Research On Ship Microgrid Operation Control

The energy crisis and environmental pollution are major challenges facing the world at present,and also affect the rapid development of various transportation industries.As an important member of the transportation industry,the shipping industry has received extensive attention from its research on energy conservation and emission reduction.With the development of ship electric propulsion,the ship microgrid has become the core of ship operation,and the research on ship microgrid can greatly promote the development of shiping industry.With the development of power electronic converter technology,the ship's microgrid can be more free to choose DC system,AC system,AC and DC hybrid system.As AC/DC hybrid power system is more economical,space-saving and maneuverable,it is more and more favored by the shipping industry.The access of the battery system improves the flexibility of the ship's microgrid,reduces pollutant emissions,and increased diesel utilization of diesel generators.In this thesis will study the electrical system on a hybrid ferry.The battery is connected to the DC bus via a bidirectional DC/DC converter and provides energy to the drive motor.The two diesel generators are connected to the AC bus and supply power to other loads.A DC/AC converter using LCL filtering is used as a bridge connecting the AC bus and the DC bus.The ferry has three working modes,namely,the diesel engine does not work,the battery alone gives the whole system power supply mode,the battery and the diesel engine jointly give the whole system power supply mode,and the diesel engine separately supplies power to the entire system while charging the battery.The bidirectional DC/DC converter adopts a three-phase interleaved DC/DC circuit.In order to ensure stable DC bus voltage and ensure that the control signal is not saturated at the start of the motor,the bidirectional DC/DC circuit adopts double loop anti-saturation PI control.For the stability problem of bidirectional DC/DC converter with constant power load,the impedance ratio method is used to analyze and select the appropriate capacitance value and controller parameters on the DC bus.In view of the complexity of ship microgrid control,in this thesis uses hierarchical control to control the system.The coordinated control method of diesel generator and battery adopts the droop control method of bidirectional DC/AC converter constant frequency control and QV droop control with virtual impedance.The governor andexciter of diesel generator adopt droop control.In this way,the fuel efficiency of the diesel generator can be improved under the coordinated control,and the reactive power can be shared among different micro sources.Based on the Matlab/Simulink simulation platform,the electrical system model of the hybrid ferry was built,and the correctness and effectiveness of the control strategy of the ferry under different operating modes were verified.