CN114142477B - Three-phase zero voltage ride through reactive current calculation method and system based on voltage section prolongation - Google Patents

Abstract

The application discloses a three-phase zero voltage ride through reactive current calculation method and a system based on voltage section prolongation, wherein the method comprises the steps of obtaining test data of an energy storage power station three-phase zero voltage ride through test; positioning a voltage drop section according to the test data, taking three-phase balanced voltage data with specified duration before the voltage drop section as a fitting data source, and performing function fitting according to the fitting data source to obtain a positive sequence voltage fitting function; positioning a current surge section according to the test data, taking current data of the current surge section as a fitting data source, and performing function fitting according to the fitting data source to obtain a positive sequence current fitting function; and in the voltage drop section, projecting the fitted positive sequence current in the positive sequence current fitting function to the fitted positive sequence voltage in the positive sequence voltage fitting function to obtain the positive sequence reactive current, so that the positive sequence reactive current quantitative calculation of the three-phase zero voltage ride through test of the energy storage station can be realized, and the result of the three-phase zero voltage ride through test is quantitatively analyzed.

Description

Calculation method of three-phase zero-voltage ride-through reactive current based on voltage section continuation and its system

technical field

The invention relates to the technical field of power systems, in particular to a three-phase zero-voltage ride-through reactive current calculation method and system based on voltage section extension.

Background technique

The large-scale development of electrochemical energy storage has put forward higher and higher requirements for the functions of control equipment. The current national standards and industry standards require that when the grid voltage drops, the energy storage power station should have low voltage ride-through capability, that is, to ensure that during the grid drop, The power conversion system (PCS) of the energy storage station should not run off the grid as required, and at the same time provide reactive current support for the grid. Therefore, in the process of low voltage ride through, the main phenomenon is the drop of voltage, accompanied by the sudden increase of current. For energy storage stations, low-voltage ride-through capability is a necessary core function, and low-voltage ride-through test is a key test to test the performance of PCS. The current standard requires the calculation of positive-sequence reactive current during low-voltage ride-through to evaluate the reactive power support capability, but there is no clear statement on the calculation method of positive-sequence reactive current in the case of three-phase zero-voltage ride-through. During non-zero voltage crossing, the voltage drop is not deep, and conventional voltage transformers can accurately calculate the voltage amplitude and phase, but during three-phase zero voltage crossing, the three-phase voltage amplitude has dropped to near zero, and the power grid The voltage waveform has been distorted, and the phase calculation cannot be performed based on the measured value of the voltage transformer. From the perspective of the grid side, the output voltage amplitude and phase of the generator remain stable. The three-phase zero voltage ride through process only changes the voltage at the point of drop. When the drop occurs, the output voltage of the generator in the grid is the same as before the drop. Use the generator outlet voltage as the voltage reference. For PCS, since the actual voltage cannot be sampled in the three-phase zero voltage drop section, the voltage information before the fault will be kept in the control algorithm and extended to the fault section, and the normal voltage fitted according to the fault section Calculate the control quantity of reactive current. Therefore, according to the fact that the generator output voltage is consistent before and after the drop, and the implementation of the actual PCS control algorithm, the voltage section before the drop can be extended and the voltage section after the virtual drop can be used as a normal voltage section for positive sequence Calculation of work current.

Therefore, according to the requirements for positive sequence reactive current calculation in energy storage station zero voltage ride through, a three-phase zero voltage ride through reactive current calculation method based on voltage section continuation is needed to ensure the low voltage ride through energy storage station. The three-phase zero voltage crossing results in the test are quantitatively calculated to provide an accurate reference for judging the specific performance of the equipment. At present, the relevant existing technologies are: Existing technology [1]: Li Jiaman, Wan Wenjun, Su Wei, etc. Design and test of large-capacity energy storage mobile grid-connected test device [J]. Guangdong Electric Power. 2020, 33(10):9-15. Existing technology [2]: Cao Lei, Qin Xiaodi, Xia Lie, etc. Photovoltaic inverter low-voltage ride-through test system based on virtual instrument technology [J]. Electric Measurement and Instrumentation. 2015, 52(14):71-75. Among them, the prior art [1] designed a mobile test device suitable for grid-connected detection of large-capacity energy storage systems, and carried out low-voltage ride-through tests on site. The designed device can simulate different Fault type, completed various tests of low voltage ride through, but failed to explain the analysis method of the results of three-phase zero voltage ride through. Existing technology [2] designed a photovoltaic inverter low-voltage ride-through test system based on virtual instrument technology to realize real-time monitoring of AC side voltage and current and evaluation of test results during the low-voltage ride-through test process of photovoltaic inverters. The calculation method of key indicators such as active power recovery and dynamic reactive power support of photovoltaic inverter low-voltage ride-through test is studied, but the measurement and analysis of three-phase zero-voltage ride-through is not elaborated.

Contents of the invention

Technical problem to be solved by the present invention: Aiming at the above-mentioned problems of the prior art, a three-phase zero-voltage ride-through reactive current calculation method and system based on voltage section extension is provided. The present invention can realize three-phase zero-voltage in energy storage stations Quantitative calculation of the positive sequence reactive current of the ride-through test, and quantitative analysis of the results of the three-phase zero-voltage ride-through test.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A three-phase zero-voltage ride-through reactive current calculation method based on voltage section extension, including:

1) Obtain the test data of the three-phase zero-voltage ride-through test of the energy storage power station;

2) Locate the voltage drop section according to the test data, take the three-phase balanced voltage data of the specified time before the voltage drop section as the fitting data source, and perform function fitting according to the fitting data source to obtain the positive sequence voltage fitting function; The test data locates the current sudden increase section, takes the current data of the current sudden increase section as the fitting data source, and performs function fitting according to the fitting data source to obtain the positive sequence current fitting function;

3) In the voltage drop section, project the fitted positive-sequence current in the positive-sequence current fitting function to the fitting positive-sequence voltage in the positive-sequence voltage fitting function to obtain the positive-sequence reactive current.

Optionally, before step 1), a step of performing a three-phase zero-voltage ride-through test on the energy storage power station to obtain test data of the three-phase zero-voltage ride-through test is also included.

Optionally, the value range of the specified duration in step 2) is 0.5-1.5s.

Optionally, the value of the duration specified in step 2) is 1s.

Optionally, the test data of the three-phase zero-voltage ride-through test includes voltage data and current data.

Optionally, performing function fitting according to the fitting data source in step 2) to obtain the positive sequence voltage fitting function includes: performing fast Fourier transform FFT on the voltage data as the fitting data source to obtain the dominant frequency, and combining time, voltage The mapping relationship between them is used for function fitting, so as to obtain the positive sequence voltage fitting function.

Optionally, performing function fitting according to the fitting data source in step 2) to obtain the positive sequence current fitting function includes: performing fast Fourier transform FFT on the current data as the fitting data source to obtain the dominant frequency, and combining time, current The mapping relationship between them is used for function fitting, so as to obtain the positive sequence current fitting function.

Optionally, the fitting function parameters include amplitude Amp, frequency f and initial phase φ of the sine wave.

In addition, this embodiment also provides a three-phase zero-voltage ride-through reactive current calculation system based on voltage section extension, which includes interconnected microprocessors and memories, and the microprocessor is programmed or configured to perform the calculation based on Steps of the three-phase zero-voltage ride-through reactive current calculation method for voltage section extension.

In addition, this embodiment also provides a computer-readable storage medium, which is stored in the computer-readable storage medium for being executed by a computer device to implement the three-phase zero-voltage ride-through reactive current calculation method based on voltage section extension computer program.

Compared with the prior art, the present invention mainly has the following advantages: the present invention includes obtaining the test data of the three-phase zero-voltage ride-through test of the energy storage power station; locating the voltage drop section according to the test data, and taking the specified time before the voltage drop section The voltage data of the three-phase balance is used as the fitting data source, and the positive sequence voltage fitting function is obtained by performing function fitting according to the fitting data source; the current sudden increase section is located according to the test data, and the current data of the current sudden increase section is used as the fitting function. According to the fitting data source, the function fitting is performed according to the fitting data source to obtain the positive sequence current fitting function; in the voltage drop section, the fitting positive sequence current in the positive sequence current fitting function is transferred to the positive sequence voltage fitting function Fitting the positive-sequence voltage projection to obtain the positive-sequence reactive current can realize the quantitative calculation of the positive-sequence reactive current in the three-phase zero-voltage ride-through test of the energy storage station, and quantitatively analyze the results of the three-phase zero-voltage ride-through test.

Description of drawings

Fig. 1 is a schematic flow diagram of the basic process of the method of the embodiment of the present invention.

Fig. 2 is a schematic diagram of the fitting waveform of the method of the embodiment of the present invention.

Detailed ways

The following will take the calculation of three-phase zero-voltage ride-through positive-sequence reactive current for an energy storage power station as an example, and further describe the three-phase zero-voltage ride-through reactive current calculation method and system based on voltage section extension of the present invention in detail. . In this embodiment, the scale of the energy storage power station is 20MW/40MWh, the electrochemical energy storage technology is adopted, and the battery is lithium iron phosphate battery.

As shown in Figure 1, the three-phase zero-voltage ride-through reactive current calculation method based on voltage section extension in this embodiment includes:

1) Obtain the test data of the three-phase zero-voltage ride-through test of the energy storage power station;

2) Locate the voltage drop section according to the test data, take the three-phase balanced voltage data of the specified time before the voltage drop section as the fitting data source, and perform function fitting according to the fitting data source to obtain the positive sequence voltage fitting function; The test data locates the current sudden increase section, takes the current data of the current sudden increase section as the fitting data source, and performs function fitting according to the fitting data source to obtain the positive sequence current fitting function;

3) In the voltage drop section, project the fitted positive-sequence current in the positive-sequence current fitting function to the fitting positive-sequence voltage in the positive-sequence voltage fitting function to obtain the positive-sequence reactive current.

In this embodiment, before step 1), there is also a step of performing a three-phase zero-voltage ride-through test on the energy storage power station to obtain test data of the three-phase zero-voltage ride-through test.

The value range of the specified duration in step 2) is 0.5-1.5s.

As a specific implementation manner, the value of the specified duration in this embodiment is 1s.

In this embodiment, the test data of the three-phase zero-voltage ride-through test includes voltage data and current data.

In this embodiment, performing function fitting according to the fitting data source in step 2) to obtain the positive sequence voltage fitting function includes: performing fast Fourier transform (FFT) on the voltage data as the fitting data source to obtain the dominant frequency, time, The mapping relationship between the voltages is used for function fitting, so as to obtain the positive sequence voltage fitting function. In this embodiment, the parameters of the fitting function include the amplitude Amp, the frequency f, and the initial phase φ of the sine wave of the voltage data, and the function expression of the obtained positive sequence voltage fitting function is:

In this embodiment, performing function fitting according to the fitting data source in step 2) to obtain the positive sequence current fitting function includes: performing fast Fourier transform (FFT) on the current data as the fitting data source to obtain the dominant frequency, time, The mapping relationship between the currents is used for function fitting, so as to obtain the positive sequence current fitting function. In this embodiment, the parameters of the fitting function include the amplitude Amp of the sine wave of the current data, the frequency f and the initial phase φ, and the function expression of the obtained positive sequence current fitting function is:

The calculation results in this embodiment are shown in Figure 2. During the low-voltage ride-through process, the main feature of the phenomenon in the zero-voltage ride-through section is a voltage drop, accompanied by a sudden increase in current, that is, a voltage drop section and a current sudden increase. Add section. Among them: a is the comparison between the original waveform of UA phase voltage UA in the zero voltage crossing section and the waveform of UA fitting voltage. The fault occurred at 17.70 seconds. The voltage waveform before the fault is symmetrical and stable. The voltage fitting function is obtained by the voltage before the fault , the voltage range after the virtual drop after extending the voltage fitting function is the normal voltage range. b is the comparison between the original waveform of phase A current IA and the IA fitting current waveform in the zero voltage crossing section. The fault occurred at 17.70 seconds. The current waveform in the fault is symmetrical and stable, and the current fitting function is obtained through the current in the fault. c is the comparison between the fitting waveform of phase A current IA and the fitting waveform of phase A voltage UA in the zero-voltage crossing section. It can be seen that the phase difference between the two is about 90°, and the active power output is suppressed to 0 during three-phase zero-voltage crossing, mainly The fact that the output is reactive power is basically consistent. d is the projection of the positive-sequence fitting current to the positive-sequence fitting voltage in the voltage drop interval to obtain the phase difference Δφ and the positive-sequence reactive current IQ. According to the calculation results, the phase difference Δφ is about 87°, which is consistent with the main output reactive power. The IQ calculated by Δφ is about 147A. This value can be used to quantitatively evaluate the PCS three-phase zero voltage ride-through performance.

In addition, this embodiment also provides a three-phase zero-voltage ride-through reactive current calculation system based on voltage section extension, which includes interconnected microprocessors and memories, and the microprocessor is programmed or configured to perform the aforementioned voltage-based The steps of the three-phase zero-voltage ride-through reactive current calculation method for section extension. In addition, this embodiment also provides a computer-readable storage medium, which is stored in the computer-readable storage medium to be executed by a computer device to implement the aforementioned three-phase zero-voltage ride-through reactive current calculation method based on voltage segment extension Computer program.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein. The present application is described with reference to flowcharts and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram. These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram. These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

The above descriptions are only preferred implementations of the present invention, and the scope of protection of the present invention is not limited to the above examples, and all technical solutions that fall under the idea of the present invention belong to the scope of protection of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (7)

1. The three-phase zero voltage ride through reactive current calculation method based on voltage section extension is characterized by comprising the following steps of:

1) Acquiring test data of a three-phase zero-voltage ride through test of an energy storage power station, wherein the test data of the three-phase zero-voltage ride through test comprises voltage data and current data;

2) Positioning a voltage drop section according to the test data, taking three-phase balanced voltage data with specified duration before the voltage drop section as a fitting data source, and performing function fitting according to the fitting data source to obtain a positive sequence voltage fitting function; positioning a current surge section according to the test data, taking current data of the current surge section as a fitting data source, and performing function fitting according to the fitting data source to obtain a positive sequence current fitting function; the step of performing function fitting according to the fitting data source to obtain a positive sequence voltage fitting function comprises the following steps: performing Fast Fourier Transform (FFT) on voltage data serving as a fitting data source to obtain dominant frequency, and performing function fitting on the mapping relation between time and voltage to obtain a positive sequence voltage fitting function; the step of performing function fitting according to the fitting data source to obtain a positive sequence current fitting function comprises the following steps: carrying out Fast Fourier Transform (FFT) on current data serving as a fitting data source to obtain dominant frequency, and carrying out function fitting on the mapping relation between time and current so as to obtain a positive sequence current fitting function;

3) And in the voltage drop section, projecting the fitted positive sequence current in the positive sequence current fitting function to the fitted positive sequence voltage in the positive sequence voltage fitting function to obtain the positive sequence reactive current.

2. The method for calculating three-phase zero voltage ride through reactive current based on voltage segment extension according to claim 1, further comprising the step of performing a three-phase zero voltage ride through test on the energy storage power station to obtain test data of the three-phase zero voltage ride through test before the step 1).

3. The three-phase zero voltage ride through reactive current calculation method based on voltage section extension according to claim 1, wherein the value range of the specified duration in step 2) is 0.5-1.5 s.

4. The voltage segment continuation-based three-phase zero voltage ride through reactive current calculation method of claim 3, wherein the value of the specified duration in step 2) is 1s.

5. The method for calculating the three-phase zero voltage crossing reactive current based on the voltage section extension according to claim 4, wherein after the fast fourier transform FFT is performed to obtain the dominant frequency of the fitting waveform, further comprising fitting to obtain the amplitude Amp, the frequency f and the initial phase phi of the fitting function.

6. A voltage segment continuation-based three-phase zero voltage ride through reactive current calculation system comprising a microprocessor and a memory connected to each other, characterized in that the microprocessor is programmed or configured to perform the steps of the voltage segment continuation-based three-phase zero voltage ride through reactive current calculation method of any one of claims 1 to 5.

7. A computer-readable storage medium, in which a computer program for execution by a computer device to implement the three-phase zero voltage ride through reactive current calculation method based on voltage segment continuation of any one of claims 1 to 5 is stored.