CN201584892U - Series connection filter - Google Patents

Abstract

The utility model discloses a series connection filter which is connected between a power supply network and an electric power converter in series; the series connection filter comprises a three-phase reactor and a capacitor. Since the series connection filter is a T-shaped broadband low pass filter formed by the reactor and the capacitor, hardly consume active power and can not produce the influence on electric fundamental power factors and has the suppression effect on the higher harmonic current generated by an electric power converter, therefore the series connection filter can increase the power factor of the whole electricity utilization, reduces the distorted degree of the electric current, has good filtering effect, is particularly suitable for the managing affect of the harmonic pollution of a six-pulse converter; and in addition, the series connection filter belongs to a passive filter, has simple structure and can effectively control the cost.

Description

A series filter

technical field

The utility model belongs to the field of power systems, in particular to a series filter for controlling harmonic pollution of power converters.

Background technique

Power conversion technology includes AC-DC converter, AC-AC converter, AC-DC-AC converter and other technologies, which are widely used in modern industry. The speed regulation performance of variable flow equipment can meet the requirements of various production process machinery and equipment, and the energy saving effect of fan water pump speed regulation and flow adjustment is obvious, which has been generally accepted by the society and widely used; but the energy saving of variable flow equipment also produces a lot of Harmonics, while saving energy, also increase additional losses, waste part of the electric energy, and also bring harmonic pollution to the grid, and at the same time affect the operation of the motor. Harmonic pollution brings additional losses to transmission lines and power loads. For a motor powered by an ordinary frequency converter, the distortion rate of the current flowing into the grid can reach more than 100%. According to the calculation of the loss of the transmission line, without considering the influence of frequency, the loss of the line is proportional to the square of the current, and the loss of the transformer is proportional to the current. Considering the influence of harmonics, the loss of the line is proportional to the square root of the frequency. The higher the frequency, the higher the line loss. The higher the loss.

Traditionally, for the harmonic control of electrorheological systems, there are mainly the following control methods:

(1) Harmonic suppression reactor. Connect the line reactor in series at the incoming line of the converter equipment. This method can suppress the current distortion to 35% to 45%. The reactor will reduce the power factor and affect the output power of the converter equipment. It is generally used as an auxiliary means.

(2) Adopt 12-pulse, 18-pulse or higher pulse variable current. This method can reduce the current distortion to 5% to 10%, but it is costly and depends on the converter itself, so it is suitable for new large-capacity projects.

(3) LC filter. The LC fixed filter is connected in parallel at the incoming line of the converter equipment. This method can not only filter the harmonic current generated by the converter equipment, but also compensate reactive power and improve the power factor. The harmonic filtering rate ranges from 30% to 80%. The disadvantage is that a) the reactive power is compensated while filtering. When the reactive power and harmonic current are out of sync, the filtering effect is poor; b) the filter design The harmonic filtering effect of the tuning frequency accessory is good, but the filtering effect of other harmonics is poor; c) LC filter may cause harmonic amplification and even cause system resonance.

(4) Active filter. This method can reduce the current distortion to less than 5%, but the filtering effect depends on the detection accuracy, and the cost is high. Active filters began to be developed abroad in the early 1970s, and were successfully developed by Westinghouse in 1976. The active filter is very good, but the cost of the active filter is high, a large number of electronic components are used in it, the reliability is poor, the maintenance is large, and it consumes electric energy itself, so it is rarely used in practical applications.

Utility model content

In order to solve the above problems, the utility model provides a series filter with good filtering effect and low cost.

The technical scheme that the utility model adopts for solving its problem is:

A series filter, the series filter includes a three-phase reactor and a capacitor, the three-phase reactor includes a first reactor, a second reactor and a third reactor, the capacitor includes a first capacitor, a second A capacitor and a third capacitor, the incoming end of the first reactor is used to connect to the power grid, the outgoing end is connected to the incoming end of the second reactor, and the outgoing end of the second reactor is used to connect to the power transformer The third reactor, the first capacitor, the second capacitor, and the third capacitor form a tuned filter and are connected between the first reactor and the second reactor.

The beneficial effects of the utility model are: the utility model is a T-type broadband low-pass filter composed of a reactor and a capacitor, hardly consumes active power and does not affect the fundamental wave power factor of electricity, and it can The high-order harmonic current generated by the power converter has a suppression effect, so it can improve the power factor of the overall power consumption, reduce the degree of current distortion, and has a good filtering effect, especially suitable for harmonic pollution of six-pulse converters In addition, because the utility model belongs to the passive filter, its structure is simple, and the cost can be effectively controlled.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is further described:

Fig. 1 is the schematic diagram of the first wiring mode of the present utility model;

Fig. 2 is the schematic diagram of the second wiring mode of the utility model;

Fig. 3 is the schematic diagram of the third wiring mode of the present invention;

Fig. 4 is the use wiring diagram of the utility model.

Detailed ways

Referring to Figures 1 to 4, the series filter of the present invention is connected in series between the power supply grid and the power converter, and is used for the treatment of harmonic pollution of the power converter. The series filter includes three-phase reactors and capacitors , the three-phase reactor includes the first reactor L1, the second reactor L2 and the third reactor L3, the capacitor includes the first capacitor C1, the second capacitor C2 and the third capacitor C3, and the input terminal of the first reactor L1 For connecting with the power supply grid, the outlet terminal is connected with the input terminal of the second reactor L2, the outlet terminal of the second reactor L2 is used for connecting with the power converter, the third reactor L3 and the first capacitor C1 , the second capacitor C2 and the third capacitor C3 form a tuned filter and are connected between the first reactor L1 and the second reactor L2. The series filter has a T-shaped structure as a whole. By selecting appropriate three-phase reactor and capacitor parameters, the filter can neither transmit reactive power nor absorb reactive power during rated operation, and will not affect the power supply grid.

In actual application, the sum of the impedances of the first reactor L1 and the second reactor L2 occupies between 5% and 25% of the electrical load impedance, depending on the actual filtering effect; the third reactor L3 and the first capacitor C1, the second capacitor C2, and the third capacitor C3 form a tuning filter with the characteristic order 5 of the six-pulse power converter. The capacity of the filter is equivalent to the capacity of the first reactor L1 and the second reactor L2, so that the tuning The filter neither outputs reactive power nor transmits reactive power.

Figure 1 is a schematic diagram of the first wiring mode of the present invention, wherein the incoming line end of the third reactor L3 is connected to the outgoing line end of the first reactor L1, and the outgoing line ends of the third reactor are respectively connected to the first capacitor One end of C1, the second capacitor C2, and the third capacitor C3, and the other end of the first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected together, that is, the first capacitor C1, the second capacitor C2, and the third capacitor C3 is connected to each other in star connection.

Fig. 2 is a diagram of the second wiring mode of the present invention, wherein the incoming line end of the third reactor L3 is connected to the outgoing line end of the first reactor L1, and the outgoing line ends of the third reactor are respectively connected with the first capacitors C1, one end of the second capacitor C2, and the third capacitor C3, the first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected to each other in a delta connection.

Figure 3 is a schematic diagram of the third wiring mode of the present invention, wherein the incoming line end of the third reactor L3 is connected to the outgoing line end of the first reactor L1, and the outgoing line ends of the third reactor are respectively connected to the first capacitor C1, the second capacitor C2, one end of the third capacitor C3, and the three phases of the third reactor L3 are respectively connected to the capacitors to form a three-phase branch connected to each other in a delta connection.

There are differences in the above several wiring methods, but they all have a good control effect on the high-order harmonics generated by the power converter. Experiments have shown that the current distortion in the circuit after the series filter of the utility model can be reduced to 5 %~10%.

In addition, the first reactor L1 and the second reactor L2 in the utility model can be combined to form a double-winding reactor, or the first reactor L1, the second reactor L2 and the third reactor L3 can be combined in A multi-winding reactor is made together, so that the overall manufacturing cost of the reactor can be reduced, and the volume of the series filter can be greatly reduced, thereby achieving a better use effect.

Of course, the present invention is not limited to the above-mentioned embodiments. Those skilled in the art can also make various equivalent modifications or replacements without violating the spirit of the present utility model. These equivalent modifications or replacements are all included in this application. within the scope of the claims.

Claims (4)

1. A series filter, characterized in that: the series filter comprises a three-phase reactor and a capacitor, and the three-phase reactor comprises a first reactor (L1), a second reactor (L2) and a third reactance A reactor (L3), the capacitor includes a first capacitor (C1), a second capacitor (C2) and a third capacitor (C3), and the incoming terminal of the first reactor (L1) is used to connect to the power grid, The outlet terminal is connected to the input terminal of the second reactor (L2), the outlet terminal of the second reactor (L2) is used to connect with the power converter, the third reactor (L3) and the first capacitor (C1 ), the second capacitor (C2), and the third capacitor (C3) form a tuned filter and are connected between the first reactor (L1) and the second reactor (L2). 2. A series filter according to claim 1, characterized in that the incoming line end of the third reactor (L3) is connected to the outgoing line end of the first reactor (L1), and the outgoing line end of the third reactor One end of the first capacitor (C1), the second capacitor (C2), and the third capacitor (C3) are respectively connected to one end of the first capacitor (C1), the second capacitor (C2), and the other end of the third capacitor (C3). and connected together. 3. A series filter according to claim 1, characterized in that the incoming line end of the third reactor (L3) is connected to the outgoing line end of the first reactor (L1), and the outgoing line end of the third reactor One end of the first capacitor (C1), the second capacitor (C2), and the third capacitor (C3) are respectively connected to each other, and the first capacitor (C1), the second capacitor (C2), and the third capacitor (C3) are connected in a delta connection. law interconnected. 4. A series filter according to claim 1, characterized in that the incoming line end of the third reactor (L3) is connected to the outgoing line end of the first reactor (L1), and the outgoing line end of the third reactor One end of the first capacitor (C1), the second capacitor (C2), and the third capacitor (C3) are respectively connected to each end, and the three phases of the third reactor (L3) are respectively connected to the capacitor to form a three-phase branch circuit They are connected to each other by delta connection.

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