Research On Parallel System And Control Method Of Photovoltaic Inverter

Under the beautiful vision of "accelerating the formation of green development mode and lifestyle,building carbon neutral,and building a new system of green life",photovoltaic power generation,as one of the three major renewable energy sources,has ushered in an unprecedented development opportunity.With the popularity of various household appliances,and the development of the industry,an increasing demand for alternating current(ac),the traditional single inverter already cannot satisfy people’s basic demand,must be conducted in a single inverter on the basis of innovation,developed to meet the social demand of the new inverter,is this topic research the photovoltaic inverter parallel system.Unlike conventional single inverters,the input and output of the power source can be regulated as required during DC conversion.Obviously,this parallel system is more appropriate for the needs of social development,but what we need to understand is that in the process of power output,if the voltage output of each module cannot be adjusted well to ensure the steadiness of electric energy,once the voltage vector of a certain link exceeds the expected index,the system will be burned down and will be paralyzed,or even there will be a fire.The inverter is the core device in the PV inverter parallel system,and its energy conversion efficiency determines the quality of the whole system.In this article,in the first place,the research status of the system at home and abroad is analyzed,the properties and theories of the system are concisely introduced,followed by the three-phase inverter in the use process are discussed.In this section,we analyzes and tests the principle and performance of solar cells.The voltage chart of simulated batteries under different conditions are obtained.It is known that photovoltaic cells have a unique maximum power point under different factors.For keep the maximum output power of the parallel system,we have to make each part of the system should output the largest power all the time.Based on the conventional perturbation way this paper proposes a maximum power point tracking technology based on dynamic duty cycle perturbation.The simulation chart show that the duty cycle perturbation algorithm can follow the greatest point of the battery system well,and compared with the traditional MPPT algorithm,this way can follow the point of the battery system more rapidly,and under the condition of abrupt variations of ambient,this way can also follow the point rapidly.Moreover,after following the point,the power curve does not produce large fluctuations.In the DQ coordinate system,the double closed ring control system of the three-phase is devised.The control system adopts the voltage outer ring and current inner ring.and the corresponding controller date are obtained of the syetem.In the aspect of circulating current control and power sharing,the traditional method is analyzed first,but this method is controlled under the condition of ignoring the equivalent resistance of the system,for surmount this weakness,the prevailing way is lead into virtual impedance,which can greatly decrease the circulating current of the system.but the addition of virtual impedance will cause the system to produce a lot of pressure drop,influence the stability of the system.Therefore,a virtual impedance adaptive droop control strategy based on active power instantaneous feedback is proposed.Different from the traditional virtual impedance droop control strategy,this method adds the instantaneous feedback of active power,and the system can use the received information of active power to adjust the virtual impedance in real time.In order to verify the feasibility and rationality of the controller designed in this paper and the virtual impedance adaptive droop control strategy based on the instantaneous feedback of active power,a dual inverter parallel system was designed and a simulation model was built and verified.The simulation results show that,The virtual impedance adaptive droop control strategy based on the instantaneous feedback of active power can effectively maintain the stability of the voltage quality of the system,achieve equal power sharing,reduce the circulation generated by the system to a large extent,and improve the safety performance of the parallel photovoltaic inverter system.