Abstract
With the rapid increase of research and development of marine energy, including WECs (wave energy converters) and RCECs (river current energy converters), capturing the available local energy in areas is becoming more promising and viable. Adding renewable marine energy as a secondary or main source of energy to our growing grid generation portfolio---and importantly, to derived microgrid-based topologies---will play a key role in the de-carbonization of our infrastructure. However, the integration of these modern generator models into grid-level analysis poses interesting challenges due to the variability of marine resources, new individual elements to model on the WECs and CECs (for example, power-take off interfaces) and hence, the irregular nature of their power output.
The new marine generator models, driven by Variable Energy Resources (VERs) need to co-exist with more traditional generator models that are widely used in steady-state, quasi-steady-state, and dynamic analysis of power systems and their associated computational frameworks. Engineers, computer scientists, and operators need to have a common understanding of marine energy timescales and model resolution in order to reliably integrate and optimize power systems to effectively make use of these VERs.
The work presented here is part of a U.S. Department of Energy project where we are focusing on demonstrating the integration of WEC and CEC generator models with power flow solvers for marine microgrid locations such as the Oregon Coast, Alaska, Hawai'i, and the Caribbean. To accomplish this, several research tasks in this project will support the co-development of an open-source software framework that will make the process of modeling WECs and CECs for power flow solvers accessible and iterable for optimization purposes. This framework will be shared and tested by engineers working on marine energy integration into grid and microgrid topologies. As an initial benchmark for the proposed realistic microgrid locations, we use a modified RM3 WEC model from WEC-Sim, an open-source WEC modeling software written for MATLAB/Simulink. Next, we integrate the marine energy converter data and model from WEC-Sim, designing robust application interfaces for Siemens PTI PSSe, HOMER, and MiGRID. We hope to demonstrate a successful utilization and integration of wave energy in our target microgrid locations using the wave resource data collected at each site. Running and optimizing these models using the site specific wave resource data will show engineers and operators what to expect when introducing wave energy to their energy portfolio.
The WEC-Sim software is rather mature in power conversion modeling from the wave-driven hydrodynamic bodies through the electrical generator. However, no WEC-Sim library provides models for the power electronics needed to supply the WEC generated power to the grid, making integration with a Power Flow Solver a challenging task. By building on the existing WEC-Sim models, an open-source model of the complete wave-to-grid (W2G) system will be created in MATLAB/Simulink. This will enable an accessible way to integrate WECs with a Power Flow Solver. The W2G system will include a back-to-back power electronic converter, consisting of AC/DC converters and an optional energy storage system. With the integrated power flow software and the WEC/CEC plugin, we facilitate the use and multiple-real-scenario scaling of marine microgrid studies. Our open source software will be available on Github and DOE Code for distribution.