DC power distribution systems for building application are gaining interest both in academic and industrial world, due to potential benefits in terms of energy efficiency and capital savings. These benefits are more evident were the end-use loads are natively DC (e.g., computers, solid-state lighting or variable speed drives for electric motors), like in data centers and commercial buildings, but also in houses. When considering the presence of onsite renewable generation, e.g. PV or micro-wind generators, storage systems and electric vehicles, DC-based building microgrids can bring additional benefits, allowing direct coupling of DC loads and DC Distributed energy Resources (DERs). A number of demonstrating installations have been built and operated around the world, and an effort is being made both in USA and Europe to study different aspects involved in the implementation of a DC distribution system (e.g. safety, protection, control) and to develop standards for DC building application. This paper discusses on the planning of an experimental DC microgrid with power hardware in the loop features at the University of Naples Federico II, Dept. of Electr. Engineering and Inf. Technologies. The microgrid consists of a 3-wire DC bus, with positive, negative and neutral poles, with a voltage range of +/-0÷400 V. The system integrates a number of DERs, like PV, Wind and Fuel Cell generators, battery and super capacitor based storage systems, EV chargers, standard loads and smart loads. It will include also a power-hardware-in-the-loop platform with the aim to enable the real time emulation of single components or parts of the microgrid, or of systems and sub-systems interacting with the microgrid, thus realizing a virtual extension of the scale of the system. Technical features and specifications of the power amplifier to be used as power interface of the PHIL platform will be discussed in detail.