Research On Control Strategy Of H-Bridge Cascade High-voltage Shore Power Supply

With the continuous development of international trade,more and more foreign ships are mooring to China's ports.At the same time,the use of diesel generators to generate electricity will cause serious environmental pollution problems.More and more countries pay attention to the environmental pollution problems caused by ships during port call,and seeking port energy-saving and emission-reduction solutions has become the top priority of all terminals.Under this background,ship shore power technology came into being.Shore power is divided into two types: low-voltage shore power and high-voltage shore power.However,when low-voltage shore power is applied to high-power ships,there are problems such as large number of wiring cables,long wiring distance,and complicated wiring process.With the continuous expansion of trade,foreign high-voltage and high-power ships have become the "main force" of the shipping industry.Therefore,high-voltage shore power supply has high promotion value.This paper is dedicated to the research of 6.6k V / 60 Hz high-voltage shore power system.This thesis,based on the research of the control strategy of the high voltage ship power supply,its main circuit topology and modulation method are designed and selected,and different control strategies are designed for the shore power inverter under off-grid and grid-connected conditions respectively,so as to convert China's 10 k V / 50 Hz AC power system to foreign ships' 6.6k V / 60 Hz power system.The H-bridge cascaded multilevel converter topology is selected as the main circuit structure of high-voltage shore power,and the unipolar frequency-doubled carrier phase shift modulation with better harmonic elimination performance is selected as its modulation strategy.For the shore power supply under off-grid conditions,a dual closed-loop control strategy based on feedforward decoupling is adopted.Through the establishment of model,coordinate conversion,feedforward decoupling and the regulator parameters are designed to achieve the purpose of providing good power quality for 6.6k V / 60 Hz ships.For the shore power supply under grid-connected conditions,on the basis of analyzing the factors affecting the stability of the seamless connection of ship and shore power,a shore power presynchronization controller is designed to suppress the grid-connected inrush current,and the virtual synchronous generator(VSG)technology connected to the microgrid inverter is used to simulate the output characteristics of the diesel generator,to enhance its rigidity,to make up for the lack of traditional droop-controlled shore power,to realize a safe and stable seamless grid connection process.Finally,on the basis of modeling and simulation of marine diesel generators,according to the relevant national standards,the accuracy and effectiveness of the shore power supply control strategy under off-grid and on-grid operating conditions were verified under MATLAB / Simulink environment respectively.What's more,the semiphysical low-power experimental platform based on d SPACE was established to verify the practicability of its control strategy under off-grid conditions,which provided theoretical support for the future marketization of high-voltage shore power supply.