Research On Speed Control System Of Diesel Generator Based On Variable Moment Of Inertia And H_? Robust Control Theory

The power supply system of diesel generators is an isolated grid.Sudden loading and unloading will lead to fluctuation of the engine speed and exert an impact on the power supply quality.The improvement of the control algorithm can improve the response performance of the speed controller,but the space to improve the performance of speed control system by optimizing control algorithm is limited by the inherent characteristics of the diesel generator and the inertia and friction of the speed actuator.The variable inertia flywheel changes the moment of inertia of the diesel generator when the load changes.Therefore,the variable inertia flywheel can improve the transient characteristics of the speed when the load of the diesel generator changes,but it cannot change the steady-state error of the speed control system.The load disturbance is random and the parameter uncertainties will caused by the model error of the speed control system and the variable inertia flywheel.The robust control method can improve the load disturbance rejection performance of the system with Parameter perturbation,but the controller designed only by robust control method has a problem that the order is too high to be easily realized.Combining the variable inertia flywheel with the robust controller can reduce the order of the robust controller while achieving satisfactory system performance.In order to improve the speed stability of the diesel generator under load impact,this paper proposes a variable inertia flywheel.By analyzing the force of the flywheel mass,the differential equation of the mass block is derived,and the differential equation is linearized and developed the mass block control system model.Through the simplification of the control block diagram,the linear time-invariant speed control system of the diesel generator with variable inertia flywheel is derived.The performance of the variable inertia flywheel on the speed control system is analyzed in the frequency domain.The influence of the zero-pole position response performance of the speed control system by the application of variable inertia flywheel and parameter changing is analyzed,and the disturbance rejection performance is analyzed.Considering the modeling error and parameter perturbation caused by approximate linearization and the randomness of load disturbance,the parameter perturbation model of speed control system with variable inertia flywheel is established,and the perturbation of parameters is analyzed.Finally,the design of the H? robust controller was carried out.The influence of the variable inertia flywheel and the robust controller on the performance of speed control system is analyzed by the linear time-invariant speed control system model.The simulation results shows that when the diesel engine output torque and load are unbalanced,the variable inertia flywheel can store and release energy to maintain the balance of system energy and make the speed change smoother.Since the fluctuation ofthe load is often unpredictable and has a certain randomness,the variable inertia flywheel compensates for the change of the load with the change of the kinetic energy of the flywheel,and realizes the change of the diesel engine speed when the load changes.The analysis in the frequency domain shows that the variable inertia flywheel reduces the peak magnitude and bandwidth of the speed control system,which proves that the variable inertia flywheel improves the transient characteristics of the speed control system.The robust controller makes the speed control system get better stability and faster response under the condition of system parameter perturbation and external disturbance.Since the variable inertia flywheel can change the inherent characteristics of the generator,combining the robust control method with the variable inertia flywheel avoids the problem that only robust control is not easy to realize due to the high order of the controller.