This paper proposes a voltage-reactive power optimization, which is an integrated system based on centralized optimization and distributed control, to confine the action numbers of control devices. The system includes VQC (voltage and reactive power control system) and the optimal power flow calculation in the master station. By using the fractal theory, the original data in the range of nonperiodic cycles are divided into several time-intervals. After this processing, the optimal points are obtained by optimal power flow in every segment. Based on the load fluctuation rate, in every period, the voltage / reactive power limits of nine area figure are set. As the load fluctuation rates changed in every segment, voltage / reactive power limits are different. And the tap changers and switchable capacitor banks are regulated according to each upper/lower limits and the optimal points. Furthermore, correctness and effectiveness of the proposed method have been confirmed. And the simulation results show that it not only reduces power losses but also restricts the action numbers of control device.

Three-phase active power filter (APF) is a typical switched affine system for the action of the power switch. The conventional method of modeling was based on the linear system theory. In this paper, a novel control procedure for the three-phase APF based on the switched affine system and quadratic stability is proposed. Firstly, the three-phase APF is built as switched affine system model. Based on the sufficient condition for quadratic stability of convex combination, the common Lyapunov function is selected. Then, the switched rules can be defined to assess quadratic stability of the switched system, thus realizing the control of the compensation current and the DC side voltage. Finally, simulation results have good agreement with the theory analysis, and demonstrate the validity of this approach.