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For small scale roof-top systems, there is a trend towards module-integrated electronics. Module integrated ac inverters (ac modules) connect each photovoltaic (PV) module separately to the single-phase grid. They feature not only increased yield due to module-level maximum power point (MPP) tracking, but also further advantages such as reduced installation cost. This work investigates the concept of subpanel-level MPP tracking for ac modules, which allows us to increase yield thanks to reduced mismatching losses. Topology concepts to realize such a converter are systematically investigated and categorized. A topology comparison identifies two promising system concepts: first a single-stage converter with a three-port power balancer and second a two-stage topology with three paralleled dc–dc converters and a pulse width modulation full bridge. The later features the advantage of a small power-decoupling capacitor and is therefore further investigated. A model-based optimization of the investigated multi-input ac module is performed, applying high performing Gallium Nitride (GaN) devices and nanocrystalline core materials to increase efficiency. The built prototype confirms the accuracy of the model-based optimization. The performed efficiency study reveals an achievable efficiency of \eta \text{EU} = 94.5%. In order to compete with single-input ac modules, achieving typically an efficiency of 95.5%, the efficiency of multi-input ac modules must improve beyond the level achieved with the investigated two-stage ac-module topology. Given this result, the alternative system concept with a three-port power balancer in combination with a single-stage converter seems to be more promising, as it is conceptually similar to the high efficient single-input ac modules and may achieve the same high efficiency. [ABSTRACT FROM AUTHOR]

Hardware-in-the-Loop tests of components for high-voltage dc transmission grids, for example circuit breakers, require converter systems capable of generating a high output current with fast transients of the output signal at different output voltages. In this paper, a three-level buck converter (N3L) employing three different supply voltages to enable a wide voltage operation range is presented. The modulation of the converter is investigated in detail with special focus on ripple cancellation, the startup of the interleaved converter and the level shifting between different converter output voltages. A prototype system is designed and constructed, optimized for pulsed power operation and compared to a two level and to a neutral point clamped converter design. The system has been simulated numerically and the design boundaries are validated by measurements on the prototype system. [ABSTRACT FROM AUTHOR]

Electronic ballasts for high-pressure sodium lamps based on an ac-chopper topology are proposed as a cheaper and less complex alternative to the industry-standard low-frequency square-wave ballasts. In this paper, the design process of the ac-chopper ballast is reviewed, and the design tradeoffs caused by the single-stage topology are discussed. The analytical and simulation results are verified with measurements of a 250-W prototype system, including a detailed list of the losses for the different circuit components and electromagnetic compatibility measurements. Due to the disadvantages of the single-stage topology, a comparison to a two-stage ballast using the inverter stage of the ac-chopper ballast with a separate power factor correction stage is provided. [ABSTRACT FROM PUBLISHER]