CN101894208A - Pulse duty ratio calculation method for series power storage battery equalizing circuit switch device - Google Patents

Abstract

The invention discloses a pulse duty ratio calculation method for a series power storage battery equalizing circuit switch device, aiming at solving the problem of the pulse duty ratio calculation of the equalizing circuit switch device according to the relationship established by a lithium ion battery charging state dynamic model between the terminal voltage and the state of charge of the battery so that the state of charge of a single battery tend to be consistent. The duty ratio calculation method comprises the following steps of: fitting a corresponding conic curve according to the relationship between the open circuit voltage and the state of charge (SOC) of the battery; obtaining a relation expression of the terminal voltage and the open circuit voltage of the battery in the charging process according to the storage battery charging state dynamic model; and obtaining an SOC valve (Spn) of each battery during the parameter detection by combining the equalizing charging circuit, calculating the pulse-width modulation (PWM) duty ratio of the equalizing module according to the Spn and equalizing the SOC to ensure that the SOC of the single battery tend to be consistent. The pulse duty ratio calculation method has the advantages of definite steps, simple model, high calculation efficiency and higher theory innovation and application value.

Description

The pulse duty ratio calculation method of series power storage battery equalizing circuit switch device

Technical field

The present invention relates to series power storage battery charge balancing control technology field, relate in particular to the computing method of switching device pulse duty factor in the equalizing circuit, realize each cell state-of-charge equilibrium in charging process.

Background technology

The calculating of the pulse duty factor of cascaded lithium ion power accumulator switching device generally is that the pass with SOC and open-circuit voltage is a prerequisite, and the equilibrium control stage in the batteries charging process calculates.The battery open circuit voltage method is mainly adopted in the measurement of open-circuit voltage.If only utilize this mode to estimate battery SOC, meeting is error to some extent.In order to shorten the time of wait, utilize the regression curve mode, revise open-circuit voltage values with short time acquisition, and then the capacity of decision battery.Yet the open-circuit voltage method is to measure the voltage of battery under no-load condition, is mainly used in the initial capacitance of estimating battery, and battery status accurately can't be provided in battery charge and discharge process.Battery remaining power is exported input current size and Temperature Influence, and the open-circuit voltage method can't be revised these factors, and other method is used so method must be arranged in pairs or groups, can't individualism.Simultaneously, in the equilibrium control in the batteries charging process, the parameter detecting stage is mainly measured charge power supply electric current and each cell terminal voltage value.During test side voltage,, stop each balance module work for obtaining terminal voltage value accurately, and at parameter detecting time-delay T _PLatter stage measure the best because this moment, the inside battery electrochemical reaction tended to be steady, terminal voltage is stable.

Summary of the invention

The objective of the invention is at the deficiencies in the prior art, a kind of pulse duty ratio calculation method of series power storage battery equalizing circuit switch device is provided.

The objective of the invention is to be achieved through the following technical solutions: a kind of pulse duty ratio calculation method that is used for series power storage battery equalizing circuit switch device, this method simulates the relational expression of the quadratic polynomial of SOC and open-circuit voltage according to the relation of lithium ion battery open-circuit voltage and SOC.According to battery charge attitude dynamic model, release battery terminal voltage and open-circuit voltage relation in the charging process, then again by the SOC value S of each battery during parameter detecting _PnCalculate balance module PWM dutycycle, reach the purpose that each cell state-of-charge reaches unanimity in charging process.

The invention has the beneficial effects as follows:

1. concern between terminal voltage of setting up according to charge in batteries attitude dynamic model and the battery charge state, solved equalizing circuit switch device pulse duty factor computational problem

2. effectively regulate equalizing circuit switch device pwm pulse dutycycle, each cell state-of-charge is reached unanimity.

Description of drawings

Fig. 1 is that open-circuit voltage and SOC concern synoptic diagram;

Fig. 2 is the Charging state dynamic model;

Fig. 3 is balanced control flow chart.

Embodiment

The pulse duty ratio calculation method of a kind of series power storage battery equalizing circuit switch device provided by the invention, be under above-mentioned background, in the equilibrium control stage in the batteries charging process, the terminal voltage value substitution formula (6) that records is obtained the SOC value S of each battery during parameter detecting _Pn, pass through S then _PnCalculate the dutycycle of balance module PWM.

Describe the present invention below with reference to the accompanying drawings in detail, it is more obvious that purpose of the present invention and effect will become.

Core of the present invention is: according to the relation between charge in batteries attitude dynamic model and terminal voltage and the battery charge state, calculate equalizing circuit switch device pwm pulse dutycycle, realize that battery SOC in charging process reaches unanimity.The object of the invention cooperates my another invention---power storage battery energy non-dissipative type equalization charging circuit, makes corresponding balanced control strategy.The pulse duty ratio calculation method that the present invention is used for series power storage battery equalizing circuit switch device may further comprise the steps:

When 1, switch turn-offed, the electric current on the switching tube reduced to zero immediately, then I _AvnUndertaken by computing formula (1):

$I_{\mathrm{avn}}=\frac{1}{T}{\∫}_0^{D_{n}T}\frac{V_B}{L}\mathrm{tdt}=\frac{V_B{D}_n^{2}T}{2L}---\left(1\right)$

I wherein _AvnFor flowing into the average current of balance module, D in the one-period _nBe duty cycle of switching, T is a switch periods, V _BBe battery terminal voltage.In like manner, the average current I of one-period internal inductance release _LdnCalculating by formula (2) carry out:

$\left\{\begin{array}{c}{I}_{\mathrm{Ldn}}=\frac{V_B{D}_n^{2}T}{2L(2N-n)},1\≤n\≤N\\ I_{\mathrm{Ldn}}=\frac{V_B{D}_n^{2}T}{2L(n-1)},N+1\≤n\≤2N\end{array}\right.---\left(2\right)$

2, at the equalizing circuit duration of work, the electric current that flows into accumulator except the charging current of charge power supply, the loopback electric current of the balance module of respectively working in addition, average current I _BnCalculating by formula (3) carry out:

$\left\{\begin{array}{c}{I}_{\mathrm{bn}}=I_c+\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}}+\underset{i=N+1}{\overset{2N}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}},1\≤n\≤N\\ I_{\mathrm{bn}}=I_c+\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}}+\underset{i=n+1}{\overset{2N}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}},N+1\≤n\≤N\end{array}\right.---\left(3\right)$

3, according to the relation of lithium ion battery open-circuit voltage and SOC, as shown in Figure 1, SOC during 20%-100%, with the relation of open-circuit voltage can be by the effective match of quadratic polynomial:

S＝-3.712V ²+31.149V-64.363(4)

Consider in the battery charge dynamic process, be subjected to the influence of battery charge equivalent internal resistance and terminal resistance, battery terminal voltage that records and open-circuit voltage can be variant, so adopt battery charge attitude dynamic model (see figure 2), obtain battery terminal voltage and open-circuit voltage relation in the charging process:

V ₀＝V _b-I _CR (5)

R=R wherein _C+ R _b, be the total internal resistance of battery charge attitude.Convolution (4) obtains with (5):

S＝-3.712(V _b-I _CR) ²+31.149(V _b-I _CR)-64.363(6)

4,,, make the SOC of each cell reach the equalization target value S of the average SOC of total battery for keeping each battery capacity balance at SOC between equalizing stage _t:

$S_t=\frac{I_C{T}_S}{Q_t}+\frac{1}{2N}\underset{n=1}{\overset{2N}{\mathrm{\Σ}}}{S}_{\mathrm{pn}}---\left(7\right)$

In fact, at the SOC balance stage, because the influence of the equalizing circuit that is subjected to respectively to work, flowing into the quantity of electric charge of a certain cell, each is variant, and its actual battery capacity is:

Q _Sn＝Q _pn+(I _bn-I _sn)T _S(8)

Q wherein _PnBe the battery capacity in parameter detecting stage, both sides are together divided by battery rated capacity Q _tGet actual accordingly SOC:

$S_{\mathrm{Sn}}=S_{\mathrm{pn}}+\frac{(I_{\mathrm{bn}}-I_{\mathrm{sn}})T_S}{Q_t}---\left(9\right)$

S wherein _PnEach balance module of working is the SOC value during the parameter detecting, so at the SOC balance stage, should make the actual SOC of each cell reach the balance state-of-charge S of target _t, that is:

S _t＝S _Sn (10)

With (1), (2), (3) formula substitution formula (10), can get equalizing circuit switching tube PWM dutycycle:

$D_n=\left\{\begin{array}{cc}[\frac{2L{Q}_t(S_{\mathrm{pn}}-\frac{1}{2N}\underset{i=1}{\overset{2N}{\mathrm{\Σ}}}{S}_{\mathrm{pi}})}{V_B{\mathrm{TT}}_S}+\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}\frac{D_i^2}{2N-i}+\underset{i=N+1}{\overset{2N}{\mathrm{\Σ}}}\frac{D_i^2}{i-1}{]}^{\frac{1}{2}},& 1\≤n\≤N\\ [\frac{2L{Q}_t(S_{\mathrm{pn}}-\frac{1}{2N}\underset{i=1}{\overset{2N}{\mathrm{\Σ}}}{S}_{\mathrm{pi}})}{V_B{\mathrm{TT}}_S}+\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{D_i^2}{2N-i}+\underset{i=n+1}{\overset{2N}{\mathrm{\Σ}}}\frac{D_i^2}{i-1}{]}^{\frac{1}{2}},& N+1\≤n\≤2N\end{array}\right.$

According to above-mentioned formula iteration, obtain effective dutycycle of each equalizing circuit, realize that battery SOC in charging process reaches unanimity.

Claims (2)

1. a pulse duty ratio calculation method that is used for series power storage battery equalizing circuit switch device is characterized in that: according to the relation of lithium ion battery open-circuit voltage and SOC, simulate the relational expression of the quadratic polynomial of SOC and open-circuit voltage.According to battery charge attitude dynamic model, release battery terminal voltage and open-circuit voltage relation in the charging process, then again by the SOC value S of each battery during parameter detecting _PnCalculate balance module PWM dutycycle, reach the purpose that each cell state-of-charge reaches unanimity in charging process.

2. according to the described pulse duty ratio calculation method that is used for series power storage battery equalizing circuit switch device of claim 1, it is characterized in that: this method specifically may further comprise the steps:

When (1) switch turn-offed, the electric current on the switching tube reduced to zero immediately, then I _AvnObtain by following formula:

$I_{\mathrm{avn}}=\frac{1}{T}{\∫}_0^{D_{n}T}\frac{V_B}{L}\mathrm{tdt}=\frac{V_B{D}_n^{2}T}{2L};$

Wherein, I _AvnFor flowing into the average current of balance module, D in the one-period _nBe duty cycle of switching, T is a switch periods, V _BBe battery terminal voltage.In like manner, the average current I of one-period internal inductance release _LdnObtain by following formula:

$\left\{\begin{array}{c}{I}_{\mathrm{Ldn}}=\frac{V_B{D}_n^{2}T}{2L(2N-n)},1\≤n\≤N\\ I_{\mathrm{Ldn}}=\frac{V_B{D}_n^{2}T}{2L(n-1)},N+1\≤n\≤2N\end{array}\right..$

(2) at the equalizing circuit duration of work, the electric current that flows into accumulator except the charging current of charge power supply, the loopback electric current of the balance module of respectively working in addition, average current I _BnCalculating undertaken by following formula:

$\left\{\begin{array}{c}{I}_{\mathrm{bn}}=I_c+\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}}+\underset{i=N+1}{\overset{2N}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}},1\≤n\≤N\\ I_{\mathrm{bn}}=I_c+\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}}+\underset{i=n+1}{\overset{2N}{\mathrm{\Σ}}}{I}_{\mathrm{Ldi}},N+1\≤n\≤N\end{array}\right..$

(3) according to the relation of lithium ion battery open-circuit voltage and SOC, SOC during 20%-100%, with the relation of open-circuit voltage can be by the effective match of following quadratic polynomial:

S＝-3.712V ²+31.149V-64.363。

Consider in the battery charge dynamic process, be subjected to the influence of battery charge equivalent internal resistance and terminal resistance, battery terminal voltage that records and open-circuit voltage can be variant, so adopt battery charge attitude dynamic model, obtain battery terminal voltage and open-circuit voltage relation in the charging process:

V ₀＝V _b-I _CR。

R=R wherein _C+ R _b, be the total internal resistance of battery charge attitude.Thereby:

S＝-3.712(V _b-I _CR) ²+31.149(V _b-I _CR)-64.363。

(4),, make the SOC of each cell reach the equalization target value S of the average SOC of total battery for keeping each battery capacity balance at SOC between equalizing stage _t:

$S_t=\frac{I_C{T}_S}{Q_t}+\frac{1}{2N}\underset{n=1}{\overset{2N}{\mathrm{\Σ}}}{S}_{\mathrm{pn}};$

In fact, at the SOC balance stage, because the influence of the equalizing circuit that is subjected to respectively to work, flowing into the quantity of electric charge of a certain cell, each is variant, and its actual battery capacity is:

Q _Sn＝Q _pn+(I _bn-I _sn)T _S；

Q wherein _PnBe the battery capacity in parameter detecting stage, both sides are together divided by battery rated capacity Q _tGet actual accordingly SOC:

$S_{\mathrm{Sn}}=S_{\mathrm{pn}}+\frac{(I_{\mathrm{bn}}-I_{\mathrm{sn}})T_S}{Q_t};$

S wherein _PnEach balance module of working is the SOC value during the parameter detecting, so at the SOC balance stage, should make the actual SOC of each cell reach the balance state-of-charge S of target _t, that is:

S _t＝S _Sn

With (1), (2), (3) formula substitution formula (10), can get equalizing circuit switching tube PWM dutycycle:

$D_n=\left\{\begin{array}{cc}[\frac{2L{Q}_t(S_{\mathrm{pn}}-\frac{1}{2N}\underset{i=1}{\overset{2N}{\mathrm{\Σ}}}{S}_{\mathrm{pi}})}{V_B{\mathrm{TT}}_S}+\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}\frac{D_i^2}{2N-i}+\underset{i=N+1}{\overset{2N}{\mathrm{\Σ}}}\frac{D_i^2}{i-1}{]}^{\frac{1}{2}},& 1\≤n\≤N\\ [\frac{2L{Q}_t(S_{\mathrm{pn}}-\frac{1}{2N}\underset{i=1}{\overset{2N}{\mathrm{\Σ}}}{S}_{\mathrm{pi}})}{V_B{\mathrm{TT}}_S}+\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{D_i^2}{2N-i}+\underset{i=n+1}{\overset{2N}{\mathrm{\Σ}}}\frac{D_i^2}{i-1}{]}^{\frac{1}{2}},& N+1\≤n\≤2N\end{array}\right..$

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