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With the development of flywheel technology, the speed and the voltage level of flywheel continue to increase. The Z-type self-balancing modular multilevel converter can have a wide frequency range at medium voltage and is suitable for flywheel driving application. However, the voltage and current characteristics of the flywheel and the variable frequency drive still affect capacitor voltage balance in each phase-leg. The new balance of capacitor voltage can be achieved by controlling the circulating current. This paper proposed a control algorithm of the novel Z-type self-balancing modular multilevel converter for flywheel driving applications. Simulation results are presented to validate the theoretical analysis.

Aggregated green infrastructure is the only element that has a relatively concentrated and well-functioning carbon sink in the city. It plays an important role in achieving carbon neutrality in urban areas with dense functions and scarce carbon sink resources. However, in contrast to other regions, aggregated green infrastructure carbon sink performance is more influenced by socioeconomic activities in urban centres. There is a lack of research on the impact between carbon sink performance and socioeconomic activities at the urban scale. In this study, we evaluated the carbon sink performance (i.e., carbon sink and location entropy) of aggregated green infrastructure and its interaction with socioeconomic activities at the urban scale based on Sentinel-2A satellite. The results showed that: (1) Aggregate green infrastructures with high carbon sink performance have significant aggregation characteristics in urban areas. (2) Aggregated green infrastructure with poor carbon sink performance tended to be surrounded by dense socioeconomic activities. Our study provides a new approach to the assessment of carbon sink performance of aggregated green infrastructure at the urban scale. More importantly, we make a new attempt to assess the association between carbon sink performance and socioeconomic activities of urban aggregated green infrastructure. These results point to a new direction for the realization of carbon neutrality in cities.