Hardware-in-the-Loop Simulation of Superconducting Devices for DC Electric Railway Systems Based on a Real-Time Digital Simulator

We have developed a hardware-in-the-loop (HIL) simulation setup to analyze superconducting devices for dc electric railway systems. When such superconducting devices are to be installed into a larger system, it is indispensable to characterize their behavior, i.e., their interaction with the system, to assure their reliability in all operating conditions. This is challenging when using full-scale superconducting devices and real power systems because many types of operation and fault cannot be easily demonstrated. Numerical simulation may compensate for that, but complete modeling of superconducting devices has often been difficult because of complicated electromagnetic behavior due to nonlinear transport properties, the transition between superconducting and normal states, and so on. In this paper, we have established an HIL simulation setup by the combination of superconducting hardware and a real-time digital simulator (RTDS). They communicate information about the instantaneous current and voltage values to each other every 50 μs. This enables us to simulate the interaction between superconducting devices and the system for many kinds of operation and fault. Furthermore, it is not necessary to use a full-scale superconducting device, as the signal level from/to the RTDS can be scaled. This will be very attractive for understanding the behavior of a superconducting device by studying a small prototype before developing the full-scale one.