Full Phase Angle Range Adjustable Direct Power Flow Controller With Unipolar Modulation

Direct power flow controller(DPFC)can realize the independent and continuous control of active power flow and reactive power flow without high-capacity DC energy storage elements by cascading amplitude and phase adjustable compensation voltage into the power grid.In order to solve the problem that the existing DPFC needs to add an electrical selector switch or power conversion unit to realize 360° regulation of compensation voltage,a full phase angle range adjustable direct power flow controller with unipolar modulation is proposed in this paper.First,the topology of the bridge Buck AC converter is proposed,its operating modes and output-output relations are analyzed,and the control strategy is given.The circuit topology of the full phase angle range adjustable direct power flow controller with unipolar modulation is derived and constructed using the bridge Buck AC converter circuit as the power conversion unit,and its operating principle is elucidated in detail,and the control strategy of the full phase angle range adjustable direct power flow controller with unipolar modulation is given.The circuit structure is verified by using Saber simulation software,and it is shown that the compensating voltage with adjustable amplitude and phase over the full phase angle range of 360° can be obtained by controlling the duty cycle states of the left and right bridge arms of the bridge Buck AC converter unit only.In order to verify the dynamic response of the controller proposed in this paper,a closed-loop voltage simulation based on sliding mode control is designed,and the simulation model is built using MATLAB software.Then,the relationship between the control parameters and the regulation interval selection is analyzed in detail,the judgment conditions for the regulation interval selection are given,and two different operating modes are given in the same regulation interval,and the characteristics of the different operating modes are analyzed.A block diagram of the final control strategy of the full phase angle range adjustable direct power flow controller with unipolar modulation is given,and one of the sub-modules is used as an example for detailed analysis.Finally,a schematic prototype of the full phase angle range adjustable direct power flow controller with unipolar modulation is developed,and the overall design scheme is introduced in detail.The experimental platform of the principle prototype is built to verify the theoretical analysis of the control circuit and the main circuit respectively,and the experimental waveforms of different regulation intervals are given to confirm the correctness and feasibility of the theoretical analysis through the analysis of the experimental waveforms.