Full
Outline
An accurate estimation of utility harmonic impedance is the key to harmonic source determination. Most of the existing methods are based on the premise that the background harmonics keep constant or fluctuate smoothly. However, the background harmonic voltage or utility harmonic impedance generally exhibits unsmooth fluctuation patterns in the novel power system, and there are even abrupt changes in some time sections, which leads to large calculation errors in the existing methods. To solve this problem, an estimation method for utility harmonic impedance considering the time-varying characteristics of background harmonics is proposed. First, this method identifies multiple abrupt change points of background harmonics by means of the binary sliding T maximum, and the measured harmonic data at a point of common coupling (PCC) is divided into several intervals of continuous unsmooth fluctuation accordingly. Then, with the consideration of the small variation of background harmonics between adjacent sampling points, utility harmonic impedance estimation is carried out based on the principle of comprehensive minimum fluctuation within each data interval, and the matrix sparse technique is introduced to reduce the computational time complexity. Finally, simulations and field data are adopted to conduct a comparative analysis, and results indicate that compared with the existing methods, the proposed method can more accurately estimate the utility harmonic impedance and demonstrate a higher computational efficiency.
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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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