Computationally-efficient Modelling of Wave Energy Conversion Systems via Pseudo Steady-State PMSM Model

Ocean wave energy is a widely available and largely unexploited renewable energy source. Generation equipment needs to operate reliably and withstand rough seas, so power shedding in high sea states is as important as maximum power extraction in low sea states for minimum levelized cost of energy. Wave resources fluctuate and are represented by statistical distributions, so sizing of the powertrain components needs to be optimized over multiple simulations. Computationally efficient models are required to represent the power-limiting operation of the generator, and include the wave frequency dynamics with a period of a few seconds, over a run duration of an hour. This paper develops a new pseudo-steady-state model of the permanent magnet synchronous machine (PMSM), including field-weakening operation. Dynamic equations for the generator and current control are replaced by an analytical solution giving a factor of 15-40 times speed up in solution time.