Voltage Regulation Method for a Rotary Power Flow Controller Based on the Impedance Regulation Principle

A rotary power flow controller (RPFC) that consists of rotary phase shifting transformers can be used for voltage regulation to address the problem of voltage crossing limit caused by high-penetration photovoltaic integration. First, this study presents an impedance dynamic adjustment model for RPFC by combining its topology and working principle. Second, a voltage control strategy based on impedance adjustment, wherein line voltage and the power factor are used as control input, is proposed. This strategy calculates the set-point values for the dq-axis components of the RPFC output voltage on the basis of the deviations of user-side voltage amplitude and line power factor. Then, it combines and converts them into two target values for rotation angles. The actual and target values of rotation angles are used to quantify the duty cycles of RPFC servomotors, achieving closed-loop coordinated control of the two rotation angles’ speeds to maintain the voltage level at the user side. Finally, experimental analyses are conducted to verify the feasibility and effectiveness of the proposed scheme, including the impedance compensation characteristics of RPFC and the control of user-side voltage and the line power factor under varying voltage set points and load power disturbances.