Research For Control Strategy Of Shipboard Grid Connected Inverter

With the increasing exhaustion of traditional fossil energy and the worsening of air pollution and climatic issues, clean and renewable energy development and utilization gets growing concern. In this instance, utilizing clean renewable energy and achieving grid connected on ships will be a new development direction of shipbuilding. Inverter is very important to the grid connected system of new energy, but the application of it on ships is little. So the research on shipboard grid connected inverter is profoundly significant, especially for large ocean ships.In consideration of the characteristics of Shipboard Power System (SPS) which has limited capacity and unstable voltage and frequency, this dissertation conducts research work on the grid connected control strategy of shipboard grid connected inverter. The main contents are as follows:Firstly, the paper analyzes the strengths and weaknesses of different topologies of inverter and its filter, and the topology of them is chosen, then the math model is built in two-phase stationary coordinate system. Besides, in the section of current control, by explaining of the LCL filter’s resonance phenomenon and the comparison of its two rejection methods, this paper proposes a novel control strategy with inverter side inductance voltage feedforward. Grid voltage feedforward method and Proportion Multiresonant controller are proposed to enhance the anti-disturbance system based on the fact that the voltage and frequency are not stable and the SPS contains great deal of harmonics. Furthermore, in the section of grid connection control, the constant power control is chosen to decrease the reactive content in SPS. But the voltage collapse of SPS frequently will lead to the invert overload, so a method that the inverter output reactive power is increased in proportion to the depth of voltage collapse is used to keep the system running steady and support grid voltage. And the Phase Lock Loop based (PLL) on the Second Order Generalized Integrator (SOGI) which has been improved with Low Pass Filter (LPF) is adopted to quickly and accurately lock the grid phase when the grid voltage is unstable and harmonics and unbalanced three-phase voltage exist in SPS.At last, the simulation model of shipboard grid connected inverter is set up in Matlab/Simulink and simulated according to proposed scheme. Simulated results validate the effectiveness of the proposed approach. And this thesis provides reference to the design of shipboard grid connected inverter.