Research On The Stability Of Wind And Solar Power Grid-connected Ship Power Systems

Shipping is the most important mode of transportation in global trade.Introducing distributed power sources such as photovoltaics and wind power into the ship’s power system can effectively alleviate energy crisis and environmental issues,and be more conducive to achieving the strategic goal of "carbon neutrality" by 2060.However,the output power of photovoltaics and wind power has randomness,which may impact the grid system.Therefore,it is crucial to ensure and improve the stability of the grid system.This article establishes models for major components of wind-solar power generation systems,including photovoltaic arrays and their MPPT control,wind turbines and their MPPT control,grid-connected inverters,and diesel generators,laying the foundation for subsequent stability analysis.To improve energy efficiency and practical value of windsolar integration research,a good MPPT control is needed.Due to the complex and changing external factors in offshore sailing work environment,traditional MPPT control algorithms have problems with output power far below theoretical values.The grey wolf intelligent algorithm is applied as the MPPT control algorithm,with non-linear convergence and interval contraction strategy to improve convergence speed and calculation accuracy.Simulation results show that the improved grey wolf algorithm has faster convergence speed and higher convergence accuracy,achieving better photovoltaic maximum power tracking.Considering the integration of distributed power sources such as photovoltaic and wind power,the proportion of synchronous generators in ship power systems has decreased.In addition,MPPT control weakens the output power regulation ability of distributed power sources.These factors lead to a significant reduction in the system’s inertia and damping characteristics,posing a threat to system stability.Therefore,virtual synchronous generator technology is used for converter control to simulate the virtual inertia and damping introduced by synchronous generators into the system.Considering the difficulty in determining values for traditional virtual synchronous generator damping and inertia,a differential module method is proposed to increase system damping without enlarging steady-state power errors,thereby enhancing system stability.An adaptive inertia improvement measure is also proposed to adjust inertia values based on the ideal virtual inertia feedback according to actual system requirements,meeting the demands for system stability.Simulation results demonstrate that these methods can accelerate system frequency adjustment speed,effectively reduce frequency overshoot,and improve system stability.Virtual synchronous generator technology and energy storage have a synergistic effect.Energy storage not only provides inertia for virtual synchronous generators to smooth out power,but also affects the implementation of virtual synchronous generator technology’s inertia,frequency modulation,and other characteristics in terms of capacity density,power density,and other properties.To achieve optimal results with virtual synchronous generator technology,specific applications of energy storage must be considered.Because the inertia characteristics of virtual synchronous generators are closely related to energy storage capacity density and frequency modulation characteristics are closely related to energy storage power density,single energy storage is limited by either capacity or power density,making it difficult to achieve desired effects such as virtual synchronous generator inertia and frequency modulation.Therefore,hybrid energy storage units with both high energy density and high power density are chosen.To enable energy storage to smooth out power and provide inertial support for virtual synchronous generators while enhancing system stability,charge and discharge control of energy storage is necessary.Simulation results show that the total output power of the wind-solar power system remains constant when energy storage is used,buffering fluctuations in power.To improve the implementation and stability of virtual synchronous generator technology,power allocation for energy storage should consider the unique features of different types of energy storage.A power allocation strategy based on virtual LC droop control is proposed because traditional droop controls cannot meet the requirements of good dynamic power sharing due to fixed resistance values.By introducing virtual inductance and capacitance and utilizing their response relationships with frequency,dynamic power allocation is achieved.Simulation results demonstrate that lithium-ion batteries continuously supply power to the system,while supercapacitors have quick response times during transient processes.Good power allocation enables high-capacity density lithium-ion batteries to achieve inertia characteristics and high-power-density supercapacitors to achieve frequency modulation characteristics.The simulation results demonstrate that virtual synchronous generator technology has a faster response to frequency changes,quicker adjustment,and smaller frequency variation,making it more beneficial for system stability.Finally,the ship power system’s stability during wind and solar power grid connection,wind and solar power shutdown,changes in illumination intensity and wind speed,and load changes are analyzed through simulation.The simulation results of parameters such as AC/DC bus voltage and system frequency verify the stability of the wind and solar power grid-connected ship power system,as the frequency and voltage variation ranges of the grid system are within the stable operating range,verifying its stability.The research content of this article has certain practical guidance value and research significance for ensuring and improving the stability of wind and solar power grid-connected ship power systems.