A frequency limiting control method and system for frequency conversion compressor

Abstract

The invention relates to a frequency limit control method and system for a variable-frequency compressor. The method comprises the following steps that S1, N temperature protection threshold values of a power module are set, wherein N is a natural number larger than or equal to three; N+1 temperature protection threshold value intervals are obtained through division according to the N temperature protection threshold values; S2, in the compression process of the compressor, the temperature of the power module is acquired; and S3, the acquired temperature of the power module is compared with the set temperature protection threshold values, the temperature protection threshold value interval where the temperature of the power module is located is judged, different functions are triggered according to the temperature protection threshold value interval where the temperature of the power module is located, the compressor performs corresponding operations, and then the actual operation frequency of the compressor is controlled. According to the frequency limit control method and system for the variable-frequency compressor, the temperature protection threshold values of the power module are detailed, the operation state of the compressor is restrained, the power module can respond the temperature in time reliably, and the system can be more stable and reliable.

Description

technical field [0001] The invention belongs to the field of frequency control of compressors, and in particular relates to a frequency-limiting control method and system for variable-frequency compressors. Background technique [0002] The traditional frequency conversion speed regulation system with PPFC (passive power factor correction) correction circuit consists of three links: rectification link, filter link and inverter link, such as figure 1 As shown, the rectification link mainly includes an inductor L and a rectification circuit composed of four diodes VD1-VD4, the filter link mainly includes a large-capacity electrolytic capacitor C, and the inverter link mainly includes an inverter. The main working principle of the traditional frequency conversion speed regulation system is as follows: the single-phase AC power supply AC from the AC power grid is converted into DC voltage after uncontrolled rectification and power factor correction in the rectification link, the...

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Problems solved by technology

As the operating frequency of the compressor increases, the input current of the compressor increases accordingly, which causes the power module to heat up seriously. If the power module works at high temperature for a long time, it will affect the reliability of the system and the life of the power module.

[0003] In order to prevent the temperature of the power module from being too high, the temperature of the power module can be reduced by improving the heat dissipation method of the power module, such as increasing the heat sink, changing the system air duct, etc. This solution needs to change the system hardware equipment and system arrangement design, and implement cumbersome and inconvenient

[0004] It is also possible to control the start and stop of the compressor through the software algorithm and the temperature protection threshold of the power module. When the temperature of the power module exceeds the set temperature protection threshold, the compressor stops working; when the temperature of the power module is lower than the overheat recovery threshold , restart the compressor, and gradually increase to the target frequency. This solution will cause the compressor to restart repeatedly, which will affect the life of the compressor and have a greater impact on the compressor and power module, and the power module will run at The high temperature state will also affect the reliability of the system and the life of the power module

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