Energy storage control method for preventing countercurrent and computer device

Abstract

The invention relates to an energy storage control method for preventing countercurrent and a computer device, and belongs to the field of power systems. And when the power grid output power is greater than or equal to the maximum energy storage output power, the stored energy is output according to the maximum output power. When the electricity meter power is larger than or equal to the dead-zone power threshold value and smaller than the maximum energy storage output power for the first time, and the electricity meter power is not larger than or equal to the maximum energy storage output power, the stored energy is output according to the value obtained by subtracting the set anti-fluctuation power from the electricity meter power; when the electric meter power is greater than or equal to a dead-zone power threshold value and less than a set energy storage maximum output power for the first time and countercurrent occurs, the stored energy is output according to a value obtained by adding the electric meter power and the last energy storage output power; if the electricity meter power is larger than or equal to the dead-zone power threshold value and smaller than the maximum energy storage output power and the duration is larger than the set value continuously, the stored energy is output after being subjected to amplitude limiting according to the value obtained by adding the electricity meter power and the last energy storage output power, and stable operation of the system can be ensured through flexible selection according to the actual situation.

Description

Technical Field

[0001] The present invention relates to an energy storage control method and a computer device for preventing reverse current, belonging to the field of power systems. Background Art

[0002] With the wide application of renewable energy and the continuous development of distributed generation technology, low-voltage distributed energy storage systems play an increasingly important role in power systems. However, in low-voltage distributed energy storage systems, due to the uncertainty of power flow, reverse current phenomena may occur, that is, electric energy flows reversely from the low-voltage side into the power grid, which not only affects the stable operation of the power grid, but may also cause damage to energy storage devices and electrical equipment. Therefore, effective reverse current prevention control methods play a very important role in the safe and stable operation of low-voltage distributed energy storage systems.

[0003] Existing technologies usually adopt reverse current prevention devices or controllers to achieve this goal, and these technologies often have problems such as slow response speed, low control accuracy, and poor adaptability. Specifically, most existing reverse current prevention devices rely on simple current detection and comparison mechanisms. When reverse current is detected, the discharge of the energy storage system is cut off or restricted to prevent reverse current. However, this method often leads to unstable discharge processes of the energy storage system and cannot be dynamically adjusted according to the actual needs of the power grid.

[0004] In addition, although some advanced reverse current prevention control systems, such as reverse current prevention control devices based on model predictive control, adaptive control, etc., can achieve more refined control, these devices often have complex control logics, high costs, and require professional technical personnel for maintenance and debugging, which is not conducive to wide application in low-voltage distributed energy storage systems. Summary of the Invention

[0005] The purpose of the present invention is to provide an energy storage control method and a computer device for preventing reverse current, so as to solve the problem of complex control strategies adopted during the operation of reverse current prevention devices.

[0006] To achieve the above purpose, the solution of the present invention includes: An energy storage control method for preventing reverse current according to the present invention includes the following steps: 1) When the energy storage is in the discharge state, obtain the meter power reflecting the exchanged power between the power grid and the load side; 2) If the meter power is greater than or equal to the set maximum energy storage output power, use the set maximum energy storage output power as the current energy storage output power; When the power of the electricity meter is greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power for the first time, and the power of the electricity meter has not been greater than or equal to the set maximum energy storage output power before, then the value obtained by subtracting the set anti - fluctuation power from the power of the electricity meter is used as the energy storage output power for this time; If the power of the electricity meter is greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power for the first time, and there has been a reverse current before and the energy storage has been regulated, then the value obtained by adding the power of the electricity meter and the previous energy storage output power is used as the energy storage output power for this time; If the power of the electricity meter continuously satisfies being greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power and the continuous time is greater than the set continuous - time threshold, then the result of adding the power of the electricity meter and the previous energy storage output power is limited by an upper limit and used as the energy storage output power for this time; The upper - limit limitation means that if the result before limitation is greater than the set maximum energy storage output power, then the result after limitation is set to the set maximum energy storage output power; 3) Control the energy storage discharge according to the energy storage output power for this time.

[0007] Furthermore, if a reverse - current phenomenon with a reverse - current current less than or equal to the set maximum reverse - current threshold occurs for the first time, then the result of adding the set maximum energy storage output power and the power of the electricity meter and then subtracting the anti - fluctuation power set value is limited by a lower limit and used as the energy storage output power for this time; If a reverse - current phenomenon with a reverse - current current less than or equal to the set maximum reverse - current threshold occurs and it is not the first time, then the result of adding the power of the electricity meter and the previous energy storage output power and then subtracting the dead - zone power set value is limited by a lower limit and used as the energy storage output power for this time; Among them, the lower - limit limitation means that if the result before limitation is less than 0, then the result after limitation is set to 0.

[0008] Furthermore, if the power of the electricity meter is less than the set anti - reverse - current protection power threshold, then it is determined that a reverse current has occurred.

[0009] Furthermore, if a reverse - current phenomenon with a reverse - current current greater than the set maximum reverse - current threshold occurs, then the connection between the energy storage and the power grid is cut off.

[0010] A computer device of the present invention includes a processor, and the processor executes computer instructions for the above - mentioned energy - storage control method for preventing reverse current.

[0011] The beneficial effects of the present invention are: The energy storage control method and computer device for preventing reverse current of the present invention obtain the meter power reflecting the exchanged power between the power grid and the load side when the energy storage is in the discharge state. When the meter power is greater than or equal to the set maximum energy storage output power, the set maximum energy storage output power is used as the energy storage output power for this time, thereby reducing the power transmitted from the power grid to the load side. When the meter power is greater than or equal to the set dead zone power threshold and less than the set maximum energy storage output power and this is the first occurrence, and the meter power greater than or equal to the set maximum energy storage output power has not occurred before, the value obtained by subtracting the set anti-fluctuation power from the meter power is used as the energy storage output power for this time. The energy storage output according to the meter power can reduce the power output of the power grid while avoiding reverse current and reducing power fluctuations in the power grid. When the meter power is greater than or equal to the set dead zone power threshold and less than the set maximum energy storage output power and this is the first occurrence, and reverse current has occurred before, the value obtained by adding the meter power and the previous energy storage output power is used as the energy storage output power for this time. If the meter power is continuously greater than or equal to the set dead zone power threshold and less than the set maximum energy storage output power and the duration is greater than the set duration threshold, the result of adding the meter power and the previous energy storage output power is limited by an upper limit and then used as the energy storage output power for this time. The energy storage discharge is controlled according to the energy storage output power for this time. The upper limit limitation means that if the result before limitation is greater than the set maximum energy storage output power, the result after limitation is set to the set maximum energy storage output power. The energy storage output power is appropriately adjusted within a small range according to the power output of the power grid, so that the power output of the power grid is within a reasonable range. The energy storage control method and computer device for preventing reverse current of the present invention adopt a variety of anti-reverse current control strategies, which can be flexibly selected according to the actual situation, effectively avoid the generation of reverse current, avoid the impact of reverse current on the power grid, ensure the stable operation of the system, improve the reliability of the system, and can be realized only by software upgrade, reducing the cost and having a broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flowchart of the energy storage control method for preventing reverse current of the present invention; Figure 2 is a schematic diagram of the anti-reverse current control strategy. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described in detail clearly and completely below with reference to the accompanying drawings and embodiments.

[0014] The concept of the present invention lies in that when the energy storage is in the discharging state, the meter power for reflecting the exchanged power between the power grid and the load side is obtained; the reverse current that may occur in the power grid is avoided according to the meter power: when the meter power is greater than or equal to the set maximum output power of the energy storage, the set maximum output power of the energy storage is used as the output power of the energy storage for this time; when the meter power is greater than or equal to the set dead zone power threshold and less than the set maximum output power of the energy storage and it appears for the first time, and the meter power has not been greater than or equal to the set maximum output power of the energy storage before, the value obtained by subtracting the set anti-fluctuation power from the meter power is used as the output power of the energy storage for this time; when the meter power is greater than or equal to the set dead zone power threshold and less than the set maximum output power of the energy storage and it appears for the first time, and there has been a reverse current before and the energy storage has been regulated, the value obtained by adding the meter power and the previous output power of the energy storage is used as the output power of the energy storage for this time; when the meter power is continuously greater than or equal to the set dead zone power threshold and less than the set maximum output power of the energy storage and the duration is greater than the set duration threshold, the result obtained by adding the meter power and the previous output power of the energy storage is limited by an upper limit and used as the output power of the energy storage for this time; the upper limit limitation means that if the result before the limitation is greater than the set maximum output power of the energy storage, the result after the limitation is made to be the set maximum output power of the energy storage. The energy storage discharging is controlled according to the output power of the energy storage for this time.

[0015] An implementation manner of an energy storage control method for preventing reverse current: As Figure 1 shown, the energy storage reverse current prevention control method of the present invention includes the following steps: 1) Monitor the current and voltage of the low-voltage side distributed energy storage system in real time.

[0016] Install a current sensor and a voltage sensor in the energy storage system, collect the current and voltage signals of the energy storage system in real time, and transmit these signals to the control unit. The control unit calculates the magnitude and direction of the current according to the collected current and voltage signals. If it is detected that the current flows from the power grid to the energy storage system, it is a positive current; if the current flows from the energy storage system to the power grid, it is a reverse current.

[0017] Set a meter between the load side and the power grid, and the power indication of the meter is used to represent the power consumed by the load side from the power grid. When the power indication is greater than 0, it means that the current flows from the power grid to the load side, that is, the load side is consuming the power of the power grid, and when the power indication is less than 0, it means that the current flows from the load side to the power grid, that is, a reverse current appears at this time.

[0018] As a specific embodiment, the control unit can be a microprocessor, a single-chip microcomputer, and other programmable controllers, etc.; the current sensor can be a current transformer or a Hall sensor, etc.

[0019] 2) Execute the reverse current prevention control strategy according to the power output of the power grid.

[0020] When the energy storage is in the discharging state, obtain the meter power that reflects the exchanged power between the power grid and the load side; when there is a tendency of reverse current, control the inverter of the energy storage system to use pulse width modulation (PWM) technology to reduce the output power of the energy storage system. Specifically: if the meter power is greater than or equal to the set maximum output power of the energy storage, then use the set maximum output power of the energy storage as the output power of the energy storage for this time to control the energy storage discharge. The occurrence of this situation indicates that the power grid is generating more power at this time. In order to minimize the power generation of the power grid and avoid reverse current at the same time, the energy storage can be directly output according to the set maximum output power of the energy storage.

[0021] If the meter power is greater than or equal to the set dead zone power threshold and less than the set maximum output power of the energy storage and this is the first occurrence, and the meter power has not been greater than or equal to the set maximum output power of the energy storage before, then use the calculated value obtained by subtracting the set anti-fluctuation power from the meter power as the output power of the energy storage for this time to control the energy storage discharge. In this case, theoretically, the energy storage can output according to the meter power to reduce the power generation of the power grid and avoid reverse current at the same time, but the actual situation is not like this. The actual situation is that the meter power will fluctuate, that is, the meter power may change during the execution of this calculation process and is not stable around a certain value. Therefore, a set anti-fluctuation power is set at this time to make the energy storage output less, in case reverse current occurs when the energy storage directly outputs according to the meter power.

[0022] If the meter power is greater than or equal to the set dead zone power threshold and less than the set maximum output power of the energy storage and this is the first occurrence, and there has been reverse current before and the energy storage has been regulated, then use the calculated value obtained by adding the meter power and the previous output power of the energy storage as the output power of the energy storage for this time to control the energy storage discharge. Since the energy storage has been regulated, it cannot be regulated based on the set maximum output power of the energy storage but based on the previous output power of the energy storage. Moreover, this situation corresponds to the situation where after the reverse current phenomenon occurs and the energy storage is regulated, the meter power gradually rises from 0 to greater than the set dead zone power threshold and less than the set maximum output power of the energy storage. In this case, theoretically, the meter power is a value relatively close to the set dead zone power threshold and will not be particularly large. Therefore, the result after adding the meter power and the previous output power of the energy storage will not be too large, and there will be no situation where the result after addition is greater than the set maximum output power of the energy storage. Therefore, directly use the calculated result of adding the meter power and the previous output power of the energy storage as the output power of the energy storage for this time.

[0023] If the power of the electricity meter continuously satisfies the condition that it is greater than or equal to the set dead - zone power threshold (a value greater than 0 but not much larger) and less than the set maximum energy storage output power, and the duration is greater than the set duration threshold, then the result of adding the power of the electricity meter and the previous energy storage output power is limited by an upper limit to obtain the current energy storage output power. The upper limit means that if the result before limiting is greater than the set maximum energy storage output power, the result after limiting is set to the set maximum energy storage output power. This situation corresponds to the case where the power of the electricity meter is always greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power. The energy storage output may increase and even exceed the set maximum energy storage output power. Therefore, the result of adding the power of the electricity meter and the previous energy storage output power is limited.

[0024] Moreover, it should be noted that there are also some situations. When the power of the electricity meter is in the range from 0 to the set dead - zone power threshold, no regulation is performed on the energy storage output, that is, the energy storage continues to output according to the previous energy storage output power. It also includes the situation where the power of the electricity meter is greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power, but the power of the electricity meter has been greater than or equal to the set maximum energy storage output power before. At this time, no regulation is performed on the energy storage output either. This is because frequent changes in the energy storage output will affect the life and performance of the energy storage.

[0025] When the anti - reverse - flow strategy is specifically implemented, three flag bits are set, namely the first flag bit flag1, the second flag bit flag2, and the third flag bit flag3. In the initial state, flag1, flag2, and flag3 are all 0. The first flag bit indicates that when flag1 = 0, it means that the power of the electricity meter being greater than or equal to the set maximum energy storage output power has not occurred; when flag1 = 1, it means that the power of the electricity meter being greater than or equal to the set maximum energy storage output power has occurred. The second flag bit indicates that when flag2 = 0, it means that the power of the electricity meter being greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power has never occurred; when flag2 = 1, it means that the power of the electricity meter being greater than or equal to the set dead - zone power threshold and less than the set maximum energy storage output power has occurred. The third flag bit indicates that when flag3 = 0, it means that the power of the electricity meter being less than the reverse - flow determination set value, that is, reverse - flow in the power grid has never occurred; when flag3 = 1, it means that the power of the electricity meter being less than the reverse - flow determination set value, that is, reverse - flow in the power grid has occurred.

[0026] In addition, Pset is used to represent the set maximum energy storage output power, Ppro is used to represent the set anti - reverse - flow protection threshold, Pload is used to represent the power reading of the electricity meter, Pref is used to represent the energy storage output power, and Pold is used to temporarily store the corresponding energy storage output power Pref. As Figure 2 shown, after initializing lag1, flag2, and flag3, the specific implementation includes the following steps: 1) Detect whether the power reading Pload of the electricity meter is greater than or equal to the set maximum energy storage output power Pset. At this time, the power output from the power grid to the load side is too large, and the power output of the power grid needs to be reduced.

[0027] As Figure 2 shown, if the condition is met, set the output power Pref of the energy storage to the set maximum energy storage output power Pset to reduce the power output from the power grid to the load, and use Pold to save the energy storage output power Pref at this time; set the first flag bit flag1 to 1 and the second flag bit flag2 to 0.

[0028] 2) Detect whether the power reading Pload of the electricity meter is greater than or equal to the set dead zone power threshold and less than the set maximum energy storage output power Pset.

[0029] If the corresponding condition is met, within one minute, determine whether the second flag bit flag2 is 0 or the third flag bit flag3 is 1: When the second flag bit flag2 is 0, when the first flag bit flag1 is 0, set the inverter output power Pref to the operation value of the current power reading Pload of the electricity meter minus the anti-fluctuation power, to reduce the power output of the power grid and prevent the power output of the power grid from fluctuating and affecting the power grid; when the third flag bit flag3 is 1, at this time, set the output power Pref to the operation value of the previous energy storage output power Pold plus the current power reading Pload of the electricity meter, to reduce the power output of the power grid.

[0030] Save the inverter output power Pref at this time to Pold, and set the second flag bit flag2 to 1.

[0031] When the timing reaches 1 minute, set the energy storage output power Pref to the operation value of Pold plus the current electricity meter reading Pload, thereby reducing the power output of the power grid.

[0032] Determine whether the energy storage output power Pref at this time is greater than the set maximum energy storage output power Pset; if the condition is met, set the energy storage output power Pref to the value of the set maximum energy storage output power Pset and save it to Pold.

[0033] As a specific embodiment, the anti-fluctuation power can be set to 5 Kw.

[0034] When reverse current is detected, start the anti-counterflow control strategy; in the present invention, the anti-counterflow control strategy can be selected in the following ways according to the actual situation: Method 1: Adjust the output power of the energy storage system.

[0035] When the reverse current in the power grid has not exceeded the set maximum reverse current threshold, adjust the output power of the energy storage system to reduce and eliminate the reverse current in the power grid.

[0036] Judge whether the power indication Pload of the electric meter is less than the set anti-reverse protection power threshold Ppro.

[0037] If the power indication Pload of the electric meter is greater than the set anti-reverse protection power threshold Ppro, that is, there is a reverse current in the power grid. At this time, when the third flag bit flag3 is 0, the energy storage output power Pref is set to the set maximum energy storage output power Pset plus the operation value obtained by subtracting the power indication Pload of the electric meter from the set dead zone power threshold to increase the power output of the power grid; when the third flag bit flag3 is not 0, the energy storage output power is set to Pold plus the operation value obtained by subtracting the power indication Pload of the electric meter from the set dead zone power threshold.

[0038] When the energy storage output power Pref is less than 0, the energy storage output power is set to 0 to prevent the power on the load side from flowing back into the energy storage system and causing damage to the energy storage system, and the value of this energy storage output power Pref is saved to Pold.

[0039] As an embodiment of the set dead zone power threshold, it can be set to 5kw.

[0040] Method 2: Disconnect the energy storage system from the power grid.

[0041] When the reverse current is large and exceeds the set maximum reverse current threshold, immediately disconnect the switch between the energy storage system and the power grid to prevent the excessive reverse current from having a greater impact on the power grid.

[0042] As a specific embodiment, the switch can be implemented by a circuit breaker, a contactor or other devices to connect and disconnect the energy storage system from the power grid.

[0043] The above anti-reverse control strategy and reverse current elimination strategy are executed in real time according to the reverse current situation.

[0044] An implementation mode of a computer device: The computer device of the present invention includes a processor, and the processor executes a computer program stored in a memory to implement the steps of the above-mentioned energy storage control method for preventing reverse current.

[0045] The energy storage control method and computer device for preventing reverse current of the present invention monitor the current and voltage in the power grid and energy storage in real time, and adopt corresponding reverse current prevention control strategies according to the output power of the power grid when there is no reverse current, which can be flexibly selected according to the actual situation, effectively reducing the occurrence of reverse current in the power grid and reducing the impact on the power grid. When the reverse current phenomenon is found, a relatively simple and effective reverse current elimination control strategy is adopted, improving the safety and stability of the power grid system. Without additional hardware devices, it can be achieved only through software upgrade, reducing costs and having broad application prospects.

[0046] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be subject to the claims. All equivalent structural changes made by using the content of the specification and drawings of the present invention shall be equally included in the protection scope of the present invention.

Claims

1. A method for energy storage control for preventing backflow, characterized in that, It includes the following steps: 1) When the energy storage is in the discharging state, obtain the meter power used to reflect the exchanged power between the power grid and the load side; 2) If the meter power is greater than or equal to the set maximum output power of the energy storage, then use the set maximum output power of the energy storage as the output power of the energy storage for this time; When the meter power is greater than or equal to the set dead - zone power threshold and less than the set maximum output power of the energy storage and it appears for the first time, and the meter power has not been greater than or equal to the set maximum output power of the energy storage before, then use the value obtained by subtracting the set anti - fluctuation power from the meter power as the output power of the energy storage for this time; If the meter power is greater than or equal to the set dead - zone power threshold and less than the set maximum output power of the energy storage and it appears for the first time, and there has been a reverse current before and the energy storage has been regulated, then use the value obtained by adding the meter power and the previous output power of the energy storage as the output power of the energy storage for this time; If it continuously appears that the meter power is greater than or equal to the set dead - zone power threshold and less than the set maximum output power of the energy storage and the duration is greater than the set duration threshold, then use the result of adding the meter power and the previous output power of the energy storage after upper - limit clipping as the output power of the energy storage for this time; Upper - limit clipping means that if the result before clipping is greater than the set maximum output power of the energy storage, then make the result after clipping be the set maximum output power of the energy storage; 3) Control the energy storage discharge according to the output power of the energy storage for this time.

2. The energy storage control method for preventing backflow according to claim 1, wherein If a reverse - current phenomenon where the reverse - current is less than or equal to the set maximum reverse - current threshold appears for the first time, then use the result of adding the set maximum output power of the energy storage and the meter power and then subtracting the anti - fluctuation power set value after lower - limit clipping as the output power of the energy storage for this time; If a reverse - current phenomenon where the reverse - current is less than or equal to the set maximum reverse - current threshold appears and it is not the first time, then use the result of adding the meter power and the previous output power of the energy storage and then subtracting the dead - zone power set value after lower - limit clipping as the output power of the energy storage for this time; Among them, lower - limit clipping means that if the result before clipping is less than 0, then make the result after clipping be 0.

3. The energy storage control method for preventing backflow according to claim 1 or 2, characterized in that, If the meter power is less than the set anti - reverse - current protection power threshold, then it is determined that a reverse current occurs.

4. The energy storage control method for preventing backflow according to claim 1, wherein If a reverse - current phenomenon where the reverse - current is greater than the set maximum reverse - current threshold appears, then cut off the connection between the energy storage and the power grid.

5. A computer device, comprising a processor, characterized in that, The processor executes computer instructions to implement the energy - storage control method for preventing reverse current as described in any one of claims 1 to 4 above.

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