A Novel Piecewise Velocity Control Method Using Passivity-Based Controller for Wave Energy Conversion

Abstract

By studying the working principle of a maximum power point tracking (MPPT) method called active phase control (APC), we found that not only was the phase difference between the wave excitation force and the velocity reduced, but also the magnitude of the velocity increased. For the direct-drive wave energy converter with a permanent magnet linear generator (PMLG), the velocity of the PMLG in the no-load state is larger than that in any power generation states. According to this characteristic, a novel piecewise velocity control (PVC) method and its trajectory planning scheme for a sealed-buoy wave energy converter (SBWEC) are proposed to obtain the maximum power extraction condition. Considering the irregularity of ocean waves and that the proposed method needs to frequently change the operating state of the PMLG, a passivity-based controller (PBC) is designed. With energy modification and damping injection, rapid convergence and asymptotic stability of the system are guaranteed, so that the proposed MPPT method can be perfectly implemented. The comparative simulation results for regular and irregular waves demonstrate that it is an effective and promising power control method. INDEX TERMS Sealed-buoy wave energy converter, permanent magnet linear generator, piecewise velocity control method, trajectory planning scheme, passivity-based controller.

A Review of Power Electronics for Nearshore Wave Energy Converter Applications

“…These WEC research used different power electronics converters according to their applications. In [23], [46], [57]- [66], [47], [67]- [70], [48]- [50], [52]- [54], [56] a three-phase AC/DC/AC converter is used to dispatch power to the grid, and in [23], an active DC/AC converter is used as the control element. In [60], a single-phase AC/DC/AC converter is used.…”

“…Based on this research, it can be summarized that the most commonly used modulation technique to control the converters is the PWM technique [23], [47], [73], [49], [51], [52], [59], [61], [69], [71], [72] with the specificity of the Space Vector Pulse Width Modulation (SVPWM) in [48], [59], [69], [70], [73]. According to the application, these modulation techniques control the switching operation of the IGBT/MOSFETs in the converter, which is responsible for generating and regulating the AC sinusoidal voltage output at the desired output frequency.…”

“…[55]- [62] [53], [77], [78] AC/DC [68] [65], [66], [69], [70], [79] -DC/DC [67], [68] [54], [59] hydraulic power take-off system (PTO) simulation using the Simscape library in Matlab/Simulink. Both simulation and experimental results of a hydraulic system of the WEC are proposed in [106].…”

A Review on Power Electronic Topologies and Control for Wave Energy Converters

“…Although the control system improved the transient stability, the work did not discuss the effect on output power quality or the devices' power losses. Beside improving the power electronic structure, several publications targeted improving the control schemes of the WEC AC/DC/AC back-to-back converters [58][59][60][61][62][63][64][65][66][67]. In [58], a non-linear control strategy using linear quadratic regulator (LQR) techniques is proposed to improve the controllability of the WEC system.…”

Generator Design Considering Mover Action to Improve Energy Conversion Efficiency in a Free-Piston Engine Generator

“…The input energy of the systems has a random waveform with nonconstant cycles and amplitudes. The design and control of linear generators considering the characteristics of ocean power generation and vibration power generation have been proposed [6][7][8][9].…”