“…It generates a much smaller system to approximate the original system such that the small system can retain some important properties (Jiang, 2010). Up to now, a lot of model reduction methods have emerged, such as Krylov subspace methods (Villemagne and Skelton, 1987; Yuan and Jiang, 2017), polynomials-based model reduction methods (Jiang and Chen, 2012; Kumar et al, 2016; Wang et al, 2016) and H 2 optimal model reduction methods (Qiu et al, 2018; Van Dooren et al, 2010).…”