Three-phase phase-hopping AC-AC frequency conversion method

Abstract

The invention discloses a three-phase phase-hopping AC-AC frequency conversion method. A frequency conversion main circuit is formed based on the same circuit as a traditional thyristor three-phase AC-AC frequency conversion method, and frequency conversion control is performed by an innovative method called phase-hopping frequency conversion, thereby achieving AC-AC frequency conversion. Three single-phase output phase-hopping AC-AC frequency conversion circuits are connected in a star connection manner. The trigger pulses of the second and third phases are delayed by 6.67 ms and 13.33 ms with respect to the first phase respectively, so that the three frequency conversion circuits can operate at a difference of 120 degree and output three-phase AC power with a phase difference of 120 degree to be used by a three-phase motor type load. The method is low in cost and high in reliability, and can overcome the shortcoming that a traditional AC-AC frequency converter can only output frequencies below 20 Hz, and has no ring current or no dead zone.

Description

Technical field [0001] The invention belongs to the technical field of frequency conversion, and relates to an alternating current frequency conversion technology, in particular to a three-phase jump and cross frequency conversion method. Background technique [0002] Electricity, as a clean energy source, provides a driving force for the development of various industries. It plays a very important role in the development of modern human society. Countries all over 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. Human 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 waste is serious. Therefore, today, when the energy problem is increasingly prominent, countries are competing for research on energy-saving technologies. In particular, my country’s curren...

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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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