Load frequency control of an inter-connected system with DC tie-lines and AC-DC parallel tie-lines

The authors examine the effect of DC tie-lines and AC-DC parallel tie-lines in a multi-area interconnected system consisting of hydro and thermal generation units provided with conventional integral controllers. Separate studies were made for each case and results are compared with a pure AC tie-line multi-area system. A conventional integral controller is used for all the studies demonstrated. The DC tie lines and AC-DC parallel tie-lines in an inter-connected power system give much better dynamic performance by bringing all the desired system variables to steady-state faster than in the existing AC tie-line inter-connected systems and quite smoothly. Eigenvalue analysis supports the results