Analysis is carried out regarding the side effects caused by the line inductance. The study indicates that the concrete zero-crossing band of the sampled voltage renders uniquely symmetrical manner about the zero-crossing point of the actual grid voltage. An improved voltage phase detecting method is presented based on zero-crossing calculations. Furthermore， specifically for large line inductance and voltage fluctuation， phase locked loop（PLL） technique and Fourier analysis are integrated to develop a new voltage phase tracking method. Both simulations and experiments well verify the effectiveness and accuracy of the proposed two phase detecting methods.