Research On Topology And Control Strategy Of New Dynamic Voltage Restorer

With the continuous expansion of the construction scale of smart grid,a large number of nonlinear power electronic equipment and impulsive loads are connected to the grid and have brought many power quality problems,among which voltage sag is the most frequent and harmful.Dynamic Voltage Restorer(DVR)has low operating cost,high flexibility in design and application,and can quickly respond to and compensate various voltage disturbances in the power system.It is the most economical and effective transient power management equipment at present.According to the different compensation methods,it can be divided into series dynamic voltage restorer and parallel dynamic voltage restorer.This thesis selects the parallel dynamic voltage restorer as the research object,and studies the voltage sag detection algorithm and the topology and control strategy of the parallel dynamic voltage restorer.Firstly,the working principles of several conventional voltage sag detection algorithms are analyzed,and the three-phase voltage dq detection algorithm based on instantaneous reactive power,single-phase instantaneous voltage dq detection algorithm,single-phase instantaneous voltage αβ-dq detection algorithm and instantaneous voltage based on derivative transformation αβ-dq detection algorithm,and simulation verification.The transient voltage based on derivative transformation is verified by simulation αβ-dq detection algorithm has strong real-time and high accuracy in detection and tracking,which effectively improves the working compensation performance of parallel DVR.Then the topology and working principle of parallel DVR are analyzed in detail,and the mathematical models of bidirectional Buck/Boost DC converter and three-phase three-wire voltage source inverter are built,and their small signal models are obtained by linearization.Considering the particularity of the parallel DVR topology,the control strategy of the front and rear stage hierarchical control is proposed and the simulation model is built.The double closed-loop control system of the front stage bidirectional Buck/Boost converter is established,and the rear stage is the double closed-loop control system based on feedforward decoupling of the three-phase three-wire voltage source inverter.A 5k W parallel DVR prototype experimental platform is built,its working characteristics are analyzed,and the stability and effectiveness of the dynamic voltage restorer model are verified.Finally,a dual-coupled inductive bidirectional high gain DC/DC converter topology is proposed,its topology and working principle are described,and it is applied to the improved high gain DVR system.Compared with the traditional parallel DVR,its energy storage link is more flexible.The simulation model and prototype experimental platform of the dual-coupled inductive bidirectional high gain DC/DC converter are built,which verify that the converter effectively reduces the input current ripple and realizes bidirectional high gain energy transmission.At the same time,the simulation model and prototype experiment platform of the improved high-gain DVR are also built,which verifies that the response of the prototype to the voltage sag is quickly compensated,and the design purpose is achieved.There are 74 figures,7 tables and 93 references in this thesis.