## 1 Introduction  
PV (Photovoltaic) systems are largely divided into PV arrays that produce DC (Direct current) power and PV inverters that convert the generated DC power into AC (Alternating current) power. An PV array is a structure in which PV modules are connected in a series, and many such strings are connected in parallel. The maximum number of PV modules in a string connected in a series is usually below the system voltage of 1500 V, depending on the PV plant capacity and the input voltage of the PV inverter. In PV plants with a large installation area, the voltage mismatch of strings is caused by various factors, which may change the performance of the PV system. The PV plant with a centralized-type inverter consists of multiple PV strings, and the performance of the PV system is determined by the sum of the performance of the multiple strings. Therefore, differences in the performance of PV arrays or strings reduce the performance of the PV system, which is referred to as a mismatch loss due to the parallel connection of PV strings. According to the research results, the mismatch factors of PV arrays, such as PV module mismatching and partial shading, reduce the output of the PV system by about 20-25% [1]. Output mismatch causes a considerable loss for the PV system, and various studies have been conducted to remedy it. The most common factor of output mismatch is partial shading. In partial shading, the operation of bypass diodes changes the power-voltage curve of each array, reducing the output. Various studies with the aim of remedying these problems have been conducted to estimate and analyze the performance of PV arrays using a simulation tool or an experiment [2; 3]. Research was also conducted to minimize output mismatch by improving the arrangement of PV arrays. Using the suggested arrangement of PV arrays, the efficiency of the output power improved by up to 4% under partial shading [4]. The recent research result released an odd-even structure that improved on various array arrangement methods [5]. PV inverters perform MPPT (Maximum Power Point Tracking) on the entire input strings to optimize the output under various environmental conditions. However, in the case of output mismatch, such as partial shading, the P&O or IncCond method, which is used as a general MPPT method, does not perform an optimal MPPT, resulting in output loss. In partial shading, the research result of applying the DMPPT (Distributed Maximum Power Point Tracking), which improved the existing MPPT, has been published [6]. Additionally, the RMPPT (Real Maximum Power Point Tracking) method was developed with 15% less output reduction than the IncCond method [7]. A study was conducted to confirm the effect of the output mismatch of PV modules and arrays on the PV system. A new parameter extraction model was proposed to analyze the output loss of the PV system due to output mismatch [8]. The study also confirmed that the larger the number of PV modules, the higher the output loss due to output mismatch [9]. Various studies have been conducted to analyze and improve the output mismatch of PV arrays, but the studies on the electrical characteristics of the system due to the output mismatch of PV arrays under the system configuration and fault condition are insufficient. In large PV plants, the system is constructed mainly by adopting a centralized-type inverter, in which multiple PV arrays are connected to a combiner box and then connected to an inverter and a grid. According to Korea's pre-2017 PV installation standard, blocking diodes and fuses are mandatory to prevent damage to PV modules and arrays due to an overcurrent and reverse current in the design of a combiner box. However, according to IEC TS 62257-7-1: 2010, blocking diodes can be a source of the failure and power loss and are not recommended for use [10].