Photovoltaic-based retired battery energy storage control system

Abstract

According to the photovoltaic-based retired battery energy storage control system provided by the invention, the photovoltaic cell panel is arranged in the energy storage system, and the charging power supply is determined according to the high power consumption, the flat peak period and the output of the photovoltaic cell when the retired battery is charged, so that the diversity of the charging power supply is ensured, and certain use cost can be saved; and a switching control circuit is arranged in the system, sequential charging is performed according to the charge state and the voltage of the decommissioned battery, and the battery in the low charge state can exit discharging during discharging, so that the unbalance of charging and discharging is prevented, the service life of the decommissioned battery is ensured, and the potential safety hazard caused by the unbalance of charging and discharging is eliminated.

Description

Technical Field

[0001] The present invention relates to a retired battery energy storage control system, and in particular to a retired battery energy storage control system based on photovoltaics. Background Art

[0002] With the increasing popularity of electric vehicles, power battery packs, as one of the core components of electric vehicles, are also being used more and more. When the power battery packs reach certain conditions, they cannot meet the needs of electric vehicles, thus forming retired batteries. Although the retired batteries cannot meet the power needs of electric vehicles, they can still be used in other scenarios, such as as energy storage power sources.

[0003] Retired batteries have been widely used as energy storage power sources, but the existing energy storage power sources based on retired batteries have the following defects: on the one hand, the existing energy storage power sources based on retired batteries have a single charging option, and are generally charged based on municipal electricity. When the municipal electricity is at its peak price, the electricity price is relatively expensive, resulting in high cost of use. In addition, the municipal power grid has a certain degree of volatility during peak hours compared to off-peak hours, and there are certain hidden dangers in electricity use, such as fluctuation shocks.

[0004] A more important aspect is that when retired batteries are used as energy storage power sources, they often cannot be used independently. Instead, multiple retired batteries with the same specifications, that is, the same capacity, the same output power, the same output current and the same output voltage, form an energy storage system, and then the energy storage system is used as a whole for charging or discharging. However, because they are retired batteries, their working state stability is poor, and they are prone to charge and discharge imbalance, which poses a safety hazard.

[0005] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a photovoltaic-based retired battery energy storage control system, in which photovoltaic panels are arranged in the energy storage system, and when charging the retired batteries, the charging power source is determined according to the peak and off-peak periods and the output of the photovoltaic cells, so as to ensure the diversity of the charging power source and save a certain amount of use cost. In addition, a switching control circuit is arranged in the system to sequentially charge the retired batteries according to the charge state and voltage of the retired batteries, so that the batteries with low charge state can exit discharge during discharge, thereby preventing the imbalance of charge and discharge, ensuring the service life of the retired batteries, and eliminating the safety hazards caused by the imbalance of charge and discharge.

[0007] The present invention provides a photovoltaic-based retired battery energy storage control system, comprising a retired battery module, a photovoltaic panel, a photovoltaic controller, a single-pole three-throw relay, a switching control circuit, a control unit, a DC-DC conversion circuit and an output port;

[0008] There are multiple retired battery modules, and each retired battery module has a battery management unit, the battery management unit is used to obtain the operating information of the retired battery module and transmit it to the control input end of the control unit, the switching control circuit has an input end and an output end, the input end of the switching control circuit is connected to the moving contact of the single-pole three-throw relay, the output end of the switching control circuit is connected to the input end of the DC-DC conversion circuit, the output end of the DC-DC conversion circuit is connected to the output port, the output port supplies power to the DC power device, the control unit has a switching control output end and a conversion control output end, the switching control output end of the control unit is connected to the switching control circuit The control input end of the control unit is connected to the control input end of the DC-DC conversion circuit; the first static contact of the single-pole three-throw relay is connected to the output end of the photovoltaic controller, the input end of the photovoltaic controller is connected to the photovoltaic battery panel, the photovoltaic controller is also communicatively connected to the control unit, the second static contact of the single-pole three-throw relay is connected to the power grid charging output port, the third static contact of the single-pole three-throw relay is suspended, the control input end of the single-pole three-throw relay is connected to the control unit, and the control unit controls the action of the single-pole three-throw relay according to the photovoltaic power generation information uploaded by the current photovoltaic controller and whether the current charging time node is a peak period.

[0009] Further, the control unit controls the single-pole three-throw relay action according to the photovoltaic power generation information uploaded by the current photovoltaic controller and whether the current charging time node is a peak period, specifically including:

[0010] SA1. The control unit obtains the current state of charge information of the retired battery through the battery management unit and determines whether the retired battery needs to be charged. If so, it enters SA2, if not, it stops;

[0011] SA2. The control unit obtains the current output current of the photovoltaic panel from the photovoltaic controller. When the output current of the photovoltaic panel is less than the set threshold, the process proceeds to step SA3. If not, the process proceeds to step SA6.

[0012] SA3 control unit determines whether the current time is the peak period of electricity prices or the flat period of electricity prices. If it is the peak period of electricity prices, it proceeds to step SA4. If it is the flat period of electricity prices, it proceeds to step SA5.

[0013] SA4. The control unit obtains the historical discharge times of the energy storage system in the period corresponding to the current time in the historical data. When the historical discharge times are greater than the set value, the control unit controls the moving contact of the single-pole three-throw relay to be turned on with the second static contact, and the grid charges the retired battery. If not, the energy storage system is charged when the electricity price is off-peak or the output current of the photovoltaic panel is greater than the set value;

[0014] SA5. The control unit controls the moving contact of the single-pole three-throw relay to be turned on with the second static contact, and the retired battery is charged by the power grid;

[0015] SA6. The control unit controls the moving contact of the single-pole three-throw relay to be connected with the first static contact, and the photovoltaic panel charges the retired battery.

[0016] Further, the switching control circuit includes a series electronic switch group and a charge and discharge electronic switch group;

[0017] The series electronic switch group includes m-1 electronic switches and is respectively arranged between the positive and negative electrodes of adjacent retired battery modules and connects the adjacent retired battery modules in series; the adjacent here means that the positive and negative electrodes of the two retired battery modules are adjacent; m represents the total number of retired battery modules;

[0018] The charging and discharging electronic switch group includes a plurality of electronic switches, the positive electrode of each retired battery module is connected to the charging DC bus through an electronic switch, the negative electrode of the retired battery module at the end of the series connection is connected to the negative electrode of the charging output port through an electronic switch, and the charging DC bus is connected to the positive electrode of the charging output port of the battery management unit through the charging master switch QZ1; the charging DC bus is connected to the negative electrode of the input end of the DC-DC conversion circuit through an electronic switch;

[0019] The positive electrode of each retired battery module is connected to the discharge DC bus through an electronic switch, and the discharge DC bus is connected to the positive electrode of the input end of the DC-DC conversion circuit through the discharge master switch QZ2. The negative electrode of the retired battery module at the end of the series connection is connected to the negative electrode of the input end of the DC-DC conversion circuit through an electronic switch; the discharge DC bus is connected to the negative electrode of the charging output port through an electronic switch;

[0020] The control input ends of the electronic switches of the series electronic switch group and the charge-discharge electronic switch group are connected to the control unit.

[0021] Further, the control unit switches the control circuit to perform charging operation in the following manner:

[0022] SB1. The control unit initializes the status information of each retired battery module, the status information includes the current state of charge SOC and voltage of each retired battery module; and the control unit controls the main discharge switch QZ2 to always be in the off state;

[0023] SB2. The control unit sorts the retired battery modules according to the state of charge SOC from small to large, and determines the charging priority of each retired battery module, where the smaller the state of charge SOC, the higher the charging priority;

[0024] SB3. The control unit first controls the electronic switch corresponding to the retired battery module with the smallest state of charge SOC to turn on and the retired battery module enters the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the smallest state of charge SOC reaches the battery voltage with the second smallest state of charge SOC among the retired battery modules, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to turn on, and so on, until all retired battery modules enter the charging state.

[0025] Further, the control unit switches the control circuit to perform the discharge operation in the following manner:

[0026] SC1. The control unit obtains the state of charge SOC and voltage of each retired battery module at the initial discharge from the battery management unit, and the control unit controls the charging main switch QZ1 to always be in the off state;

[0027] SC2. After the set discharge time, the control unit obtains the state of charge SOC and voltage of each retired battery module from the battery management unit again. When the difference between the current state of charge SOC value of any retired battery module and the average state of charge value of all retired battery modules at the current moment is greater than the set value, or when the difference between the current voltage value of any retired battery module and the average voltage value of all retired battery modules is greater than the set value, the control unit controls the electronic switch corresponding to the current retired battery module to turn off, and the electronic switches corresponding to other retired battery modules are turned on and are in the discharge state. At the same time, the control unit adjusts the duty cycle of the PWM signal output to the DC-DC conversion circuit so that the power of the DC-DC conversion circuit maintains the rated power of the electrical device;

[0028] SC3. Return to step SC2 until the set discharge time is reached or the power provided by the remaining retired battery modules cannot meet the needs of the electrical devices.

[0029] Furthermore, the control unit performs fault warning according to the consistency of the state of charge and the voltage of each retired battery module:

[0030] Among them, the charge state consistency is:

[0031] Among them, CON SOC is the charge state consistency, η SOC is the rate of change of state of charge, is the average rate of change of state of charge of all retired battery modules, SOC0 is the state of charge value of the retired battery module at the initial discharge time after charging, and SOC1 is the state of charge value of the retired battery module after the set discharge time;

[0032] The voltage consistency is:

[0033]

[0034] Among them: CON V is the voltage consistency, η V is the voltage change rate, is the average voltage change rate of all retired battery modules, V0 is the voltage value of the retired battery module at the initial discharge time after charging, and V1 is the voltage value of the retired battery module after the set discharge time;

[0035] When any retired battery module has a charge state consistency value greater than a set value or a voltage consistency value greater than a set value during N consecutive discharges, the control unit issues a fault alarm through the alarm connected thereto.

[0036] Furthermore, the electronic switch is a MOS tube.

[0037] Furthermore, the energy storage system further includes a battery status control unit;

[0038] The battery state control unit includes a temperature sensor, a humidity sensor, a battery cooling module and an environment adjustment module;

[0039] The temperature sensors are in two groups, one of which is used to obtain the operating temperature of each retired battery module, and the other is used to obtain the ambient temperature of the environment where the energy storage system is located. The output ends of the temperature sensors and humidity sensors are connected to the control unit, and the control input ends of the battery cooling module and the environment adjustment module are connected to the control unit. The battery cooling module is used to receive the control command of the control unit to cool the retired battery module when the temperature of the retired battery module is higher than the set value, and the environment adjustment module is used to receive the control command of the control unit to adjust the ambient temperature and humidity of the environment where the energy storage system is located when the temperature of the environment is higher than the set value or the humidity is higher than the set value.

[0040] Furthermore, the DC-DC conversion circuit includes a switching power supply circuit and a rectifier filter circuit, the input end of the switching power supply circuit is connected to the discharge output end of the switching control circuit, the output end of the switching power supply circuit is connected to the input end of the rectifier filter circuit, the output end of the rectifier filter circuit is connected to the output port, and the control input end of the switching power supply circuit is connected to the control unit.

[0041] Beneficial effects of the present invention: Through the present invention, photovoltaic panels are arranged in the energy storage system, and when charging retired batteries, the charging power source is determined according to the peak and off-peak periods and the output of the photovoltaic cells, thereby ensuring the diversity of the charging power source and saving a certain amount of use cost. In addition, a switching control circuit is arranged in the system, and sequential charging is performed according to the charge state and voltage of the retired batteries. During discharge, the batteries with a low charge state can be stopped from discharging, thereby preventing the imbalance of charge and discharge, ensuring the service life of the retired batteries, and eliminating the potential safety hazards caused by the imbalance of charge and discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0043] Figure 1 It is a structural schematic diagram of the present invention.

[0044] Figure 2 It is a schematic diagram of the switching control circuit of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below:

[0046] The present invention provides a photovoltaic-based retired battery energy storage control system, comprising a retired battery module, a photovoltaic panel, a photovoltaic controller, a single-pole three-throw relay, a switching control circuit, a control unit, a DC-DC conversion circuit and an output port;

[0047] There are multiple retired battery modules, and each retired battery module has a battery management unit, the battery management unit is used to obtain the operating information of the retired battery module and transmit it to the control input end of the control unit, the switching control circuit has an input end and an output end, the input end of the switching control circuit is connected to the moving contact of the single-pole three-throw relay, the output end of the switching control circuit is connected to the input end of the DC-DC conversion circuit, the output end of the DC-DC conversion circuit is connected to the output port, and the output port supplies power to the DC power-consuming equipment, the control unit has a switching control output end and a conversion control output end, the switching control output end of the control unit is connected to the control input end of the switching control circuit, and the conversion control output end of the control unit is connected to the control input end of the DC-DC conversion circuit; the single-pole three-throw relay The first static contact of the single-pole three-throw relay is connected to the output end of the photovoltaic controller, the input end of the photovoltaic controller is connected to the photovoltaic panel, the photovoltaic controller is also communicatively connected to the control unit, the second static contact of the single-pole three-throw relay is connected to the grid charging output port (the grid charging output port refers to a charging circuit set on the grid side, the input end of the circuit is connected to the mains, and the output end is the grid charging output port, wherein the charging circuit is an existing circuit, formed by rectification, filtering, and DC-DC conversion, and its principle and structure are not described in detail here), the third static contact of the single-pole three-throw relay is suspended, the control input end of the single-pole three-throw relay is connected to the control unit, and the control unit controls the action of the single-pole three-throw relay according to the photovoltaic power generation information uploaded by the current photovoltaic controller and whether the current charging time node is a peak period. Among them, the third static contact of the single-pole three-throw relay is suspended, that is, when the retired battery does not need to be charged, the static contact is placed on the third static contact, and the static contact is not connected to anything to prevent false operation. The single-pole three-throw relay is a prior art. Any of the three static contacts can be set to the first, second or third static contact. This is common sense and will not be elaborated here. Among them, the battery management unit can adopt the existing BMS management circuit, which will not be elaborated here. The output port adopts the existing output interface, such as for charging electric vehicles, and its output port is a charging gun; the control unit adopts the existing controller.

[0048] Each retired battery module (i.e., a retired battery pack) that forms the energy storage system needs to meet the consistency requirements, that is, the rated voltage and charge and discharge current at the time of leaving the factory must be consistent, and also needs to meet the health requirements, that is, the health value is greater than the set value. The health evaluation is achieved by the control unit using the following method:

[0049] S1. Obtaining environmental characteristics, electrical characteristics and operating characteristics of retired batteries; wherein: the electrical characteristics include: the current I of the retired battery when it is charged and discharged before retirement, the voltage U of the retired battery when it is charged and discharged before retirement, and the charge and discharge depth D of the retired battery when it is charged and discharged before retirement;

[0050] The operation characteristics include: the total number of overcharge and overdischarge of the retired battery K and the number of cycles of the retired battery H. The environmental characteristics include: the temperature T and humidity S of the scene where the retired battery was used before retirement.

[0051] S2. Determine the electrical characteristics P that has the greatest correlation with the DC internal resistance R of the retired battery a The characteristic Q that is most correlated with the DC internal resistance R of the retired battery among the operating characteristics a ;

[0052] S3. According to feature P a and Q a Get feature p a and q a ;

[0053] S4. For all environmental features, features p a and q a Perform feature fusion to obtain fused feature G;

[0054] S5. Input the fused feature G into the machine learning model to obtain the predicted state of health SOH of the retired battery. The machine learning model uses a model that can perform numerical prediction, including but not limited to: multi-layer perceptron, neural network and decision tree.

[0055] Among them: The fusion feature G is obtained by the following formula:

[0056]

[0057] α+β+γ+δ=1

[0058] Among them, α, β, γ and δ represent weight parameters, R represents the DC internal resistance of the retired battery, COV(R, T) represents the covariance of the DC resistance R of the retired battery and the temperature T of the scene where the retired battery was used before retirement, σ R represents the standard deviation of the DC resistance R of retired batteries, σ T represents the standard deviation of the temperature T of the target scenario where the retired battery will be used, and COV(R, S) represents the covariance of the DC resistance R of the retired battery and the humidity S of the scenario where the retired battery was used before retirement.

[0059] When the feature P with the largest correlation a When the current I of the retired battery during charging and discharging before retirement is I, the characteristic p is obtained by the following method a:

[0060] Obtain the current value I of the retired battery when it is charged and discharged before retirement, and determine the number of charge and discharge times i below the preset current range and above the preset current range a , according to the number i a Calculate feature p a :

[0061]

[0062] Where M represents the total number of charge and discharge times of the retired battery before retirement. a When U is the voltage of the retired battery when it is charged and discharged before retirement, the characteristic p is obtained by the following method a :

[0063] Obtain the voltage value U of the retired battery when it is charged and discharged before retirement, and determine the number of charge and discharge times u below the preset voltage range and above the preset voltage range a , according to the number u a Calculate feature p a :

[0064]

[0065] Where M represents the total number of charge and discharge times of the retired battery before retirement. a When the charge and discharge depth D of the retired battery before retirement is charged and discharged, the characteristic p is obtained by the following method a :

[0066] Obtain the charge and discharge depth D of the retired battery before retirement, and determine the number of discharges d that is higher than the preset charge and discharge depth range a , according to the number of discharges d a Calculate feature p a :

[0067]

[0068] Among them, μ represents the influence factor of full discharge, and L represents the total number of discharges of the retired battery before retirement. a When K is the total number of overcharge and overdischarge of retired batteries, the characteristic q is obtained by the following method a :

[0069] K=K1+K2

[0070]

[0071] Among them, K1 represents the number of overcharges, K2 represents the number of overdischarges, and K 21represents the number of full discharges during over-discharge, μ represents the influence factor of full discharge, and N represents the total number of charge and discharge times of the preset retired battery. a When H is the cycle number of the retired battery, the characteristic q is obtained by the following method a :

[0072]

[0073] Wherein, N represents the total number of charge and discharge times of the preset retired battery.

[0074] In this embodiment, the control unit controls the single-pole three-throw relay action according to the photovoltaic power generation information uploaded by the current photovoltaic controller and whether the current charging time node is a peak period, specifically including:

[0075] SA1. The control unit obtains the current state of charge information of the retired battery through the battery management unit, and determines whether the retired battery needs to be charged. If so, it enters SA2, if not, it stops; wherein, determining whether the retired battery needs to be charged is performed in the following manner:

[0076] The control unit determines and obtains the state of charge SOC and battery voltage of all retired batteries. When the state of charge SOC is less than the set threshold (the minimum SOC value that cannot continue to discharge, if continued discharge, it will cause over-discharge) or the number of retired batteries with a voltage value less than the set voltage value (similarly, the voltage value at which the retired battery cannot continue to discharge) is greater than the set value, the energy storage system formed by the retired battery modules needs to be charged. For example: there are a total of 8 retired battery modules. When there are 3 battery modules that cannot continue to discharge, even if the remaining 5 retired batteries are discharged in series, their output voltage converted by the DC-DC conversion circuit (after adjusting the PWM duty cycle) still cannot meet the needs of electrical devices, such as voltage requirements or power requirements. In this case, the retired battery modules need to be charged;

[0077] SA2. The control unit obtains the current output current of the photovoltaic panel from the photovoltaic controller. When the output current of the photovoltaic panel is less than the set threshold, the process proceeds to step SA3. If not, the process proceeds to step SA6.

[0078] SA3 control unit determines whether the current time is the peak period of electricity prices or the flat period of electricity prices. If it is the peak period of electricity prices, it proceeds to step SA4. If it is the flat period of electricity prices, it proceeds to step SA5.

[0079] SA4. The control unit obtains the average number of historical discharges of the energy storage system in the period corresponding to the current time within the set period in the historical data. When the average number of historical discharges is greater than the set value, the control unit controls the moving contact of the single-pole three-throw relay to be turned on with the second static contact, and the retired battery is charged by the power grid. If not, the energy storage system is charged when the electricity price is off-peak or the output current of the photovoltaic panel is greater than the set value. For example, the 24 hours of a day are divided into 12 periods, and any two consecutive hours are a period. For example, the current period is 3 pm, then the average number of discharges in the period corresponding to 3 pm on the same day of the same month in the same season of last year, the year before last, and the year before last for three consecutive years is counted. If the average number is greater than the set number, the power grid is directly charged, indicating that the energy storage system has a large demand during this period. Of course, if a certain data in the historical data is significantly greater than other data, that is, the difference is greater than the set value, the data is eliminated, indicating that this is an individual case and has no reference value.

[0080] SA5. The control unit controls the moving contact of the single-pole three-throw relay to be turned on with the second static contact, and the retired battery is charged by the power grid;

[0081] SA6. The control unit controls the moving contact of the single-pole three-throw relay to be connected with the first static contact, and the photovoltaic panel charges the retired battery. The above method can reduce the cost of use and avoid the impact of power grid fluctuations during peak hours on the energy storage system to a certain extent.

[0082] In this embodiment, the switching control circuit includes a series electronic switch group and a charge and discharge electronic switch group;

[0083] The series electronic switch group includes m-1 electronic switches and is respectively arranged between the positive and negative electrodes of adjacent retired battery modules and connects the adjacent retired battery modules in series; the adjacent here means that the positive and negative electrodes of the two retired battery modules are adjacent; m represents the total number of retired battery modules;

[0084] The charging and discharging electronic switch group includes a plurality of electronic switches, the positive electrode of each retired battery module is connected to the charging DC bus through an electronic switch, the negative electrode of the retired battery module at the end of the series connection is connected to the negative electrode of the charging output port through an electronic switch, and the charging DC bus is connected to the positive electrode of the charging output port of the battery management unit through the charging master switch QZ1; the charging DC bus is connected to the negative electrode of the input end of the DC-DC conversion circuit through an electronic switch;

[0085] The positive electrode of each retired battery module is connected to the discharge DC bus through an electronic switch, and the discharge DC bus is connected to the positive electrode of the input end of the DC-DC conversion circuit through the discharge master switch QZ2. The negative electrode of the retired battery module at the end of the series connection is connected to the negative electrode of the input end of the DC-DC conversion circuit through an electronic switch; the discharge DC bus is connected to the negative electrode of the charging output port through an electronic switch;

[0086] The control input ends of the electronic switches of the series electronic switch group and the charge-discharge electronic switch group are connected to the control unit.

[0087] like Figure 2 As shown: Figure 2 The dotted lines in the figure indicate that the middle battery and the corresponding electronic switch are omitted. Q1 to Qm-1 represent series electronic switches for connecting retired battery modules in series, while QC1-QCn+1 and QD1-QDn+1 represent charge and discharge electronic switches. Although the health of retired batteries needs to be predicted before they are put into use, their performance is different in actual working conditions. If they are not well controlled, they will eventually manifest as charge and discharge imbalance in the retired battery modules in the energy storage system. This phenomenon will cause some retired battery modules to overcharge or over-discharge, thereby affecting the life of the retired batteries. More importantly, it is necessary to prevent thermal imbalance in the charge and discharge process. For example, if the battery is over-discharged, the battery will have excessive temperature rise, which will pose a safety hazard. Although the energy storage system has heat dissipation and cooling, the battery will still swell after thermal imbalance, causing irreversible damage and affecting the stability of the energy storage system. Then, through the above-mentioned switching control circuit, when there is an imbalance, the charge and discharge imbalance can be avoided.

[0088] In this embodiment, the control unit switches the control circuit to perform charging operation in the following manner:

[0089] SB1. The control unit initializes the status information of each retired battery module, the status information includes the current state of charge SOC and voltage of each retired battery module; and the control unit controls the main discharge switch QZ2 to always be in the off state;

[0090] SB2. The control unit sorts the retired battery modules according to the state of charge SOC from small to large, and determines the charging priority of each retired battery module, where the smaller the state of charge SOC, the higher the charging priority;

[0091] SB3. The control unit first controls the electronic switch corresponding to the retired battery module with the smallest state of charge SOC to turn on and the retired battery module enters the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the smallest state of charge SOC reaches the battery voltage with the second smallest state of charge SOC among the retired battery modules, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to turn on, and so on, until all retired battery modules enter the charging state. Control the corresponding electronic switch to be turned on. When charging, Qz2 and QCn+1 must be turned off. Assuming that BAT1 is charged first, then at this time, Qz1, QC2 and QC1 are turned on, and the other electronic switches are turned off. When BAT1 is charged to a certain extent, assuming that BATm should be charged, then at this time, QZ1, QCn, QDn-1, QD2, and QC1 are turned on, and the other electronic devices are turned off. Assuming that BATm needs to be charged, then at this time, QZ1, QCn, QDn-1, and QDn+1 are turned on, and all other electronic switches are turned off, thereby completing the charging. Of course, other combinations are analogous to the above examples. In actual control, when the retired battery module is determined and the structure of the switching control circuit is also determined, the corresponding conduction control table is formulated. As long as the control unit determines the charging order according to the above steps, it directly calls the serial number of the turned-on electronic switch in the conduction control table of the corresponding electronic switch to achieve charging control. Of course, if sorting is not required, the control unit controls the electronic switches corresponding to all retired battery modules to be turned on, and all retired battery modules are directly charged at the same time, that is, Qz1, Q1-Qm-1, and QC1 are turned on, and the remaining electronic switches are all turned off; for QCn+1, it always remains cut off during charging, and during discharging, as long as BAT1 at the end of the series connection participates in discharging, QCn+1 remains cut off, otherwise it remains turned on and QD1 remains cut off; for QDn+1, the situation is the opposite. When discharging, it always remains cut off, and when charging, as long as BAT1 participates in charging, it remains cut off, otherwise it remains turned on and QC1 remains cut off.

[0092] In this embodiment, the control unit switches the control circuit to perform the discharge operation in the following manner:

[0093] SC1. The control unit obtains the state of charge SOC and voltage of each retired battery module at the initial discharge from the battery management unit, and the control unit controls the charging main switch QZ1 to always be in the off state;

[0094] SC2. After the set discharge time, the control unit obtains the state of charge SOC and voltage of each retired battery module from the battery management unit again. When the difference between the current state of charge SOC value of any retired battery module and the average state of charge value of all retired battery modules at the current moment is greater than the set value, or when the difference between the current voltage value of any retired battery module and the average voltage value of all retired battery modules is greater than the set value, the control unit controls the electronic switch corresponding to the current retired battery module to turn off, and the electronic switches corresponding to other retired battery modules are turned on and are in the discharge state. At the same time, the control unit adjusts the duty cycle of the PWM signal output to the DC-DC conversion circuit so that the power of the DC-DC conversion circuit maintains the rated power of the electrical device;

[0095] SC3. Return to step SC2 until the set discharge time is reached or the power provided by the remaining retired battery modules cannot meet the needs of the electrical devices. During the initial discharge, QZ2, Q1-Qm-1, and QD1 are all turned on, and the rest are all turned off. All batteries enter the discharge state. After a certain period of time, assuming that BAT1 reaches the stop discharge state mentioned above first, then at this time, QD1 and Q1 enter the cut-off state, while QCn+1 and QC3, which were originally turned off, enter the conduction state, and the rest of the electronic switches remain turned off. At this time, after BAT1 exits, the overall output voltage will decrease. At this time, the control unit also needs to adjust the duty cycle of the PWM signal according to the current output voltage, so that the DC-DC maintains the original output; when the voltage input to the DC-DC conversion circuit still cannot meet the power demand after conversion, the overall discharge is stopped. Of course, other combinations are analogous to the above examples. Like charging, in actual control, when the retired battery module is determined, the structure of the switching control circuit is also determined, and the corresponding conduction control table is formulated. As long as the control unit determines the exited battery according to the above steps, it directly calls the serial number of the turned-on electronic switch in the conduction control table of the corresponding electronic switch, and discharge control can be achieved.

[0096] In this embodiment, the control unit performs fault warning according to the consistency of the state of charge and the voltage of each retired battery module:

[0097] Among them, the charge state consistency is:

[0098] Among them, CON SOC is the charge state consistency, η SOC is the rate of change of state of charge, is the average rate of change of state of charge of all retired battery modules, SOC0 is the state of charge value of the retired battery module at the initial discharge time after charging, and SOC1 is the state of charge value of the retired battery module after the set discharge time;

[0099] The voltage consistency is:

[0100]

[0101] Among them: CON V is the voltage consistency, η V is the voltage change rate, is the average voltage change rate of all retired battery modules, V0 is the voltage value of the retired battery module at the initial discharge time after charging, and V1 is the voltage value of the retired battery module after the set discharge time;

[0102] When the state of charge consistency value of any retired battery module is greater than the set value or the voltage consistency value is greater than the set value during N consecutive discharges, the control unit will issue a fault alarm through the alarm connected to it. In fact, in practice, it is normal that the state of charge consistency and voltage consistency do not meet the conditions due to a certain discharge imbalance. If the above phenomenon occurs after N consecutive discharges, maintenance is required, such as replacing the retired battery module to avoid safety hazards. This N times is generally set at 3 times.

[0103] In this embodiment, the electronic switch is a MOS tube; because after the NMOS switch is turned on, its current is bidirectional between the gate and source of the NMOS tube, that is, it can flow from the drain to the source and from the source to the drain, thereby ensuring that the loop during switching control is a complete loop, and the NMOS switch has a faster response speed, strong impact resistance, and better stability.

[0104] In this embodiment, the energy storage system further includes a battery status control unit;

[0105] The battery state control unit includes a temperature sensor, a humidity sensor, a battery cooling module and an environment adjustment module;

[0106] The temperature sensors are in two groups, one of which is used to obtain the operating temperature of each retired battery module, and the other is used to obtain the ambient temperature of the environment where the energy storage system is located. The output ends of the temperature sensors and humidity sensors are connected to the control unit, and the control input ends of the battery cooling module and the environment adjustment module are connected to the control unit. The battery cooling module is used to receive the control command of the control unit to cool the retired battery module when the temperature of the retired battery module is higher than the set value, and the environment adjustment module is used to receive the control command of the control unit to adjust the ambient temperature and humidity of the environment where the energy storage system is located when the temperature of the environment is higher than the set value or the humidity is higher than the set value. Energy storage systems are often not open environments, but need to form an integrated device, such as a cabinet or a storage room. For the battery cooling module, some power battery packs originally have water cooling equipment, so the battery cooling module directly uses the retired battery pack's own water cooling equipment. The outside only needs to provide water cooling medium and circulating power. The circulating power uses a water pump. If the retired battery does not have water cooling equipment, the battery cooling module uses an existing fan or air conditioner to cool the energy storage system; and the environmental conditioning module uses an existing fan or air conditioner, because the working environment of the battery needs to be maintained at a suitable temperature and humidity environment, otherwise it will have a serious impact on the battery. Of course, if the retired battery is directly cooled by air, the environmental conditioning module and the battery cooling module can be directly implemented by the same air conditioner.

[0107] In this embodiment, the DC-DC conversion circuit includes a switching power supply circuit and a rectifier filter circuit, the input end of the switching power supply circuit is connected to the discharge output end of the switching control circuit, the output end of the switching power supply circuit is connected to the input end of the rectifier filter circuit, the output end of the rectifier filter circuit is connected to the output port, and the control input end of the switching power supply circuit is connected to the control unit, wherein the switching power supply circuit adopts an existing circuit, the rectifier filter circuit adopts a diode for rectification, and an RC or LC filter circuit for filtering, or adopts a full-bridge rectifier circuit for rectification, and adopts an RC or LRC filter circuit for filtering; the control signal of the switching power supply circuit is a PWM signal, and according to different duty cycles, the output voltage and output power of the DC-DC circuit can be adjusted, or the predetermined output voltage and power can be maintained under different input voltages.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A photovoltaic-based retired battery energy storage control system, Features: It includes retired battery modules, photovoltaic panels, photovoltaic controllers, single-pole three-throw relays, switching control circuits, control units, DC-DC conversion circuits, and output ports; There are multiple retired battery modules, and each retired battery module has a battery management unit, the battery management unit is used to obtain the operating information of the retired battery module and transmit it to the control input end of the control unit, the switching control circuit has an input end and an output end, the input end of the switching control circuit is connected to the moving contact of the single-pole three-throw relay, the output end of the switching control circuit is connected to the input end of the DC-DC conversion circuit, the output end of the DC-DC conversion circuit is connected to the output port, the output port supplies power to the DC power device, the control unit has a switching control output end and a conversion control output end, the switching control output end of the control unit is connected to the switching control circuit The control input end of the control unit is connected to the control input end of the DC-DC conversion circuit; the first static contact of the single-pole three-throw relay is connected to the output end of the photovoltaic controller, the input end of the photovoltaic controller is connected to the photovoltaic battery panel, the photovoltaic controller is also communicatively connected to the control unit, the second static contact of the single-pole three-throw relay is connected to the power grid charging output port, the third static contact of the single-pole three-throw relay is suspended, the control input end of the single-pole three-throw relay is connected to the control unit, and the control unit controls the action of the single-pole three-throw relay according to the photovoltaic power generation information uploaded by the current photovoltaic controller and whether the current charging time node is a peak period.

2. According to the photovoltaic-based retired battery energy storage control system of claim 1, Features: The control unit controls the single-pole three-throw relay action according to the photovoltaic power generation information uploaded by the current photovoltaic controller and whether the current charging time node is a peak period, specifically including: SA1. The control unit obtains the current state of charge information of the retired battery through the battery management unit and determines whether the retired battery needs to be charged. If so, it enters SA2, if not, it stops; SA2. The control unit obtains the current output current of the photovoltaic panel from the photovoltaic controller. When the output current of the photovoltaic panel is less than the set threshold, the process proceeds to step SA3. If not, the process proceeds to step SA6. SA3 control unit determines whether the current time is the peak period of electricity prices or the flat period of electricity prices. If it is the peak period of electricity prices, it proceeds to step SA4. If it is the flat period of electricity prices, it proceeds to step SA5. SA4. The control unit obtains the average number of historical discharges of the energy storage system in the corresponding period at the current time within the set period of time in the historical data. When the average number of historical discharges is greater than the set value, the control unit controls the moving contact of the single-pole three-throw relay to be turned on with the second static contact, and the grid charges the retired battery. If not, the energy storage system is charged when the electricity price is off-peak or the output current of the photovoltaic panel is greater than the set value. SA5. The control unit controls the moving contact of the single-pole three-throw relay to be turned on with the second static contact, and the retired battery is charged by the power grid; SA6. The control unit controls the moving contact of the single-pole three-throw relay to be connected with the first static contact, and the photovoltaic panel charges the retired battery.

3. According to the photovoltaic-based retired battery energy storage control system of claim 2, Features: The switching control circuit includes a series electronic switch group and a charge and discharge electronic switch group; The series electronic switch group includes m-1 electronic switches and is respectively arranged between the positive and negative electrodes of adjacent retired battery modules and connects the adjacent retired battery modules in series; the adjacent here means that the positive and negative electrodes of the two retired battery modules are adjacent; m represents the total number of retired battery modules; The charging and discharging electronic switch group includes a plurality of electronic switches, the positive electrode of each retired battery module is connected to the charging DC bus through an electronic switch, the negative electrode of the retired battery module at the end of the series connection is connected to the negative electrode of the charging output port through an electronic switch, and the charging DC bus is connected to the positive electrode of the charging output port of the battery management unit through the charging master switch QZ1; the charging DC bus is connected to the negative electrode of the input end of the DC-DC conversion circuit through an electronic switch; The positive electrode of each retired battery module is connected to the discharge DC bus through an electronic switch, and the discharge DC bus is connected to the positive electrode of the input end of the DC-DC conversion circuit through the discharge master switch QZ2. The negative electrode of the retired battery module at the end of the series connection is connected to the negative electrode of the input end of the DC-DC conversion circuit through an electronic switch; the discharge DC bus is connected to the negative electrode of the charging output port through an electronic switch; The control input ends of the electronic switches of the series electronic switch group and the charge-discharge electronic switch group are connected to the control unit.

4. According to the photovoltaic-based retired battery energy storage control system of claim 3, Features: The control unit switches the control circuit to perform charging operation in the following manner: SB1. The control unit initializes the status information of each retired battery module, the status information includes the current state of charge SOC and voltage of each retired battery module; and the control unit controls the main discharge switch QZ2 to always be in the off state; SB2. The control unit sorts the retired battery modules according to the state of charge SOC from small to large, and determines the charging priority of each retired battery module, where the smaller the state of charge SOC, the higher the charging priority; SB3. The control unit first controls the electronic switch corresponding to the retired battery module with the smallest state of charge SOC to turn on and the retired battery module enters the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the smallest state of charge SOC reaches the battery voltage with the second smallest state of charge SOC among the retired battery modules, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to turn on, and so on, until all retired battery modules enter the charging state.

5. According to the photovoltaic-based retired battery energy storage control system of claim 4, Features: The control unit switches the control circuit to perform the discharge operation in the following manner: SC1. The control unit obtains the state of charge SOC and voltage of each retired battery module at the initial discharge from the battery management unit, and the control unit controls the charging main switch QZ1 to always be in the off state; SC2. After the set discharge time, the control unit obtains the state of charge SOC and voltage of each retired battery module from the battery management unit again. When the difference between the current state of charge SOC value of any retired battery module and the average state of charge value of all retired battery modules at the current moment is greater than the set value, or when the difference between the current voltage value of any retired battery module and the average voltage value of all retired battery modules is greater than the set value, the control unit controls the electronic switch corresponding to the current retired battery module to turn off, and the electronic switches corresponding to other retired battery modules are turned on and are in the discharge state. At the same time, the control unit adjusts the duty cycle of the PWM signal output to the DC-DC conversion circuit so that the power of the DC-DC conversion circuit maintains the rated power of the electrical device; SC3. Return to step SC2 until the set discharge time is reached or the power provided by the remaining retired battery modules cannot meet the needs of the electrical devices.

6. According to the photovoltaic-based retired battery energy storage control system of claim 5, Features: The control unit performs fault warning according to the consistency of the state of charge and voltage of each retired battery module: Among them, the charge state consistency is: Among them, CON SOC is the charge state consistency, η SOC is the rate of change of state of charge, is the average rate of change of state of charge of all retired battery modules, SOC 0 The state of charge value of the retired battery module at the initial discharge time after charging, SOC 1 The state of charge value of the retired battery module after the set discharge time; The voltage consistency is: Among them: CON V is the voltage consistency, η V is the voltage change rate, is the average voltage change rate of all retired battery modules, V 0 is the voltage value of the retired battery module at the initial discharge time after charging, V 1 The voltage value of the retired battery module after the set discharge time; When any retired battery module has a charge state consistency value greater than a set value or a voltage consistency value greater than a set value during N consecutive discharges, the control unit issues a fault alarm through the alarm connected thereto.

7. According to claim 6, the photovoltaic-based retired battery energy storage control system, Features: The electronic switch is a MOS tube.

8. According to the photovoltaic-based retired battery energy storage control system of claim 7, Features: The energy storage system also includes a battery status control unit; The battery state control unit includes a temperature sensor, a humidity sensor, a battery cooling module and an environment adjustment module; The temperature sensors are in two groups, one of which is used to obtain the operating temperature of each retired battery module, and the other is used to obtain the ambient temperature of the environment where the energy storage system is located. The output ends of the temperature sensors and humidity sensors are connected to the control unit, and the control input ends of the battery cooling module and the environment adjustment module are connected to the control unit. The battery cooling module is used to receive the control command of the control unit to cool the retired battery module when the temperature of the retired battery module is higher than the set value, and the environment adjustment module is used to receive the control command of the control unit to adjust the ambient temperature and humidity of the environment where the energy storage system is located when the temperature of the environment is higher than the set value or the humidity is higher than the set value.

9. According to the photovoltaic-based retired battery energy storage control system of claim 8, Features: The DC-DC conversion circuit includes a switching power supply circuit and a rectifier filter circuit, wherein the input end of the switching power supply circuit is connected to the discharge output end of the switching control circuit, the output end of the switching power supply circuit is connected to the input end of the rectifier filter circuit, the output end of the rectifier filter circuit is connected to the output port, and the control input end of the switching power supply circuit is connected to the control unit.

Images