Maximal electric power generation from varying ocean waves with LC-tuned reactive PTO force

TL;DR

The paper addresses the challenge of maximizing electric power generation from wave energy converters (WECs) under variable ocean wave frequencies by emphasizing the essential role of reactive PTO forces. It introduces a simple LC-tuned WEC that uses a parallel LC network with a permanent magnet linear generator (PMLG) to generate leading and lagging reactive currents, enabling resonance with the wave input across a range of frequencies. A complete closed-loop hydrodynamic model is derived, and three LC-tuning rules are established to set the reactive PTO forces so the WEC resonates at the input frequency, yielding maximal active electrical power. Analytical results provide explicit expressions for mechanical power absorption, active and reactive power, power factor, optimal load $R^*$, and capacity requirements for the PMLG and LC network, with simulations validating performance across multiple frequency scenarios. This approach offers a passive, tunable and potentially cost-effective path to wideband power extraction and informs generator sizing and LC component design for practical WEC deployments.

Abstract

The reactive Power Take Off (PTO) force is the key to maximizing mechanical power absorption and electric power generation of Wave Energy Converters (WECs) from ocean waves with variable frequency, but its study is limited due to its difficulty in physical realization. This paper presents a simple yet effective $LC$-tuned WEC that generates a tunable reactive PTO force from tunable inductor $L$ and capacitor $C$ in the WEC. A complete closed loop system model of the WEC is derived first, then three quantitative rules are obtained from analyzing the model. These rules are used to tune the $LC$ network, and hence the reactive PTO force that drives the WEC, to resonate with the input wave force and generate maximal electric power over a range of wave frequencies. Mathematical analysis of the WEC and tuning rules reveals the analytical and quantitative descriptions of the WEC's mechanical power absorption, active and reactive electric power generation and power factor, optimal electric resistance load, and the generator and $LC$ capacity requirements. Simulation results show the effectiveness and advantages of the proposed WEC and verify the analysis results.

Figures (9)

• Figure 1: New WEC structure and mechanical-electrical interaction model
• Figure 2: WEC response at natural resonance frequency $\omega = \omega_0$
• Figure 3: Mechanical and active electrical powers of WEC at $\omega = \omega_0$
• Figure 4: Responses of tuned and untuned WECs at $\omega < \omega_0$,
• Figure 5: Mechanical and active electrical powers of tuned and untuned WECs at $\omega < \omega_0$