Investigation into Thermal and Acoustical Characteristics of Power Electronic Devices used for Photovoltaic Solar Systems

Power electronic converters (PECs) play a vital role in the power industry, in particular, in solar photovoltaic energy systems. Damage to any single PEC component either reduces the efficiency of the entire system or causes it to malfunction. Thermal stress from switching devices used in PECs is a major contributor to failures in those systems. Most commonly used condition-monitoring techniques are based on intrusive electrical and thermal measurements. Therefore, there is a timely need for non-intrusive, non-contact and reliable monitoring techniques that can detect failures at an early stage. The aim of this work is to assess the possibility of extracting useful condition-related information using thermal and acoustic characteristics of power electronic devices (PEDs) under different operation conditions. First, a 3-D finite element model was developed to gain clear understanding of thermal and acoustical characteristics of PEC components. Second, the outcomes of the derived model were validated using experimental setups. The thermo-acoustic behaviour of this model was explained, by applying equations relating to heat and acoustic diffusion over the converter geometry through the semiconductor layers of the electrical contacts. Operational, environmental and loading effects on the generated acoustic signals were studied in detail both in time and frequency domains. Results showed that the measured acoustic signals are observable and the accumulated signal is significantly visible and detectable even at high frequency (about 300 kHz). The peaks of the measured signals at the transition instance of the PWM proved to be an important element for predicting acoustic and thermal behaviour, which was validated by a referenced temperature sensor. Thus, the electro-thermal temperature can be relayed to an effective monitoring system, making future investigations in this area worth pursuing.