Study On Equivalent Test Circuit And Its Parameters For Light HVDC-flexible Converter Valve

Voltage Sourced Converter Based High Voltage Direct Current Transmission(VSC-HVDC)is a new generation of DC transmission technology following AC transmission and conventional DC transmission depending on its unique advantages in islanding and offshore platform power supply,power grid interconnection,new energy grid connection,and urban distribution network capacity enhancement.As a core equipment of VSC-HVDC transmission system,there are still many problems in the converter valve.Compared with the conventional DC transmission converter valve,the flexible converter valve with the same capacity level has large volume/weight,poor seismic performance and high cost.In the converter valve,the capacitor occupies the main volume and weight.So we can make the light-converter valve by improving the topology and control strategy of VSC-HVDC and improving capacity density of the capacitor in the sub-module.Converter is the key equipment of the light VSC-HVDC project.And the power electronic devices are very sensitive to voltage,current and temperature,which causes the operation reliability of the light converter valve low.Therefore,a series of tests must be carried out before the light flexible converter valve is put into operation to verify the correctness of its design and manufacture,which requires the establishment of corresponding test means.This paper focuses on the equivalent test technology based on light flexible converter valve.Firstly,the paper analyses the topological structure and working principle of the light flexible converter valve,and acquires the key stresses of the light converter valve based on Xiamen project,including voltage,current and thermal stress.Then this paper defines the equivalent test circuit of the ligh converter valve,and the operation mechanism of the test circuit are analyzed.The mathematical model and parameter design method of the test circuit are studied,and the main equipment parameters of the test equipment are determined.The simulation model of the test circuit is built in PSCAD/EMTDC simulation software to prove the correctness and equivalence of the test circuit.Finally,the paper introduces the MMC sub-module test system,and the voltage and current are established for the existing flexible converter sub-module in Yue Project through the test system.The stress of the test voltage,current is compared to light converter valve stress and further verify the correctness and equivalence of the test circuit.