Drives Comparison for Reciprocating and Renewable Energy Applications

The objective of this work is to compare and analyze brushed DC, induction, brushless DC, and synchronous reluctance machines and drives in reciprocating applications. In particular, this work is focused on wave energy generator applications. In contrast to wind energy, the ocean environment can require bidirectional operation of the generator. For this study, the efficiency of a set of small induction, permanent magnet synchronous, brushed DC, and synchronous reluctance drives and machines were compared side-by-side in a reciprocating application against the typical constant operation used to determine steady state efficiency. The presented results suggest that drives and machines used in ocean wave energy should not expect a large de-rating in nameplate machine or drive efficiency compared to the same drive or machine producing the same amount of power constantly. In addition, it is shown that the frequency of reciprocation (e.g., ocean wave frequency) has little impact on efficiency.