| For remote mountainous areas,pastures,islands and other areas with weak connections to the power grid,the power supply capacity of the power grid is insufficient and the reliability is low.Due to the large scale of investment in grid upgrades,and the effective use of local wind,solar and other renewable energy sources,the construction of a wind-solar diesel-storage microgrid is a highly feasible system technical solution for implementation.How to make better use of the power generation capacity of the microgrid to accept new energy and improve the power quality of the microgrid is an urgent technical problem to be solved.Harmonic resonance,as a power quality problem that can magnify the negative effects of harmonic sources,should be paid enough attention in microgrids.In this paper,the independent microgrid system of wind and diesel storage is the research object,the harmonic resonance characteristics of the microgrid system under different conditions are studied,and the targeted harmonic suppression method is proposed based on the conclusions and characteristics of the analysis.First,perform detailed mathematical modeling of micro-source units such as photovoltaic arrays,wind power generation systems,diesel generators,energy storage systems,etc.inside the micro-grid.According to the different characteristics of each micro-power source,each micro-power source is simulated from different focal points.analysis.The simulation results show that the micro-power sources established in this paper can reflect the actual operating conditions of the micro-power sources and can adapt to the modeling needs of complex microgrid systems.Secondly,conduct in-depth analysis and research on the harmonic sources of the two mainstream power generation systems of photovoltaic power generation and wind power generation in the microgrid system.Based on the photovoltaic array and the doubly-fed wind turbine model built in PSCAD,the microgrid under different operating conditions is analyzed and researched.The harmonic characteristics of the power supply are simulated and analyzed.A simulation model suitable for studying the harmonic characteristics of independent microgrid of wind,solar,diesel and diesel storage was built with reference to a certain non-electrical area,and the effect of micro-power supply connection on the voltage and current harmonics of the micro-grid system was simulated and analyzed from two aspects: the connection location and the number of micro power sources.The influence of distortion rate.According to the characteristics of the non-synchronous machine power inverter cluster in the microgrid,the method of harmonic linearization is adopted,and the current controller,dq axis decoupling,LCL filter and other links are considered,and the influence of the operating point on the output impedance is considered Established positive and negative sequence impedance models for the LCL grid-connected inverter,and built a simulation model based on PSCAD/EMTDC to verify the impedance model in the time domain.On this basis,the equivalent model of the multi-inverter parallel system is derived from the common connection point,the resonance amplification coefficient index is introduced,and the influence of various factors on the resonance of the multi-inverter system is discussed.Finally,aiming at the harmonic characteristics of the microgrid,two suppression methods using dual-tuned filters and deadbeat current prediction active power filters are proposed.Through simulation,a comparative analysis of the harmonic suppression performance of the dual-tuned filter and the active power filter applied to the microgrid is carried out.Taking the current of the micro-power grid connection point as an example,it is verified that the active power filter can be compared with the passive power filter.Real-time compensation for multiple harmonics,better harmonic suppression performance. |
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