基于扩展卡尔曼滤波频率跟踪的DFT同步相量测量算法

An Improved Discrete Fourier Transformation Based Synchronous Phasor Measurement Algorithm Using Frequency Tracking Founded on Extended Kalman Filter

当电力信号的频率发生偏移时,采用离散傅里叶变换(discrete Fourier transformation,DFT)进行同步相量测量难以做到同步采样,由此造成的栅栏效应严重影响了同步相量测量精度。为此提出一种改进的DFT同步相量测量算法。首先引入了基于扩展卡尔曼滤波(extended Kalman filter,EKF)的频率跟踪算法,建立了基波频率测量的算法流程,并介绍了基于DFT的同步相量测量算法原理。在此基础上,将测量结果分为整数部分和分数部分,分析了因频率偏移导致的相量测量误差,对分数部分进行插值计算以提高同步相量测量精度。分别应用含谐波和噪声的稳定信号和幅值、相位、频率、谐波及噪声含量跳变的信号来校验算法的性能。仿真结果表明,EKF频率跟踪算法能快速对基波频率进行跟踪,所提出的同步相量测量算法能消除或减弱谐波、噪声以及频率偏移对同步测量的影响,提高了相量测量精度。

It is hard to perform synchronous sampling during synchronous phasor measurement by discrete Fourier transformation （DFT） under signal frequency deviation that causes the picket fence effect, which seriously affects the accuracy of synchronous phasor measurement. For this reason, an improved DFT based synchronous phasor measurement algorithm is proposed. Firstly, an extended Kalman filter （EKF） based frequency tracking algorithm is led in to establish an algorithm for power frequency measurement, and the principle of synchronous phasor measurement algorithm is presented; on this basis, the measured results are divided into integer part and fractional part, and the phasor measurement error due to frequency deviation is analyzed and the interpolation calculation is applied to the fractional part to improve the accuracy of synchronous phasor measurement. The performance of the proposed algorithm is validated by the steady signals containing harmonic and noise constituents as well as the signals with the jump of amplitude, phase angle, frequency, harmonics and noise level. Simulation results show that the EKF based frequency tracking algorithm can trace the power frequency quickly, and the proposed synchronous phasor measurement algorithm can eliminate or weaken the affects of harmonics, noise and frequency deviation on synchronous measurement, thus the accuracy of phasor measurement can be improved.