Virus infection can alter immune regulatory activity, and thus may be involved in the occurrence of autoimmune diseases. Recently, the pandemic of COVID-19 has posed a huge threat to public health and emerging evidence suggests that coronavirus may be implicated in the development and pathogenesis of autoimmune diseases. However, how coronavirus infection impacts the risk of autoimmune disease remains largely unknown. In this review, we focused on the association between coronavirus and autoimmunity, and elucidated the molecular mechanisms linking coronavirus exposure to autoimmunity. Additionally, we briefly introduced the role that coronavirus plays in several autoimmune diseases including multiple sclerosis (MS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and idiopathicthrombocytopenic purpura (ITP).

Based on Support Vector Machines (SVM) and S-transform, a novel approach to detect and classify various types of high voltage direct current (HVDC) converter faults is presented. An electro-magnetic transient state simulation software PSCAD/EMTDC was used to set up a simulation model of HVDC system to investigate the typical converter faults. For the good time-frequency characteristic of S-transform, S-transform is applied to obtain useful features of the non-stationary fault signals. Then fault types are identified through the pattern recognition classifier based on SVM classification tree. Numerical results show that the proposed classification method is an effective technique for building up a pattern recognition system for converter fault signals.

Capacitive commutation technology is favorable in improving the stability of weak receiving end ac systems, and our Qinghai-Xizhang HVDC interconnection project is exactly belonging to this kind. In order to study the effect of capacitor commutation technology to ac and dc systems, basing on the Qinghai-Xizhang HVDC interconnection project, the paper focuses on analyzing the building of the HVDC simulation model with capacitor commuted converters (CCC-HVDC model) in PACAD/EMTDC simulation program, and then the optimization selection of commutation capacitance parameter is described. Finally, capacitor commutated converters effect in improving the stability of weak receiving end ac system is simulated and analyzed.

As the development of high voltage direct current (HVDC) transmission, the problems of harmonic instability become more prevalent. Besides, harmonic instability in exceedingly weak HVDC systems is particularly serious. The modulation of the DC converter based on switching function is deduced. By considering the whole process of harmonic transferring at the AC and DC side through converters from the perspective of circuit, the generation conditions of harmonic instability are analyzed. Then an exceedingly weak HVDC system model is established and simulated in PSCAD/EMTDC software to verify the theoretical analysis. The study results provide theoretical basis and computational methods to solve the problems of harmonic instability in HVDC systems.

Harmonic transfer between different levels of ac systems increases the difficulty in harmonic identification and governance. From the view of harmonic transfer coefficients, the paper firstly establishes a harmonic infiltration equivalent model of different voltage levels, and then analyzes the formula of harmonic transfer coefficients. Finally, the computational and simulation analysis are carried out in MATLAB software to study the factors that affect the harmonic transfer coefficients between different voltage levels.