bc, ca tri-lines; Subscript ab, bc, ca represent ab, bc and ca tri-lines, and n represents the numbering of chain link in this line, and N represents the chain number of every line;

The voltage of controlling each chain link controlled the power proportions of each chain link, realized the equilibrium of chain internode.