Impact of control strategies on the rating of electric power take off for Wave Energy conversion

Abstract

In Wave Energy Converters (WECs) the maximum power extraction would be achievable at the expense of a very high rating of the electric and power electronics equipment. The goal of this paper is to show how a convenient trade-off between high power extraction and viable electrical device ratings can be achieved by a proper choice of the WEC control strategy. The case of a direct coupled point absorber in heave is considered, in order to show the impact of the most common control strategies on the power performance. Consequently a revised approach to WEC control is proposed, which is simple and takes into account these potentially conflicting requirements. The targeted application of the presented tool is at the design stage of the power take off, but it also offers a reference-case control principle that can be conveniently adapted to improve the device exploitation when working in real sea conditions. Theoretical analysis and computer simulations are used to show the validity of the proposed approach.

Reliability analysis of IGBT Inverter for Wave Energy Converter with focus on thermal cycling

“…In general the optimal energy extraction is achieved when the point absorber is moving with a 90 • phase shift to the waves [6]. Several methods of approaching this production mode are described, the best known being reactive control [7], [8] and latching control [9]. Figure 5 shows an electrical equivalent circuit for the WEC where the dynamic behavior of the WEC is modeled as an RLC circuit.…”

Exploring the Potential for Increased Production from the Wave Energy Converter Lifesaver by Reactive Control

“…The speed at which field weakening begins, ω max = ω f w , can be expressed by the generator characteristics, as seen in Equation (24). The method used for determining the field weakening reference d-and q-axis currents is based on the robust field weakening control strategy described by Pan and Liaw [19].…”

“…Previous estimations have been made for the Lifesaver concept [23], and some preliminary investigations have also been performed into a potential increase in annual energy production using reactive control. However, the latter paper does not take into account the generator force limitation or generator losses, and these factors become very significant under reactive control in particular [24]. This means that an investigation into increased energy production using reactive control with generator limitations is a very interesting and novel addition to the former research.…”

Sizing and Control of the Electric Power Take Off for a Buoy Type Point Absorber Wave Energy Converter

“…This is known as one of the key factors to the success of a WEC concept. The current primary focus of such activities is on the search for the reliable energy extraction system to fulfil the technology as well as the economical viability [3]. Several remarkable technologies have been investigated, and some of them are near to technological readiness.…”

“…To date, the design and development of such system has involved extensive studies on the mechanical and the hydrodynamic aspects while little attention has been given to the power take-off (PTO) systems [3], [4]. This causes the PTO and electrical components installed on WEC are generally oversized, in order to achieve the desired power extraction capacity.…”