基于离散谐振器的自适应数字锁频环设计

The Design for Digital Adaptive Frequency-Locked-Loop Based on Discrete Resonators

对电网电压基波幅值、频率以及谐波信息的准确估计是保证分布式电源并网变流器控制性能的重要条件。因而该文首先从便于数字实现的角度出发,提出了一种新颖的离散谐振器(discrete resonator,DR),并在数字频域下分析了该谐振器对单相和三相系统中正弦信号的积分作用,特别是三相系统下的频率极性选择特性;接着,针对电网中存在多次谐波的情况,提出了多重离散谐振器的滤波结构及其精确数学模型,并通过根轨迹法分析了多重离散谐振器增益系数之间的交叉影响,优化了增益参数的设计,提高了谐波检测的动态性能;最后,基于多重离散谐振器,设计了自适应数字锁频环(digital frequency-locked loop,DR-DFLL),该锁频环能够在电网正常和畸变条件下高精度的估计电网基波频率,且自适应于采样频率,同时便于数字实现。仿真与实验验证该文所提自适应数字锁频环的有效性和优越性。

The grid-tied converter for distributed generations is required with high control performance, which indicates that it is particularly important to estimate the information of the amplitude, frequency and harmonic of grid voltages. This paper proposed a novel discrete-time discrete resonator（DR） which was suitable for single-and three-phase systems simultaneously. And the integration property, especially the selectivity characteristic of positive and negative sequence components, was analyzed under the digital frequency domain. Based on the proposed DRs, the digital frequency-locked loop（DFLL） was designed. Furthermore, a systemic mathematical model of multiple DR was established to analyze the influence of gains for each DR by means of root locus. The DFLL proposed in this paper was convenient to be implemented digitally and can estimate the frequency of grid voltage fundamental with a high degree of precision which would not be influenced by sampling frequencies. Finally, the validity and superiority of the proposed DFLL are verified through simulations and laboratory experiments.