一段dsp中的零序过流保护程序，再发上零序故障时用来动作保护。-For dsp saver module, used to detect the zero-sequence fault protection action under the circumstances

可以对所给正弦信号进行采样，并判断过零点且输出频率和正弦信号一样的方波信号。用ePWM模块来确定采样频率，来一次中断采样一次，确保采样率。并对所采样的数据进行有效值计算(The given sinusoidal signal can be sampled and the zero-crossing point can be determined and the square wave signal with the same frequency as the sinusoidal signal