液化天然气船舶动力系统加速性能优化策略研究

Optimizing Strategies for Accelerating Performance of LNG Power System

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

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

摘要:

针对船舶天然气发动机匹配定距桨（FPP）的直接推进动力系统存在加速速率慢、动态性能差的缺陷，提出了一种系统级优化方案，设计并联型式气电混合动力系统，通过轴带电机辅助推进优化系统的加速性能。建立船舶气电混合动力系统仿真模型，根据试验数据对天然气发动机的加速性能进行数据标定，保证模型动态精度，以仿真手段分别验证混合动力系统使用变频器（VFD）动态切换策略和变频器超前控制策略的加速优化效果。综合考虑实际工程控制难度和加速过程优化效果，变频器动态切换策略优于变频器超前控制策略。气电混合动力系统轴带电机辅助推进（PTI）模式使用变频器切换控制策略可达到较好的加速性能，在降低主机机械负荷和热力负荷的同时船舶快速性最大提升16%。气电混合动力系统轴带电机辅助发电（PTO）模式加速时轴带发电机负载转移至船舶辅机，稳定一段时间后切换至电动模式助推，加速性能可达到PTI模式加速水平。

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.