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This study presents the design of local decentralised power system stabiliser (PSS) controllers, using selected suitable remote signals as supplementary inputs, for a separate better damping of specific inter-area modes. Each local PSS controller is designed separately for each of the inter-area modes of interest. The PSS controller uses only those local and remote input signals in which the assigned single inter-area mode is most observable and is located at a generator which is most effective in controlling that mode. The local PSS controller, designed for a particular single inter-area mode, also works mainly in a frequency band given by the natural frequency of the assigned mode. The locations of the local PSS controllers are obtained based on the amplitude gains of the frequency responses of the best-suited measurement to the inputs of all generators in the inter-connected system. For the selection of suitable local and supplementary remote input signals, the features or measurements from the whole system are preselected first by engineering judgment and then by using a clustering feature selection technique. Final selection of local and remote input signals is based on the degree of observability of the considered single mode in them. To provide robust behaviour, H∞ control theory together with an algebraic Riccati equation approach has been applied to design the controllers. The effectiveness of the resulting robust H∞-based PSS controllers is demonstrated through digital simulation studies conducted on a test power system.