Application of D-STATCOM to mitigate high inrush current during start-up of three-phase induction motor

Abstract

This thesis presents the application of Distribution Static Compensator (D-STATCOM) to mitigate inrush current during start up three phase induction motor. Three phase induction motor draws high current during starting period and will from 6 to 7 times of the rated current of the motor. The effect of high starting current will cause severe damage to motor itself, especially overheating and making motor life expectancy short. In addition, the high starting current will cause the voltage of the power supply rapid drop and affect other devices’ running in the same power line. The purpose of this thesis is to demonstrate that a D-STATCOM is capable to mitigate inrush starting current during start up induction motor. The controller circuit of D-STATCOM has been simulated by using Power System Computer Aided Design (PSCAD/EMTDC) software. The research methodology of this project is to design D-STATCOM circuit which consists of Voltage Source Converter as a main circuit. The function of this circuit is to convert AC to DC and then invert DC to AC before transmit to the threephase power line. The circuit’s has a capability to absorb and inject the reactive and active of the power system which is to control the magnitude of the VSC output voltage. To compare the capability of the D-STATCOM, a Soft starter is developed. The Soft starter circuit is controlled by six thyristors. There were three methods which can be used such as starting the induction motor with direct start-up, starting the induction motor by connecting with the D-STACOM and starting the induction motor with Soft starter. The starting currents of these three methods were observed up to 30 milliseconds and compared. The analysis result shows that the D-STATCOM had mitigated inrush current during start-up induction motor up to 74% higher compared to direct start-up and 164 Ampere is the highest inrush current recorded while direct startup was 637 Ampere recorded. The D-STATCOM was compared with Soft starter to determine the ability of reducing inrush current during start-up induction motor. The result shows that the D-STATCOM had mitigated of 54.3% higher inrush current compared with Soft starter. Hence, the conclusion of this research is the D-STATCOM has a higher capability to reduce inrush current during start up the induction motor compared with Soft starter.