Abstract :
The reaction of actively controlled power-electronics converters connected to the grid to grid-fault conditions becomes more and more important. This results, on the one hand, from standards defining increasingly demanding characteristics for such converters. On the other hand, the number of such devices increases steadily, especially for infeed use, in the context of renewable energy, bi-directional charging and energy-storage applications. With increase in numbers and power, these converters play an increasingly important role concerning grid conditions during faults. Consequently, their reaction to such conditions needs careful analysis - not only by simulation, but also by experiment. Two approaches to this challenge are known: Mechanical switches for defining these fault conditions and power-electronic converters generating test grids emulating fault conditions. They each have advantages and disadvantages. This paper proposes a new, combined strategy: Power-electronic switches are used for the precisely defined emulation of grid faults, combining advantages and avoiding disadvantages of known methods. Loads with high grid-fault currents, like doubly-fed induction machines, can be tested under realistic conditions with comparatively low effort.
