Simulation Study On Energy Management Strategy For Hybrid Power Ship

With the demands of more stringent fuel consumption and emission regulations,the application of high efficiency-clean power system for ships is growing rapidly.Hybrid power system has become one of the most promising power structures because of its practicability,environmental adaptability,remarkable energy saving and emission reduction effect.This paper focuses on the development of hybrid power system for a series hybrid power water-quality-monitoring ship.Firstly,according to the modular modeling methodology,the transient dynamics model of ship,the dynamic model of permanent magnet synchronous motor(PMSM),the steady state model of diesel generator set and the lithium-ion battery model are established using Simulink.Then,starting from the PWM modulation principle of three-phase voltage source inverter,the characteristics of sinusoidal PWM technique(SPWM),third harmonic injection PWM technique(THIPWM)and space vector pulse width modulation technique(SVPWM)are compared.The closed-loop control system of PMSM based on the field oriented vector control algorithm is determined.To sum up,the modeling of hybrid power propulsion system is completed.Secondly,according to the operating condition and working characteristics of water-quality-monitoring-ship,the energy management strategy based on the definite rules is designed.Aimed at reducing fuel consumption rate and NO_x emission,the weight coefficientis introduced in this paper.The characteristics of engine operating point,operation mode and SOC are studied when the values ofare 0,0.8,0.9 and 1 respectively.Taking the traditional diesel engine propulsion system as a comparison,both fuel consumption and NO_x emission characteristics under driving cycle are analyzed.The results show that the definite rules strategy with differentωvalues can effectively reduce the fuel consumption by 38.54%～41.72%.But the conditions of=1 and=0.9 are unable to achieve the goal of low emission because the operating points of engine locate in the high NO_x emission area;the NO_x emissions of=0.8 and=0 are reduced by 5.94%and 24.50%respectively.Finally,the energy management strategy based on dynamic programming is designed,in which,SOC is designed as the state variable;engine power is designed as the decision variable;minimum fuel consumption rate is designed as the cost function;and the model simulation is carried out under the same driving cycle.Compared with the energy management strategy based on the definite rules(=1),the characteristics of the dynamic programming algorithm are analyzed,such as ship speed following,the working-state and working-time of the engine,SOC trend and so on.The simulation results show that the diesel engine based on the dynamic programming algorithm runs in the middle and high load area,and the operating conditions are comparatively stable.The final SOC of the two strategies are almost the same.The total energy consumption and fuel consumption based on dynamic programming strategy are minimum respectively:the energy consumption reduces by 4.33%compared with the strategy based on the definite rules,and reduces by 24.48%compared with the traditional diesel engine propulsion.However,because higher NO_x emission presents in the middle and high load,NO_xemission based on dynamic programming strategy is the highest.