Design and implementation of a single-phase cascaded H-bridge multi-level converter based statcom

Reactive power control is very crucial in terms of voltage stability and power quality of electrical power systems. In steady-state, during heavy loading conditions, the system voltage may be lower than its reference value, or it might be observed an increase in system voltage during light loading conditions. In either of these cases, especially shunt reactive power support is necessary to restore the system. STATCOM is one of the most versatile member of FACTS devices that is used for VAR compensation and voltage control. When compared to old compensation technologies such as fixed capacitor or SVC, STATCOM has many advantages such as faster response and small size. In this thesis, a low-power single-phase STATCOM prototype has been modelled, designed and practically implemented. The proposed STATCOM comprises of a multilevel converter having three cascaded full H-bridges. It is aimed that the proposed STATCOM can operate both in capacitive and inductive modes. It is shown by both simulations and experiments that the STATCOM injects and absorbs reactive power into/from single-phase 220V grid. A closed loop control scheme has been implemented so that the STATCOM can generate the desired amount of capacitive/inductive reactive power. Some optimization methods have been used to determine many controller parameters which provide good dynamic performance to STATCOM.