Capacitor Voltage Control in a Cascaded Multilevel Inverter as a Static Var Generator

The widespread use of non-linear loads and power electronics converters has increased the generation of non-sinusoidal and non-periodic currents and voltages in power systems. Reactive power compensation or control is an important part of a power system to minimize power transmission losses. Given a modulation index, the switch times can be chosen to achieve the fundamental while eliminating specific harmonics. However, the resulting total harmonic distortion (THD) depends on the modulation index. This work considers the control of the DC capacitor voltage in such a way that one can operate at the modulation index which results in the minimum THD. This paper presents the development of specific control algorithms for a cascaded multilevel inverter to be used for static VAr compensation