The Research Of Variable Frequency Control System Of Long Stroke Pumping Unit

With the exploitation of oil resource, in our country, the main oil area has come into the phase that contains much water, and thick oil, the effect of exploitation of crude oil is becoming worse. Conventional beam-pumping unit is widely used in oil pumping by mechanical means, but its efficiency is very low and it consumes much energy, therefore, it can not meet the requirement of pumping oil and reducing the consumption of energy. For a long time, oil industry experts and technicians always bend themselves to reconstruct and create pumping units, they developed many new pumping units. One of the new pumping units is long stroke non-beam pumping unit. It features long stroke, large load, low energy consumption and wide field of application. In this thesis, a variable frequency control system of long stroke pumping units is designed, it takes significant effects on reducing cost of oil exploitation and accelerating the development of domestic economy.The analysis of the structure of long stroke non-beam pumping unit and the working principle of the variable frequency control system has been made in this paper. The primary function and qualification of pumping unit control system has been proposed. Then taking the programmable logic controller(PLC) as basic part to control the motor by frequency converter. On researching the working mode of pumping units and the method of controlling revs, this paper proposed the revs control algorithms, which contributes to making the pumping units working stably. Also, a closed-loop PID controller is designed, so the stroke length, stroke times per minute and stroke time can be adjusted accurately. As a result, the pumping control system can be applied to different oil well.The pumping control system is continuously and long time in work, a temperature measure and control equipment is designed on the basis of the working environment, which has automatic temperature measure and control functions. In addition, the pumping control system has self-check and self-diagnose functions.The variable frequency control system of long stroke pumping units has the features of high accuracy of controlling, high efficiency and high reliability, it...