A Study of Small Signal Stability of the Power System with VSC Based HVDC Link

Electrical Engineering

The wind power is evacuated using a 5 terminal DC system. Aside from the slack bus, all of the VSC buses' reference powers may be changed to alter the amount of power sent into DC and AC systems. At steady state, the effect of distributing power between an AC and a DC system in varying amounts is examined. When synchronous generators inject power into AC and DC networks, the losses, real and vi reactive power production, and voltage profile of the system are all affected. A real utility system with 156 buses, 209 lines, and wind power-penetrating buses is examined in the above study. A power penetration and load level at different buses and overloading’s in transmission lines and transformers are taken into account to establish the topology of two DC rings. The overloading of the AC lines and transformers has been reduced, according to the results of a load flow study. Increases in wind power might be met with the DC ring, opening the door to further capacity. Furthermore, this technology offers a significant advantage: the control of the active power independently of the reactive power. With the use of different modulation techniques, the VSC can independently control the active power flowing through the transmission system as well as the reactive power being exchanged with the connected AC network. Therefore, different types of controllers and strategies can be used depending on the environment chosen for the VSC-HVDC to operate. In this thesis, for the onshore stations the DC voltage control was set for the active channel and the reactive power exchanged with the connected AC network was the control chosen for the reactive channel. On the other hand, at the offshore stations, the controls used were the active power generated at the wind farms for the active channel and the module of the AC voltage at the PCC of the stations for the reactive channel.

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