Multimode Power Oscillation Damping Controller Synthesis using Vector Fitting

Low-frequency oscillations in power systems have been commonly damped by power system stabilisers based on lead-lag transfer functions. These stabilisers can be implemented in the control loops of synchronous generators or converter-interfaced generation (CIG). Commonly, pole placement techniques are used to design power oscillation damping (POD) controllers. However, these methods require a detailed linearised model of the power system which is not always available. In this paper, a method to synthesize POD controllers for multiple modes using the vector fitting (VF) algorithm is presented. This technique is based on the compensation of the open-loop phase of the plant at some specific frequencies. Therefore, it is suitable for those cases when the power system model is not accessible because it only requires the frequency response at certain points. The VF algorithm is then used to synthesise a transfer function that fulfils the specifications. The proposed method is tested using a benchmark power system consisting of three machines and an additional CIG. Finally, the performance of the POD controller is verified by using electromagnetic transient simulations in Matlab/SimPowerSystems.