中国では、ビームポンプユニットが様々な油田の主要ポンプ設備として広く使用されていますが、生産量が少なく、エネルギー消費量が多く、大型馬が小型車を牽引するなどの問題を抱えています。近年、パワーエレクトロニクス技術の発展に伴い、周波数変換技術は省エネや周波数調整の利便性などの利点から、油田で広く利用されています。ポンプユニットの運転中、電動モーターは発電状態で運転されることが多いです。
In order to solve the problem of energy backflow, there are currently two main solutions for pumping units in various oil fields in China:
·Variable frequency braking unit and variable frequency feedback unit. Adding a braking unit and a braking resistor to the busbar directly consumes energy on the braking resistor, which is not only detrimental to energy conservation, but also difficult to solve the problems of heat dissipation and lifespan of the braking resistor;
·Parallel feedback units are connected to the busbar to feed back the energy generated by the motor during power generation to the grid, achieving reverse flow between the inverter and the grid. However, this does not solve the problem of low power factor and high harmonic current when energy flows from the grid to the inverter.
In response to the above situation, the four quadrant technology solution can overcome the shortcomings of the two solutions mentioned above. The four quadrant frequency conversion technology solves the problem of regenerative energy processing of pumping units when the system is unbalanced, with four quadrant operation function, while improving energy-saving efficiency, reducing harmonic pollution of the power supply, and improving power factor. The four quadrant frequency converter adopts IGBT rectification technology controlled by PWM, with bidirectional control of rectification and energy feedback. True four quadrant operation can perfectly solve the problem of energy backflow in pumping units.
Introduction to Four Quadrant Frequency Conversion Technology
1、 Principle of Four Quadrant Frequency Converter
The topology of the four quadrant frequency converter circuit, which uses three-phase pulse width modulation (PWM) rectification instead of uncontrolled rectification, is shown in Figure 1. It can convert the mechanical energy of the load into electrical energy and return it to the grid.
Four quadrant frequency converter - energy-saving solution for oilfield pumping units
Figure 1 Topology structure of four quadrant frequency converter circuit
2、 Advantages of Four Quadrant Frequency Converter
Using a high-speed and high computing power rectifier control unit DSP, six high-frequency PWM pulses are generated to control the turn-on and turn off of the IGBT on the rectifier side. The turn-on and turn off of the IGBT work together with the input reactor to produce a sine current waveform that is in phase with the input voltage. This eliminates the harmonics generated by diode rectification and analysis, and the power factor is close to 1, thereby eliminating harmonic pollution to the power grid;
The rectifier side of the four quadrant frequency conversion technology adopts IGBT power modules, which can achieve bidirectional flow of energy between the input grid and the motor. When the system is unbalanced, the potential energy generated by the imbalance can be fed back to the grid, greatly reducing the requirement for system balance;
モータが発電状態にある場合、モータで発電されたエネルギーはインバータ側のダイオードを介してDCバスにフィードバックされます。整流器側のフィードバック制御が開始され、DCをACに変換し、インバータ電圧の位相と振幅を制御することでエネルギーを系統にフィードバックすることで、省エネ効果を実現します。