Power Quality in Renewable Energy Systems - Challenges and Opportunities

Power quality in traditional power systems is concerned with voltage problems caused by abnormal operation or nonlinear load behavior. The integration of renewable energy into the power grid introduces new power quality problems. In addition to the intermittency of renewable production, which leads to more frequent voltage fluctuation, and the switching in the power electronics interfaces, which injects high-frequency harmonics into the system, harmonic resonance and other dynamics power quality problems become more prevalent due to the complex and fast dynamics and control of power electronics interfaces. This paper reviews the sources of harmonic resonance involving renewable energy and presents a systematic method to identify and characterize such dynamic power quality problems. A distributed generation test-bed is also presented as an experimental platform for the study of system harmonic resonance and other control-related power quality and stability problems. Measurement results involving single-phase solar and three-phase wind inverters are presented to validate the analysis method and to demonstrate possible mitigation techniques. The need for advanced autonomous control that enhances system stability and mitigates system harmonic resonance are discussed. Issues related to electromagnetic interference (EMI) generated by renewable energy sources and the need to develop EMI compliance requirements for such sources are also discussed.

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