The invention discloses a
life evaluation method for a modular multilevel converter (MMC). The
life evaluation method comprises the following steps: reading year-round temperature data of a running
natural environment of the MMC and power
data input into the MMC; performing analytic calculation on the average value and the effective value of the current of sub-modules IGBT and
Diode of the MMC; calculating the average loss power Ploss,T and Ploss,D of the sub-modules IGBT and
Diode of the MMC within the
fundamental frequency period; calculating the average temperature rise Tja of a
semiconductor device within the working frequency period by use of a Forster
network model to obtain the average
junction temperature value Tj of IGBT modules (IGBT modules, IGBTs, including IGBT and
Diode); modifying fitting calculation of loss of the IGBTs according to the average
junction temperature of the IGBTs; calculating the extreme values of the function temperature within the working frequency and counting the year-round
fundamental frequency junction temperature cycle; counting fluctuation information of the year-round low-frequency junction temperature; and calculating the failure number Nf of the
fundamental frequency and the
low frequency of the semi-conductor device by use of a Bayerer life model, and obtaining the life of the MMC in combination with operation conditions. The
life evaluation method can reliably forecast the life of the MMC, can effectively improve the forecasting calculation speed through obtaining an analytical expression of both current and the junction temperature, and has the characteristics of project operational capability and the like.