Study On The Stability Of Electric Propulsion Ship Power System

The electric propulsion system is gradually applied to modern merchant ships due to its advantages of flexible operation,good economy and high safety.However,the use of high-power electrical equipment and a large number of electronic components will make the system structure more and more complicated.At the same time,the load change of the high-power equipment will impact the power grid,the harmonics generated by the electronic components will interfere with the normal operation of the electrical equipment,and the complex system structure is prone to failure in the harsh working environment.Therefore,in order to improve the safety and control performance of ship operation,this paper takes the power system of the electric propulsion ship as the research object,and studies the stability of the power system from the aspects of equipment reliability,grid harmonics and typical disturbances.First,build a model of electric propulsion ship power system including diesel synchronous generator set and asynchronous motor vector control system,and use particle swarm optimization algorithm to optimally configure the control parameters of diesel engine governor.In order to reduce the reliability of the speed sensor in the harsh working environment,a model reference adaptive speed identification device based on the rotor flux linkage is used to estimate the motor speed.In order to improve the speed identification accuracy of the device,a single neuron PI controller is proposed as the adaptive mechanism of the model reference adaptive system to realize the online self-tuning of the control parameters.The simulation results show that the non-speed sensor using a single neuron PI controller has good speed estimation accuracy.In order to study the influence of harmonics on the power system stability of electric propulsion ships,the equivalent power network model of harmonic analysis is established,and the harmonic current is analyzed by fast Fourier analysis method.Aiming at the problem of system stability reduction caused by excessive harmonic content in power system,this paper analyzes the multi-phase rectification technology and active power filtering technology,and proposes to use parallel active power filtering device to suppress the harmonics of the power grid.The simulation results show that the parallel active power filter device has a good harmonic suppression effect and plays an important role in improving the stability of the system under the influence of harmonics.In order to analyze the dynamic response process and transient stability performance of the power system under large disturbances,according to the electric propulsion ship power system model,this paper conducts simulation tests under three typical disturbances of load shock,three-phase short circuit fault,and generator unit trip fault,and the stability criteria such as instantaneous regulation rate,stability time,static and dynamic voltage regulation rate are used to analyze the simulation results.Simulation results show that the built power system can maintain good stability performance under large disturbances.