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| Accuracy Comparison of Digital Implementation on the Second-Order Generalized Integrator Frequency-Locked Loop |
| Yang Caiwei1, Wang Jian1, You Xiaojie1, Wang Chenchen1, Zhan Zhejun2 |
1. School of Electrical Engineering Beijing Jiaotong University Beijing 100044 China;
2. CRRC Yongji Electric Co. Ltd Yongji 044502 China |
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Abstract Second-order generalized integrator frequency-locked loop (SOGI-FLL) is a grid synchronization algorithm based on SOGI, which consists of adaptive filter (AF) and frequency-locked loop (FLL). SOGI is a widely used in current control and grid synchronization to achieve zero steady-state error when tracking sinusoidal signals, but its accuracy is affected by digital implementation. AF is a closed-loop structure of SOGI, and its accuracy is also affected by the digital implementation. Moreover, in AF digital implementation, the orthogonality of two output signals needs to be ensured to guarantee the phase stability of the grid. Discretization results are different when using different discretization methods. Common discretization methods are divided into two categories, i.e. numerical integration methods and non-integration methods. If using non-integration methods, the hierarchy of AF to be discretized can affect the discretization results as well. AF can be divided into three levels of integrator, SOGI and AF. Different discretization methods are used for the digital implementation of each hierarchy, which are compared by bode diagram, simulations and experiments. The comparisons of digital implementation focus on accuracy and orthogonality of output signals.
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Received: 28 June 2018
Published: 28 June 2019
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2019, Vol. 34 
