Impedance Modeling And Grid Connection Stability Analysis Of Synchronverter

With the increase of power grid permeability,the inertia and damping of the whole power system are relatively reduced,and the difficulty of frequency regulation and voltage regulation of the power grid is increased,bringing a series of brand-new impacts and challenges to the safe and stable operation of the power system.Synchronverter is a voltage source inverter that can simulate the external characteristics of synchronous generator and has good grid adaptability.However,due to the remote location of distributed power generation system,the long distance transmission lines and a large number of series compensation devices will bring an equivalent impedance to the power grid,it is easily interact with the grid-connected devices to cause harmonic oscillation which can undermine the power quality and system stability,impedance analysis is a convenient and effective method of stability analysis.The thesis first uses the method of harmonic linearization to derive the positive and negative sequence impedance model of LC-filter-based three-phase synchronverter,and proves the stability advantage of the synchronverter under the condition of normal weak grid.On this basis,the influence of four loop parameters on the impedance model is analyzed.The possible situation of series compensating power grid and synchronous inverter resonance is studied,parameter adjustment is adopted to suppress the system interaction oscillation and increase system phase margin.Finally,the stability of the simple interconnected system consisting of synchronverter and grid-connected inverter is explored by impedance analysis method.The paper verifies the correctness of the proposed impedance model by simulation and experiment;The good adaptability of the synchronverter under weak grid isverified by experiments;The stability of the series compensation system is verified by RTlab hardware in-loop experimental platform.