Machines and Drives Comparison for Low-Power Renewable Energy and Oscillating Applications

The objective of this paper is to analyze, test, and compare machines and drives in oscillating applications. In particular, this paper is focused on low-power wave energy generator applications, such as autonomous weather and monitoring buoys with power requirements in the 100 W and less range. Due to the oscillating motion of waves, the ocean environment can require bidirectional and variable speed operation of the generator. In this research, the efficiency of a set of small brushed dc, induction, brushless dc, and synchronous reluctance drives and machines were compared in constant and oscillating operation. The presented results show that drives and machines used in low-power oscillating applications (e.g., ocean wave energy) should not expect a significant derating with respect to their nameplate rating. In addition, it is shown that the frequency of oscillation (e.g., ocean wave frequency) has little impact on efficiency.