Power oscillation damper design using minimax LQG and LQG methods in large scale PV plants

Abstract

Large number of transmission voltage level PV plants are integrated into the existing transmission networks. As PV penetrations on weak transmission links increases, its impact on power system stability also increases. Low frequency oscillations are produced due to this reason. The influence on low frequency oscillations vary, it can be positive or negative depending upon the location and sizes of large scale PV plants. The low frequency oscillation (LFO) changes as its location changes, but it is not possible to shift these plants to an ideal location where the influence of low frequency oscillations less. So a damping controller has to be designed in order to reduce the low frequency oscillations. The POD is based on minimax linear quadratic gaussian method. In order to illustrate damping performance of the designed controller, a test system prone to power system oscillations is used. The test system and the PV model are simulated and then connected to analyse the produced oscillations. Then for mitigating the oscillations, the damping controller is designed. For designing of minimax LQG controller, state space representation of the entire power system model is required. From that state space matrices, by following a step by step procedure of minimax LQG method, the controller matrix can be formulated. The POD can be used to eliminate the low frequency oscillations. Controller is also designed using LQG method and by comparing the damping of oscillations by these two methods, we can see that minimax LQG method gives better damping of oscillations.