Abstract: An apparatus for performing the following. The apparatus maintains, in a memory, information on a computational model for thermal behavior of layers of an insulated-gate bipolar transistor, IGBT, module. The apparatus obtains measurements of the dissipated power at the semiconductors and the ambient temperature and determines one or more current values of one or more temperatures of the IGBT module based on a switching delay of the IGBT module. The apparatus calculates a current estimate of a joint state-parameter space of the computational model using a Bayesian filter and the computational model taking as inputs the dissipated power and the ambient temperature. The joint state-parameter space includes the one or more temperatures, one or more thermal loss parameters and one or more wear parameters. The one or more current values of the one or more temperatures are used as observations in the Bayesian filter.

Abstract: Techniques for monitoring and/or operating a power system asset are provided. A series of sets of first model parameter values (71-73) of a power system asset model is determined from data obtained by measurements. The series of sets of first model parameter values (71-73) is used to determine a set of second model parameter values (79) of a parameter evolution model different from the power system asset model. The parameter evolution model describes an evolution of one, several or all first model parameter values (71-73) of the power system asset model. An output is generated in dependence on at least one of the sets of first model parameter values (71-73) of the power system asset model and the set of second model parameter values (79) of the parameter evolution model.