Adjusting filtering device

Abstract

The utility model discloses an adjusting filtering device, comprising a capacitor; each group comprises an electric reactor and a thyristor switch which are connected in series with each other; after the two groups are connected in parallel, one end is connected in series with the capacitor and the other end is grounded. The thyristor switches are used for grouping the reactors, and an adjustable link is added. Therefore, the adjustable filtering device has the advantages of passive filtering and active filtering. In addition, filtering characteristics are adjusted in a grouping mode, and 1-to-N capacity backup is achieved. And meanwhile, the method has good frequency range expansibility, and the filtering frequency range is greatly expanded as long as the number of groups is properly increased. The more complex harmonic wave environment is, the higher the cost performance is, which is the central idea and the technical characteristic of the utility model.

Description

Technical Field

[0001] The utility model relates to the field of charging pile circuits, and particularly relates to an adjustable filtering device. Background Art

[0002] In an electrical power system, nonlinear elements are the main factors generating harmonics. With the increase in the types of nonlinear elements, the generated harmonic currents become more and more complex. For example, in the railway electrification power system, the electrical circuits all adopt the power supply mode of AC - DC - AC, and a large number of semi-controlled and fully-controlled power electronic devices and PWM technology are adopted, which will inevitably generate a large amount of harmonic currents. Data shows that among the harmonic currents, the 3rd, 5th, 7th, and 9th harmonics are the most, and harmonics below the 50th are all present to varying degrees. Especially in the working states of locomotive braking and climbing slopes, the harmonic currents will be even more complex. In order to reduce the influence of harmonic currents on the power system, certain measures must be taken, such as setting up a filtering circuit. When setting up four filtering circuits for the 3rd, 5th, 7th, and 9th harmonics, three (N - 1) filtering circuits will inevitably be in the "amplification" state. In order to effectively limit the influence generated in the "amplification" state, the utility model designs an adjustable filtering device circuit to reduce the amplified harmonics from the source and ensure the safety of the power system.

[0003] Nonlinear loads are actually a more advanced form of electricity consumption compared to linear loads, but at the same time, they generate harmonic currents, and harmonic currents will cause harm to the power system. Therefore, harmonic currents must be treated. Currently, the main means of treating harmonics is to set up a filtering circuit. The filtering circuit can be divided into two types: passive filtering and active filtering.

[0004] (1) Situation of passive filtering technology: This is a mature traditional filtering technology, which is composed of a capacitor in series with a reactor, and different products such as a double-tuned harmonic filter and a high-pass filter have been developed on the basis of a single-tuned harmonic filter.

[0005] The basic working principle is: It is composed of a capacitor in series with a reactor, and then the parameters of the capacitor and the reactor are adjusted to be close to resonance according to a preset frequency (such as 150HZ for the third harmonic). Then this series circuit presents a low impedance to the third harmonic current and a high impedance to harmonic currents of other frequencies, thereby introducing the third harmonic into the ground and eliminating its influence on the power system.

[0006] The characteristics are: The compensated frequency is single, and one compensation device can only compensate for harmonics of a single frequency. Therefore, multiple compensation devices are often required to meet the requirements. However, the price is cheap, so it is usually used to compensate for large-capacity low-order harmonics, such as the 3rd, 5th, 7th, and 9th harmonics.

[0007] (2) Situation of active filtering technology: This is a new type of filtering technology. With the continuous maturity of the control technology of fully-controlled power electronic device IGBT, this technology has developed rapidly.

[0008] The basic working principle is to detect the harmonics generated by nonlinear loads and then create a harmonic in the opposite direction so that the two harmonics can cancel each other out, thereby eliminating the impact of the harmonics.

[0009] The characteristics are: the compensation frequency is wide, and one compensation device can compensate for all harmonics of different frequencies, but it is expensive, so it is usually used to compensate for higher-order harmonics with smaller capacity.

[0010] (3) In summary, passive filtering and active filtering can be used independently or in combination, depending on the needs of the site environment. Figure 1 shown.

[0011] However, the passive filter device is composed of a capacitor in series with a reactor. Once built, the parameters of each filter circuit are fixed, including the frequency and capacity of the filter. In actual operation, the "amplification" phenomenon of harmonics deteriorates the operating environment and often makes harmonic control fail to achieve the expected effect. The "amplification" phenomenon of harmonics refers to: when a harmonic current flows through a circuit in which a capacitor and a reactor are connected in parallel, the current of the capacitor and the reactor is larger than the harmonic current due to the opposite direction of energy. Taking a group of 3rd, 5th, 7th, and 9th harmonic control circuits as an example, when harmonics below 9th order are generated, they will be amplified and absorbed in the equivalent impedance of the power system and the equivalent impedance of the 3rd, 5th, 7th, and 9th harmonic control circuits. The amplification of harmonics depends on the effective impedance of the power system, which is an unpredictable factor; due to the "amplification" phenomenon, each filter circuit may be overloaded at different times. The parameters of the filter device in the prior art are fixed, unless the capacity of each circuit is greatly increased, or an active filter device is used, which will increase a lot of funds.

[0012] Therefore, it is necessary to develop a new adjustable filtering device to improve the harmonic control effect. Utility Model Content

[0013] In order to overcome the shortcomings of the prior art, the purpose of the utility model is to address the shortcoming that the parameters of the existing passive filter devices are fixed. With a lower cost and an adjustable link, this adjustable filter device acts as a reserve capacity for all filter loops, because only a certain harmonic is seriously amplified at any time, and the adjustable filter device can eliminate this factor in a targeted manner, thereby ensuring the filtering effect.

[0014] The utility model is realized by the following technical scheme: a regulating filter device, comprising a capacitor; at least two groups, each group comprising a reactor and a thyristor switch connected in series; after the two groups are connected in parallel, one end is connected in series with the capacitor, and the other end is grounded.

[0015] Further, it further includes a third group, and the three groups are connected in parallel and then connected in series with the capacitor.

[0016] Compared with the prior art, the beneficial effects that the present utility model can achieve are as follows:

[0017] The adjustable filtering device of the present utility model belongs to the category of passive filtering technology. In order to overcome its lack of flexibility, thyristor switches are used to group the reactors, adding an adjustable link. This enables the adjustable filtering device to have the advantages of both passive filtering and active filtering. In addition, the filtering characteristics are adjusted in a grouped form, achieving a 1-to-N capacity backup. At the same time, it has good frequency range expandability. As long as the number of groups is appropriately increased, the filtering frequency range can be greatly expanded. The more complex the harmonic environment, the higher the cost performance, which is also the central idea and technical feature of the present utility model. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Shown is a wiring schematic diagram of an existing filter;

[0019] Figure 2 Shown is a structural schematic diagram of an existing filtering device;

[0020] Figure 3 Shown is a structural schematic diagram of the first embodiment of the adjustable filtering device of the present utility model;

[0021] Figure 4 Shown is a structural schematic diagram of the second embodiment of the adjustable filtering device of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Next, in combination with the drawings and specific embodiments, the present utility model will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined with each other to form new embodiments.

[0023] As Figure 2 shown, the embodiment of the present utility model discloses an adjustable filtering device, including a capacitor;

[0024] At least two groups, each group includes a reactor and a thyristor switch connected in series with each other; the two groups are connected in parallel and one end is connected in series with the capacitor, and the other end is grounded. Generally, the passive filtering device filters the lower-order harmonics, and the active filtering device filters the higher-order harmonics. The adjustable filtering device is in a standby state. Since the equivalent impedance of the power system changes at any time, it may cause the amplification of a certain harmonic. When abnormal lower-order harmonics are detected, the conduction of the thyristor can be controlled to put the adjustable filtering device into operation.

[0025] This enables the present utility model to achieve the following technical features:

[0026] 1) The adjustable filtering device of the present utility model belongs to the category of passive filtering technology. In order to overcome the lack of flexibility, thyristor switches are used to group the reactors, adding an adjustable link. This enables the adjustable filtering device to have the advantages of both passive filtering and active filtering.

[0027] 2) The filtering characteristics are adjusted in a grouped form, achieving a 1-to-N capacity backup. At the same time, it has good expandability in the frequency range. As long as the number of groups is appropriately increased, the filtering frequency range can be significantly expanded. The more complex the harmonic environment, the higher the cost performance, which is also the central idea and technical feature of the present utility model.

[0028] As Figure 3 shown, further, it further includes a third group. After the three groups are connected in parallel, they are then connected in series with the capacitor. The principle for grouping the adjustable filtering device of the present utility model is that the minimum number of groups is two, and then they are combined as needed. When the number of groups = 2, there are 3 combinations, serving as 3 filtering circuits for reserve capacity; when the number of groups = 3, there are 7 combinations, serving as 7 filtering circuits for reserve capacity; and so on. Specifically, by controlling the thyristor state, the filtering characteristics of the filtering circuit can be adjusted. Generally, the settings are as follows:

[0029] Combination case Filtering frequency (harmonic order) T1 conducts 3rd harmonic T2 conducts 5th harmonic T3 conducts 7th harmonic T1, T2 conduct 9th harmonic T1, T3 conduct 11th harmonic T2, T3 conduct 13th harmonic T1, T2, T3 conduct 15th harmonic

[0030] In summary, the present utility model has achieved the following technical features:

[0031] 1) The adjustable filtering device of the present utility model belongs to the category of passive filtering technology. In order to overcome the lack of flexibility, thyristor switches are used to group the reactors, adding an adjustable link. This enables the adjustable filtering device to have the advantages of both passive filtering and active filtering.

[0032] 2) The filtering characteristics are adjusted in a grouped form, achieving a 1-to-N capacity backup. At the same time, it has good expandability in the frequency range. As long as the number of groups is appropriately increased, the filtering frequency range can be significantly expanded. The more complex the harmonic environment, the higher the cost performance, which is also the central idea and technical feature of the present utility model.

[0033] The above embodiments are only the preferred embodiments of the present utility model and cannot be used to limit the scope of protection of the present utility model. Any non-substantive changes and substitutions made by those skilled in the art based on the present utility model fall within the scope of protection required by the present utility model.

Claims

1. A regulating filter device, characterized in that: include: a capacitor; At least two groups, each group includes a reactor and a thyristor switch connected in series; After the two groups are connected in parallel, one end is connected in series with the capacitor and the other end is grounded.

2. The regulating filter device according to claim 1, characterized in that: It also includes a third group, and the three groups are connected in parallel and then connected in series with the capacitors.

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