| The development of human society is inseparable from energy.However,limited primary energy cannot meet the fundamental needs of the growing development of human society.Energy shortage has become a fundamental factor restricting the development of human society.Therefore,the development and application of new energy has become the main driving force for the sustainable development of society.As one of the most important renewable energy sources,solar energy has an irreplaceable advantage over other forms of energy,and its development and utilization technology has also been widely developed.The power supply in the photovoltaic microgrid system is mainly based on photovoltaic power supply,which also contains other auxiliary power sources.Due to the clean,pollution-free,renewable characteristics of solar energy and the flexibility of the microgrid system structure itself,the photovoltaic microgrid is related.The technology is widely studied and applied in practice.The access of a large number of power electronic components and non-linear loads in the photovoltaic microgrid causes problems such as grid voltage fluctuations,flicker,and waveform distortion and voltage deviation caused by harmonics in the power system.At the same time,photovoltaic power generation itself has intermittent,Characteristics such as randomness and volatility cannot guarantee the power quality of the power system in line with national requirements.Based on the above problems,this paper mainly analyzes and discusses the three aspects of photovoltaic power generation system maximum power point tracking(MPPT),inverter grid-connected control and harmonic control.The main research contents of paper are as follows:(1)Maximum Power Point Tracking(MPPT)optimization for PV arrays under local shadows.The MPPT of photovoltaic array is an important part of the control of photovoltaic power generation system,and it is also one of the main factors causing the voltage flicker and fluctuation of microgrid.Firstly,according to the mathematical model and physical characteristics of photovoltaic cells,the output characteristics of photovoltaic arrays under local shadows are discussed,and the reasons for the multiple peaks of PV array output waveforms under local shadows are analyzed.Secondly,the traditional particle swarm optimization algorithm is studied and analyzed,and the traditional conductance increment method is improved.A fuzzy control conductance increment method is proposed,and the improved conductance increment method and traditional particle swarm optimization are proposed.The algorithm combines and uses a hybrid algorithm to track and control the maximum power output of the PV array to improve tracking efficiency.Finally,the MATLAB/Simulink software platform is used to build the PV array power generation system model,the traditional particle swarm optimization algorithm model and the improved conductivity incremental method model.The simulation results show that the maximum power tracking efficiency is higher by the hybrid control method.(2)The photovoltaic microgrid system contains a large number of power electronic devices,especially with the increase of non-linear loads,causing a large amount of harmonic pollution after the system is connected to the grid.By analyzing the active filter(APF)and study the advantages and disadvantages of a conventional passive LC filter,and on the basis of both the composition of the mixed series active filter(LCL-APF),the LCL-APF parallel nuanced.The LCL-APF is connected in parallel to the load circuit of the microgrid system,and the purpose of suppressing harmonics is achieved by means of reverse compensation of harmonic current.The simulation results of the system simulation model show that LCL-APF has better harmonic compensation effect than the separate APF and LC filters.The harmonic content in the photovoltaic microgrid is significantly reduced,so that the output voltage and current waveform q The harmonic content in the photovoltaic microgrid is significantly reduced,so that the output voltage and current waveform quality of the microgrid meet the network requirements,and the power quality of the microgrid system is significantly improved.(3)According to the basic structure of photovoltaic microgrid,the traditional control method PQ control method and V/f control method of microgrid grid-connected inverter are analyzed and analyzed.In addition,the influence of different operation modes on the grid-connected operation of microgrid is discussed.On this basis,the composite control strategy is used to control the grid-connected inverter.The system simulation model is built by MATLAB/Simulink software to verify the composite control strategy.The results show that the strategy can ensure the stable operation of the system and effectively reduce it.System power oscillations ensure system voltage stability,which improves system power quality. |
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