Conference article

The amount of grid-connected power electronic converters is increasing as the world’s energy production shifts toward sustainable sources. Poor power quality and harmonic resonances have been reported which have been shown to be caused by grid-connected converters. Accurate modeling tools are required to characterize the conditions for instability and to design stable power-electronics-based power systems. Unstable behavior can be identi?ed by using models implemented in circuit simulators or using power-hardware-in-the-loop setups. The unstable resonance occurs when inverter control system interacts with the grid impedance. However, a very wide impedance-bank is required in the laboratory to test inverter stability when grid impedance is expected to vary signi?cantly. Moreover, stability tests are often limited to cases where grid impedance is approximated as an inductance. This paper proposes a method for emulating the grid impedance in a hardware-in-the-loop setup which eliminates the need for bulky passive components and allows arbitrary grid impedance to be emulated. As a result, the inverter can be tested with a varying grid impedance to determine the exact conditions for unstable behavior. Moreover, the grid impedance can be changed online to emulate the behavior of a time-varying power grid in real time.

hardware-in-the-loop, grid impedance, emulation