An active filter device

Abstract

This utility model relates to the field of active power filter technology and provides an active power filter device, comprising: a current transformer connected between the mains power supply and the load for acquiring three-phase current signals; an active power filter whose input terminal is connected between the mains power supply and the current transformer, and whose current transformer interface is connected to the current transformer; the active power filter includes a control board and a display module; the control board is connected to the input terminal and is used to acquire the three-phase voltage signal of the power grid through the input terminal, acquire the three-phase current signal through the current transformer interface, and generate a connection anomaly detection signal for the current transformer based on the three-phase voltage signal and the three-phase current signal, and send a flag bit signal corresponding to the connection anomaly detection signal to the display module. This solves the problem of quickly and accurately providing a connection anomaly detection signal for the external current transformer of the active power filter.

Description

Technical Field

[0001] This utility model belongs to the field of active filter technology, and in particular relates to an active filter device. Background Technology

[0002] An active power filter (APF) is a new type of power electronic device used for dynamically suppressing harmonics and compensating for reactive power. It can compensate for harmonics and reactive power that vary in magnitude and frequency. However, during the installation of an APF, issues such as reversed CT (current transformer) polarity and three-phase misalignment may occur. For example, in traditional processes, the installation direction and phase sequence of the CTs need to be manually checked. This operation is complex, and manual inspection alone makes it easy to encounter reversed CT connections and incorrect phase sequences. This leads to errors in the data collected by the filter control device, affecting the normal control of the filter device, causing severe grid distortion, and generating higher voltage spikes in the grid. In severe cases, it may even damage the load equipment, affecting the safe and reliable operation of the equipment, and these issues are difficult to detect. When equipment failures or incorrect compensation occur, troubleshooting is time-consuming, labor-intensive, and inefficient. Utility Model Content

[0003] This invention provides an active filter device, which aims to solve the problem of quickly and accurately providing a connection anomaly detection signal for an external current transformer connected to the active filter.

[0004] This invention is implemented as follows: an active filter device, comprising:

[0005] A current transformer is connected between the mains power supply and the load to collect three-phase current signals.

[0006] An active filter, the input terminal of which is connected between the mains power and the current transformer, and the current transformer interface of which is connected to the current transformer;

[0007] The active filter includes a control board and a display module; the control board is connected to the input terminal and is used to acquire the three-phase voltage signal of the power grid through the input terminal, acquire the three-phase current signal through the current transformer interface, generate a connection abnormality detection signal of the current transformer based on the three-phase voltage signal and the three-phase current signal, and send the flag bit signal corresponding to the connection abnormality detection signal to the display module.

[0008] Furthermore, the control panel includes:

[0009] An operational amplifier module is connected to the input terminal, and the operational amplifier module is used to acquire the three-phase voltage signal of the power grid;

[0010] The control module, connected to the operational amplifier module and the current transformer, is used to generate a connection abnormality detection signal for the current transformer based on the three-phase voltage signal and the three-phase current signal.

[0011] Furthermore, the connection anomaly detection signal includes at least one of a first signal indicating reversed polarity of the current transformer and a second signal indicating incorrect phase connection of the current transformer.

[0012] Furthermore, the connection anomaly detection signal includes a first signal indicating that the polarity of the current transformer is reversed. The control board generates the first signal when the three-phase active power determined based on the three-phase voltage signal and the three-phase current signal is negative.

[0013] Furthermore, the connection anomaly detection signal includes a second signal indicating a phase error in the current transformer connection, which the control board generates when a power factor anomaly is determined based on the three-phase voltage signal and the three-phase current signal.

[0014] Furthermore, the flag bit signal corresponds one-to-one with the connection anomaly detection signal, and the flag bit signal is used to identify the connection anomaly situation or the connection normal situation corresponding to the connection anomaly detection signal.

[0015] Furthermore, once the active filter device is installed, the load is at least partially put into use.

[0016] Furthermore, the active filter device also includes an auxiliary power supply board connected to the control board for supplying power to the control board.

[0017] Furthermore, the current transformer is connected to the mains side or the load side.

[0018] This utility model's active power filter device generates a connection anomaly detection signal for the current transformer by combining the three-phase current signal collected by an external current transformer and the three-phase voltage signal of the power grid collected by the control board of the active power filter. The signal is then sent to the display module via a flag bit corresponding to the connection anomaly detection signal to provide a connection anomaly detection result prompt. This avoids the low accuracy and heavy workload of manual identification of connection status during the installation of the active power filter device. The detection can be performed simply by powering on the active power filter device before it is put into use, with high detection efficiency and accuracy, and no impact on the safety of the line system or the load. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the active filter device provided by this utility model;

[0020] Figure 2 This is a schematic diagram of the structure of the active filter provided by this utility model;

[0021] Figure 3 This is a schematic diagram of the control module provided by this utility model;

[0022] Figure 4 This is a schematic diagram of the signal acquisition principle provided by this utility model. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0024] In related technologies, active power filter devices often fail to perform current transformer (CT) testing during installation and use. Instead, the traditional method of manually checking the CT connection is used. This method is highly susceptible to reversed CT polarity and incorrect phase sequence. If reversed CT polarity or incorrect phase sequence occurs and the active power filter is activated, the compensation current will generate higher voltage spikes in the power grid, potentially damaging the load equipment. Other detection methods calculate the phase of voltage and current using FFT (Fast Fourier Transform), obtain the relative phase of voltage and current, and compare it with a set threshold to determine the CT direction. This method is computationally intensive and complex to implement, fails to consider the diversity of actual loads in the field, and has poor practicality, only applicable to specific situations.

[0025] Therefore, traditional installation methods rely on manual orientation identification, requiring extensive pre-power-on checks, highly specialized personnel, a heavy workload, and demanding testing equipment, making the process complex. Troubleshooting necessitates specialized instruments for measurement and data comparison, requiring experienced personnel with high proficiency in the equipment, making the process complex and potentially dangerous. While FFT (Fault-Fold Analyzer Testing) offers rapid detection, its complexity and limited practicality limit its application to specific sites. Failure to accurately detect reversed connections before power-on can easily lead to worsened power grid distortion and potential damage to load equipment.

[0026] This utility model's active power filter device generates a connection anomaly detection signal for the current transformer by combining the three-phase current signal collected by an external current transformer and the three-phase voltage signal of the power grid collected by the control board of the active power filter. The signal is then sent to the display module via a flag bit corresponding to the connection anomaly detection signal to provide a connection anomaly detection result prompt. This avoids the low accuracy and heavy workload of manual identification of connection status during the installation of the active power filter device. The detection can be performed simply by powering on the active power filter device before it is put into use, with high detection efficiency and accuracy, and no impact on the safety of the line system or the load.

[0027] Example 1

[0028] This embodiment provides an active filter device, such as... Figure 1 As shown, it includes:

[0029] The current transformer 101 is connected between the mains power 102 and the load 103 and is used to collect three-phase current signals; specifically, the current transformer 101 is a three-phase current transformer.

[0030] An active filter 104 has its input terminal connected between the mains power 102 and the current transformer 101, and its current transformer interface is connected to the current transformer 101.

[0031] The active power filter 104 includes a control board 1041 and a display module 1042. The control board 1041 is connected to the input terminals and is used to acquire the three-phase voltage signal of the power grid through the input terminals, acquire the three-phase current signal through the current transformer interface, and generate a connection abnormality detection signal for the current transformer 101 based on the three-phase voltage signal and the three-phase current signal. The control board 1041 then sends the flag bit signal corresponding to the connection abnormality detection signal to the display module 1042. For example, the display module 1042 may be a liquid crystal display module.

[0032] In one example, the structure of an active filter is as follows: Figure 2 As shown, in addition to the control board, it also includes a current transformer interface (CT interface), input terminals, an auxiliary power supply board, a driver board, and capacitor busbars. The input terminals are used to introduce the three-phase voltage signal from the power grid into the control board 1041. The current transformer interface (CT interface) is connected to the secondary sampling lines of the current transformer 101, and is used to introduce the three-phase current signal collected by the current transformer 101 into an active filter to combine with the three-phase voltage signal from the power grid to generate a connection anomaly detection signal. The auxiliary power supply board is used to supply power to the control board 1041, and the driver board is used to drive the IGBT devices.

[0033] In this embodiment, the connection anomaly detection signal of the current transformer can be generated by the three-phase current signal collected by the external current transformer and the three-phase voltage signal of the power grid collected by the control board of the active filter. The connection anomaly detection signal is then sent to the display module through the flag bit signal corresponding to the connection anomaly detection signal to provide a connection anomaly detection result prompt. This avoids the low accuracy and huge workload of manual identification of connection status during the installation of the active filter device. The detection can be achieved by powering on the active filter device before it is put into use. The detection efficiency and accuracy are high, and there is no impact on the safety of the line system and the load. This solves the problem of quickly and accurately providing connection anomaly detection signals of the external current transformer of the active filter.

[0034] Example 2

[0035] Based on Embodiment 1, in the active filter device of this embodiment, the control board 1041 includes:

[0036] An operational amplifier module, connected to the input terminals, is used to acquire three-phase voltage signals from the power grid; and

[0037] The control module, connected to the operational amplifier module and the current transformer, is used to generate a connection abnormality detection signal for the current transformer based on the three-phase voltage signal and the three-phase current signal.

[0038] In this embodiment, the control module can be a control chip. By acquiring the three-phase voltage signal of the power grid through the operational amplifier module, high-precision and stable voltage sampling can be achieved.

[0039] Example 3

[0040] Based on the foregoing embodiments, in the active filter device of this embodiment, the connection abnormality detection signal includes at least one of a first signal of reverse polarity connection of current transformer and a second signal of phase connection error of current transformer.

[0041] In this embodiment, the active filter device can generate a first signal indicating reversed polarity of the current transformer and / or a second signal indicating incorrect phase connection of the current transformer based on the three-phase voltage signal and the three-phase current signal. This enables the detection of abnormal connection of the external current transformer. By transmitting the first signal and / or the second signal to the display module, abnormal information can be provided in a timely manner. Before the active filter device is powered on and put into use, the external current transformer should be connected correctly to avoid potential safety hazards. This ensures the safe and stable normal operation of the active filter device, improves work efficiency, and reduces maintenance costs.

[0042] In some cases, the connection anomaly detection signal includes a first signal indicating that the current transformer polarity is reversed, which the control board generates when the three-phase active power, determined based on the three-phase voltage and current signals, is negative.

[0043] In some cases, the load includes a resistive load, and the connection anomaly detection signal includes a second signal indicating a phase error in the current transformer connection. The control board generates this second signal when the power factor is abnormal, determined based on the three-phase voltage and current signals. Specifically, in resistive loads, a second signal indicating a phase misconnection of the three-phase current transformers is generated based on the power factor (PF) value of each phase.

[0044] In practical applications, such as Figure 4 As shown, the three-phase current signal of the load is acquired in real time through an external current transformer to obtain the instantaneous value of the three-phase load current. The three-phase voltage signal of the power grid is acquired in real time through an operational amplifier module to obtain the instantaneous value of the three-phase power grid voltage. The acquired three-phase voltage and current signals are integrated in an interrupt function by multiplying the instantaneous values ​​of the power grid voltage and current for a single cycle (20ms) to calculate the three-phase active power of the current transformer for that single cycle. If the three-phase active power is negative (with a certain allowable error within a single cycle), the control board generates a first signal indicating reversed polarity of the current transformer. Using the same method, but replacing the voltage with a voltage lagging by 90 degrees, and again using a single cycle as the unit, the three-phase reactive power can be calculated, and thus the PF (power factor) value at the three-phase current transformer can be calculated.

[0045] In one example, such as Figure 3 As shown, the control module includes a voltage and current sampling unit, a signal processing unit, and a control unit. The voltage and current sampling unit is used to acquire the three-phase voltage signal of the power grid collected by the operational amplifier module and the three-phase current signal of the load collected in real time by the external current transformer. The signal processing unit is connected to the voltage and current sampling unit and is used to determine the three-phase active power based on the three-phase voltage signal and the three-phase current signal, and / or determine the power factor based on the three-phase voltage signal and the three-phase current signal. The control unit is used to generate corresponding signals based on logical judgments, including generating a first signal when the three-phase active power is negative, generating a second signal when the power factor is abnormal, and transmitting the first signal and / or the second signal to the display module for display, so as to facilitate viewing.

[0046] Example 4

[0047] Based on the aforementioned embodiments, in the active filter device of this embodiment, the flag bit signal corresponds one-to-one with the connection anomaly detection signal, and the flag bit signal is used to identify the connection anomaly situation or the connection normal situation corresponding to the connection anomaly detection signal.

[0048] In one example, flag 01 indicates that the polarity of the current transformer is reversed, flag 02 indicates that the phase connection of the current transformer is incorrect, and flag 00 indicates that the current transformer is connected normally, that is, there is no situation where the polarity of the current transformer is reversed or the phase connection is incorrect.

[0049] In this embodiment, by generating a flag bit signal that corresponds one-to-one with the connection anomaly detection signal and transmitting the flag bit signal to the display module, maintenance personnel can easily view and obtain connection anomaly information in a timely manner.

[0050] Example 5

[0051] Based on the aforementioned embodiments, this embodiment ensures that at least part of the load is put into use after the active filter device is installed.

[0052] Once the active power filter is installed, simply powering it on (without actually turning it on) and connecting a certain amount of active load is sufficient for detection. This method offers high efficiency and accuracy, has no impact on line system safety or load, and is applicable to a wide range of scenarios. It boasts a fast detection rate, ideally completing detection in 20ms, and high accuracy unaffected by load. As long as there is a certain amount of active power at the current transformer, it can be accurately detected. This solves the problem of quickly and accurately providing connection anomaly detection signals for external current transformers connected to the active power filter.

[0053] In some cases, current transformer polarity and phase reversal detection enable keys can be set to enable the detection function when detection is required, making it convenient and quick to implement current transformer connection detection according to needs.

[0054] In some specific implementations, the current transformer is connected to the mains side or the load side. The above-described scheme applies to the current transformer regardless of whether it is connected to the mains side or the load side, so as to generate and display the connection abnormality detection signal.

[0055] Compared with existing devices capable of detecting connection anomalies in external current transformers, the solution provided by this invention can accurately generate connection anomaly detection signals even in the presence of reactive power and harmonics, offering high accuracy and practicality. The connection anomaly detection signal for the current transformer can be generated by combining the three-phase current signal collected by the external current transformer and the three-phase voltage signal of the power grid collected by the control board of the active power filter. This signal is then sent to the display module via a corresponding flag bit to provide a connection anomaly detection result. This avoids the low accuracy and heavy workload of manual identification of connection status during the installation of the active power filter. Detection can be performed simply by powering on the active power filter before it is put into use, resulting in high detection efficiency and accuracy without affecting the safety of the line system or the load. This solves the problem of quickly and accurately providing connection anomaly detection signals for external current transformers in active power filters.

[0056] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An active filter device, characterized in that, include: A current transformer is connected between the mains power supply and the load to collect three-phase current signals. An active filter, the input terminal of which is connected between the mains power and the current transformer, and the current transformer interface of which is connected to the current transformer; The active filter includes a control board and a display module; the control board is connected to the input terminal and is used to acquire the three-phase voltage signal of the power grid through the input terminal, acquire the three-phase current signal through the current transformer interface, generate a connection abnormality detection signal of the current transformer based on the three-phase voltage signal and the three-phase current signal, and send the flag bit signal corresponding to the connection abnormality detection signal to the display module.

2. The active filter device as described in claim 1, characterized in that, The control panel includes: An operational amplifier module is connected to the input terminal, and the operational amplifier module is used to acquire the three-phase voltage signal of the power grid; The control module, connected to the operational amplifier module and the current transformer, is used to generate a connection abnormality detection signal for the current transformer based on the three-phase voltage signal and the three-phase current signal.

3. The active filter device as described in claim 1, characterized in that, The connection anomaly detection signal includes at least one of a first signal indicating reversed polarity of the current transformer and a second signal indicating incorrect phase connection of the current transformer.

4. The active filter device as described in claim 3, characterized in that, The connection anomaly detection signal includes a first signal indicating that the polarity of the current transformer is reversed. The control board generates the first signal when the three-phase active power determined based on the three-phase voltage signal and the three-phase current signal is negative.

5. The active filter device as described in claim 3, characterized in that, The load includes resistive loads.

6. The active filter device as described in claim 5, characterized in that, The connection anomaly detection signal includes a second signal indicating a phase error in the current transformer connection. The control board generates the second signal when the power factor is abnormal, as determined based on the three-phase voltage signal and the three-phase current signal.

7. The active filter device as described in claim 1, characterized in that, The flag bit signal corresponds one-to-one with the connection anomaly detection signal, and the flag bit signal is used to identify the connection anomaly situation or the connection normal situation corresponding to the connection anomaly detection signal.

8. The active filter device as described in claim 1, characterized in that, The load is at least partially put into use once the active filter device is installed.

9. The active filter device as described in claim 1, characterized in that, It also includes an auxiliary power board, which is connected to the control board and is used to supply power to the control board.

10. The active filter device as claimed in claim 1, characterized in that, The current transformer is connected to the mains side or the load side.

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