The use of LCL-filter for reducing current harmonics has been commonly used for converters connected to the power grid. However, under non-ideal power grid condition, a converter using an LCL-filter may interact with other converters connecting to the grid. In this paper, a three-phase voltage source converter using an LCL-filter is studied. Simulations show that resonant oscillation occurs in the distributed power grid, even if the voltage source inverter with LCL-filter is well designed. A small-signal loop analysis is performed to predict this stability problem and a method is proposed for stability design.