Model reduction of large-scale systems in the neighborhood of crossover frequency

A new model reduction concept and approach is proposed. In this approach the order of a large-scale system is reduced in the neighborhood of crossover frequency in order to retain stability and performance of the full order system. This concept very closely preserves the gain and phase of the original system. In this approach, the full order system is perturbed and reduced within its specified frequency bandwidth. The concept is applicable to both open and closed-loop systems. To illustrate the effectiveness of the proposed concept and approach a benchmark 4(th) order plant model is reduced to a 2(nd) order. For the same 4(th) order system, two distinct approaches are applied to design two distinct 2(nd) order H(infinity) controllers. The simulation results of the two controllers are compared.