In the current era of information explosion, cybersecurity challenges have become increasingly prominent. Compared to malware that causes direct attacks, covert malware poses a significant cybersecurity threat as it can remain hidden within networks for extended periods while stealthily stealing users’ private information. To address the challenge of clearing covert malware, this study proposes two defense mechanisms: the Patch Propagation Mechanism (PPM) the aSleep-aWake Mechanism (SWM). Based on these mechanisms, we develop a mean-field two-layer propagation model, SW-VIPU (aSleep-aWake-Vulnerable-Infected-Patched-Unaware), to analyze the network’s dynamic evolution. In addition to theoretical analysis, the effectiveness of PPM and SWM in curbing the spread of malware is validated through comparisons with existing models and simulations on real-world network topologies. Subsequently, to enhance the performance of SWM, we introduce a multi-pulse control mechanism and analyze the dynamic performance of SW-VIPU under this mechanism. Finally, to comprehensively explore and improve the control effectiveness, we introduce static strategies as well as an objective-function-based dynamic defense framework, leading to the development of several hybrid control strategies (HCSs). The effectiveness of these HCSs is confirmed through simulation experiments. The experimental results demonstrate that the proposed dynamic HCSs outperform static HCSs in most scenarios. Furthermore, when malware exhibits a high propagation capability, patches should be deployed at their maximum deployment output, and users should be forced to log out and be prohibited from logging back in. Conversely, when malware spread capability is weaker, although the patch output should still be maintained at its highest level, user logins and logouts should not be restricted.

The advent of third-generation semiconductors brings the switching frequency into a much higher level, which enables high-frequency transformer with a smaller footprint in power electronics. Due to its inherent ability of voltage amplification, the transformer-based voltage-multiplier becomes prevalent in step-up converters which are the inevitable parts in the usage of low-voltage renewable resources. Though its feasibility has been verified in many researches, an uncertain error in voltage conversion ratio exists between the reality and ideal, which leaves a theoretical gap. Accordingly, the key affecting characteristics, the reverse recovery process of the leakage inductance, is considered and analyzed in this paper. The power transmission mechanism is clarified, and the root-mean-square error of the gain can be reduced from 24.31% to 3.13%, and the maximum output power together with power effect on the gain are obtained. With the conclusion of this paper, parameters of power supply can be optimized at the beginning of design to satisfy the demand of maximum output power and gain over a wide power range, which can save the unnecessary trial-and-error during the case-by-case design.

The advent of smart terminals and the IOT era has prompted the emergence of the multiplex network system. With the rapid information transmission in multiplex networks, security incidents caused by malicious attackers occur frequently. In light of the foregoing, this paper concentrates on modeling and analyzing the propagation process of multiplex networks. Particularly, this paper proposes an epidemic-based RCMO (Running- Confined- Malfuntioned- Overhauled) model after considering the operating state of equipment and a class of visibility-aware malware. After that, the stability analysis of the equilibria is performed to verify the effectiveness of the propagation threshold obtained in RCMO. Then, we introduce static controls including unique control, target control, acquaintance control, and pulse control, as well as dynamic controls including continuous-time and pulsed forms to the suppression strategies for preventing the spread of malware. Furthermore, the control strategies are cross-combined into$6\times 6$hybrid maintenance strategies (HMS), and the simulation analysis is performed from three perspectives: evolution of state variables, accumulation of revenue, and change of controls. We discovered through experimental results that the optimal HMS to inhibit the propagation of malware and the HMS with the highest revenue are always different under various network topologies, but they are all hybrid combinations of continuous-time and pulse controls. To some extent, dynamic control can reduce discrepancies between the HMS and generate approximate returns. Finally, we propose a few cyber defense recommendations for network administrators.

This paper presents a multi-agent (MAS) solution to the energy management in microgrid. An introduction and analysis of the system, including the structure of microgrid, characteristics of MAS and the potential game theory, are presented firstly. Then, micro models of agents for each component are proposed. The MAS is shown of having attributes of distribution, heterogeneity, autonomous, dynamism and openness. And then, the overall model of MAS and the process of optimization are presented in the next part. Potential game theory is introduced which applying as the distributed optimization method embedded in each micro agent model. Finally, the MAS for microgrid is formulated and implemented by the JADE platform. A scenario case study on the MAS and its testing process are included in the paper.

In this paper, a switched Z-source dc-dc converter (SZSC) is proposed for the conversion from a low voltage to a higher one in renewable energy systems. The voltage gain is increased by adding another one switch and diode to the output terminal of the traditional Z-source dc-dc converter. Not only does the output capacitor function as the filter capacitor; it is also connected in series into the inductors' charging loops when both switches are turned on. Compared with existing Z-source based structures, higher voltage gain is realized with a small duty ratio (smaller than 25%), which can avoid the instability caused by saturation of inductors. Fewer passive components are employed when compared with the recently proposed hybrid Z-source topologies that have the same boost factor, increasing the efficiency and decreasing the cost. Another two switched quasi-Z-source dc-dc converters (SQZSCs) with the same transfer ratio are proposed in analog to the two traditional quasi-Z-source topologies. The performances of the proposed SZSC are analyzed, and then validated by simulation and experimental results.

In this paper, a quasi-resonant switched-capacitor (QRSC) multilevel inverter (MLI) is proposed with self-voltage balancing for single-phase high-frequency ac (HFAC) microgrids. It is composed of a QRSC circuit (QRSCC) in the frontend and an H-bridge circuit in the backend. The input voltage is divided averagely by the series-connected capacitors in QRSCC, and any voltage level can be obtained by increasing the capacitor number. The different operational mechanism and the resulting different application make up for the deficiency of the existing switched-capacitor topologies. The capacitors are connected in parallel partially or wholly when discharging to the load, thus the self-voltage balancing is realized without any high-frequency balancing algorithm. In other words, the proposed QRSC MLI is especially adapted for HFAC fields, where fundamental frequency modulation is preferred when considering the switching frequency and the resulting loss. The quasi-resonance technique is utilized to suppress the current spikes that emerge from the instantaneous parallel connection of the series-connected capacitors and the input source, decreasing the capacitance, increasing their lifetimes, and reducing the electromagnetic interference, simultaneously. The circuit analysis, power loss analysis, and comparisons with typical switched-capacitor topologies are presented. To evaluate the superior performances, a nine-level prototype is designed and implemented in both simulation and experiment, whose results confirm the feasibility of the proposed QRSC MLI.