ES2233193A1 - Active filter for use in nonlinear load network, has processor comprising block distortion analyzer, and logic block receiving output signal of current sensors for ordering features of inverter bridge - Google Patents

Abstract

The filter has current sensors provided with a bridge inverter, where output current of the sensors is proportional to input current to a nonlinear load. A processor is programmed with a preset intensity curve value, and comprises a block distortion analyzer. A logic block receives an output signal of the current sensors for ordering features of an inverter bridge.

Description

Active filter to use in a network with a load nonlinear

When a load is established on a network, linear, there is an alteration of the variables in the network Electrical quantifiable by its harmonics.

The elimination of said alteration has been done so far by connecting to the filter network passive for each harmonic one wanted to reduce, which is a Important cost in the installation.

The applicant has achieved better results and at a lower cost by replacing the set of passive filters with the active filter object of the invention.

The user can decide a combination between already known based on passive filters with the active filter of the invention, for example, using a passive filter for the 5th harmonic.

In particular, the active filter of the invention is characterized because it consists of

a) first intensity sensors, one per network phase, whose output is proportional to the input intensity to the non-linear load;

b) an inverter bridge whose outputs feed back to the network, with the distortion signal, being arranged in said Departures

c) a few second intensity sensors, similar to the first intensity sensors;

d) a processor programmed with a curve of preset intensity, consisting of

d_ {1}) an analyzer block that receives the output signals of the first intensity sensors and that analyzes its harmonic distortion based on the rapid transformation of Fourier, obtaining the real distortion;

d_ {2}) a logic block that receives the signal output of the second intensity sensors and ordering the trigger characteristics of the inverter bridge while the conjunction of the distortion signal with the actual distortion no recompose, with a preset differential, the intensity curve preset

It is also characterized because the present inverter is equipped with power poles.

It is also characterized because at the exit of the First intensity sensors a low pass filter is arranged.

It is also characterized because it is available in the network before the first sensors a high frequency filter.

It is also characterized because the outputs of the inverter bridge are connected to the network by means of a transformer of coupling and isolation.

To better understand the purpose of this invention, a preferred form of practical realization, susceptible to accessory changes that do not distort its foundation.

Figure 1 is a block diagram of a practical embodiment of the active filter object of the invention a rectifier bridge (1) being used as a non-linear load.

Figure 2 is a coordinate representation intensity / time of the intensity absorbed by the bridge rectifier (1) read in point A of figure 1.

Figure 3 is a coordinate representation intensity / time of the distortion of the current absorbed by the bridge rectifier (1) read in point C of figure 1.

Figure 4 is a coordinate representation intensity / time of the intensity absorbed by the set read at point B of figure 1.

An example of practical, non-limiting embodiment of the present invention. I dont know discarded at all other embodiments in which introduce accessory changes that do not distort its foundation; by On the contrary, the present invention also covers all its variants.

The prototype test of Figure 1 consisted of in the connection of the active filter object of the invention to a rectifier (1) in three-phase thyristor bridge, which constitutes a very extended example of non-linear load, since it absorbs harmonics order characteristics 6 n ± 1 with strong distortion total.

For the said test, the assembly of the Figure 1, but eliminating the reactive compensation unit (2) and the passive 5th harmonic filter (3) and the result appears in the Figures 2, 3 and 4.

In practice, a passive filter is used formed by a reactive energy compensation unit (2), by example, a capacitor bank and a passive filter (3) tuned for the 5th harmonic frequency filtering fundamental of the network used (all of which is already known), in combination with an active filter (which is the object of the invention) that Eliminates distortion due to the rest of the harmonics.

The active filter can eliminate distortion of individual mode on each of the phases, if the system is unbalanced or correcting all three phases equally if the system It is balanced.

The active filter (figure 1) consists of a filter AF (high frequency) (4) to eliminate the component due to the switching frequency, and subsequently an intensity sensor (5) per phase whose output (S) is proportional to the current of rectifier bridge input (1), for example, transformers hall effect

The mentioned outputs (S) once filtered by a low pass filter (L.P.F.) (6) layered at most half of The sampling frequency is sent to a processor (7) that consists of from:

- A harmonic distortion analyzer (8) in base to the fast Fourier transform, which gets the distortion actual current at point A due to non-linear load, in this case by the rectifier (1);

- A logic block (9) that decides the shot (12) of the inverter bridge (10) and receives in hystereris the signal of output (S_ {1}) of said inverter bridge (10).

For the capture of said output signal (S_ {1}) intensity sensors (11) are arranged, for example hall effect transformers similar to those above mentioned (5).

The processor (7) is previously found programmed with an ideal intensity (S_ {2}) or preset by the user, for example that is sinusoidal; so that the conjunction of distorted intensity (S) with distortion intensity (S_ {1}) reset the preset intensity (S_ {2}) or without distortion, ordering the logic block (9) the characteristics of tripping the inverter bridge (10) until this happens (i.e. (Figure 1) ib = ia + ic, with ib being the ideal or default).

The inverter bridge (10) is equipped with poles of power, for example, three single-phase IGBT'S bridges, eliminating each bridge the distortion of a phase of the network.

A coupling transformer (13) is available and isolation between the alternating voltage of the network and the continuous one of the active filter

The desired points are arranged inductances (14).

Results of the active filter prototype

- Kind of load: Nonlinear - Load Typical: Diode Rectifier or thyristors - Distortion of the intensity of the load: Anyone. - Load distortion typical: \ approx 30% - Waveform of the load typical: Quasi-rectangular (Ton- - -240) (Toff- - -120) - Active filter power: \ approx 15% PC - Distortion of the intensity wave after of the filter: <5% rms. - Harmonic more significant: 5th - Attenuation of harmonics: 85% - Front response time loading cargo: 10 ms

Other features.

- Harmonic attenuation of indica> 37º: Through L-C filter (Low Pass) - Losses in filter: approx 1.5% Pc. - Compensation of reactive: Excluded

The materials, dimensions, may vary proportions and, in general, those other accessory details or side effects that do not alter, change or modify the essentiality proposal.

The terms in which this report is written they are true and faithful reflection of the object described, being taken in its broadest sense and never in a limiting way.

Claims (5)

1. Active filter to be used in a network with a non-linear load, characterized in that it consists of a) first intensity sensors, one per network phase, whose output is proportional to the input intensity to the non-linear load; b) an inverter bridge whose outputs feed back to the network, with the distortion signal, being arranged in said Departures c) a few second intensity sensors, similar to the first intensity sensors; d) a processor programmed with a curve of preset intensity, consisting of d_ {1}) an analyzer block that receives the output signals of the first intensity sensors and that analyzes its harmonic distortion based on the rapid transformation of Fourier, obtaining the real distortion; d_ {2}) a logic block that receives the signal output of the second intensity sensors and ordering the trigger characteristics of the inverter bridge while the conjunction of the distortion signal with the actual distortion no recompose, with a preset differential, the intensity curve preset 2. Active filter to be used in a network with a non-linear load, according to the preceding claim, characterized in that the present inverter is provided with power poles. 3. Active filter to be used in a network with a non-linear load, according to claim one, characterized in that a low pass filter is provided at the output of the first intensity sensors. 4. Active filter to be used in a network with a non-linear load, according to claim one, characterized in that a high frequency filter is arranged in the network before the first sensors. 5. Active filter to be used in a network with a non-linear load, according to claim one, characterized in that the inverter bridge outputs are connected to the network by means of a coupling and isolation transformer.