Virtual Synchronous Generator Control Of Ship Distributed Energy Under Shore-to-Ship Power Supply

The ship adopts shore-to-ship power supply through disconnection,which lead to a power outage throughout the entire vessel and waste valuable manpower and resources.As an auxiliary electric source for ships,distributed energy improve the stability and reliability of power supply during berthing periods,enabling uninterrupted power supply to shiploads.Compared to onshore microgrids,ship microgrids are independent power systems with limited capacity and susceptible to load fluctuations.Additionally,ship microgrid electrical systems have high power density and diverse energy sources,demanding high power density from microgrid power generation.Therefore,studying distributed energy control under shore-to-ship power has significant theoretical and engineering practical significance.The paper mainly focuses on ship distributed energy inverters and utilizes a model-free adaptive control(MFAC)algorithm as the research foundation,deeply studying virtual synchronous generator(VSG)control,and designing a ship microgrid inverter control system under shore-toship power.To optimize the output power of ship photovoltaic systems,a maximum power point tracking control method is studied based on model-free adaptive control.This study aims to address power optimization control,frequency control,and grid presynchronization control for distributed energy systems on ships,particularly when connected to shore-to-ship power supply.Specific research content includes:(1)For the optimization of the output power of ship photovoltaic systems during port stay,a maximum power point tracking(MPPT)of merchant marine photovoltaic system based on MFAC is proposed.This method fully considers the time-varying model parameters of the PV system caused by complex weather,ship roll,and sea salt crystallization.The method designs an MPPT controller for photovoltaic systems based on the input and output data to obtain control signals for the boost circuit.The convergence and simulation analysis verify that the method can not only accelerate the control response speed but also improve the accuracy of MPPT.(2)To address the frequency deviation caused by the switching of in the off-grid mode of microgrid inverters under ship-to-shore power.A secondary frequency modulation control of ship microgrid based on MFAC is proposed.The method designs a model-free adaptive controller based on the rotor discretization equation data model of VSG,and the radial basis neural network observer is utilized to observe the nonlinear term including the ship load disturbance.Based on MFAC algorithm,the VSG control is designed to achieve adaptive adjustment of secondary frequency parameters,dynamically adjusting the virtual input mechanical power of the VSG to achieve secondary frequency control without deviation for the ship microgrid.(3)To achieve the smooth transition of the shipboard microgrid inverter under shore power supply,and fully consider the drawbacks of traditional pre-synchronization control such as poor control accuracy and long transition time,a ship microgrid presynchronization control method is proposed.This method calculates the virtual power based on the inverter voltage component and further designs a virtual power model-free adaptive controller to obtain the compensating frequency and compensating voltage amplitude,which are respectively introduced into the power-frequency controller and excitation controller of VSG,thus achieving the synchronization of the distributed inverter output voltage and low-voltage shore-to-ship power.The effectiveness and superiority of the proposed control method are verified through simulation.(4)To address frequency deviation during microgrid pre-synchronization control of ships during port operations,the paper proposes an intelligent self-learning control method for ship microgrid pre-synchronization.This method utilizes a phase difference data model between the ship microgrid and the low-voltage shore power to design an intelligent self-learning VSG pre-synchronization control algorithm.The adaptive adjustment of the VSG power-frequency droop coefficient during the presynchronization process is utilized to avoid the frequency deviation exceeding the limit of the ship microgrid output frequency.Simulation experiments verify that the proposed control method can achieve rapid and smooth grid-connection of the ship’s microgrid while ensuring the normal and stable operation of the ship’s local asynchronous motor load.