An Economical Hardware-in-loop Approach for Real-Time Simulation of SST

Solid state transformers (SSTs) use power electronic converters to enhance the functionality of the grid. They are also essential for the development of smart and micro grids as well as interfacing the renewable energy sources to the grid. Single stage SSTs have no bulky inductors and capacitors which leads to high power density. Also just a single stage of power conversion leads to high efficiency compared to the two and three stage SSTs. This paper develops a hardware-in-loop (HIL) based approach using a DSP and an FPGA for real time simulation of direct AC/AC solid state transformer (SST). HIL is used for testing the various aspects of a power electronic system like modulation strategies, controllers etc. before implementing them in actual hardware. This avoids risk of damage and ensures rapid development of the hardware. However, HIL in current literature is implemented using expensive, dedicated processors which are not easily available in a power electronics laboratory.The HIL based approach in this paper is developed using a DSP and an FPGA which are easily available in a power electronics laboratory and can be repurposed for various uses. The DSP used is TI’s F28335 and the FPGA used is NI’s Sbrio 9636. The SST model is build in FPGA using NI’s LabVIEW environment while the controller is programmed using TI’s code composer studio. A Simulink model for the SST is developed to validate the results of the proposed HIL based approach.