Abstract
Renewable energy is steadily increasing its penetration level in electric power systems. Wind and solar energy have reached a high degree of maturity, and their impacts on the grid are well known. However, this is not the case for emerging sources like wave energy. This work explores the impact of the fluctuating power injected by a wave energy converter on the distribution grid voltage and proposes a strategy for mitigating the induced voltage fluctuations. The paper describes the mechanics of how a fluctuating active power injection leads to grid voltage fluctuations and presents an unbalanced three-phase power flow tool that allows one to quantitatively analyze the voltage evolution at every phase and bus of a distribution grid driven by this power injection. The paper also proposes a corrective action for mitigating the voltage fluctuations that makes use of the hardware resources already available in the wave energy converter, by means of a control strategy on the reactive capability of the grid-side inverter. The use of a STATCOM as additional reactive compensation equipment is also explored. The effectiveness of the proposal is assessed in the IEEE 13-bus test feeder showing that, in some cases, the wave energy converter by itself is able to mitigate the voltage fluctuations that it causes. If not, a STATCOM can provide the extra reactive capability needed.
Highlights
Renewable resources of energy have been increasing their penetration level in electrical grids
This paper presents a control strategy applicable in real unbalanced distribution grids that implements the authors’ idea of exploiting the wave energy converters (WEC)’s own reactive resources for the mitigation of voltage fluctuations
The paper is organized as follows: Section 2 formulates the problem of voltage fluctuations caused by power variations along with some metrics; Section 3 describes the implementation of the three-phase unbalanced load flow; Section 4 presents the wave-to-wire model of the WEC; Section 5 analyzes the voltage impact of the WEC connection; Section 6 presents the proposed control strategy; Section 7 shows the assessment of the strategy with simulation results; and Section 8 draws the main conclusions
Summary
Renewable resources of energy have been increasing their penetration level in electrical grids. DG systems can aid in the grid support with ancillary services and in environmental issues, since most of these primary sources are non-polluting, as photovoltaic, wind, hydro and wave generation The latter technology, unlike the others, is still under development, and its impact on the electrical grid and its compliance with the connection requirements are the subjects of current research. Another way is presented in [27], where an initial study has been conducted with a balanced radial distribution grid In this case, the strategy is to use the reactive power capability of the WEC power electronic converter to mitigate the voltage fluctuations, avoiding the need for additional energy storage equipment. The paper is organized as follows: Section 2 formulates the problem of voltage fluctuations caused by power variations along with some metrics; Section 3 describes the implementation of the three-phase unbalanced load flow; Section 4 presents the wave-to-wire model of the WEC; Section 5 analyzes the voltage impact of the WEC connection; Section 6 presents the proposed control strategy; Section 7 shows the assessment of the strategy with simulation results; and Section 8 draws the main conclusions
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