DC bus frequency converting control circuit employing small-capacitance capacitor and frequency conversion device

Abstract

The invention discloses a DC bus frequency converting control circuit employing a small-capacitance capacitor and a frequency conversion device. The circuit includes a rectifier, a DC bus, the small-capacitance capacitor, an inverter, an inverter control module, a power supply switch, an inverter control module power supply circuit and a power supply control module. The power supply switch is connected between the rectifier and an AC input. The inverter control module power supply circuit is connected with the AC input and provides power for the inverter control module. The power control module controls the power supply switch to close after the inverter control module power supply circuit runs stably so as to enable the AC input to connect with the rectifier. After the complete machine iselectrified and the AC input is provided, the inverter control module power supply circuit is started for providing working power for the inverter control module. After the inverter control module power supply circuit runs stably, the power supply switch is controlled to close so as to enable the AC input to connect with the rectifier. Time-shared electrification of an inverter control circuit and an inverter working circuit are enabled separately in a two-stage electrification control method, so that frequency conversion reliability is improved.

Description

technical field [0001] The invention belongs to the technical field of motor control, and in particular relates to a DC bus small-capacity capacitor frequency conversion control circuit and frequency conversion equipment. Background technique [0002] There are two types of products in the air conditioner market: fixed-speed air conditioners and inverter air conditioners. When the fixed-speed air conditioners are started, they will generate a huge inrush current that will affect the operation of other electrical appliances in the power grid. Because of the low cost of fixed-speed air conditioners, they occupy a large proportion of the air conditioner market. [0003] The DC filtering link of the frequency conversion control of the traditional inverter air conditioner is composed of electrolytic capacitors with thousands of microfarads or even thousands of microfarads. Third, in order to improve the harmonics caused by the charging and discharging of the filter capacitor, it...

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Problems solved by technology

[0002] There are two types of products in the air conditioner market: fixed-speed air conditioners and inverter air conditioners. When the fixed-speed air conditioners are started, they will generate a huge inrush current that will affect the operation of other electrical appliances in the power grid. Because the cost of fixed-speed air conditioners is low, it occupies a large proportion of the air conditioner market

[0003] The DC filtering link of the frequency conversion control of the traditional inverter air conditioner is composed of electrolytic capacitors with thousands of microfarads or even thousands of microfarads. Third, in order to improve the harmonics caused by the charging and discharging of the filter capacitor, it is necessary to add a PFC (Power Factor Correction, power factor correction) circuit to correct the power factor and solve the harmonic problem; and the switching devices in the PFC circuit operate at a higher switching frequency It will produce a lot of power loss and a lot of EMI (Electro Magnetic Interference, electromagnetic interference) interference. If this problem is not solved, it is necessary to increase the cost of EMI filtering. Therefore, the cost of the traditional frequency conversion control circuit is high, and the electrolytic capacitor and PFC loop The power device is a failure-prone device of the frequency conversion controller, especially the life of the electrolytic capacitor is more obviously affected by the temperature and voltage

[0004] In view of the above problems, in the prior art, there is a proposal to replace the electrolytic capacitor with a small-capacity film capacitor, which can save the PFC part and the EMI filter part, realize the miniaturization and low cost of the frequency conversion control circuit, and can also eliminate the life of the electrolytic capacitor. Short problem, but usually the capacity of small film capacitors is small, resulting in instability of the DC bus voltage. When the system impedance matching is not suitable, it will cause system resonance and system overvoltage faults. In order to overcome these problems, existing solutions The solution is to use the driving algorithm to solve the problem of DC bus voltage stability through the detection of parameters such as AC input voltage and bus voltage.

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