Wiring sequence identification method for a three-phase electric meter, and three-phase inverter

Abstract

The present application provides a wiring sequence identification method for a three-phase electric meter, and a three-phase inverter. The method comprises the following steps: using a three-phase electric meter to acquire a first power of each phase at a power grid output end when a three-phase inverter is in an off-grid state; controlling the three-phase inverter to enter a second mode, wherein in the second mode, the three-phase inverter is in a grid-connected state and outputs in a feed-in direction according to a preset power reference value of each corresponding phase, and in the second mode, the preset power reference values of the phases of the three-phase inverter are different; using the three-phase electric meter to acquire a second power of each phase at the power grid output end in the second mode; and on the basis of the first power of each phase and the second power of each phase at the power grid output end, obtaining a power change amount of each phase, and if the deviation between the power change amount of each phase and the preset power reference value of the corresponding phase is within a preset range, determining that the configuration of the three-phase electric meter is correct. The wiring sequence identification method for a three-phase electric meter provided in the present application can implement automatic detection of whether the wiring of three-phase electric meters is correct.

Description

Three-phase electricity meter wiring sequence identification method and three-phase inverter

[0001] This application claims priority to Chinese Patent Application No. 202410987362.8, filed on July 22, 2024, entitled “Three-phase meter wiring sequence identification method and three-phase inverter”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of inverter technology, and in particular to a three-phase meter wiring sequence identification method and a three-phase inverter. Background Technology

[0003] In energy control systems, such as photovoltaic systems, energy storage systems, or photovoltaic-storage systems, electricity meters need to be installed. During installation, issues such as incorrect wiring sequence or reversed internal current sensor orientation can easily occur. This not only leads to errors in real-time monitoring data but may also cause system malfunctions. Therefore, it is necessary to check the wiring sequence of three-phase electricity meters before installation.

[0004] Currently, the installation of three-phase electricity meters is mainly carried out by professional technicians who operate according to the installation guidelines provided by the meter manufacturer. However, since the meter is usually an independent component and is far from the inverter, the installers only follow the wiring sequence of the inverter entering the house and the phase sequence guidance provided by the meter to complete the matching installation between the meter and the inverter. In this process, problems such as incorrect wiring sequence or reversed internal current sensor connection are prone to occur. Summary of the Invention

[0005] In view of the above-mentioned problems in related technologies, this application provides a three-phase electricity meter wiring sequence identification method and a three-phase inverter, which can automatically detect whether the wiring of the three-phase electricity meter is correct.

[0006] To achieve the above objectives, this application provides a method for identifying the wiring sequence of a three-phase electricity meter. The three-phase electricity meter can be electrically connected to the power grid to collect the three-phase power output from the grid. The three-phase electricity meter can also be communicatively connected to a three-phase inverter, which can perform both grid-connected and off-grid operations. The method includes the following steps:

[0007] Using a three-phase meter, when the three-phase inverter is in the first mode, the first power of each phase at the grid output terminal is collected. When the three-phase inverter is in the first mode, the three-phase inverter is in an off-grid state.

[0008] The three-phase inverter is controlled to enter the second mode. When the three-phase inverter is in the second mode, it is in grid-connected state. Furthermore, each phase of the three-phase inverter outputs power in the grid direction according to the preset power reference value of the corresponding phase. In the second mode, the preset power reference values ​​of each phase of the three-phase inverter are different.

[0009] Using a three-phase meter, with the three-phase inverter in its second mode, the second power of each phase at the grid output is collected;

[0010] Based on the first power and second power of each phase at the power grid output, the power change of each phase is obtained. If the deviation between the power change of each phase and the preset power reference value of the corresponding phase is within the preset range, it is determined that the three-phase meter wiring sequence is set correctly.

[0011] This three-phase meter wiring sequence identification method controls the three-phase inverter to operate in an off-grid first mode and a grid-connected second mode. In the second mode, the preset power reference values ​​for each phase are different. The method obtains the power change of each phase based on the first and second power values ​​of each phase at the grid output terminal in the first and second modes. Then, it determines whether the wiring sequence of the three-phase meter is set correctly based on whether the deviation between the power change of each phase and the preset power reference value of the corresponding phase is within a preset range. This achieves automatic detection of whether the wiring of the three-phase meter is correct.

[0012] This application also provides a three-phase inverter for use in an energy management system, the energy management system including a three-phase meter and a three-phase inverter;

[0013] The DC side of a three-phase inverter is used to connect to a DC source, and the AC side is used to connect to the grid. The three-phase inverter can achieve grid-connected and off-grid operation.

[0014] The three-phase meter is connected to the power grid and is used to collect the three-phase power at the output of the power grid.

[0015] The three-phase inverter also includes a control module, which is used for:

[0016] The three-phase inverter is controlled in either the first mode of being off-grid or the second mode of being on-grid. In the second mode, each phase of the three-phase inverter is controlled to output power in the direction of the grid feed according to a preset power reference value. In the second mode, the preset power reference values ​​of each phase of the three-phase inverter are different.

[0017] The control module is also used to collect the first power of each phase at the grid output terminal when the three-phase inverter is in the first mode, and to collect the second power of each phase at the grid output terminal when the three-phase inverter is in the second mode.

[0018] The control module is also used to obtain the power change of each phase based on the first power and second power of each phase at the power grid output. If the deviation between the power change of each phase and the preset power reference value of the corresponding phase is within the preset range, the control module determines that the three-phase meters are set correctly.

[0019] The control module of this three-phase inverter can control the three-phase inverter to operate in the first off-grid mode and the second grid-connected mode. In the second mode, the preset power reference values ​​of each phase are different. Based on the first power and second power of each phase at the grid output terminal in the first and second modes, the module obtains the power change of each phase. Then, based on whether the deviation between the power change of each phase and the preset power reference value of the corresponding phase is within the preset range, the module determines whether the wiring sequence of the three-phase electricity meter is set correctly, thereby realizing the automatic detection of whether the wiring of the three-phase electricity meter is correct.

[0020] This application also provides a three-phase electricity meter wiring sequence identification device, including:

[0021] The first power acquisition module is used to acquire the first power of each phase at the grid output terminal using a three-phase meter when the three-phase inverter is in the first mode. The three-phase inverter is in the off-grid state when it is in the first mode.

[0022] The second mode module is used to control the three-phase inverter to enter the second mode. When the three-phase inverter is in the second mode, it is in grid-connected state, and each phase of the three-phase inverter outputs power in the grid direction according to the preset power reference value of the corresponding phase. In the second mode, the preset power reference values ​​of each phase of the three-phase inverter are different.

[0023] The second power acquisition module is used to acquire the second power of each phase at the grid output terminal using a three-phase meter when the three-phase inverter is in the second mode.

[0024] The judgment module is used to obtain the power change of each phase based on the first power and second power of each phase at the power grid output terminal. If the deviation between the power change of each phase and the preset power reference value of the corresponding phase is within the preset range, it is judged that the three-phase meter wiring sequence is set correctly.

[0025] This application also provides a control module, including: a processor, and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the three-phase meter line sequence identification method as described above.

[0026] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the three-phase meter line sequence identification method described above.

[0027] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the three-phase meter line sequence identification method as described above. Attached Figure Description

[0028] Figure 1 is a schematic diagram of the connection relationship between the three-phase inverter, the three-phase meter, and the power grid when the three-phase meter is correctly installed, according to an embodiment of this application.

[0029] Figure 2 is a flowchart of the three-phase meter wiring sequence identification method provided in an embodiment of this application;

[0030] Figure 3 is a schematic diagram of the U-phase current sensor of the three-phase meter provided in the embodiment of this application when it is connected in reverse.

[0031] Figure 4 is a schematic diagram showing the incorrect wiring sequence of the U-phase current sensor and V-phase current sensor in the three-phase meter provided in the embodiment of this application.

[0032] Figure 5 is a schematic diagram of a three-phase meter provided in this application where the current sensor direction and wiring sequence are simultaneously incorrectly installed.

[0033] Figure 6 is a schematic diagram of the energy management system provided in an embodiment of this application. Detailed Implementation

[0034] The present application will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application. Any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the protection scope of the present application.

[0035] The purpose of this application is to provide a method for identifying the wiring sequence of a three-phase electricity meter, which can automatically detect whether the meter wiring is correct. The detection operation is simple and quick, and can improve detection efficiency and accuracy.

[0036] For ease of explanation, this application first describes the connection relationship between the three-phase inverter, the three-phase meter, and the power grid. As shown in Figure 1, it illustrates the connection relationship between the three-phase inverter (Figure 1 uses a three-phase energy storage inverter as an example), the three-phase meter, and the power grid when the three-phase meter is correctly installed. As shown in Figure 1, the grid side includes the grid inlet, the incoming circuit breaker, and the existing incoming electricity meter. The existing incoming electricity meter is connected to the three-phase meter and the three-phase energy storage inverter via each phase. Taking a three-phase four-wire system as an example, the grid side includes phase A, phase B, phase C, and neutral (N). The DC side of the three-phase inverter is used to connect to a DC source, which can be an energy storage battery and / or a photovoltaic array. The left side of the three-phase inverter in Figure 1 represents the DC side. The AC side of the three-phase inverter has four terminals, denoted as R, S, T, and N. The R terminal connects to phase A, the S terminal to phase B, the T terminal to phase C, and the N terminal to neutral (N). During operation, the three-phase meter connects to the grid output to collect the three-phase power output. Specifically, the three-phase meter includes a voltage sampling terminal and three current sensors. The voltage sampling terminal of the three-phase meter can be represented by UVW. The three-phase electricity meter can also communicate with the three-phase inverter, sending the collected data to the inverter for energy management. For ease of explanation, in this embodiment, the current sensor connected to the U-phase voltage sampling terminal is called the U-phase current sensor, the current sensor connected to the V-phase voltage sampling terminal is called the V-phase current sensor, and the current sensor connected to the W-phase voltage sampling terminal is called the W-phase current sensor. As shown in Figure 1, the three rectangles connected to the three-phase electricity meter represent the three current sensors. Each phase current sensor has a reference direction; in this application, the arrow direction in Figure 1 represents the positive current direction.

[0037] As shown in Figure 1, assuming the three-phase electricity meter is correctly installed, the following conditions should be met when setting up the three-phase electricity meter:

[0038] 1) The voltage line sequence UVW of the three-phase meter must be consistent with the UVW line sequence of its own current sensor;

[0039] 2) The installation direction of the current sensor of each phase of the three-phase meter needs to be the same as the set reference direction; In this application, the current flowing to the power grid is used as the positive direction for the explanation of the principle of this application.

[0040] 3) The voltage line sequence UVW of the three-phase meter needs to be consistent with the RST line sequence on the AC side of the three-phase inverter.

[0041] To verify the correct installation of a three-phase electricity meter, this application provides a three-phase electricity meter wiring sequence identification method applied to a three-phase inverter capable of both grid-connected and off-grid operation. Figure 2 is a flowchart of the three-phase electricity meter wiring sequence identification method provided in this application. As shown in Figure 2, the three-phase electricity meter wiring sequence identification method provided in this application includes the following steps:

[0042] Step S11: Using a three-phase meter, with the three-phase inverter in the first mode, collect the first power of each phase at the grid output terminal. The three-phase inverter is in the first mode and is in an off-grid state.

[0043] Step S12: Control the three-phase inverter to enter the second mode. When the three-phase inverter is in the second mode, it is in grid-connected state. Furthermore, each phase of the three-phase inverter outputs power in the grid direction according to the preset power reference value. In the second mode, the preset power reference values ​​of each phase of the three-phase inverter are different.

[0044] Step S13: Using a three-phase meter, with the three-phase inverter in the second mode, collect the second power of each phase at the grid output terminal;

[0045] Step S14: Based on the first power and second power of each phase at the grid output terminal, obtain the power change of each phase. If the deviation between the power change of each phase and the preset power reference value of the corresponding phase is less than or equal to the preset threshold, then it is determined that the three-phase meter wiring sequence is set correctly.

[0046] It should be noted that the grid output terminal mentioned in this application is relative to the grid side, where the grid side outputs power to the user to supply the load, hence the name grid output terminal. In practical applications, there may also be situations where photovoltaic / energy storage feeds into the grid through this grid output terminal. Specifically, when the three-phase inverter is in the first mode, it is in an off-grid state, and the power of the electrical load is entirely provided by the grid side. At this time, the three-phase meter can collect the first power of each phase at the grid output terminal. When the three-phase inverter is in a grid-connected and grid-feeding state, the power of the electrical load is shared by the grid side and the DC source (e.g., energy storage battery, photovoltaic panel). At this time, the three-phase meter should detect the decrease in the power of each phase at the grid output terminal, and the three-phase meter can collect the second power of each phase at the grid output terminal. Based on the first and second power of each phase at the grid output terminal, the power change of each phase at the grid output terminal before and after the three-phase inverter is connected to the grid can be calculated. In the embodiments of this application, the power change of any phase is defined as the difference between the second power and the first power of that phase. The power change in any phase at the grid output should be equal to the grid power supplied by the three-phase inverter in that phase. Considering actual power fluctuations, the deviation between the power change in any phase at the grid output and the grid power supplied by the three-phase inverter in that phase should be within a certain range.

[0047] This application features a specially designed second mode for the three-phase inverter, actively controlling it to operate in a short-term unbalanced power output state. This allows for the determination of the correct installation of the three-phase meters based on the power changes of each phase at the grid output before and after grid connection, as well as the difference in the feed-to-grid power settings for each phase after grid connection. For example, the feed-to-grid power of phase A of the three-phase inverter is set to Sa = 20%P. N The power of the B-phase feeder is Sb = 60%P N The power of the C-phase feeder is Sc = 100% P N This ensures that the grid-connected power of the three-phase inverter is in an unbalanced operating condition, while guaranteeing that the power of each phase is in the direction of grid feeding.

[0048] Assuming that when the three-phase inverter is in the first mode, the first power at the input terminals of the grid phases A, B, and C collected by the U, V, and W phase current sensors of the three-phase meter can be denoted as Pu1, Pv1, and Pw1, respectively; and when the three-phase inverter is in the second mode, the second power at the input terminals of the grid phases A, B, and C collected by the U, V, and W phase current sensors of the three-phase meter can be denoted as Pu2, Pv2, and Pw2, respectively.

[0049] Therefore, the power change detected by the U-phase current sensor can be expressed as Δu = Pu2 - Pu1, and the power change detected by the V-phase current sensor can be expressed as Δv = Pv2 - Pv1, and the power change detected by the W-phase current sensor can be expressed as Δw = Pw2 - Pw1.

[0050] When a three-phase meter is installed correctly, the U-phase current sensor should be connected to the A-phase line, the V-phase current sensor should be connected to the B-phase line, and the W-phase current sensor should be connected to the C-phase line.

[0051] Based on the grid power of the three-phase inverter on phases A, B, and C, if |△u-Sa|≤m, then the U-phase current sensor can be considered correctly connected to phase A. Similarly, if |△v-Sb|≤m, then the V-phase current sensor can be considered correctly connected to phase B. And if |△w-Sc|≤m, then the W-phase current sensor can be considered correctly connected to phase C. Here, m is greater than 0 and is a preset value that can be set according to actual conditions. Taking |△u-Sa|≤m as an example, it means that the deviation between the power change △u on phase A at the grid output and the preset power reference value Sa of phase A of the three-phase inverter is within a preset range.

[0052] It should be noted that, under normal circumstances, the three-phase grid-connected power of a three-phase inverter is in a balanced operating condition. The identification method provided in this application actively controls the grid-connected power of the three-phase inverter to be in a short-term unbalanced operating condition. Thus, based on the power change of each phase line at the grid output terminal before and after grid connection, combined with the preset unbalanced power of each phase of the three-phase inverter, it can determine whether the current sensor UVW phase of the three-phase meter is connected correctly.

[0053] As an optional implementation, the grid-connected power of the three-phase inverter can be temporarily unbalanced through software self-test settings. After correction, the three-phase inverter can be restored to balanced operation, thus avoiding adverse effects on the inverter (e.g., prolonged unbalanced operation may lead to uneven thermal stress in the phase switches, reducing the inverter's lifespan). It should be noted that during the three-phase meter wiring sequence correction process, significant switching of household loads should be avoided.

[0054] As an optional implementation, the method provided in this application further includes: determining whether the power change of each phase is less than zero; in response to the power change of any phase being less than zero, determining that the current sensor on the corresponding phase wiring of the three-phase meter is connected in the wrong direction; and in response to the power change of any phase being greater than zero, determining that the current sensor on the corresponding phase wiring of the three-phase meter is connected in the correct direction.

[0055] It should be noted that when a three-phase electricity meter is correctly installed, the UVW wiring sequence of the current sensor must take the current flowing into the grid as positive, and the correct sign for drawing power from the grid is negative, while the power generated by grid connection is positive. Therefore, the power change before and after grid connection should be greater than zero. For example, as shown in Figure 3, a schematic diagram of a three-phase electricity meter with the U-phase current sensor connected in reverse is presented. In this case, the U-phase current sensor in the three-phase electricity meter will measure Δu = Pu2 - Pu1 < 0. Therefore, it can be determined that the installation direction of the U-phase current sensor in the three-phase electricity meter is reversed, that is, the installation direction of the U-phase current sensor does not match the reference direction.

[0056] Furthermore, automatic correction can be performed when a wiring error in the three-phase meter is detected. As an optional implementation, in response to the determination that the current sensor is connected in reverse, the reading of the current sensor for the corresponding phase of the three-phase meter is negativeed.

[0057] In this way, only the negative value of the power reading of the corresponding phase needs to be set in the software and the state is saved. When the phase is commutated in the future, the original value is taken as negative. There is no need to readjust the installation direction of the current sensor in the three-phase meter, and no need for electricians or installers to rework. This greatly reduces the installation and maintenance costs of the inverter.

[0058] As an optional implementation, the method provided in this application also includes:

[0059] If the deviation between the power change of any phase and the preset power reference value of the corresponding phase exceeds the preset range, it is determined that the wiring sequence of the current sensor in the three-phase meter is incorrect.

[0060] Specifically, taking the U-phase current sensor test result of a three-phase electricity meter as an example, if |△u-Sa|>m, it can be considered that the U-phase current sensor of the three-phase electricity meter is not connected to the A-phase line, and the U-phase current sensor is connected incorrectly.

[0061] Furthermore, to automatically correct incorrect wiring sequences, a remarking step is set up: in response to the determination that the wiring sequence of the three-phase meter is incorrect, the phase to which the data collected from each connection port of the three-phase meter belongs is remarked; this remarking step includes the following sub-steps:

[0062] Obtain the first power change rate of the phase corresponding to the first terminal with an incorrect wiring sequence setting in the three-phase meter;

[0063] The first power change rate is matched with the preset power reference value for each phase. If the deviation between the first power change rate and the preset power reference value for the first phase is within a preset range, the data collected by the first connection port is marked as the data belonging to the first phase. It should be noted that the terms "first connection port," "first power change rate," and "first phase" are for descriptive convenience only. In specific embodiments, the first connection port can be any incorrectly connected connection port of the three-phase meter, and the first phase can be any one of the U-phase, V-phase, or W-phase.

[0064] For example, as shown in Figure 4, a schematic diagram of incorrect wiring sequence for the U-phase current sensor and the V-phase current sensor is presented. The U-phase current sensor is incorrectly connected to phase B; the first wiring port is either the U-phase port or the V-phase port; in actual operation, the U-phase current sensor actually detects the current in phase B, and the V-phase current sensor is incorrectly connected to phase A, in actual operation, the V-phase current sensor actually detects the current in phase A.

[0065] When an error is detected in the wiring sequence of the current sensor, the software can initiate a search algorithm to find combinations that satisfy |△j-Si|≤m (where i takes values ​​from a, b, c; j takes values ​​from u, v, w). This indicates that the j-phase current sensor (the current sensor corresponding to the phase with the first terminal) is connected to the i-phase line (the first phase). The software is then configured to treat the power reading of the j-phase current sensor as the power value of the i-phase line. For easy understanding, based on the three-phase meter connection shown in Figure 4, the following should apply: |△u-Sb|≤m, |△v-Sa|≤m, |△w-Sc|≤m. This means the U-phase current sensor is incorrectly connected to phase B, and the software is configured to treat its power reading as the power value of the B-phase line. Similarly, the V-phase current sensor is incorrectly connected to phase A, and the software is configured to treat its power reading as the power value of the A-phase line. Finally, the W-phase current sensor is correctly connected to phase C, and the software is configured to treat its power reading as the power value of the C-phase line.

[0066] In this way, only the settings need to be configured within the software, without having to readjust the wiring sequence of the current sensor in the three-phase meter, and without requiring electricians or installers to rework, greatly reducing the installation and maintenance costs of the inverter.

[0067] Figure 5 illustrates a schematic diagram of simultaneous errors in the direction and wiring sequence of current sensors. As an optional implementation, it can be first determined whether the direction of any phase current sensor is reversed. If so, the current sensor reading for the phase with the reversed direction is negative, which facilitates subsequent determination of the correctness of the three-phase meter wiring sequence and the wiring sequence correction. Then, the wiring sequence of the current sensors is determined to be correct according to the method provided in this application. If the wiring sequence is found to be incorrect, it can be corrected internally in the software according to the method provided in this application.

[0068] Table 1 lists the possible wiring configurations for a three-phase meter.

[0069] Table 1

[0070] As shown in Table 1, in actual situations, there are 7 cases where at least one phase current sensor has an incorrect direction but the wiring sequence is correct; 5 cases where at least two phases have incorrect wiring sequence but the direction is correct; and 35 cases where at least two phases have incorrect wiring sequence and the direction is incorrect. The three-phase meter wiring sequence identification method provided in this application can self-check and identify the above-mentioned errors in three-phase meter installation, and correct them after the self-check detects the errors.

[0071] As an optional implementation, when setting the unbalanced operating conditions of each phase in the second mode of the three-phase inverter, the preset power reference values ​​of each phase can be set with a large difference. As a result, when the three-phase meters detect the power changes of each phase at the grid output terminal before and after grid connection, the power changes of each phase are significantly different, making it easier to distinguish the correct wiring sequence of the three-phase meters and facilitating the identification method.

[0072] Specifically, to ensure the success rate of the three-phase meter self-test, this application conducts a semi-quantitative analysis of the power difference setting principle for each phase in the second mode of the three-phase inverter, as follows:

[0073] During the self-test, the power data read by the three-phase meters for the first time are Pu1, Pv1, and Pw1. Assuming that the fluctuation rate of the power read by the three-phase meters is α, and the error rate of the power reference value set by the three-phase inverter itself is β, then the actual power output of each phase of the three-phase inverter can be expressed as: Sa_rel=Sa*(1±β), Sb_rel=Sb*(1±β), Sc_rel=Sc*(1±β);

[0074] First, considering that the software needs to compare and distinguish the differences between power data Pu2, Pv2, Pw2 and Pu1, Pv1, Pw1, the following must be satisfied:

[0075] |(Si_rel-α*Pj1)-(Si_rel+α*Pj1)|≥0, for any i taking all values ​​of a, b, c, and any j taking all values ​​of u, v, w, we can simplify the formula to get: Si≥2α*Pj1 / (1-β).

[0076] The formula Si≥2α*Pj1 / (1-β) indicates that the power reference command for each phase must be greater than twice the current power fluctuation of that phase. Considering the maximum value of the power command error coefficient (1-β), twice the maximum value of Si (i=a, b, c) (for redundancy considerations) is set as Sa*.

[0077] Meanwhile, considering that the software needs to clearly distinguish the power difference between each phase in order to find the correct wiring sequence, without loss of generality, the following settings can be configured:

[0078] The reference value for phase A power is Sa = Sa*.

[0079] The reference value for phase B power is Sb=(1+γ)Sa*.

[0080] The reference value for phase C power is Sc=(1+2γ)Sa*.

[0081] Where γ is the power difference rate, which can be taken as approximately 20% to 40% depending on the actual situation. That is, the preset power reference values ​​for each phase of the three-phase inverter can be expressed as follows: Sa=2*max{2α*Pj1 / (1-β)|j=u,v,w}; Sb=2(1+γ)*max{2α*Pj1 / (1-β)|j=u,v,w}; Sc=2(1+2γ)*max{2α*Pj1 / (1-β)|j=u,v,w};

[0082] In the formula, Pj1 is the first power of the grid output terminal collected by the j-th phase of the three-phase meter when the three-phase inverter is in the first mode, j = u, v, w, where u, v, w can be rotated.

[0083] To further illustrate the three-phase electricity meter wiring sequence identification method provided in this application embodiment, the following description is based on a specific scenario. For ease of explanation, the fluctuation rate of the three-phase electricity meter reading power and the error rate of the three-phase inverter's own power reference value setting are ignored in the following scenarios, as follows:

[0084] Assuming the correct wiring sequence and direction of a three-phase (A / B / C) electricity meter connected to the power grid can be represented as U→A+ / V→B+ / W→C+, where U, V, and W represent current sensors, and A, B, and C represent power grid phase lines. Taking U→A+ as an example, it means the U-phase current sensor of the three-phase meter is connected to the A-phase line of the power grid, and the meter direction is correct, indicating positive meter reading. It is stipulated that the correct sign for drawing power from the grid is negative, and the power generated by grid connection is positive.

[0085] Let's assume one incorrect connection is U→C- / V→A- / W→B+ (as shown in Figure 5). Then the self-correction process is as follows:

[0086] Step S1: Using the three-phase meter, with the three-phase inverter in the first mode, collect the first power of each phase at the grid output terminal. Assuming that the actual power values ​​of the three phases A, B, and C of the grid are Pa1_rel = -1.2kW, Pb1_rel = -2.4kW, and Pc1_rel = -1.5kW respectively, then the first power of each phase detected by the three-phase meter can be expressed as follows: Pu1 = -Pc1_rel = 1.5kW; Pv1 = -Pa1_rel = 1.2kW; Pw1 = Pb1_rel = -2.4kW;

[0087] Step S2: Set the reference values ​​for the unbalanced three-phase grid-connected power of the three-phase inverter as Sa = 1.5kW, Sb = 2kW, and Sc = 4kW. Then, the actual power consumption of the three phases are as follows: Pa2_rel = Pa1_rel + Sa = 0.3kW; Pb2_rel = Pb1_rel + Sb = -0.4kW; Pc2_rel = Pc1_rel + Sb = 2.5kW.

[0088] Step S3: Read the power values ​​sampled by the three-phase meters for the second time, and record them as Pu2, Pv2, and Pw2 respectively. Since the actual current of phase A is measured in reverse by the phase V current sensor, the actual current of phase B is measured in forward by the phase W current sensor, and the actual current of phase C is measured in reverse by the phase U current sensor, then we have: Pu2 = -Pc2_rel = -2.5kW; Pv2 = -Pa2_rel = -0.3kW; Pw2 = Pb2_rel = -0.4kW;

[0089] Step S4: Calculate the power change. Calculate the values ​​of Pu2-Pu1, Pv2-Pv1, and Pw2-Pw1: △u = Pu2-Pu1 = -2.5kW - 1.5kW = -4kW < 0; △v = Pv2-Pv1 = -0.3kW - 1.2kW = -1.5kW < 0; △w = Pw2-Pw1 = -0.4kW - (-2.3kW) = 1.9kW > 0;

[0090] △w>0 indicates that the W-phase current sensor is in the correct direction. △u and △v are both less than 0, and the U-phase and V-phase current sensors are in opposite directions. The W-phase power reading value is kept in sign, and the U-phase and V-phase power reading values ​​are negative, i.e.: Pu*=-Pu; Pv*=-Pv; Pw*=Pw;

[0091] Where Pu* represents the reading of the U-phase current sensor after the current sensor direction correction, Pv* represents the reading of the V-phase current sensor after the current sensor direction correction, and Pw* represents the reading of the W-phase current sensor after the current sensor direction correction.

[0092] The first reading values ​​then become: Pu1* = -Pu1 = -1.5kW; Pv1* = -Pv1 = -1.2kW; Pw1* = Pw1 = -2.4kW;

[0093] The second reading values ​​are: Pu2* = -Pu2 = 2.5kW; Pv2* = -Pv2 = 0.3kW; Pw2* = Pw2 = -0.4kW;

[0094] Step S5: Traverse the values ​​of Pj2-Pj1 (j = u, v, w) and compare them with Sa, Sb, Sc. The results are shown in Table 2.

[0095] Table 2

[0096] According to Table 2, the results do not match Sa, Sb, and Sc, indicating that the U, V, and W three-phase current sensors are all connected in the wrong order.

[0097] Step S6: Traverse the values ​​of Pj2-Pj1 (j = u, v, w) and search for the corresponding Si (i = a, b, c) sequence until Pj2-Pj1 = Si is satisfied. At this time, we should have: Pu2*-Pu1* = Sc; Pv2*-Pv1* = Sa; Pw2*-Pw1* = Sb;

[0098] Based on the above relationships, it is explained that the U-phase current sensor is incorrectly connected to phase C of the power grid, the V-phase current sensor is incorrectly connected to phase A of the power grid, and the W-phase current sensor is incorrectly connected to phase B of the power grid. Based on step S6, the following corrections are made: Pa*=Pv*=-Pv; Pb*=Pw*=Pw; Pc*=Pu*=-Pu;

[0099] In the formula, Pa* represents the power of phase A of the power grid collected by the three-phase meter after calibration, and Pa*=Pv*=-Pv means that the negative value of the power measured by the phase V current sensor is taken as the power of phase A of the power grid; similarly, Pb* represents the power of phase B of the power grid collected by the three-phase meter after calibration, and Pb*=Pw*=Pw means that the power measured by the phase W current sensor is taken as the power of phase B of the power grid; Pc* represents the power of phase C of the power grid collected by the three-phase meter after calibration, and Pc*=Pu*=-Pu means that the negative value of the power measured by the phase U current sensor is taken as the power of phase C of the power grid. The calibration is now complete.

[0100] This application also provides a three-phase inverter 11. Figure 6 is a schematic diagram of an energy management system provided in an embodiment of this application. As shown in Figure 6, the three-phase inverter 11 is applied to an energy management system 100. The three-phase inverter 11 uses the three-phase meter 12 wiring sequence identification method provided in an embodiment of this application to automatically detect whether the wiring of the three-phase meter 12 is correct and corrects it when the wiring of the three-phase meter 12 is incorrect.

[0101] Energy Management System 100 includes:

[0102] The three-phase inverter 11, as shown in Figure 6, is a three-phase energy storage inverter. The DC side of the three-phase inverter 11 is used to connect to the DC source, and the AC side is used to connect to the grid side. The three-phase inverter 11 can realize grid-connected and off-grid operations.

[0103] Three-phase meter 12 is connected to the grid output terminal and is used to collect the three-phase power at the grid output terminal.

[0104] The three-phase inverter 11 includes a control module 13. Specifically, the control module 13 can be integrated with the three-phase inverter 11 or it can be installed separately. This application does not limit its structural configuration. It should be understood that in the energy management system 100, the control module 13 can also perform other control functions.

[0105] The three-phase inverter 11 has two operating modes: a first mode and a second mode.

[0106] When the three-phase inverter 11 is in the first mode, the three-phase inverter 11 is in an off-grid state;

[0107] When the three-phase inverter 11 is in the second mode, the three-phase inverter 11 is in grid-connected state, and each phase of the three-phase inverter 11 outputs power in the grid direction according to the preset power reference value. In the second mode, the preset power reference values ​​of each phase of the three-phase inverter 11 are different.

[0108] The control module 13 is used to collect the first power of each phase at the grid output terminal when the three-phase inverter 11 is in the first mode, and to collect the second power of each phase at the grid output terminal when the three-phase inverter 11 is in the second mode.

[0109] The control module 13 also obtains the power change of each phase based on the first power and second power of each phase at the power grid output terminal. If the power change of each phase is within the preset range of the deviation between the power change of each phase and the preset power reference value of the corresponding phase, the control module 13 determines that the three-phase meter 12 is set correctly.

[0110] Based on the above description, the three-phase inverter 11 provided in this application embodiment can actively control the three-phase inverter 11 to enter the second mode and actively control the three-phase inverter 11 to be in a short-term unbalanced power output state. Therefore, based on the power change of each phase at the grid output terminal before and after the three-phase inverter 11 is connected to the grid, as well as the different grid feed power of each phase after the three-phase inverter 11 is connected to the grid, it can be determined whether the installation of the three-phase meter 12 is correct.

[0111] As an optional implementation, the control module 13 is also used to determine whether the power change of each phase is greater than zero. In response to the power change of any phase being less than zero, it is determined that the current sensor on the corresponding phase wiring of the three-phase meter 12 is connected in the wrong direction.

[0112] For phases where the current sensor is connected in the wrong direction, the control module 13 will reverse the reading of the current sensor connected to the corresponding phase of the three-phase meter 12.

[0113] As an optional implementation, the control module 13 is also used to determine whether the deviation between the power change of each phase and the preset power reference value of the corresponding phase exceeds the preset range. In response to the deviation between the power change of any phase and the preset power reference value of the corresponding phase exceeding the preset range, it is determined that the wiring sequence of the current sensor in the three-phase meter 12 is incorrect.

[0114] As an optional implementation, the control module 13 is also used to re-mark the phase to which the data collected from each connection port of the three-phase meter 12 belongs in response to determining that the wiring sequence of the current sensor in the three-phase meter 12 is incorrect. The control module 13 is used to re-mark the data according to at least the following steps:

[0115] Obtain the first power change rate of the phase corresponding to the first terminal of the three-phase meter 12;

[0116] The first power change rate is matched with the preset power reference value of each phase. If the deviation between the first power change rate and the preset power reference value of the first phase is within a preset range, the data collected by the first wiring port is marked as the data of the first phase.

[0117] In summary, the three-phase meter 12 wire sequence identification method and three-phase inverter 11 provided in this application embodiment can utilize the grid-connected operation of the three-phase inverter 11 to actively control the three-phase inverter 11 to be in a short-term unbalanced power output state, thereby automatically and accurately correcting the wire sequence of the smart meter, saving time and effort, eliminating the need for electricians or installers to rework, and greatly reducing the installation and maintenance costs of the inverter.

[0118] This application also provides a three-phase electricity meter wiring sequence identification device, including:

[0119] The first power acquisition module is used to acquire the first power of each phase at the grid output terminal using a three-phase meter when the three-phase inverter is in the first mode. The three-phase inverter is in the off-grid state when it is in the first mode.

[0120] The second mode module is used to control the three-phase inverter to enter the second mode. When the three-phase inverter is in the second mode, it is in grid-connected state, and each phase of the three-phase inverter outputs power in the grid direction according to the preset power reference value of the corresponding phase. In the second mode, the preset power reference values ​​of each phase of the three-phase inverter are different.

[0121] The second power acquisition module is used to acquire the second power of each phase at the grid output terminal using a three-phase meter when the three-phase inverter is in the second mode.

[0122] The judgment module is used to obtain the power change of each phase based on the first power and second power of each phase at the power grid output terminal. If the deviation between the power change of each phase and the preset power reference value of the corresponding phase is within the preset range, it is judged that the three-phase meter wiring sequence is set correctly.

[0123] This application also provides a control module, including: a processor and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the three-phase meter line sequence identification method provided in the above embodiments.

[0124] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the three-phase meter line sequence identification method provided in the above embodiments.

[0125] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the three-phase meter line sequence identification method provided in the above embodiments.

[0126] It is understood that the term "exemplary" as used herein means "as an example, illustration, or description." Any embodiment described as "exemplary" is not necessarily preferred or superior to other embodiments and / or does not exclude features in combination with other embodiments. It should be understood that certain features of this application described in the context of a single embodiment for clarity may also be provided in combination in a single embodiment. Conversely, various features of this application described in the context of a single embodiment for clarity may also be provided individually or in any suitable combination or as part of any other described embodiment of this application.

[0127] The above-disclosed embodiments are merely preferred embodiments of this application, but are not intended to limit the scope of this application. Those skilled in the art will understand that any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and scope of this application and the appended claims are equivalent substitutions and still fall within the scope of the invention.

Claims

1. A method for identifying the line sequence of a three-phase power meter, the three-phase power meter being electrically connectable to a power grid for collecting three-phase power at an output of the power grid, the three-phase power meter further being communicatively connectable to a three-phase inverter, the three-phase inverter being operable in grid-connected and off-grid mode, the method comprising the steps of: The method comprises: ​ acquiring, by the three-phase power meter, first-phase power of the power grid output end when the three-phase inverter is in a first mode, the three-phase inverter being in an off-grid state when in the first mode; controlling the three-phase inverter to enter a second mode, the three-phase inverter being in a grid-connected state when in the second mode, and each phase of the three-phase inverter outputting in a grid-connected direction according to a preset power reference value of the corresponding phase, the preset power reference values of the three-phase inverter being different in the second mode; acquiring, by the three-phase power meter, second-phase power of the power grid output end when the three-phase inverter is in the second mode; acquiring a power change amount of each phase according to the first-phase power and the second-phase power of the power grid output end, and determining that the wiring sequence of the three-phase power meter is correct if the deviation between the power change amount of each phase and the preset power reference value of the corresponding phase is within a preset range.

2. The three-phase meter wire sequence identification method of claim 1, wherein, The method further comprises: The power change amount is the difference between the second power and the first power, and it is determined whether the power change amount of each phase is less than zero; in response to the power change amount of any phase being less than zero, it is determined that the current sensor direction of the corresponding phase of the three-phase power meter is connected reversely, and in response to the power change amount of any phase being greater than zero, it is determined that the current sensor direction of the corresponding phase of the three-phase power meter is correct.

3. The method of claim 2, wherein, The method further comprises: in response to determining that the current sensor direction is connected reversely, performing negative value processing on the current sensor reading of the corresponding phase of the three-phase power meter for the phase whose current sensor direction is connected reversely.

4. The method of claim 2 or 3, wherein The method further comprises: in response to the deviation between the power change amount of any phase and the preset power reference value of the corresponding phase being beyond the preset range, it is determined that the wiring sequence of the current sensor in the three-phase power meter is incorrect.

5. The method of claim 4, wherein, The method further comprises a re-labeling step of re-labeling the phase to which the data collected by each wiring port of the three-phase power meter belongs in response to determining that the wiring sequence of the current sensor in the three-phase power meter is incorrect. The re-labeling step comprises the following sub-steps: acquiring a first power change rate of the corresponding phase of a first wiring port whose wiring sequence is incorrect in the three-phase power meter; matching the first power change rate with the preset power reference value of each phase, and if the deviation between the first power change rate and the preset power reference value of the first phase is within the preset range, labeling the data collected by the first wiring port as data belonging to the first phase.

6. The three-phase power meter wiring sequence identification method according to any one of claims 1-5, wherein the preset power reference values of the three-phase inverter are different, and the preset power reference values of the three-phase inverter are represented as follows: Sa=2*max{2α*Pj1 / (1-β)|j=u,v,w}; Sb=2(1+γ)*max{2α*Pj1 / (1-β)|j=u,v,w}. ​ ​ ​ Sc=2(1+2γ)*max{2α*Pj1 / (1-β)|j=u,v,w}; In the formula, Sa, Sb and Sc respectively represent preset power reference values of the three-phase inverter A, B and C phases, α represents a fluctuation rate of power read by the three-phase power meter, β represents an error rate of the power reference value set of the three-phase inverter itself, γ is a power difference rate, Pj1 is a first power of the grid output end collected by the j phase of the three-phase power meter when the three-phase inverter is in a first mode, j=u, v, w, and u, v and w respectively represent U, V and W phases of the three-phase power meter. 7.A three-phase inverter applied to an energy management system, the energy management system comprising a three-phase power meter and a three-phase inverter; a direct current side of the three-phase inverter being used to be connected with a direct current source, and an alternating current side being used to be connected with a grid side, the three-phase inverter being capable of realizing parallel and off-grid operations; the three-phase power meter being electrically connected with the grid, and the three-phase power meter being used to collect three-phase powers of the grid output end; characterized in that the three-phase inverter further comprising a control module, the control module being used to: control the three-phase inverter to be in a first mode in an off-grid state or in a second mode in a parallel state, and control each phase of the three-phase inverter to output in a grid feeding direction according to a preset power reference value in the second mode, and the preset power reference values of the phases of the three-phase inverter are different in the second mode; the control module is further used to collect each phase first power of the grid output end by using the three-phase power meter when the three-phase inverter is in the first mode, and collect each phase second power of the grid output end when the three-phase inverter is in the second mode; the control module is further used to obtain a power variation of each phase according to the each phase first power and the each phase second power of the grid output end, and if deviations between the power variation of each phase and the preset power reference value of the corresponding phase are in a preset range, the control module judges that the three-phase power meter is set correctly. 8.The three-phase inverter of claim 7, wherein the control module is further used to judge whether the power variation of each phase is greater than zero, and in response to the power variation of any phase being less than zero, it is judged that a current sensor direction of a corresponding phase connection of the three-phase power meter is connected reversely; for the phase with the reversely connected current sensor direction, the control module performs a negation processing on a current sensor reading of the corresponding phase connection of the three-phase power meter. 9.The three-phase inverter of claim 8, wherein the control module is further used to judge whether the deviation between the power variation of each phase and the preset power reference value of the corresponding phase exceeds the preset range, and in response to the deviation between the power variation of any phase and the preset power reference value of the corresponding phase exceeding the preset range, it is judged that a wiring sequence of the current sensor in the three-phase power meter is set incorrectly. 10.The three-phase inverter of claim 8 or 9, wherein The control module is further configured to, in response to determining that the wiring sequence of the current sensor in the three-phase power meter is set incorrectly, re-label the data collected by each wiring port of the three-phase power meter as belonging to a phase; The control module is configured to re-label according to at least the following steps: obtaining a first power change rate of a phase corresponding to a first wiring port of the three-phase power meter; matching the first power change rate with the preset power reference value of each phase, and if the deviation between the first power change rate and the preset power reference value of the first phase is within the preset range, then labeling the data collected by the first wiring port as belonging to the first phase.

11. A three-phase meter wire sequence identification device, characterized by, Comprise: a first power collection module configured to collect first power of each phase of a power grid output end using the three-phase power meter, wherein the three-phase inverter is in a first mode, the three-phase inverter is in an off-grid state when in the first mode; a second mode module configured to control the three-phase inverter to enter a second mode, wherein the three-phase inverter is in the second mode, the three-phase inverter is in a grid-connected state, and each phase of the three-phase inverter outputs in a grid-connected direction according to a preset power reference value of the corresponding phase, and the preset power reference values of each phase of the three-phase inverter are different in the second mode; a second power collection module configured to collect second power of each phase of the power grid output end using the three-phase power meter, wherein the three-phase inverter is in the second mode; a judgment module configured to obtain a power change amount of each phase according to the first power of each phase of the power grid output end and the second power of each phase, and determine that the wiring sequence of the three-phase power meter is set correctly if the deviation between the power change amount of each phase and the preset power reference value of the corresponding phase is within a preset range.

12. A control module, characterized by Comprise: a processor, and a memory in communication with the processor; the memory stores computer execution instructions; the processor executes the computer execution instructions stored in the memory to implement the three-phase power meter wiring sequence identification method according to any one of claims 1-6.

13. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer execution instructions, and the computer execution instructions are executed by the processor to implement the three-phase power meter wiring sequence identification method according to any one of claims 1-6.

14. A computer program product, characterised in that, A computer program is provided, and the computer program is executed by the processor to implement the three-phase power meter wiring sequence identification method according to any one of claims 1-6.

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