The Optimal Dispatch Of Deferrable Load

With the development of smart grid, some controlled resources from demand side play an important role in power system. In the frame of smart grid, the high two-ways communication technologies offer the interaction between demand side and grid. Based on incentive of electric price from market, the controlled resources can respond to the dispatch of grid through transferring their time of using. Deferrable load belongs to the controlled resources because of the flexible working period. Through shifting the demand characteristic of deferrable load along the time horizon, the working period can be transferred and the demand can be altered. With the optimal shifting, deferrable load can have the values such as shaving the peak, filling the valley, releasing the burden of frequent adjustment from the supply, offsetting the fluctuation from renewable energy, reducing the cost of supply demand and the injected energy from transmission network to distribution one at whole periods of dispatch. In order to show the values, three tasks are done.Considering the problem of the balance between the supply and demand at first, some features of deferrable load are researched such as the shifting characteristic, the limit of shifting, the constant energy demand and the aggregated characteristic. According to the features, an optimal day-ahead dispatch model where the group of deferrable load is to track dispatch signal reflecting the desire from supply is presented. Through simplifying the model with some measures, the branch-and-bound method is used for solving. In the simulation, the validity of the model and some values are verified.Then, considering the cost characteristic of generators with the guarantee of the balance, the problem of the coordinated dispatch between deferrable load and generators is researched. Because the dispatch of deferrable load is at distribution layer and the dispatch of generators is at transmission layer, the dynamic economic dispatch model based on the Benders decomposition is presented for resolving the dispatch limit of being at different layer. Though decomposing the model and constructing the interaction frame between distribution layer and transmission one, the problem of the coordinated dispatch is solved at different layer. In the simulation, the solving of the model is converged after the limited iterations and the cost which is relative to the cost without dispatching deferrable load is reduced.Finally, based on the constraint of power flow equations at distribution network, the problem of how to shift deferrable load for optimizing the operation mode and reducing the injected energy from transmission is researched. Because the aggregated characteristics make the problem included the coupled power flow equations at time horizon, the solving of problem is very difficult. Two types of the simplified models based on Taylor’s formula without the constraint of power flow equations are presented to solve the problem approximately. In the simulation, the simplified models can make the injected energy reduced with the optimal shifting.