Autonomous Decentralized Control Strategy of Reactive Current Proportional Factor of Grid Fault for String Photovoltaic Inverters

With the development of photovoltaic (PV) power generation technology, string PV inverters have gradually occupied a large part of the PV inverter market in recent years. For string PV power plants, unlike centralized PV power plants that can be simply equated to a single unit, the transient response of multiple units within them is decentralized and less researched. This paper firstly introduces the grid fault reactive current proportionality factor(RCPF) of string PV inverters applied to different scenarios. Then, taking the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K_{1}$</tex>, which is the RCPF applied to voltage drop scenarios caused by symmetrical faults as an example, the paper analyzes the influence of grid strength and prefault active output of the unit, and get the trend of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K_{1}$</tex> when the grid strength and pre-fault active output of the unit change The comprehensive analysis of the influencing factors gives the objective function to determine the value of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K_{1}$</tex>, and taking into account the two problems encountered in engineering practice: the dispersion and mutual influence of multiple units and the possible lack of unit arithmetic power, this paper also gives the corresponding solution after corresponding analysis. Finally, through a string PV plant example, the specific calculation process and results are introduced. From the results, it can be seen that the value of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K_{1}$</tex> is in line with the aforementioned analysis of the grid strength and the influence of the active output of the unit before the fault, which verifies the validity of the objective function. The same analytical idea can be generalized to other RCPF applied to asymmetrical faults and high-voltage faults scenarios.