Secondly the detection precision is only related to the synchronization phase but not to the amplitude of the mainline voltage because that it uses the optimized pulses synchronous with the mainline voltage as modulation signals . thirdly it decreases the requirement of the input low pass filter and eliminates the error resulting from the direct component and even harmonics of load current . the most significant merit is that it can eliminate the effect of a few low order odd harmonics and the detecting circuit is easy to be implemented 仿真和实验结果表明该方法的主要优点有：不需使用乘法器进行信号调制，调制信号采用与电网电压同步的优化特定脉冲，其检测精度只与同步相位有关，而与电网电压幅值无关；降低了对输入低通滤波器的通频带要求，直流和偶次谐波分量对检测精度没有影响；突出的优点是可以消除有限个低奇次谐波对检测结果的影响。
