CN103760492A - Method for online testing performance of lead-acid storage cells of transformer substation - Google Patents

Abstract

The invention discloses a method for online testing performance of lead-acid storage cells of a transformer substation. The method includes the steps that capacity of each single storage cell body is acquired through an instantaneous discharge method, the inner resistance of each single storage cell body is detected through an alternating current phase method, the instantaneous discharge method is corrected by the alternating current phase method, interference of the instantaneous discharge method in neighbors of open-circuit cells is eliminated, and then real-time online nondestructive testing of the performance of a storage cell set is achieved. According to the method for online testing the performance of the lead-acid storage cells of the transformer substation, the instantaneous discharge method and the alternating current phase method are combined, the inner resistance, the capacity and other performance parameters of each single storage cell body can be measured in real time, and then the cells with degraded performance can be found in time at the early stage of degradation of the storage cells, and severe direct current system accidents caused by degradation accumulation and intensification of the storage cells are avoided.

Description

A method for online performance testing of lead-acid batteries in substations

technical field

The invention relates to an on-line performance testing method of a substation lead-acid storage battery, which relates to the field of substation direct current power supply monitoring.

Background technique

The DC power supply part of the substation in the power system is composed of battery packs, charging modules, DC screens and other equipment. As a DC backup power supply, the battery is usually in a floating charge state. Once the AC power fails, the battery can supply power to the DC system. At present, most of the batteries used in substations are "maintenance-free batteries", namely: valve-regulated sealed lead-acid batteries (VRLA). The so-called "maintenance-free" means that there is no need to add water, add acid, change fluid and other maintenance. The detection of the performance state of the battery is only to measure the floating charge voltage and current of the battery pack; the real capacity of the battery cannot be accurately measured. Predicting the usable time of the battery causes many potential safety hazards in the operation of the valve-regulated sealed lead-acid battery pack, which seriously affects the safe operation of the DC system.

The existing battery performance testing methods are as follows:

1) Method for measuring float voltage:

Manually measure directly with a multimeter, or measure the floating charge voltage of the battery through monitoring equipment. The measurement of the float voltage can prevent the float voltage from being too high or too low. But practice has proved that VRLA batteries have no correlation between terminal voltage and capacity. From the static floating charge voltage, it is impossible to accurately judge the performance of the battery.

2), AC impedance/conductance test method:

Impedance test: Load an AC current of known frequency and amplitude across the battery pack, and measure the AC voltage drop of each cell/unit. The measured value of the AC voltage is taken from the maximum value (or average value, maximum value) of the positive and negative poles of each monomer, and the impedance is calculated using Ohm's law. Conductance test: load a voltage of known frequency and amplitude on the monomer/element, and measure the response value of its alternating current. Conductance is the measured AC current divided by the voltage value. The disadvantage is that there is no linear correspondence between impedance or conductance and battery capacity, and the data needs to be analyzed after the measurement results are obtained.

3) Internal resistance test method:

Internal resistance test: add a load to both ends of the monomer/element, measure the step change value of its current and voltage, divide the change value of voltage by the change value of current to get the internal resistance value. Instantaneous large current discharge test internal resistance value, due to the use of direct current method, can well solve the problem of the influence of battery parasitic capacitance. Because a large current test is used, it also solves the problems of accuracy and charger ripple current interference. Disadvantages are: for the battery pack connected in series, the open-circuit battery has a great influence on the test of the internal resistance of adjacent batteries. In addition, the internal resistance and capacity do not have a completely linear correspondence. After the internal resistance test, manual analysis is still required to judge the battery condition.

4), voltage method:

The voltage method mainly measures the size of the open circuit voltage and the load voltage, and the decrease of the open circuit voltage and the load voltage indicates that the capacity is insufficient. The open circuit voltage has a good correspondence with the battery capacity. The disadvantage is that the measurement of the open circuit voltage must be carried out in the offline state of the battery, and it must be stable for more than two hours, so it cannot be put into the current substation battery.

In addition, there are instantaneous discharge method and AC phase method. The instantaneous discharge method can detect the true internal resistance of a single battery, but since the battery packs are connected in series, if an open-circuit battery appears, it will affect the test results of the batteries near the series. The AC phase method is an effective on-line real-time detection method for batteries, but in the actual application process, the reliability of the detection results is greatly reduced due to the influence of various disturbances such as component tolerances and charger ripple.

Contents of the invention

In view of this, the present invention provides an on-line performance testing method of a lead-acid storage battery in a substation, which adopts a method combining an instantaneous discharge method and an AC phase method. It can measure the internal resistance, capacity and other performance parameters of each single battery in real time, so as to detect the battery with degraded performance in the early stage of battery deterioration. Avoid serious DC system accidents due to the accumulation and aggravation of battery deterioration.

The technical solution adopted by the present invention is: an online performance test method for lead-acid batteries in substations. The capacity of each battery cell is obtained by the instantaneous discharge method, and the internal resistance of each battery cell is detected by the AC phase method, and the AC phase The method corrects the instantaneous discharge method, eliminates the interference to the neighborhood of the open-circuit battery in the instantaneous discharge method, and realizes the real-time online nondestructive testing of the performance of the battery pack.

Step 1: The battery pack is connected to the charger, and the charger supplies power to the DC load. The battery pack is in the state of floating charging, and the internal resistance of the battery is tested by the instantaneous discharge method;

Step 2: The AC small signal generated by the low-frequency AC signal generator is amplified by the coupling drive circuit and then applied to both ends of the battery pack to measure the AC voltage V0 at both ends of the single battery. Due to the existence of the internal impedance of the battery, the output of the battery is AC There is a phase difference between the current waveform and its input waveform, and the internal resistance of the battery is calculated by measuring the phase difference of the input and output voltage waveforms of batteries with different capacities.

In said step 1: the battery pack includes a plurality of battery cells, and the multiple battery cells are divided into two groups, each group uses a high-power resistor as a discharge load, and the controller controls two solid state relays in time-sharing to complete the instantaneous discharge operation , while using a voltage sensor and a current sensor to collect the discharge voltage and discharge current of each battery cell before and after discharge.

In said step 2: use a signal generator to generate a sine wave signal, add it to the battery pack through a DC blocking capacitor, and then pass the signal of the battery pack to ground through a grounding resistor and a DC blocking capacitor to measure the phase of the input and output signals of the battery The impedance is calculated from the phase difference.

The difference area method is used to calculate the phase difference of the two waveforms.

The present invention is a substation lead-acid storage battery online performance testing method, and the technical effects are as follows:

1) The instantaneous discharge method and the AC phase method are supplemented and corrected to form a comprehensive evaluation system. The internal resistance of each single battery is obtained by the instantaneous discharge method, and the correction of the instantaneous discharge method by the AC phase method eliminates the interference to the neighborhood of the open-circuit battery in the instantaneous discharge method, and effectively realizes the real-time online non-destructive testing of battery performance.

2) Using the instantaneous discharge method and the AC phase method to accurately test the internal resistance of the lead-acid battery in the substation;

3) It can accurately detect when the capacity of lead-acid batteries in substations changes in a small range;

4) In extreme cases such as sudden open-circuit batteries, it is possible to pick out deteriorated batteries in time without affecting the measurement of other batteries;

5) It is possible to detect performance-deteriorated batteries in the early stage of battery deterioration, so as to avoid serious DC system accidents due to the accumulation and aggravation of battery deterioration.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is further described:

Figure 1 is a schematic diagram of a basic battery model;

Figure 2 is an equivalent model diagram of battery AC impedance;

Figure 3 is a simplified equivalent model of battery AC impedance;

Fig. 4 is the complex plane diagram of battery impedance;

Figure 5 is the battery AC equivalent impedance model;

Figure 6 is the relationship between battery capacity and internal resistance;

Fig. 7 is the battery equivalent model of instantaneous discharge method;

Fig. 8 is the test circuit diagram of instantaneous discharge method;

Fig. 9 is the battery discharge characteristic curve;

Fig. 10 is the test circuit of instantaneous discharge method;

Figure 11 is the equivalent series circuit of the AC proportional method;

Fig. 12 is a schematic block diagram of the AC phase method;

Fig. 13 is a schematic diagram of the signal acquisition subsystem of the present invention;

Fig. 14 is a schematic diagram of the zero-crossing comparison method;

Figure 15 is a phase difference measurement waveform diagram;

Fig. 16 is a schematic diagram of the zero-crossing comparator of the present invention;

Fig. 17 is the phase difference waveform diagram obtained by the area method of the present invention;

Fig. 18 is a schematic diagram of the AC method test of the present invention.

Detailed ways

Principle analysis:

The advantages and disadvantages of the existing battery on-line monitoring method can be seen: the secondary voltage method (instantaneous discharge method) is accurate for monomer detection. However, when there is an open-circuit single cell, or when there is a single cell in the whole group with poor performance, the experimental comparison shows that it will cause serious detection errors to several cells connected in series near the single cell. The AC phase method can effectively correct the deficiency of the secondary voltage method. Therefore, the present invention combines the secondary voltage method and the AC phase method to comprehensively analyze and evaluate the performance of each monomer of the storage battery. The voltage, internal resistance, and reference remaining life of each cell are obtained.

Battery internal resistance includes: ohmic resistance and polarization resistance. Ohmic internal resistance includes: the resistance of all components such as electrodes, diaphragms, electrolytes, connecting bars and poles inside the battery. The polarization internal resistance is the resistance equivalent to the electrode polarization in the electrochemical reaction inside the battery. According to different understandings of the internal resistance of the battery, different battery models can be established. The common ones are the basic model and the AC impedance equivalent model. Let's analyze these two models:

1. The common battery model is shown in Figure 1. This model consists of an ideal battery E0 (its voltage is E0) and an equivalent internal resistance r. V0 is the terminal voltage of the battery, and I is the current flowing through the battery. According to the whole circuit Ohm's law:

I=V0-E0/r (1)

The model does not take into account changes in the internal resistance of the battery due to changes in the battery state of charge, changes in electrolyte concentration, and sulfate formation. This model is only suitable if it is assumed that infinite energy is available from the battery, or if the battery state of charge is not important.

2. The AC impedance equivalent model of the battery: as shown in Figure 2, C is the equivalent value of the electric double layer capacitance of the positive and negative electrodes, and R _Ω is the ohmic internal resistance of the battery. The ohmic internal resistance is composed of the electrode material, the diaphragm, the electrolyte, and the resistance of the terminal. It affects the output characteristics of the battery, the temperature rise during charging and discharging, etc. The total Faradaic impedance Z of the battery can be represented by the real part R and the imaginary part X, namely:

Z=R-jX (2)

When the frequency of alternating current is low enough, the electrode reaction can be considered to be reversible. At this time, the electrode reaction speed is controlled by the diffusion process, and the following relationship exists between X and R:

X=RR _Ω -R _t +2λ ² C _d (3)

Therefore, if the X and R measured at different frequencies are plotted in the complex plane, a straight line with a slope of 45° will be obtained. When the alternating current frequency is high enough, the electrode reaction can be considered to be completely irreversible. At this time, the electrode reaction speed is mainly controlled by the battery transfer resistance Rt, and the battery equivalent model can be simplified as shown in Figure 3. R _C is the equivalent polarization resistance, which is the resistance of chemical polarization and concentration polarization. It involves the effective area of the electrode, the kinetics of the electrode process and the ion transport characteristics, and its characteristics do not conform to Ohm's law.

At this point, there is the following relationship between X and R:

${<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; \&Omega;</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Therefore, the X-R complex plane is a semicircle.

From the above analysis, we can see that the complex plane diagram of battery impedance can be represented by Figure 4.

The present invention adopts the battery AC equivalent impedance Z model, as shown in FIG. 5 .

In the figure: R ₁ , R ₂ —— Polarization resistance of positive and negative electrodes;

C ₁ , C ₂ —— Polarized capacitance of positive and negative electrodes;

L——lead inductance;

R _Ω —— battery ohmic resistance.

The battery ohmic resistance RΩ characterizes the charge level of the battery.

In order to simplify the measurement, only the pure resistance R (R is composed of R1, R2, and R _Ω ) is usually separated from the equivalent impedance Z. There is a linear relationship between R and R _Ω , so R can be used to indirectly characterize the battery charge level.

Through a large number of experiments on the relationship between the internal resistance and capacity of the battery, it is found that the capacity of the battery can be indirectly reflected by monitoring the internal resistance of the battery. Generally speaking, the larger the capacity of the battery, the smaller the internal resistance. Therefore, the capacity of the battery can be evaluated online by measuring the internal resistance of the battery. The relationship between battery capacity and internal resistance is shown in Figure 6, so detecting internal resistance can determine the remaining capacity of the battery. In this way, the performance of the battery is analyzed, and various potential safety hazards in the operation of the battery are found, which provides an important guarantee for ensuring the stable and reliable operation of the battery.

Through a large number of experiments on the relationship between the internal resistance and capacity of the battery, it is found that the capacity of the battery can be indirectly reflected by monitoring the internal resistance of the battery. Generally speaking, the larger the capacity of the battery, the smaller the internal resistance, so the battery capacity can be evaluated online by measuring the internal resistance of the battery. The relationship between battery capacity and internal resistance is shown in Figure 6. Therefore, detecting the internal resistance can determine the remaining capacity of the battery, thereby analyzing the performance of the battery and discovering various safety hazards in the operation of the battery. In order to ensure the stability and reliability of the battery The operation provides an important guarantee.

3. The principle and implementation of instantaneous discharge method test:

The instantaneous discharge method is to discharge the battery with a large current instantaneously, measure the instantaneous voltage drop on the battery, and calculate the internal resistance of the battery through Ohm's law. In the case of instantaneous DC, the equivalent model of the battery can be considered to be composed of a voltage source and an internal resistance connected in series (Thevenin equivalent model), as shown in Figure 7. Among them, Rin: battery internal resistance; I: instantaneous current; RL: load resistance. Calculation formula for battery internal resistance: R _in =ΔU/I; ΔU is the voltage change before and after instantaneous discharge of the battery. The test circuit is shown in Figure 8, the switch is closed, and after a delay for a period of time, the current reaches a steady state, and the current value I and the voltage value U ₁ are recorded. After disconnecting the switch K, record the instantaneously recovered voltage value U ₂ , and at the same time record the voltage fluctuations at both ends of the battery during the whole process. The reason why it is necessary to delay the next test for a period of time is mainly because in the process of switching on, due to the existence of capacitance, there will inevitably be an inrush current. In order to reduce the impact of the impact current on the test results, a certain time delay is adopted. At the same time, this short delay can also allow the battery to gradually tend to a relative equilibrium state from the initial violent chemical reaction.

After the battery is fully charged, record its internal resistance when it is in the floating charge state, and draw a voltage fluctuation diagram accordingly. When the battery is discharged with different values of current, the terminal voltage drop is also different. Figure 9 shows the discharge characteristic curves of the same storage battery under different discharge current conditions. It can be seen from Figure 9 that the greater the discharge current, the lower the terminal voltage drops during the entire discharge process, and the faster the drop rate, this is because when the discharge current is large, the consumption of sulfuric acid in the reaction zone is also large, but The replenishment rate is very small. Therefore, the electrolyte density in the plate pores must drop lower and faster. Moreover, when the discharge current is large, the voltage drop on the internal resistance is also large, so the terminal voltage drops rapidly, and the phenomenon of discharge termination occurs in advance, so the larger the discharge current of the battery, the shorter the discharge duration. However, when the discharge current exceeds a certain range, the change in internal resistance is not very large. At this time, the damage to the battery caused by high current discharge should be considered.

Therefore, from the experimental point of view, when using instantaneous large current discharge for internal resistance test, the allowable discharge current range should be selected within 0.3 ~ 0.5Co (Co refers to the capacity of the battery), so that better accuracy can be obtained, and at the same time Can avoid damage to the battery. From the experiment and analysis, we can know that this method can effectively avoid the influence of AC noise, so as to achieve better test accuracy, and also avoid the traditional long-time discharge, and get the test results quickly.

Example:

The present invention is an on-line performance testing method of a lead-acid battery in a substation. The capacity of each battery cell is obtained by the instantaneous discharge method, and the internal resistance of each battery cell is detected by the AC phase method, and the AC phase method corrects the instantaneous discharge method. , eliminating the interference to the neighborhood of the open-circuit battery in the instantaneous discharge method, and realizing real-time online non-destructive testing of battery performance.

The test circuit of the present invention is shown in FIG. 10 . The battery pack in the substation is connected to the charger, which usually supplies power to the DC load. The battery pack is in a floating charge state. In order to test the internal resistance of the battery by the instantaneous discharge method. The present invention takes the single 12V storage battery as an example. There are 18 batteries in the whole group. The 18 batteries are divided into two groups. Each group uses a 12Ω high-power resistor as the discharge load. The controller controls two solid-state relays in time-sharing to complete Instantaneous discharge operation. At the same time, the voltage and current sensors are used to collect the voltage and discharge current of each battery before and after discharge, and the internal resistance of each battery is calculated by the formula. The main reason for using this circuit is to avoid the wrong discharge of the charger.

Theoretically speaking, there are three voltage states during the discharge process of the battery, as shown in Figure 11, where there are two voltage changes: ① the drop value of the battery voltage when the load is applied to the test circuit; ② the drop value of the battery voltage when the load is disconnected Instantly, the battery voltage recovers to its value. During the experiment, the voltage and current at the moment of switching on are easy to introduce a large impact, resulting in a large error, so the voltage drop value is uniformly used, and the current has basically reached a steady state at this time. In the actual test process, Test the voltage once 2 seconds after the discharge is turned on, and test the voltage immediately after disconnecting the discharge module to obtain ΔU in Figure 11, and then use the internal resistance calculation formula in Figure 7 to calculate, R _in =ΔU/I.

The AC phase method is to measure the internal resistance of the battery by measuring the voltage feedback of the battery to an AC signal of a certain frequency injected into it. The advantages of the AC method are: no need to discharge, it is the safest way to test the internal resistance; it can test the internal resistance of the battery in any state such as charging and discharging; it can reflect the polarization internal resistance of the battery; it can adapt to different conditions by selecting the signal frequency. types of batteries. The existing AC methods include the AC proportional method and the AC phase method.

(1) AC ratio method:

The internal resistance of the battery is measured by the AC ratio method, that is, the battery is connected in series with a high-precision resistor, and the equivalent series circuit is shown in Figure 11. The internal resistance of the battery can be calculated by using a special-purpose chip to measure and compare the effective value of the AC signal voltage division between the battery and the precision resistor. In Figure 11, R _θ is a high-precision resistance, the dotted line is the equivalent circuit of the battery, R _Ω is the ohmic internal resistance of the battery, Rc is the polarization internal resistance, and C is the inter-electrode capacitance, then the equivalent impedance of the battery is:

Z= _RΩ +Rc/(1+JωCRc) (5)

Where: R _Ω is the resistance of the signal generation circuit. The current of the AC signal flowing through the series circuit is:

I=Ui/(Z+R _θ )=u2/R _θ (6)

The variables in formula (6) are all complex numbers and have a proportional relationship. If the modulus operation is performed on them, the proportional relationship still has the modulus of the AC signals u1 and u2 are their effective values V1 and V2 respectively. Therefore, as long as the battery is measured And the effective value of the high-precision resistance to the voltage division of the AC signal, the modulus of the equivalent impedance of the battery can be calculated:

|Z|=U1|R _θ /|U2| (7)

It is a combination of battery ohmic internal resistance, polarization internal resistance and inter-electrode capacitance, which can be used as the equivalent internal resistance of the battery:

|Z|=V1R _θ /V2 (8)

(2) AC phase method:

The AC phase method measures the internal resistance of the battery online, that is, injects a low-frequency AC current signal into the battery. In the project, there are restrictions on the frequency and magnitude of the injected signal to ensure that the performance of the battery is not affected, and then the low-frequency AC voltage V ₀ and the low-frequency AC current Is flowing through the battery and the phase difference α between the two are measured, according to the formula Z=V ₀ /Is, R=Zcosα, so as to calculate the internal resistance of the battery, the schematic diagram is shown in Figure 12. Since the AC method does not need to discharge, it does not need to be static or offline, and can realize complete online monitoring and management. The impact on the safety of equipment operation is avoided. At the same time, because the frequency of the applied low-frequency AC signal is very low and the current is very small, it will not adversely affect the performance of the power system.

Based on the AC phase method, the present invention adopts the simplified equivalent circuit model of the storage battery as shown in Figure 3. The AC small signal generated by the low-frequency AC signal generator is amplified by the coupling drive circuit and then added to both ends of the storage battery pack to measure the single storage battery The AC voltage V0 at both ends, due to the existence of the internal impedance of the battery, produces a phase difference between the output AC current waveform of the battery and its input waveform, and the phase difference decreases with the increase of the internal resistance of the battery, while the internal resistance of the battery increases with decreasing capacity. Therefore, the phase difference of the input and output signals of the battery will decrease as the capacity decreases. The internal resistance of the battery can be calculated by measuring the phase difference of the input and output voltage waveforms of batteries with different capacities. Since the AC method does not need to be discharged, it does not need to be static or offline, and it can realize complete online monitoring and management, avoiding the impact on the safety of equipment operation.

At the same time, since the frequency of the applied low-frequency signal is very low, the applied AC current is also very small, so it will not adversely affect the performance of the power supply system. The specific implementation process is as follows: Use a signal generator (ICL8038 chip) to generate a sine wave signal, add it to the battery pack through a DC blocking capacitor, and then pass through a grounding resistor of about 10Ω and a DC blocking capacitor to ground the signal passing through the battery pack. The DC blocking capacitor is small, about 1uF. To measure the impedance of the battery, it is necessary to measure the phase difference of the input and output signals of the battery, and calculate the impedance according to the phase difference. Fig. 13 is a schematic diagram of the signal acquisition subsystem of the present invention.

When collecting data, a line is drawn from both ends of each storage battery, and then sent to the multi-way switch after passing through a DC blocking capacitor, and then sent to the data acquisition board. Each line of the battery pack can be controlled by controlling the multi-way switch. The single battery is tested for cycle. The phase difference obtained at this time cannot be considered to be caused by the internal resistance of the battery. Because DC blocking capacitors are connected when collecting battery voltage, even if the models, sizes, and manufacturers of these DC blocking capacitors are the same, there will still be tolerances, which will also cause phase differences between the input and output signals of the battery. Therefore, the internal resistance of the battery cannot be determined only by collecting the phase difference once. The phase difference of the input and output signals of the battery will decrease with the decrease of the capacity, but the phase difference caused by the tolerance of the DC blocking capacitor is constant, so we can calculate the internal resistance of the battery according to the change of the phase difference. In order to obtain the phase difference, the capacity of the battery must be changed, even if the battery discharges the load. Data acquisition is performed once when the storage battery has just been charged, and then the storage battery is discharged, and data acquisition is performed again at regular intervals. As the discharge time increases, the phase difference will gradually decrease, so the present invention utilizes the signal acquisition system to This phase difference is collected. The detected phase difference of the input and output voltage signals of the battery is actually the phase difference between the battery voltage and current, combined with the amplitude of the AC voltage and the amplitude of the entire set of current, according to the formula Z=V0/Is, R=Zcosα Calculate the internal resistance of the battery. The traditional method for calculating the phase difference between two waveforms is the zero-crossing comparison method, and the basic principle is shown in Figure 14. The two sampled signals are filtered out various interference signals by the filter and linearly amplified to become a sinusoidal signal with regular waveform and appropriate amplitude, such as the signal a﹑b in Figure 14. After passing through the zero comparator, the sinusoidal signal becomes Square wave signal, that is, signal c﹑d, then the signal d is converted into signal e through the inverter, and finally the two signals are sent to an AND gate to output signal f.

The zero-crossing comparator consists of two LM393s and is used to detect the zero point of two AC signals. When the input signal is greater than zero, the LM393 outputs a high level; when the input signal voltage is less than -5R1/R2, the LM393 outputs a low level.

Calculation method of △T: Calculate by monitoring the time difference at the zero crossing point of the voltage signal, use the embedded computer system to collect the signal, start the timer timing when the signal is high level, stop timing when it becomes low level, and the timer displays The time is ΔT. Due to the internal resistance of the battery, in addition to the phase difference between the input and output signals, the amplitude will also change, but the internal resistance of the battery is very small, and its influence on the amplitude can be ignored compared with the external 10Ω resistor. Therefore, we think that the amplitudes of the input and output signals of the battery are equal, and normalize the amplitudes. Therefore, we set the signal input to the battery pack as:

y ₁ =cos(ωt)+n ₁ (t) (9)

The signal output from the battery pack is:

y ₂ =cos(ωt+θ)+n ₂ (t) (10)

The zero-crossing comparison method to calculate the phase difference is actually to calculate the time difference between the zero point or the peak value of the two signals. If the time of the zero-crossing point of the input signal of the battery pack is t1, and the zero-crossing time of the output signal of the battery pack is t2, then

△T=|t ₂ -t ₁ | (11)

Let the origin of the coordinates be at t ₁ , then

t ₁ =0 (12)

y ₁ =1-n ₁ (0) (13)

y2=cos(ω△T+θ)+n ₂ (△T) (14)

When crossing zero, y ₁ =y ₂ =0, substituting the expressions of y ₁ and y ₂ into the equation:

cos(ω△T+θ)=1-n ₁ (0)-n ₂ (△T) (15)

θ=arccos[1-n ₁ (0)-n ₂ (△T)]-ω△T (16)

However, there are certain defects in this method, mainly as follows:

(1) All components have tolerances, and the phase difference of input and output signals caused by tolerances will be relatively large. When the battery has a large capacity, the phase difference of input and output signals is very small, so the phase difference caused by tolerances The phase difference may cover the phase difference caused by the internal resistance of the battery.

(2) The sensitivity of the detection data to the change of the detection object is guaranteed by high-speed AD sampling. Because when the variation of the phase difference is very small, the variation of the corresponding time difference △T is also very small, and high-speed AD sampling is necessary to obtain this small variation;

(3) It can be seen from formula (16) that the expression of phase difference contains noise part, and the detection result is very sensitive to random noise.

The present invention uses the differential area method. That is, the area corresponding to the phase difference of the two waveforms is calculated first, and then the phase difference of the two waveforms can be calculated by integrating the area, as shown in Figure 17. The input and output signals are sent to the two high-speed and high-precision differential channels of the single-chip microcomputer. The output after sampling is the amplitude difference between the two signals. During the measurement, one cycle is intensively sampled, and the squares of the differential results of the two channels are accumulated and summed. A measured value A is obtained, which can be approximated as the integral of the square of the absolute value of the difference between the two signals, and the integral of the absolute value of the difference between the two signals is the area to which the phase difference corresponds. The algorithm is as follows:

Let the signal of the input signal battery pack be y1,

y ₁ =cos(ωt)+n ₁ (t) (17)

The output signal of the battery pack is y2,

y ₂ =cos(ωt+θ)+n ₂ (t) (18)

The integral of the square of the absolute value of the difference between the input and output signals is:

${<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="HDA0000458200700000021.png,HDA0000458200700000033.png"\; state="\{\{state\}\}">y</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; d\&omega;t</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 19</span>}<span\; class="notranslate">\; )</span>$

Substitute y ₁ y ₂ into formula (19) to get:

${<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="HDA0000458200700000021.png,HDA0000458200700000033.png"\; state="\{\{state\}\}">y</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; d\&omega;t</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; d\&omega;t</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 20</span>}<span\; class="notranslate">\; )</span>$

Expand formula (20) to get:

$\begin{array}{c}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="HDA0000458200700000021.png,HDA0000458200700000033.png"\; state="\{\{state\}\}">y</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; d\&omega;t</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; d\&omega;t</span>}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; )</span>$

Because there is no correlation between the input and output signals and the noise signal, and the integral of the product of the noise signal and any uncorrelated definite signal is zero, it can be simplified to:

${<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="y"\; filenames="HDA0000458200700000021.png,HDA0000458200700000033.png"\; state="\{\{state\}\}">y</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; d\&omega;t</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; two</span>}<span\; class="notranslate">\; )</span>$

Since the cumulative summation of the squares of the differential results of the two channels obtains a measured value A that can be approximated as the integral of the square of the absolute value of the difference between the two signals, so:

2T-Tcosθ=A (23)

Equation (24) is the phase difference obtained by integrating within one signal cycle. If continuous sampling is performed and integrated within N cycles, the result is the cumulative value of the phase difference. This method compares the phase detection results with the zero-crossing comparison method Data can be zoomed in. At the same time, the measurement result does not contain noise, which effectively eliminates the error caused by signal noise.

Although the amplification of the phase detection result data makes the phase difference caused by the component tolerance relatively reduced, and the sensitivity of the measurement result to the tolerance of the circuit components is greatly reduced, but the above methods cannot fundamentally eliminate the component tolerance caused by the detection circuit. measurement results. For example, if the voltage dividing resistor is 10Ω copper resistor, according to the national standard IEC60028-1925, the error is ±1%, that is, ±0.1Ω, and the internal resistance of the battery is milliohm level. There are many electronic components in the detection circuit, the influence of these components will be directly reflected in the measurement results, so it is impossible to distinguish whether the change of the phase difference is caused by the change of the internal resistance of the battery or the tolerance of the components, so each detection system There must be a zero-point drift of the test results, and this zero-point drift is far greater than the internal resistance of the battery, and of course it is far greater than the change in internal resistance that needs to be detected.

The main task of the present invention is to monitor the degree of deterioration of the storage battery during use. As long as the monitoring system can effectively reflect the capacity of the storage battery, and combine the detected temperature and cell voltage as a correction parameter, the current value of each single cell can be effectively given. capacity percentage. The measurement result A of the single-chip microcomputer is an approximation of the phase difference area, but based on the method of statistical look-up table, only one corresponding value is needed, and the phase difference does not need to be accurately calculated. Let the functional relationship between capacity and internal resistance be:

C=f(x) (25)

f(x) is a single-valued continuous monotonically decreasing function. Assume that the relationship between the internal resistance and the phase difference function is:

R=g(x) (26)

g(x) is a single-valued continuous monotonically decreasing function, then the functional relationship between capacity and phase difference can be set as:

C=h(x) (27)

C=h(x) is a single-valued continuous monotonically increasing function. Therefore, the mapping relationship between the measured value A and the battery capacity is that the larger the value of A, the larger the capacity.

Based on this idea, the method adopted in the present invention is to first fully charge the battery, measure the phase difference data result at this time, obtain a data a0, and then measure a data result a1 of 3% of the discharge capacity, and then obtain a data result a0, a1, a2, a3,.... Get a data point b1 from a0-a1, get b2 from a0-a2, and then get: b1, b2, b3,.... Therefore, b1, b2, b3, ... This group of data is the data of the phase difference change that decreases by 3% relative to the 100% capacity during the operation of the battery, which effectively eliminates the zero point drift caused by component tolerances. Assuming that the phase difference caused by the tolerance in the input and output signals is φ1 and φ2 respectively, the expression of the phase difference contains Δφ, and the Δφ obtained by each measurement is the same, which can be offset during the subtraction process. Therefore, this method effectively eliminates the zero drift caused by component tolerances, and can effectively detect the health status of the battery.

According to theoretical research, the system has carried out the following two kinds of experiments: laboratory simulation experiment and field online operation experiment.

(1) Laboratory simulation experiment

The experiment uses a 220V DC system, which consists of 18 batteries. The nominal voltage of the batteries is 12V, and the capacity varies from old to new.

Among the 18 batteries, the data of 4 typical batteries were selected for analysis. The four batteries are an old 200Ah battery, a 100Ah battery on the verge of scrapping, a 100Ah scrapped battery, and a brand new 100Ah battery.

Table 1 shows the voltage data before and after the offline instantaneous discharge experiment after the battery is fully charged, and the instantaneous discharge current is 4.8A.

Table 1 offline experimental data:

Battery U0/V U1/V ΔU/V R/mΩ 1 (100Ah) on the verge of scrapping 13.074 12.151 0.923 192 2 (200Ah) old 10.521 10.216 0.305 64 3 (100Ah) scrapped 12.779 11.644 1.135 236 4 (100Ah) brand new 12.934 12.587 0.347 72

It can be seen from Table 1 that according to the calculated internal resistance, the 100Ah No. 1, No. 2 and No. 4 batteries reflect the capacity well, and the No. 2 battery has a small calculated internal resistance due to its large capacity.

Table 2 shows the voltage data after the online instantaneous discharge experiment after the battery is fully charged and the charger and load are connected.

Table 2 online experimental data:

Battery U2/V ΔU/V R/mΩ 1 (100Ah) on the verge of scrapping 12.197 0.877 183 2 (200Ah) old 10.226 0.295 61 3 (100Ah) scrapped 11.684 1.095 228 4 (100Ah) brand new 12.649 0.285 59

It can be seen from Table 2 that the internal resistance of the battery does not change much, because the battery itself is fully charged, and the battery capacity will not change greatly under the float charge state, so the internal resistance is almost unchanged.

Table 3 and Table 4 are the relevant data obtained by using the instantaneous discharge method when the battery is discharged offline at a current of 10A for 12 minutes, respectively, without and without a charger.

Table 3 The results of the offline comparison experiment:

Battery U0/V U1/V ΔU/V R/mΩ 1 (100Ah) on the verge of scrapping 12.474 12.024 0.450 93

2 (200Ah) old 10.449 10.147 0.352 73 3 (100Ah) scrapped 12.670 11.582 1.088 227 4 (100Ah) brand new 12.901 12.532 0.369 77

Table 4 The results of the online comparison experiment:

Battery U2/V ΔU/V R/mΩ 1 (100Ah) on the verge of scrapping 12.138 0.336 70 2 (200Ah) old 10.165 0.334 69 3 (100Ah) scrapped 11.594 1.076 224 4 (100Ah) brand new 12.547 0.354 74

It can be seen from Table 3 and Table 4 that for each battery, after 12 minutes of discharge, the capacity drops by 2Ah. The purpose of this is to simulate whether the change of battery capacity in a small range can be reflected by the internal resistance. Comparing the data in Table 1-4, we can get the following rules: batteries No. 1 and No. 3 are discarded batteries, and their capacity is already very small. When they are discharged offline for a period of time, their own voltage drops very quickly, and the voltage of the batteries can be judged. Performance, the internal resistance data obtained under this condition does not have relevant laws; although the No. 2 battery is an old battery with a large capacity, the capacity change of 2Ah can also be reflected by the internal resistance change; the No. 4 battery is a brand new battery , is the main object of this comparison experiment, and Table 5 shows the test data of the No. 4 battery with different capacities.

Table 54 battery internal resistance and capacity comparison:

Capacity/Ah U1/V U2/V IS R/mΩ 100 12.522 12.679 5.31 29.56 98 12.331 12.496 5.31 31.07 90 12.054 12.243 5.24 36.07 86 11.987 12.189 5.21 38.77 81 11.897 12.110 5.26 40.49 78 11.862 12.086 5.23 42.83

It can be seen from Table 5 that when the capacity changes a little, the internal resistance change measured by the instantaneous discharge method is very obvious. Through similar repeated experiments, the capacity of the battery was reduced to 80Ah. During this period, the linear change of internal resistance has a good correlation with the capacity (see Figure 4), which can well prove the feasibility of this method. In the actual development of the system, the voltage value in the instantaneous discharge method is used as one of the judgment standards, which ensures the reliability of the system. The actual results show that the battery with low capacity has low voltage during discharge. The capacity obtained by testing the above method meets the requirements of actual production, and is especially suitable for the situation where early detection of changes in battery capacity is required.

(2) On-site online running experiment

The results of this project are applied to multiple substations of a power supply bureau. The test data and experimental conclusions carried out in a substation under the jurisdiction of the power supply bureau are given below.

A substation is a 110kV voltage level substation. The DC system uses 18 batteries. The nominal voltage of the single battery is 12V and the capacity is 100Ah. The initial data of the system test is shown in Table 19:

In the above figure, after the test of this system, the internal resistance of all batteries is less than 50mΩ, and they are in a normal operating state.

In order to test the effect of this system on actually judging the deterioration of the battery, according to the power system substation operation management regulations, after handling the relevant operation tickets, the online running battery is separated from the main system for a short time, and 17 of them are replaced with a faulty battery prepared in advance. No. battery, the faulty battery is an open-circuit faulty battery, unable to store power. After the system is tested by the instantaneous discharge method and the AC phase method, the test data obtained are shown in Table 20:

Through the system test, it is found that the terminal voltage of the 17 connected batteries is normal and slightly higher than the normal battery voltage, but the internal resistance is 988mΩ, which is much higher than the internal resistance of other batteries, which can be clearly identified. The system successfully detected the fault Battery, many existing battery monitoring equipment cannot identify faulty batteries by monitoring the voltage of a single battery.

To sum up, this system has solved the problem of online monitoring of battery performance through the above two types of experiments. The method of combining instantaneous discharge method and AC phase method can accurately measure the internal resistance of the battery, and then determine the capacity of the battery. , so as to judge the performance of the battery.

Claims (5)

1. A substation lead-acid storage battery on-line performance test method is characterized in that, obtains the capacity of each battery cell by the instantaneous discharge method, detects the internal resistance of each battery cell by the AC phase method, and the AC phase method is The instantaneous discharge method correction eliminates the interference to the neighborhood of the open-circuit battery in the instantaneous discharge method, and realizes the real-time online non-destructive testing of the performance of the battery pack. 2. a kind of substation lead-acid storage battery online performance testing method according to claim 1, is characterized in that, Step 1: The battery pack is connected to the charger, and the charger supplies power to the DC load. The battery pack is in the state of floating charging, and the internal resistance of the battery is tested by the instantaneous discharge method; Step 2: The AC small signal generated by the low-frequency AC signal generator is amplified by the coupling drive circuit and then applied to both ends of the battery pack to measure the AC voltage V0 at both ends of the single battery. Due to the existence of the internal impedance of the battery, the output of the battery is AC There is a phase difference between the current waveform and its input waveform, and the internal resistance of the battery is calculated by measuring the phase difference of the input and output voltage waveforms of batteries with different capacities. 3. a kind of substation lead-acid storage battery online performance testing method according to claim 2, is characterized in that, in described step 1: storage battery pack comprises a plurality of storage battery monomers, a plurality of storage battery monomers are divided into two groups, each The group uses a high-power resistor as the discharge load, and the controller controls two solid-state relays in time-sharing to complete the instantaneous discharge operation. At the same time, the voltage sensor and current sensor are used to collect the discharge voltage and discharge current of each battery cell before and after discharge. 4. a kind of substation lead-acid storage battery online performance testing method according to claim 2, is characterized in that, in described step 2: produce sine wave signal with signal generator, add on the accumulator group by a direct current blocking capacitance, through The signal of the battery pack is grounded through a grounding resistor and a DC blocking capacitor, and the phase difference of the input and output signals of the battery is measured, and the impedance is calculated according to the phase difference. 5. according to claim 2 or 4 described a kind of substation lead-acid battery online performance test method, it is characterized in that, adopt difference area method to calculate two waveform phase difference.

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