Power electronics has progressively gained an important status in power generation, distribution, and consumption. With more than 70% of electricity processed through power electronics, recent research endeavors to improve the reliability of power electronic systems to comply with more stringent constraints on cost, safety, and availability in various applications. This paper serves to give an overview of the major aspects of reliability in power electronics and to address the future trends in this multidisciplinary research direction. The ongoing paradigm shift in reliability research is presented first. Then, the three major aspects of power electronics reliability are discussed, respectively, which cover physics-of-failure analysis of critical power electronic components, state-of-the-art design for reliability process and robustness validation, and intelligent control and condition monitoring to achieve improved reliability under operation. Finally, the challenges and opportunities for achieving more reliable power electronic systems in the future are discussed.

http://www.tf.uni-kiel.de/etit/LEA-download/publications/2014/80629_jestpe-2013-04-0032_postprint.pdf

Transitioning to Physics-of-Failure as a Reliability Driver in Power Electronics

This paper presents a comprehensive review of step-up single-phase non-isolated inverters suitable for ac-module applications. In order to compare the most feasible solutions of the reviewed topologies, a benchmark is set. This benchmark is based on a typical ac-module application considering the requirements for the solar panels and the grid. The selected solutions are designed and simulated complying with the benchmark obtaining passive and semiconductor components ratings in order to perform a comparison in terms of size and cost. A discussion of the analyzed topologies regarding the obtained ratings as well as ground currents is presented. Recommendations for topological solutions complying with the application benchmark are provided.

/pdf/review-and-comparison-of-step-up-transformerless-topologies-ubtxng7ots.pdf

Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application

The reliability of the microinverter is a very important feature that will determine the reliability of the ac-module photovoltaic (PV) system. Recently, many topologies and techniques have been proposed to improve its reliability. This paper presents a thorough study for different power decoupling techniques in single-phase microinverters for grid-tie PV applications. These power decoupling techniques are categorized into three groups in terms of the decoupling capacitor locations: 1) PV-side decoupling; 2) dc-link decoupling; and 3) ac-side decoupling. Various techniques and topologies are presented, compared, and scrutinized in scope of the size of decoupling capacitor, efficiency, and control complexity. Also, a systematic performance comparison is presented for potential power decoupling topologies and techniques.

A Review of Power Decoupling Techniques for Microinverters With Three Different Decoupling Capacitor Locations in PV Systems

Active power decoupling methods are developed to deal with the inherent ripple power at twice the grid frequency in single-phase systems generally by adding active switches and energy storage units. They have obtained a wide range of applications, such as photovoltaic (PV) systems, light-emitting diodes (LEDs) drivers, fuel cell (FC) power systems, and electric vehicle (EV) battery chargers, etc. This paper provides a comprehensive review of active power decoupling circuit topologies. They are categorized into two groups in terms of the structure characteristics: independent and dependent decoupling circuit topologies. The former operates independently with the original converter, and the latter, however, shares the power semiconductor devices with the original converter partially and even completely. The development laws for the active power decoupling topologies are revealed from the view of “duality principle,” “switches sharing,” and “differential connection.” In addition, the exceptions and special cases are also briefly introduced. This paper is targeted to help researchers, engineers, and designers to construct some new decoupling circuit topologies and properly select existing ones according to the specific application.

Review of Active Power Decoupling Topologies in Single-Phase Systems

High power density is strongly preferable for the on-board battery charger of Plug-in Hybrid Electric Vehicle (PHEV). Wide band gap devices, such as Gallium Nitride HEMTs are being explored to push to higher switching frequency and reduce passive component size. In this case, the bulk DC link capacitor of AC-DC Power Factor Correction (PFC) stage, which is usually necessary to store ripple power of two times the line frequency in a DC current charging system, becomes a major barrier on power density. If low frequency ripple is allowed in the battery, the DC link capacitance can be significantly reduced. This paper focuses on the operation of a battery charging system, which is comprised of one Full Bridge (FB) AC-DC stage and one Dual Active Bridge (DAB) DC-DC stage, with charging current containing low frequency ripple at two times line frequency, designated as sinusoidal charging. DAB operation under sinusoidal charging is investigated. Two types of control schemes are proposed and implemented in an experimental prototype. It is proved that closed loop current control is the better. Full system test including both FB AC-DC stage and DAB DC-DC stage verified the concept of sinusoidal charging, which may lead to potentially very high power density battery charger for PHEV.

/pdf/dual-active-bridge-based-battery-charger-for-plug-in-hybrid-1d7lt51xnj.pdf

Dual active bridge based battery charger for plug-in hybrid electric vehicle with charging current containing low frequency ripple

This paper presents a new microinverter topology that is intended for single-phase grid-connected PV systems. The proposed microinverter topology is based on a flyback converter, where an extra switch is added to separate the decoupling capacitor from the PV Module, which allows for a high voltage and voltage ripples across its terminals. This results in reducing the power decoupling required capacitance. In this manner, long life-time low power density film capacitors can be used instead of life-time limited high power density electrolytic capacitors, resulting in remarkable increase of microinverter's lifespan. The main advantages of the proposed topology are summarized as: 1) eliminating the double-frequency power ripple using a small film capacitor; 2) using long lifetime film capacitors, which will improve the reliability of the inverter; and 3) requiring no additional circuitry to manage the transformer leakage energy. A 100-W microinverter prototype was built to verify the proposed topology. Experimental results show that the proposed topology and its control scheme can realize the power decoupling, while maintaining very good conversion efficiency numbers.

A Single-Stage Microinverter Without Using Eletrolytic Capacitors

This paper proposes a new methodology for calculating the mean time between failure (MTBF) of a photovoltaic module-integrated inverter (PV-MII). Based on a stress-factor reliability methodology, the proposed technique applies a usage model for the inverter to determine the statistical distribution of thermal and electrical stresses for the electrical components. The salient feature of the proposed methodology is taking into account the operating environment volatility of the module-integrated electronics to calculate the MTBF of the MII. This leads to more realistic assessment of reliability than if a single worst case or typical operating point was used. Measured data (module temperature and insolation level) are used to experimentally verify the efficacy of the methodology. The proposed methodology is used to examine the reliability of six different candidate inverter topologies for a PV-MII. This study shows the impact of each component on the inverter reliability, in particular, the power decoupling capacitors. The results confirm that the electrolytic capacitor is the most vulnerable component with the lowest MTBF, but more importantly provide a quantified assessment of realistic MTBF under expected operating conditions rather than a single worst case operating point, which may have a low probability of occurrence.

Reliability of Candidate Photovoltaic Module-Integrated-Inverter (PV-MII) Topologies—A Usage Model Approach

This paper reviews the power decoupling techniques of micro-inverters used in single-phase, grid-tied PV systems. The power decoupling techniques are categorized into three groups: (1) PV side decoupling; (2) DC link decoupling; and (3) AC side decoupling. Various topologies and techniques are presented, compared, and evaluated against the size of capacitance, efficiency and control complexity. Finally, potential topologies and technologies are pointed out as the best options for power decoupling implementation.

/pdf/power-decoupling-techniques-for-micro-inverters-in-pv-5aqj4kxz17.pdf

Power decoupling techniques for micro-inverters in PV systems-a review

A novel single-stage photovoltaic (PV) microinverter with power decoupling capability is proposed in this paper The proposed topology is based on three-port flyback with one port dedicated to power decoupling function so as to reduce the decoupling capacitance, thus allowing for long lifetime film capacitor to be used Operation principle is analyzed in details Key design considerations, including key parameter selections, predictive control strategy, and the dc voltage balance control across the power decoupling capacitor, are given in this paper A 100-W microinverter prototype is built to verify the proposed topology Experimental results show the proposed topology can achieve power decoupling, while maintaining good efficiency

http://pelstechpro.weebly.com/uploads/1/2/8/1/12811276/a_three-port_flyback_for_pv_microinverter_applications_with_power_pulsation_decoupling_capability.pdf

Souhib Harb

Papers

A Review of Power Decoupling Techniques for Microinverters With Three Different Decoupling Capacitor Locations in PV Systems

A Single-Stage Microinverter Without Using Eletrolytic Capacitors

Reliability of Candidate Photovoltaic Module-Integrated-Inverter (PV-MII) Topologies—A Usage Model Approach

Power decoupling techniques for micro-inverters in PV systems-a review

A Three-port Flyback for PV Microinverter Applications With Power Pulsation Decoupling Capability