Design for Reliability of Power Electronics for Grid-Connected Photovoltaic Systems

Abstract

Abstract-Power electronics is the enabling technology for optimizing energy harvesting from renewable systems like Photovoltaic (PV) and wind power systems, and also for interfacing grid-friendly energy systems. Advancements in the power semiconductor technology (e.g., wide band-gap devices) have pushed the conversion efficiency of power electronics to above 98%, where however the reliability of power electronics is becoming of high concern. Therefore, it is important to design for reliable power electronic systems to lower the risks of many failures during operation; otherwise will increase the cost for maintenance and reputation, thus affecting the cost of PV energy. Today's PV power conversion applications require the power electronic systems with low failure rates during a service life of 20 years or even more. To achieve so, it is vital to know the main life-limiting factors of power electronic systems as well as to design for high reliability at an early stage. Knowhow of the loading in power electronics in harsh operating environments (e.g., fluctuating ambient temperature and solar irradiance) is important for life-time prediction, as the prerequisite of Design for Reliability (DfR). Hence, in this paper, the technological challenges in DfR of power electronics for grid-connected PV systems will be addressed, where how the power converters are stressed considering real-field mission profiles. Furthermore, the DfR technology will be systematically exemplified on practical power electronic systems (i.e., gridconnected PV systems).

Reconfiguration of NPC Multilevel Inverters to Mitigate Short Circuit Faults Using Back-to-Back Switches

“…The increased number of semiconductor devices increases the risk of failure since the failure of a single device could cause the whole inverter to fail. Researchers have studied the reliability of power electronics to a great extent in an attempt to reduce the risk of failure and to increase the reliability of power electronic systems for distributed energy resources [6], [7]. The most common faults that may occur in MLIs are open and short circuit faults in power switches [8].…”

Electric-Vehicle Power Converters Model-Based Design-for-Reliability

“…It is possible to determine the operating voltage of the motor, recalling (10): (10) If the threshold of (5) is exceeded, the MTPA trajectory cannot be used any longer, and the control point should be determined by the flux-weakening technique intersecting the current circle with the voltage ellipsis in the dq plane (CPSR operating region). This gives the polynomial (11), again with order four: (11) In this case the desired solution is the maximum among the negative (and real) ones. If all those constraints lead to unacceptable solutions, it means that the requested operating point is unachievable by the motor.…”

“…Coffin-Manson) are unavoidably affected by uncertainty, that is usually dealt with by means of Montecarlo analysis [9], [10], [11], [13], [14]. The authors of this paper present a Montecarlo analysis of the final results to analyze the effects of reliability model parameter dispersion.…”

“…Furthermore, it is worth observing that DfR implies a paradigm switch towards the so called Physics of Failure (PoF) since this approach implies the detection of the root-causes of failure as stated in [9]- [11].…”

“…Therefore, this work, which settles in the automotive scenario, can be regarded as an effort to provide a novel design strategy of power converters from a vehicle-system-level point of view. When reliability of modern power converters is concerned, the approach described by Design-for-Reliability (DfR), rather than reliability testing, is the preferred choice, as it has already been proposed for photovoltaics (PV) and energy systems based on renewables [9]- [11]. Indeed, for these applications life-time prediction is very important because the cost of renewable energy and hence its greater convenience over fossil energy depends directly on the number of faults and unexpected maintenance interventions which are required for the proper operation of PV and wind plants.…”