A three-phase three-phase three-phase jump-crossing alternating frequency conversion method

Abstract

The invention discloses a three-phase three-phase series-connected three-phase stepping alternating-current frequency conversion method. The main frequency conversion circuit is formed on the basis of the same circuit as the traditional three-phase three-phase three-phase series series thyristor alternating-current conversion method. Separate control, triggering a pair of thyristors in the positive group and the negative group simultaneously for each heavy circuit, so that the output terminal of the heavy circuit is connected with the input of one phase of the heavy circuit, and after a time interval related to the expected output frequency. The next time it is triggered, the heavy output terminal is connected to the input of the next phase. By continuously switching this connection relationship, the phase of the output voltage is continuously changed, thereby obtaining the effect of changing the overall output frequency. At the same time, by arranging the phase of the output voltage of each heavy circuit according to the needs, and adjusting the triggering time of each heavy thyristor, it can realize the output of AC power with a three-phase phase difference of 120° for use by three-phase motor loads. It has the advantages of low cost and high reliability.

Description

technical field [0001] The invention belongs to the technical field of frequency conversion, and relates to an alternating frequency conversion technology, in particular to a series three-phase triple-hop alternating alternating frequency conversion method. Background technique [0002] As a clean energy source, electric energy provides the driving force for the development of all walks of life. It plays a very important role in the development of modern human society. All countries in the world attach great importance to the development of electric energy. In recent years, my country has also invested a lot in the development of electric energy. Manpower and material resources. However, in various fields where electric energy is widely used, the utilization rate is low, especially in the field of transmission, where the phenomenon of waste is serious. Therefore, in today's increasingly prominent energy problems, countries are competing to conduct research on energy-saving te...

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Problems solved by technology

These three methods have their own disadvantages: due to the "dead zone" time in the no-circulation mode, the minimum "dead zone" time that can be realized at present is 1.1ms. When the output frequency is high, such as close to 50Hz, the time per cycle is only 20ms If there are 2 current zero crossings per cycle, the total "dead zone" time is greater than 2.2ms, that is, the system has no output for more than 10% of each cycle, which will make the output waveform worse and have too much harmonic content , can not be used in the actual system; the circulation method has the disadvantages of high cost and large volume because it needs multiple large-capacity reactors, and the reactor of the main circuit will reduce the total power factor of the system; the small circulation method uses The reactor capacity of the reactor is much smaller than that of the circulating current method, and it has great advantages in terms of cost, volume and total power factor reduction compared with the circulating current method. At the same time, there is no "dead zone" time in the system work, but the reactor capacity is too small If the circulating current is too large and the capacity is too large, it will have the disadvantage of being closer to the circulating current mode, and the system will switch between the circulating current mode and the non-circulating current mode during work, and the inconsistent working status will also lead to certain output waveform distortion. The design and control of the whole system are more complex

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