Quadrature Type Direct Power Flow Controller

In order to improve the stability of the power power grid and it’s ability to transmit electricity,a novel flexible AC transmission system of direct power flow controller(DPFC)was proposed.When DPFC is installed to the power grid,it can adjust the amplitude and phase of the grid voltage,so that it can control the active and reactive power in the grid thereby improving the stability and power transmission capacity of the grid.DPFC is a single-stage power converter that only contain Buck AC converters,and its circuit structure does not contain DC energy storage element,thereby avoiding the failure rate caused by the DC energy storage element in the equipment.DPFC has various forms and multiple topologies.In this paper,the topology,working principle and control strategy of quadrature type direct power flow controller are studied in detail.Aiming at the topology and working principle of the quadrature type direct power flow controller,a prototype has been manufactured and experimental verification was performed.Experiments demonstrate the adjustment waveforms of the phase and amplitude of the grid voltage when the compensation voltage output by the quadrature type direct power flow controller is in different adjustment regions,after the measurement of the experimental waveforms,the results were almost the same as the theoretical calculations,which proved the theoretical correctness of the quadrature type direct power flow controller.In addition,to reduce the voltage stress of the components in the main circuit of the quadrature type direct power flow controller and to use it in more high voltage power grid,this article also proposes multilevel conversion in the main circuit of the quadrature type direct power flow controller.The topology,working principle and control strategy of quadrature type direct power flow controller whose main circuit is a three-level conversion circuit are given.The simulation results verify the correctness of the theoretical study of the three-level quadrature type direct power flow controller.