Electric Collection System Research Articles

Collection System Topology for Deep-Sea Offshore Wind Farms Considering Wind Characteristics

DC series-parallel collection system has recently been widely discussed for integrating deep-sea OWFs because it saves the offshore HVDC stations. However, comparing with traditional offshore electrical collection systems, there is a unique operational problem introducing by the DC series-parallel system that is the wind power curtailment caused by the wind power fluctuations. In this paper, a rigorous mathematical analysis of wind power curtailment is conducted, and an optimization model considering wind power curtailment for DC series-parallel collection systems is proposed. To address the particularities of the series-parallel collection system in graph theory, an improved parthenogenetic algorithm (PGA) is suggested to address the optimization problem. The proposed model and optimization algorithms are tested based on a deep-sea OWF with 56 wind turbines (WTs). The simulation results show that considering wind power curtailment during the DC series-parallel system planning helps to save the levelized cable cost of energy (LCCOE) in the long term, and putting the wiring direction of the series as perpendicular as possible to the prevailing wind direction of the OWF helps to increase the power generation of the OWF and reduce LCCOE.

A reliability review on electrical collection system of battery energy storage power station

The battery energy storage system is a flexible resource with dual characteristics of source and load. It can be widely used in renewable energy consumption, peak shaving and frequency modulation, virtual power plant, and so on. However, the safety problem of energy storage system used in power system is serious, and it should be given an attention. In addition to being affected by the external operating environment of storage system, the reliability of its internal electrical collection system also plays a decisive role in the safe operation of energy storage power station. Therefore, for the reliability problem of battery energy storage power station, this paper analyzes the collection system structure, reliability model, evaluation algorithm and index system, establishes the single state reliability model of battery module considering derating state, presents a framework of a differentiated two-layer reliability evaluation algorithm for collection system of energy storage power station. This paper’s literature investigation can provide a support for the reliability improvement of energy storage power station.

Electrical collection systems for offshore wind farms — a review

A review of the electrical collection systems in offshore wind farms (OWFs) is presented in this paper. The review is based on a categorization of offshore wind power electrical collection systems. The classification encompasses three categories of electrical collection systems, medium voltage AC collection, medium voltage DC collection systems and low frequency AC collection systems (LFAC). This paper summarizes the related research on different collection systems and explores their operational characteristics and challenges. As the initial cost of an OWF is very much influenced, to a great extent, by the configuration of electrical collection and transmission systems, it is necessary to understand the key components and challenges in each collection system configuration.

Multidisciplinary design analysis and optimisation of a reference offshore wind plant

Motivated by the need to develop reference wind energy systems for optimisation and technology assessment studies, the International Energy Agency Wind Task 37 on Wind Energy Systems Engineering is developing a reference offshore wind power plant at the Dutch offshore wind energy areas Borssele III and IV. This paper presents a comparison between two approaches for developing the preliminary design of an offshore wind plant turbine layout, electrical collection system, and support structures. The first is a sequential approach, where components of the wind farm are optimised sequentially, each with its own objective function, thus neglecting potential interactions between them. The second approach uses Multidisciplinary Design Analysis and Optimisation (MDAO), where all components are jointly optimised with the overall system levelised cost of energy (LCOE) as a global objective function. Studying the cases of regular and irregular layouts, the integrated approach always shows a greater improvement in the LCOE of the final design compared to the design resulting from the traditional sequential approach. The most significant trade-off exploited by the MDAO approach used in this study is between losses in energy production due to turbine wake effects and the costs of electrical cable infrastructure.

Analysis of Switching Transients during Energization in Large Offshore Wind Farms

In order to study switching transients in an offshore wind farm (OWF) collector system, we employ modeling methods of the main components in OWFs, including vacuum circuit breakers (VCBs), submarine cables, and wind turbine transformers (WTTs). In particular, a high frequency (HF) VCB model that reflects the prestrike characteristics of VCBs was developed. Moreover, a simplified experimental system of an OWF electric collection system was set up to verify the developed models, and a typical OWF medium voltage (MV) cable collection system was built in PSCAD/EMTDC based on the developed models. Finally, we investigated the influences of both the initial closing phase angle of VCBs and typical system operation scenarios on the amplitude and steepness of transient overvoltages (TOVs) at the high-voltage side of WTTs.