Research On Calculation Method Of Modular Multilevel Converter Loss Based On Junction Temperature Estimation

At present,there are many calculation methods for the loss of the modular multi-level converter,but both of them are complicated to calculate and lack the accuracy of the calculation results.In this paper,in order to calculate the loss of modular multilevel converter more quickly and concisely,by first analyzing the advantages and disadvantages of the existing loss calculation methods,by introducing the equivalent analysis method of full-bridge sub-module loss,Full/Half-bridge hybrid topology MMC loss problems classified as half-bridge topology MMC loss problem.In addition,based on the simulation of the time domain method,a junction temperature calculation model is established.Based on the model,the junction temperature calculation method is proposed.Based on the analysis of junction temperature and loss characteristics of the device,a simplified calculation method is proposed based on the method.That is,the estimated junction temperature calculation method,and derive the corresponding loss calculation method.In order to analyze the accuracy of the proposed method,the loss was measured by setting up the valve platform of the converter to run the test platform.Through the measurement principle,the type of measurement test,the measurement of test parameters,measurement acquisition system for the measurement of the system description,and gives the test results.Finally,the loss calculation is carried out by the junction temperature feedback calculation method and the junction temperature prediction calculation method,and the accuracy and feasibility of the junction temperature prediction method are verified.Finally,the loss characteristics of ±800kV/5000MW converter are analyzed.Starting from the simulation model of the converter,the loss characteristic of the converter under the actual operating conditions is analyzed by the method of estimated junction loss.In order to further analyze the loss characteristics of the system,As well as the impact of the algorithm on the loss characteristics and avoiding any accidental effects due to the calculated single-run condition.The loss characteristics of the converter are analyzed from three aspects of the system operating conditions,the system reactive power and the switching frequency of the converter.At the same time,the correctness of the simplification of the junction temperature estimation method is verified.