A method of controlling a power unit having a plurality of converter modules coupled in parallel, is configured to convert DC into AC voltages or AC into DC voltage. The method includes (a) receiving a control value for each phase of each converter module, (b) obtaining a set of phase current values for each converter module, (c) generating a compensation value for each phase of each converter module based on the set of phase current values and a set of stored data, the set of data representative of non-linearity characteristics of the converter modules as functions of phase current value, (d) generating a compensated control value for each phase of each converter module based on the corresponding control value and compensation value, and (e) supplying the compensated control values to the respective converter modules. A controller, power unit, wind turbine, computer program and computer program product are similarly configured.