DC collection networks for offshore generation

Finney

2017

IET Power Electronics

High-power converters for high-voltage direct current transmission systems and collecting networks are attracting increasing interest for application in large offshore wind farms. Offshore wind farms are capable of generating more electric energy at lower cost when compared with onshore wind systems. In this study, DC/DC voltage conversion should be achieved with a power converter that uses readily available semiconductor devices. A modular DC/DC converter can achieve the required system currents and voltages without exceeding semiconductor ratings. In this study, the operation and control strategy for an input-series-input-parallel-output-series (ISIPOS) energy conversion system for wind systems are presented. The ISIPOS system allows the direct connection of wind turbines to the DC grid. In this research, the design process to control the input and output currents and voltages is explained. In addition, a new method to ensure voltage and current sharing between the different modules is presented and explained. The basic structure, control design, and system performance are tested using MATLAB/ SIMULINK. Practical results validate the control design flexibility of the ISIPOS topology when controlled by a TMSF280335 DSP.

Section: Introductionmentioning

confidence: 99%

Operation and control design of an input‐series–input‐parallel–output‐series conversion scheme for offshore DC wind systems

Darwish

Finney

2017

IET Power Electronics

“…Present offshore farms connect to conventional 50 or 60Hz AC systems by employing mainsfrequency transformers to step up the generator output voltage to collection network voltage levels. Advances in DC/DC converters, particularly High-Frequency (HF) technologies [2,3], allow the heavy line-frequency transformer in an AC grid to be replaced by a high-or medium-frequency transformer, leading to significant weight and size savings. Fig.1 illustrates AC and DC options for the collection grid.…”

Section: Introductionmentioning

confidence: 99%

Modular input‐parallel output‐series DC/DC converter control with fault detection and redundancy

Lian

Adam

IET Generation, Transmission & Distribution

et al. 2016

This version is available at https://strathprints.strath.ac.uk/54599/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the AbstractLarge offshore wind farms will require an extensive sub-sea power network to provide internal interconnection. Present solutions are based around conventional medium-voltage AC architectures. This paper proposes an alternative DC collection network based around modular DC/DC converters with input-parallel-output-series (IPOS) connection. Smallsignal analysis of the converter is presented, to assist in control scheme development for the converter input and output stages. A Lyapunov controller is embedded within the conventional output voltage sharing control loop. A masterslave control scheme is proposed to ensure power sharing under a range of operating conditions, and provides faulttolerant operation since the status of 'master' can be reallocated in the event that the present 'master' module fails.

“…Present solutions are based around conventional medium‐voltage AC architectures. However, recent studies have highlighted the potential benefits of medium‐voltage DC collection networks for high‐capacity offshore wind farms [3–7]. With appropriate selection of DC voltage, reduced losses can be achieved in the DC collection network.…”

Section: Introductionmentioning

confidence: 99%

Medium‐voltage DC/DC converter for offshore wind collection grid

Lian

Adam

IET Renewable Power Generation

et al. 2016

A novel modular DC/DC converter with input-series-input-parallel output-series connection to realise a DC collection power network for large-scale wind farms is presented. The proposed topology uses interconnection of multiple modular cells with low rated voltage and power to enable operation with high voltage at the input and output. Low rated power of individual modules in the proposed DC/DC converter permits the use of a high-frequency ac link, resulting in a significant reduction in transformer size and weight, which makes deployment of DC collection networks in offshore wind farm applications more feasible and effective. In addition, a robust control scheme is developed to ensure power sharing between practical modules with parameter mismatch and during transient conditions. Small- and large-signal analyses are performed in order to deduce the control structure for the converter input and output stages. Simulation and experimental results demonstrate and validate the proposed converter and associated control scheme