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Summary With the capability of DC fault ride‐through and the reduced cost, the hybrid modular multilevel converter (HMMC) is a promising topology for high‐voltage direct current (HVDC) applications. However, the complicated configuration of HMMCs with a large number and different types of submodules (SM) increases the risk of submodule failure. This paper proposes a novel HMMC submodule fault‐tolerant strategy by adjusting the number of inserted SMs of faulty phases. Then, based on the analysis of the SM voltage fluctuation, an SM capacitor voltage controller matched in coordination with the fault‐tolerant strategy is designed. By utilizing the negative voltage output full‐bridge submodules (FBSMs), this strategy can significantly improve the SM fault‐tolerant capability of the HMMC. Moreover, as compared to conventional fault‐tolerant strategies, the proposed strategy requires fewer components and can be easily implemented. Finally, the feasibility and performance of the proposed strategy are verified by the MATLAB/Simulink simulation experiment under different fault conditions and MMC systems.

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Grazing by large herbivores can potentially affect interspecific interactions between small herbivores by reducing the ecological fitness of animals. Desert rodents are important components in desert ecosystems and indicators of environmental change. Grazing reduces food resources, but rodents can decrease interspecific niche overlap by adaptive behavior. However, the key factors driving rodent behavioral activities and coexistence in the Alxa desert remains unstudied. We monitored population density and behavioral activities of Midday gerbil (Meriones meridianus) and northern three-toed jerboa (Dipus sagitta) in a grazing exclusion experiment in Alxa desert, Inner Mongolia, China, in 2017. We assessed the relationship between environmental factors (such as plant height, density, coverage, rainfall and temperature) and the behavioral activities of two coexisting rodent species. The results showed that: (1) In summer, grazing significantly reduced the activity time of gerbil and jerboa compared to that in grazing exclusion areas (gerbil: F = 5.98, p < 0.05, η2 = 0.22; jerboa: F = 8.57, p < 0.01, η2 = 0.28). Grazing reduced the temporal niche overlap with an obvious shifting of activity peaks between two species. (2) Grazing exclusion enhanced the temporal niche overlap between the two rodent species due to greater food availability which relieved inter-specific competition in each season. (3) Grazing strengthened the sensitivity of rodents to environmental changes in all seasons. These results indicated that grazing affected competition between the rodent species by altering vegetation conditions, which in turn affected the temporal niche and activity patterns of rodents.