Study On The Control Strategies Of Centralized DC Transmission For Large-scaled Renewable Energy

Recently, China has speeded up the pace of construction of renewable energy, and the capacity of wind power and photovoltaic arises each year. While constructing renewable energy base and changing Chinese energy structure, it is necessary to consider the situation that the renewable energy resources and load centers are located reversely in China. Therefore, how to enhance the ability of consuming renewable energy has become one of the key issues needed to be solved. For a large-scale renewable energy base, the HVDC system has advantages in the controlablity and transmission capacity with distance, which makes it to be the first choise for the transmission of renewable energy. In order to enhance the ability of consuming renewable energy, there are several things needed be considered firstly. On the one hand, a new DC transmission channel should be built, and a proper way to integrate renewable energy should be designed; on the other hand, the new HVDC control strategies can be used through an existing DC channel, and enhances the ability of consuming renewable energy.In this thesis, based on the centralized DC transmission of large-scale renewable energy base, the integration topology and control strategies of renewable energy are studied, as well as the new control strategy of the centralized DC transmission. Details are as follows:Firstly, the way of integration in photovoltaic stations is studied. The principles and practical topology of photovoltaic integration is analyzed, and the AC and DC way of integration is discussed as well. The DC way is chosen for large-scale photovoltaic power plants, and the relevant control strategy is come up with.Secondly, the way of integration in wind farms is studied. The possible ways in both DFIG and the direct drive blower is discussed. The parallel centralized DC boost mode is chosen for the integration in the large-scale wind farms, and the relevant control strategy is come up with, too.Finally, the control strategies of centralized DC transmission for large-scaled renewable energy is studied. An idea of droop control is come up with through the concept of virtual inertia control in wind farm and the frequency modulation in power system, and it is applied to the HVDC control strategy for the enhancement of the ability of consuming renewable energy. The control strategy is verified with results from numerical simulations in PSCAD/EMTDC.