| With the development and utilization of various forms of energy and the rapid development of power electronic conversion technology,wind and light are the typical representatives,and the distributed energy using power electronic devices is connected to the power grid.The structure of the power grid is becoming more and more complex,and the power load is gradually becoming more and more complex,diversified and sensitive,resulting in various types of power quality problems becoming more and more serious and coexisting.In order to solve many kinds of power quality problems in power grid at the same time,a voltage reconfiguration cascaded power quality integrated treatment device based on source load decoupling is proposed in this paper.The circuit topology and parameter design of the device are studied,and the corresponding modulation and control methods are proposed.The treatment effect of the device is verified by real-time simulator.Firstly,the main circuit structure of the voltage reconfiguration cascaded power quality integrated treatment device is introduced.The device adopts AC-DC-AC back-to-back topology.The rectifier side is used to convert the system power supply of the governed area with a variety of power quality problems into DC,and then invert the AC voltage required by the load side through the H-bridge converter,in which the DC link is used to isolate the power side and load side.In order to apply the device to the system with higher voltage level,a chain structure of cascaded power units is proposed.The power supply is divided into multiple channels by a phase-shifting converter and used as the input of the power units.The modulation strategy and parameter design of the device are given.Then,according to the characteristics of the device topology,in order to ensure the high-quality power supply level to users,the double closed-loop control strategy of split phase constant voltage is proposed.The voltage outer loop adopts the repetitive control theory,which can realize the tracking of the periodic signal without static difference,and ensure the stable performance of the device.The inner current loop is used to improve the dynamic response speed of the system.In order to further improve the reliability of the device,the reliability improvement scheme of dual power supply and energy storage is proposed.Through PSCAD/EMTDC simulation software,a variety of ty pical power quality problems are simulated,and the treatment effect of the device is verified.Finally,in order to further verify the device,a hardware in-loop verification platform is built based on NI real-time simulation system,including a host computer,a real-time simulation case,control cases and transfer board.The human-computer interaction interface is designed in the PC,which can realize the switching of various power quality conditions and the real-time monitoring of related output waveforms.According to the test results of harmonic,voltage sag,three-phase imbalance,voltage fluctuation and other power quality conditions,the device has good treatment effect for a variety of power quality problems,which verifies the effectiveness of the device. |
