Load and source electronic emulation using resonant current control for testing in a microgrid laboratory

This paper details the development of a microgrid test set-up for the purposes of performing electrical system emulation such as load emulation and the emulation of generation equipment such as PV arrays. This test rig is comprised of two 15 kW dc-ac inverters connected in back to back configuration together with a rapid prototyping platform utilizing a Linux PC to interface with the inverter FPGAs using a control model built in Simulink Real-Time Workshop. This test platform allows for accelerated testing and verification of control designs, allowing the user to utilize existing Simulink toolboxes, and facilitates real time interaction with the equipment while in operation. In order to accurately track the current references of the emulated non-linear loads, a digital resonant current control scheme was designed and implemented. This controller utilizes a vector proportional integral control scheme to compensate up to the 18^th harmonic in the synchronous reference frame. Current references are generated using an in the loop simulation of the desired load or generator model in Simulink. Experimental results are presented to verify the operation of the system as a load emulator with linear RCL load and unbalanced load. Generation emulation was carried out using an emulated PV array.