Background
The intelligent power monitoring system is a software and hardware device which uses computer technology, metering protection device and bus technology to perform centralized detection and centralized management on real-time data, switch state and remote control of the power transmission and transformation system. The current intelligent power monitoring system has the characteristics of unit modularization, transmission networking and monitoring graphics.
Although intelligent power monitoring systems have been developed for a long time, there is a limitation in that the monitoring application of each electrical parameter and the switching state parameter is far more than the monitoring application of the environmental parameter. Practical experience shows that equipment faults caused by a backup power supply are also an important factor that the power transmission and transformation network cannot stably run besides the reason of the electric equipment. Monitoring of the backup power supply is also necessary. In domestic and foreign industry application, online monitoring of storage batteries has been a mature example of research and application, but the solutions provided are to install an insulation detection system, a battery inspection system, a voltage monitoring system, an environment monitoring system, a transformer monitoring system and the like respectively, and these systems have the following problems:
1. Each system independently operates to form a monitoring 'island' phenomenon, management cannot be effectively performed, and the effect of safety management cannot be achieved.
2. The multi-system coexistence not only increases investment cost, but also greatly increases later maintenance cost, and equipment of a plurality of factories operates simultaneously, so that a skin tearing site can be generated, and the time and energy of a power supply company are wasted.
3. The device has single function.
4. The networked monitoring device generally only uploads a small amount of important information to the monitoring center, and cannot reflect detailed information of the running state, environmental parameters and the like of the direct current equipment in real time.
5. The discretization of the monitoring data and the judgment of the state mainly depend on manual inspection to find out problems, so that the safe operation of the power grid is affected.
6. The operation and maintenance conditions of the storage battery of the backup power supply are not emphasized, the storage battery pack cannot be guaranteed to operate in a good state, the safe operation of a power grid is affected, various accidents caused by storage battery faults in the power industry also occur sometimes, and even ignition and total station power failure are caused partially, so that great potential safety hazards are brought to the reliable operation of a power system.
7. For a battery on-line monitoring system, on-line monitoring devices of some storage batteries are developed at present, and the device can provide effective technical means for daily maintenance monitoring of the storage batteries and realize various functions such as comprehensive analysis, intelligent management, automatic alarm, network monitoring and the like. However, the device has a single function, can only provide a monitoring function, and cannot evaluate the residual life, the actual capacity and remotely maintain the storage battery. At present, measurement technologies of charge and discharge current, voltage, temperature and the like of a battery pack are basically mature, the main direction of research at present is measurement of internal resistance of a single body, and research on insulation resistance monitoring, on-line equalization of a storage battery and residual life assessment of the storage battery at present is not started at home.
8. For the insulation monitoring device of the direct current system, the currently applied device has single function, can only provide a monitoring function and send out a forenotice signal when the condition is met, cannot monitor insulation reduction, and cannot realize isolation protection and accurately monitor the grounding position.
9. The battery pack does not have the voltage balancing capability, and other batteries are often overcharged or undercharged due to the voltage change of a certain number of batteries in the batteries, so that the conditions of capacity reduction, battery life shortening, electrolyte drying and the like of the batteries are caused, and the operation reliability of the whole system is affected.
Disclosure of Invention
In view of the foregoing, the present invention provides a system that is capable of effectively monitoring and evaluating the state of a battery.
In order to achieve the aim, the invention provides a remote monitoring and performance evaluation system of a storage battery, which is characterized in that a data acquisition module is respectively and independently arranged for each storage battery to be evaluated, each storage battery is provided with a standby storage battery unit, the storage battery and the corresponding standby storage battery unit are connected with a remote discharging module, the data acquisition module and the corresponding remote discharging module are connected with a terminal controller, the terminal controller is connected with a database server and a control center through a communication network, and the control center and the database server exchange data through a network;
the control center evaluates the storage battery according to indexes including the application life and the residual capacity of the storage battery;
the database server is used for storing the acquired data information and providing database service for the control center;
The terminal controller transmits the storage battery data of each station acquired in real time to the database server in a network transmission mode;
The data acquisition module is used for remotely monitoring and acquiring end voltage, battery cell temperature, current, internal resistance of a storage battery, ambient temperature and battery operation state (the states include a normal working state including an equilibrium charge state, a floating charge state and a discharging/power supply state, and the abnormal states include working parameter abnormality under any one of the equilibrium charge state, the floating charge state and the discharging/power supply state, such as overhigh cell voltage, overlow cell voltage and voltage difference between batteries) and bus voltage parameter;
the bus voltage parameters specifically comprise parameters required by the prediction of the capacity and the service life of the DTU battery;
the remote discharging module is used for remotely controlling the corresponding storage battery packs to realize constant-current discharging group by group;
s1, providing a battery capacity prediction function based on the system, comprising the following steps:
S1-1, discretely collected storage battery discharge parameters including discharge proportion (%), discharge capacity (AH), corresponding voltage v, corresponding temperature and discharge current;
S1-2, calculating the values of relevant discharge proportion (%), discharge capacity (AH), corresponding voltage v, corresponding temperature and discharge current by adopting an interpolation method based on the acquired data and taking 5% of the actual capacitance as an interval, and drawing a discharge variable table;
s1-3, predicting the discharged capacity of the battery according to the following formula (1):
Wherein, C (T) represents the predicted discharge capacity of the battery, Vt represents the current voltage of the lowest battery cell in the working parameters of the battery, Vi represents the initial voltage of the interval in which the current voltage Vt in the discharge variable table is located, Vi+1 represents the end voltage of the interval in which the current voltage Vt in the discharge variable table is located, It represents the current discharge current value of the battery, I0 represents the initial discharge current value of the interval in which Vt in the discharge variable table is located, C (I) represents the initial discharge capacity of the interval in which the current voltage Vt in the discharge variable table is located, C (i+1) represents the end discharge capacity of the interval in which the current voltage Vt in the discharge variable table is located, Tt represents the ambient temperature at the current discharge time, T0 represents the ambient temperature at the initial point of the interval in which Vt in the discharge variable table is located, when Vt corresponds to a plurality of intervals, the first interval from the left in the table is taken as reference, and when Vt exceeds the voltage value corresponding to 0%;
s1-4, predicting remaining capacity and actual capacity of the battery
Battery remaining capacity C (left) =c (total) -C (t) formula (2)
Battery actual capacity c=c (left) +c (actual) formula (3)
Wherein, C (total) represents the actual capacity of the storage battery recorded when the discharge variable table is established, C (left) represents the residual capacity of the storage battery calculated according to the current state, C (actual) represents the actual discharge capacity of the storage battery collected by the controller, and C represents the actual capacity of the storage battery in the current state, wherein in step S1-4, after Vt is lower than the voltage value corresponding to the change of the storage battery capacity from the left side of the table, C (t) is calculated according to the discharge amount reported by the controller, namely C (t) =c (actual);
S2, providing a battery remaining life prediction function based on the system, comprising the following steps:
When the discharge quantity of the storage battery is not less than 30% of the rated capacity of the storage battery, after the discharge of the storage battery is finished, according to the working parameters when the discharge state is acquired in the last discrete mode, the working parameters comprise the values of discharge proportion (%), discharge capacity (AH), corresponding voltage v, corresponding temperature and discharge current, and the service life is calculated:
Or (b)
Y (t) =10-Y (i) formula (5)
Wherein Y (t) represents the calculated remaining life of the storage battery, a smaller value is obtained from the calculation result of the formula (4) and the calculation result of the formula (5), and Y (i) represents the known working time of the storage battery;
where k represents an aging coefficient, y=a known working period-1;
In a preferred mode, when the data acquisition module monitors that the internal resistance value of a certain single storage battery pack exceeds a set threshold value, the control center automatically alarms and prompts through the terminal controller;
The internal resistance is measured by adopting two methods, namely an alternating current method or a direct current method;
The AC method is to generate AC voltage with fixed frequency by an AC signal generator, measure the current of the signal passing through the storage battery, calculate the ratio of the voltage to the current to obtain a resistance value, and the DC method is to discharge the storage battery under different current conditions, measure the voltage value during discharge and calculate the ratio of the voltage difference to the current difference to obtain the resistance value.
Under the preferred mode, the actual capacity of the battery is comprehensively evaluated based on the predicted actual capacity of the battery and the internal resistance comparison standard of the battery, and the accurate actual capacity of the battery can be obtained by adopting the following modes:
In the practical engineering application, the practical internal resistance of the storage battery is respectively compared with the internal resistance of the new batteries in the same batch in a mode 1, or the average internal resistance of the storage battery in the same group is compared in a mode 2, or the internal resistance is compared with the internal resistance test value of the last time per se in a mode 3;
The method 1 is that the production elements of the same batch of batteries are basically the same, so the internal resistance is basically close, when the internal resistance of a specific storage battery is higher than the internal resistance of a new battery, the capacity is reduced, and the actual test is needed;
The mode 2 is that the same group of batteries are completely identical in use environment and basically identical in internal resistance, when the internal resistance of a specific storage battery is higher than the average internal resistance of the same group, the capacity is reduced, and when the internal resistance is higher than the average internal resistance by 30%, close attention is needed, and when the internal resistance is higher than 100%, replacement is considered to be needed;
And 3, comparing the relation between the internal resistance of the storage battery and the actual residual capacity of the storage battery, wherein when the actual residual capacity of the storage battery is 100% -70% of the nominal value, the corresponding relation between the capacity decrease and the internal resistance increase is not obvious, and when the actual residual capacity of the storage battery is less than 25% of the nominal value, the internal resistance increase trend is gradually accelerated.
The discharge variable table records the actual measured values of the corresponding discharge capacity, the corresponding voltage, the corresponding temperature and the discharge current from zero percent to five percent of the discharge proportion to hundred percent of the discharge proportion.
The intelligent monitoring system has the beneficial effects that the system adopts the internet of things technology and the intelligent sensor technology to remotely monitor and collect parameters such as the terminal voltage of the storage battery pack, the voltage of the battery cell, the temperature of the battery cell, the current, the ambient temperature, the running state of the battery and the bus voltage in real time. And uploading the acquired data to central management platform software for analysis and storage in real time through a network so as to monitor the real-time operation environment of the operation parameters of the direct-current equipment of the transformer substation. Meanwhile, the system calculates the residual life and actual capacity assessment of the battery according to the data monitored in real time, and provides scientific and reasonable basis for the replacement plan of the storage battery.
Detailed Description
As shown in figure 1, the remote monitoring and performance evaluation system of the storage battery comprises a data acquisition module, a standby storage battery unit, a remote discharging module, a terminal controller, a database server and a control center, wherein the data acquisition module is respectively and independently arranged for each storage battery to be evaluated, the standby storage battery unit is arranged for each storage battery, the storage battery and the corresponding standby storage battery unit are connected with the remote discharging module, the data acquisition module and the corresponding remote discharging module are connected with the terminal controller, the terminal controller is connected with the database server and the control center through a communication network, and the control center and the database server interact data through the network. Wherein,
1. And a control center. The system provides an effective technical means for daily maintenance, monitoring and maintenance of direct current equipment, and realizes various advanced functions such as remote maintenance, comprehensive analysis, intelligent management, automatic alarm, network monitoring and the like. Meanwhile, various operation and maintenance parameters of the storage battery are researched from multiple angles, and an evaluation system of the storage battery is provided, and the storage battery is evaluated, distinguished and screened according to main indexes such as the service life, the residual capacity and the like of the storage battery by using the system.
2. And a database server. The system is used for storing the acquired data information and providing database services for the control center.
3. And a terminal controller. And transmitting the storage battery data of each station acquired by the system in real time to a database server through various network transmission modes. The comprehensive analysis processing of the uploaded power environment data of each site is completed through the control center, the operation parameters and the operation states of the direct current equipment of each site are automatically displayed and analyzed, and the functions of remote maintenance, comprehensive analysis, intelligent management, automatic alarm, network monitoring and the like are realized.
4. And a data acquisition module.
(1) And the real-time monitoring function is to remotely monitor and collect parameters such as end voltage, battery cell temperature, current, environment temperature, battery running state, bus voltage and the like of the storage battery pack in real time.
(2) The storage battery internal resistance monitoring function is that on the basis of the on-line conventional monitoring of the storage battery pack, an advanced on-line internal resistance testing technology is adopted, so that the internal resistance of each storage battery can be tested on line, the performance state of the storage battery can be timely and accurately known, and a fault monomer can be found. And the real-time warning function is that the system automatically warns and prompts when the internal resistance value of a certain monomer exceeds a set threshold value. The normal operation of the system is not affected in the test process. The module is composed of various sensors and is used for collecting end voltage of a storage battery pack, voltage of a battery cell, temperature of the battery cell, current, ambient temperature, battery running state, bus voltage and internal resistance of the storage battery. Except for the internal resistance test, the internal resistance test is monitored in real time through a sensor, so that the internal resistance test is called conventional measurement. The internal resistance test cannot be directly obtained through a sensor, and two methods in the module are used for realizing the measurement of the internal resistance, namely an alternating current method and a direct current method. The AC method is to generate an AC voltage with a fixed frequency (different frequencies of the AC signal generator) by the AC signal generator, measure the current of the signal passing through the storage battery, calculate the ratio of the voltage to the current to obtain a resistance value, and the DC method is to discharge the storage battery under different current conditions (different industry standards have specific regulations on the discharge current), measure the voltage value during discharge and calculate the ratio of the voltage difference to the current difference to obtain the resistance value. The AC method is simple in measurement, can be used for measuring at any time by controlling an AC signal generator and can be monitored in real time, and the DC method is not real-time because the DC method can be used for measuring only when the storage battery is controlled to discharge.
5. And a remote discharging module. The remote control storage battery pack realizes 'on-line' constant current discharge group by group. In the discharging process, the tested storage battery pack does not need to be separated from the system, keeps real-time on-line, and maximally ensures the residual capacity of the backup battery pack of the system so as to achieve the aim of testing the safe discharge capacity. After the discharging is finished, the system can carry out online charging recovery on the storage battery. The whole checkup discharging process is automatically completed, no staff is required to go to the site to operate in the discharging process, no personnel is required to watch, the related results are automatically recorded by a system background, the labor cost is greatly saved, and the labor efficiency is improved.
And the residual life prediction function of the storage battery calculates the capacity decay ratio of the battery according to the discharge capacity of the battery to obtain the current aging coefficient of the storage battery, and a large number of storage battery tests show that the aging model of the battery is similar to a battery discharge curve, the aging coefficient of a new battery is 1, and the aging coefficient of the new battery is 0 when the service life is ended.
The invention adopts curve fitting and piecewise linear interpolation method to comprehensively evaluate the actual capacity of the battery according to self-learning discharge curve method and low-current internal resistance test method, and the comprehensive formula of the fitting curve and piecewise difference is as follows:
In the formula, C (T) represents the predicted discharge capacity of the battery according to the measured working parameters of the battery after the battery starts to discharge, vt represents the current voltage of the lowest battery cell in the measured working parameters of the battery after the battery discharges, vi represents the initial voltage of the section where the current voltage Vt is located in the discharge variable table, vi+1 represents the final voltage of the section where the current voltage Vt is located in the discharge variable table, it represents the current discharge current value of the battery, I0 represents the discharge current value of the initial point of the section where the Vt is located in the discharge variable table, C (I) represents the initial discharge capacity of the section where the current voltage Vt is located in the discharge variable table, C (j) represents the final discharge capacity of the section where the current voltage Vt is located in the discharge variable table, tt 0 represents the ambient temperature at the current discharge time, and T0 represents the ambient temperature at the initial point of the section where the Vt is located in the discharge variable table, and the standard is comprehensively evaluated according to the predicted actual capacity of the battery and the internal resistance ratio, so that the accurate actual capacity of the battery can be obtained. The battery internal resistance comparison standard adopts the following mode that in the practical engineering application, the practical internal resistance of the storage battery is respectively compared with the internal resistance of a new battery in the same batch (note 1), or the average internal resistance of the storage battery in the same group is compared (note 2), or the internal resistance is compared with the internal resistance test value of the last time per se (note 3). And 1, the production elements of the same batch of batteries are basically the same, so the internal resistance is basically close. When the internal resistance of a specific battery is higher than the internal resistance of a new battery, this means a capacity drop. However, the capacity drop and the internal resistance rise are not functionally related, and an actual test is required. And 2, the same group of batteries have the same internal resistance because the use environments are completely the same. When the internal resistance of a specific storage battery is higher than the average internal resistance of the same group, the capacity is reduced. In general, the internal resistance is 30% higher than the average internal resistance, namely close attention is paid, and more than 100% is considered to be replaced. However, the capacity reduction cannot be directly reflected by only comparing the specific internal resistance of a certain battery with the average value deviation. Note 3 that, in general, when the actual remaining capacity of the battery is about 100% -70% of the nominal value, the corresponding relation between the capacity drop and the internal resistance rise is not obvious. When the actual residual capacity of the storage battery is less than 25% of the nominal value, the internal resistance rising trend is gradually accelerated.
Based on the above principle, specific predicted contents are explained below:
1. Definition of battery capacity and life
First, capacity
The capacity of the battery is the amount of electricity that can be obtained from the battery under a certain discharge condition, and is denoted by symbol C. The usual unit is ampere-hours, simply ampere-hours (A.H). The capacity of the secondary battery can be classified into a rated capacity, an actual capacity, and a remaining capacity.
1. Rated capacity
Rated capacity is the ampere-hour power indicated by the manufacturer that can be provided after the battery is fully charged under prescribed conditions. A fully charged battery is typically used to continuously discharge current (corresponding to 1/20 of rated capacity) at a rate of 20 hours to a level of 1.75V per cell at an average electrolyte temperature of 25 ℃. Typically the nominal capacity of the battery.
2. Actual capacity
The actual capacity is the maximum electric quantity which can be actually output under a certain condition after the storage battery is fully charged.
3. Residual capacity
The remaining capacity is the difference between the actual capacity of the battery and the discharged power.
(II) lifetime
1. Design life of accumulator
The battery design life is generally referred to as the service life, that is, the calendar time from the use of a new battery or the time when the actual capacity of the battery drops to 80% of rated capacity after rest. Typically 10 years.
2. Residual life of accumulator
The remaining life of a battery is typically the difference between the design life of the battery and the operating time of the battery.
2. Method for calculating capacity of storage battery
1. Calculation conditions
In the discharging state, the current working voltage (Vt), the ambient temperature (Tt) and the discharging current (It) are used as calculation bases, the residual capacity (Ct) of the old battery is calculated according to an interpolation method, after each new battery working parameter is uploaded, the discharge capacity (Ct) of the battery is calculated, and the residual capacity (Cleft) of the battery is calculated.
The discharge capacity (Ct) of the battery calculated from the battery having the lowest operating voltage (Vt) in the battery should be used as a basis for calculating the remaining capacity (Cleft) of the battery.
2. Calculation method
According to the current working voltage of the storage battery, calculating by adopting an interpolation method based on a pre-recorded storage battery discharging curve. In particular, 21 reference points are recorded in advance according to the discharge curve of the storage battery at intervals of 5% of the actual capacitance, see fig. 2.
(1) Firstly, the discharged capacity of the battery is predicted according to the working parameters of the battery, and the calculation formula is as follows:
In equation (1), the parameters are described as follows, C (t) represents the predicted discharged capacity of the battery based on the measured operating parameters of the battery after the battery begins to discharge. Vt represents the current voltage Vi of the lowest battery cell in the measured battery pack operating parameters after the battery is discharged, and represents the starting voltage of the interval where the current voltage Vt in the discharge variable table is located. Vi+1 denotes the end voltage of the interval in which the current voltage Vt is located in the discharge variable table. It represents the current discharge current value of the battery pack. I0 represents the discharge current value at the start point of the interval where Vt is located in the discharge variable table. C (i) represents the initial discharge capacity of the section of the discharge variable table where the current voltage Vt is located. C (i+1) represents the termination discharge capacity of the section of the discharge variable table where the current voltage Vt is located. Tt denotes the ambient temperature at the time of the current discharge. T0 represents the ambient temperature at the beginning of the interval where Vt is located in the discharge variable table. When Vt corresponds to multiple intervals, the first interval from the left in the table is taken as the reference. When Vt exceeds the voltage value corresponding to 0% of discharge proportion, C (t) takes on the value of 0.
Calculation example 1. The operating voltage Vt of the battery was measured at a certain point in time to be 2.005V, the discharge current It was 39.9A, and the ambient temperature Tt was 32.3 ℃. Then it can be obtained by the formula (1)
Calculation example 2. The operating voltage Vt of the battery was measured at a certain time to be 2.182V, the discharge current It was 39.9A, and the ambient temperature Tt was 32.3 ℃, C (t) =0 because Vt is greater than 2.126V.
(2) Predicting remaining and actual battery capacity
Battery remaining capacity C (left) =c (total) -C (t)
Battery actual capacity c=c (left) +c (actual)
And C (total), the actual capacity of the storage battery recorded in the process of building the table, namely the rightmost value of the discharge capacity column in the discharge variable table in fig. 2. And C (t) calculating the discharge capacity of the storage battery according to the current state by adopting the formula (1). And C (left), namely the residual capacity of the storage battery calculated according to the current state is the difference between C (total) and C (t). And C (actual) the actual discharge capacity of the storage battery acquired by the controller. And C, calculating the actual capacity of the storage battery in the current state, wherein the actual capacity is the sum of C (left) and C (actual).
Calculation example 3 the operating voltage Vt of the battery was measured at a certain time to be 2.005V, the discharge current It was 39.9A, the ambient temperature Tt was 32.3C, and the discharged electric quantity was 100AH. Then C (t) =128.1 AH can be obtained by formula (1), where C (total) is 400AH and C (actual) is 100AH. And (3) calculating:
battery remaining capacity C (left) =400-128.1= 271.9AH
Actual capacity c=271.9+100= 371.9AH
(3) If the pre-stored discharge variable table is in the format of fig. 3, after Vt is lower than the voltage value corresponding to the change of the battery capacity from the left side of the table, C (t), i.e., C (t) =c (actual), is calculated according to the discharge amount reported by the controller.
3. Method for calculating remaining life of storage battery
When the discharge quantity of the storage battery is not less than 30% of the rated capacity of the storage battery, after the discharge of the storage battery is finished, calculating the residual life of the storage battery according to the working parameters acquired in the discharge state for the last time.
And Y (t), taking the calculated result of the formula (4) and the smaller value of the calculated result of the formula (5) as the calculated remaining life of the storage battery. Y (i) known operating time of battery
K is the ageing coefficient of the glass fiber reinforced plastic film,
Where y = known operational age-1.
Calculation example 4 the battery, which had been operated for 5 years, was measured at a certain time to have an operating voltage Vt of 1.989V at the time of stopping discharging, a discharge current It of 39.9A, an ambient temperature Tt of 32.3C, and a discharged electric quantity of 160AH. Then C (t) = 192.8AH can be obtained by formula (1), and when C (total) is 400AH and C (actual) is 160AH, the actual capacity c=400-192.8+160=367.2 AH of the battery is obtained.
Obtained according to the formula (4)
Y (t) =10-5=5 years according to formula (5), and the final value of Y (t) is 5 years.
4. Discharge variable meter
1. Discharge variable table update standard
(1) When the storage battery pack has no discharge record, the discharge variable table is a default discharge variable table of the system.
(2) When the discharge capacity of the storage battery exceeds 95% of the capacity of the storage battery, corresponding data in the discharge variable table is updated after the discharge is finished.
(3) Method for updating discharge variable table
When the discharge capacity of the storage battery is not less than 95% (complete discharge), the corresponding voltage, current and temperature data corresponding to the discharge percentage position in the discharge variable table are updated according to the measured data, and the discharge capacity data are updated according to calculation, wherein the data of 100% discharge are based on the data acquired last (the discharge electric quantity value at 5% intervals is accurate to 1 bit after the decimal point when the battery capacity is more than or equal to 100AH, and is less than or equal to 50AH when the battery capacity is less than or equal to 100AH, and is accurate to 2 bits after the decimal point when the battery capacity is less than 50AH, and the rest is rounded. The updated example is that after the battery with a rated capacity of 400AH discharges 369AH for the first time, the discharge is stopped because the voltage reaches 1.8V discharge cut-off voltage, and the last collected working voltage Vt before the discharge is stopped is 1.801V.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should be covered by the protection scope of the present invention by making equivalents and modifications to the technical solution and the inventive concept thereof.