Abstract: A method and an arrangement in connection with a wind power plant, an electric drive of the wind power plant comprising two or more partial converters in parallel, which constitute a frequency converter of the electric drive, and each partial converter comprising a mains converter part, of which the nominal power of at least one differs from the nominal power of other mains converter parts, and in the method there is selected for use the smallest possible, individual mains converter part required by an operating point of the wind power plant, or a combination of mains converter parts.

Abstract: A method and arrangement in connection with an inverter that comprises several power semiconductor components and a control apparatus arranged to control them is disclosed. The method comprises the steps of determining the temperature or an electric quantity affecting the temperature of one or more power semiconductor components, determining the change of the temperature or an electric quantity affecting the temperature of one or more power semiconductor components, and controlling with the control apparatus the power semiconductor components in response to both a control quantity to generate an output voltage and the change rate of the temperature or a quantity affecting the temperature of the power semiconductor components to reduce temperature variation by slowing down the temperature increase rate as the temperature or quantity affecting the temperature increases and by slowing down the temperature decrease rate as the temperature or quantity affecting the temperature decreases.