Real Field Mission Profile Oriented Design of a SiC-Based PV-Inverter Application

Abstract

This paper introduces a real field mission profile oriented design tool for the new generation of grid-connected photovoltaic (PV)-inverter applications based on silicon carbide devices. The proposed design tool consists of a grid-connected PV-inverter model, an electrothermal model, a converter safe operating area (SOA) model, a mission profile model, and an evaluation block. The PV-system model involves a three-level bipolar switch neutral point clamped (3L-BS NPC) inverter connected to the three-phase grid through an LCL filter. Moreover, the SOA model calculates the required converter heatsink thermal impedance Z th_ H in order to perform in a safe mode for the whole operating range. Furthermore, the proposed design tool considers the mission profile (the measured solar irradiance and ambient temperature) from the real field where the converter will operate. Thus, a realistic loading of the converter devices is achieved. To consider one-year real field measurements of the mission profile, an accurate long-term simulation model is developed. The model predicts the junction and case temperature of the converter devices, for three different case scenarios. In the first case, a one-year mission profile is used into the model with a sampling rate of 5 min. For the second and third case, a more detailed analysis is performed for a one-week mission profile (in the winter-summer time) with a sampling rate of 25 s. The simulation results shows the thermal loading distribution among the converter devices (MOSFET, IGBT+FD) in terms of junction (average, peak, ΔT) and case (average) temperature for all three simulation cases. Finally, the evaluation block is used to analyze the results in order to perform a thermal-loading-based classification of the converter devices.