Study Of Ultracapicator-Based Power Compensation And Energy Recovery System For Mine Lifting Equipment

The power grid capacity of oil field is usually weak in China, electric workover rig cannot work in the rated point if we use the power grid as the single energy source, this situation will lead to poor efficiency of workover rig. Based on the XJ250electric workover rig, a power compensation system used Ultracapacitor is developed, which can compensate the shortage of power grid in oil field, make the XJ250electric workover rig work properly in the same situation of traditional workover rig, and absorb the braking energy of the workover rig.The paper anlayses the working condition of workover rig firstly, and obtain the working sequence and the demand of energy and power level. Then propose the power compensation solution based on Ultracapacitor enegy storage system. On the basic of principle analysis of Ultracapacitor, the paper disscuss the equivalent circuit model of Ultracapacitor. and finished the study of capacity sizing of Ultrapacitor power compensation system.In order to study the control method of Ultacapacitor power compensation system,the paper derives the small signal model based state average method. Then the design of voltage and current loop is finished. Considering the actual working condition and no-load voltage fluctuation, the paper proposes the control strategy based on the speed of motor and dynamic voltage threshold:if the motor speed n<nCH (the threshold of motor speed) and the bus voltage Udc>UCH (the threshold of charge), then the system will work in the energy storage mode; if the motor speed n>nCH and the bus voltage Udc<UDCH (the threshold of discharge), the system will work in the mode of power compensation. Considering the fluctuation of power grid, the thresholds of charge and discharge will be adjusted by the subtraction of no-load voltage and the threshold difference of charge or discharge. This control strategy makes the system working under the rated condition and the feasibility is verified through simulation.In the end, the paper developes the80kW Ultracapacitor power compensation system applied to the XJ250electirc workover rig including design of main circuit control circuit、communication and monitor system、software program. The reliability and stability of the prototype is verified through the assessment experiment in Henan Zhongyuan oilfied, meanwhile,the control strategy based on the speed of motor and dynamic threshold in the paper is verified too.