Control of a hybrid modular multilevel converter during grid voltage unbalance

Amankwah, Emmanuel K.; Watson, A.J.; Wheeler, Patrick; Clare, Jon C.

Abstract

The recently proposed parallel hybrid modular multilevel converter is considered to be a low loss, low component count converter with soft switching capability of the ‘main’ bridge. The converter has similar advantages to other emerging modular multilevel converter circuits being considered for HVDC power transmission. However, during ac network unbalance the individual ‘chain-links’ exchange unequal amounts of power with the grid which requires appropriate remedial action. This paper presents research into the performance of the converter and proposes a suitable control method that enables the converter to operate during grid voltage unbalance. The proposed control concept involves the use of asymmetric third harmonic voltage generation in the ‘chain-links’ of the converter to redistribute the power exchanged between the individual ‘chain-links’ and the grid. Mathematical analysis and simulation modelling with results are presented to support the work described.

Citation

Amankwah, E. K., Watson, A., Wheeler, P., & Clare, J. C. Control of a hybrid modular multilevel converter during grid voltage unbalance.

• Conference Name: 11th International Conference on AC and DC Power Transmission
• End Date: Feb 12, 2015
• Online Publication Date: Feb 10, 2015
• Deposit Date: Apr 26, 2016
• Publicly Available Date: Apr 26, 2016
• Peer Reviewed: Peer Reviewed
• Keywords: HVDC, modular multilevel, unbalance control, third harmonic injection control
• Public URL: https://nottingham-repository.worktribe.com/output/745179
• Publisher URL: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=7140566
• Additional Information: Published in: 11th International Conference on AC and DC Power Transmission (ACDC 2015), IEEE, 2015. ISBN: 9781849199827, pp. 1-8, doi:10.1049/cp.2015.0084