Research On Hierarchical Optimal Scheduling Of Inter-regional Power System With UHVDC For Wind Power Accommodation

In recent years,the share of wind power in the power system has become larger and larger.The inverse peak shaving and uncertainty of wind power increase the difficulty of the power balance.The participation of UHVDC in long-distance transmission is an important means to solve the shortage of on-site wind power accommodation space.The schedule of the DC tie-line involves different regions.Therefore,the dispatching mechanism is more complicated and the optimization model scale is larger.There are problems such as difficulty in coordination between power grids and synchronization calculation,which restrict the wind power accommodation between different grids.Therefore,it’s practical meaning to study how to coordinate the DC tie-line and various dispatching resources of the source and load to participate in multi-region schedule.For solving the problems mentioned above,the main study in this paper is as follow.(1)In view of the difficulty in the cross-regional wind power accommodation,the restricted factors and adjustment capability under different operation modes considering the characteristics of UHVDC transmission are studied.On the basic,the feasibility of UHVDC participating in cross-regional wind power accommodation is qualitatively analyzed.An improved DC operation model which is "multi-step" is proposed and a cross-regional grid joint dispatch model aiming at the lowest operating cost of the whole grid is established.Through simulation,the effect of the DC tie-line on wind power accommodation is quantified.(2)In order to solve the problem of the coordinated dispatch of DC tie-line,the concept of dynamic equivalent units is introduced and a coordinated dispatching mode based on the dynamic equivalent unit is proposed.In this mode,each region can participate in the optimization of DC tie-line by aggregating the scheduling capabilities of the region.And a dynamic equivalent unit decision model that is independently solved in each area and a DC transmission power dispatch model coordinated by the superior dispatch center are established in this paper.The solution of the model is by continuously updating the dynamic equivalent unit.And the simulation results show that this method realizes the optimal allocation of resources in the whole grid on the basis of improving the economic efficiency of each region’s own operation.(3)In order to alleviate the double peaking pressure imposed on the supply side by the connection of DC tie-line and the uncertainty of wind power,a multi-time scale optimal dispatch strategy based on UHVDC and provincial grid stratification is proposed.It uses the complementarity of UHVDC transmission characteristics and demand-side resource dynamic characteristics.Then considering the uncertainty of wind power,a scenario-based day-ahead optimization scheduling model and an intraday rolling optimization model based on opportunity constraints are established in this paper.The simulation verifies that the proposed method has a good ability to deal with the uncertainty of wind power in the interconnected grid.Both the pressure of thermal power regulation and the grid operating cost are reduced.In summary,this paper proposes a multi-time-scale optimal dispatching model for UHVDC interconnected power grid that comprehensively considers hierarchical coordination and source-DC-load coordination.This model has advantages in promoting the wind power accommodation and improving the operating economy of the interconnected grid.And it has reference significance for the formulation of the interconnected grid dispatching plan.