A method of protecting a converter of a wind turbine, wherein the converter is coupled to a generator of the wind turbine to perform conversion of electrical power produced by the generator, the converter comprising plural semiconductor components that are operational to provide the conversion of the electrical power, wherein the method comprises: performing a step of estimating an actual junction temperature (T j) of at least one of said semiconductor components by - determining a current (I 1, I 2, I 3) in the converter associated with power loss in one or more of the semiconductor components; - estimating power loss (P L) associated with the one or more semiconductor components based on the determined current and on a state (sw) of the one or more semiconductor components; and - using a thermal model (600, 700) of the one or more semiconductor components to estimate the actual junction temperature (T j) of at least one of the one or more semiconductor components based on the estimated power loss (P L); characterised by the step of estimating the actual junction temperature (T j) is repeatedly performed, wherein a time period corresponding to a step size between subsequent steps of estimating the actual junction temperature (T j) is smaller than 1/10 of the period of an AC voltage output by the converter; and if the estimated actual junction temperature (T j) exceeds a predetermined temperature threshold, triggering a protection mechanism that is configured to reduce the actual junction temperature (T j) of the at least one semiconductor component, wherein the determining of a current in the converter comprises determining an operating current (I 1, I 2, I 3) of the converter that is indicative of the current through the at least one semiconductor component, wherein the operating current of the converter is measured if the operating current lies within a working range of a respective current sensor (141, 142, 143) and wherein the operating current is estimated based on operational parameters of the converter if said operating current lies outside the working range of said current sensor (141, 142, 143). performing a step of estimating an actual junction temperature (T j) of at least one of said semiconductor components by - determining a current (I 1, I 2, I 3) in the converter associated with power loss in one or more of the semiconductor components; - estimating power loss (P L) associated with the one or more semiconductor components based on the determined current and on a state (sw) of the one or more semiconductor components; and - using a thermal model (600, 700) of the one or more semiconductor components to estimate the actual junction temperature (T j) of at least one of the one or more semiconductor components based on the estimated power loss (P L); characterised by the step of estimating the actual junction temperature (T j) is repeatedly performed, wherein a time period corresponding to a step size between subsequent steps of estimating the actual junction temperature (T j) is smaller than 1/10 of the period of an AC voltage output by the converter; and - determining a current (I 1, I 2, I 3) in the converter associated with power loss in one or more of the semiconductor components; - estimating power loss (P L) associated with the one or more semiconductor components based on the determined current and on a state (sw) of the one or more semiconductor components; and - using a thermal model (600, 700) of the one or more semiconductor components to estimate the actual junction temperature (T j) of at least one of the one or more semiconductor components based on the estimated power loss (P L); characterised by the step of estimating the actual junction temperature (T j) is repeatedly performed, wherein a time period corresponding to a step size between subsequent steps of estimating the actual junction temperature (T j) is smaller than 1/10 of the period of an AC voltage output by the converter; and if the estimated actual junction temperature (T j) exceeds a predetermined temperature threshold, triggering a protection mechanism that is configured to reduce the actual junction temperature (T j) of the at least one semiconductor component, wherein the determining of a current in the converter comprises determining an operating current (I 1, I 2, I 3) of the converter that is indicative of the current through the at least one semiconductor component, wherein the operating current of the converter is measured if the operating current lies within a working range of a respective current sensor (141, 142, 143) and wherein the operating current is estimated based on operational parameters of the converter if said operating current lies outside the working range of said current sensor (141, 142, 143).