A method and apparatus for measuring reactive inductance

Abstract

The application discloses a kind of reactive inductance measurement method and device, it is related to battery energy storage technology field, can be calculated according to the voltage drop in battery energy storage system by controlling converter, reactive inductance, and then provide data support for subsequent reactive compensation strategy and reactive power control, for example: control the first converter in multiple converters is in zero power state;In turn, start one or more converters except the first converter in multiple converters to send capacitive reactive power until the primary side excitation current of transformer is 0;According to the input terminal voltage of primary winding when primary side excitation current is 0 and the total amount of capacitive reactive power, calculate primary side excitation reactive inductance.The application compared with prior art method for calculating reactive inductance, the accuracy of calculation result is high, does not depend on winding number and other data difficult to obtain directly, does not need to high-speed sampling to current, also does not need manual identification unsaturated phase current interval, simple operation and lower error.

Description

Technical Field

[0001] This application relates to the field of battery energy storage technology, and in particular to a method and apparatus for measuring reactive inductance. Background Technology

[0002] With the accelerated construction of new power systems based on new energy sources, the role of battery energy storage systems is becoming increasingly prominent. In practical applications, most battery energy storage systems connect multiple small-capacity converter units in parallel to the grid through multi-winding transformers, thus integrating multiple small-capacity converter units into a single large-capacity system.

[0003] However, transformers in battery energy storage systems have inherent electromagnetic characteristics: First, both the primary and secondary windings have leakage inductance, which generates inductive reactive power when current flows through the leakage inductance; second, inductive reactive power is also generated during the primary winding excitation process of the transformer. These inductive reactive power components are undesirable reactive power in battery energy storage systems, which not only reduce the power factor of the system but also interfere with power control accuracy, causing deviations between the actual output power and the control command.

[0004] Therefore, in order to eliminate the impact of the aforementioned undesirable reactive power on power control, it is necessary to accurately calculate the leakage inductance of the transformer's primary side, the leakage inductance of the secondary side, and the inductance value corresponding to the primary side excitation reactive power, thereby providing data support for subsequent reactive power compensation strategies and reactive power control.

[0005] Existing methods for calculating the primary and secondary leakage inductance of transformers have the following drawbacks: First, the accuracy of the calculation results is low; second, they rely on data that is difficult to obtain directly, such as the number of winding turns; third, they require high-speed sampling of the current; and fourth, they require manual identification of the unsaturated phase current range, which is complex to operate and prone to human error. Summary of the Invention

[0006] This application provides a method and apparatus for measuring reactive inductance. By controlling the converter and performing simple operations such as voltage drop, it can online measure and calculate with high accuracy the primary leakage inductance, secondary leakage inductance, inductance value corresponding to primary excitation reactive power of the transformer, and the line inductance value between the transformer and the power grid, thereby providing data support for subsequent reactive power compensation strategies and reactive power control.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] Firstly, a method for measuring reactive inductance is provided. This method is used to obtain the reactive inductance in a battery energy storage system. The battery energy storage system includes a power grid, a transformer, and multiple converters. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are respectively connected to multiple converters. The method includes: controlling a first converter among the multiple converters to a zero-power state; connecting the first converter to a first secondary winding among the multiple secondary windings; starting a second converter among the multiple converters to generate a first capacitive reactive power, and gradually increasing the magnitude of the first capacitive reactive power; measuring the primary excitation current of the transformer as a first current value; if the first current value is 0, obtaining the total first capacitive reactive power, which is the magnitude of the first capacitive reactive power already generated; measuring the first input terminal voltage of the primary winding; calculating the primary excitation reactive inductance based on the first input terminal voltage and the total first capacitive reactive power; if the first current value is not 0, and the first capacitive reactive power has reached the maximum capacitive inductance of the second converter; To generate the second capacitive reactive power, the third converter among multiple converters is started, and the magnitude of the second capacitive reactive power is gradually increased. The primary winding excitation current of the transformer is measured as the second current value. If the second current value is 0, the total amount of the second capacitive reactive power is obtained, which is the sum of the first and second capacitive reactive power already generated. The voltage at the second input terminal of the primary winding is measured. Based on the second input terminal voltage and the total amount of the second capacitive reactive power, the primary excitation reactive power inductance is calculated. If the second current value is not 0, and the second capacitive reactive power has reached the maximum capacitive reactive power of the third converter, one or more other converters among the multiple converters are started sequentially to generate capacitive reactive power until the primary winding excitation current of the transformer is 0. The total amount of the third capacitive reactive power is obtained, which is the sum of the first, second, and capacitive reactive power already generated, and the capacitive reactive power generated by one or more other converters. The voltage at the third input terminal of the primary winding is measured. Based on the third input terminal voltage and the total amount of the third capacitive reactive power, the primary excitation reactive power inductance is calculated.

[0009] The solution provided in the first aspect above, when the primary winding of the transformer is connected to the power grid and multiple secondary windings of the transformer are connected to multiple converters, and there is no current between the power grid and the transformer, controls the first converter connected to the first secondary winding among the multiple secondary windings to be in a zero-power state, and starts multiple converters other than the first converter to generate capacitive reactive power. Since there is no current between the power grid and the transformer, the voltage of the primary leakage inductance is 0, and the primary excitation voltage is equal to the system voltage at the point of common coupling (PCC). The primary excitation voltage dominates the main magnetic flux, and the secondary voltage is coupled to the primary side through the main magnetic flux. At this time, the second converter among the multiple converters can be controlled to generate the first capacitive reactive power, and the magnitude of the first capacitive reactive power is gradually increased. Since the capacitive reactive power generated by the converter can offset the inductive reactive power generated by the primary excitation, the primary excitation current can be measured at the same time as the second converter generates the first capacitive reactive power. If the measured first current value is 0, it indicates that the second converter has generated the first capacitive reactive power. The magnitude of the first capacitive reactive power is just enough to offset the inductive reactive power generated by the primary winding excitation. Therefore, the magnitude of the inductive reactive power generated by the primary winding excitation is equal to the magnitude of the first capacitive reactive power already generated by the second converter. Based on the measured voltage at the first input terminal of the primary winding and the total amount of the first capacitive reactive power (i.e., the magnitude of the first capacitive reactive power already generated, which is also the magnitude of the inductive reactive power generated by the primary winding excitation), the primary winding excitation reactive power inductance can be calculated. If the measured first current value is not zero, and the first capacitive reactive power has reached the maximum capacitive capacity of the second converter... The reactive power reading indicates that the magnitude of the first capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter) is insufficient to offset the inductive reactive power generated by the primary excitation. Therefore, a third converter among multiple converters can be started to generate a second capacitive reactive power, and the magnitude of the second capacitive reactive power should be gradually increased while simultaneously measuring the primary excitation current. If the measured second current value is 0, it indicates that the second capacitive reactive power generated by the third converter is less than the first capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter). The sum of the two can just cancel out the inductive reactive power generated by the primary side excitation. Therefore, the magnitude of the inductive reactive power generated by the primary side excitation is equal to the sum of the second capacitive reactive power generated by the third converter and the first capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter). Based on the measured voltage at the second input terminal of the primary winding and the total amount of the second capacitive reactive power (i.e., the sum of the second and first capacitive reactive power generated, which is also the magnitude of the inductive reactive power generated by the primary side excitation), the primary side excitation inductance can be calculated.If the measured second current value is not 0, and the second capacitive reactive power has reached the maximum capacitive reactive power of the third converter, it means that the magnitude of the second capacitive reactive power already generated by the third converter (i.e., the maximum capacitive reactive power of the third converter) and the sum of the maximum capacitive reactive power of the second converter are insufficient to offset the inductive reactive power generated by the primary excitation. In this case, one or more other converters among the multiple converters can be started to generate capacitive reactive power until the current of the primary excitation is 0. At this time, the sum of the first capacitive reactive power, the second capacitive reactive power, and the capacitive reactive power generated by one or more other converters is equal to the magnitude of the inductive reactive power generated by the primary excitation. Based on the measured third input terminal voltage of the primary winding and the total third capacitive reactive power (i.e., the sum of the first capacitive reactive power, the second capacitive reactive power, and the capacitive reactive power generated by one or more other converters, which is also the magnitude of the inductive reactive power generated by the primary excitation), the inductance of the primary excitation reactive power can be calculated. Thus, by controlling the converter to generate capacitive reactive power and simultaneously measuring whether the primary excitation current is zero, the magnitude of the inductive reactive power generated by the primary excitation can be obtained. Based on the input voltage of the primary winding and the magnitude of the inductive reactive power generated by the primary excitation, the specific value of the reactive inductance of the primary excitation can be accurately calculated, thereby providing data support for subsequent reactive power compensation strategies and reactive power control.

[0010] As an example, the zero-power state mentioned above refers to a situation where there is no power transfer between the first converter and the grid, and it only maintains its own minimum operating power consumption.

[0011] As an example, when the aforementioned control converter outputs capacitive reactive power, the magnitude of the capacitive reactive power can start from 0 and gradually increase; it can also start from any value less than the maximum capacitive reactive power and gradually increase. This application does not limit this.

[0012] As an example, the magnitudes of the first and second current values ​​mentioned above are different.

[0013] As an example, the second, third, and one or more other converters that generate capacitive reactive power do not include the first converter, which is in a zero-power state, and its connected first secondary winding can also be referred to as the measuring winding.

[0014] In one possible implementation of the first aspect, the formula for calculating the primary-side excitation reactive inductance is as follows:

[0015] ;

[0016] in, For primary-side excitation reactive inductance, superscript Indicates the original edge, subscript Indicates excitation; This is the input voltage of the primary winding when the primary excitation current is 0. (Superscript) Indicates the original edge, subscript Indicates the first measurement of the first primary winding, subscript The first This indicates the primary winding number, i.e., the first primary winding, the second... This indicates the first measurement of the first primary winding; The total capacitive reactive power refers to the magnitude of the inductive reactive power generated by primary-side excitation. (Subscript) Indicates excitation; ω is the angular frequency of alternating current.

[0017] As an example, the above The voltage at the first input terminal. This represents the total amount of the first capacitive reactive power; or, The voltage at the second input terminal. This is the total amount of the second capacitive reactive power; or, The voltage at the third input terminal. This represents the total reactive power of the third capacitive capacitor.

[0018] In one possible implementation of the first aspect, the method further includes: measuring the first output terminal voltage of the first secondary winding; and obtaining the turns ratio based on the input terminal voltage of the primary winding and the first output terminal voltage when the primary excitation current is 0. .

[0019] As an example, the ratio The calculation formula is:

[0020] ;

[0021] in, This represents the input voltage of the primary winding when the primary excitation current is 0. For an explanation of superscripts and subscripts, please refer to the above explanation. The relevant descriptions will not be repeated here; The voltage at the first output terminal is indicated by the superscript. Indicates secondary edge, subscript This indicates the first measurement of the output voltage of the first secondary winding (i.e., the measuring winding), with the subscript... In Indicates the first secondary winding (i.e., the measuring winding), subscript In This indicates the first measurement of the first secondary winding (i.e., the measurement winding).

[0022] As an example, when the first converter is in a zero-power state, the voltage at the first output terminal of the first secondary winding connected to the first converter needs to be balanced with the voltage at the input terminal of the first converter. Therefore, the voltage at the first output terminal of the first secondary winding is equal to the voltage at the input terminal of the first converter.

[0023] In one possible implementation of the first aspect, the method includes: controlling the other converters (excluding the first converter) among a plurality of converters to output capacitive reactive power at the maximum capacitive reactive power; measuring the fourth input terminal voltage of the primary winding, the grid-connected current of the primary winding, and the second output terminal voltage of the first secondary winding; and based on the input terminal voltage and turns ratio of the primary winding when the primary excitation current is 0. The second output voltage and grid-connected current are used to calculate the primary leakage inductance. It can be understood that when controlling multiple converters (excluding the first converter) to output capacitive reactive power at their maximum capacitive reactive power, the input voltage of the primary winding will significantly increase, and the output voltage of the first auxiliary winding will also change. Therefore, the primary leakage inductance can be calculated based on the voltage change across it, and the line inductance between the transformer and the grid can also be calculated based on the voltage change at the primary input. .

[0024] In one possible implementation of the first aspect, the formula for calculating the primary leakage inductance is as follows:

[0025] ;

[0026] in, For the original edge leakage, superscript Indicates the original edge, subscript Indicates leakage; For variable ratio; The voltage at the second output terminal is indicated by the superscript. Indicates secondary edge, subscript This indicates the second measurement of the output voltage of the first secondary winding (i.e., the measuring winding), with the subscript... In Indicates the first secondary winding (i.e., the measuring winding), subscript In This indicates that the second measurement is performed on the first secondary winding (i.e., the measurement winding). This is the input voltage of the primary winding when the primary excitation current is 0. For further information, please refer to the above descriptions. The relevant descriptions will not be repeated here; The angular frequency of alternating current; This is the grid-connected current.

[0027] In one possible implementation of the first aspect, the method further includes: calculating the line inductance between the transformer and the power grid according to the following formula. :

[0028]

[0029] in, The voltage at the fourth input terminal is indicated by the superscript. Indicates the original edge, subscript Indicates the second measurement of the first primary winding, subscript In Indicates the primary winding number, i.e., the first primary winding, subscript. In This indicates the second measurement of the first primary winding; This is the grid-connected current; This is the input voltage of the primary winding when the primary excitation current is 0. For further information, please refer to the above descriptions. The relevant descriptions will not be repeated here.

[0030] As an example, the line inductance between the transformer and the power grid also generates inductive reactive power. By calculating the specific value of the line inductance between the transformer and the power grid, data support can be provided for subsequent reactive power compensation strategies and reactive power control.

[0031] In one possible implementation of the first aspect, the method further includes: measuring the output terminal voltages corresponding to each of the multiple secondary windings when the primary excitation current is 0; controlling a first part of the converters in the multiple converters to generate capacitive reactive power and a second part of the converters to generate inductive reactive power, wherein the magnitude of the capacitive reactive power generated by the first part of the converters and the magnitude of the inductive reactive power generated by the second part of the converters are the same; measuring the magnitude of the capacitive reactive power generated by each converter in the first part of the converters and the magnitude of the inductive reactive power generated by each converter in the second part of the converters; measuring the output terminal voltages corresponding to each of the first secondary windings connected to the first part of the converters, in order to The output voltages of the secondary windings of the second part of the converter are respectively connected to the second part of the converter. Based on the magnitude of the capacitive reactive power generated by each converter in the first part of the converter, the output voltages of the secondary windings of the first part of the converter, and the output voltages of the secondary windings of the first part of the converter when the primary excitation current is 0, the secondary leakage inductance of each secondary winding of the first part of the converter is calculated. Based on the magnitude of the inductive reactive power generated by each converter in the second part of the converter, the output voltages of the secondary windings of the second part of the converter, and the output voltages of the secondary windings of the second part of the converter when the primary excitation current is 0, the secondary leakage inductance of each secondary winding of the second part of the converter is calculated. It can be understood that when the primary excitation current is 0, the output voltages corresponding to the first and second secondary windings are ideal coupling voltages without the influence of leakage inductance. When the magnitude of the capacitive reactive power generated by the first converter and the magnitude of the inductive reactive power generated by the second converter are the same (i.e., the total reactive power of the converter is 0), the measured output voltages corresponding to the first secondary windings connected to the first converter and the second secondary windings connected to the second converter are voltages that only include the influence of primary leakage inductance. The voltage difference between these two measurements is the voltage of the primary leakage inductance, which is the secondary leakage inductance referred to the primary side. Therefore, by controlling the electromotive force of the primary and secondary windings to remain constant, adjusting the inductive and capacitive reactive power generated by the converter connected to the secondary winding, and by detecting the voltage drop of the secondary leakage inductance during operation, the secondary leakage inductance can be calculated.

[0032] In one possible implementation of the first aspect, the formula for calculating the secondary leakage inductance is as follows:

[0033]

[0034] in, For the Nth secondary side leakage inductance, superscript Indicates secondary edge, subscript The subscript represents the leakage inductance of the Nth secondary winding. In Indicates leakage, subscript In This indicates the number of the secondary winding, i.e., the Nth secondary winding, where N is an integer greater than or equal to 1; The superscript represents the output voltage of the Nth secondary winding obtained from the second measurement. Indicates secondary edge, subscript This indicates the second measurement of the Nth primary winding, with the subscript indicating the measurement. In Indicates the secondary winding number, i.e., the Nth primary winding, subscript In This indicates that the second measurement was taken of the Nth primary winding; This refers to the output voltage of the Nth secondary winding obtained from the first measurement, i.e., the output voltage of the Nth secondary winding when the primary excitation current is 0; for an explanation of superscripts and subscripts, please refer to the above explanation. The relevant information will not be repeated here; The angular frequency of alternating current; This represents the magnitude of the inductive reactive power generated by the Nth converter, where the subscript N indicates the Nth converter.

[0035] Secondly, a device for measuring leakage inductance and reactive inductance is provided, the device comprising:

[0036] The control module is used to control one or more modules in the battery energy storage system. The battery energy storage system includes a power grid, a transformer, and multiple converters. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are connected to multiple converters respectively.

[0037] A measurement module for performing voltage and / or current measurements during the control of one or more modules in a battery energy storage system;

[0038] The processing module is used to determine one or more of the following reactive inductances of the battery energy storage system based on the process of the control module controlling one or more modules in the battery energy storage system and the measurement results of the measurement module: primary side excitation reactive inductance, primary side leakage inductance, and secondary side leakage inductance.

[0039] In one possible implementation, the control model can be used to control the first converter among multiple converters to be in a zero-power state, the first converter being connected to the first secondary winding among multiple secondary windings; the second converter among multiple converters is started to generate the first capacitive reactive power, and the magnitude of the first capacitive reactive power is gradually increased. The measurement module can be used to measure the primary excitation current of the transformer as the first current value to obtain the total amount of the first capacitive reactive power.

[0040] In one possible implementation, the control module can be used to control the first converter among multiple converters to be in a zero-power state. The first converter is connected to the first secondary winding among multiple secondary windings. One or more other converters besides the first converter are sequentially started to generate capacitive reactive power, and the magnitude of the capacitive reactive power is gradually increased until the primary excitation current of the transformer is 0. The measurement module can be used to measure the primary excitation current of the transformer at this time. When the primary excitation current is 0, the total capacitive reactive power (i.e., the first total capacitive reactive power, or the second total capacitive reactive power, or the third total capacitive reactive power) is obtained. The total capacitive reactive power is the magnitude of the generated capacitive reactive power. When the primary excitation current is 0, the input terminal voltage of the primary winding (i.e., the first input terminal voltage, or the second input terminal voltage, or the third input terminal voltage) and the first output terminal voltage of the first secondary winding are measured. The processing module can be used to calculate the primary excitation reactive inductance based on the input voltage and the total capacitive reactive power; and to calculate the input voltage and the first output voltage of the primary winding when the primary excitation current is 0.

[0041] In one possible implementation, the control module can also be used to control the other converters (excluding the first converter) among multiple converters to output capacitive reactive power at their maximum capacitive reactive power. The measurement module can also be used to measure the input voltage of the primary winding (i.e., the fourth input voltage), the grid-connected current of the primary winding, and the second output voltage of the first secondary winding at this time. The processing module can also determine the input voltage and turns ratio of the primary winding when the primary excitation current is 0. Calculate the primary leakage inductance based on the second output voltage and grid current; calculate the line inductance between the transformer and the grid based on the fourth input voltage, the input voltage of the primary winding when the primary excitation current is 0, and the grid current.

[0042] In one possible implementation, the control module can also be used to control a first part of the converters in multiple converters to generate capacitive reactive power and a second part of the converters to generate inductive reactive power, wherein the magnitude of the capacitive reactive power generated by the first part of the converters and the magnitude of the inductive reactive power generated by the second part of the converters are the same. The measurement module can also be used to measure the output terminal voltages of each of the multiple secondary windings when the primary excitation current is 0; measure the magnitude of the capacitive reactive power generated by each converter in the first part of the converters and the magnitude of the inductive reactive power generated by each converter in the second part of the converters; and measure the output terminal voltages of the first secondary windings connected to the first part of the converters and the second secondary windings connected to the second part of the converters. The control module can also be used to calculate the secondary leakage inductance of each secondary winding in the first part of the converter based on the magnitude of the capacitive reactive power generated by each converter in the first part of the converter, the corresponding output terminal voltage of each secondary winding in the first part of the converter, and the corresponding output terminal voltage of each secondary winding in the first part of the converter when the primary excitation current is 0; and to calculate the secondary leakage inductance of each secondary winding in the second part of the converter based on the magnitude of the inductive reactive power generated by each converter in the second part of the converter, the corresponding output terminal voltage of each secondary winding in the second part of the converter, and the corresponding output terminal voltage of each secondary winding in the second part of the converter when the primary excitation current is 0.

[0043] Thirdly, this application provides a readable storage medium storing a program and / or instructions that, when executed by a processor, implement the methods described in the first aspect and any possible implementation thereof.

[0044] Fourthly, a computer program product containing instructions is provided, which, when run on a computer, causes the computer to implement the methods of the first aspect and any possible implementation thereof.

[0045] Fifthly, a chip system is provided, comprising processing circuitry and a storage medium storing computer program instructions; when executed by the processor, the computer program instructions implement the methods described in the first aspect and any possible implementation thereof. The chip system may be composed of chips or may include chips and other discrete devices.

[0046] This application enables the determination of the magnitude of inductive reactive power generated by the primary winding by controlling the converter to output capacitive reactive power and simultaneously measuring whether the primary excitation current is zero. Based on the input voltage of the primary winding and the magnitude of the inductive reactive power generated by the primary excitation, the specific value of the reactive inductance of the primary excitation can be accurately calculated. Furthermore, by controlling the other converters (excluding the first converter) to output capacitive reactive power at their maximum capacity, and simultaneously measuring the input voltage and grid current of the primary winding and the output voltage of the first secondary winding, the specific value of the primary leakage inductance can be accurately calculated. Moreover, by adjusting the output of inductive and capacitive reactive power from the converter connected to the secondary winding while keeping the electromotive force of the primary and secondary windings constant, and by detecting the voltage drop of the secondary leakage inductance during operation, the specific value of the secondary leakage inductance can be accurately calculated. The accurately calculated reactive inductance, primary leakage inductance, and secondary leakage inductance of the primary excitation provide data support for subsequent reactive power compensation strategies and reactive power control.

[0047] Compared with existing methods for calculating reactive inductance, the solution provided in this application has high accuracy, does not rely on data that is difficult to obtain directly, such as the number of winding turns, does not require high-speed sampling of current, and does not require manual identification of unsaturated phase current ranges. It is simple to operate and has low error. Attached Figure Description

[0048] Figure 1 An architecture diagram of a battery energy storage system provided in this application embodiment;

[0049] Figure 2 A flowchart illustrating a method for measuring primary-side magnetizing inductance provided in an embodiment of this application;

[0050] Figure 3 A flowchart illustrating a method for measuring primary leakage inductance and line inductance provided in an embodiment of this application;

[0051] Figure 4 A flowchart illustrating a method for measuring secondary leakage inductance provided in an embodiment of this application;

[0052] Figure 5 This is a schematic diagram of a reactive inductance measuring device provided in an embodiment of this application. Detailed Implementation

[0053] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0054] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0055] In the technical solutions provided in this application, the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved are all information and data authorized by the user or fully authorized by all parties. The collection, storage, use, processing, transmission, provision and disclosure of the above information and data all comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0056] It should be noted that in the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, it does not mean that the applicant has used or necessarily used the solution.

[0057] This application provides a method for measuring reactive inductance. Figure 1 An architecture diagram of a battery energy storage system provided in this application embodiment is shown below. Figure 1 As shown, a battery energy storage system may include a power grid, a transformer, multiple converters, and multiple energy storage batteries. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are connected to multiple converters. For example, as... Figure 1 As shown, the primary winding can be connected to the point of common connection (PCC); multiple secondary windings can be connected to converter 1, converter 2, converter 3... converter N; converter 1 is connected to energy storage battery 1, converter 2 is connected to energy storage battery 2, converter 3 is connected to energy storage battery 3... converter N is connected to energy storage battery N. It is the equivalent voltage source of the power grid at the PCC point, and the PCC point can represent the power grid.

[0058] In this system, the power grid can serve as the energy exchange carrier for the battery energy storage system, responsible for both energy input and energy output.

[0059] As an example, in a charging scenario, the power grid can replenish energy for energy storage batteries.

[0060] As an example, in a discharge scenario, the power grid can receive the electrical energy released by the energy storage battery and transmit it to the power consumer.

[0061] Transformers can convert voltage levels to match the voltage requirements of converters, power grids, and energy storage batteries.

[0062] As an example, such as Figure 1 As shown, a transformer can connect multiple converters to the grid, integrating multiple small-capacity converters into a single large-capacity system.

[0063] Multiple converters can achieve electrical energy form conversion and power control, including active power control and reactive power control.

[0064] As an example, such as Figure 1 As shown, in a charging scenario, the converter can convert the alternating current (AC) from the power grid into direct current (DC) that is acceptable to the energy storage battery, and ensure the battery is charged safely and efficiently by controlling the charging current and voltage.

[0065] As an example, such as Figure 1 As shown, in a discharge scenario, the converter can convert the direct current (DC) output from the energy storage battery into alternating current (AC) that is in the same frequency and phase as the power grid, ensuring that the power is smoothly connected to the power grid.

[0066] As an example, a converter can respond to grid dispatch commands, regulate charging and discharging power, and control active and reactive power.

[0067] Multiple energy storage batteries can be used to store and release electrical energy.

[0068] As an example, the energy storage battery can be a flow battery, which can store electrical energy in a liquid electrolyte containing dissolved active materials. Through the circulation and electrochemical reaction of the electrolyte in the battery stack, the reversible conversion of electrical energy and chemical energy is achieved, thereby completing the charging and discharging process.

[0069] In one possible implementation, such as Figure 1 As shown, the working process of a battery energy storage system may include:

[0070] The energy storage battery stores direct current (DC) and inputs it into the corresponding converters. Each converter works independently, inverting the DC power into AC power that conforms to the grid standard, and adjusting the charging and discharging power according to the grid's dispatch instructions.

[0071] Multiple converters output AC power that conforms to grid standards, and their power is integrated through their respective tie lines. For example, a 100MW energy storage system can be composed of 200 500kW-class converters connected in parallel. The AC power output from each converter is collected through multiple tie lines to form a total AC power of 100MW.

[0072] The collected alternating current is transmitted to the transformer through the main connection line. After being stepped up to the high voltage level required by the power grid, it is officially connected to the power grid, realizing the grid connection of stored energy (i.e., being transmitted to the power grid when discharging) or the grid connection of power (i.e., being stored in the battery when charging).

[0073] During the operation of the aforementioned battery energy storage system, the transformer within the system exhibits inherent electromagnetic characteristics, including: leakage inductance in both the primary and secondary windings, resulting in inductive reactive power as current flows through them; inductive reactive power is also generated during the primary excitation process; and line inductance exists at the point of common connection between the transformer and the power grid, further contributing to inductive reactive power as current flows through it. These inductive reactive forces are all undesirable reactive forces in the battery energy storage system. Their presence not only reduces the power factor of the system but also interferes with power control accuracy, leading to deviations between the actual output power and the control commands.

[0074] Therefore, to eliminate the impact of the aforementioned undesirable reactive power on power control, it is first necessary to calculate the leakage inductance of the transformer's primary side, secondary side, primary side excitation reactive power, and the inductance value corresponding to the line inductance, thereby providing data support for subsequent reactive power compensation strategies and reactive power control.

[0075] Conventional methods for calculating the primary and secondary leakage inductance of transformers have shortcomings.

[0076] For example, the short-circuit measurement method calculates the primary-side combined leakage inductance and the secondary-side combined leakage inductance, but it cannot obtain the leakage inductance corresponding to multiple secondary windings respectively. Moreover, this calculation method is too simple, resulting in limited calculation accuracy.

[0077] For example, the short-circuit measurement method involves short-circuiting all secondary windings of the transformer, applying an AC voltage of rated frequency to the primary winding, adjusting the voltage to bring the primary current to its rated value, and then calculating the overall primary leakage inductance based on the measured primary voltage and current data. Similarly, by short-circuiting the primary windings again, applying an AC voltage of rated frequency to the secondary winding, and adjusting the voltage to bring the secondary current to its rated value, the overall secondary leakage inductance can be calculated based on the measured secondary voltage and current. However, this method only obtains the overall values ​​of the primary and secondary leakage inductances and cannot accurately separate the individual leakage inductances of each secondary winding, making it difficult to meet the refined parameter requirements of multi-winding transformers. Furthermore, the relatively simple design of this method results in limited accuracy of the calculation results, making it unsuitable for applications in battery energy storage systems where high accuracy of leakage inductance parameters is required.

[0078] For example, another calculation method can derive the primary leakage inductance of the target high-frequency transformer by using the correlation between the coupled inductance, the number of turns in the primary winding, the equivalent inductance of the primary winding, and the number of turns in the secondary winding. Similarly, the secondary leakage inductance can be calculated using a parametric coupling model of the coupled mutual inductance, the number of turns in the primary winding, the equivalent inductance of the secondary winding, and the number of turns in the secondary winding. Although this method solves the problem that the short-circuit measurement method cannot separate the independent leakage inductance of each winding, it requires obtaining accurate winding turns. However, in actual engineering, turns data is often difficult to obtain accurately due to reasons such as equipment manufacturer confidentiality and the difficulty of disassembling and measuring, thus limiting its applicability.

[0079] To address the aforementioned issues, this application provides a method for measuring reactive inductance that, through simple operations such as controlling the converter and adjusting voltage drop, can online measure and calculate with high accuracy the primary leakage inductance, secondary leakage inductance, inductance corresponding to primary excitation reactive power of the transformer, and the line inductance between the transformer and the power grid. This provides data support for subsequent reactive power compensation strategies and reactive power control.

[0080] like Figure 2 The diagram shown is a flowchart of a method for measuring the primary excitation inductance according to an embodiment of this application. This method can be used to obtain the reactive inductance in a battery energy storage system by measurement. The battery energy storage system includes a power grid, a transformer, and multiple converters. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are respectively connected to multiple converters. For example, in the following embodiments, the power grid may be... Figure 1 The common connection point shown may be the transformer. Figure 1 The transformer shown, the first converter may be Figure 1 The converter shown is 1, 2, 3, or N, where N is an integer greater than or equal to 1. The second converter may be... Figure 1 The other converters shown are the first converter, and the third converter may be... Figure 1 The diagram shows the converters other than the first and second converters. For a description of the various components of a battery energy storage system and its operation, please refer to the above description. Figure 1 The description will not be repeated here.

[0081] refer to Figure 2 The method for measuring reactive inductance may include steps S201-S203 and S204A-S206A, or steps S201-S203, S204B-S205B and S206B1-S208B1, or steps S201-S203, S204B-S205B and S206B2-S209B2:

[0082] S201. Control the first converter among multiple converters to be in a zero-power state. The first converter is connected to the first secondary winding among multiple secondary windings.

[0083] When the primary winding of the transformer is connected to the power grid, and multiple secondary windings of the transformer are connected to multiple converters, and there is no current between the power grid and the transformer, the first converter connected to the first secondary winding among the multiple secondary windings is controlled to be in a zero-power state.

[0084] As an example, the first converter is connected to the first secondary winding of a plurality of secondary windings. For example, the first converter may be as follows: Figure 1 The first secondary winding of any one of the multiple converters shown is connected to the first converter.

[0085] As an example, zero-power state refers to a situation where there is no power transfer between the first converter and the grid, and it only maintains its own minimum operating power consumption.

[0086] S202. Start the second converter among multiple converters to generate the first capacitive reactive power, and gradually increase the magnitude of the first capacitive reactive power.

[0087] In the above scenario, the second converter among multiple converters (excluding the first converter) is activated to generate capacitive reactive power. Since there is no current between the grid and the transformer, the voltage of the primary leakage inductance is 0, and the primary excitation voltage is equal to the system voltage at the point of common coupling (PCC). The primary excitation voltage dominates the main magnetic flux, and the secondary voltage is coupled to the primary side through the main magnetic flux. At this time, the second converter among the multiple converters can be controlled to generate the first capacitive reactive power, and the magnitude of the first capacitive reactive power can be gradually increased. The capacitive reactive power generated by the converter can be used to offset the inductive reactive power generated by the primary excitation.

[0088] As an example, the first converter is in a zero-power state, and its first secondary winding can also be called the measuring winding.

[0089] S203. Measure the primary excitation current of the transformer to obtain the first current value.

[0090] Since the capacitive reactive power generated by the converter can be used to offset the inductive reactive power generated by the primary excitation, the primary excitation current can be measured simultaneously with the first capacitive reactive power generated by the second converter. The magnitude of the inductive reactive power generated by the primary excitation can be calculated from the change in the primary excitation current. The specific calculation process is as follows:

[0091] If the first current value is 0, execute S204A-S206A;

[0092] If the first current value is not 0, and the first capacitive reactive power has reached the maximum capacitive reactive power of the second converter, execute S204B-S205B and S206B1-S208B1, or execute S204B-S205B and S206B2-S209B2.

[0093] S204A. If the first current value is 0, obtain the first total capacitive reactive power, which is the magnitude of the first capacitive reactive power already generated.

[0094] If the measured first current value is 0, it means that the magnitude of the first capacitive reactive power generated by the second converter can just offset the inductive reactive power generated by the primary excitation. Therefore, the magnitude of the inductive reactive power generated by the primary excitation is equal to the magnitude of the first capacitive reactive power generated by the second converter, which is the total amount of the first capacitive reactive power.

[0095] S205A, measures the voltage at the first input terminal of the primary winding.

[0096] After the primary excitation current becomes 0, the voltage at the first input terminal of the primary winding is measured. At this time, the voltage at the first input terminal of the primary winding is the primary excitation voltage, which is also the system voltage at the point of common connection (PCC).

[0097] S206A. Calculate the primary excitation reactive inductance based on the first input terminal voltage and the first total capacitive reactive power.

[0098] Based on the measured voltage at the first input terminal of the primary winding and the total amount of the first capacitive reactive power (i.e., the magnitude of the inductive reactive power generated by the primary excitation), the primary excitation reactive inductance can be calculated.

[0099] As an example, the formula for calculating the primary excitation reactive inductance is:

[0100]

[0101] in, For primary-side excitation reactive inductance, superscript Indicates the original edge, subscript Indicates excitation; The voltage at the first input terminal of the primary winding when the primary excitation current is 0 is indicated by the superscript. Indicates the original edge, subscript Indicates the first measurement of the first primary winding, subscript The first This indicates the primary winding number, i.e., the first primary winding, the second... This indicates the first measurement of the first primary winding; The first capacitive reactive power is the total amount of reactive power generated by primary excitation, indicated by the subscript. Indicates excitation; ω is the angular frequency of alternating current.

[0102] S204B If the first current value is not 0, and the first capacitive reactive power has reached the maximum capacitive reactive power of the second converter, start the third converter among the multiple converters to generate the second capacitive reactive power, and gradually increase the magnitude of the second capacitive reactive power.

[0103] If the measured first current value is not 0, and the first capacitive reactive power has reached the maximum capacitive reactive power of the second converter, it means that the magnitude of the first capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter) is insufficient to offset the inductive reactive power generated by the primary excitation. In this case, the third converter among the multiple converters can be started to generate the second capacitive reactive power, and the magnitude of the second capacitive reactive power can be gradually increased while the current of the primary excitation is measured.

[0104] S205B, the primary excitation current of the transformer is measured as the second current value.

[0105] If the second current value is 0, execute S206B1-S208B1;

[0106] If the second current value is not 0, and the second capacitive reactive power has reached the maximum capacitive reactive power of the second converter, execute S206B2-S209B2.

[0107] S206B1. If the second current value is 0, obtain the total amount of the second capacitive reactive power, which is the sum of the first and second capacitive reactive power that have been generated.

[0108] If the measured second current value is 0, it means that the sum of the second capacitive reactive power generated by the third converter and the first capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter) (i.e., the cumulative value of capacitive reactive power) can just offset the inductive reactive power generated by the primary excitation. Therefore, the magnitude of the inductive reactive power generated by the primary excitation is equal to the sum of the second capacitive reactive power generated by the third converter and the first capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter), which is the total amount of second capacitive reactive power.

[0109] S207B1, Measure the voltage at the second input terminal of the primary winding.

[0110] For an introduction to the voltage at the second input terminal, please refer to the description of the voltage at the first input terminal above; it will not be repeated here.

[0111] S208B1. Calculate the primary excitation reactive inductance based on the second input terminal voltage and the total amount of the second capacitive reactive power.

[0112] Based on the measured voltage at the second input terminal of the primary winding and the total amount of the second capacitive reactive power (i.e., the magnitude of the inductive reactive power generated by the primary excitation), the primary excitation reactive inductance can be calculated.

[0113] The formula for calculating the primary excitation reactive inductance can be found in the relevant description in S206A above, and will not be repeated here.

[0114] in, The voltage at the second input terminal. This represents the total amount of the second capacitive reactive power.

[0115] S206B2 If the second current value is not 0, and the second capacitive reactive power has reached the maximum capacitive reactive power of the third converter, then start one or more other converters among the multiple converters in sequence to generate capacitive reactive power.

[0116] If the measured second current value is not 0, and the second capacitive reactive power has reached the maximum capacitive reactive power of the third converter, it means that the sum of the magnitude of the second capacitive reactive power generated by the third converter (i.e., the maximum capacitive reactive power of the third converter) and the magnitude of the second capacitive reactive power generated by the second converter (i.e., the maximum capacitive reactive power of the second converter) (i.e., the cumulative value of capacitive reactive power) is insufficient to offset the inductive reactive power generated by the primary excitation. In this case, one or more other converters among the multiple converters can be started to generate capacitive reactive power.

[0117] S207B2. Until the primary excitation current of the transformer is 0, obtain the third total capacitive reactive power. The third total capacitive reactive power is the sum of the first capacitive reactive power, the second capacitive reactive power, and the capacitive reactive power generated by one or more other converters.

[0118] Until the primary excitation current is 0, the sum of the first capacitive reactive power already generated, the second capacitive reactive power already generated, and the capacitive reactive power generated by one or more other converters is equal to the magnitude of the inductive reactive power generated by the primary excitation.

[0119] S208B2, Measure the voltage at the third input terminal of the primary winding.

[0120] For an introduction to the voltage at the third input terminal, please refer to the description of the voltage at the first input terminal above; it will not be repeated here.

[0121] S209B2. Calculate the primary excitation reactive inductance based on the third input voltage and the third capacitive reactive total.

[0122] Based on the measured voltage at the third input terminal of the primary winding and the magnitude of the inductive reactive power generated by the primary excitation, the primary excitation reactive inductance can be calculated.

[0123] The formula for calculating the primary excitation reactive inductance can be found in the relevant description in S206A above, and will not be repeated here.

[0124] in, The voltage at the third input terminal. This represents the total reactive power of the third capacitive capacitor.

[0125] As an example, when the primary winding excitation current of the transformer is 0, the first output terminal voltage of the first secondary winding (i.e., the measuring winding) is measured; based on the input terminal voltage and the first output terminal voltage of the primary winding when the primary winding excitation current is 0, the turns ratio can be obtained. .

[0126] Transformer The calculation formula is:

[0127]

[0128] in, This represents the input voltage of the primary winding when the primary excitation current is 0. For an explanation of superscripts and subscripts, please refer to the above explanation. The relevant descriptions will not be repeated here; The voltage at the first output terminal is indicated by the superscript. Indicates secondary edge, subscript This indicates the first measurement of the output voltage of the first secondary winding (i.e., the measuring winding), with the subscript... In Indicates the first secondary winding (i.e., the measuring winding), subscript In This indicates the first measurement of the first secondary winding (i.e., the measurement winding).

[0129] In some embodiments, such as Figure 3 As shown, the primary leakage inductance and the line inductance between the transformer and the power grid can also be obtained by performing the following steps S301-S303. :

[0130] S301. Control the other converters among multiple converters, except for the first converter, to output capacitive reactive power according to the maximum capacitive reactive power.

[0131] When controlling all converters except the first converter to output capacitive reactive power at their maximum capacitive reactive power, the input voltage of the primary winding will increase significantly, and the output voltage of the first auxiliary winding will also change. Therefore, the primary leakage inductance can be calculated based on the voltage change across the primary leakage inductance, and the line inductance between the transformer and the power grid can also be calculated based on the voltage change at the primary input. .

[0132] S302. Measure the voltage at the fourth input terminal of the primary winding, the grid-connected current of the primary winding, and the voltage at the second output terminal of the first secondary winding.

[0133] S303, Based on the input voltage and turns ratio of the primary winding when the primary excitation current is 0. Calculate the primary leakage inductance based on the second output voltage and grid current.

[0134] As an example, the formula for calculating the primary side leakage inductance is:

[0135]

[0136] in, For the original edge leakage, superscript Indicates the original edge, subscript Indicates leakage; For variable ratio; The voltage at the second output terminal is indicated by the superscript. Indicates secondary edge, subscript This indicates the second measurement of the output voltage of the first secondary winding (i.e., the measuring winding), with the subscript... In Indicates the first secondary winding (i.e., the measuring winding), subscript In This indicates that the second measurement is performed on the first secondary winding (i.e., the measurement winding). This is the input voltage of the primary winding when the primary excitation current is 0. For further information, please refer to the above descriptions. The relevant descriptions will not be repeated here; The angular frequency of alternating current; This is the grid-connected current.

[0137] Understandable. This represents the voltage drop corresponding to the primary leakage inductance. Wherein, The secondary voltage is transformed by the turns ratio The equivalent voltage referred to the primary side is the same as that of the primary side. The difference is essentially the voltage loss across the primary leakage inductance. Therefore, considering the grid-connected current... The leakage inductance of the primary side can be calculated by the voltage drop.

[0138] As an example, the line inductance between the transformer and the power grid also generates inductive reactive power. Based on the data obtained from the above measurements, the line inductance between the transformer and the power grid can also be calculated using the following formula. :

[0139]

[0140] in, The voltage at the fourth input terminal is indicated by the superscript. Indicates the original edge, subscript Indicates the second measurement of the first primary winding, subscript In Indicates the primary winding number, i.e., the first primary winding, subscript. In This indicates the second measurement of the first primary winding; This is the grid-connected current; This is the input voltage of the primary winding when the primary excitation current is 0. For further information, please refer to the above descriptions. The relevant descriptions will not be repeated here;

[0141] Understandable. The voltage drop across the line inductance between the transformer and the power grid, combined with the grid-connected current. The line inductance between the transformer and the power grid can be calculated by the voltage drop.

[0142] It should be noted that steps S301-S303 can be executed after step S205A, or after S207B1, or after S208B2. That is, when the primary winding excitation current of the transformer is 0, the turns ratio is obtained through the voltage at the first output terminal of the first secondary winding (i.e., the measuring winding) and the voltage at the input terminal of the primary winding when the primary excitation current is 0. Then, steps S301-S303 can be executed to obtain the primary leakage inductance and the line inductance between the transformer and the power grid.

[0143] In some embodiments, such as Figure 4 As shown, the secondary leakage inductance can also be obtained by performing the following steps S401-S406:

[0144] S401. Measure the output terminal voltage of each of the multiple secondary windings when the primary excitation current is 0.

[0145] When the primary excitation current is 0, the output voltages of the first and second secondary windings are ideal coupling voltages without leakage inductance.

[0146] S402. Control the first part of multiple converters to generate capacitive reactive power and the second part of converters to generate inductive reactive power, wherein the magnitude of the capacitive reactive power generated by the first part of converters is the same as the magnitude of the inductive reactive power generated by the second part of converters.

[0147] S403. Measure the magnitude of capacitive reactive power generated by each converter in the first part of the converter, and the magnitude of inductive reactive power generated by each converter in the second part of the converter.

[0148] S404. Measure the output terminal voltage of the first secondary winding connected to the first part of the converter, and the output terminal voltage of the second secondary winding connected to the second part of the converter.

[0149] S405A: Based on the magnitude of the capacitive reactive power generated by each converter in the first part of the converter, the corresponding output terminal voltage of each secondary winding in the first part, and the corresponding output terminal voltage of each secondary winding in the first part when the primary excitation current is 0, calculate the secondary leakage inductance of each secondary winding in the first part.

[0150] S405B: Based on the magnitude of the inductive reactive power generated by each converter in the second part of the converter, the corresponding output terminal voltage of each secondary winding in the second part, and the corresponding output terminal voltage of each secondary winding in the second part when the primary excitation current is 0, calculate the secondary leakage inductance of each secondary winding in the second part.

[0151] When the magnitude of the capacitive reactive power generated by the first part of the converter is the same as the magnitude of the inductive reactive power generated by the second part of the converter (i.e., the total reactive power of the converter is 0), the measured output voltages of the first secondary winding connected to the first part of the converter and the second secondary winding connected to the second part of the converter only include the influence of the primary leakage inductance. The voltage difference between these two measurements is the voltage of the primary leakage inductance, which is the secondary leakage inductance referred to the primary winding. Therefore, by controlling the electromotive force of the primary and secondary windings to remain constant, the inductive and capacitive reactive power generated by the converter connected to the secondary winding can be adjusted. By detecting the voltage drop of the secondary leakage inductance during operation, the secondary leakage inductance can be calculated.

[0152] As an example, the formula for calculating the leakage inductance on the secondary side is:

[0153]

[0154] in, For the Nth secondary side leakage inductance, superscript Indicates secondary edge, subscript The subscript represents the leakage inductance of the Nth secondary winding. In Indicates leakage, subscript In This indicates the number of the secondary winding, i.e., the Nth secondary winding, where N is an integer greater than or equal to 1; The superscript represents the output voltage of the Nth secondary winding obtained from the second measurement. Indicates secondary edge, subscript This indicates the second measurement of the Nth primary winding, with the subscript indicating the measurement. In Indicates the secondary winding number, i.e., the Nth primary winding, subscript In This indicates the first measurement of the Nth primary winding; This refers to the output voltage of the Nth secondary winding obtained from the first measurement, i.e., the output voltage of the Nth secondary winding when the primary excitation current is 0; for an explanation of superscripts and subscripts, please refer to the above explanation. The relevant information will not be repeated here; The angular frequency of alternating current; This represents the magnitude of the inductive reactive power generated by the Nth converter, where the subscript N indicates the Nth converter.

[0155] As an example, the formula for calculating the leakage inductance of the first secondary winding numbered 1 is:

[0156]

[0157] It should be noted that the first secondary winding at this time is different from the first secondary winding (i.e., the measuring winding) of the first converter that is in a zero-power state. The numbering is only for example.

[0158] As an example, the formula for calculating the leakage inductance of the first secondary winding numbered 2 is:

[0159]

[0160] As an example, the formula for calculating the leakage inductance of the first secondary winding numbered 3 is:

[0161]

[0162] It should be noted that steps S401-S406 can be executed after step S205A, or after S207B1, or after S208B2. That is, when the primary winding excitation current of the transformer is 0, by measuring the output terminal voltages of the multiple secondary windings at this time, steps S401-S406 can be executed to obtain the secondary leakage inductance.

[0163] As an example, steps S301-S303 and steps S401-S406 can be performed in parallel, without any order.

[0164] like Figure 5 As shown, Figure 5 This is a schematic diagram of a reactive power inductance measuring device provided in an embodiment of this application. The reactive power inductance measuring device includes: a control module 501, a measurement module 502, and a processing module 503.

[0165] The control module 501 can be used to control one or more modules in the battery energy storage system. The battery energy storage system includes a power grid, a transformer and multiple converters. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are connected to multiple converters respectively.

[0166] The measurement module 502 can be used to perform voltage and / or current measurements during the control of one or more modules in a battery energy storage system.

[0167] The processing module 503 can determine one or more of the following reactive inductances of the battery energy storage system based on the process of the control module controlling one or more modules in the battery energy storage system and the measurement results of the measurement module: primary side excitation reactive inductance, primary side leakage inductance, and secondary side leakage inductance.

[0168] For details regarding the specific functions of the control module 501, measurement module 502, and processing module 503, please refer to the above. Figures 2-4 Each step in the process will not be described in detail here.

[0169] The reactive inductance measuring device provided in this application embodiment can execute the method shown in the above-described method embodiment. Its implementation principle and beneficial effects can be found in the relevant descriptions in the method embodiment, and will not be repeated here. Furthermore, each module in the above-described reactive inductance measuring device can be implemented entirely or partially through software, hardware, or a combination thereof. Each module can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0170] This application also provides a computer-readable storage medium storing computer instructions. When these computer instructions are executed by a processor, they are used to implement the technical solution of the reactive inductance measurement method described in the above embodiments. Specifically, when the computer instructions are executed by a processor, the computer device can execute the technical solution of the reactive inductance measurement method described in the above embodiments.

[0171] The aforementioned computer-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof. For a description of volatile or non-volatile storage devices, please refer to conventional techniques; details will not be elaborated here.

[0172] In the embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or modules, and may be electrical, mechanical, or other forms.

[0173] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to implement the solution of this embodiment according to actual needs.

[0174] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The unit composed of the above modules can be implemented in hardware or in the form of hardware plus software functional units.

[0175] The integrated modules described above, implemented as software functional modules, can be stored in a computer-readable storage medium. These software functional modules, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute some steps of the methods of the various embodiments of this application.

[0176] It should be understood that the steps of the method disclosed in the embodiments of this application can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules in the processor.

[0177] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0178] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application's patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0179] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for measuring reactive inductance, characterized in that, The method is used to obtain the reactive inductance in a battery energy storage system by measurement. The battery energy storage system includes a power grid, a transformer, and multiple converters. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are respectively connected to the multiple converters. The method includes: The first converter among the plurality of converters is controlled to be in a zero-power state, and the first converter is connected to the first secondary winding among the plurality of secondary windings; Start the second converter among the plurality of converters to generate the first capacitive reactive power, and gradually increase the magnitude of the first capacitive reactive power; The primary excitation current of the transformer is measured as the first current value; If the first current value is 0, obtain the first total capacitive reactive power, which is the magnitude of the first capacitive reactive power already generated; measure the first input terminal voltage of the primary winding; calculate the primary excitation reactive inductance based on the first input terminal voltage and the first total capacitive reactive power. If the first current value is not 0, and the first capacitive reactive power has reached the maximum capacitive reactive power of the second converter, the third converter among the plurality of converters is started to generate the second capacitive reactive power, and the magnitude of the second capacitive reactive power is gradually increased. The primary excitation current of the transformer is measured as the second current value; If the second current value is 0, obtain the second total capacitive reactive power, which is the sum of the first and second capacitive reactive power that have been generated; measure the voltage at the second input terminal of the primary winding; calculate the primary excitation reactive inductance based on the second input terminal voltage and the second total capacitive reactive power. If the second current value is not 0, and the second capacitive reactive power has reached the maximum capacitive reactive power of the third converter, then one or more other converters among the plurality of converters are started in sequence to generate capacitive reactive power until the primary excitation current of the transformer is 0, and the total third capacitive reactive power is obtained. The total third capacitive reactive power is the sum of the first capacitive reactive power, the second capacitive reactive power, and the capacitive reactive power generated by the other one or more converters. The third input terminal voltage of the primary winding is measured. Based on the third input terminal voltage and the total third capacitive reactive power, the primary excitation reactive power inductance is calculated.

2. The method according to claim 1, characterized in that, The formula for calculating the primary-side excitation reactive inductance is: ； in, The primary side reactive inductance; The input voltage of the primary winding when the primary excitation current is 0; This refers to the total amount of capacitive reactive power. ω is the angular frequency of alternating current.

3. The method according to claim 1 or 2, characterized in that, The method further includes: Measure the voltage at the first output terminal of the first secondary winding; The turns ratio is obtained based on the input voltage of the primary winding and the first output voltage when the primary excitation current is 0. .

4. The method according to claim 3, characterized in that: Control the other converters among the plurality of converters, except for the first converter, to output capacitive reactive power at the maximum capacitive reactive power; Measure the voltage at the fourth input terminal of the primary winding, the grid-connected current of the primary winding, and the voltage at the second output terminal of the first secondary winding; Based on the input terminal voltage of the primary winding when the primary excitation current is 0, and the turns ratio The primary leakage inductance is calculated using the second output voltage and the grid-connected current.

5. The method according to claim 4, characterized in that, The formula for calculating the primary leakage inductance is: ； in, The original edge leakage inductance; For variable ratio; The voltage at the second output terminal. For grid-connected current, The angular frequency of the alternating current, the The input voltage of the primary winding is given when the primary excitation current is 0.

6. The method according to claim 4 or 5, characterized in that, The method further includes: The line inductance between the transformer and the power grid is calculated using the following formula. : in, This is the voltage at the fourth input terminal. For the grid-connected current, the The input voltage of the primary winding is given when the primary excitation current is 0.

7. The method according to claim 6, characterized in that, The method further includes: Measure the output terminal voltage of each of the multiple secondary windings when the primary excitation current is 0; The first part of the multiple converters is controlled to generate capacitive reactive power, and the second part of the converters generates inductive reactive power. The magnitude of the capacitive reactive power generated by the first part of the converters is the same as the magnitude of the inductive reactive power generated by the second part of the converters. Measure the magnitude of capacitive reactive power generated by each converter in the first part of the converter, and the magnitude of inductive reactive power generated by each converter in the second part of the converter. Measure the output terminal voltage of the first secondary winding connected to the first part of the converter, and the output terminal voltage of the second secondary winding connected to the second part of the converter. Based on the magnitude of the capacitive reactive power generated by each converter in the first part of the converter, the output terminal voltage of each of the secondary windings in the first part, and the output terminal voltage of each of the secondary windings in the first part when the primary excitation current is 0, calculate the secondary leakage inductance of each of the secondary windings in the first part. Based on the magnitude of the inductive reactive power generated by each converter in the second part of the converter, the output terminal voltage of each secondary winding of the second part, and the output terminal voltage of each secondary winding of the second part when the primary excitation current is 0, calculate the secondary leakage inductance of each secondary winding of the second part.

8. The method according to claim 7, characterized in that: The formula for calculating the secondary leakage inductance is: ； in, For the Nth secondary side leakage inductance; The output voltage of the Nth secondary winding is given when the magnitude of the capacitive reactive power generated by the first part of the converter and the magnitude of the inductive reactive power generated by the second part of the converter are the same. The output voltage of the Nth secondary winding when the primary excitation current is 0. The angular frequency of alternating current. This represents the magnitude of the inductive reactive power generated by the Nth converter.

9. A device for measuring reactive inductance, characterized in that, The measuring device includes a control module, a measuring module, and a processing module, wherein the control module, the measuring module, and the processing module are used to work together to implement the method for measuring reactive inductance as described in any one of claims 1-8; The control module is specifically used to control one or more modules in the battery energy storage system. The battery energy storage system includes a power grid, a transformer, and multiple converters. The transformer includes a primary winding and multiple secondary windings. The primary winding is connected to the power grid, and the multiple secondary windings are respectively connected to the multiple converters. The measurement module is specifically used to perform voltage and / or current measurements during the process of controlling one or more modules in the battery energy storage system. The processing module is specifically used to determine one or more of the following reactive inductances of the battery energy storage system by calculation based on the measurement results of the measurement module: primary side excitation reactive inductance, primary side leakage inductance, and secondary side leakage inductance.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer program instructions that, when executed by a processing circuit, implement the method as described in any one of claims 1-8.

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