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). The design of POD controllers for multiple low-frequency oscillations has been usually addressed by using pole placement techniques. However, these methods require a detailed linearised power system model, which is not always available. In this paper, a method for multimode POD controller synthesis using vector fitting (VF) is presented, relying on the open-loop phase compensation method. This makes it suitable for cases in which the power system model is not accessible as it only requires the frequency response of the electrical system and the oscillation frequencies. The VF method is used to synthesise a transfer function that fulfils the given set of specifications in the frequency domain. The proposed method is tested on a benchmark power system consisting of three machines and an additional CIG. Finally, the POD controller performance is verified by using electromagnetic transient (EMT) simulations in Matlab/SimPowerSystems.