Full
Outline
The sorting voltage equalization algorithm is often used as a submodule capacitor voltage control strategy for a modular multilevel converter (MMC), which poses a challenge in locating the open-circuit fault of an upper switch in a half-bridge submodule. To solve this problem, a method for locating the insulated gate bipolar transistor (IGBT) open-circuit fault in the submodule of MMC based on reconstructed subunit voltage is proposed. The voltage circuit equation of a three-phase MMC is established, and the influence of current flow path on the capacitor voltage and the reasons for abnormal output current and bridge arm circulating current are analyzed when an open-circuit fault for a single-switch occurs in the half-bridge submodule. An adaptive state observer based on extended Kalman filter (EKF) is used to achieve the optimal estimation of output current and bridge arm circulating current, and fault diagnosis is performed using the residuals between the optimal estimation value and the actual sampling value. Subsequently, the submodules with the same position as the faulty bridge arm in the three-phase system are grouped and reconstructed, so as to obtain the reconstructed subunits. The adaptive state observer based on EKF is utilized to estimate the reconstructed subunit voltage, and the difference between the estimated value and the actual average voltage of the corresponding reconstructed subunit is compared with a preset threshold, thus achieving the fault localization. Four typical IGBT open-circuit fault conditions of submodules were selected for experimental verification, and experimental results show that the proposed fault diagnosis and localization method is correct and feasible.
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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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