Coupled Modeling and Advanced Control for Smooth Operation of a Grid-Connected Linear Electric Generator Based Wave-to-Wire System

Abstract

The perpetual oscillations of ocean waves produce potential energy, which can be converted to electrical energy with the help of direct drive linear generators. The fluctuating generated power poses a major challenge when it is supplied to the power grid. In this paper, a supercapacitor provides the short-term energy storage to buffer and smooth out the power fluctuations. A new coupled model of a wave energy converter and a linear generator is proposed for its response characterization under varying system conditions. The developed model and an advanced control strategy is used to exhibit a smooth and stable operation of the wave-to-wire system. The generator side converter is controlled to extract the maximum power from the waves and to minimize the generator losses by controlling its d-axis and q-axis currents. The grid side converter is controlled to keep the dc-link voltage constant and to generate the required voltage waveforms at the point of common coupling. The performance of the proposed control strategy for the wave-to-wire system is investigated under different applied diffraction forces. The simulation results show that with the use of proposed control scheme and the supercapacitor, the wave-to-wire system can operate in a smooth and stable operation under normal and fault conditions.

Optimal Design of Fractional-Order PID Controllers for a Nonlinear AWS Wave Energy Converter Using Hybrid Jellyfish Search and Particle Swarm Optimization

“…Similarly, in [17], the salp swarm algorithm [18] was employed to find the optimal gains of the PI controllers, and the system behavior was observed in the presence of irregular waves. In [19], a supercapacitor with a bidirectional converter was connected in parallel to a DC link to provide constant power to the grid. In [20], the supercapacitor technique was also employed in a hybrid wave-solar power plant to provide constant power to a version three (V3) supercharging station that charges Tesla cars.…”

Recent advances in wave energy conversion systems: From wave theory to devices and control strategies

“…One of the popular converter types used in the WEC applications is the fullscale converter mainly used with linear permanent magnet generators (LPMG), which have high force density and efficiency at low speeds [93][94][95][96][97][98][99]. The electrical 615 circuit schematic of a full-scale converter is depicted in Figure 8.…”

“…A back-to-back converter is to connect the generator, with a variable voltage and frequency, to the grid, with a constant frequency, in a controlled active power transfer mode. The proposed controller in [95][96][97] for generator side and grid side converters will be briefly explained in the following subsections.…”

“…The battery or supercapacitor is delivering or absorbing the power mismatch between the WEC and the grid using a bidirectional DC-DC converter. In [96], to control the DC-DC buckboost converter and DC-AC converters, two cascaded control loops and a voltage oriented controller (VOC) were utilized, respectively, as shown in Fig. 12.…”

Grid integration aspects of wave energy—Overview and perspectives

“…In [8,[80][81][82][83][84][85][86][87][88][89][90], the Archimedes Wave Swing (AWS) wave energy converter is studied. The AWS utilises a direct drive PTO (a linear permanent magnet generator (LPMG)) as shown in Table 5.…”