Restoration of Normal Frequency Affected by Small Load Variations Through HVDC Link Using Neuro-Fuzzy Approach

Abstract— HVDC power transmission is coming up with merits to replace the EHV-AC systems. The controller inverter operation can successfully regulate the power in HVDC link leading to fulfillment of power demand in A.C. networks caused by sudden rise in loading. Since overloading and unloading both lead to the departure of operating frequency below or above normal, its control for normalization is exercised through control of power flow in HVDC Link. Also the same is achieved by adjusting firing delay angle intelligently. This paper aims at providing automation to frequency normalization after it has undergone changes from normal value of 50 Hz, due to sudden and sustained increase in load or due to working of generators at increased loads in H.V.D.C transmission systems. It is planned to automate the restoration of departed frequency to normal value by arranging the change in firing delay angle i.e. α of the converter of H.V.D.C. link, till the increased load demand is met with. An adaptive control system has been devised which controls the firing delay angle on the basis of decisions given by a fuzzy controller. Also the fuzzy controls are decided by the departure in frequency from normal. The results have been found to be encouraging.