PARTSim is an open-source power-aware real-time system simulator. Given a proper description of both the hardware platform and the software that shall be executed on it, PARTSim can simulate the non-functional behavior of the applications under various DVFS settings, using precise models derived by its companion tool PARTProf. With this simulator, both the timing and power behavior of applications can be precisely simulated, depending on several configurable scheduling policies, including those implemented by the Linux kernel, such as SCHED_DEADLINE, SCHED_FIFO, and SCHED_RR. It is also easily extensible, so researchers and practitioners can prototype novel scheduling strategies before implementing them in a proper operating system kernel. The software is publicly available on Gitlab.