Enhancement of power quality using three phase DSTATCOM for variable load

The distribution static compensator (DSTATCOM) is used for enhancement of power quality in power distribution network with unbalanced, nonlinear and variable loads. The dc link capacitor voltage is directly affected by any alteration made in the load. The sudden decrease of load would result in an increase in the converter dc link voltage above the reference value, where as a sudden increase in the load would reduce the dc link capacitor voltage below its reference value. For proper operation of DSTATCOM requires variation of the DC link capacitor voltage within the prescribed limits. Right from the beginning, a proportional integral (PI) controller has been used to maintain the converter dc-link capacitor voltage to the reference value. Despite of it, the transient response of the conventional PI controller is still slow. In this paper, a fast acting dc-link voltage controller based on energy of the converter dc-link capacitor is proposed. Reference current is generated based on instantaneous symmetrical component theory for improving power quality in the power distribution network. Mathematical expressions are given to design the fast-acting dc-link controllers to achieve the fast transient response. A simulation study of the proposed method has been carried out using MATLAB simulation software.