DSTATCOM for Power Quality Improvement

Adistribution system suffers from current as well as voltage-related power-quality (PQ) problems which include poor power factor distorted source current and voltage disturbances. A DSTATCOM connected at the point of common coupling (PCC) has been utilized to mitigate both types of PQ problems. When operating in current control mode (CCM) it injects reactive and harmonic components of load currents to make source currents balanced sinusoidal and in phase with the PCC voltages. In voltage-control mode (VCM) the DSTATCOM regulates PCCvoltage at a reference value to protect critical loads from voltagedisturbances such as sag swell and unbalances. However the advantages of CCM and VCM cannot be achieved simultaneously with one active filter device since two modes are independent of each other. In CCM operation the DSTATCOM cannot compensate for voltage disturbances. Hence CCMoperation of DSTATCOMisnot useful under voltage disturbances which is a major disadvantage of this mode of operation.