关键词: 船舶动力系统;气电混合;天然气发动机;动态特性;加速策略

Abstract: The target vessel power system uses LNG engine to match the fixed-pitch direct propulsion system. Aiming at the defects of slow system acceleration and poor dynamic performance， a system-level optimization scheme is proposed. The parallel type gas-electric hybrid power system is designed， it optimizes the system acceleration performance through the auxiliary propulsion of shaft motor. A simulation model of gas-electric hybrid system is established， calibrating the acceleration performance of the LNG engine according to the test data to ensure the dynamic accuracy of the model， and verify the acceleration optimization effect of the hybrid power system using the VFD （Variable-frequency drive） switch control strategy and the VFD ahead control strategy one by one. Taking into account the actual engineering control difficulty and the acceleration process optimization effect， the VFD switch control strategy is superior to the VFD ahead control strategy. The Power Take In （PTI） mode of the gas-electric hybrid power system can achieve better acceleration performance by using the VFD switch control strategy， while reducing the mechanical load and thermal load of the main engine and increasing the vessel speed by up to 16%.When system in the Power Take Out （PTO） mode to accelerate， the load of the shaft generator is transferred to the generator sets. After a period of stability， shaft motor switches to the electric mode to assist， and the acceleration performance can reach the acceleration level of the PTI mode.

Key words: Ship power system;Gas-electric hybrid;LNG engine;Dynamic performance;Acceleration strategy