SimPowerSystems Model of a 1000-MW HVDC-MMC Interconnection.

DC links are becoming the preferred means for power exchange between countries and
transmission of power from renewables (hydroelectric plants, off-shore wind power and
solar farms) to power grids. Several of these systems are presently in operation, for
example the INELFE project (France-Spain interconnection), the Dolwin1 project
(offshore wind HVDC link), or planned for future projects such as the Northern Pass
(Canada-USA 1090-MW DC link).
Our example will illustrate one typical VSC topology used nowadays: the Modular Multilevel
Converters (MMC) technology. In the example, MMC converter is implemented
using an aggregate model to simulate 36 power modules per arm. With this aggregate
model, control system dynamics, converter harmonics and circulating currents
phenomena are all well-represented. However, having only one virtual capacitor to
represent the 36 capacitors of the arm, the model assumes that capacitor voltages of all
power modules are well-balanced. The aggregate model runs much faster than a detailed
model that would use two switching devices and one capacitor for each individual power
module. This aggregate model is also well-suited for real-time simulation.
Simulating our SPS model for 10 seconds allows observation of the interconnection
operation during start-up (capacitor charging), voltage regulation, and power regulation.
A comparison between this aggregated model and a SPS detailed model is also provided.
A Help File containing useful information on the model is included as well.