Investigation on the effectiveness of DSTATCOM in distribution networks

Abstract

Utility and customer-side disturbances result in terminal voltage fluctuation, transients and waveform distortions on the distribution system. In recent years, power quality engineers are becoming increasingly concerned over the quality of electrical power. In modern industries, load equipment uses electronic controller, which are sensitive to poor voltage quality and will shut down if supply voltage is depressed and may mal-operate in other ways, if harmonic distortion of the supply voltage is excessive.Also the widespread use of electronic equipment, such as information technology equipment, adjustable speed drives (ASD), arc furnaces, electronic fluorescent lamp ballasts and programmable logic controllers (PLC) have completely changed the electric loads nature.Due to the non-linearity of these loads, they cause disturbances in the voltage waveform. In modern industries, FOC induction motor drives and DTC induction motor drives are used, which produce distortion in load current and harmonics distortion. It is expected that a utility will supply a low distortion balanced voltage to its customers, especially those with sensitive loads. A Distribution Static Compensator (DSTATCOM) is a voltage source converter (VSC) based custom power device for the enhancement of power quality due to its quick response, high reliability and nominal cost. A DSTATCOM is connected in parallel with the system to compensate voltage sag, voltage swell, voltage unbalance and harmonics. When a DSTATCOM is associated with a particular load, it injects compensating current, so that total demand meets the specifications for utility connections. DSTATCOM generates capacitive and inductive reactive power internally. In this work, DSTATCOM has been modeled and simulated in MATLAB/SIMULINK environment. The performance of DSTATCOM has been analyzed for linear loads, static non-linear loads, DTC induction motor drive and FOC induction motor drive using dqo transformation technique. DSTATCOM has been found to regulate PCC current under varying load conditions and load unbalancing.The control technique implements a dqo transformation which starts from the difference between the load current and reference current that determines the reference voltage of the inverter (modulating reference signal). The simulation results show that the DSTATCOM effectively compensate load current harmonics.