Galloping start control method of frequency converter

Abstract

A galloping start control method of a frequency converter comprises the steps that the line voltage of the frequency converter is sampled, processed correspondingly and then output to a digital signal processor, and then a sampling software hysteresis method is used for shaping positive voltage to obtain square-wave voltage signals. The frequency of the square-wave voltage signals is calculated, and the start method of the frequency converter is controlled according to the frequency of the square-wave voltage signals. Particularly, when the frequency of the square-wave voltage signals is larger than or equal to 1 Hz, the frequency converter is in a rotation state, and therefore the frequency converter is controlled to start at the current frequency, and damage to the frequency converter or a load caused by reverse rotation of the frequency converter or inconsistence of the current rotation frequency is avoided. The calculation method of the galloping start control method of the frequency converter is simple, convenient and rapid to operate, and galloping start control over the frequency converter can be finished without a complex algorithm.

Description

technical field [0001] The invention relates to a method for controlling the start of a frequency converter, in particular to a method for controlling the start of a frequency converter on the fly with a simple algorithm. Background technique [0002] High-power high-voltage inverters are widely used in various fan and pump equipment in petrochemical, electric power, metallurgy, urban construction and other industries, and play an important role in reducing consumption, saving energy, and improving processes. However, with the expansion of the application field of the system, the simple speed sensorless VVVF control high-power high-voltage inverter also has many functions that need to be perfected. The so-called "flying start" is more important when the inverter is started when the motor rotor is in a rotating state. Features. In some applications such as fans and pumps, the moment of inertia of the load carried by it is generally relatively large. When the load carried by ...

AI Technical Summary

Problems solved by technology

If the inverter is powered off and on again due to power grid reasons, misoperation or random interference, the rotor of the motor is still in the rotating state. If the inverter can only start when the rotor is stationary, in many cases The petrochemical process, power plant boiler and other production processes require a strict working environment. If the motor driven by the frequency converter cannot resume operation in time, the entire system will stop production or the unit will be disconnected. For a large-scale system, unexpected system shutdown will cause will cause users to suffer immeasurable economic losses

[0004] At present, the common method in the market is to measure the speed through an external speed measuring device, such as a photoelectric encoder or a photoelectric switch. However, this cannot be installed in some occasions, and it will increase the cost of the system and reduce the reliability of the system.

[0005] In addition, there are some software methods to estimate the speed. However, this method is completely dependent on software, and the search effect is greatly affected by the maturity of the software, and has many limitations.

[0006] For example, in "Methods and Devices for Frequency Converter Tracking Motor Speed", the output voltage and frequency adjustment changes of the given current and feedback current are compared with the VF curve voltage to search for the frequency. This method cannot effectively judge the direction of the motor, and motor feedback will occur. turn situation

And the algorithm is more complex

Images