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Outline
Under weak grid conditions, the grid-connected inverter (GCI) commonly employs a type-II Phase-Locked Loop (PLL) system, which is prone to interaction with the grid impedance, leading to instability issues characterized by low-frequency oscillations. A traditional solution aimed at enhancing GCI stability by reducing the type-II PLL's bandwidth. However, this approach compromises the dynamic performance of the PLL and its adaptability to a wide range of grid impedance variations. To address this, the traditional Type-II PLL was replaced by Type-I PLL, significantly improving the stability of GCI in weak grids without degrading the PLL's dynamic performance. Furthermore, to tackle the phase-locking error issue in type-I PLLs during significant grid frequency fluctuations, an adaptive feedforward method for frequency control is introduced. This enhancement transforms the type-I PLL into a quasi-type-I PLL, eliminating phase tracking errors and enhancing the stability and dynamic performance of GCI in weak grid environments. Both simulation and experimental results confirm the validity and efficacy of the proposed methods.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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