Method for protecting power consumers against higher harmonic components

FIELD: electrical engineering.

SUBSTANCE: proposed method used to enhance quality characteristics of electrical energy supplied to users susceptible to impact of negative factors of electrical-energy higher harmonic components includes generation of higher harmonic components of current in network which are acting in phase opposition relative to higher harmonics of supply mains.

EFFECT: enhanced quality characteristics of electrical energy supplied to users.

1 cl, 3 dwg

 

The invention relates to electrical engineering, and in particular to methods that enhance the quality parameters of electric energy to consumers, subject to the influence of negative factors of higher harmonic components of electrical energy.

Known methods of reducing the level of higher harmonic components of electric power, including power resonant filters, a simple notch filters or a complex combination of filters (bandpass)that serve to filter multiple harmonics. Manufactured power resonant filters 5, 7, 11 and 13 harmonics (Zielonko IV of the Higher harmonics in power supply systems of industrial enterprises [Text] / Ivilege. - M.: Energoatomizdat, 1984, pp.109). The principle of operation of such facilities based on the occurrence of resonance in their own oscillatory circuit tuned to a specific frequency. Filters can be installed in the network for the separation of linear and nonlinear loads (barrier filters) or absorption (bypass) currents harmonics. Improving the efficiency of power supply is also provided by the use of power resonant filters in the high-speed compensating devices. The main disadvantage of the known methods, as shown by the many years of their operation, are:

incomplete compensation of the " new " harmonics;

filtering only the higher harmonic components of a certain frequency (number);

- the inability to compensate for the higher harmonics when a sudden change in the spectrum.

This leads to increased heating of current-carrying parts, the triggering of the protection of electrical installations, damage to sensitive microprocessor-based equipment process control.

As the prototype accepted way of improving the quality of electrical energy, which consists in the selection of the voltage harmonics voltage, and the first harmonic is determined by the voltage asymmetry, the straightening of the selected harmonic voltage, converting the rectified voltage into alternating voltage with a frequency equal to the frequency of the first harmonic of the network, and the return of the AC voltage in the electrical network (Patent RU №2237334 C2, H 02 J 3/01, H 02 J 3/26. The way to improve the quality of electric energy // publ. 2004). The disadvantages of this method are:

- providing incomplete compensation of higher harmonics, limited by the filter characteristics of the constituent;

filtering only certain frequency spectrum of higher harmonic components;

- the impossibility of a satisfactory compensation of higher harmonics when a sudden change in the spectrum.

Izobreteny the m solves the problem of improving the quality parameters of electric energy to consumers, using power converters and other electrical equipment, which is the source of higher harmonics by full compensation of higher harmonics due to the generation of the network of higher harmonic components of electricity, operating out of phase with the higher harmonics of the core network, using the energy of the electrical network, which will be compensated.

To achieve the mentioned technical result in the proposed method, including the selection of the first and higher harmonics of the network, apply the generator harmonics representing controlled thyristor Converter fed from the network where the compensation of the higher harmonics.

Distinctive features of the proposed method are generated in the network of higher harmonics current AC managed spectrum, operating out of phase with the harmonic core network.

The proposed method is illustrated in figure 1 and figure 2, which shows the scheme for compensation of higher harmonics and curves of the currents at the output of the current transformer and the input of the analyzer harmonics.

Scheme 1 shows a measuring current transformer 1, the higher harmonics analyzer 2 with the first harmonic filter 3, the filter higher harmonics 4, controlled thyristor Converter 5 and rectifier installation 6.

The claimed ability is b involves the use of a measuring current transformer 1 (Fig 1), servant to bring the network to the magnitude of the current up to 5 a, which is suitable for further transformation. The current transformer is connected to any phase of the electrical network due to the symmetry of higher harmonics in all phases. The current transformer 1 requirements of the minimum current and the angular error (accuracy class 0,5) and lack of distortion power conversion at higher frequencies (up to 3 kHz). The curve of output current 1 shown in figa. For analysis of higher harmonic components of the current network is higher harmonics analyzer 2 (figure 1), representing the high-speed analog-to-digital Converter connected to the current transformer 1 and serves to convert the information received from 1 into a digital form suitable for further processing. The higher harmonics analyzer decomposes the entire spectrum of higher harmonics current at frequencies that are multiples of 50 Hz, and determines their level and initial phase. To the analyzer 2 requirements of the work at frequencies up to 3 kHz. Considering the fact that the analysis focuses on only the higher harmonic components of the current network, it is necessary from the curve of the current obtained at the output of the transformer 1, to exclude the curve of the main harmonic of the current network. For these purposes, is the first harmonic filter 3, representing a resonant filter that is configured on the network frequency (50 Hz) (figure 1). the device 3 is connected to the input 2 or is included in its composition. Curve output current 3 shown in figb. For power compensation devices of higher harmonics is an electrical network that is compensation. The filter higher harmonics 4 is used to eliminate the influence of higher harmonic components of the current rectifier installation on the electrical network. For the generation of higher harmonics of the current in the network is a cascade of fast-controlled thyristor converters 5 (figure 1), which are powered from the mains. Controlled thyristor Converter is a device that operates on the principle of the frequency inverter. The power of 5 is chosen in the range of 1-2% of the rated capacity of the network. For rectifying alternating current network, you need to supply 5 to use power rectifier installation 6.

The management of the primary phase and the higher harmonic current generated by 5, is based on the principle of feedback from 2 (figure 1), through an electrical network, which will be compensated. The control criterion is to minimize the level of higher harmonics at a specific frequency.

Higher harmonics that occur in the network, carrying food controlled thyristor Converter and rectifier have a fixed range and offset 4.

To the structural elements of the installation predyavlyayuschie resistance to high voltage and security staff working at high voltage.

The way to protect consumers from the effects of higher harmonic components, including the allocation of the first and higher harmonics of electricity energy use of the electric network, which is compensation, characterized in that, to ensure compensation of higher harmonic components of the electricity generated in the network of higher harmonic currents, operating out of phase with the higher harmonics of the core network.



 

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