Active and reactive power flow for multiarea systems on automatic generation control in the presence of rapidly changing loads

In this paper, the control area dynamics of power systems on automatic generation control are revisited. The role of reactive power flow between regions under automatic generation control is studied by review of simulations in which the reactive power flow is modeled/not modelled. The effect of transmission line loading is also studied. Reactive power control is accomplished in part by automatic voltage regulation, and reactive power resides in a control “loop” much in the same way as active power resides in conventional automatic generation control. An important observation of the analysis is that short term phenomena (e.g., peaks in tie line flow after a load disturbance ΔP = j ΔQ) require the reactive loop in the model in order to obtain accurate response. Long term phenomena are less sensitive to reactive power modelling. Although these observations are well known qualitatively, examples in this paper help to quantify the role of reactive power in power flow dynamics. The main lesson learned is that there are cases in which reactive power flow must be modelled in order to accurately study active power control and flow. An emphasis in the paper is rapidly changing, heavy industrial loads. The multiarea case is considered.