In this paper, a comparison of simulation between Power Systems Computer Aided Design (PSCAD) and Real Time Digital Power System Simulator (RTDS) Hardware In-the-Loop (HIL) is presented under the same conditions to express their corresponding results for other researchers reference the differences and choice the suitable testing system. Both RTDS and PSCAD are applied widely and trusted in power electronics researching field. However, RTDS provides a real time simulation process to get close to real experimental results. Further, RTDS support HIL and permit Digital Signal Processor (DSP) control inside simulation components. Therefore, the results differences produced by RTDS and PSCAD becomes one important reference for a system or algorithm. In this study, one power compensator simulation system is built in both PSCAD and RSCAD. The set-up process is introduced, and their simulation results are analyzed.