Research On Main Circuit Topology And Modulation Of HVDC-Hight

The HVDC-Light overcomes the inherent defects of the conventional HVDC,it can enhance the stability of the exchange system, reduce system losses, recoverfast after the accident, and facilitate electricity trading functions. The main circuittopology of inverter related to the system operating characteristics and the voltageand power levels. The traditional two-level and three-level voltage source converterrequire high dynamic and static pressure characteristics of power electronic devices.This will impact the HVDC-Light technology development to a higher power rating.New converter topology and its modulation are mode to be studied.Modular multi-level converter improves the output voltage level number byincreasing the number of sub-module. It can be easily extended to higher voltageand power levels, and also it’s able to use more mature standard components suchas industrial pressure capacitance and standard AC adapter, which are more flexibleand practical. This article selects modular multi-level inverter as the main circuittopology of the HVDC-Light and study the modulation mode control strategy. Themain contents of this article are as follows:1、Analyze and compare a variety of inverter main circuit topology and severalmulti-level modulation, considers that the modular multi-level inverter topology ismore suitable for the HVDC-Light technology.2、Study the steady-state characteristics of the HVDC-Light, decompose itscontrol system, and focus on the converter valve level control strategy. Thenanalyze the working principle and mathematical modeling of modular multi-levelconverter.3、Investigate the technical difficulties of modular multi-level inverter for theHVDC-Light system, Propose a design method of main circuit parameter, as well assub-module capacitor pre-charging and capacitance voltage balancing controlstrategy.4、 Analysis the principle of carrier phase-shifted SPWM, explore thefeasibility for modular multi-level inverter. Then propose a new type of carrierphase-shifted SPWM method, which is verified by simulation.5、Propose a implementation scheme of experimental system, based on the combination of DSP and FPGA. The hardware design of circuit diagram andsoftware design of process flow chart is also given.