The way to improve the quality of electric energy

 

The invention relates to power engineering and can be used to improve electric power quality in electrical systems, including the electrical systems of electrified Railways. The technical result - improvement of quality and reduction of unproductive losses of electric energy in power supply systems. The invention consists in the selection of the supply voltage harmonics, as well as the first harmonic is determined by the zero-sequence voltage, receiving from him a constant voltage and convert it to the voltage of the main harmonic of the network and return it to the network, due to this reduced voltage asymmetry of the network and reduced power consumption. 2 Il.

The invention relates to power engineering and can be used to improve electric power quality in electrical systems, including the electrical systems of electrified Railways.

The appearance in the net unbalanced and nonlinear load leads in power supply systems to deterioration of the quality of electric energy determined by the voltage unbalance ratio is their performance is an important task.

There is a method of improving the quality of electrical energy, which consists in reducing the level of higher harmonics and reduce the voltage unbalance of the network, to do this, configure the serial circuit at resonance voltage 3rd harmonic and include the path in the network (see markwart K., Electricity electrified Railways. -M.: Transport, 1982, S. 249-251).

Closest to the claimed method is improving the quality of electrical energy, which consists in reducing the level of higher harmonics and reduce the voltage unbalance of the network by configuring two groups of sequential circuits at resonance voltages on the 5th and 7th harmonics and include these groups of paths in the network (see Zielonko Century. And. and other Quality of electrical energy in industrial plants. - Kyiv: Tekhnika, 1981, S. 134-135).

The main disadvantages of this method is that when a small load in the connection paths increases the voltage up to unacceptable values, and that the reduction of the amplitudes of the higher harmonics caused by the growth of the active losses in the network due to a sharp increase in current at the harmonic resonance, which is configured sequential circuits (resistance to these is harmonically, irretrievably lost.

The technical result of the proposed method is to improve the quality of electrical energy, the voltage in the network in the case of small load increases and the active losses from higher harmonics are greatly reduced.

This is achieved by a method for improving the quality of electrical energy, which consists in reducing the amplitudes of the harmonics of the voltage and reducing voltage asymmetry extracted from the voltage harmonics voltage, and the first harmonic, which is determined by the voltage asymmetry, straighten the selected harmonic voltage, convert the rectified voltage into alternating voltage with a frequency equal to the frequency of the first harmonic of the network, and return a variable voltage in the electrical network.

The inventive method eliminates the major disadvantages inherent in the known method, namely, when the regime of low load voltage will not grow, because the amplitudes of higher harmonics and voltage asymmetry is negligible and they will not straighten up (working valves of the rectifier at the initial sites), or constant voltage will be little in the “dead zone” of the transducer and converted to AC is on the ground, while their energy is lost in Joul losses in the wires of the network, reactor, capacitor battery and earth. In the present method due to the selection of higher harmonics and the first harmonic is determined by the asymmetry of the circuit, straightening them and convert from DC to AC voltage and enable the voltage in the network is a significant part of the energy of the above harmonics will be returned to the network.

In Fig.1 is a diagram of one device that implements the inventive method.

In Fig.1 and 2, respectively forward and backward phase, 3 - rail cloth, 4 - transformer, the primary winding of which is connected in star, the secondary winding open triangle, 5 - rectifier, 6, 7, respectively inverters, led by a network of advanced and lagging phases, 8, 9 single - phase transformers.

The method is as follows. In the absence of load in the contact network at the output of the transformer 4, a rectifier 5, the inverters 6 and 7 there is no voltage, thereby idling the supply voltage is not growing (in a known way, the voltage increases). In case of load in phases 1 and 2, and this load is usually asymmetrical and Nesin is ericina component of zero sequence and higher harmonics, then the output of the transformer 4, you may receive the voltage of the first harmonic, the amplitude of which is determined by the zero harmonic voltage asymmetry of the contact network, as well as all higher harmonics that are multiples of the third, this voltage rectifier 5 is converted into a DC voltage supplied to the inputs of the inverters 6, 7, by which the DC voltage is converted into a sinusoidal frequency and returns to phase 1 and 2 in the form of energy the main harmonics through single-phase transformers 8 and 9.

The modeling method was carried out according to the circuit of Fig.2, where 10, 11, 12 - phase network, 13 - asymmetric adjustable network segment, 14 - adjustable nonlinear load (for example, 3-phase rectifier according to the scheme Larionov, a DC motor with adjustable torque on the shaft), 15 - 3-phase transformer with primary windings connected in star, and the secondary open triangle, 16 - bridge rectifier 17, the inverter 18 is adjustable load, 19 - analyzer characteristics of power consumption and measuring quality parameters of electric energy AR.5M, 20 - wattmeter, 21 - switch.

The simulation results of the method given the following options: if you disable the switch 21, the maximum src="https://img.russianpatents.com/chr/981.gif">=1,02, the switch 21 Kou=0,02%, Ku=1,79%, tq=0,13, load power 18 accounted for ~17% of the power consumption 13 and 14, which allowed us to conclude that when implementing the proposed method improves the quality of electricity and conserve electrical energy.

The inventive method can be carried out on the basis of known blocks in the contact network of electrified Railways, and power supply circuits of industrial enterprises.

Claims

The way to improve the quality of electrical energy, which consists in reducing the amplitudes of the harmonics of voltage and reduced voltage asymmetry, characterized in that the highlight of the voltage harmonics voltage, and the first harmonic, which is determined by the voltage asymmetry, straighten the selected harmonic voltage, convert the rectified voltage with inverter driven forward looking and backward phases of the network load, sinusoidal voltage with a frequency equal to the frequency of the first harmonic of the network, the voltage returns to the appropriate phase of the network in the form of energy

 

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FIELD: electrical engineering.

SUBSTANCE: two engineering solutions are proposed which are characterized in common engineering goal and common approach to solution. Power supply has transformer incorporating primary windings 1, magnetic core 2, and secondary windings 3; connected in series with the latter is diode bridge 4 closed through poles to reactor coils 5 and 6. Novelty is that central lead of reactor coils 5 and 6 is connected to neutral of load 7. The latter is connected to supply mains through switch 8. Diode bridge with similar double-coil reactor is inserted in series with neutral of all three phases of three-phase load. Novelty in this alternative is that reactor center tap is connected to neutral of supply mains. Damping (smoothing down current peaks) is effected both when three-phase and single-phase loads are connected.

EFFECT: enlarged functional capabilities, ability of damping inrush load currents.

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SUBSTANCE: proposed method involves evaluation of coefficients of current and voltage sinusoid distortions, checkup of these characteristics for compliance with their rated values, and generation of control signal by devices correcting sinusoid of voltage and current levels. This method is characterized in that subharmonic and higher fractional components of current and voltage are included in evaluation of coefficient of current and voltage sinusoid distortions due to determination of actual period of voltage and current variations with time.

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FIELD: railway transport.

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