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With the development of VSC HVDC transmission, the realization of the first VSC MTDC grid is coming within reach. An outstanding issue is DC voltage control in MTDC Systems. The easiest way to maintain stable operation is to assign the task of DC voltage regulation to one converter. This paper discusses a control strategy for an extended VSC MTDC grid using a typical DC voltage control on one DC bus, combined with a DC voltage droop characteristic on the other DC buses. The impact of the proposed control structure on the stability of the AC and DC grid is investigated by numeric simulations using the MatDyn software package.

SUMMARYVoltage source converter high voltage direct current (VSC HVDC) is a relatively new technology which allows the connection of islanded power systems. As such, it can form a connection between large-scale future offshore wind farms and the onshore transmission grid. In this paper, the VSC HVDC solution is proposed as a promising alternative for high voltage alternating current (HVAC). The choice for a transmission technology is primarily based on economic considerations. Therefore, the economic value of VSC HVDC is investigated in this paper. VSC HVDC has important technical advantages for submarine installation compared to HVAC. The aim is to monetize these advantages in an economic comparison. Possible wind farm topology simplifications and optimizations due to the use of VSC HVDC are taken into account. Depending on the ownership of the transmission cable, the break-even cable length, above which the HVDC option is chosen, varies. A sensitivity analysis is included in this paper.

Impacts on electrical protections in radial distribution networks with distributed generation, considering a high penetration of sources based on invertersThis document analyzes the time response of two electrical protection schemes in different scenarios of distributed generation. Its implementation is carried out in the 13-node IEEE system, to which modifications were made in order to simulate a typical 13.2kV electrical network in Colombia. Initially, there is presented a theoretical part in which the characteristics of electrical protections and the main protection schemes implemented for distribution networks are explained, to later analyze the case studies and their considerations.Finally, the results of the simulations obtained for each of the selected protection coordination schemes are presented, taking into consideration the scenarios of minimum and maximum demand of the system. The different fault impedances that can occur and the types of generation connected to the distribution network are also taken into account (synchronous generators and static generators).

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