Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization
Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization
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DOI：
10.1109/access.2020.2986409
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发表时间：
2020-01-01
期刊：
影响因子：
3.9
通讯作者：
Benbouzid, Mohamed
中科院分区：
文献类型：
--
作者：
Ahmed, Hafiz;Salgado, Ivan;Benbouzid, Mohamed
并网变流器是电力电子系统的重要组成部分。许多电力和能源应用需要并网转换器。为了控制并网变流器，需要精确的电网电压频率和相位信息。梯度估计器在这方面非常有用。它们适用于估计电网电压信号的频率和相位。在文献中已经有各种梯度估计器，例如基于回归的技术。然而，它们大多数都是使用瞬时估计误差作为代价函数来设计的。这放大了估计参数中噪声的影响。为了克服这个问题，本文考虑了一个积分成本函数。积分成本函数试图最小化积分窗口上的估计误差，从而减少估计频率和相位中的噪声影响。此外，成本函数使用可调的遗忘因子来赋予最近的数据更多的重要性。所提出的梯度估计器假设电网频率是恒定的。然而，在实践中，频率是可变的，具有已知的标称值。为了克服这个问题，频率估计块与梯度估计器耦合。频率估计块使用基于相位的频率估计的思想。比较数值模拟和实验研究，以证明所提出的技术的适用性超过其他三个先进的技术从文献中。
Grid-connected converters are an important class of power electronic systems. Many power and energy applications require grid-connected converters. To control grid-connected converters, precise information of the grid voltage frequency and phase are required. Gradient estimators can be very useful in this regard. They are suitable to estimate the frequency and phase of the grid voltage signal. Various gradient estimators are already available in the literature e.g. regression-based techniques. However, most of them are designed by using the instantaneous estimation error as the cost-function. This amplifies the effect of noise in the estimated parameters. To overcome this issue, an integral cost-function is considered in this paper. The integral cost-function tries to minimize the estimation error over the integration window leading to reduce the effect of noise in the estimated frequency and phase. Moreover, the cost-function uses tunable forgetting factor to give more importance to recent data. The proposed gradient estimator assumes the grid frequency to be constant. However, in practice the frequency is variable with known nominal value. To overcome this problem, a frequency estimation block is coupled with the gradient estimator. The frequency estimation block uses the idea of phase-based frequency estimation. Comparative numerical simulation and experimental studies are performed to demonstrate the suitability of the proposed technique over three other advanced techniques from the literature.