Distributed Secondary Control And Economic Dispatch Of Microgrids

In recent years, with the aggravation of the energy crisis and environment pollution, the distributed generation technology with renewable energy as the main energy has attracted increasing attention. However, the access of numerous DG will bring severe impact to the main grid, which limits the development of distributed power generation technology. The proposal and development of the microgrid can fully utilize the advantage of distributed generation. Voltage and frequency are the important indexes of power quality. The stability of the voltage and frequency plays a key role in ensuring the safety and reliability of the microgrid. To maintain the voltage and frequency of the islanded microgrids at the nominal values, the conventional secondary controls apply a centralized control structure. To make the microgrids operate economically, the centralized economic dispatch algorithms have been extensively studied. However, these centralized algorithms have some drawbacks, such as highly dependence on the communication network, weak robustness, and low expansibility. This thesis provides some solutions to these problems. The main contents are as follows:① This thesis presents a fully distributed control structure which consists of the primary controller, the distributed secondary voltage and frequency controller, and the distributed economic dispatch scheme. The control structure can significantly decrease the amount of communication data and enhance reliability.② A distributed cooperative secondary control algorithm is presented. Different from the conventional secondary control algorithm, the proposed secondary control is fully distributed such that each bus only requires its own information and the information of its neighbors. The proposed approach can restore the voltage and frequency of DG to their nominal values in finite time.③ A distributed algorithm is presented to solve the economical dispatch problem with generating constraints. Different from the centralized economic dispatch algorithm, the proposed scheme is fully distributed such that each bus only requires its own information and the information of its neighbors. The proposed approach can minimize the total cost of generation while satisfying a set of constraints.