Backflow prevention control method and system for user side energy storage device

Abstract

The invention discloses an anti-countercurrent control method and system for a user side energy storage device, and belongs to the field of electric power, and the method comprises the following steps: collecting a voltage signal and a current signal at a common connection point; calculating an optimal discharge power threshold value of the energy storage device through the voltage signal and the current signal; the optimal discharge power is searched based on the optimal discharge power threshold value, the power direction is judged based on the optimal discharge power, and then output of the energy storage device is controlled or a grid-connected point switch is switched off. According to the method, the overall power transmission characteristic in a time period is not represented by the power transmission characteristic at a certain moment any more, the fluctuation characteristic of the power used by the user is fully considered, the situation that the energy storage income of the user side is reduced due to sudden power change is avoided, meanwhile, the switching frequency of an energy storage device is reduced, and the service life of an energy storage switch is prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of electric power, and in particular relates to a backflow prevention control method and system for a user-side energy storage device. Background Art

[0002] With policy support and the advancement of related technologies, the economic benefits of user-side energy storage are becoming more and more considerable. The existing user-side energy storage revenue is mainly obtained through peak-valley arbitrage, but relevant standards stipulate that user-side storage cannot have power reverse transmission. Therefore, anti-backflow devices are crucial in user-side energy storage.

[0003] At present, the energy storage backflow prevention device on the user side mostly adopts the method of adding a transformer. Users install voltage transformers (PT) and current transformers (CT) at the common connection point to collect voltage and current signals at the common connection point, so as to determine the power flow direction at the common connection point. Using this method, when the user is in the process of putting energy storage into production, the switch at the common connection point needs to be disconnected for safety reasons, which affects the power supply of the user.

[0004] For this type of backflow prevention device, the invention patent with application publication number CN118739435A discloses a user-side energy storage backflow prevention device, which collects voltage and current signals to obtain power signals at the common connection point to prevent backflow. When the backflow prevention device detects that the power reaches the set minimum threshold, it disconnects the energy storage switch, thereby preventing power backflow.

[0005] However, the energy storage anti-backflow devices currently used all use the method of installing PT and CT to collect the power flow at the public connection point. When installing the energy storage device using this method, the load at the public connection point needs to be powered off, which greatly increases the complexity of installation. Disconnecting the energy storage switch will also cause the power stored in the energy storage device to be unable to be transmitted to the user, reducing the energy storage benefits. The energy storage switch has a service life, and frequently turning on and off the energy storage switch to achieve the anti-backflow function will cause the energy storage switch to be damaged.

[0006] In addition, the power used by users has a fluctuating characteristic. The power transmission characteristics at a certain moment cannot represent the overall power transmission characteristics within a time period. Therefore, a sudden change in power at a certain moment will lead to a decrease in the energy storage benefits on the user side. On the other hand, Related patents are also being applied for to achieve the anti-backflow function. "A low-voltage anti-backflow switch and its control method" mainly targets the problem of self-generated backflow during distribution network maintenance. Voltage monitoring elements are added to the upper and lower terminals of the equipment to be tested, and the backflow phenomenon is prevented by monitoring the logic judgment of voltage and no voltage; "A dynamic adaptive control method for anti-reverse power of energy storage system" proposes an adaptive reverse power threshold control method. Different from the traditional anti-backflow control method, this control method learns the characteristics of the user's load curve and adaptively modifies the reverse power threshold to control the output of the energy storage system and ensure the continuity of the discharge of the energy storage system. However, these control methods all use the power transmission characteristics at a certain moment to represent the overall power transmission characteristics within the time period, which cannot be fully reflected, and the reverse flow phenomenon is prevented by turning on and off the energy storage switch. For users with frequent reverse flow, the number of energy storage switches turned on and off is large, so it is urgent to find a control method to reduce the number of on and off. Summary of the invention

[0007] The purpose of the present invention is to provide a backflow prevention control method and system for a user-side energy storage device, so as to solve the problems of frequent switching of the energy storage device by the existing backflow prevention device, resulting in reduced energy storage benefits and easy damage of the switch.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows: The present invention relates to a backflow prevention control method for a user-side energy storage device, which comprises the following steps: S1. Collect voltage and current signals at the common connection point; S2. Calculate the optimal discharge power threshold of the energy storage device through the voltage signal and the current signal; S3. Find the optimal discharge power based on the optimal discharge power threshold, determine the power direction based on the optimal discharge power, and then control the output of the energy storage device or disconnect the grid connection point switch.

[0009] Preferably, the optimal discharge power of the S2 energy storage device is calculated as follows: S2.1. Set the output adjustment accuracy of the energy storage device; S2.2. Calculate the power at the common connection point at time n and time n+1 respectively based on the voltage signal and current signal at time n and the voltage signal and current signal at time n+1; S2.3. Calculate the power increase at the common connection point using the formula: △pt= pt[n+1]- pt[n], Among them, △pt is the power increment, pt[n] and pt[n+1] represent the power at time n and time n+1 respectively; And when the calculated power increment is greater than 0, take △pt=0; S2.4. Real-time recording of the power pt[n] and power increment △pt at the common connection point at time n, and adaptive learning based on multiple sets of data to obtain the functional relationship between the power and power increment at each moment at the common connection point; S2.5. Calculate the optimal discharge power threshold at each moment based on the functional relationship between power and power increment. The calculation formula for the optimal discharge power threshold is: Pmin=k(pa-f(pt[n])), In the formula, Pmin is the optimal discharge power threshold, k is the threshold reliability coefficient, f(pt[n]) is the functional relationship between the power and power value at time n, and pa is the output regulation accuracy of the energy storage device.

[0010] Preferably, the specific steps of S3 controlling the output of the energy storage device or disconnecting the grid connection point switch are: When the power at the common connection point at time n satisfies pt[n]≥Pmin, the output of the energy storage device on the user side is maintained; when the power at the common connection point at time n satisfies pt[n]<Pmin, the output of the energy storage device on the user side is reduced.

[0011] Preferably, when S3 reduces the output of the user-side energy storage device, the output is adjusted to: pc[n+1]=pc[n]-([Pmin / pa]+1)*pa, In the formula, pc[n+1] is the energy storage output at time n+1 after adjustment, pc[n] is the user energy storage output before adjustment, and [] represents the rounding function; When the adjusted energy storage output at time n satisfies pc[n]>0, it is adjusted according to the calculated energy storage output value; when the adjusted energy storage output at time n satisfies pc[n]≤0, the grid connection point switch is disconnected.

[0012] Preferably, after collecting the voltage signal and the current signal, S1 converts the voltage signal and the current signal into an optical signal.

[0013] The present invention also relates to a backflow prevention control system of a user-side energy storage device, which comprises: An interface module, used for collecting voltage signals and current signals at a common connection point; The processor module is used to calculate the optimal discharge power threshold of the energy storage device through the voltage signal and the current signal; find the optimal discharge power based on the optimal discharge power threshold, determine the power direction based on the optimal discharge power, and then control the output of the energy storage device or disconnect the grid connection point switch.

[0014] Preferably, the interface module is also used to convert voltage signals and current signals into optical signals.

[0015] Preferably, the interface module and the processor module are connected via a transmission module, and the transmission module is used to transmit the optical signal to the processor module.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1. The anti-backflow control method of the user-side energy storage device involved in the present invention calculates the optimal discharge power of the energy storage device through voltage signals and current signals, makes a power direction judgment, and controls the output of the energy storage device or disconnects the grid connection point switch based on the optimal discharge power. This method no longer replaces the power at a certain moment with the average power, but always monitors the power situation at the public connection point to achieve real-time backflow prevention, fully considers the fluctuation characteristics of the power used by the user, avoids the reduction of the user-side energy storage benefit caused by power mutation, and reduces the switching frequency of the energy storage device to extend the service life of the energy storage switch.

[0017] 2. The anti-backflow control system of the user-side energy storage device involved in the present invention includes an interface module, a transmission module and a processor module. The interface module collects the voltage signal and the current signal at the common connection point and converts them into optical signals. The transmission module is used to transmit the optical signal to the processor module, and then perform anti-backflow control, which improves the reliability of data transmission and has strong anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a flow chart of a method for preventing backflow in a user-side energy storage device according to the present invention; Figure 2 Reading a process flow chart for a processor module; Figure 3 To prevent backflow control flow chart; Figure 4 This is a usage status diagram of the anti-backflow device of the user-side energy storage device. DETAILED DESCRIPTION

[0019] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0020] Example 1: Refer to the attached Figure 1 As shown, the present invention relates to a backflow prevention control method for a user-side energy storage device, which comprises the following steps: S1. Collecting voltage and current signals at the common connection point, where a comprehensive protection device is provided, reading the voltage and current signals on the comprehensive protection device, converting the voltage and current signals into optical signals, transmitting the optical signals to the processor module through a transmission module (transmission medium such as optical fiber), and then transmitting the voltage and current signals to the processor module; S2. After receiving the signal, the processor module determines whether the read information is correct and whether there is any data missing. If the data is missing, the interface module is requested to resend. If there is no data missing, the optimal discharge power threshold of the energy storage device is calculated through the voltage signal and the current signal. The specific steps include: S2.1. Set the output adjustment accuracy of the energy storage device; S2.2. Calculate the power at the common connection point at time n and time n+1 respectively based on the voltage signal and current signal at time n and the voltage signal and current signal at time n+1; S2.3. Calculate the power increase at the common connection point using the formula: △pt= pt[n+1]- pt[n], Among them, △pt is the power increment, pt[n] and pt[n+1] represent the power at time n and time n+1 respectively; And when the calculated power increment is greater than 0, take △pt=0; S2.4. Real-time recording of the power pt[n] and power increment △pt at the common connection point at time n, and adaptive learning based on multiple sets of data to obtain the functional relationship between the power and power increment at each moment at the common connection point; S2.5. Calculate the optimal discharge power threshold at each moment based on the functional relationship between power and power increment. The calculation formula for the optimal discharge power threshold is: Pmin=k(pa-f(pt[n])), In the formula, Pmin is the optimal discharge power threshold, k is the threshold reliability coefficient, f(pt[n]) is the functional relationship between the power and power value at time n, and pa is the output regulation accuracy of the energy storage device.

[0021] S3. Find the optimal discharge power based on the optimal discharge power threshold, determine the power direction based on the optimal discharge power, and then control the output of the energy storage device or disconnect the grid-connected switch. That is, when the optimal discharge power P>0, transmit the signal to the energy storage control module EMS to control the output of the energy storage PCS. When the optimal discharge power P≤0, disconnect the grid-connected switch. The specific steps are as follows: Figure 2 and Figure 3As shown: In this embodiment, the optimal discharge power can be divided into three categories, namely, the forward state, the critical state and the reverse state. The forward state means that the power at the common connection point flows to the user, the negative state means that the power at the common connection point flows to the grid side, and the critical state means that the power at the common connection point is zero; when in the forward state, the energy storage transmission power state is judged. If the energy storage device is discharged at full power, the output is maintained in this state; if the energy storage device has not reached the full power discharge state, the discharge power is appropriately increased; when in the critical state, the energy storage transmission power situation is read. If the transmission power is positive, the output of the energy storage device is appropriately reduced; if the transmission power is zero, the grid connection point switch is immediately disconnected; when in the reverse state, the power has been reversed, and the grid connection point switch needs to be disconnected immediately. The specific judgment basis is:

[0022] When the power at the common connection point at time n satisfies pt[n]≥Pmin, it indicates that it is in a forward state. At this time, the output of the energy storage device on the user side is maintained; When the power at the common connection point at time n satisfies pt[n]<Pmin, it is necessary to reduce the output of the energy storage device on the user side, and the output adjustment size is: pc[n+1]=pc[n]-([Pmin / pa]+1)*pa, In the formula, pc[n+1] is the energy storage output at time n+1 after adjustment, pc[n] is the user-side energy storage output before adjustment, and [] represents the rounding function. The adjusted energy storage output obtained in this step is the optimal discharge power, that is, P = pc[n+1]; When the adjusted energy storage output satisfies pc[n+1]>0, it indicates that it is in a critical state and is adjusted according to the calculated energy storage output value; when the adjusted energy storage output at time n satisfies pc[n]≤0, it indicates that it is in a reverse state and the grid connection point switch is disconnected.

[0023] Example 2: Refer to the attached Figure 4 As shown, the present invention also relates to a backflow prevention control system of a user-side energy storage device, which is connected to a comprehensive protection device at a common connection point, and comprises: An interface module is used to collect voltage signals and current signals at the common connection point, that is, to read voltage signals and current signals in the protection relay connected to the comprehensive protection device; the interface module is used to implement the function of step 1 of embodiment 1, and the interface module is also used to convert the voltage signal and the current signal into optical signals; The processor module is used to calculate the optimal discharge power threshold of the energy storage device through the voltage signal and the current signal; find the optimal discharge power based on the optimal discharge power threshold, determine the power direction based on the optimal discharge power, and then control the output of the energy storage device or disconnect the grid connection point switch. The processor module is used to implement the functions of step 2 and step 3 of embodiment 1.

[0024] The interface module and the processor module are connected via a transmission module, and the transmission module is used to transmit the optical signal to the processor module.

[0025] The present invention is described in detail above in conjunction with the embodiments, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preventing backflow of a user-side energy storage device, characterized in that: It includes the following steps: S1. Collect voltage and current signals at the common connection point; S2. Calculate the optimal discharge power threshold of the energy storage device through the voltage signal and the current signal; S3. Find the optimal discharge power based on the optimal discharge power threshold, determine the power direction based on the optimal discharge power, and then control the output of the energy storage device or disconnect the grid connection point switch.

2. The method for preventing backflow of a user-side energy storage device according to claim 1, characterized in that: The optimal discharge power threshold of the S2 energy storage device is calculated as follows: S2.

1. Set the output adjustment accuracy of the energy storage device; S2.

2. Calculate the power at the common connection point at time n and time n+1 respectively based on the voltage signal and current signal at time n and the voltage signal and current signal at time n+1; S2.

3. Calculate the power increase at the common connection point using the formula: △pt= pt[n+1]- pt[n], Among them, △pt is the power increment, pt[n] and pt[n+1] represent the power at time n and time n+1 respectively; And when the calculated power increment is greater than 0, take △pt=0; S2.

4. Real-time recording of the power pt[n] and power increment △pt at the common connection point at time n, and adaptive learning based on multiple sets of data to obtain the functional relationship between the power and power increment at each moment at the common connection point; S2.

5. Calculate the optimal discharge power threshold at each moment based on the functional relationship between power and power increment. The calculation formula for the optimal discharge power threshold is: Pmin=k(pa-f(pt[n])), In the formula, Pmin is the optimal discharge power threshold, k is the threshold reliability coefficient, f(pt[n]) is the functional relationship between the power and power value at time n, and pa is the output regulation accuracy of the energy storage device.

3. The method for preventing backflow of a user-side energy storage device according to claim 2, characterized in that: The specific steps of S3 controlling the output of the energy storage device or disconnecting the grid connection point switch are: When the power at the common connection point at time n satisfies pt[n]≥Pmin, the output of the energy storage device on the user side is maintained; when the power at the common connection point at time n satisfies pt[n]<Pmin, the output of the energy storage device on the user side is reduced.

4. The method for preventing backflow of a user-side energy storage device according to claim 3, characterized in that: When S3 reduces the output of the energy storage device on the user side, the output adjustment magnitude is: pc[n+1]=pc[n]-([Pmin / pa]+1)*pa, In the formula, pc[n+1] is the adjusted energy storage output at time n+1, pc[n] is the user energy storage output at time n, and [] represents the rounding function; When the adjusted energy storage output at time n satisfies pc[n]>0, it is adjusted according to the calculated energy storage output value; when the adjusted energy storage output at time n satisfies pc[n]≤0, the grid connection point switch is disconnected.

5. The method for preventing backflow of a user-side energy storage device according to claim 1, characterized in that: After S1 collects the voltage signal and the current signal, it converts the voltage signal and the current signal into an optical signal.

6. A backflow prevention control system for a user-side energy storage device, characterized in that: It includes: An interface module, used for collecting voltage signals and current signals at a common connection point; The processor module is used to calculate the optimal discharge power threshold of the energy storage device through the voltage signal and the current signal; find the optimal discharge power based on the optimal discharge power threshold, determine the power direction based on the optimal discharge power, and then control the output of the energy storage device or disconnect the grid connection point switch.

7. The anti-backflow control system of the user-side energy storage device according to claim 6, characterized in that: The interface module is also used to convert voltage signals and current signals into optical signals.

8. The anti-backflow control system of the user-side energy storage device according to claim 7, characterized in that: The interface module and the processor module are connected via a transmission module, and the transmission module is used to transmit the optical signal to the processor module.

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