Photovoltaic based retired battery energy storage control system

Abstract

The application provides a photovoltaic-based retired battery energy storage control system, photovoltaic cell panels are arranged in the energy storage system, when the retired batteries are charged, the charging power supply is determined according to the high, flat peak period and the output of the photovoltaic cell, the diversity of the charging power supply is ensured, certain use cost can be saved, a switching control circuit is arranged in the system, the retired batteries are sequentially charged according to the state of charge and the voltage, when the batteries are discharged, the batteries with low state of charge are discharged, so that the imbalance of charging and discharging is prevented, the service life of the retired batteries is ensured, and the safety hidden danger caused by the imbalance of charging and discharging is eliminated.

Description

TECHNICAL FIELD

[0001] The application relates to a retired battery energy storage control system, in particular to a retired battery energy storage control system based on photovoltaics. BACKGROUND

[0002] With the increasing popularity of electric vehicles, power battery packs, as one of the core components of electric vehicles, are also used more and more. When the power battery pack reaches a certain condition, it cannot meet the demand of electric vehicles, thereby forming a retired battery. Although the retired battery cannot meet the power demand of electric vehicles, it can still meet other scenarios, such as serving as an energy storage power supply.

[0003] The retired battery has been widely used as an energy storage power supply, but the existing energy storage power supply based on the retired battery has the following defects: on the one hand, the charging of the existing energy storage power supply based on the retired battery is single, and is generally based on the mains power supply. When the mains power supply is in a peak period, the electricity price is high, resulting in high use cost. Moreover, the mains power grid has a certain fluctuation during the peak period compared with the flat peak period, and there is a certain electricity risk, such as fluctuation impact.

[0004] More importantly, when the retired battery is used as an energy storage power supply, it cannot be used independently, but a plurality of retired batteries with the same specifications, i.e. 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 as a whole is charged or discharged. However, since it is a retired battery, the stability of the working state is poor, and the charging and discharging imbalance phenomenon easily occurs, thereby existing a safety hazard.

[0005] Therefore, in order to solve the above technical problems, a new technical means is needed. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a retired battery energy storage control system based on photovoltaics, which sets photovoltaic panels in the energy storage system, determines the charging power supply according to the electricity high, flat peak period and the output of the photovoltaic cell when charging the retired battery, ensures the diversity of the charging power supply, saves certain use cost, sets a switching control circuit in the system, sequentially charges according to the state of charge and voltage of the retired battery, and makes the battery with low state of charge exit the discharge during the discharge, thereby preventing the imbalance of charging and discharging, ensuring the service life of the retired battery, and eliminating the safety hazard caused by the imbalance of charging and discharging.

[0007] The application provides a retired battery energy storage control system based on photovoltaics, which comprises a retired battery module, photovoltaic panels, 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] The retired battery modules are multiple, and each retired battery module has a battery management unit for obtaining operation information of the retired battery module and transmitting to a control input end of a 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 direct-current electrical 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 first stationary 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 in communication connection with the control unit, the second stationary contact of the single-pole three-throw relay is connected to the grid charging output port, the third stationary contact of the single-pole three-throw relay is suspended, and the control input end of the single-pole three-throw relay is connected to the control unit; 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 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, and specifically includes:

[0010] SA1. The control unit obtains the current retired battery state of charge information through the battery management unit, and judges whether the retired battery needs to be charged, if yes, it enters SA2, and if no, it stops;

[0011] SA2. The control unit obtains the output current of the current photovoltaic panel from the photovoltaic controller, and when the output current of the photovoltaic panel is less than a set threshold, it enters step SA3, and if not, it enters step SA6;

[0012] SA3. The control unit judges whether the current time is a peak electricity price period or a flat peak electricity price period, if it is a peak electricity price period, it enters step SA4, and if it is a flat peak electricity price period, it enters step SA5;

[0013] SA4. The control unit acquires the historical discharge times of the energy storage system in the time period corresponding to the current time in the historical data, and when the historical discharge times are greater than a set value, the control unit controls the movable contact and the second stationary contact of the single-pole three-throw relay to be conductive, and the retired battery is charged by the power grid, and if not, the control unit waits for the flat peak period of electricity price or the output current of the photovoltaic panel to be greater than a set value to charge the energy storage system;

[0014] SA5. The control unit controls the movable contact and the second stationary contact of the single-pole three-throw relay to be conductive, and the retired battery is charged by the power grid.

[0015] SA6. The control unit controls the movable contact and the first stationary contact of the single-pole three-throw relay to be conductive, and the retired battery is charged by the photovoltaic panel.

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

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

[0018] The charge-discharge electronic switch group comprises a plurality of electronic switches, the positive pole of each retired battery module is connected to a charge DC bus through an electronic switch, the negative pole of the last retired battery module after series connection is connected to the negative pole of the charge output port through an electronic switch, and the charge DC bus is connected to the positive pole of the charge output port of the battery management unit through a charge total switch QZ1; and the charge DC bus is connected to the input negative pole of the DC-DC conversion circuit through an electronic switch.

[0019] The positive pole of each retired battery module is connected to a discharge DC bus through an electronic switch, the discharge DC bus is connected to the positive pole of the input of the DC-DC conversion circuit through a discharge total switch QZ2, and the negative pole of the last retired battery module after series connection is connected to the negative pole of the input of the DC-DC conversion circuit through an electronic switch; and the discharge DC bus is connected to the negative pole of the charge 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 controls the switching control circuit to perform the charging operation in the following manner:

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

[0023] SB2. The control unit sorts each retired battery module according to the state of charge (SOC) from small to large, and determines the charging priority of each retired battery module, 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 be turned on and the retired battery module to enter 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 of the retired battery module with the second smallest state of charge (SOC), the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge (SOC) to be turned 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 discharging 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 discharging time from the battery management unit, and controls the charging total switch QZ1 to be always in the off state;

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

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

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

[0030] wherein the consistency of the state of charge (SOC) is:

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

[0032] The voltage consistency is:

[0033]

[0034] wherein, 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 at the initial discharge time after the retired battery module is charged, and V1 is the voltage value after the retired battery module is discharged for a set time;

[0035] When the value of the state of charge consistency or the value of the voltage consistency of any retired battery module in consecutive N discharge processes is greater than a set value, the control unit performs fault alarm through an alarm connected thereto.

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

[0037] Further, the energy storage system further comprises a battery state control unit;

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

[0039] The temperature sensor is 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 in which the energy storage system is located. The output ends of the temperature sensor and the humidity sensor are connected to the control unit. The control input ends of the battery cooling module and the environment adjusting module are connected to the control unit. The battery cooling module is used to cool the retired battery module when the temperature of the retired battery module is higher than a set value. The environment adjusting module is used to adjust the ambient temperature and humidity of the environment in which the energy storage system is located when the temperature or humidity of the environment is higher than a set value.

[0040] Further, the DC-DC conversion circuit comprises a switching power supply circuit and a rectification filter circuit, an input end of the switching power supply circuit is connected to the discharge output end of the switching control circuit, an output end of the switching power supply circuit is connected to an input end of the rectification filter circuit, an output end of the rectification filter circuit is connected to the output port, and a control input end of the switching power supply circuit is connected to the control unit.

[0041] The application has the following beneficial effects: according to the application, a photovoltaic cell panel is arranged in the energy storage system, the charging power is determined according to the high electricity consumption, flat peak period and output of the photovoltaic cell when the retired battery is charged, the diversity of the charging power is ensured, certain use cost is saved, the switching control circuit is arranged in the system, the charging is sequentially performed according to the state of charge and voltage of the retired battery, the battery with low state of charge is prevented from discharging, the imbalance of charging and discharging is prevented, the service life of the retired battery is ensured, and the safety hidden danger caused by the imbalance of charging and discharging is eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0042] The application will be further described below in combination with the drawings and embodiments:

[0043] Figure 1 The figure is a structural schematic diagram of the application.

[0044] Figure 2 The figure is a schematic diagram of the switching control circuit of the application. DETAILED DESCRIPTION

[0045] The application will be further described below in combination with the drawings and embodiments:

[0046] The application provides a retired battery energy storage control system based on photovoltaic, which comprises a retired battery module, a photovoltaic cell 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] The retired battery modules are multiple, and each retired battery module has a battery management unit, which is used to obtain the operation information of the retired battery module and transmit 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 direct current 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 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 first stationary 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, and the photovoltaic controller is also connected to the control unit in communication, the second stationary contact of the single-pole three-throw relay is connected to the grid charging output port (the grid charging output port refers to setting a charging circuit 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, which is formed by rectification, filtering and DC-DC conversion, and its principle and structure are not described here), the third stationary contact of the single-pole three-throw relay is suspended, and the control input end of the single-pole three-throw relay is connected to the control unit. 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 stationary contact of the single-pole three-throw relay is suspended, that is, when the retired battery does not need to be charged, the stationary contact is placed on the third stationary contact, and the stationary contact is not connected to any connection, thereby preventing misoperation. The single-pole three-throw relay is a prior art, any of the three stationary contacts can be set as the first, second or third stationary contact, which is common sense and will not be described here. The battery management unit adopts an existing BMS management circuit, which will not be described here. The output port adopts an existing output interface, such as a charging gun for charging an electric vehicle; the control unit adopts an existing controller.

[0048] Each retired battery module (i.e. a retired battery pack) forming the energy storage system needs to meet the consistency requirement, i.e. the rated voltage and charging and discharging current at the time of leaving the factory are consistent, and also needs to meet the health degree requirement, i.e. the health degree value is greater than a set value. The evaluation of the health degree is realized by the control unit using the following method:

[0049] S1. Obtain the environmental characteristics, electrical characteristics and operating characteristics of the retired battery; wherein: the electrical characteristics include: the current I of the retired battery before retirement, the voltage U of the retired battery before retirement, and the charge-discharge depth D of the retired battery before retirement; the operating characteristics include: the total number of overcharge and overdischarge K of the retired battery, and the cycle number H of the retired battery; the environmental characteristics include: the temperature T and humidity S of the scene used by the retired battery before retirement.

[0050] The operating characteristics include: the total number of overcharge and overdischarge K of the retired battery, and the cycle number H of the retired battery; the environmental characteristics include: the temperature T and humidity S of the scene used by the retired battery before retirement.

[0051] S2. Determine the characteristic P a with the greatest correlation to the direct current resistance R of the retired battery in the electrical characteristics a and the characteristic Q a with the greatest correlation to the direct current resistance R of the retired battery in the operating characteristics a .

[0052] S3. Obtain the characteristics p a and q a from the characteristics P a and Q a .

[0053] S4. Perform feature fusion on all environmental characteristics, characteristics p R and q T to obtain the fused characteristics G.

[0054] S5. Input the fused characteristics G into a machine learning model to obtain the predicted health degree SOH of the retired battery. The machine learning model selected can be a numerical prediction model, including but not limited to: multilayer perception, neural network and decision tree.

[0055] Wherein: the fused characteristics G are obtained by the following formula:

[0056]

[0057] α+β+γ+δ=1

[0058] Wherein, α, β, γ and δ represent weight parameters, R represents the direct current resistance of the retired battery, COV(R, T) represents the covariance of the direct current resistance R of the retired battery and the temperature T of the scene used by the retired battery before retirement, σ a represents the standard deviation of the direct current resistance R of the retired battery, σ a represents the standard deviation of the temperature T of the target scene to be used by the retired battery, and COV(R, S) represents the covariance of the direct current resistance R of the retired battery and the humidity S of the scene used by the retired battery before retirement.

[0059] When the characteristic P a with the greatest correlation is the current I of the retired battery before retirement, the characteristics p a:

[0060] Obtain the current value I of the retired battery when charging and discharging before retirement, and determine the number of times i of charging and discharging below the preset current range and above the preset current range a , according to the number of times i a Calculate the feature p a :

[0061]

[0062] Where M represents the total number of times of charging and discharging of the retired battery before retirement. When the feature P a with the largest correlation is the voltage U of the retired battery when charging and discharging before retirement, the feature p a is obtained by the following method:

[0063] Obtain the voltage value U of the retired battery when charging and discharging before retirement, and determine the number of times u of charging and discharging below the preset voltage range and above the preset voltage range a , according to the number of times u a Calculate the feature p a :

[0064]

[0065] Where M represents the total number of times of charging and discharging of the retired battery before retirement. When the feature P a with the largest correlation is the depth of charge and discharge D of the retired battery when charging and discharging before retirement, the feature p a is obtained by the following method:

[0066] Obtain the depth of charge and discharge D of the retired battery before retirement, and determine the number of times d of discharging above the preset depth of charge and discharge a , according to the number of times d a Calculate the feature p a :

[0067]

[0068] Where μ represents the influence factor of complete discharge, and L represents the total number of times of discharging of the retired battery before retirement. When the feature Q a with the largest correlation is the total number of times K of overcharging and overdischarging of the retired battery, the feature q a is obtained by the following method:

[0069] K = K1 + K2

[0070]

[0071] Where K1 represents the number of times of overcharging, K2 represents the number of times of overdischarging, and K 21represents the number of complete discharges in over-discharge, μ represents an influence factor of complete discharge, and N represents the total number of preset charging and discharging times of the retired battery. When the correlation of the feature Q a is the cycle number H of the retired battery, the feature q a is obtained by the following method:

[0072]

[0073] where N represents the total number of preset charging and discharging times of the retired battery.

[0074] In the embodiment, the control unit controls the action of the single-pole triple-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, and specifically includes the following steps:

[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 yes, the process proceeds to SA2; if no, the process is stopped. Wherein, whether the retired battery needs to be charged is determined by the following method:

[0076] The control unit determines the state of charge SOC and the battery voltage of all retired batteries. When the number of retired batteries whose state of charge SOC is less than a set threshold (the minimum SOC value at which the retired battery cannot continue to be discharged, and if the retired battery continues to be discharged, over-discharge will occur) or whose voltage value is less than a set voltage value (for the same reason, i.e., the voltage value at which the retired battery cannot continue to be discharged) is greater than a set value, the energy storage system formed by the retired battery module needs to be charged. For example, there are a total of 8 retired battery modules. When 3 battery modules cannot continue to be discharged, even if the remaining 5 retired batteries are discharged in series, the output voltage converted by the DC-DC conversion circuit (after adjusting the PWM duty cycle) still cannot meet the requirements of the electrical device, such as voltage requirements or power requirements. At this time, the retired battery module needs to be charged.

[0077] SA2. The control unit obtains the output current of the current photovoltaic cell panel from the photovoltaic controller. When the output current of the photovoltaic cell panel is less than a set threshold, the process proceeds to step SA3; otherwise, the process proceeds to step SA6.

[0078] SA3. The control unit determines whether the current time is a peak electricity price period or a flat electricity price period. If it is a peak electricity price period, the process proceeds to step SA4; if it is a flat electricity price period, the process proceeds to step SA5.

[0079] SA4. The control unit obtains the average number of discharges of the energy storage system in the time period corresponding to the current time within the set time limit in the historical data, and when the average number of discharges is greater than a set value, the control unit controls the movable contact and the second stationary contact of the single-pole three-throw relay to be conductive, and the retired battery is charged by the power grid, and if not, the energy storage system is charged when the electricity price is flat or the output current of the photovoltaic panel is greater than a set value; for example, 24 hours in a day are divided into 12 time periods, and any two consecutive hours are a time period, for example, the current time period is 3 pm, and then the average number of discharges in the time period corresponding to 3 pm on the same day in the same month in the same season in the past three years is counted, and if the average number of discharges is greater than a set number, the retired battery is directly charged by the power grid, indicating that the energy storage system requires a larger period in this period. Of course, if a data in the historical data is obviously greater than other data, that is, the difference is greater than a set value, the data is excluded, indicating that this is an individual case and has no reference value.

[0080] SA5. The control unit controls the movable contact and the second stationary contact of the single-pole three-throw relay to be conductive, and the retired battery is charged by the power grid.

[0081] SA6. The control unit controls the movable contact and the first stationary contact of the single-pole three-throw relay to be conductive, and the retired battery is charged by the photovoltaic panel. Through the above method, the use cost can be reduced, and the influence of the power grid fluctuation in the peak period on the energy storage system can be avoided to a certain extent.

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

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

[0084] The charge-discharge electronic switch group includes a plurality of electronic switches, the positive pole of each retired battery module is connected to a charge DC bus through an electronic switch, and the negative pole of the last retired battery module after series connection is connected to the negative pole of the charge output port through an electronic switch. The charge DC bus is connected to the positive pole of the charge output port of the battery management unit through a charge total switch QZ1; and the charge DC bus is connected to the input negative pole of the DC-DC conversion circuit through an electronic switch.

[0085] The positive electrode of each retired battery module is connected to a discharge DC busbar via an electronic switch. The discharge DC busbar is connected to the positive electrode of the input terminal of the DC-DC converter circuit via a discharge master switch QZ2. The negative electrode of the last retired battery module in the series connection is connected to the negative electrode of the input terminal of the DC-DC converter circuit via an electronic switch. The discharge DC busbar is connected to the negative electrode of the charging output port via 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 dashed lines in the figure indicate the omission of the middle battery and the corresponding electronic switches. Q1 to Qm-1 represent series electronic switches used to connect the retired battery modules in series, while QC1-QCn+1 and QD1-QDn+1 represent charge and discharge electronic switches. Although a health prediction is required before retired batteries are put into use, their performance varies in actual operating conditions. If not properly controlled, this can ultimately manifest as charge and discharge imbalances among the retired battery modules in the energy storage system. This can cause some retired battery modules to overcharge or overdischarge, thereby shortening the lifespan of the retired batteries. More importantly, thermal imbalances during the charge and discharge process must be prevented. For example, overdischarge can cause excessive temperature rise, posing a safety hazard. Although energy storage systems provide heat dissipation and cooling, thermal imbalances can still cause battery expansion, resulting in irreversible damage and affecting the stability of the energy storage system. The switching control circuit described above can prevent charge and discharge imbalances when these imbalances occur.

[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 is always 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 minimum state of charge SOC to be turned on and the retired battery module to enter the charging state, and obtains the battery voltage of the retired battery module. When the voltage of the retired battery module with the minimum state of charge SOC reaches the battery voltage of the retired battery module with the second minimum state of charge SOC, the control unit controls the electronic switch corresponding to the retired battery module with the second minimum state of charge SOC to be turned on, and so on, until all the retired battery modules enter the charging state. The corresponding electronic switch is controlled to be turned on. When charging, Qz2 and QCn+1 are definitely turned off. Assuming that BAT1 is preferentially charged, at this time, Qz1, QC2 and QC1 are turned on, and the remaining electronic switches are turned off. When BAT1 is charged to a certain extent, assuming that BATm needs to be charged, at this time, QZ1, QCn, QDn-1, QD2 and QC1 are turned on, and the remaining electronic switches are turned off. Assuming that BATm needs to be charged, at this time, QZ1, QCn, QDn-1 and QDn+1 are turned on, and the remaining electronic switches are turned off, thereby completing the charging. Of course, other combinations can be similarly deduced from the above examples. In actual control, when the retired battery modules are determined and the structure of the switching control circuit is determined, the corresponding on-off control table is implemented. As long as the control unit determines the charging sequence according to the above steps, the on-off control table of the corresponding electronic switch is directly called, and the charging control can be realized. Of course, if sorting is not required, the control unit controls all the electronic switches corresponding to the retired battery modules to be turned on, and all the 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 turned off. For QCn+1, it is always turned off during charging. During discharging, as long as BAT1 participates in discharging, QCn+1 is turned off, otherwise it is turned on and QD1 is turned off. For QDn+1, the situation is the opposite. During discharging, it is always turned off. During charging, as long as BAT1 participates in charging, it is turned off, otherwise it is turned on and QC1 is turned off.

[0092] In this embodiment, the control unit switches the control circuit to perform discharging 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 discharging time from the battery management unit, and controls the charging main switch QZ1 to be always turned off.

[0094] SC2. After the discharge setting 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 value of the state of charge of all retired battery modules at the current time is greater than a set value, or when the difference between the current voltage value of any retired battery module and the average value of the voltage of all retired battery modules is greater than a set value, the control unit controls the electronic switch corresponding to the current retired battery module to be turned off, and the electronic switches corresponding to the other retired battery modules to be turned on and in a discharging state. At the same time, the control unit adjusts the duty cycle of the PWM signal output to the DC-DC conversion circuit to keep the power of the DC-DC conversion circuit at 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 demand of the electrical device. When initial discharging, QZ2, Q1-Qm-1, and QD1 are all turned on, and the rest are all turned off. All the batteries enter a discharging state. When a certain time is reached, assume that BAT1 reaches the stop discharging state first. At this time, QD1 and Q1 are turned off, and QCn+1 and QC3 that were originally kept off are turned on. The remaining electronic switches are still kept off. After BAT1 exits, the overall output voltage will decrease. At this time, the control unit needs to adjust the duty cycle of the PWM signal according to the current output voltage, so that the DC-DC remains the original output. When the voltage input to the DC-DC conversion circuit cannot meet the electrical demand after conversion, the overall discharging stops. Of course, other combinations can be similarly deduced from the above example. As with charging, when the retired battery modules are determined and the structure of the switching control circuit is determined, the corresponding on-off control table is implemented. As long as the control unit determines the exit of the battery according to the above steps, it can directly call the on-off electronic switch sequence number in the on-off control table of the corresponding electronic switch to achieve discharging control.

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

[0097] wherein the consistency of the state of charge is:

[0098] wherein CON SOC is the consistency of the state of charge, η SOC is the state of charge change rate, is the average value of the state of charge change rate of all retired battery modules, SOC0 is the state of charge value at the initial discharging time after charging of the retired battery module, and SOC1 is the state of charge value after the retired battery module discharges for a set time.

[0099] The voltage consistency is:

[0100]

[0101] CON V The voltage consistency is: V The voltage consistency is: The voltage consistency is:

[0102] When any of the retired battery modules in the continuous N times of discharging process, the value of the state of charge consistency or the value of the voltage consistency is greater than the set value, the control unit alarms through the alarm connected therewith. In fact, in practice, the discharging imbalance of a certain time leads to the state of charge consistency and the voltage consistency not meeting the conditions, which is relatively normal. If the above phenomenon occurs continuously for N times of discharging, maintenance is needed, such as replacing the retired battery module, so as to avoid causing safety hazards. The N times is generally set to 3 times.

[0103] In the embodiment, the electronic switch is an NMOS tube. After the NMOS tube is turned on, the current between the gate and the source of the NMOS tube has bidirectionality, that is, the current can flow from the drain to the source and from the source to the drain, so that a complete loop can be ensured when switching control is performed. In addition, the NMOS tube has high speed, strong impact resistance and good stability.

[0104] In the embodiment, the energy storage system further comprises a battery state control unit.

[0105] The battery state control unit comprises a temperature sensor, a humidity sensor, a battery cooling module and an environment adjusting module.

[0106] The temperature sensor is two groups, one group is used to obtain the operating temperature of each retired battery module, and the other group is used to obtain the ambient temperature of the environment where the energy storage system is located, the output ends of the temperature sensor and the humidity sensor are connected to the control unit, the control input ends of the battery cooling module and the environment adjusting 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 adjusting 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. The energy storage system is often not an open environment, but needs to form a whole 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 water cooling equipment of the retired battery pack itself, and only needs to provide water cooling medium and circulating power outside. The circulating power adopts a water pump. If the retired battery does not have water cooling equipment, the battery cooling module adopts an existing fan or air conditioner to realize the cooling of the energy storage system. The environment adjusting module adopts an existing fan or air conditioner. Because the working environment of the battery needs to be kept at a suitable temperature and humidity environment, otherwise it will have a serious impact on the battery. Of course, if the retired battery directly adopts air cooling, the environment adjusting module and the battery cooling module can directly use the same air conditioner to realize it.

[0107] In the embodiment, the DC-DC conversion circuit includes a switching power supply circuit and a rectification 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 rectification filter circuit, the output end of the rectification 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. The switching power supply circuit adopts an existing circuit, the rectification filter circuit adopts a diode for rectification, an RC or LC filter circuit for filtering, or a full-bridge rectification circuit for rectification and an RC or LRC filter circuit for filtering. The control signal of the switching power supply circuit is a PWM signal, and the output voltage and output power of the DC-DC circuit can be adjusted according to different duty cycles, or the output voltage and power can be kept at a certain value under different input voltages.

[0108] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A photovoltaic based decommissioned battery energy storage control system, characterized by: The application relates to a photovoltaic energy storage system, which comprises a plurality of retired battery modules, 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. The retired battery modules are connected to the control input end of the control unit through the battery management unit, 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 direct-current electric 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 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 further connected to the control unit in communication, the second static contact of the single-pole three-throw relay is connected to the grid charging output port, the third static contact of the single-pole three-throw relay is suspended, and the control input end of the single-pole three-throw relay is connected to the control unit; 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. 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, and the method specifically comprises the following steps: SA1. The control unit obtains the current retired battery state of charge information through the battery management unit, and judges whether the retired battery needs to be charged; if yes, the step SA2 is entered; if no, the step is stopped; SA2. The control unit obtains the output current of the current photovoltaic panel from the photovoltaic controller; if the output current of the photovoltaic panel is less than a set threshold value, the step SA3 is entered; if no, the step SA6 is entered; SA3. The control unit judges whether the current time is a peak electricity price period or a flat peak electricity price period; if it is a peak electricity price period, the step SA4 is entered; if it is a flat peak electricity price period, the step SA5 is entered; SA4. The control unit obtains the average historical discharge frequency of the energy storage system in the time period corresponding to the current time within the set time limit in the historical data; if the average historical discharge frequency is greater than a set value, the control unit controls the moving contact of the single-pole three-throw relay to be conductive with the second static contact, and the retired battery is charged by the grid; if no, the energy storage system is charged by the grid when the output current of the photovoltaic panel is greater than a set value or the flat peak electricity price period arrives; SA5. The control unit controls the moving contact of the single-pole three-throw relay to be conductive with the second static contact, and the retired battery is charged by the grid; SA6. The control unit controls the moving contact of the single-pole three-throw relay to be conductive with the first static contact, and the retired battery is charged by the photovoltaic panel.

2. The photovoltaic-based decommissioned battery energy storage control system of claim 1, wherein: The switching control circuit comprises a series electronic switch group and a charge-discharge electronic switch group; The series electronic switch group comprises m-1 electronic switches and is arranged between the positive and negative poles of adjacent retired battery modules to connect the adjacent retired battery modules in series; here, adjacent refers to the positive and negative poles of two retired battery modules being adjacent; m represents the total number of retired battery modules; The charge-discharge electronic switch group comprises a plurality of electronic switches, the positive pole of each retired battery module is connected to a charge DC bus through an electronic switch, the negative pole of the last retired battery module in series is connected to the negative pole of a charge output through an electronic switch, and the charge DC bus is connected to the positive pole of a charge output of a battery management unit through a charge total switch QZ1; the charge DC bus is connected to the input negative pole of a DC-DC conversion circuit through an electronic switch; The positive pole of each retired battery module is connected to a discharge DC bus through an electronic switch, the discharge DC bus is connected to the positive pole of the input of a DC-DC conversion circuit through a discharge total switch QZ2, and the negative pole of the last retired battery module in series is connected to the negative pole of the input of the DC-DC conversion circuit through an electronic switch; the discharge DC bus is connected to the negative pole of the charge output 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 a control unit.

3. The photovoltaic-based decommissioned battery energy storage control system of claim 2, wherein: The control unit controls the switching control circuit to perform a charge operation in the following manner: SB1. The control unit initializes the state information of each retired battery module, the state information comprising the current state of charge SOC and voltage of each retired battery module; and the control unit controls the discharge total switch QZ2 to be always in an off state; SB2. The control unit sorts each retired battery module according to the state of charge SOC from small to large, and determines the charge priority of each retired battery module, the smaller the state of charge SOC, the higher the charge priority; SB3. The control unit first controls the electronic switch corresponding to the retired battery module with the smallest state of charge SOC to be turned on and the retired battery module to be in a charge 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 of the retired battery module with the second smallest state of charge SOC, the control unit controls the electronic switch corresponding to the retired battery module with the second smallest state of charge SOC to be turned on, and so on, until all the retired battery modules are in the charge state.

4. The photovoltaic-based decommissioned battery energy storage control system of claim 3, wherein: The control unit controls the switching control circuit to perform a 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 time of discharge from a battery management unit, and controls the charge total switch QZ1 to be always in an off state; SC2. After the discharge setting 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 value of the state of charge of all retired battery modules at the current time is greater than a set value, or when the difference between the current voltage value of any retired battery module and the average value of the voltage of all retired battery modules is greater than a set value, the control unit controls the electronic switch corresponding to the current retired battery module to be turned off, and the electronic switches corresponding to the other retired battery modules to be turned on and in a discharge state. At the same time, the control unit adjusts the duty cycle of the PWM signal output to the DC-DC conversion circuit to keep the power of the DC-DC conversion circuit at 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 demand of the electrical device.

5. The photovoltaic-based decommissioned battery energy storage control system of claim 4, wherein: The control unit performs fault warning according to the consistency of the state of charge and the consistency of the voltage of each retired battery module: The consistency of the state of charge is: wherein CON SOC is the state of charge consistency, η SOC is the state of charge change rate, is the average state of charge change rate of all retired battery modules, SOC0 is the state of charge value at the initial discharge time after the retired battery module is charged, and SOC1 is the state of charge value after the retired battery module is discharged for a set time. The consistency of the voltage is: wherein: CON V for voltage consistency, η V for voltage change rate, for the average voltage change rate of all retired battery modules, V0 is the voltage value at the initial discharge time after the retired battery module is charged, and V1 is the voltage value after the retired battery module is discharged for a set time. When any retired battery module has a value greater than a set value in the consistency of the state of charge or a value greater than a set value in the consistency of the voltage in consecutive N discharge processes, the control unit performs fault warning through the alarm connected thereto.

6. The photovoltaic-based decommissioned battery energy storage control system of claim 5, wherein: The electronic switch is a MOS tube.

7. The photovoltaic-based decommissioned battery energy storage control system of claim 6, wherein: The energy storage system further comprises a battery state control unit; The battery state control unit comprises a temperature sensor, a humidity sensor, a battery cooling module, and an environment adjusting module; The temperature sensor has 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 terminals of the temperature sensor and the humidity sensor are connected to the control unit. The control input terminals of the battery cooling module and the environment adjusting module are connected to the control unit. The battery cooling module is used to cool the retired battery module when the temperature of the retired battery module is higher than a set value. The environment adjusting module is used to adjust the ambient temperature and humidity of the environment where the energy storage system is located when the temperature or humidity of the environment is higher than a set value.

8. The photovoltaic-based decommissioned battery energy storage control system of claim 7, wherein: The DC-DC conversion circuit comprises a switching power supply circuit and a rectifier filter circuit. The input terminal of the switching power supply circuit is connected to the discharge output terminal of the switching control circuit. The output terminal of the switching power supply circuit is connected to the input terminal of the rectifier filter circuit. The output terminal of the rectifier filter circuit is connected to the output port. The control input terminal of the switching power supply circuit is connected to the control unit.

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