Electromagnetic compensator of power grid third harmonic

FIELD: electricity.

SUBSTANCE: invention refers to the sphere of electrical engineering and is of relevance for design and development of technical equipment ensuring improved quality of electric power transmission through three phase four-wire electrical networks and reduction of power losses related thereto due to anharmonicity and asymmetry minimisation. The desired effect is due to the electromagnetic compensator identifying among the phase currents the one whose frequency value is equal to 150 Hz current which current is immediately injected in phase opposition to the third harmonic of the neutral lead current.

EFFECT: compensation for the largest spectral harmonic as circulating within the currents neutral lead.

3 cl, 2 dwg

 

The invention relates to electrical engineering and can be used to improve quality and reduce power loss by reducing nonsinusoidal and unbalance in three-phase four-wire electric networks with earthed neutral.

Know the device /1/containing three transformer windings of which are included in the star schema with zero - triangle". For longitudinal insertion of such a transformer in the electrical network, the third harmonic currents close in the windings, connected in a triangle, and are not in the line currents.

The disadvantages of this device are large consumption of materials and incomplete compensation of the third harmonic with an unbalanced load in the network phases, which reduces the efficiency of suppression a current of the third harmonics that distort the sine wave voltage.

The known method, which is implemented device adopted for the prototype /2/, consisting of a measuring current transformer analyzer harmonics, the filter of the first harmonic, filter higher harmonics controlled semiconductor Converter and rectifier.

The disadvantages of this device include its large consumption, complexity and low reliability when the overvoltage arising in the primary electrical network.

Task Appl is imago invention is to improve reliability while maintaining the accuracy of the compensation of the third harmonic current component and the dematerialization of the device.

This technical result is achieved by the electromagnetic compensator of the third harmonic of the electrical network containing the measuring current transformer, the rectifier and the inverter, added three current transformer, the primary winding of which is unipolar included in rassechku linear wire network, and the beginning of their secondary windings form with the end of the secondary winding of the current transformer common point, the ends of the secondary windings of the three transformers of current through the rectifier is connected to the positive output terminal of the inverter, a negative output clamp which is connected with the beginning of the secondary winding of the current transformer, the primary winding of which is included in the neutral wire network unipolar three mentioned current transformers, the input terminals of the Converter connected between one phase and neutral wires of the network, in addition, the three-phase rectifier is carried out and the cathode form a common point with the positive output terminal of the inverter, and each of the anodes of the rectifier is attached to the ends of the secondary windings of the three transformers.

In addition, the measuring current transformer can be made in the form of a toroidal magnetic core located therein a secondary winding, Katya the soup neutral network, or magnetic circuit with break-type clamp.

The inventive electromagnetic compensator of the third harmonic of the electrical network shown in figure 1, and figure 2 shows graphs of harmonic components of voltages and currents for continuous operation.

Electromagnetic compensator of the third harmonic of the electrical network contains included in the neutral N and phase conductors L1-L3 of the measuring current transformer 1 and additional transformers 2, 3, 4, to the secondary windings of which are connected to the rectifier 5 and the Converter 6 (Fig 1). The diodes 7, 8, 9 rectifier 5 their anodes form a common point with the positive output terminal of the inverter 6.

The Converter consists of a capacitor 10, diode 11, 14, Zener diodes 12, 13, electrolytic capacitor 15, the chip stabilizer 16, resistor 17 and the trimmer resistor 18 (power supplies. Amateur circuit. Part 2. Comp. Hon. - M: FE the Radiosoftware, CJSC "Magazine "Radio", 2003. - p.178).

The transformers 1-4 comprising electromagnetic compensator have the same ratio and accuracy class.

Electromagnetic compensator of the third harmonic of the electrical network operates as follows.

Single-phase nonlinear loads cause the flow in the phases and neutral che is areaprovides network nonsinusoidal currents, among which is dominated by the third harmonic. Under the action of stresses UL1UL2and UL3(2) in the secondary windings of the transformers 2, 3, 4 diodes 7, 8, 9 are switched alternately by 1/3 period of industrial frequency. The current will carry out the rectifier diode, the potential of the anode of which is relatively common point of the transformers 2, 3, 4 higher than other diodes. Switching diodes occurs at points in time corresponding to the intersection points of the sine of the phase voltages, so the curve of the rectified voltage Udhas the form of the envelope of the sinusoid phase voltages, currents running through the secondary windings of the current transformers (figure 2). The curve of the rectified current idrepeats the curve of the rectified voltage, but because of the presence of the inductive resistance of the secondary winding of the current transformer 1 is slightly flattened. The frequency of pulsations of the rectified current flowing in the secondary winding of the current transformer 1 with respect to the fundamental frequency of the primary network is equal to three.

For compensation arising by straightening the constant component of Edthe Converter 6 is formed protivoelektrodvizhushchej force, which is directed counter electromotive force of the rectifier 5. In the result, the current flowing through the current transformer 1 current iinfrequency of 150 Hz will not be with erati a permanent part of I d(figure 2). Exact compensation for DC rectifier can be done trimmer 18 Converter 6 (Fig 1).

Thus, decreases the intensity of electromagnetic compensator increases the reliability and accuracy of the compensation of harmonics, which improves the quality of electric energy, reduces loss of active power and voltage losses in all network elements from the current third harmonic component.

Sources of information

1. Briskin DE Electric machine. In 2 hours Part 1 / Daibouken, Aesoteric, Vshost. - M.: Higher school, 1987. - s.

2. Patent RU 2294044. CL. 02J 3/01, 02J 3/26, 2007, BI 5.

1. Electromagnetic compensator of the third harmonic of the electrical network containing the measuring current transformer, the rectifier and the inverter, characterized in that it additionally introduced three current transformer, the primary winding of which is unipolar included in rassechku linear wire network, and the beginning of their secondary windings form with the end of the secondary winding of the current transformer common point, the ends of the secondary windings of the three transformers of current through the rectifier is connected to the positive output terminal of the inverter, a negative output clamp which is connected with the beginning of the secondary winding of the ISM the measuring current transformer, the primary winding of which is included in the neutral wire network unipolar three mentioned current transformers, the input terminals of the Converter connected between one phase and neutral wires of the network, in addition, the three-phase rectifier is carried out, and the cathode form a common point with the positive output terminal of the inverter, and each of the anodes of the rectifier is attached to the ends of the secondary windings of the three transformers.

2. Electromagnetic compensator of the third harmonic of the electrical network according to claim 1, characterized in that the measuring current transformer is made in the form of a toroidal magnetic core located therein a secondary winding, covering the neutral wire network.

3. Electromagnetic compensator of the third harmonic of the electrical network according to claim 1, characterized in that the measuring current transformer is made magnetic circuit with break-type clamp.



 

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