Comparative Study of PQ and DQ Theory for Diode Clamped Multilevel Inverter based D-STATCOM

The heavy engineering industries have conventionally opted for higher ranges of distribution voltage to cater the demands of high power load. However, some of the loads are demanding high power ratings at medium voltage levels. The conventional inverters operating in this range are two level inverters. These inverters despite of being economical, requires high DC link voltages and lags behind for the power quality parameters. For high-power, mediumvoltage applications, multilevel inverters are deployed in industrial applications. The multilevel inverters are constructed in variety of configurations and levels according to the load requirements. These multilevel inverters are also used in power quality enhancement devices like active filters and STATCOM due to their inherent advantages as reduced harmonics contents, reduced voltage stress on switching devices and minimized losses in the switching. This paper focuses on implementation of D-STATCOM with diode-clamped multilevel inverter (DCMLI). A comparative study of DCMLI based D-STATCOM with synchronous reference frame (SRF often referred as DQ) theory and instantaneous reactive power (IRP often referred as PQ) theory is presented with MATLAB simulations.