A comparison of two methods of estimating losses in the Modular Multi-Level Converter

The transmission losses in an HVDC interconnection represent lost revenue to the purchaser (usually a transmission Utility) and are therefore heavily penalised. At the bid stage, the purchaser calculates the Net Present Value (NPV) of the revenue lost due to power losses over the operating life of the system (typically 30 years) and uses this to derive a loss capitalisation value which is typically in the range of 4000€/kW. Bidders are required to calculate and guarantee the power losses of the converter station under certain idealised operating conditions. Presently there is no agreed method for calculating the losses for the Multi Modular Converter (MMC). This paper presents a mathematical analysis for calculating both the conduction and switching losses for a VSC HVDC station using the MMC topology, comparing it to an equivalent model based on MATLAB/Simulink model. The results show very good agreement for conduction loss; however the error for the switching loss are much more significant and require further development.