CN100498367C - Electric vehicle accumulator internal resistance pulse detecting method - Google Patents

Abstract

The invention relates to an impulse detection method for the accumulator inherent resistance of the electric automobile which can measure many batteries. So it can solve the separating problem of the detected circuit and the battery group and the frequent tests, also it can detect online. The collecting module of invention is the optical couple with the transformer separated inherent resistance, and it computes the inherent resistance by the non-sine electricity. The optical couple is to separate the injecting signal and the impulse cluster signal is instead of the sine AC signal. The transformer is to collect the voltage signal separation which the data is the Is or Ism of the constant current resource, the Vz or Vzm in inherent resistance and the phase position differencealpha. Then it computes the battery resistance by using the formula r=|Z|cosalpha. It also computes the inherent resistance r=DeltU/Is by collecting the voltage variable value and the current.

Description

A kind of electric vehicle accumulator internal resistance pulse detecting method

One, technical field:

The present invention relates to a kind of accumulator detection method, especially relate to a kind of electric vehicle accumulator internal resistance pulse detecting method.

Two, background technology:

Each battery all has internal resistance.Dissimilar internal resistance of cell differences.The battery of same type is because the inconsistent internal resistance of inner chemical characteristic is also different.The internal resistance of battery is very little, is generally micro-ohm or milliohm level (the 2V accumulator internal resistance of general 400Ah is approximately about 0.5 milliohm).Internal resistance is an important technology index weighing battery performance.Under the normal condition, the large current discharging capability of the battery that internal resistance is little is strong, a little less than the big battery discharge ability of internal resistance.Internal resistance when a rechargeable battery dispatches from the factory is smaller, but after long-term the use, because the exhaustion of inside battery electrolytic solution, and the reduction of inside battery chemical substance activity, the internal resistance meeting increases gradually, can't normally discharge to the electric weight of inside battery greatly up to internal resistance, this moment, battery also just " was died ".The batteries that the overwhelming majority is aging all are because excessive former of internal resistance thereby scrap.

The internal resistance of battery has been an important parameter of accurately and fast judging the battery health situation by generally acknowledging.Conclusion about internal resistance and capacity is: when the internal resistance of battery greater than initial value (base value) 25% the time, battery can't be by the test of capacity.As seen the internal resistance of cell is an important parameter of reflection battery performance.Someone has done a large amount of experiments to the relation of the internal resistance of cell and capacity, and discovery can reflect the capacity condition of battery indirectly by the internal resistance that detects battery.Generally speaking, the capacity of battery is big more, and internal resistance is just more little, therefore can be by the measurement of accumulator internal resistance, the capacity of battery is carried out online evaluation.As seen, the size of internal resistance directly influences the driving force and the residual capacity of battery.

Internal resistance has following two characteristics:

1. internal resistance is not a fixed numeric values.When battery was in different state of charge, its internal resistance value was different.From the angle of technology, we generally are divided into two states to the internal resistance of battery: Charging state internal resistance and the internal resistance of discharge attitude.The measured internal resistance of cell when Charging state internal resistance refers to that battery is full of electricity fully.Discharge attitude internal resistance refers to battery back (when discharging into the cut-off voltage of standard) the measured internal resistance of cell that fully discharges.The internal resistance of the attitude of discharging generally speaking is unsettled, and the result of measurement is also high than normal value, and the Charging state internal resistance is relatively stable.For EV used, we had needed the electrolytic cell internal resistance of any time in the course of the work (dynamically internal resistance), to judge the performance and the residual capacity of battery.

2. internal resistance can't accurately be measured with general method.Because the internal resistance of battery is very little, in micro-ohm or milliohm scope, and in general measurement occasion, we require internal resistance of cell measuring accuracy error must be controlled in positive and negative 5%.So little resistance and so accurate requirement must be measured with instrumentation.

Based on above-mentioned two characteristics, internal resistance on-line testing technical difficulty is big, and the technology and equipment of each producer respectively has characteristics, and the accuracy and the antijamming capability difference of its test internal resistance are also very big.Therefore the internal resistance measuring technology has just become the core technology of whole detection system, and the quality of its test has also directly influenced the quality of whole detection system.

Internal resistance detection method commonly used:

Usually, the detection method of being used always has two kinds: direct-current discharge method and ac-current inject method.

1. direct-current discharge method

According to physical equation R=V/I, testing apparatus allow battery at short notice (be generally 2-3 second) force by a very big Constant Direct Current electric current (the big electric current of the general 40A-80A of use at present), measure the voltage at battery two ends this moment, and by formula calculate the current internal resistance of cell.The degree of accuracy of this measuring method is higher, controls properly, and the measuring accuracy error can be controlled in 0.1%.But this method has tangible weak point:

(1) can only measure high capacity cell or accumulator, small-capacity cells can't be at the big electric current of 2-3 internal loading in second 40A-80A;

(2) when battery passed through big electric current, polarization phenomena can take place in the electrode of inside battery, produced polarization resistance.So Measuring Time must be very short, otherwise the internal resistance value error of measuring is very big;

(3) big electric current has certain damage by battery to the electrode of inside battery.

(4) must under the situation of static state or off line, carry out, can't realize on-line measurement.

(5) have more a load that volume is bigger.Can increase the complexity of installing and controlling on the one hand, can increase the workload of plant maintenance on the other hand, influence the convenience of daily servicing.

The test internal resistance patented technology of U.S. Alber company " instantaneous large-current load discharge method " is different with the conventional DC electric discharge.Its course of work connects in turn every batteries to load blocks (RTM) discharge " valve " by control module (main frame) by programming signal, and (30A～70A) discharge, the time is 3.25 seconds to every batteries to the big electric current of load blocks.Discharge process is detected and is gathered the make-and-break voltage (the instant cut-off pressure reduction after sparking voltage is stable) of battery by data acquisition module (DCM); Load blocks (RTM) carrying and collection battery discharge current I.DCM and RTM all have correspondent voltage and induction by current device, measure voltage difference delta V=V2-V1 that load blocks disconnects moment, calculate internal resistance of cell value (R internal resistance=Δ V/I) accurately in view of the above, DCM, RTM and control module all have store recording, and with related data with chart and digital mode, on the PC terminal, show intuitively.

Though this method has many advantages, the same with the conventional DC electric discharge, all be not suitable for the application of EV.Except above-mentioned listed shortcoming, for EV uses, also have following not enough: because the number of battery cells of EV is many, give each cell not only mechanism's complexity of load blocks that continues, and take interior space, increase vehicle weight, directly influence every rideability of EV, such as speed, climbable gradient, acceleration and continual mileage etc.In addition, EV requires frequently to carry out the detection and the demonstration of residual capacity, and this just requires internally resistance to carry out frequent detection, certainly will influence the residual capacity of the cruising and the minimizing battery of automobile like this.We can simple computation once: suppose that the EV electric battery is made up of 24 joint 12V batteries.Detect discharge current and get 50A, then surveying an internal resistance power demand is P=50 * 12=600W, duration 3.25s.Required time T=24 * 3.25=78s of all battery detecting needs the consuming cells capacity C _T=50 * 78=3900C.If the battery nominal capacity is 110Ah, i.e. C _s=110 * 3600=396000C then detects an internal resistance and will waste about 1% battery capacity.If detected an internal resistance, then will survey 12 times waste capacity 12% in 1 hour in 5 minutes.This EV for " cherishing electricity as gold " is difficult to accept.

2. ac-current inject method

Need the shortcoming of heavy-current discharge, people to propose to exchange the injection mensuration in order to overcome the direct-current discharge method.Its principle is: apply a constant AC audio current source i at the accumulator two ends _s(t)=I _sCos (ω t+ α _i), general frequency is got 1KHz, and electric current is got 50mA.Detect battery terminal voltage v then _o(t)=V ₀Cos (ω t+ α _o), and i _s(t) and v _o(t) angle α between the two.According to Ohm law as can be known between the three relation shown in Fig. 7-15, (establish α _i=0), expression formula is

$Z=\frac{V_o}{{\stackrel{\·}{I}}_s}=\left|Z\right|\∠\mathrm{\α}$

Wherein: $\left|Z\right|=\frac{V_o}{I_s},$ α＝α _o-α _i

Because Z=r+jX, so have:

r＝|Z|cosα

R is the accumulator internal resistance that we need obtain.

Compole is short when exchanging the battery measurement of internal resistance measurement method, and generally about 100 milliseconds, the measuring accuracy error is generally between 1%-2%.Use the AC measurment method almost can measure all batteries.In addition, but it also have that volume is little, cost is low, to the harmless on-line measurement of battery, can carry out frequent advantages such as measurement.But measuring accuracy is subjected to effect of ripple possibly not as the direct-current discharge mensuration, simultaneously the possibility that also has harmonic current to disturb.

Three, summary of the invention:

The present invention is in order to solve the weak point in the above-mentioned background technology, a kind of electric vehicle accumulator internal resistance pulse detecting method is provided, efficiently solve the isolating problem of metering circuit and electric battery and the problem of frequent test, and can realize on-line measurement, be fit to very much the use of EV.

For achieving the above object, the technical solution used in the present invention is:

A kind of accumulator internal resistance pulse detecting method, its special character is: adopt optocoupler to add transformer isolation formula internal resistance acquisition module, and adopt the internal resistance of non-sinusoidal electricity counting cell.Optocoupler is used for the isolation of " injection " signal, replaces sinusoidal ac signal with burst signal, and transformer is used to gather the isolation of voltage signal, and the data of collection are the effective value I of constant current source _sOr maximal value I _Sm, the voltage effective value V on the internal impedance _zOr maximal value V _Zm, and phase differential α between the two.

The phase difference detection process is: the burst signal that MCU produces passes through resistance R _vProduce current i _D1, give optocoupler OP1, produce constant current i _s" injection " battery; Enter low-pass filter 1 simultaneously.i _sThe voltage signal u that on the anti-z of the internal resistance of cell, produces _zWith after the electromotive force 12V stack through capacitor C _dStopping direct current, at transformer T ₁Primary signal be exactly u _zThis voltage is through the isolated variable of transformer, at the secondary Nu that just obtained _z, N is a transformation ratio.T ₁Output voltage signal send into that amplifier amplifies and filter process, obtain the fundametal compoment of voltage, then with i _D1Fundametal compoment enter phase bit comparison testing circuit together, phase bit comparison testing circuit is sent two phase of input signals difference α into MCU; " injection " battery constant current source i _sMould value I ₀Transistor characteristic by fourier progression expanding method formula and optocoupler is calculated, and internal impedance voltage signal u, the amplification coefficient of mould value by dividing potential drop, transformation ratio and amplifier calculate.

Utilize formula r=|Z|cos α to calculate the internal resistance of cell at last.This method need detect voltage, electric current and the phase differential between them.

According to the work characteristics of EV, can obtain another kind of internal resistance computing method.When battery is not worked, allow transistor switch according to certain frequency closed and disconnected, when disconnecting, the terminal voltage of surveying battery is open-circuit voltage U _K, the terminal voltage of surveying battery when closure is on-Line Voltage U _r, then obtain the terminal voltage U of battery _EAnd output voltage u ₀Waveform, u ₀Amplitude be Δ U, so as long as with u.Amplitude measure, can pass through formula $r=\frac{\mathrm{\ΔU}}{I_s}$ Calculate internal resistance of cell r.

EV provides the MCU of an accelerator pedal working signal to the internal resistance detection module, the output high level pushes down on the pedal, output low level when not stepping on is when MCU receives low level, with regard to output pulse signal, gather Δ U, calculate internal resistance then and give main control computer,, judge battery performance and calculate remaining mileage by the internal resistance situation of main control computer according to all batteries, the accelerator pedal signal can be uploaded to main control computer by the CAN bus, again by main control computer by passing to each detection module under the CAN bus.

Compared with prior art, the advantage and the effect that have of the present invention is as follows:

1, the present invention adopts the pulse constant current signal to inject battery, has solved the isolating problem of signal source and battery.

2, the present invention adopts transformer to solve the isolating problem of Acquisition Circuit and battery.

3, the present invention can also can calculate internal resistance by the variable quantity that detects voltage by detecting the phase difference calculating internal resistance of voltage and electric current.

4, the present invention is fit to the measurement to electric battery very much, such as the application of EV (electric automobile).

Four, description of drawings:

Fig. 1 detects schematic diagram for impulse control method one internal resistance of the present invention.

Fig. 2 is a non-sinusoidal circuit diagram.

Fig. 3 is optocoupler and isoboles thereof.

Fig. 4 is the cell circuit isoboles.

Fig. 5 is a cell circuit each point oscillogram.

Fig. 6 is the train of impulses synoptic diagram.

Fig. 7 is the spectrogram of train of impulses.

Fig. 8 is the theory diagram of impulse control method two.

Fig. 9 is the equivalent circuit diagram of impulse control method two.

Figure 10 is the waveform correlation figure of impulse control method two.

Five, embodiment:

Impulse control method one:

We have known that the direct-current discharge method is not suitable for EV and uses, though and to exchange method for implanting more superior than DC-method, in EV, use still existing problems.How subject matter is measured for electric battery exactly.Single battery is used the AC method measurement and once is easy to, and the application circuit of comparative maturity is also arranged, but with after the multiple batteries serial connection, considers the isolating problem of metering circuit and electric battery and the problem of frequent test with regard to needs.

The notion of impulse control method:

The essence of AC measurment method is: one wants electric current to change, and two want electric current to change by the simple alternating current rule.The reason of wanting electric current to change is to isolate change component from the DC current (voltage) of battery, and the variable-current (voltage) that satisfies this condition has a variety of, such as triangular wave, sawtooth wave, square wave, sine wave, train of impulses etc.And select sinusoidal wave reason for use is that maturation, simple simple alternating current electrical analysis are arranged, and its ultimate principle is exactly to satisfy Ohm law between the sinusoidal voltage phasor U at an impedance Z=R+jX and its two ends and the electric current phasor I that flows through it: $Z=\frac{\stackrel{\·}{U}}{\stackrel{\·}{I}},$ And the real part among the z is a resistance be: R=|Z|cos α, α equal the phase differential of U and I.If varied non-sinusoidal electric current (voltage), then it must be expanded into the algebraic sum of sinusoidal pattern signal with fourier series, then each harmonic component is used simple alternating current electrical analysis and calculate corresponding electric current and voltage, stack up at last.Total current effective value such as certain branch road in the circuit is:

$I=\sqrt{I_0^2+I_1^2+I_2^2+\mathrm{\Λ}+I_i^2+\mathrm{\Λ}}$

The total voltage effective value of certain element is in the circuit:

$U=\sqrt{{\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="C200610104538E00171.png,C200610104538E00182.png"\; state="\{\{state\}\}">U</figure-callout>}}_0^2+{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="C200610104538E00171.png,C200610104538E00182.png"\; state="\{\{state\}\}">U</figure-callout>}}_1^2+{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="C200610104538E00182.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2+\mathrm{\&Lambda;}+U_i^2+\mathrm{\&Lambda;}}$

Wherein the i order harmonic components satisfies $Z_i=\frac{{\stackrel{\&CenterDot;}{U}}_i}{{\stackrel{\&CenterDot;}{I}}_i}.$

Such as, to circuit shown in Figure 2, when input signal is u _s=6+cost+cos2t V, its output signal equals the algebraic sum of three component result of calculations, that is:

i＝2+0.28cos(t-33.7 ⁰)+0.2cos(2t-53.1 ⁰)A

Effective value is:

$I=\sqrt{I_0^2+I_1^2+I_2^2}=\sqrt{4+0.5{\left(0.28\right)}^2+0.5{\left(0.2\right)}^2}=2.015A$

As seen the calculating of non-sinusoidal alternating circuit is pretty troublesome, so people select for use sinusoidal ac to carry out internal resistance measurement.

Will find that but think over what we needed is not voltage and current, but the real part among the impedance z is a resistance R.For a given circuit, no matter apply which kind of curtage, its active component can not become, change only be reaction component in the impedance.Promptly the real part in all harmonic impedances is the same.This means that resistance can calculate with any first harmonic component in electric current and the voltage, promptly has:

R＝|Z ₀|cosα ₀＝|Z ₁|cosα ₁＝Λ＝|Z ₁|cosα ₁

Therefore draw a conclusion: for the non-sinusoidal alternating circuit,,, can utilize formula as long as find any first harmonic electric current and component of voltage in order to calculate its resistance

R＝|Z ₁|cosα _i

Calculate.In the formula: $Z_i=\frac{{\stackrel{\&CenterDot;}{U}}_i}{{\stackrel{\&CenterDot;}{I}}_i},$ α ₁Equal

With

Phase differential.

Above-mentioned conclusion explanation can be adopted the internal resistance of non-sinusoidal electricity counting cell.This proposes the theoretical foundation of " impulse control method " just.

Why propose " impulse control method ", main cause is in order to solve the isolating problem between detection module and the electric battery.The present invention will adopt concentration/distribution formula detecting pattern to carry out the collection of related data, and therefore, the internal resistance detection module will combine with the battery voltage detection module.Realized the isolation collection of voltage data by " bridge electric capacity ", how to have isolated that to gather the internal resistance data then be a difficult point.

The main points of AC method have two: the one, and to the constant simple sinusoidal alternating current of battery input range, the 2nd, gather ac voltage signal from battery.This means and to give the battery input current and aspect battery collection output voltage two, all to carry out isolation processing.Because the electric current that injects and the voltage signal of collection all are AC signal, the quarantine measures that we at first expect adopt transformer exactly.But, think over the back and find to utilize transformer isolation to have a problem: be exactly that transformer can't produce constant current signal in battery-end.So we have proposed to utilize optocoupler+transformer isolation method.Optocoupler is used for the isolation of " injection " signal, because the secondary of optocoupler is the emitter (the e utmost point) and the collector (the c utmost point) of a transistor amplifier, its equivalent electrical circuit just in time is a constant current source, sees Fig. 3.So, can produce the controlled current source of isolation.But the problem that optocoupler exists is to be not suitable for transmission of analogue signal, and for this reason, the present invention adopts burst signal to replace sinusoidal ac signal.According to fourier series, train of impulses can expand into the algebraic sum of sinusoidal pattern signal, can take out fundamental signal by low-pass filter, and fundamental signal is exactly the sinusoidal pattern AC signal.Transformer is used to gather the isolation of voltage signal, because the voltage on the internal impedance is the train of impulses voltage u that " injection " electric current produces _zWith the algebraic sum of cell voltage, so, capacitor C passed through _dThe stopping direct current effect, that be added in primary is exactly the train of impulses voltage u that " injection " electric current produces _z, just obtain being proportional to u at transformer secondary output _zOutput voltage signal.

Optocoupler+transformer isolation formula internal resistance acquisition module the schematic diagram of the present invention's design is seen Fig. 1.The data of gathering are the effective value I of constant current source _s(or maximal value I _Sm), the voltage effective value V on the internal impedance _z(or maximal value V _Zm) and phase differential α between the two.

The phase difference detection process is such: the burst signal that MCU produces passes through resistance R _vProduce current i _D1, give optocoupler OP1, produce constant current i _s" injection " battery; Enter low-pass filter 1 simultaneously.i _sThe voltage signal u that on the anti-z of the internal resistance of cell, produces _zWith after the electromotive force 12V stack through capacitor C _dStopping direct current, at transformer T ₁Primary signal be exactly u _zThis voltage is through the isolated variable of transformer, at the secondary Nu that just obtained _z, N is a transformation ratio.T ₁Output voltage signal send into that amplifier amplifies and filter process, obtain the fundametal compoment of voltage, then with i _D1Fundametal compoment enter phase bit comparison testing circuit together, phase bit comparison testing circuit is sent two phase of input signals difference α into MCU.

" injection " battery constant current source i _sMould value I ₀Can calculate by the transistor characteristic of fourier progression expanding method formula and optocoupler.And internal impedance voltage signal u _zThe mould value can calculate by the amplification coefficient of dividing potential drop, transformation ratio and amplifier.Like this, calculating the required parameter of internal resistance has just all obtained.

According to above-mentioned detection principle, we find and common ac-current inject method not quite alike, mainly difference is:

(1) giving the constant current signal of battery is not that external power provides (injection), but takes from battery itself.Because, though transistorized output circuit equivalence is a current source, but its energy is not from base stage, it is input circuit, but obtain with the big electric current of the little Current Control output loop of input circuit, this transistorized just work essence, be so-called transistor " amplification ", be not directly will import small-signal to become large-signal output, but the large-signal of going to the control output end with the input small-signal, making it to change with the variation of small-signal, look from the transistor outside, just looks like to be that small-signal is enlarged into large-signal.

(2) current source is not sinusoidal ac but train of impulses.

(3) detect and the detected circuit isolation, be fit to the detection of series battery.

Therefore, we are named as this method " impulse control method one " according to These characteristics.

2. correlation computations

The equivalent electrical circuit of cell circuit as shown in Figure 4.Suppose that accumulator internal resistance is the milliohm order of magnitude, such as 1 milliohm (1m Ω), if constant current source i _sAmplitude (or effective value) be 1A, the maximal value of voltage 1mV just in the internal resistance then.And generally the output current of optocoupler is less than 100mA, and the output of Darlington type can reach

Such as PC725.If getting the output current of optocoupler PC725 is 100mA, is exactly 0.1 * 0.001=0.0001V=100 μ V in the ohmically pressure drop of 1m Ω.That is to say u _zMaximal value V _0mBe no more than 100 μ V.Because voltage is very little, just require testing circuit very sensitive, precision is very high, and anti-noise ability is also very strong.

The representative value of optocoupler PC725 transfer ratio ^[95]For $\frac{I_C}{I_F}=4000\%.$ If get the working current maximal value is 100mA (leaving surplus), just I _c=I _Sm=100mA, then optocoupler input end current maxima is I _F=I _D1m=2.5mA.At this moment, output end voltage is 2V, and input terminal voltage is 1.2V ^[95]Resistance then $R_V=\frac{5-1.2}{2.5}=1.5K.$

Thereby the purpose of measuring internal resistance is to want the residual capacity of counting cell to calculate continual mileage.And continual mileage does not need frequent understanding.Because generally about 200 kilometers, its top speed is at 100km/h for the EV continual mileage of use lead-acid battery, according to people's driving habits and continual mileage computational accuracy, we get and calculated once in per 1 minute, are equivalent to several kilometers detections once again.The time of detecting an internal resistance is decided to be 1 second, so, and the frequencies omega of train of impulses ₀=2 π f ₀=1/T should get height a little a bit (such as, f ₀=1KHz), and the characteristic of determining also will consider low-pass filter of this value.Like this, we provide the theoretical waveforms of " injection " electric current, internal impedance voltage and battery terminal voltage, see Fig. 5.

If the voltage signal of optocoupler input end is the burst signal that is produced by MCU, as shown in Figure 6.Then according to the fourier series theory, the fourier progression expanding method formula of this signal is:

$f\left(t\right)=\frac{A}{2}+\frac{2A}{\mathrm{\&pi;}}[\sin {\mathrm{\&omega;}}_{0}t+\frac{1}{3}\sin 3{\mathrm{\&omega;}}_{0}t+\frac{1}{5}\mathrm{<figure-callout\; id="5"\; label="sin"\; filenames="C200610104538E00182.png"\; state="\{\{state\}\}">sin</figure-callout>}5{\mathrm{\&omega;}}_{0}t+\frac{1}{7}\sin 7{\mathrm{\&omega;}}_{0}t+\mathrm{\&Lambda;}]$

A is a signal amplitude in the formula, gets A=1.2V herein, and its spectrogram as shown in Figure 7.

As seen, if with one by frequency less than 3 ω ₀Low-pass filter (LPF) just fundametal compoment can be taken out.Therefore, be provided with the fundametal compoment that two low-pass filters take out train of impulses electric current and voltage respectively at Fig. 3 and be used to calculate internal resistance.

By foregoing, can know current i _sFundametal compoment I _S0Need not measure and can directly calculate, and voltage u _zFundametal compoment V ₀Take out by filtering, the A/D converter of sending into MCU again just can obtain.Like this, be used to calculate three parameter: I of internal resistance _S0, V ₀Just all obtained with α.

Because this method is the same with AC method, also be to lean on the phase differential of counting cell voltage and current to calculate internal resistance at last, for distinguishing mutually, so be referred to as " impulse control method one " with the following another kind of computing method that will introduce.

No matter be ac-current inject method or the impulse control method one that proposes, can online at any time measure, this is their advantage.But for EV, motor is not all to work all the time, such as brake, when slowing down, and just not electricity consumption of motor, battery is not just worked.And in the vehicle ' process of reality, brake and deceleration are more frequent, and the work that is to say battery is intermittent.These characteristics provide an other thinking of calculating internal resistance for us.

Impulse control method two:

We know that battery is because of the existence of internal resistance, its open-circuit voltage U _KWith on-Line Voltage U _rThere is a potential difference (PD) Δ U=U _K-U _rAnd the internal resistance of cell is $r=\frac{\mathrm{\&Delta;U}}{I_s},$ I _sWorking current for battery.As seen, if I _sBe steady current, can obtain internal resistance r as long as then measure Δ U.Referring to Fig. 9, when battery is not worked,, allow transistor switch according to certain frequency (such as 100Hz) closed and disconnected such as slowing down period or brake period, when disconnecting, the terminal voltage of surveying battery is open-circuit voltage U _K, the terminal voltage of surveying battery when closure is on-Line Voltage U _r, the terminal voltage U of battery then _EAnd output voltage u ₀Waveform see Figure 10.Because u ₀Amplitude be Δ U, so as long as with u ₀Amplitude measure, can pass through formula $r=\frac{\mathrm{\&Delta;U}}{I_s}$ Calculate internal resistance of cell r.Because this method does not need the phase differential of calculating voltage and electric current, so, this computing method are called " impulse control method two ".

During application process two, require EV to provide the MCU of an accelerator pedal (gas pedal) working signal to the internal resistance detection module, such as the output high level that pushes down on the pedal, output low level when not stepping on.When MCU receives low level, with regard to output pulse signal, gather Δ U, calculate internal resistance then and give main control computer, by the internal resistance situation of main control computer, judge battery performance and calculate remaining mileage according to all batteries.The accelerator pedal signal can be uploaded to main control computer by the CAN bus, again by main control computer by passing to each detection module under the CAN bus.

The electric theory diagram of method two is seen Fig. 8.As seen, the signals collecting hardware of " impulse control method one " and " impulse control method two " is the same with principle, the different computing method of being, and " method one " wants the phase differential of calculating voltage and electric current, and be cumbersome; And " method two " only needs the variable quantity of calculating voltage.They are compared with common " ac-current inject method ", and great advantage is to isolate image data, thereby the data acquisition that is more suitable for series battery is used.

Claims (3)

1, a kind of electric vehicle accumulator internal resistance pulse detecting method, it is characterized in that: adopt optocoupler to add transformer isolation formula internal resistance acquisition module, and the internal resistance of employing non-sinusoidal alternating circuit counting cell, optocoupler is used for the isolation of " injection " signal, replace sinusoidal ac signal with burst signal, transformer is used to gather the isolation of voltage signal, and the data of collection are the effective value (I of constant current source _s) or maximal value (I _Sm), the voltage effective value (V on the internal impedance _z) or maximal value (V _Zm), and the effective value (I of constant current source _s) with internal impedance on voltage effective value (V _z) or constant current source maximal value (I _Sm) with internal impedance on voltage max (V _Zm) between the two phase differential (α); When battery is not worked, allow transistor switch according to certain frequency closed and disconnected, when disconnecting, the terminal voltage of surveying battery is open-circuit voltage (U _K), the terminal voltage of surveying battery when closure is on-Line Voltage (U _r), then obtain the terminal voltage (U of battery _E) and output voltage (u ₀) waveform, output voltage (u ₀) amplitude be Δ U, with output voltage (u ₀) amplitude measure, can pass through formula $r=\frac{\mathrm{\&Delta;U}}{I_s}$ Calculate the internal resistance of cell (r).

2, a kind of electric vehicle accumulator internal resistance pulse detecting method according to claim 1, it is characterized in that: the phase difference detection process is: the burst signal that microcontroller produces is by resistance (R _V) generation electric current (i _D1), give optocoupler (OP1), produce constant current (i _s) " injection " battery; Electric current (i _D1) enter low-pass filter (1) simultaneously; Constant current (i _s) go up the voltage signal (u that produces at the internal resistance of cell anti-(z) _z) with electromotive force 12V stack after through electric capacity (C _d) stopping direct current, at transformer (T ₁) primary signal be exactly voltage signal (u _z), this voltage is through the isolated variable of transformer, at the secondary transformation ratio (Nu that just obtained _z), transformer T ₁Output voltage signal send into that amplifier amplifies and filter process, obtain the fundametal compoment of voltage, then with electric current (i _D1) fundametal compoment enter phase bit comparison testing circuit together, phase bit comparison testing circuit is sent two phase of input signals poor (α) into microcontroller; " injection " battery constant current source (i _s) mould value (I ₀) calculate by the transistor characteristic of fourier progression expanding method formula and optocoupler, and internal impedance voltage signal (u _z) the amplification coefficient of mould value by dividing potential drop, transformation ratio and amplifier calculate.

3, a kind of electric vehicle accumulator internal resistance pulse detecting method according to claim 2, it is characterized in that: electric automobile provides the microcontroller of an accelerator pedal working signal to the internal resistance detection module, the output high level pushes down on the pedal, output low level when not stepping on, when microcontroller is received low level, with regard to output pulse signal, gather Δ U, calculate internal resistance then and give main control computer, by the internal resistance situation of main control computer according to all batteries, judge that battery performance also calculates remaining mileage, the accelerator pedal signal is uploaded to main control computer by the CAN bus, again by main control computer by passing to each detection module under the CAN bus.

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