Combining local and optimised power flow remedial measures in bulk reliability assessment

In traditional Newton-Raphson power flow algorithms, the terminal and remote bus voltages are obtained using a local control logic, i.e. reactive power and LTC taps are adjusted to meet pre-specified voltage settings. On the other hand, most of the optimal power flows (OPF) utilised in available reliability programs adopt an optimised logic for voltage control, i.e. the voltage level is optimised inside the pre-specified bounds, meaning that new settings can be calculated in order to avoid or minimise load shedding. However, in several practical situations this is not a feasible approach, due to operational constraints. Local voltage control logic is introduced into the nonlinear interior point (IP) optimal power flow of a bulk power system reliability evaluation program in order to represent actual operational practices with increased accuracy. The impact of these two voltage control logics on the reliability indices is then analysed using the new IEEE Reliability Test System (RTS-96) and an 89-bus network derived from the North/Northeastern Brazilian System (NNBS).