# Investigation of Failures during Commissioning and Operation in Photovoltaic Power Systems
## 2 Materials and Methods
The power produced in photovoltaic panels is transmitted to the central inverter via collector boxes. At the inverter input, the DC current first passes through the DC-DC converter and then passes through the inverter circuit. The MPPT function is also shown in this block, which performs the inverter control functions in the  
Figure 1: Classification of electrical faults [1]. inverter block and operates at the maximum power point. The AC current coming out of the inverter unit passes through the transformer and is connected to the grid. In this study, electrical faults in photovoltaic power plants are classified according to the region where the fault occurs. In this classification system, faults are detailed according to the regions where they occur. These electrical faults are principally caused by open circuit and short circuit situations. In order to create electrical faults in the MATLAB Simulink program, open circuit and short circuit situations are created in the area where the fault occurs. Methods for creating electrical faults in photovoltaic power plants according to open circuit or short circuit situations are shown in Table 1.  
Since the photovoltaic panels and the grid connection are interrupted in the case of inverter malfunctions, an open circuit condition is created at the inverter output and the reactions on the DC and AC sides are examined. The area where the circuit breaker at the transformer output is located in the photovoltaic power plant is considered the grid connection. For this reason, short circuit and open circuit blocks are used at the transformer output to model grid-related faults in the MATLAB Simulink model of the photovoltaic power plant. When modeling faults that are caused by environmental effects, in contrast to short circuit and open circuit situations, the amount of radiation is changed in order to show the effect of shadowing due to external effects on current and voltage. Ground fault and line-to-line short-circuit fault conditions are produced by using the \"three-phase fault\" object in the MATLAB Simulink program. To generate the open-circuit fault on the DC side, the circuit breaker object is used in the MATLAB Simulink program. Equipment failures on the DC side are simulated by creating a short circuit situation on the DC side under the title \"Photovoltaic Module Fault\". Figure 2: MATLAB Simulink model overview. Within the scope of this study, it is assumed that circuit protection equipment is not active so the fault condition remains. For this reason, circuit protection equipment is not included in the model. To create fault conditions in MATLAB Simulink, certain process steps were followed to standardize fault creation. Firstly, the MATLAB Simulink program was started, and it was ensured that the simulation was working correctly. The process steps for different faults are listed below:  
* DC line-line short-circuit fault: The phase-to-phase short-circuit fault block connected between the photovoltaic panels and the inverter was triggered externally. * DC ground fault: The phase-ground short-circuit fault block connected between the photovoltaic panels and the inverter was triggered externally. * DC open circuit: The breaker block connected between the photovoltaic panels and the inverter was triggered from the outside to open the breaker. * Grid-sourced phase-to-phase short-circuit fault: The phase-to-phase short-circuit fault block connected between the photovoltaic power plant and the grid was triggered externally. * Grid-sourced open-circuit fault: The breaker block connected between the photovoltaic power plant and the grid was triggered from the outside to open the breaker. * Inverter fault: The breaker block connected between the inverter power output side and the transformer was triggered from the outside to open the breaker. * PV module fault: The phase-to-phase short-circuit fault block connected between the output side of one of the photovoltaic modules and the inverter was triggered externally.