Study Of Buffering Performance In Quick Closing Of Servomotor With External Buffer Structure And Designing Of Test Platform

Steam turbine is a large prime mover equipment which is used todrive the generator to generate electricity by transforming the steam heatenergy into kinetic energy of rotating machinery. Due to the complexityand dynamic performance of power grid, It’s a high demand of safety ofsteam turbine. So in order to ensure safety and stable operation of turbine,an acurate control system is necessary. With the development of controltheory and computer technology, turbine digital electro-hydraulic controlsystem (DEH) is used increasingly wide in the field of regulation andcontrolling of turbine system. DEH system is composed of complexhydraulic systems, electromechanical control systems and othercomponents, and the executive component in DEH system is theservomotor. We can see，the performance of servomotor has a significantimpact to the accuracy, vagility and quickness of the steam turbine controlsystem. Especially in order to guarantee the turbine load rejection withgood dynamic performance, it is required to close the servomotor asquickly as possible at the necessary time.Basing on this point, unilateral servomotor is used increasingly in thedesign of the structure of servomotor. The unilateral servomotor drives thevalve closed by a huge spring. The piston will return to zero motive veryquickly under the great force of spring. Therefore, without any bufferingdevices, the valve would hit the door wall heavily. It is easy to causedamage to valves and equipment or even an accident. So, the security inthe closing of servomotor is another issue to resolved and guaranteed.Apparently, here is the emergence of a contradiction, that is how to makethe servomotor close with the fastest speed while the least terminalvelocity when shutdown the valves. To resolve the conflict, the best way is to study and design the buffer performance of the servomotor in theprocess of fast closing. So that, we can identify how various designparameters affect the buffering performance of the servomotor. It willprovide us the data and recommendation of servomotor designing to designthe optimal structure of the new servomotor, certainly it is a good way tosolve the contradiction.Basing on the current general design of the hydraulic buffer structureand the existing servomotor buffering device, the thesis will focus on thestudy of external buffering process of the servomotor, and building up themathematical model of single-level and multi-level buffering structure ofthe servomotor to identify the impact of structural parameters andenvironmental parameters to servomotor fast closing buffering properties.And then, we design an appropriate servomotor test platform to measuresome parameters such as delay time, closing time, terminal velocity, thebuffer chamber pressure. And moreover, we will study the effect ofdifferent parameters on the fast closing buffering performance by changingthe values of different parameters, and verifying the rationality andfeasibility of the simulation results by comparing the model analysis withthe experiment results.After verifying the correctness of the model, we can analysize theimpact of how other structural and environmental parameters to fastclosing buffering performance of servomotor. These conclusions can beapplied to design the servomotor structure and component selection andsite conditions by providing a theoretical basis and data supportcontrolling.