| Since the industrial revolution,the application of traditional fossil energy to bring a lot of global environmental pollution and greenhouse effect,and new energy technology as one of the important ways to solve the problems of global environment,to get the world universal favor and recognition,extensive application.Photovoltaic power generation as an important part of new energy power generation technology,the development in the world can be said to be advancing by leaps and bounds,and the application of distributed photovoltaic technology is more common.As more and more distributed PV projects are incorporated into the distribution network to generate electricity,the impact on the power quality and system stability of the distribution network is becoming increasingly prominent.Because of distributed photovoltaic grid is the main form and the development trend of photovoltaic power generation in the future,so the integration on power quality real-time monitoring,analysis of the power quality disturbance caused the principle of distribution network power,to maintain stable operation of the distribution network system,has a strong practical significance.This thesis mainly focuses on the simulation and Research on the influence of distributed PV grid connected to the voltage quality of distribution network.The access of distributed photovoltaic has changed the power supply mode of traditional distribution network with single-phase laying mode.Its output power is stochastic,fluctuating and irreconcilable,and it is easy to cause voltage fluctuation,flicker,overshoot and harmonic pollution in distribution network.This thesis established a distribution network simulation model of distributed photovoltaic customers locally,analysis simulation and mechanism of different power level of fundamental and harmonic voltage,characteristics and trends,found that high power factor,reverse power flow and lead compensation are improved by using terminal voltage.When the power factor is different under the reverse power and the positive power flow,the influence on the voltage stability is different,and the system has the resonance phenomenon at a certain frequency.At the same time of distribution network with distributed photovoltaic power simulation,found that access to distributed PV will cause periodic fluctuation of low voltage line into rectangular pulse total power factor,causing the reactive power compensation device in the form of frequent action,inrush current capacitor circuit has been put into operation,it will produce a fuse fused.The power quality improvement measures of distribution network side and photovoltaic system side are put forward,and their advantages and disadvantages are analyzed.The three optimization strategies of reactive power control,active power prediction limit control,active power and reactive power comprehensive control are put forward.Through comparative study,the rationality and limitations of the three schemes are analyzed.It is found that the active power and reactive power integrated control strategy,that is,using reactive power of the inverter to regulate reactive power and voltage,and reduce unnecessary power cuts,is the most effective way to improve power quality.Finally,combined with specific cases,we put forward the access schemes of all kinds of distributed PV projects connected to the grid,compare the similarities and differences and applicability,and summarize the most ideal access scheme. |
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