Direct Power Flow Controller With Continuous Full Regulation Range

In order to enhance power flow control in power transmission, a new simplified structure of direct power flow controller with continuous full regulation range (F-DPFC) was proposed. It has only one-stage power conversion and comprises of a three-phase transformer in parallel and a three-phase transformer in series with grid, three single-phase full-bridge ac units, and a three-phase filter. Compared with the previous DPFC, the proposed one dispenses with two complex three-phase selection switches, which are connected to a high-voltage grid directly, and replaces buck-type ac units with full-bridge-type ac units. Then, the limit of its duty cycle is extended from [0, 1] to [−1, 1], providing a continuous 360° adjustment range of compensation voltage. Within a large complete zone replacing six separate zones, the proposed F-DPFC can regulate the amplitude and phase angle of grid node voltage, respectively and simultaneously, and the active and reactive power flow in the grid can be controlled smoothly and effectively. The new structure is easy to achieve modular expansion and enables it to operate under high-voltage and power conditions. Its structure and operational principle were analyzed in detail, and a prototype was developed. The experimental results verified the feasibility and the correctness of the theoretical analysis.