Device for eliminating the distortion of the voltage curve in distribution networks, ac

 

The invention relates to electrical engineering, in particular to power active filters, and can be used in power supply systems electrical and power circuits with distorted voltage and current loads to ensure collaboration powerful sharply varying loads sensitive to the distortion of the voltage receiving terminals, as well as to improve transfer efficiency and energy consumption. The technical result is to improve the waveform of the supply voltage. For this purpose, the device for eliminating the distortion of the voltage curve in distribution networks, the AC contains a source of alternating voltage, a controlled current source, a voltage sensor connected to the current-carrying busbars of the distribution network of an alternating current, and a current sensor. 2 Il.

The invention relates to electrical engineering, in particular to power active filters, and can be used in power supply systems electrical and power circuits with distorted voltage and current loads to ensure collaboration powerful sharply varying loads sensitive to voltage distortion, the receiver is correct the distortion of the voltage curve in distribution networks, AC (see, for example, L. Gyugyi, E. Strycula Active AC Power Filter. // IEEE Trans. on Industry Applications, p.p. 529-535,1976).

Closest to the present invention is a device for eliminating the distortion of the voltage curve containing passive LC-filter and active filter connected in series (see N. Fujita, H. Akagi. A Practical Approach to Harmonic Compensation in Power Systems - Series Connection of Passive and Active Filters. IEEE Trans. on Industry Applications, vol. IA-27, 6, pp. 1020-1025, 1991).

The presence of the capacitors in the power circuit of such devices makes the General lack of such technical solutions to the problem of attaching a condenser batteries directly to AC current and potential issues associated with the resonance of such batteries with AC power, resulting in lower static and dynamic stability of the network. In addition, this leads to a significant increase in the voltage drop resonant harmonics on the internal impedance of the source and, as a consequence, a significant distortion of the voltage curve on the buses feeding the load.

The essence of the invention lies in the fact that in the device for eliminating the distortion of the voltage curve in distribution networks, AC, containing the source of alternating voltage, a controlled current source, the sensor is Amy a current source and a source of alternating voltage connected in parallel. Connected in parallel to the controlled current source and a source of alternating voltage connected to the current-carrying busbars of the distribution network of an alternating current through the current sensor.

In Fig. 1 presents a diagram of the device for eliminating the distortion of the voltage curve in distribution networks, AC, Fig.2 is a waveform of operation of the device.

Device for eliminating the distortion of the voltage curve in distribution networks, AC (Fig.1) contains a source of alternating voltage 1; a controlled current source 2 connected in parallel to a source of alternating voltage; a voltage detector 3 connected to the current-carrying bus distribution network of AC VT; the current sensor 4, through which is connected in parallel to the controlled current source and a source of alternating voltage connected to the current-carrying bus distribution network of AC. To live tyre distribution network of AC VTconnected and the load 5.

The device operates as follows.

Generated power is 1 in the distribution network of AC presents nonideal source VSwith an internal impedance Z

The current harmonics generated by nonlinear loads Ihdivided into two parts. One part IShflows through the branches of the source, the other IFh- the branch impedance To.

On the basis of the first Kirchhoff's law, the current IFhin the branch with impedance is defined as IFh= 1h- ISh. (1) on the other hand, on the basis of the second Kirchhoff's law for this circuit we have the following expression: KIFh= ZLIh. (2) Substitution of IFhfrom (1) into (2) leads to the following result: KIFh- KISh= ZLIh, (3) where for the current harmonics IShflowing through the source, you can writeThe voltage on sideline as VT= VS- ZSISh. (4)
Analysis (3) shows that if |K-ZL|0, the current IShalso approximately equal to zero.

In other words, the current harmonics stops flowing through the branch source and completely flows through the branch impedance K, that is, the impedance K bypasses the source for harmonics of the nonlinear load. The branch source flows only active component of the load current Ia. Because harmonic currents from nonlinear loads in this case no longer flow through the source, and does not create a voltage drop of harmonics on the internal impedance of the source, and therefore does not distort the shape of the curve of the voltage VTon the supply tyres. Indeed from (4) it follows that under the above conditions VTVS.

Parallel branch with the required impedance is implemented using a controlled current source 2.

Data about the voltage at the busbars of the distribution network of AC VTand current tyre distribution network from the voltage detector 3 and the current sensor 4 is coming to a controlled current source. A controlled current source fulfills the desired impedance. Thus the giving of the voltage on the internal impedance of the generator, that, in turn, provides a sinusoidal curve of the supply voltage on the tyre distribution network of AC VT.

In Fig. 2 shows waveforms of the mains voltage (top) and current generator (bottom). Scale: voltage 200 V/div., current 50 a/div., time of 0.01 s/div.

From the waveforms shows that before the controlled current source began its work, the voltage on the supply bus bars and the current generator contained a large number of harmonics.

However, when the controlled current source starts its operation, the voltage on the supply bus bars and the current generator be strictly sinusoidal.

The use of the invention allows to improve the shape of the curve of the supply voltage, that is, to reduce harmonics in the supply voltage to zero than to ensure collaboration powerful sharply varying loads sensitive to voltage distortion power receiving terminals.


Claims

Device for eliminating the distortion of the voltage curve in distribution networks, AC, containing the source of alternating voltage, a controlled current source, a voltage sensor connected to tocover current and a source of alternating voltage connected in parallel and through the current sensor is connected to the current-carrying bus distribution network of AC.

 

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