In this paper, a novel reliability assessment scheme is presented to achieve the optimal selection of control strategies for switched reluctance machine system from the perspective of reliability. To begin with, a combination model of k-out-of-n:G model and Markov model is proposed to lower the complexity and enhance the accuracy of system-level reliability assessment. As for the component-level reliability assessment, the three-dimensional coupled thermal circuit model of power converter is built to achieve the precise and fast prediction of junction temperature that is necessary for calculation of failure rate. Then the static and dynamic reliability analyses are carried out under voltage chopping control (VCC), current chopping control (CCC), and angle position control (APC) strategies, which indicates that the implementation scope of the APC strategy should be broadened. Compared with the VCC strategy, the CCC strategy is strongly recommended even if current sensors boost the extra failure rate. Besides, the increase in redundancy levels on power converter is certified as the most powerful measure for reliability enhancement of the SRM system and the most cost-effective redundancy level can also be quantitatively obtained. The experiments of fault-tolerance capability and thermal stress indirectly verify the validity of reliability analysis.

With the increasing penetration of inverter-interfaced photovoltaic (PV) systems in AC microgrids, the system inertia is increasingly deficient and the frequency response ancillary service provided by PV systems will be inevitable. In this paper, in order to make the PV systems provide multi-time scale frequency response, a novel distributed event-triggered hierarchical control (DEHC) of PV inverters is proposed, which includes a primary frequency response (PFR) control loop and a secondary frequency response (SFR) control loop. For the PFR, the PV inverters that operate in frequency regulation (FR) mode can arrest the frequency deviation in sub-seconds time-scale by an automatic deloading strategy, which is with low cost and easy to implement as no requirements for a storage system, irradiance sensors, and MPP estimators. For the SFR, the PV inverters that operate in FR mode can respond to the reference instruction assigned by a high-level AGC control center in seconds time-scale based on a novel distributed control strategy, which can converge within a fixed-time that independents to the initial conditions of the system. Furthermore, a novel event-triggered mechanism is designed to reduce the communication costs between PV inverters. Finally, case study results verify the effectiveness and improved performance of the proposed method.

To improve the speed synchronization performance of dual switched reluctance motor (SRM) drive with traditional sliding mode control (TSMC), the improved sliding mode control (ISMC) based cross-coupling control strategy is proposed. Firstly, the overall control structure of the dual-SRM drive is represented. Secondly, the state variable is introduced to reduce the torque fluctuation and adjustment time of the dynamic process of each SRM drive in the system based on the traditional sliding surface and sliding mode reaching law. The adaptive law is introduced into the sliding mode controller to avoid the load torque observation. Thirdly, the ISMC-based cross-coupling control method for the speed synchronization of the dual-SRM drive is designed. The novel sliding surface is proposed considering the speed synchronization deviation. The novel sliding mode reaching law is represented by introducing the state variables. Then the ISMC-based cross-coupling control method is realized for speed synchronization. The stability is proved by Lyapunov function. Simulations and experiments are implemented to verify the effectiveness of the proposed method.

This paper proposes a novel reliability evaluation scheme to achieve quantitative reliability calculation for power converter in the whole operation region of switched reluctance motor (SRM) system. Firstly, the electrical model is built to obtain electrical stress and fault-tolerance capability in Matlab/Simulink environment. Secondly, thermal circuit model is performed to get the thermal stress of power converter quickly. Thirdly, dynamical Markov model with a novel failure criterion is applied to achieve quantitative reliability calculation by characterizing the fault-tolerance capability and thermal stress. The proposed failure criterion can simplify the model to decrease the number of states and avoid the divergence of results. Especially the interconnected relationship of the three models is key emphasized. Next, the proposed reliability evaluation scheme is carried out to explore the reliability of power converter under different chopping modes. Finally, simulations in conjunction with experiment verifies the validity of the proposed reliability evaluation scheme.