Multirate Partitioning Interface for Enhanced Stability of Power Hardware-in-the-Loop Real-Time Simulation

Power hardware-in-the-loop (PHIL) technology allows for the testing of physical equipment including power electronic converters in a simulation environment that closely mirrors the reality of the electric power grid. A challenge involved in PHIL systems is the design of the interface between the digital network model and physical equipment as this has a significant influence on stability of the real-time simulation. While a small time step supports stability and accuracy, its lower limit is given by the real-time constraint. The proposed multirate partitioning (MRP) interface addresses this issue by using a rather small time step at the hardware-software interconnection and then employing a staged adaptation of the time step within the digital model in accordance with the real-time constraint. Thus, multiple rates are used. The Nyquist stability criterion confirms enhanced stability and bandwidth by the MRP compared with single-rate (SR) counterparts. Moreover, a PHIL test of two parallel photovoltaic converters feeding a low-voltage network reveals different behaviors depending on the interface. Using the MRP, the waveforms more closely track the real-world curves of active and reactive power with the relative accuracy increasing with the speed of the transients. Informed decision making regarding the integration of renewables in the grid is so supported.