I. INTRODUCTION
Control of interconnected dynamical systems is a challenging problem with many applications, for example in power grids and process control. We consider a class of systems in which subsystems are coupled over states, inputs, and a performance criterion. The control of systems coupled via states has already been tackled to a considerable extent within the framework of decentralized control [1]. Within this framework, the overall system is decomposed by exploiting structural interconnection constraints in order to obtain a system structure which allows to design decentralized control laws. Results have been published on how to alter the decomposition if a system does not admit a stabilizing decentralized controller [2]. However, even if a stabilizing decentralized controller exists, performance might be significantly degraded compared to a centralized approach.