Abstract
An improved Maximum Power Point Tracking (MPPT) method based on a purely mechanical wave energy converter (WEC) of gyroscope precession is proposed. The method adopts dynamic perturbation step adjustment, which improves the stability of power output and reduces steady-state oscillation. The paper introduces the principle of the device, establishes the mathematical model, and obtains the complete expression of power. The effect of wave frequency, pitch amplitude, power take-off (PTO) damping coefficient, and flywheel rotating speed on power output is analyzed. The output regression equation is established, and the extraction conditions of the maximum power are summarized and predicted. Aiming at the time-varying nature of actual ocean waves, a variable step size modified maximum power point (MPP) tracking control algorithm based on perturbation and observation (P&O) method is proposed. The algorithm has a unique technology to dynamically change the perturbation size, which not only improves the dynamic response but also reduces the oscillation. Besides, the boundary conditions ensure that the algorithm will not deviate from the motion trajectory, and the average filtering method and steady-state judgment can further reduce steady-state oscillation. In various ocean conditions, the proposed method has better output stability compared with other variable step size algorithms. Finally, different wave working conditions are given in the experiment, and the results verify the effectiveness of the proposed MPPT control strategy in experimental equipment. The device will be suitable for distributed power sources in small islands and ports.
Highlights
Published: 11 May 2021In the past few decades, the entire world has lived in a great crisis of energy shortage and the deterioration of the environment [1]
The average power generation in 25 s obtained by the Maximum Power Point Tracking (MPPT) control is 10.9 W, which accounts for 85.96% of the optimal power generation obtained by data fitting, which directly proves the feasibility of the algorithm
This paper proposes a modified MPPT algorithm and realizes the maximum power capture under different working conditions based on the gyroscope wave energy converter (WEC)
Summary
In the past few decades, the entire world has lived in a great crisis of energy shortage and the deterioration of the environment [1]. In all kinds of WECs, point absorbers [12,13], oscillating water columns [14,15], and flaps [16] have become the most common devices in the wave energy field. Kobe University applied the gyroscope principle to extract wave energy in the low-energy density ocean and successfully developed a 5.5 kW WEC in 2003 [28]. Compared with other structures of WEC, this paper creatively develops a compact, high-safety, and non-polluting purely mechanical wave power generation system. It is anchored underwater and can be lowered to the seabed in extreme ocean conditions, thereby avoiding potential damage near the sea surface.
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