Control method of energy storage system and energy storage system

Abstract

The invention discloses a control method of an energy storage system and the energy storage system, and the energy storage system comprises a limit value management system and a smooth control system, and the method comprises the following steps: 1, collecting data including voltage and current, and judging whether the end voltage of a storage battery is in a working voltage range or not; step 2, if the judgment result is yes in the step 1, stabilizing the voltage of the direct current bus by using the storage battery; thirdly, load power fluctuation is larger than a threshold value; 4, the super capacitor provides abrupt change power; 5, if not, the storage battery is charged in a constant-voltage and current-limiting mode; compared with the prior art, the energy storage device has the advantages that the energy storage device has better adaptability to loads, reliable power supply is provided, the output current peak value of the storage battery is reduced, the discharging time of the storage battery is prolonged, the internal loss of the storage battery is reduced, the charging and discharging process of the storage battery is optimized, and the failure progress of the storage battery is slow.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a control method of an energy storage system and an energy storage system. Background Art

[0002] In solar photovoltaic power generation systems, the main function of batteries is to maintain the stability of the system. When the light is strong, the battery will store the excess power generated by the photovoltaic cell; when the sunlight intensity is low, the power generated by the photovoltaic cell is not enough to maintain the load consumption of the system, and the battery will release the stored power to the system to ensure the stable and normal operation of the system. The battery has a high energy density, so it is most commonly used in photovoltaic power generation systems. However, due to its low power output capacity and short life, its configuration capacity in the system must be much larger than the load capacity, which causes great waste.

[0003] The energy density of supercapacitors is much lower than that of batteries. The factor that has a greater impact on the end voltage of supercapacitors is the change in energy storage capacity, especially at the beginning or end of charging and discharging, the end voltage of supercapacitors will change more significantly. The amplitude of its voltage fluctuation is mainly affected by the internal equivalent resistance of the capacitor and the current during charging. Therefore, in order to ensure the stability of the system voltage, we must add a converter between the load and the supercapacitor, which makes the system structure more complicated, and the efficiency will decrease accordingly, and it will also increase the investment cost of the system.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the above technical defects, provide a control method and an energy storage system, combine the advantages of the battery and the supercapacitor, make the whole energy storage device have better adaptability to the load, provide more reliable power supply, reduce the weight of the device, and reduce the size of the device. In the process of mixed use of batteries and supercapacitors, the peak value of the output current of the battery can be reduced, so that the discharge time of the battery can be better extended and the internal loss of the battery can be reduced, and the whole charging and discharging process of the battery can be better optimized, so that the process of battery failure is slower.

[0006] In order to solve the above problems, the technical solution of the present invention is a control method of an energy storage system and an energy storage system: the method includes a limit management system and a smooth control system, the limit management system is an upper energy management system, and the smooth control system is a lower energy management system;

[0007] The method comprises the following steps:

[0008] Step 1: Collect data, including voltage and current, to determine whether the battery terminal voltage is within the operating voltage range;

[0009] Step 2: If the answer in step 1 is yes, use the battery to stabilize the DC bus voltage;

[0010] Step 3: Load power fluctuation is greater than a threshold;

[0011] Step 4: The supercapacitor provides sudden power;

[0012] Step 5: If the judgment in step 1 is no, the battery is charged with constant voltage and current limitation.

[0013] Further, the energy storage mode of the supercapacitor in the step 4 is: E=CU2 / 2, where E is the total energy stored in the supercapacitor, C is the capacitance value of the supercapacitor, and U is the voltage value at the end of the supercapacitor;

[0014] Where S is the remaining energy storage capacity of the supercapacitor, 0 and 1 are the remaining energy storage capacity of the supercapacitor and U MIN and U MIN The corresponding value.

[0015] Furthermore, the supercapacitor terminal voltage pre-control method is introduced into the limit value management, and the system's battery and supercapacitor power reference value is P before correction. S and P b , the remaining energy stored in the battery is S s , and P S Correction amount + P b The correction amount = 0, the battery and supercapacitor hybrid energy storage energy management method based on the pre-control of the supercapacitor terminal voltage needs to make U MIN <U DOWN <U UP <U MAX , where U DOWN and U UP The upper and lower limits of the terminal voltage pre-control judgment conditions of the supercapacitor are set. The terminal voltage pre-control of the supercapacitor is issued to take corresponding pre-control before the terminal voltage reaches the maximum and minimum limits.

[0016] Furthermore, the operation of the supercapacitor is divided into five intervals, and the five intervals include: a normal working area, a low voltage limit area, a high voltage limit area, a low voltage limit crossing area, and a high voltage limit crossing area;

[0017] The reference power of the supercapacitor in the normal working area does not need to be adjusted. DOWN <U<U UP ;

[0018] In the low voltage limit region, the supercapacitor voltage drop rate is reduced by reducing the discharge amount of the supercapacitor and increasing the charge amount of the supercapacitor. As the standard for pre-control of the supercapacitor end voltage at this stage, U MIN <U<U DAWN When P S >0, ΔP S =P S (U DAWN -U) / (U DAWN -U MIN ); when P S When ΔP < 0 S =-P S (U DAWN -U) / (U DAWN -U MIN );

[0019] In the high-voltage limit region, the supercapacitor voltage rise rate is reduced by reducing the charge amount of the supercapacitor and increasing the discharge amount of the supercapacitor. As the standard for pre-control of the supercapacitor end voltage at this stage, U UP <U<U MAX When P S >0, ΔP S =-P S (U UP -U) / (U MAX -U UP ); when P S When ΔP < 0 S =P S (U UP -U) / (U MAX -U UP );

[0020] When the supercapacitor is working in the low voltage limit region, the supercapacitor is only allowed to be charged and the discharge is restricted. The supercapacitor terminal voltage value U≤U MIN , when P S >0, there will be ΔP S =-P S When P S When <0, there will be ΔP S =0;

[0021] When the supercapacitor in the high-voltage limit region works, the supercapacitor is only allowed to discharge, and charging is restricted. The supercapacitor terminal voltage value U MAX ≤U, when P S >0, there will be ΔP S =0; when P S When <0, there will be ΔP S =-P S .

[0022] Furthermore, the control method determines the next operating mode of the system according to whether the power fluctuation of the load exceeds the initially set threshold value. If the load power fluctuation does not exceed the value, the battery will stabilize the voltage on the DC bus, and the supercapacitor will perform constant voltage and current limiting charging and discharging; if the power fluctuation of the load exceeds the set threshold, the supercapacitor will provide the sudden change power required by the load. After the sudden change, the supercapacitor will self-charge and discharge to prepare for the next load sudden change in advance.

[0023] Furthermore, the charging and discharging of the energy storage element is realized by a bidirectional DC / DC converter, and the working mode of the bidirectional converter adopts voltage and current double closed loop regulation. The traditional voltage outer loop and current inner loop both adopt P control mode.

[0024] Furthermore, an energy storage system is characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the program, the control method of the energy storage system is implemented.

[0025] The advantages of the present invention compared with the prior art are:

[0026] 1. The present invention combines the advantages of the battery and the supercapacitor, so that the entire energy storage device has better adaptability to the load, provides more reliable power supply, can reduce the weight of the device, and reduce the size of the device. In the process of mixed use of batteries and supercapacitors, the peak value of the output current of the battery can be reduced, so that the discharge time of the battery can be better extended and the internal loss of the battery can be reduced. In addition, the entire charging and discharging process of the battery can be better optimized, so that the process of battery failure is slower. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a system control flow chart of the present invention. DETAILED DESCRIPTION

[0028] In order to make the contents of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] like Figure 1 As shown, a control method for an energy storage system includes a limit management system and a smooth control system, wherein the limit management system is an upper-layer energy management system and the smooth control system is a lower-layer energy management system;

[0030] The method comprises the following steps:

[0031] Step 1: Collect data, including voltage and current, to determine whether the battery terminal voltage is within the operating voltage range;

[0032] Step 2: If the answer in step 1 is yes, use the battery to stabilize the DC bus voltage;

[0033] Step 3: Load power fluctuation is greater than a threshold;

[0034] Step 4: The supercapacitor provides sudden power;

[0035] Step 5: If the judgment in step 1 is no, the battery is charged with constant voltage and current limitation.

[0036] The energy storage method of the supercapacitor in step 4: E = CU 2 / 2, where E is the total energy stored in the supercapacitor, C is the capacitance of the supercapacitor, and U is the voltage value at the end of the supercapacitor;

[0037] Where S is the remaining energy storage capacity of the supercapacitor, 0 and 1 are the remaining energy storage capacity of the supercapacitor and U MIN and U MIN The corresponding value.

[0038] The supercapacitor terminal voltage pre-control method is introduced into the limit management. The system's battery and supercapacitor power reference value is P before correction. S and P b , the remaining energy stored in the battery is S s , and P S Correction amount + P b The correction amount = 0, the battery and supercapacitor hybrid energy storage energy management method based on the pre-control of the supercapacitor terminal voltage needs to make U MIN <U DOWN <U UP <U MAX , where U DOWN and U UP The upper and lower limits of the terminal voltage pre-control judgment conditions of the supercapacitor are set. The terminal voltage pre-control of the supercapacitor is issued to take corresponding pre-control before the terminal voltage reaches the maximum and minimum limits.

[0039] The operation of the supercapacitor is divided into five intervals, including: normal working area, low voltage limit area, high voltage limit area, low voltage limit crossing area and high voltage limit crossing area;

[0040] The reference power of the supercapacitor in the normal working area does not need to be adjusted. DOWN <U<U UP ;

[0041] In the low voltage limit region, the supercapacitor voltage drop rate is reduced by reducing the discharge amount of the supercapacitor and increasing the charge amount of the supercapacitor. As the standard for pre-control of the supercapacitor end voltage at this stage, U MIN <U<U DAWN When P S >0, ΔP S =P S (U DAWN -U) / (U DAWN -U MIN ); when P S When ΔP < 0 S =-P S (U DAWN -U) / (U DAWN -U MIN );

[0042] In the high-voltage limit region, the supercapacitor voltage rise rate is reduced by reducing the charge amount of the supercapacitor and increasing the discharge amount of the supercapacitor. As the standard for pre-control of the supercapacitor end voltage at this stage, U UP <U<U MAX When P S >0, ΔP S =-P S (U UP -U) / (U MAX -U UP ); when P S When ΔP < 0 S =P S (U UP -U) / (U MAX -U UP );

[0043] When the supercapacitor is working in the low voltage limit region, the supercapacitor is only allowed to be charged and the discharge is restricted. The supercapacitor terminal voltage value U≤U MIN , when P S >0, there will be ΔP S =-P S When P S When <0, there will be ΔP S =0;

[0044] When the supercapacitor in the high-voltage limit region works, the supercapacitor is only allowed to discharge, and charging is restricted. The supercapacitor terminal voltage value U MAX ≤U, when P S >0, there will be ΔP S =0; when P S When <0, there will be ΔP S =-P S .

[0045] The control method is to determine the next operating mode of the system according to whether the power fluctuation of the load exceeds the initially set threshold. If the load power fluctuation does not exceed the value, the battery will stabilize the voltage on the DC bus, and the supercapacitor will perform constant voltage and current limiting charging and discharging; if the power fluctuation of the load exceeds the set threshold, the supercapacitor will provide the sudden power required by the load. After the mutation, the supercapacitor will self-charge and discharge to prepare for the next load mutation in advance.

[0046] The charging and discharging of the energy storage element is realized through a bidirectional DC / DC converter, and the working mode of the bidirectional converter adopts voltage and current double closed loop regulation. The traditional voltage outer loop and current inner loop both adopt P control mode.

[0047] An energy storage system includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, a control method for the energy storage system is implemented.

[0048] The present invention and its embodiments are described above, which is not restrictive. The drawings are only one of the embodiments of the present invention. In short, if ordinary technicians in the field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A control method for an energy storage system, characterized in that: The method includes a limit management system and a smooth control system, wherein the limit management system is an upper-layer energy management system and the smooth control system is a lower-layer energy management system; The method comprises the following steps: Step 1: Collect data, including voltage and current, to determine whether the battery terminal voltage is within the operating voltage range; Step 2: If the answer in step 1 is yes, use the battery to stabilize the DC bus voltage; Step 3: Load power fluctuation is greater than a threshold; Step 4: The supercapacitor provides sudden power; Step 5: If the judgment in step 1 is no, the battery is charged with constant voltage and current limitation.

2. The control method and energy storage system of an energy storage system according to claim 1, characterized in that: The energy storage method of the supercapacitor in step 4: E=CU 2 / 2, where E is the total energy stored in the supercapacitor, C is the capacitance of the supercapacitor, and U is the voltage value at the end of the supercapacitor; Where S is the remaining energy storage capacity of the supercapacitor, 0 and 1 are the remaining energy storage capacity of the supercapacitor and U MIN and U MIN The corresponding value.

3. The control method and energy storage system of an energy storage system according to claim 1, characterized in that: The supercapacitor terminal voltage pre-control method is introduced into the limit management. The system's battery and supercapacitor power reference value is P before correction. S and P b , the remaining energy of the battery is stored as S s , and P S Correction amount + P b The correction amount = 0, the battery and supercapacitor hybrid energy storage energy management method based on the pre-control of the supercapacitor terminal voltage needs to make U MIN <U DOWN <U UP <U MAX , where U DOWN and U UP The upper and lower limits of the terminal voltage pre-control judgment conditions of the supercapacitor are set. The terminal voltage pre-control of the supercapacitor is issued to take corresponding pre-control before the terminal voltage reaches the maximum and minimum limits.

4. The control method and energy storage system of an energy storage system according to claim 3, characterized in that: The supercapacitor is divided into five working ranges, including: a normal working range, a low voltage limit range, a high voltage limit range, a low voltage limit crossing range and a high voltage limit crossing range; The reference power of the supercapacitor in the normal working area does not need to be adjusted. DOWN <U<U UP ; In the low voltage limit region, the supercapacitor voltage drop rate is reduced by reducing the discharge amount of the supercapacitor and increasing the charge amount of the supercapacitor. As the standard for pre-control of the supercapacitor end voltage at this stage, U MIN <U<U DAWN When P S >0, ΔP S =P S (U DAWN -U) / (U DAWN -U MIN ); when P S When ΔP < 0 S =-P S (U DAWN -U) / (U DAWN -U MIN ); In the high-voltage limit region, the supercapacitor voltage rise rate is reduced by reducing the charge amount of the supercapacitor and increasing the discharge amount of the supercapacitor. As the standard for pre-control of the supercapacitor end voltage at this stage, U UP <U<U MAX When P S >0, ΔP S =-P S (U UP -U) / (U MAX -U UP ); when P S When ΔP < 0 S =P S (U UP -U) / (U MAX -U UP ); When the supercapacitor is working in the low voltage limit region, the supercapacitor is only allowed to be charged and the discharge is restricted. The supercapacitor terminal voltage value U≤U MIN , when P S >0, there will be ΔP S =-P S When P S When <0, there will be ΔP S =0; When the supercapacitor in the high-voltage limit region works, the supercapacitor is only allowed to discharge, and charging is restricted. The supercapacitor terminal voltage value U MAX ≤U, when P S >0, there will be ΔP S =0; when P S When <0, there will be ΔP S =-P S .

5. The control method and energy storage system of an energy storage system according to claim 1, characterized in that: The control method determines the next operation mode of the system according to whether the power fluctuation of the load exceeds the initially set threshold value. If the load power fluctuation does not exceed the value, the battery will stabilize the voltage on the DC bus, and the supercapacitor will perform constant voltage and current limiting charging and discharging; if the power fluctuation of the load exceeds the set threshold, the supercapacitor will provide the sudden change power required by the load. After the sudden change, the supercapacitor will self-charge and discharge to prepare for the next load sudden change in advance.

6. The control method and energy storage system of an energy storage system according to claim 1, characterized in that: The charging and discharging of the energy storage element is realized by a bidirectional DC / DC converter, and the working mode of the bidirectional converter adopts voltage and current double closed loop regulation. The traditional voltage outer loop and current inner loop both adopt P control mode.

7. An energy storage system, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the program, the control method of the energy storage system according to any one of claims 1 to 6 is implemented.

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