Torsional torque suppression of decentralized generators using H∞ observer

Electric utility deregulation has made it possible for power producers and suppliers (PPSs) to enter the electricity market in Japan. PPSs are supposed to achieve 30-minute balancing control for stable supply of electrical power, in which energy demand and energy supply should be matched within thirty minutes. Meanwhile, load rejection and instantaneous voltage drop greatly affect turbine shafting, that is, torsional torque oscillation. Therefore, PPSs have to consider the reduction of torsional torque to prevent generator shaft damage. However, observation of torsional torque is technically difficult. Thus, this paper proposes an observation system for torsional torque based on H_infin theory. This work also introduces a control system that achieves both the 30-minute balancing control as well as reduction in torsional torque by use of an H_infin observer for the shaft torque. The effectiveness of the proposed control system is verified by using MATLAB.