In this Letter, a demodulation based pre-filtering technique is proposed for fast detection of the single-phase grid variables. The estimation of grid voltage parameters is achieved through a Type-I synchronous reference frame phase-locked loop (PLL). The modified bandpass filter in the pre-filtering stage ensure a better rejection of the DC-offset and harmonics. Thus, the grid variables are estimated rapidly with the help of a simple proportional controller. Consequently, in-loop filtering burden and the effort required to tune the PLL is minimal. However, steady errors are witnessed in the fundamental amplitude and the phase information which are mitigated by a curve fitting technique. Importantly, the proposed PLL scheme has improved the dynamic performance under off-nominal frequency conditions with immunity against grid disturbances. The robustness of the proposed algorithm is experimentally verified vis-a-vis existing literature.

中文翻译：

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基于改进的非自适应带通滤波器的锁相环

在这封信中，提出了一种基于解调的预滤波技术，用于快速检测单相电网变量。电网电压参数的估计是通过 I 型同步参考框架锁相环 (PLL) 实现的。预滤波阶段改进的带通滤波器确保更好地抑制直流偏移和谐波。因此，在简单的比例控制器的帮助下，可以快速估计电网变量。因此，环路滤波负担和调整 PLL 所需的工作量是最小的。然而，在基本幅度和相位信息中可以看到稳态误差，这些误差通过曲线拟合技术得到缓解。重要的是，所提出的 PLL 方案提高了非标称频率条件下的动态性能，并具有抗电网干扰的能力。