基于参数估计的工频交流信号过零时刻检测方法

智能电网调试工程中广泛应用数字化检测设备,其相位准确度可通过工频交流信号过零时刻检测装置转换成时间准确度的检测,而当前大多数工频交流模拟信号过零检测方法用于电网同期检测,其准确度均达不到微秒级要求。本方法通过对输入信号进行连续采样,分别使用峰值检测及Levenberg-Marquardt算法估计正弦模型的相对频率和相位参数,并根据模型及估计的参数计算准确的过零时刻。在MATLAB上实现了该算法及模拟环境,改变信号的采样频率、估计信号长度、谐波分量及信噪比等参数,分别对算法进行测试。仿真结果表明,该算法在采样频率100 ksps,拟合数据长度不小于104时,对谐波含量1%以内,信噪比40 d B以上的工频交流信号过零时刻的估计误差为1μs左右。

Method on zero-cross time detection of power-frequency AC signals based on parameter estimation

Digital detection equipment is widely used in smart grid commissioning,and the accuracy of zero cross time detection is essential to the phase and frequency measurement of 50 Hz AC signals.The most commonly used zero cross time detection methods are for synchronization check which requires low accuracy that is not up to the micro-second level.A new method for zero cross time detection of AC signal is proposed.The peak detection method and Levenberg-Marquardt algorithm are used to estimate the parameters of sinusoidal model based on the continuous sampled data.The zero cross time is calculated according to the model and estimated parameters.This method and test bench is established on MATLAB.Experiments on different sample-rates,data length,harmonic power,and signal-noise ratio were conducted to verify the performance of this method.The results indicate that the deviation of detected zero cross time is around 1 μs in the circumstance of sample rate of 100 ksps,data length of 104,signal-noise ratio of 40 dB minimum,and harmonic power of 1％ maximum.