Research On Power Quality Controller For New Energy Ship Grid

With the world’s massive consumption of fossil fuels and rising global temperatures,the development of new energy sources is an effective way to achieve carbon peaking and carbon neutrality.Distributed Renewable Energy is widely applied on new energy ship grids.However,the new energy ship grid with high penetration rate presents power electronic micro-grid characteristics,causing serious harmonic distortion in the ship grid,leading to a series of problems such as increased active loss of grid equipment,insulation aging of transmission cables,electromagnetic interference and voltage flicker in the grid.Therefore,it is particularly important to improve the power quality of new energy ship grids.This paper takes the new energy ship power grid as the research object,establishes the source-grid-load simulation model of the ship power grid on the MATLAB/Simulink platform,simulates the harmonic characteristics of the new energy grid,and adopts the harmonic detection algorithm of the cascaded active power filter to effectively suppress the harmonics of the new energy ship power grid.The main research elements of this paper are as follows.In this work,to address the problem of serious harmonic pollution in the power grid of new energy vessels.the cascaded multi-level active power filters are used to suppress harmonics on the basis of the analysis of multi-level topologies.However,cascaded multilevel topologies suffer from unbalanced DC-side voltages due to unbalanced module power.Based on the analysis of the intra-phase and inter-phase power characteristics of the modules,a multi-layer power balancing control strategy is proposed for effective control of module power balancing.The simulation results show that the control strategy is effective.For the problems of inaccurate harmonic detection and compensation caused by the pq method and ip-iq method based on the stationary coordinate system because of voltage distortion and asymmetry,an improved dq harmonic detection algorithm based on instantaneous power theory is proposed in this paper.Firstly,a phase-locked loop based on the dual-rotation synchronous coordinate method is used to realize the extraction of the amplitude and phase of the base-wave positive sequence voltage of the grid.Then a coordinate transformation is used to achieve the accurate separation of each component of the load current,so as to accurately extract the harmonic reference components and effectively improve the compensation accuracy.Experimental results show that the algorithm has a fast dynamic response,reaching steady state in just 0.1 seconds.In this paper,a source-grid-load simulation model of a ship’s grid is built on the MATLAB/Simulink platform,using a thyristor rectifier as a non-linear load for simulating the 3rd,5th,7th and 9th harmonic sources of the ship’s grid.The harmonics are suppressed by cascaded multilevel active power filtering,The experimental results show that the 3rd,5th,7th and 9th harmonic content rates of the ship’s grid are reduced from 0.729%,12.95%,4.78%and 1.11%to 0.06%,0.11%,0.055%and 0.048%before suppression,so the harmonic detection algorithm based on cascaded active power filters can effectively suppress harmonics and effectively improve the accuracy and precision of harmonic compensation.