Study On Chaos And Its Control In Parallel Diesel Generators

The mathematical model of parallel diesel generators is non-linear, and under certainexternal interference non-linear system may show chaos oscillation. As a result, in order toimprove the dynamic characteristics of ship power system and ensure the stability andreliability of ship power system, this dissertation will establish the non-linear mathematicalmodel of parallel diesel generators in ship power system, study the non-linear mathematicalmodel of ship power system using chaos theory, obtain the parameter conditions when shippower system is in chaos oscillation, and finally design a chaos controller of ship powersystem for retraining chaos oscillation.First of all, according to the operation characteristics of parallel diesel generators,establish the mathematical model of ship power system. Normally, dual-parallel system is thebasis of multi-parallel system, so establish the mathematical model of dual-parallel dieselgenerators as the mathematical model of ship power system. After reasonable assumptionsand simplifications, taking the transient change process of field winding into account, butignoring the dynamic process of damping winding, establish the third-order model ofsynchronous generator. Furthermore, add voltage and current coupling relationships to themodel, then establish the mathematical model of dual-parallel system.Secondly, add a periodic electromagnetic power disturbance as external interference tothe model of ship powe system, then use Lyapunov indices analysis method as the criterion ofchaotic oscillation to obtain the parameter conditions that poroduce chaos oscillation in shippower system. But as the criterion of chaotic oscillation, Lyapunov indices analysis method isonly a sufficient condition, so need to verify the result with the simulation figures of powerangle, rotor velocity and phase diagram.Third, design nonlinear controller using nonlinear H_∞method. First, linear the non-linearmathematical model of ship power system with direct feedback linearization method. Then,design nonlinear H_∞speed governor and voltage regulator. Finally, add the nonlinear H_∞speedgovernor and voltage regulator into the mathematical model of ship power system and obtainthe speed control system and voltage control system, and then simulate with Matlab softwarethree cases as follows: adding100%load suddenly into a single diesel generator, removing100%load suddenly from a single diesel generator and distributing load in dual-parallel dieselgenerators. Through the dynamic response curves obtaind from simulation, verify thefeasibility of the nonlinear H_∞speed governor and voltage regulator designed before. Finally, under the parameter conditions obtained with Lyapunov indices analysis method,design non-linear chaos controller with nonlinear H_∞method. Add external interference intoship power system and at the same time, add H_∞chaos controller into the system too, andobserve the effect of H_∞chaos controller through the dynamic response curves obtaind fromsimulation to prove that H_∞chaos controller designed before is feasibility.