Abstract
With the wind industry moving further offshore, High Voltage Direct Current (HVDC) transmission is becoming increasingly popular. HVDC transformer substations are not optimized for the offshore industry though, increasing costs and reducing redundancy. A suggested medium frequency, modular hybrid HVDC transformer located within each wind turbine nacelle could mitigate these problems, but the overall design must be considered carefully to minimize losses. This paper’s contribution is a detailed analysis of the hybrid transformer, using practical design considerations including component library minimization. The configurations investigated include combinations of single phase H-Bridge and Modular Multilevel Converter topologies operating under minimum switching frequency control strategies. These were modelled in the MATLAB/Simulink environment. The impact of the minimum switching control strategy and converter topology on power transfer stability and overall efficiency is then investigated. It was found that the H-Bridge converter generated the lowest overall losses, but there was a trade off with power flow sensitivity due in part to the additional harmonics generated.
Highlights
Over the last decade, the average distance to shore for new wind farms has increased to exploit the higher and more consistent wind conditions, resulting in more High Voltage Direct Current (HVDC) connected wind farms [1,2]
While winding losses are not considered in the analysis, they have been shown to be small compared to the converter losses, and so have a limited effect on the transformer’s topology [20]
The Modular Multilevel Converter (MMC)-MMC topology was run with three different combinations of modules on the primary and secondary converters, while only one combination was run for the HB-HB and HB-MMC
Summary
The average distance to shore for new wind farms has increased to exploit the higher and more consistent wind conditions, resulting in more High Voltage Direct Current (HVDC) connected wind farms [1,2]. To constrain the hybrid HVDC transformer’s switching losses while operating in the MF range, Pulse Width Modulation (PWM) has not been used, and a minimal switching frequency module balancing algorithm has been designed for the MMC This takes advantage of the smaller module capacitance to reduce losses while maintaining stable operation. This paper’s contribution is the detailed evaluation of the HB-HB, MMC-MMC, and HB-MMC configurations using simulations in the MATLAB/Simulink environment These simulations are used to calculate their conduction, switching, and transformer core loss at operating frequencies ranging from 0.5 to 2 kHz. The magnetic transformer design and winding losses are not considered here for brevity as they have been calculated in [20].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
