HARDWARE Implementation of Step-Switched SVCs to Correct Power factor and Mitigate Harmonics for Large DC Variable Loads

The objective of this paper is to develop and implement a complete system for reactive power compensation in railways or high DC power consuming industries. Very high current harmonics are generated, when AC supply is converted to DC to run DC machines, e.g., railway locomotives. Generally, for such applications, static VAr compensators (SVC) are used in combination with passive harmonics filters for mitigating different orders of harmonics. By default, such systems take power factor to high leading side, which must be corrected. To achieve acceptable results, manufacturers switch large inductors and feed chopped voltage waveform to achieve required inductive reactive power to compensate the leading reacting power present at any time in the SVC. This is done at high voltage using thyristors or GTOs, i.e., 11 kV or 33 kV. It is technically a complicated, very expensive technology and needs highly skilled engineers to run and maintain such system. Looking at those problems, better, reliable and technically superior solution is developed to give desired results at much reduced cost. A hardware prototype is developed for 433 V, three phase, 20 A load to obtain satisfactory experimental results.