一种用于频率跟踪和相角估计的实用算法

电网电压的频率、幅值和谐波含量均随时间发生变化,它们严重影响着电网相量的测量精度．为此,在分析傅氏法计算误差与频偏、起始点相位关系的基础上,提出了一种基于准同步采样和傅氏分析的频率跟踪、相角估计的实用算法．它用离散傅氏法和线性插值法估计任意时刻的相量,用迭代算法寻找相角差为零的相邻周期的两个估计相量进行频率计算,继而对采样数据进行同步化处理以获取信号的真实相量．仿真结果表明,这种方法可使相角误差小于0．2°,并能够满足电网相量实时测量的快速性要求．

A New Approach to Frequency Tracking and Phase Measurement

The frequency, amplitude and harmonic component of the voltage of power networks are time-variant. They have great effect on the measurement precision of the phasor in power networks. By analyzing the effect of the signal frequency shift and the phase of the calculation start-point on the error of DFT, a method based on quasi-synchronous sampling and DFT algorithm is proposed to track frequency and measure phase. In the process of calculating frequency, the linear interpolation method and DFT algorithm are used to estimate phasor at any time, and the iteration method is employed to find out the two estimated phasors, of which the interval is one period. Then, the sampling sequence is synchronized and the phase of the signal is calculated. The simulation results show that the phase can be obtained with an error within 0. 2? The proposed method can meet the rapidity requirement of the real-time synchronized phasor measurement for different sites in power networks.