Application of ES500 frequency converter in a tower pumping unit in an oilfield
详细说明
As a new type of energy-saving and high-efficiency mechanical oil extraction equipment that has developed rapidly in recent years, the comprehensive energy saving rate of tower unit is 30% higher than that of beam pumping unit. However, the beam pumping units driven by asynchronous motors commonly used in oil wells still have defects such as system redundancy, low motor efficiency and low power factor. Therefore, with the increasingly high requirements for energy conservation and emission reduction, finding a more environmentally friendly and energy-saving drive device has become a top priority. The direct-drive pumping unit drive composed of ES500 inverter and permanent magnet synchronous motor system is a good choice. Compared with using an AC asynchronous motor as a driving device, the system reduces the working loss of the pumping unit system and improves the working efficiency of oil pumping.
Application Environment
The tower pumping unit system consists of a power transmission system, a control system frame and a mobile device, a balance box, and a safety brake system for the balance box. It is used in oil production conditions of stroke times. The structure of the tower pumping unit is shown in Figure 1.
The core of the system lies in the permanent magnet synchronous motor. Permanent magnet synchronous motor has the characteristics of large starting torque at low speed, wide speed regulation, high efficiency and small steady-state speed error. Smooth speed regulation can be achieved by matching ES500 inverter. Under rated voltage, the speed can be adjusted between 0-250r/min. The excitation of the electric motor is derived from permanent magnets, so that the power factor is above 0.98.
Load characteristics of tower pumping unit: The tower pumping unit carries a constant torque load, which requires a torque exceeding the rated torque value when starting. The working state is relatively close to that of the elevator. It is divided into two processes of ascending and descending. It supports hovering and has high requirements on the torque control characteristics of the inverter. Due to the characteristics of the permanent magnet synchronous motor, when the counterweight of the tower pumping unit is unbalanced There will be energy feedback, so it needs to be fed back to the grid through the feedback device or consumed in the braking resistor to prevent the bus voltage from overshooting.
The requirements of a 14kW motor in an oil field are used as an example to illustrate. The specific requirements are as follows:
Ø The motor parameters provided by customers are shown in Table 1. The inverter needs to complete the fast start and stop control, and one channel of 4-20mA analog output;
Table 1: 15kW permanent magnet synchronous motor parameters
Motor parameters | rated power | Rated voltage | Rated current | Rated frequency | Number of pole pairs |
Numerical value | 14kW | 380V | 28A |
Ø When the motor is fully loaded, the maximum output speed reaches 187 rpm;
Ø The output voltage is stable, and the output current waveform is a sine wave.
Inverter selection:
The use of asynchronous motor and rotary encoder to control the spindle motor requires position control and speed control. ES500 inverter is a kind of high-speed motor and electric spindle, variable frequency motor, AC servo motor, various synchronous motors, ordinary asynchronous motors, with torque, speed and position control capabilities. It has good torque and speed control performance to ensure stable mechanical operation, rapid response and small torque ripple. The frequency converter has the following technical characteristics:
A. Starting frequency/starting torque at 0Hz/200%
B. Overload capacity: 150% rated current 60s, 180% rated current 10s, 200% rated current 1s
C. Speed ratio: 1:1000
D. Speed control accuracy: ±0.02% maximum speed, response time<10ms
E. Built-in C3 filter, stronger anti-interference ability
F, with fixed-length control function
G. Position control accuracy: ±1 pulse
Control implementation
For a 15kW multi-stage permanent magnet synchronous motor, fully considering the torque requirements during start-up and operation, a frequency converter can be selected for amplifying the first gear, and the optional model is ES5004T018G. The screw pumping unit needs to meet the requirements of quick start and stop and effective braking, so that the braking unit of the inverter should have a larger braking current to shorten the braking process. Customers can choose the braking unit of DBU-055-4, and the braking resistance is 22Ω/3000W.
Specific use effect
The acquisition of the signal by the whole system is relatively simple, so the wiring is very convenient. ES500 series inverters have excellent performance in vector control, and only simple self-learning can achieve precise control of permanent magnet synchronous motors, which makes the whole debugging process easier.
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