Variable-frequency air-condition power supply power factor correcting device

Abstract

The invention discloses a correction device for power factor of variable-frequency air conditioner with a converter to change ac power from input port into dc power and a frequency converter to change dc power from said converter into three-phase ac power with need working frequency, which comprises: a zero-crossing detection circuit connected to input port of power, a control part connected with said circuit to determine electrical degree angle based on detection result and then output opposite control signal, a current regulation circuit connected with said control part and converter to regulate current waveform of ac power and improve current harmonic.

Description

technical field [0001] The invention relates to the technical field of frequency conversion air conditioners and power supplies, and more specifically relates to a power factor correction device for power supply of frequency conversion air conditioners. Background technique [0002] With the wide application of modern power devices and household appliances, the influence of power supply on the power supply quality of the power grid cannot be underestimated. As we all know, supplying DC after rectification from the AC grid is the most widely used basic conversion method in power electronics technology. However, the grid current with low power factor and high harmonic content generated by the controllable or uncontrollable rectification filter circuit causes the distortion of the grid voltage, increases the loss of the wire and transformer of the power distribution system, and increases the harmonic current of the neutral line, resulting in Serious electromagnetic interferenc...

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Problems solved by technology

However, it has some disadvantages: firstly, the passive filter device consumes a lot of effective materials and is large in size; secondly, it can only be made to have a filtering effect on certain harmonics, and the filtering effect is easily affected by component or system parameters, and grid frequency and other changes; again, under certain conditions, it may resonate with the system, causing accidents; in addition, when the harmonic source increases, the filter burden will increase, so that it may not be able to operate due to harmonic overload, etc.

However, its disadvantage is: because the switching frequency of the internal switching tube IGBT is very high (generally above 20K), it will generate considerable electromagnetic interference during operation, which will cause the system's interference voltage and interference power to exceed the standard. In order to suppress power factor correction The interference brought by itself generally requires multi-stage filtering, which will inevitably greatly increase the cost of the frequency conversion control system

In addition, due to its high operating frequency, it needs high-frequency inductor L1 made of amorphous magnetic material to cooperate with it, and the price of this inductor is very high, which further increases the cost of the system and is not conducive to market competition.

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