Control tuning methodology for modular multilevel converter-based STATCOM

The application of modular multilevel converters (MMC) in medium voltage static synchronous compensators (STATCOMs) has been investigated in recent years. A huge challenge for MMC-STATCOM is to compute the gain of the controllers. Therefore, the contribution of this paper is the proposal of a control tuning methodology for MMC-STATCOM. For this purpose, the control and tuning strategies are presented. Since MMC-STATCOM can employ different modulation strategies, two distinct modulation strategies are considered: nearest-level control, with variable switching frequency; and phase-shifted carrier pulse-width modulation, with fixed switching frequency. Moreover, the proposal was validated through simulation and an experimental platform. The results indicate that the power response follows the reference, besides supplying the internal losses of the converter. The 10% ripple tolerance of the submodule voltages is respected in steady state for both modulation strategies. Moreover, the 5% total demand distortion (TDD) limit recommended by the Institute of Electrical and Electronics Engineers (IEEE) standard is attended. These results demonstrate the effectiveness of the controls employed. A straightforward methodology for the control tuning of modular multilevel converter (MMC)-static synchronous compensators (STATCOMs), which facilitates the testing and validation of techniques in these converters.Experimental validation of the control tuning methodology in a laboratory MMC setup.Evaluation of the proposal applied in different designs and voltage levels and distinct modulation strategies.image