Dynamic modeling, control design and stability analysis of railway active power quality conditioner

Two-phase three-wire converter has been proposed to compensate the power quality issues in AC electrified railway systems. In this paper, a step-by-step modeling procedure is presented and applied to the compensator to obtain a linear model. The model is then used in a linear control system design and stability analysis of the compensator. The first step is to obtain the bi-linear form of the exact (switched) model of the compensator representing the high and low frequency behavior of the converter. Then, the generalized state space averaging is applied to the bi-linear model to obtain the continuous time model of the compensator. The linear small signal model is derived by differentiating the averaged model around its equilibrium point. Linear control system design is established based on the linear small-signal model to improve DC-link voltage performance. The simulated model of compensator is verified by quantitatively comparing to the previously reported experimental results. The verified simulation model is used to validate the obtained models. Finally, the open loop stability analysis is performed by studying the locus of system eigenvalues with respect to the circuit parameters variations.