In this talk, we present a hardware-in-the-loop (HIL) testbed which is used to test our control algorithms that allows for the coordination of distributed energy resources (DERs). We discuss a novel distributed control algorithm, implemented on the hardware-in-the-loop testbed, which is used along with local power controllers to provide frequency regulation services to the bulk grid. This testbed is composed of a network of microcontrollers, Typhoon HIL Simulator, Ethernet switch and a computing platform. The computing platform acts as an aggregator and initiates the experiment by sending regulation signals to one microcontroller via serial communication. The microcontrollers communicate with each other wirelessly using Xbee modules and are used to execute the distributed control algorithm. These microcontrollers also equipped with Ethernet modules are connected to the HIL simulator via an Ethernet switch which is present to accommodate multiple microcontrollers. The local power controller is designed in the HIL simulator, and uses results obtained through the distributed control algorithm as an active power reference to determine the voltage set points for the inverter models. We present experimental results which show the convergence of the distributed control algorithm and the active power output of the DERs in comparison to the reference value.