Research On High Frequency Resonance Phenomenon Of Independent Microgrid Of Photovoltaic And Storage,Diesel Based On Impedance Model

In recent years,problems such as energy shortages and environmental pollution have become increasingly prominent.The development of distributed energy generation represented by new energy has become a key research topic for humans to solve energy and env ironmental problems.Microgrid is an organizational structure that can give full play to the value of distributed generation The form is mainly composed of new energy,energy storage equipment and traditional generator sets.Due to cost,terrain and other factors,the large power grid cannot be extended to remote areas and isolated islands.The construction of independent microgrids can solve the problem of electricity consumption in these areas.However,independent microgrids not only lack the support of large power grids,but also have a large number of power electronic converters.Making the independent microgrid highly prone to high-frequency oscillations between sources and loads,which seriously threatens the safe and stable operation of the system.T his paper will analyze this problem from the perspective of impedance.The research object of this paper is the photovoltaic and storage,diesel independent microgrid.In the modeling process,the impedance model of the three-phase converter is first established.Assuming that the three-phase converter works in the inverter mode,its open-loop small-signal model is obtained through small-signal analysis,and then a single-current closed-loop control is introduced to obtain the closed-loop impedance model of the three-phase converter,and the model is used to analyze the impedance change trend of three-phase converters connected in parallel.Then this paper introduces the composition and working principle of diesel synchronous generator,and proved the equivalence of synchronous generator and inverter.The diesel synchronous generator is divided into three parts: the stator armature circuit,the excitation system,and the speed control system for modeling.During the modeling process,the inertia is introduced into the speed control system model,and the impedance model of diesel synchronous generator is obtained by integrating the three parts,and the effect of diesel synchronous generator capacity on the impedance of diesel synchronous generator is analyzed using this model.The impedance model of the photovoltaic and storage/diesel independent microgrid with different loads(resistive load and rectifier load)is established using the obtained impedance model of the three-phase converter and the diesel synchronous generator.Using Matlab to obtain its generalized Nyquist curve when accessing different capacity loads and photovoltaic and storage units,the potential resonance problems in the photovoltaic and storage,diesel independent microgrid are analyzed,and the corresponding independent microgrid is built using RTDS The simulation verified the analysis results.Finally,a hardware-in-the-loop test platform based on RTDS and LAUNCHXL-F28377 S development board was built,which further verified the correctness of the theoretical analysis in this paper.