A power filter commissioning protection device

Abstract

The application provides a power filter operation protection device, and relates to the technical field of power equipment monitoring.The power filter operation protection device comprises a signal acquisition module, an isolation transformer, an analog quantity acquisition module, an A / D conversion module and a CPU.The output end of the signal acquisition module is connected with the input end of the isolation transformer;the output end of the isolation transformer is connected with the input end of the analog quantity acquisition module;the output end of the analog quantity acquisition module is connected with the input end of the A / D conversion module;and the A / D conversion module is connected with the CPU.The power filter operation protection device solves the problem that improper operation may cause harmonic amplification, which threatens the safety of the power grid, causes the filter to be unable to be normally operated, and even damages the filter, and the protection device determines the filter operation scheme by detecting the harmonic characteristics of the power grid, so as to guarantee the safe operation of the filter.

Description

Technical Field

[0001] This invention relates to the field of power equipment monitoring technology, and in particular to a power filter commissioning protection device. Background Technology

[0002] New energy sources such as wind power and photovoltaic power generation need to be connected to the power grid via power electronic devices, and electric vehicle charging facilities also require power electronic devices to achieve power conversion. With the rapid development of new energy and electric vehicles, more and more power electronic devices are being connected to the power grid. These devices generate a large number of harmonics during operation. These harmonics, once injected into the grid, degrade power quality, affect the normal operation of power users, damage electrical equipment, cause production accidents, and in extreme cases, cause harmonic resonance, threatening the safe operation of the power grid. Therefore, it is necessary to control the harmonics generated by power electronic devices to reduce their impact on power quality and ensure the safe operation of the power grid and power users. Power filters are a widely used and effective means of controlling harmonics. Power grid harmonics are mainly of the 3rd, 5th, and 7th orders, and generally, 3rd, 5th, and 7th order filters need to be installed on the grid side or the user side. Different filters have different harmonic impedance characteristics. Improper commissioning during operation may cause harmonic amplification, threatening the safety of the power grid, preventing the filter from operating normally, or even damaging the filter.

[0003] A filter is essentially a series circuit of an inductor (L) and a capacitor (C), and its operation alters the harmonic impedance characteristics of the power grid. Currently, filter commissioning is generally based on experience and follows a fixed commissioning sequence. This method does not consider the harmonic characteristics of the power grid, which can easily lead to harmonic amplification and affect the normal operation of the filter. Therefore, a protection device is needed to determine the filter commissioning scheme by detecting the harmonic characteristics of the power grid to ensure the safe operation of the filter. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a power filter commissioning protection device to solve the problems of harmonic amplification and failure to commission normally during the commissioning process of power filters in the prior art.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a power filter commissioning protection device, comprising a signal acquisition module, an isolation transformer, an analog quantity acquisition module, an A / D conversion module, and a CPU;

[0006] The output terminal of the signal acquisition module is connected to the input terminal of the isolation transformer, the output terminal of the isolation transformer is connected to the input terminal of the analog quantity acquisition module, and the output terminal of the analog quantity acquisition module is connected to the input terminal of the A / D conversion module.

[0007] The A / D conversion module is connected to the CPU;

[0008] The signal acquisition module includes a voltage transformer and a current transformer;

[0009] The signal acquisition module acquires voltage signals through a voltage transformer and current signals through a current transformer.

[0010] Furthermore, the CPU also includes a power grid harmonic characteristic analysis module for performing harmonic characteristic analysis on current and voltage signals.

[0011] Furthermore, the CPU is also connected to a device display for operators to perform filter commissioning operations.

[0012] Furthermore, the commissioning method and steps for the power filter commissioning protection device include:

[0013] Step 1: The signal acquisition module acquires the grid voltage and current signals, which are then converted into digital signals by the isolation transformer, analog acquisition module, and A / D conversion module.

[0014] Step 2: Based on the obtained digital signal, the CPU performs power grid harmonic characteristic analysis to obtain the power grid harmonic voltage and harmonic current;

[0015] Step 3: Calculate the harmonic impedance of the power grid based on the obtained harmonic voltage and harmonic current, and obtain the harmonic amplification criterion;

[0016] Step 4: Calculate the filter impedance using the filter parameters and combination methods to determine the safe operating region of the filter;

[0017] Step 5: Based on the obtained harmonic amplification criteria and the safe operating domain of the filter, screen feasible operation schemes for the filter, calculate the safety factor of the feasible operation schemes, and thus determine the filter operation scheme.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The power filter commissioning protection device of this invention solves the problem that improper commissioning during operation may cause harmonic amplification, which threatens the safety of the power grid, prevents the filter from operating normally, or even damages the filter. The protection device determines the filter commissioning scheme by detecting the harmonic characteristics of the power grid, so as to ensure the safe commissioning of the filter. Attached Figure Description

[0020] Figure 1 Hardware structure diagram of the power filter commissioning protection device provided by the present invention;

[0021] Figure 2 A schematic diagram of the harmonic amplification risk area of ​​the power filter during commissioning provided by the present invention;

[0022] Figure 3 A flowchart illustrating the power filter commissioning scheme provided by this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1-3 As shown, the present invention proposes a power filter commissioning protection device, including a signal acquisition module, an isolation transformer, an analog quantity acquisition module, an A / D conversion module, and a CPU;

[0025] The output terminal of the signal acquisition module is connected to the input terminal of the isolation transformer, the output terminal of the isolation transformer is connected to the input terminal of the analog quantity acquisition module, and the output terminal of the analog quantity acquisition module is connected to the input terminal of the A / D conversion module.

[0026] The A / D conversion module is connected to the CPU;

[0027] The signal acquisition module includes a voltage transformer and a current transformer;

[0028] The signal acquisition module acquires voltage signals through a voltage transformer and current signals through a current transformer.

[0029] Furthermore, the CPU also includes a power grid harmonic characteristic analysis module for performing harmonic characteristic analysis on current and voltage signals.

[0030] Furthermore, a device display is connected to the CPU for operators to perform filter commissioning operations. Furthermore, the commissioning method for the power filter commissioning protection device includes the following steps:

[0031] Step 1: The signal acquisition module acquires the grid voltage and current signals, which are then converted into digital signals by the isolation transformer, analog acquisition module, and A / D conversion module.

[0032] Step 2: Based on the obtained digital signal, the CPU performs power grid harmonic characteristic analysis to obtain the power grid harmonic voltage and harmonic current;

[0033] Step 3: Calculate the harmonic impedance of the power grid based on the obtained harmonic voltage and harmonic current, and obtain the harmonic amplification criterion;

[0034] Step 4: Calculate the filter impedance using the filter parameters and combination methods to determine the safe operating region of the filter;

[0035] Step 5: Based on the obtained harmonic amplification criteria and the safe operating domain of the filter, screen feasible operation schemes for the filter, calculate the safety factor of the feasible operation schemes, and thus determine the filter operation scheme.

[0036] In this embodiment, the device collects grid voltage and current signals, and the CPU performs grid harmonic analysis. Based on the grid harmonic impedance and the filter harmonic impedance, a harmonic amplification criterion is derived. Based on the harmonic amplification criterion and the filter commissioning combination method, a filter commissioning safety domain is given. By comparing the safety factors of different commissioning schemes, the filter commissioning scheme is determined. Finally, the CPU outputs the commissioning scheme to the device display.

[0037] The working principle of this embodiment is as follows: the voltage signal of the signal acquisition module is taken from the voltage transformer of the low-voltage side bus of the self-transformer, and the current signal is taken from the current transformer of the low-voltage side of the self-transformer. The voltage and current signals are converted into weak electrical signals through the isolation transformer and the analog quantity acquisition module (AN), and then converted into digital signals through the A / D conversion module. Finally, they are input to the CPU for the power grid harmonic characteristic analysis module.

[0038] The power grid harmonic characteristic analysis module is implemented through software. First, the power grid voltage and current signals are analyzed for harmonics using Fast Fourier Decomposition to obtain the power grid harmonic voltage and harmonic current.

[0039] Let the voltage of the h-th harmonic of the power grid before the filter is put into operation be... The h-th harmonic current is Then the impedance of the h-th harmonic of the power grid is

[0040]

[0041] Wherein, harmonic impedance angle θ sh Used to determine the properties of power grid harmonic impedance, when θ sh When θ > 0, the harmonic impedance of the power grid is inductive. sh When the value is less than 0, the harmonic impedance of the power grid is capacitive.

[0042] Let the harmonic current injected into the power grid by the harmonic source be... After the filter is put into operation, the harmonic impedance of the filter is when Z Lh Then, the harmonic current injected into the power grid after the filter is put into operation is

[0043]

[0044] If the harmonic impedance of the power grid and the harmonic impedance of the filter have opposite properties, there is a risk of harmonic amplification. Theoretically, the range of power grid harmonic impedances that can cause harmonic amplification is...

[0045] 0 < Z sh <2Z Lh

[0046] Considering that both the grid harmonic impedance and the filter harmonic impedance have resistive components, from an engineering practice perspective, the criterion for harmonic amplification after the filter is put into operation is:

[0047] 0.2Z Lh <Z sh <1.8Z Lh

[0048] In practical engineering, multiple filters are typically configured, resulting in various filter operation combinations. The harmonic impedance of each combination is calculated, and based on the aforementioned harmonic amplification criterion, the harmonic risk region for each combination can be determined. The union of these risk regions is taken; the area outside this union represents the safe operating region of the filter. Operation schemes falling within this safe region are feasible, will not cause harmonic amplification, and can ensure the safe operation of the filter.

[0049] In actual engineering projects, the commissioning plan can be ultimately determined by calculating the safety factor, and the commissioning plan with the highest safety factor is selected as the final commissioning plan. The safety factor calculation method is as follows:

[0050]

[0051] Once the final commissioning plan is determined, it is output by the CPU to the device display for the operator to perform the filter commissioning operation.

[0052] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A power filter commissioning protection device, characterized in that, Includes signal acquisition module, isolation transformer, analog signal acquisition module, A / D conversion module, and CPU; The output terminal of the signal acquisition module is connected to the input terminal of the isolation transformer, the output terminal of the isolation transformer is connected to the input terminal of the analog quantity acquisition module, and the output terminal of the analog quantity acquisition module is connected to the input terminal of the A / D conversion module. The A / D conversion module is connected to the CPU; The signal acquisition module includes a voltage transformer and a current transformer; The signal acquisition module acquires voltage signals through a voltage transformer and current signals through a current transformer; Specifically, the signal acquisition module acquires the grid voltage and current signals, which are then converted into digital signals by the isolation transformer, analog acquisition module, and A / D conversion module; the CPU performs grid harmonic characteristic analysis to obtain grid harmonic voltage and harmonic current; the grid harmonic impedance is then calculated to obtain harmonic amplification criteria; and the filter impedance is calculated using filter parameters and combination methods to determine the safe operating range of the filter. By comparing the safety factors of different commissioning schemes, the filter commissioning scheme is determined, and the CPU outputs the commissioning scheme to the device display. Wherein, the h-th harmonic voltage of the power grid before the filter is put into operation is... The h-th harmonic current is Then the impedance of the h-th harmonic of the power grid is, In the formula, the harmonic impedance angle θ sh Used to determine the properties of power grid harmonic impedance, when θ sh When θ > 0, the harmonic impedance of the power grid is inductive; when θ < 0, the harmonic impedance of sh When < 0, the power grid harmonic impedance is capacitive; Let the harmonic current injected into the power grid by the harmonic source be... After the filter is put into operation, the harmonic impedance of the filter is when Z Lh Then, the harmonic current injected into the power grid after the filter is put into operation is, The range of harmonic impedance of the power grid is: 0 < Z sh <2Z Lh ; The harmonic amplification criterion after the filter is put into operation is: 0.2Z Lh <Z sh <1.8Z Lh ; Safety factor is 2. The power filter commissioning protection device according to claim 1, characterized in that, The CPU also includes a power grid harmonic characteristic analysis module, used to perform harmonic characteristic analysis on current and voltage signals.

3. The power filter commissioning protection device according to claim 1, characterized in that, The CPU is also connected to a device display, which is used by operators to perform filter commissioning operations.

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