Negative sequence inhibiting device and method for asynchronous motor under unbalanced voltage condition

Abstract

The invention relates to negative sequence inhibiting device and method for an asynchronous motor under an unbalanced voltage condition. The device is characterized in three phases of a positive / negative sequence voltage current detecting module are respectively correspondingly connected with three phases at the asynchronous motor; the input side of a negative sequence inhibiting wave generation module is connected to a power grid through a voltage regulator; a power supply module is connected with the power grid. According to the technical scheme, the device has the advantages that the positive and negative sequence components and unbalance factor of the asynchronous motor end of the motor in running are acquired on real time; the microcomputer is used for calculating and processing, a corresponding control instruction is sent to the negative sequence inhibitor to generate voltage waveform for inhibiting the negative sequence component of the asynchronous motor, so as to reduce the adverse influence of the negative sequence component on the asynchronous motor; in addition, when detecting that the voltage unbalance factor of the asynchronous motor end and the stator single-phase maximum current exceed the extreme safety operation range, an alarming signal is sent, a power supply of the asynchronous motor is cut off, and therefore, the safety operation of the asynchronous motor is ensured.

Description

technical field [0001] The invention relates to a negative-sequence suppressor and a realization method thereof, in particular to an asynchronous motor negative-sequence suppressor and a realization method thereof under the condition of unbalanced voltage. Background technique [0002] The grid voltage imbalance is mainly caused by the uneven distribution of single-phase load and three-phase in the grid. At this time, there is a certain negative sequence component in the power supply system, and the negative sequence is extremely harmful to the power system, threatening the safety and economic operation of the power system. Negative sequence current will bring greater harm to the operation of power generation, transmission, transformation, power distribution and power consumption equipment, mainly reflected in: [0003] 1) Increase the additional loss of the synchronous generator and the heating of the rotor, and cause additional vibration; [0004] 2) Make the relay protec...

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Problems solved by technology

[0005] 3) The negative-sequence current causes the unbalance of the three-phase current, so that one of the three-phase currents of the power transformer has the largest current, which limits the rated output of the transformer and reduces its effective utilization rate. In addition, it also causes increased magnetic flux leakage and local overheating of the transformer. ;

[0006] 4) When the voltage is unbalanced, the voltage of a certain phase will inevitably be too high or too low, which will cause overvoltage or undervoltage operation of single-phase electrical equipment. If it is a three-phase electrical equipment, such as the most typical three-phase asynchronous motor , there will be adverse effects such as reduced output capacity, increased loss, severe heat generation, and vibration, which will cause waste of electric energy, affect the safe operation of electrical equipment, and even cause industrial operation interruption and major economic losses.

If there is a three-phase voltage imbalance in the grid voltage, it will lead to adverse effects such as increased energy consumption, increased temperature rise, and reduced life. In severe cases, it will endanger the safe operation of the motor and affect normal production.

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