Optimal Selection of the Average Capacitor Voltage for Variable-Speed Drives with Modular Multilevel Converters
In this study, an algorithm that provides the optimal selection of the average capacitor voltage for M2Cs. The solution is based on a geometrical interpretation that allows formulating a polynomial equation, which has analytical solutions. Arithmetic examples for a certain M2C and IM setup are shown and experimentally confirmed. The algorithm presented here is very general and can be used in any application involving M2Cs, irrespective of the power/voltage level. The benefits of estimating the operating points with this method are that it does not cause any voltage or current overrating of the converter components, it does not increase the conduction losses, it decreases the switching losses, and it creates a very high-quality current waveform, even when the required output voltage is fairly small.