1、 Preface

In general, the water injection pump process of oilfield water injection station mostly adopts the traditional water source well deep well pump, which supplies water to the large water storage tank, and then the water is supplied to the water injection pump from the water storage tank by the water injection pump, and then the water is injected into the formation by the water injection pump. Most of the water injection pump motors are high-power motors (110, 185kW). The outlet pressure of the water injection pump is usually achieved by adjusting the valve. The operator can adjust the valve by observing the pressure of the pressure gauge at any time, while the rated speed of the water pump motor is basically unchanged. Therefore, for the motor, the phenomenon of large horse pulling the car is very serious. There are many water pumps in the pipe network, and the process is complex, which wastes electric energy, It also increases the labor intensity of operators. The constant pressure water supply control system of the frequency converter is used to realize stepless speed regulation of the pump motor, automatically adjust the operating parameters of the system according to the requirements of the water injection pressure, and keep the water pressure of the pipe network constant when the water consumption changes to meet the water injection requirements. The variable frequency speed control system is an advanced and reasonable energy-saving water supply system, which has been greatly developed in practical application. With the rapid development of power electronics technology, the functions of the frequency converter are becoming stronger and stronger. It is of great significance to make full use of the various functions of the frequency converter for the application of the constant pressure variable frequency water supply system.

2、 Application of QD800

1. The variable frequency speed control system device uses the Aozhuo frequency converter as the main control device. It collects 4~20mA signals through the pressure transmitter and transmits them to the PID controller of the frequency converter to monitor the pressure change of the water supply and water injection pipe network, control the output frequency of the frequency converter, adjust the working state of the water pump, and keep the pipe network pressure in a constant pressure range. The motor power of the deep well pump of the water source well is 5.5kW, which is driven and controlled by 7.5kW frequency converter; The motor power of the water injection pump is 110kW (or 185kW), which is driven and controlled by 132kW (or 200kW) frequency converter. According to different water volume and pressure requirements, variable frequency operation and power frequency standby are implemented to achieve constant water pressure. The system sets parameters through PID controller, and controls the operation of the system according to variable frequency display, pressure display, undervoltage timeout, water pressure alarm indication and upper and lower limit holding pressure. Install a pressure transmitter on the front pipe network at the inlet of the water injection pump to control the operation of the frequency converter of the deep well pump; Install a pressure transmitter on the outlet pipe network of the water injection pump to control the operation of the frequency converter of the water injection pump, control the output frequency of the frequency converter, thus changing the speed of the water pump, and achieve the purpose of controlling the constant pressure of the pipe network. When the actual pipe network pressure is less than the given pressure value, the output frequency of the frequency converter increases, the motor speed increases, and the pipe network pressure begins to rise; On the contrary, the output frequency of the frequency converter decreases, the speed of the motor decreases, and the pressure of the pipe network decreases. The system automatically adjusts the actual pressure to keep the pipe network pressure constant around the set pressure. The variable frequency speed control system forms a closed-loop control of controllable parameters during the operation of the water pump, implements constant pressure water supply, maintains the balance between the water injection system and the consumption, and realizes automatic control.

In the past, the flow of water injection pump was generally: water source well - water storage tank - feed pump - water injection pump. Install the variable frequency speed control system. Through constant pressure water supply control, the process can be simplified as follows: water source well - water injection pump. This technical innovation simplifies the process flow, reduces the operation steps and frequent start and stop of the water source well, realizes automatic water supply, and can effectively inhibit the phenomenon of large horse pulling the cart in the operation of the pump, which not only reduces the labor intensity of the operator, but also saves electric energy.