Research On Single-Phase Cascaded Rectifier Based On The Modified T-Type Five-Level Topology

In modern power electronic converters,cascaded converters are proposed and widely used in high voltage and high power applications.Taking the traditional H-bridge topology as the basic module unit,the three-level topology has advantages in obtaining the number of levels and reducing the voltage stress on the switch.This paper studies a cascaded singlephase rectifier based on a modified T-type three-level topology as a cascade unit.Firstlly,the basic working principle of the modified T-type three-level topology is introduced,and its similarities and differences with the traditional T-type three-level topology are analyzed.The mathematical model of the modified T-type three-level singlephase rectifier is established and the state space models in different coordinate systems are derived.The dq decoupling control is adopted to realize the current inner loop to follow the given voltage outer loop without static difference.The main parameters of the control system are designed.Secondly,the midpoint balance problem of the modified T-type three-level topology is studied in detail.This paper introduces the application of single-phase unipolar three-level carrier sinusoidal PWM(TLC-SPWM)in the modified T-type three-level topology,discusses the problem of implementing neutral point potential balance in PS modulation technology based on zero-sequence component injection method,and gives direct Redundant vector replacement method,simulation verification by Matlab.Then,the reasons for the unbalanced DC-side voltage of each module of the cascaded rectifier are explained.The stable operating conditions of cascaded rectifiers under different voltage equalization strategies are introduced,and the constraint relationship between the loads is derived.The relationship between the feasible region of the DC side load of each module and the relevant parameters in the main power circuit is analyzed in detail,and simulation verification is performed by Matlab simulation software.Finally,taking a two-module cascade as an example,an experimental prototype of a single-phase rectifier with the modified T-type three-level topology cascade is developed,and the parameter design and selection of main circuit components are completed.Complete peripheral hardware circuit design and software design based on DSP chip TMS320F28335.The experimental results verify the correctness of the theory in this paper.