计及负频率影响的新能源发电低频间谐波检测方法

近年来,随着新能源发电的快速发展,越来越多的电力电子设备应用于发电单元,导致电网中出现了频率为次同步的间谐波。在对这类低频间谐波进行参数估计时,由于受负频率影响,现有的离散频谱校正方法存在较大的误差。为提高其频谱分析精度,文章在IEC 61000-4-7推荐的测量环境下,提出了一种计及负频率影响的离散频谱校正方法。根据信号FFT后的频谱特性,建立包含负频率在内的离散频谱校正模型;依据离散频谱的周期性,利用局部谱峰附近的4条谱线构建谱线方程组来求解低频间谐波的频率校正分量;根据估计出的频率,利用间谐波峰值谱线的频谱值及其共轭值来修正其幅值和相位参数。仿真结果表明,所提方法可以有效降低负频率成分对信号频谱谱线干涉的影响,提高低频间谐波的频率、幅值和相位校正精度,同时具有较好的抗噪性能。

Low frequency interharmonic detection method for new energy generation considering negative frequency contribution

In recent years, with the rapid development of new energy, more and more power electronic devices are applied in the power grid, resulting in the occurrence of sub-synchronous interharmonics in power signals. Influenced by the negative frequency components, the existing discrete spectrum correction methods have large errors in estimating the parameters of this kind of low frequency interharmonic signals. In order to improve the accuracy of spectrum analysis, a discrete spectrum correction method with negative frequency effect is proposed based on the specified signal processing recommendations by IEC61000-4-7. Firstly, the discrete spectrum correction model including negative frequency is established according to the spectrum characteristics of the signal after DFT. Secondly, according to the periodicity of the discrete spectrum, spectrum equations is constructed by using four spectral lines closing to the local peak value to solve the frequency correction component of the low frequency interharmonic. Then, based on the estimated frequency, the spectrum value and conjugate value of the interharmonic peak line are used to correct the amplitude and phase parameters. The simulation results show that the method proposed in this paper can effectively reduce the influence of negative frequency components on spectral line interference of signals, improve the frequency, amplitude and phase correction accuracy of low frequency interharmonics, and have good anti-noise performance.