Distributed Real-Time Optimal Power Flow Control in the Smart Grid

Conventionally, power system has a hierarchical control structure including primary, secondary, and tertiary controls. The drawbacks of this hierarchical scheme are manifest: 1) it lacks flexibility and scalability, which is against the trend towards an open access power system; 2) load forecast as the basis of tertiary control could be inaccurate and infeasible, especially in micro-grid for example; 3) as the penetration of renewable energy increases, the relatively long time-scales of secondary and tertiary controls cannot accommodate to more severe power fluctuation within the system. To avoid these drawbacks, a distributed realtime optimal power flow control strategy is introduced in this paper. With the aid of up-to-date smart grid technologies such as two-way communication and distributed sensor, the proposed approach can avoid the need of load forecast and achieve the same objective as hierarchical control with a feedback mechanism in real time, that is to recover the nominal system frequency and maintain the active power of the generators close to the optimal operational condition in the presence of any disturbance. Convergence of the proposed approach is analytically proved. Simulation results in a 34-bus islanded micro-grid and the IEEE 118-bus bulk power grid validate the effectiveness and efficiency of the proposed approach.