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In this paper, the issue of open-switch faults of voltage source inverter (VSI) is studied, an adaptive fast voltage-based real-time open-switch fault location method is proposed. Firstly, for each switching period, the voltage deviation is calculated by the expected voltage and estimated actual voltage, they are obtained via the mixed logical dynamic model (MLDM) and measured currents, respectively. Then, the voltage deviation of each phase is employed as a fault variable. By this way, avoiding the use of additional hardware, and embedding easily in system. Furthermore, considering the impact of sampling error, parameter error, dead time, delay time, and transition time, the adaptive threshold is designed. Finally, simulations and experiments are executed to verify the effectiveness of the proposed method.

Aim to improve the power efficiency of the dual-active-bridge (DAB) dc–dc converter, an efficiency optimization scheme with triple-phase-shift (TPS) modulation using reinforcement learning (RL) is proposed in this article. More specifically, the Q-learning algorithm, as a typical algorithm of the RL, is applied to train an agent offline to obtain an optimized modulation strategy, and then the trained agent provides control decisions online in a real-time manner for the DAB dc–dc converter according to the current operating environment. The main objective is to obtain the optimal phase-shift angles for the DAB dc–dc converter, which can achieve the maximum power efficiency by reducing the power losses. Moreover, all possible operation modes of the TPS modulation are considered during the offline training process of the Q-learning algorithm. Thus, the cumbersome process for selecting the optimal operation mode in the conventional schemes can be circumvented successfully. Based on these merits, the proposed efficiency optimization scheme using the RL can realize the excellent performances for the whole load conditions and voltage conversion ratios. Finally, a 1.2-KW prototyped is built, and the simulation and the experimental results demonstrate that the power efficiency can be improved by using the optimization scheme based on the RL.

This article proposed a current sharing strategy for three-phase series capacitor boost converter for continuous conduction mode operation. The phase current can be automatically balanced based on the charge-balance principle, without any additional sensors or devices. And a uniform output voltage expression in full duty ratio range can be obtained. The mechanism of unbalanced current is disclosed. A current sharing strategy is proposed by adjusting the duty ratio in adjacent phase. The selection of capacitor and inductor is discussed via the analysis of topological operation and current deviation. The related characteristics are presented, including uniform output expression, continuous duty ratio operation, insensitivity to inductor parameters, loos analysis, and device stress. Experimental results on 100-W prototype are provided to confirm the feasibility of the proposed strategy.

To better predict the high-frequency switching operation of the half-bridge circuit in power converters, the value of the parasitic elements of these devices must be accurately evaluated. A new MOSFET-based half-bridge circuit parasitic inductances extraction method using two-port S-parameters is proposed in this paper. By changing the terminal connection of the half-bridge circuit, we can treat it as several different two-port networks, and then detailed network analysis can be performed on it. The parasitic parameters of multi-terminal actual circuits such as half-bridge can be extracted accurately and quickly through the simple measurement steps and calculations of the proposed method.

In this paper, the problem of modeling and control for DC-DC converter is investigated. A novel switched system model is established and an asynchronous control strategy is designed. Firstly, the DC-DC converter is modeled by the semi-Markov switched system with uncertainty and external disturbance. In which, the change of resistance parameter and the jump of input voltage are considered. Additionally, the sojourn-time of the switch is considered in the new model, in this way, it can be more accurately to depict the dynamic behavior of the plant. Then, in order to guarantee the stability of the plant, a state feedback asynchronous controller is proposed. Furthermore, the stability conditions of the closed-loop system with a prescribed H∞ index factor are given and the controller gains are solved. Finally, a numerical simulation and a practical experiment are executed to verify the superiority of proposed control strategies.

In order to guarantee the system reliability and enhance post-fault maintenance efficiency of inverters, this paper presents an current observer-based online open-switch fault diagnosis method for the voltage-source inverters (VSI). Analyzing the state space model of VSI when fault occurs, a state observer of the system is built to estimate phase currents. Once the open-switch fault occurs, the current residual vector between the estimated currents on observer and the measured currents, and fault diagnosis is realized by exploiting the featured amplitude and phase of the current residual vector. In order to realize on-line diagnosis with high reliability and speed, the average value of current residuals in a fundamental period is obtained and Clark transformation is performed so as to acquire vector angle. In addition, the sum of absolute values of measured currents is normalized to serve as the sign of fault occurrence. The simulation and experimental results show the effectiveness of proposed method.

In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn- on of part power switch and soft turn- off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis.

Wide voltage range converters are significant for photovoltaic power generation system, battery charging, etc. Resonant converter has been preferred topology for these applications, however, some demerits exist: 1) Difficult to realize wide voltage gain range and low circulating current losses; 2) Widely regulated switching frequency to adapt to wide voltage gain range; 3) Poor regulation at light load. Based on above-mentioned shortcomings, dual-resonance-core based step-up/down switched capacitor converter topology is presented in this paper. Utilizing hybrid control strategy, non-overlapping control strategy is used in the Buck-type mode and overlapping control strategy is applied in the Boost-type mode with common switching frequency range, and therefore, reduced frequency range in the presented converter is achieved. Moreover, wide voltage gain range can be obtained due to step-up/down capacity in the proposed converter. Furthermore, conversion ratio of proposed converter can be reduced to zero theoretically by using dual-resonance-core existed in the resonant switched capacitor converter. Finally, comprehensive operational principle analysis and performance analysis are provided, and a 48V to 2890V/100W prototype is built to verify the analysis.

To improve the speed and position observation performance of a Surface-Mounted Permanent Magnet Synchronous Motor (SM-PMSM), an improved sliding mode observer (SMO) based on the adaptive synchronization filter (ASF) and quadrature phase-lock loop (QPLL) is proposed. An adaptive synchronous filter based on feedback rotor position estimation from a QPLL is proposed to extract the fundamental signal of the back electromotive force (back-EMF). Then, a QPLL is linked to calculate the rotor position and speed according to the fundamental signal of the back-EMF, in order to effectively suppress the estimated harmonics and chattering and improve the observation accuracy of speed and position. Finally, the effectiveness and feasibility of the proposed observer approach are verified by simulation and dSPACE.