Abstract
Modular multilevel converters (MMCs) are expected to play an important role in future high voltage direct current (HVDC) grids. Moreover, advanced MMC topologies may include various submodule (SM) types. In this sense, the modeling of MMCs is paramount for HVDC grid studies. Detailed models of MMCs are cumbersome for electromagnetic transient (EMT) programs due to the high number of components and large simulation times. For this reason, simplified models that reduce the computation times while reproducing the dynamics of the MMCs are needed. However, up to now, the models already developed do not consider hybrid MMCs, which consist of different types of SMs. In this paper, a procedure to simulate MMCs having different SM topologies is proposed. First, the structure of hybrid MMCs and the modeling method is presented. Next, an enhanced procedure to compute the number of SMs to be inserted that takes into account the different behavior of full-bridge SMs (FB-SMs) and half-bridge submodules (HB-SMs) is proposed in order to improve the steady-state and dynamic response of hybrid MMCs. Finally, the MMC model and its control are validated by means of detailed PSCAD simulations for both steady-state and transients conditions (AC and DC faults).
Highlights
Multiterminal high voltage direct current (HVDC) grids are expected to be used to gather renewable energy from wind and solar power plants
For power grid studies of multiterminal HVDC grids, it is important to capture the interaction between the Modular multilevel converters (MMCs) and the DC and AC grids
Proposed simplified arm Thévenin equivalent model is compared its verification with the detailed
Summary
Multiterminal high voltage direct current (HVDC) grids are expected to be used to gather renewable energy from wind and solar power plants. Energies 2020, 13, 180 conditions such as blocked states, switching and conduction losses, converter start-up procedures, or internal converter faults They are the most complex and accurate models but the computational burden for EMT programs makes their use for power system studies difficult. For power grid studies of multiterminal HVDC grids, it is important to capture the interaction between the MMCs and the DC and AC grids For this reason, it is necessary to properly represent the behavior of the MMCs during steady-state and transient conditions like AC and DC faults or SM block states. It is not paramount to model other internal aspects like SMs faults, switching and conduction losses, etc In this regard, simplified arm Thévenin equivalent models offer a good tradeoff between accuracy and computational burden.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
