Lifetime Constraint Control Strategy Of PV Inverter Considering The Influence Of Capacity Ratio And Power Limit

With the changing situation of the energy industry and the rapid development of renewable energy,it is expected that by 2025,the power generation capacity of renewable energy will exceed that of coal power and become the largest power source in the world,accounting for one third of the world’s total power generation,solar power generation accounts for 60% of the newly installed capacity of renewable energy and wind energy accounts for 30%.As the key link of renewable energy grid connection,the lifetime and reliability of PV inverter have attracted extensive attention.In order to solve the probl ems of high cost and low reliability of photovoltaic power generation,it is of great significance to realize the accurate evaluation and constraint control of the lifetime of PV inverter.Therefore,this paper proposes a lifetime evaluation method of PV inverter considering the influence of fundamental frequency / low frequency junction temperature,establishes a lifetime constraint control strategy of PV inverter considering the influence of capacitance ratio and power limit,and carries out verification and analysis.The main contents of this paper are as follows:Firstly,the influence mechanism of capacity ratio configuration and power limit on the output of PV system is revealed.Based on the relationship between PV output and thermal stress,the influence of capacity ratio and power limit on the lifetime damage of PV inverter is comprehensively analyzed.Then,the electrothermal model and lifetime model of IGBT and capacitor in PV inverter are established,the influence mechanism of fundamental frequen cy /low frequency junction temperature on the lifetime damage of PV inverter is revealed,the lifetime evaluation method of PV inverter considering the influence of fundamental frequency / low frequency junction temperature is proposed,and the importance of fundamental frequency / low frequency junction temperature in the lifetime evaluation of PV inverter is analyzed.Taking different latitudes as examples,The effects of different mission profiles and different sampling periods on the lifetime damage of PV inverter are compared.Then,the lifetime constraint control strategy of PV inverter considering the influence of capacity ratio and power limit is proposed.Using the variable power tracking control method of PV inverter,the flexible adjustment of power limit of PV system is realized.Combined with the lifetime evaluation method of PV inverter,Taking a practical example,the lifetime constraint control results of PV inverter under the conditions of simply changing the capacity ratio or power limit and comprehensively considering the capacity ratio and power limit are analyzed.The lifetime conditions of PV inverter before and after using the lifetime constraint control strategy are compared and analyzed,the feasibility of the life time constraint control strategy is verified,and the capacity ratio and power limit meeting the lifetime requirements are selected.Finally,the concept of net additional power generation of PV system is proposed,and the selected capacity ratio and power limit are set to fu rther reduce the cost of PV system,which provides a theoretical basis for the capacity ratio configuration of PV station and the control parameter setting of PV inverter.