Extension of Operating Range in Hybrid Cascaded H-Bridge Inverters with Capacitor Voltage Balancing Capability.

In this article, a generalized control scheme is proposed to extend the operating range of three-phase hybrid cascaded H-bridge (HCHB) inverters into various voltage levels without necessitating alterations to the core structure or the integration of additional H-bridge submodules. This study addresses a critical challenge related to capacitor voltage drift at various modulation indices and power factors, which is a serious impediment to various applications. To overcome this challenge, a novel balancing control scheme has been developed based on the injection of two independent offset voltages to simultaneously control the DC-link and flying capacitors. A distinctive aspect of the proposed technique involves adjusting the common reference voltage to attain the nearest level in the same cluster, thereby mitigating the insufficiency of redundant switching states. The effectiveness of the proposed technique to regulate the capacitor voltages at various operating conditions has been verified through simulation and experimental results.

Elimination reactions of N-alkyl-N-chlorothenylamines promoted by MeONa-MeOH and Et(2)NH-MeCN. Effect of the beta-aryl group on the imine-forming transition state.

Elimination reactions of N-alkyl-N-chlorothenylamines 1-4 with MeONa-MeOH and Et(2)NH-MeCN have been studied kinetically. The elimination reactions are regiospecific, producing only the conjugated imines. The reactions are second order and exhibit substantial values of Hammett rho and k(H)/k(D), and an E2 mechanism is evident. The relative rates of elimination for Me/Et/i-Pr/t-Bu substituents are 1/0.5/0.2/0.02 with MeONa-MeOH and 1/0.4/0.2/0.06 with Et(2)NH-MeCN. The transition state structure changes toward more product-like as the base is changed from MeONa-MeOH to Et(2)NH-MeCN. Comparison with existing data reveals that the structure of the transition state is relatively insensitive to the beta-aryl group variation.

Ketene-forming eliminations from aryl bis(4'-chlorophenyl)acetates promoted by R2NH-R2NH2+ in aqueous MeCN. Change of mechanism.

Elimination reactions of (4'-ClC6H4)2CHCO2C6H3-2-X-4-NO2 promoted by R2NH-R2NH2+ in 70 mol% MeCN (aq.) have been studied kinetically. The reactions are second-order and exhibit Brönsted beta = 0.44-0.86 and /beta(lg)/ = 0.41-0.71. The Brönsted beta decreased with a poorer leaving group and /beta(lg)/ increased with a weaker base. The results are consistent with an E2 mechanism. When X=H, the reaction proceeded by the concurrent E2 and Elcb mechanism.