No abstract

Voltage-type sources have dominated as an input source for power electronics converters for a long type. The existence of duality implies that there are also current-type sources. The growing application of renewable energy sources such as wind and solar energy has evidently shown that the current-type input sources exist in reality such as photovoltaic (PV) generator or the feedback technique used in controlling the power electronics converters in the renewable energy systems changes the power electronic converters to behaving as such. The recent research on renewable energy systems has indicated that the current-type input sources are very challenging input sources affecting the dynamics of the interfacing converters profoundly. This paper provides a comprehensive survey of the effects of the PV generator on the dynamic behavior of the corresponding interfacing power electronic converters.

No abstract

No abstract

Power quality problems caused by grid-connected renewable energy inverters have been reported increasingly in recent literature. Excessive harmonics and interharmonics arise when the inverter starts to interact with the grid impedance. Small-signal impedance models have been proven to be useful tools to analyze the stability margins. However, in presented dq-domain models the grid voltage feedforward loop employed by the inverter is not included. To fill this gap, this paper presents a new impedance model, which includes the effect of feedforward, to analyze impedance-based stability in the presence of large grid impedance. The model was verified by impedance measurements from a laboratory prototype. The model gave accurate predictions of small-signal stability when the Nyquist stability-criterion was applied. Thus, the model can be used to re-shape the inverter impedance to avoid stability problems. The developed impedance model also provides a useful tool to monitor stability margins online, which necessitates adaptive impedance-shaping of grid-connected inverters.