Energy storage system and CT correction calculation method thereof

Abstract

The invention discloses an energy storage system and a CT correction calculation method thereof, and the method comprises the steps: controlling the jth phase of an inverter to sequentially output two kinds of power, obtaining the voltage of each phase of a power grid and a corresponding CT current sampling value of each phase, and calculating the power of each phase of the power grid according to the voltage of each phase of the power grid and the corresponding CT current sampling value of each phase; calculating a proportionality coefficient between the jth-phase power of the inverter and each-phase power of the power grid according to the two powers and the corresponding calculated power of each phase of the power grid; according to the number of phases of the energy storage system, directly or repeatedly controlling other phases of the inverter to output two kinds of power so as to obtain a proportionality coefficient between the power of each phase of the inverter and the power of each phase of a power grid; and identifying the CT access condition and correcting the power of each phase of the power grid according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid. According to the method, extra auxiliary equipment and circuits are not needed, the CT access condition can be identified, and the correct power grid power can be obtained through direct calculation.

Description

Technical Field

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

[0002] The energy storage industry is developing rapidly, and the number of household energy storage products is increasing day by day. Many household energy storage inverter systems are equipped with electricity meters for data collection. However, during the installation process, if the CT of the electricity meter is connected wrongly, it will cause the energy storage inverter system to collect incorrect data, resulting in incorrect power scheduling.

[0003] There is a prior art method for detecting the connection of the current transformer of the electricity meter in the energy storage system. By observing the change of the actual charge and discharge power through the charge and discharge actions, it is determined whether the CT wiring is normal. Although this method can identify the CT wiring error, it is necessary to manually adjust the CT wiring correctly to obtain accurate data.

[0004] There is also a prior art device and method for detecting the connection of the current transformer of the electricity meter in the energy storage system. This method enables the energy storage system to enter the off-grid and loaded mode, uses a simulated load, and compares the power of the simulated load with the power collected by the electricity meter to determine whether the CT is connected wrongly. This method requires the energy storage system to enter the off-grid mode, and additional auxiliary equipment and circuits are required to complete this detection, which is relatively complex and difficult to implement for general users.

[0005] The disclosure of the above background art content is only used to assist in understanding the concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. Without clear evidence indicating that the above content was publicly available on the filing date of this patent application, the above background art should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes an energy storage system and its CT correction calculation method, which can identify the CT access situation and directly calculate the correct grid power without additional auxiliary equipment and circuits.

[0007] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention discloses a CT correction calculation method for an energy storage system, including the following steps: S1: Control the j phase of the inverter to output a first power, obtain the grid voltage of each phase and the corresponding CT current sampling value of each phase, and calculate the grid power of each phase according to the grid voltage of each phase and the corresponding CT current sampling value of each phase; S2: Control the jOutput the second power for each phase, obtain the grid voltage of each phase and the corresponding current sampling value of the CT for each phase, and calculate the grid power of each phase based on the grid voltage of each phase and the corresponding current sampling value of the CT for each phase; S3: Calculate the proportionality coefficients between the power of the j-th phase of the inverter and the grid power of each phase based on the first power, the second power, the grid power of each phase calculated in step S1, and the grid power of each phase calculated in step S2; S4: If the energy storage system is a single-phase energy storage system, directly obtain the proportionality coefficients between the power of each phase of the inverter and the grid power of each phase; if the energy storage system is a multi-phase energy storage system, replace the output phase of the inverter and repeat steps S1 to S3 to calculate the proportionality coefficients between the power of each phase of the inverter and the grid power of each phase; S5: Identify the connection situation of the CT for each phase and correct the grid power of each phase according to the proportionality coefficients between the power of each phase of the inverter and the grid power of each phase.

[0008] Preferably, in steps S1 and S2, based on the grid voltage of each phase and the corresponding current sampling value of the CT for each phase, calculate the grid power of each phase in combination with the following formula:

[0009] In the formula, represents the grid power of the n -th phase, T is the grid cycle, represents t the grid voltage of the n -th phase obtained at time represents t the current sampling value of the CT of the n -th phase obtained at time

[0010] Preferably, step S3 specifically includes: based on the first power, the second power, the grid power of each phase calculated in step S1, and the grid power of each phase calculated in step S2, calculate the proportionality coefficients between the power of the j -th phase of the inverter and the grid power of each phase in combination with the following relational expression:

[0011] In the formula, P grid_n represents the grid power of the n -th phase, P inv_j represents the first power or the second power output by the j -th phase of the inverter, k jn represents the jThe proportionality coefficient between the phase power and the n phase grid power, b jn indicating the j phase power of the inverter and the m static deviation between the phase grid power.

[0012] Preferably, step S5 specifically includes: judging whether there is any missing connection and / or duplicate connection of each phase CT according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the grid. If not, correcting the power of each phase of the grid according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the grid.

[0013] Preferably, when judging whether there is any missing connection and / or duplicate connection of each phase CT according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the grid, if it is judged that there is a missing connection and / or duplicate connection, after adjusting the corresponding missing connection and / or duplicate connection situation, return to step S1.

[0014] Preferably, judging whether there is any missing connection and / or duplicate connection of each phase CT according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the grid specifically includes: If there are more than two absolute values of the proportionality coefficients between the powers of each phase of the inverter and the power of a certain phase of the grid within the range of [1 - a, 1 + a], it indicates that there are multiple phase CTs connected in duplicate to this phase of the grid, where a is the first preset threshold; if the absolute value of the proportionality coefficient between the power of a certain phase of the inverter and the powers of each phase of the grid is less than the second preset threshold, it indicates that there is a missing connection of this phase CT.

[0015] Preferably, the value range of the first preset threshold is 0 - 0.2, and the value range of the second preset threshold is 0 - 0.4.

[0016] Preferably, in step S5, the power of each phase of the grid is corrected according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the grid, in combination with the following formula:

[0017] In the formula, represents the corrected n phase grid power, T is the grid period, u n ( t ) represents t the n phase grid voltage obtained at the moment of N indicating the number of phases of the energy storage system; i jn indicating at thej When the t phase output power, n the current sampling value of the k jn phase CT at the moment, j where n represents the proportionality coefficient between the g jn phase power of the inverter and the k jn phase grid power; g jn = k jn ; k jn = 0, g jn = 1.

[0018] In a second aspect, the present invention discloses an energy storage system, including an inverter, a CT, and a power grid. Each phase output terminal of the inverter is respectively connected to three phases of the power grid. Each phase on the sampling side of the CT is respectively connected to three phases of the power grid. The feedback side of the CT is connected to the inverter. The energy storage system is configured to correct each phase of the grid power according to the CT correction calculation method of the energy storage system described in the first aspect.

[0019] In a third aspect, the present invention discloses a computer-readable storage medium, in which a computer program is stored. The computer program is configured to be run by a processor to execute the CT correction calculation method of the energy storage system described in the first aspect.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The energy storage system and its CT correction calculation method disclosed by the present invention control each phase of the inverter to output power multiple times in sequence, calculate the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the grid by detecting the change of the grid-side power, and based on this, can identify the CT connection situation and correct the power of each phase of the grid, so as to directly obtain the correct grid power without manually adjusting the CT wiring in case of wrong connection or reverse connection; in this solution, intelligent detection of the CT wiring situation and calibration can be achieved without the need to rely on additional auxiliary equipment and circuits, which is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flowchart of the CT correction calculation method of the energy storage system disclosed in Embodiment 1 of the present invention; Figure 2 is a framework diagram of the energy storage system in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following provides a detailed description of the embodiments of the present invention. It should be emphasized that the following description is merely exemplary and not intended to limit the scope of the present invention and its applications.

[0023] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on that other element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to that other element. Additionally, the connection can be for a fixing function or for a circuit / signal communication function.

[0024] It should be understood that the orientation or positional relationships indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0025] Furthermore, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0026] The following first provides corresponding explanatory descriptions of the terms involved in this case.

[0027] CT: Current transformer, a device for detecting the system current, and the collected data is transmitted to the system for power calculation.

[0028] As Figure 1 shown, it is a CT correction calculation method for an energy storage system disclosed in Embodiment 1 of the present invention, including the following steps: S1: Control the j th phase of the inverter to output a first power, obtain the grid voltages of each phase and the corresponding CT current sampling values of each phase, and calculate the grid power of each phase according to the grid voltages of each phase and the corresponding CT current sampling values of each phase; S2: Control the j th phase of the inverter to output a second power, obtain the grid voltages of each phase and the corresponding CT current sampling values of each phase, and calculate the grid power of each phase according to the grid voltages of each phase and the corresponding CT current sampling values of each phase; In the above steps S1 and S2, according to the grid voltages of each phase and the corresponding current sampling values of each phase CT, the grid power of each phase is calculated specifically according to the following formula (1): (1) Wherein, represents the grid power of the n th phase; T is the grid cycle; represents t the grid voltage of the n th phase obtained at the moment, which is directly sampled by the inverter; represents t the current sampling value of the n th phase CT obtained at the moment.

[0029] S3: According to the first power, the second power, the grid power of each phase calculated in step S1, and the grid power of each phase calculated in step S2, calculate the proportionality coefficients between the power of the j th phase of the inverter and the grid power of each phase respectively; Specifically, according to the first power, the second power, the grid power of each phase calculated in step S1, and the grid power of each phase calculated in step S2, combine the following relational formula (2) to calculate the proportionality coefficients between the power of the j th phase of the inverter and the grid power of each phase respectively: (2) Wherein, P grid_n represents the grid power of the n th phase, P inv_j represents the first power or the second power output by the j th phase of the inverter, k jn represents the proportionality coefficient between the power of the j th phase of the inverter and the grid power of the n th phase, b jn represents the static deviation between the power of the j th phase of the inverter and the grid power of the n th phase.

[0030] S4: If the energy storage system is a single-phase energy storage system, directly obtain the proportionality coefficients between the power of each phase of the inverter and the grid power of each phase; if the energy storage system is a multi-phase energy storage system, replace the output phase of the inverter and repeat steps S1 to S3 to calculate the proportionality coefficients between the power of each phase of the inverter and the grid power of each phase.

[0031] This preferred embodiment is applicable to single-phase, two-wire (single-phase split-phase), and three-phase energy storage systems. Single-phase and two-wire energy storage systems are usually connected to a single-phase power grid, and three-phase energy storage systems are usually connected to a three-phase power grid. Among them, when the energy storage system is a single-phase energy storage system, according to the aforementioned steps S1 to S3, the proportionality coefficient between the single-phase power of the inverter and the single-phase power grid power has been calculated. When the energy storage system is a two-wire energy storage system, according to the aforementioned steps S1 to S3, the proportionality relationship between the power of one phase of the inverter and the power of the two-wire power grid has been calculated. Therefore, it is necessary to change the output phase of the inverter and re-execute steps S1 to S3 once to calculate the proportionality relationship between the power of the other phase of the inverter and the power of the two-wire power grid. When the energy storage system is a three-phase energy storage system, according to the aforementioned steps S1 to S3, the proportionality relationship between the power of one phase of the inverter and the power of each phase of the power grid has been calculated. Therefore, it is necessary to change the output phase of the inverter and re-execute steps S1 to S3 twice to calculate the proportionality relationship between the power of the other two phases of the inverter and the power of each phase of the power grid in turn.

[0032] S5: Identify the CT connection situation of each phase and correct the power of each phase of the power grid according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid.

[0033] Step S5 specifically includes: judging whether there is a missing connection and / or duplicate connection of the CT of each phase according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid. If so, after adjusting the corresponding missing connection and / or duplicate connection situation, return to step S1; if not, correct the power of each phase of the power grid according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid.

[0034] Among them, judging whether there is a missing connection and / or duplicate connection of the CT of each phase according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid specifically includes: if there are more than two absolute values of the proportionality coefficients between the powers of each phase of the inverter and the power of a certain phase of the power grid within the range of [1-a, 1+a], it indicates that there is a situation where multiple phases of CT are repeatedly connected to this phase of the power grid, where a is the first preset threshold; if the absolute value of the proportionality coefficient between the power of a certain phase of the inverter and the powers of each phase of the power grid is less than the second preset threshold, it indicates that there is a missing connection situation in this phase of the power grid; specifically, the value range of the first preset threshold is 0-0.2, and the value range of the second preset threshold is 0-0.4.

[0035] In addition to determining whether there is a missed connection and / or duplicate connection in each phase CT, it is also possible to determine whether the polarity of each phase CT is reversed according to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid. If the proportionality coefficient between the power of a certain phase of the inverter and the power of a certain phase of the power grid is less than 0, it indicates that the CT of this phase is reversely connected; otherwise, it indicates that the CT of this phase is not reversely connected.

[0036] According to the proportionality coefficient between the power of each phase of the inverter and the power of each phase of the power grid, the power of each phase of the power grid is corrected by combining the following formula (3): (3) In the formula, represents the corrected power of the n th phase of the power grid, T is the power grid period, u n ( t ) represents t the grid voltage of the n th phase obtained at time N represents the number of phases of the energy storage system; i jn represents that when the output power of the jth phase of the inverter is t the current sampling value of the n th phase CT obtained at time k jn represents the j th phase of the inverter n the proportionality coefficient between the phase power and the power of the g jn represents the adjustment parameter, where k jn when ≠ 0, g jn = k jn ; k jn when = 0, g jn = 1.

[0037] Embodiment 2 of the present invention discloses an energy storage system, including an inverter, a CT, and a power grid. The output terminals of each phase of the inverter are respectively connected to the three phases of the power grid, and each phase of the sampling side of the CT is respectively connected to the three phases of the power grid. The feedback side of the CT is connected to the inverter. The energy storage system is used to correct the power of each phase of the power grid according to the CT correction calculation method of the energy storage system in Embodiment 1. Among them, the energy storage system can be a single-phase energy storage system, a two-wire energy storage system, or a three-phase energy storage system.

[0038] The following further elaborates on the CT correction calculation method for the energy storage system in Embodiment 1 of the present invention and the energy storage system disclosed in Embodiment 2 in conjunction with specific embodiments.

[0039] Taking a three-phase energy storage system as an example, as Figure 2 shown, this three-phase energy storage system includes an inverter 10, a CT 20, and a power grid 30. Among them, the three-phase output terminals L1, L2, and L3 of the inverter 10 are respectively connected to the corresponding three-phase lines L1, L2, and L3 of the power grid 30. The CT 20 includes three independent sub-phase CTs (201, 202, 203). The sampling side of each sub-phase CT is connected to the corresponding phase line L1, L2, L3 of the power grid 30, and the feedback side is respectively connected to the inverter 10 for real-time monitoring of the current values I1, I2, and I3 of each phase line of the power grid 30.

[0040] Under normal circumstances, the wiring of the CT 20 needs to match the inverter output phase sequence and the power grid phase sequence simultaneously to ensure the correctness of the current measurement, protection, and control systems. First, each sub-phase CT of the CT 20 is matched with the inverter output phase sequence one by one through communication, that is, the sub-phase CT 201 corresponds to the L1 phase of the inverter, the sub-phase CT 202 corresponds to the L2 phase of the inverter, and the sub-phase CT 203 corresponds to the L3 phase of the inverter. The power grid wiring sequence of the CT 20 needs to correspond to the output sequence of the inverter 10 one by one, that is, the sub-phase CT 201 detects the L1-phase power grid current I1; the sub-phase CT 202 detects the L2-phase power grid current I2; the sub-phase CT 203 detects the L3-phase power grid current I3, thereby ensuring the accuracy and stability of the system operation. However, in actual situations, there may be the following abnormal situations in the power grid wiring of each sub-phase CT: missing connection, duplicate connection, wrong connection (phase error), reverse connection (polarity / direction error). For a single-phase energy storage system, there is no problem of duplicate connection and wrong connection, and only missing connection and reverse connection may occur; for a two-phase energy storage system or a three-phase energy storage system, all of the above situations may occur.

[0041] In response to the above abnormal situations, the following provides a method that can intelligently detect the wiring situation of the CT 20 and perform calibration to calculate the true grid power of each phase of the three-phase energy storage system even when the CT is wrongly connected or reversely connected. The present invention first excludes the situations of missing connection and duplicate connection through the following technical solutions. If there are situations of missing connection and duplicate connection, there will definitely be at least one phase CT not connected to the power grid, and in this case, the true grid power of this phase cannot be obtained. Therefore, manual adjustment is required; in this solution, after excluding the situations of missing connection and duplicate connection, manual adjustment for wrong connection and reverse connection is not required, and the correct grid power can be directly calculated to achieve the correction calculation of the CT.

[0042] The following takes the most complex three-phase energy storage system as an example for detailed description.

[0043] First, control the inverter 10 to output power in each phase in turn, and calculate the real-time grid power of each phase according to the above formula (1): (1) In the formula, represents the grid power of the n phase, n which can be 1, 2, or 3, T is the grid cycle, represents t the grid voltage of the n phase obtained at time represents t the current sampling value of the CT of the n phase obtained at time

[0044] The real-time grid power of each phase calculated according to the grid voltage of each phase and the current sampling value of the CT of each phase in the above formula (1) is not the real power when there is an abnormal connection of the CT. Based on this, this solution infers the connection situation of the energy storage system.

[0045] Taking the L1 phase of the inverter as an example, taking the output powers of 500W and 1000W respectively, and the output powers of the other two phases are 0. When the L1 phase of the inverter outputs 500W of power, collect the grid voltage of each phase and the current sampling value of the CT of each phase, and combine with formula (1) to obtain the grid power data of the three phases of the system at this time P grid_1 , P grid_2 , P grid_3 , and the corresponding data points obtained are (500, P grid_1 ), (500, P grid_2 ), (500, P grid_3 ); when the L1 phase of the inverter outputs 1000W of power, collect the grid voltage of each phase and the current sampling value of the CT of each phase, and combine with formula (4) to obtain the grid power data of the three phases of the system at this time P grid_1 , P grid_2 , P grid_3 , and the corresponding data points obtained are (1000, P grid_1 ), (1000, P grid_2 ), (1000, P grid_3 ).

[0046] Substitute the above six points into the following relational expression (4): (4) In the formula, n takes values of 1, 2, 3, P grid_n represents the n power of the n - th phase power grid, P inv_1 represents the power output by the first phase of the inverter (corresponding to 500 or 1000), k 1n represents the proportionality coefficient between the power of the first phase of the inverter and the n power of the n - th phase power grid, b 1n represents the static deviation between the power of the first phase of the inverter and the n power of the n - th phase power grid.

[0047] According to the above six points, it can be calculated that k 11 , b 11 , k 12 , b 12 , k 13 , b 13 .

[0048] Then, let the L2 phase and L3 phase of the inverter output two kinds of powers respectively (except for the output power phase, the output powers of other phases are 0), and obtain the corresponding grid power data of the three - phase system, and all the key parameters in Table 1 can be obtained: Table 1 Key parameters between the power of each phase of the inverter and the power of each phase of the grid k jn and b jn

[0049] k jn represents the proportionality coefficient, b jn represents the static deviation, where, j represents the j phase of the inverter, n represents the n phase of the power grid.

[0050] Thus, the relationship between the power of each phase of the inverter and the power of each phase of the grid is obtained. Among them, the magnitude and sign of the proportionality coefficient k jn reflect the phase sequence and orientation of each phase CT connected to the power grid, and the static deviation b jnThe existence indicates the load power existing in the current system, which can prevent this detection method from being interfered by the load.

[0051] In the case where multiple-phase CTs are connected to the same phase of the power grid or a certain phase CT is missed, manual adjustment is required. Therefore, the following is to screen the value of the proportional coefficient k: Under ideal conditions, when the inverter L1 outputs power and the inverters L2 and L3 do not output power, if the CT of phase L1 is connected to the power grid of phase L2, the calculated power of the power grid of phase L1 is always 0, that is k 11 = 0. If there are two or more | k jn | close to 1, that is, the values within the range of [1 - a, 1 + a], it indicates that at least two-phase CTs are connected to the power grid phase sequence corresponding to the inverter phase sequence, where a is the first preset threshold, and its value range is 0 - 0.2; for example, when the CTs of phases L2 and L3 of the system are both connected to the power grid of phase L1, the power can be collected from both the power grids of phases L2 and L3, that is k 12 、 k 13 are both close to 1. If the inverters output power in turn for each phase, but the three | k jn | in a column of the above table are all less than the second preset threshold, and the value range of the second preset threshold is 0 - 0.4, for example, it is 0.3, then it indicates that the CT of this phase is missed, that is, it is not connected to any phase of the power grid.

[0052] The above first preset threshold and second preset threshold are the reserved deviations for calculation. In actual situations, taking phase L1 as an example, if the CT of phase L1 is correctly connected to the power grid of phase L1, then k 11 is close to 1, if it is connected reversely, then k 11 is close to -1; if the CT of phase L2 is connected to the power grid of phase L1 but the orientation is correct, then k 11 is close to 0, k 12 is close to 1, and when the orientation is wrong, then k 11 is close to 0, k 12 is close to -1; if the CT of phase L1 is missed, then k 11 、 k 21 、 k 31 are close to 0.

[0053] Under ideal conditions, taking the proportional coefficients of 1 and 0 as an example, when the jWhen the inverter outputs power for one phase (while the other phases do not output power), every j phase and the n phase of the power grid has the following proportional relationship: If n = j , and k jn = 1, it means that the phase sequence and polarity of the CT of the n phase are correctly connected to the j phase of the inverter corresponding to the j phase of the power grid.

[0054] If n = j , and k jn = -1, it means that the phase sequence of the CT of the n phase is correctly connected to the j phase of the inverter corresponding to the j phase of the power grid, but the polarity is reversed.

[0055] If n ≠ j , and k jn = 1, it means that the CT of the n phase is wrongly connected to the j phase of the inverter corresponding to the j phase of the power grid, but the polarity is correct.

[0056] If n ≠ j , and k jn = -1, it means that the CT of the n phase is wrongly connected to the j phase of the inverter corresponding to the j phase of the power grid, and the polarity is opposite.

[0057] If the inverter outputs power in rotation for three phases, and k 1n = k 2n = k 3n = 0, it means that the CT of the n phase is not connected.

[0058] When each phase CT is correctly connected to each phase of the power grid, the proportionality coefficient should be as shown in Table 2 below: Table 2 Proportionality Coefficient between the Power of Each Phase of the Inverter and the Power of Each Phase of the Power Grid k jn

[0059] After excluding the above-mentioned cases of missed connection or duplicate connection, it indicates that at this time, the CTs of the energy storage system may only have the situation of incorrect connection or reverse connection among each other, but there is no situation of missed connection or duplicate connection. At this time, the calculation formula (3) can be used to correct and obtain the correct grid power of each phase of the energy storage system: (3) For a three-phase system, after expanding formula (3), it becomes formula (5) as follows (5) In the above formula, represents the grid power of the n th phase after correction, T is the grid period, u n ( t ) represents t the grid voltage of the n th phase obtained at the moment of N indicating the number of phases of the energy storage system; i 1n represents when the output power of the first phase of the inverter is t the current sampling value of the CT of the n th phase obtained at the moment of ；i 2n represents when the output power of the second phase of the inverter is t the current sampling value of the CT of the n th phase obtained at the moment of i 3n represents when the output power of the third phase of the inverter is t the current sampling value of the CT of the n th phase obtained at the moment of k 1n represents the proportionality coefficient between the power of the 1 th phase of the inverter and the grid power of the n th phase; k 2n represents the proportionality coefficient between the power of the 2 th phase of the inverter and the grid power of the n th phase; k 3n represents the proportionality coefficient between the power of the 3 th phase of the inverter and the grid power of the n th phase ；g 1n 、g 2n 、g 3n represents the adjustment parameter, where, k jn when ≠ 0, g jn =k jn ; k jn When = 0, g jn = 1 ，j = 1, 2, 3.

[0060] For example, if the CT of phase L1 is wrongly connected to the power grid of phase L2, then the power of the power grid of phase L2 is equal to the average value obtained by integrating the voltage of phase L2 and the current of phase L1. That is, in this solution, the correlation between the output power of each phase of the inverter and the power of each phase of the power grid is obtained through multiple calculations, so as to calculate the correct power of the power grid.

[0061] When the energy storage system is a two-wire energy storage system, the calculation formula for correcting the power of the power grid of each phase of the energy storage system is formula (6): (6) When the energy storage system is a single-phase energy storage system, the calculation formula for correcting the power of the power grid of each phase of the energy storage system is formula (7): (7) In the embodiment of the present invention, the actual CT access situation of the energy storage system is identified through logical calculation, and through a specific calculation method, regardless of whether the CT is wrongly connected or reversed, the correct power of the power grid can be corrected; moreover, no additional auxiliary equipment and circuits are required during the process, which is easy to implement and applicable to three-phase, two-wire, and single-phase energy storage systems.

[0062] Embodiment 3 of the present invention discloses a computer-readable storage medium, in which a computer program is stored. Among them, the computer program is set to be run by a processor to execute the steps of the CT correction calculation method of the energy storage system in Embodiment 1 above.

[0063] Optionally, the above computer-readable storage medium may include, but is not limited to: various media such as USB flash drives, read-only memories (ROM for short), random access memories (RAM for short), mobile hard disks, magnetic disks, or optical discs that can store computer programs.

[0064] The background part of the present invention may include background information about the problems or environment of the present invention, rather than the description of the prior art by others. Therefore, the content included in the background art section is not an admission by the applicant of the prior art.

[0065] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, they can make several substitutions or modifications to these described embodiments, and these substitution or modification methods should all be regarded as belonging to the protection scope of the present invention. In the description of this specification, the descriptions with reference to terms such as "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the scope defined by the appended claims.

Claims

1. A CT correction calculation method for an energy storage system, characterized in that: The following steps are involved: S1: Control inverter j Output the first power of each phase, obtain the grid voltage of each phase and the corresponding CT current sampling value of each phase, and calculate the grid power of each phase according to the grid voltage of each phase and the corresponding CT current sampling value of each phase; S2: Control the inverter j Output the second power of each phase, obtain the grid voltage of each phase and the corresponding CT current sampling value of each phase, and calculate the grid power of each phase according to the grid voltage of each phase and the corresponding CT current sampling value of each phase; S3: Calculate the inverter first power according to the first power, the second power, the power of each phase of the power grid calculated in step S1, and the power of each phase of the power grid calculated in step S2. j The proportionality coefficient between the phase power and the power of each phase grid; S4: If the energy storage system is a single-phase energy storage system, directly obtain the proportional coefficient between each phase power of the inverter and each phase power of the grid; if the energy storage system is a multi-phase energy storage system, replace the output phase of the inverter and repeat steps S1 to S3 to calculate the proportional coefficient between each phase power of the inverter and each phase power of the grid; S5: According to the proportional coefficient between each phase power of the inverter and each phase power of the grid, the connection status of each phase CT is identified and the grid power of each phase is corrected.

2. The CT correction calculation method for the energy storage system according to claim 1, characterized in that: In step S1 and step S2, the power of each phase of the grid is calculated based on the voltage of each phase of the grid and the corresponding CT current sampling value of each phase, combined with the following formula: ； In the formula, Indicates n Phase grid power, T is the power grid cycle, express t The first n Phase grid voltage, express t The first n Current sampling value of phase CT.

3. The CT correction calculation method for the energy storage system according to claim 1, characterized in that: Step S3 specifically includes: calculating the inverter power of the first phase according to the first power, the second power, the power of each phase of the grid calculated in step S1, and the power of each phase of the grid calculated in step S2, in combination with the following relationship: j The proportionality coefficient between the phase power and the grid power of each phase: ； In the formula, P grid_n Indicates n Phase grid power, P inv_j Indicates the inverter j The first power or the second power of the phase output, k jn Indicates the inverter j Phase power and n The proportionality coefficient between the phase grid powers, b jn Indicates the inverter j Phase power and n Static deviation between phase grid powers.

4. The CT correction calculation method for the energy storage system according to claim 1, characterized in that: Step S5 specifically includes: judging whether each phase CT has missed connection and / or repeated connection according to the proportional coefficient between each phase power of the inverter and each phase power of the grid; if not, correcting each phase power of the grid according to the proportional coefficient between each phase power of the inverter and each phase power of the grid.

5. The CT correction calculation method for the energy storage system according to claim 4, characterized in that: When judging whether there is any missed connection and / or repeated connection of each phase CT based on the proportional coefficient between each phase power of the inverter and each phase power of the grid, if it is judged that there is any missed connection and / or repeated connection, then after adjusting the corresponding missed connection and / or repeated connection, return to step S1.

6. The CT correction calculation method for the energy storage system according to claim 5, characterized in that: The proportional coefficient between each phase power of the inverter and each phase power of the grid is used to determine whether each phase CT has missed connection and / or repeated connection, including: If there are more than two absolute values ​​of the proportional coefficients between the power of each phase of the inverter and the power of a certain phase of the power grid within the range of [1-a, 1+a], it indicates that multiple phase CTs are repeatedly connected to the power grid of this phase, and a is the first preset threshold; if the absolute values ​​of the proportional coefficients between the power of a certain phase of the inverter and the power of each phase of the power grid are all less than the second preset threshold, it indicates that the CT of this phase is missed.

7. The CT correction calculation method for the energy storage system according to claim 6, characterized in that: The value range of the first preset threshold is 0-0.2, and the value range of the second preset threshold is 0-0.

4.

8. The CT correction calculation method for the energy storage system according to claim 1, characterized in that: In step S5, the power of each phase of the grid is corrected according to the proportional coefficient between each phase power of the inverter and each phase power of the grid, in combination with the following formula: ； In the formula, Represents the corrected n Phase grid power, T is the power grid cycle, u n ( t )express t The first n Phase grid voltage, N represents the phase number of the energy storage system; i jn Indicates that the inverter j Phase output power, t The first n Current sampling value of phase CT, k jn Indicates the inverter j Phase power and n The proportionality coefficient between the phase grid powers, g jn represents the adjustment parameter, where k jn ≠0, g jn = k jn ; k jn = 0, g jn = 1.

9. An energy storage system, characterized in that: The invention comprises an inverter, a CT and a power grid, wherein each phase output end of the inverter is respectively connected to the three phases of the power grid, each phase of the sampling side of the CT is respectively connected to the three phases of the power grid, the feedback side of the CT is connected to the inverter, and the energy storage system is used to correct the power of each phase of the power grid according to the CT correction calculation method of the energy storage system according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program is configured to be executable by a processor to execute the CT correction calculation method for the energy storage system according to any one of claims 1 to 8.

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