Naizhe Diao

In order to ensure continuous DC link current, the overlap time introduced in the switching process of the current source rectifier (CSR) can lead to undesirable harmonics and reduce grid-side current quality. To address this issue, a hybrid space vector modulation (HSVM) method is proposed. This method designs two current vector sequence modes by reconstructing the sequence of the dwell current vectors. Then, an adaptive threshold decision (ATD) method is introduced, which can dynamically select two sequence modes during the modulation process to solve the current sharing phenomenon. The proposed method no longer need to add overlap time in modulation and fundamentally eliminates the overlap time effect (OTE). Moreover, it can minimize the switching times by using reverse voltage to block the on-state switches. By comparing with the ideal five-segment space vector modulation, theoretical analysis, simulation and experimental results prove the effectiveness of HSVM in improving system performance and minimizing the number of switching operations.

This article proposes an open-circuit (OC) fault diagnosis method for voltage source inverters (VSIs) based on microfeature extraction and a third-order tracking differentiator. The proposed method is designed for complex operating conditions such as variable frequency and variable load. It enables effective diagnosis of both types I and II faults. First, a PWM-aligned masked averaging filter (PMAF) is developed. By constructing two averaging windows within each carrier period and masking the intermediate interval, the proposed filter effectively suppresses noise while preserving fault features. Second, a third-order linear tracking differentiator (LTD3) is employed to extract the second-order derivative of currents. The fault features are mapped into a unified second-order derivative domain. As a result, a unified fault criterion is established, eliminating the need for type-specific detection logic. On this basis, a unified fault diagnosis function is constructed to achieve fault detection and fault localization. Compared with existing methods, the proposed method shows improved diagnostic response speed, and maintains robustness under complex operating conditions, with an algorithmic complexity of $\bm{O}\mathbf{(1)}$ . Both simulation and experimental results validate the effectiveness of the proposed method.

To enhance the light-load efficiency of dual-active-bridge (DAB) converters under input-output voltage mismatches, this paper proposes an asymmetrical triple-phase-shift (ATPS) modulation strategy with indirectly reduced root mean square (RMS) current and extended zero-volatge-switching (ZVS) range. Specifically, the peak-to-valley current is minimized as an optimization objective, which helps indirectly reduce the root mean square (RMS) current and conduction losses. On the basis of minimizing the peak-to-valley current, one ZVS constraint is introduced to broaden the ZVS range, enabling 5–7 switches to achieve ZVS under light-load conditions, thereby further reducing switching losses. Moreover, a simple direct duty cycle (DDC) method is proposed, leveraging the global monotonic relationship between duty cycle and transmission power, thereby eliminating complex power calculations and significantly reducing computational time. Experimental results demonstrate that ATPS not only reduces RMS current but also enables more switches to achieve ZVS compared to several existing modulation strategies, validating its effectiveness and practicality for improving the efficiency of DAB converters.

In order to effectively reduce the current distortion caused by introducing overlap time, an overlap-time optimization space vector modulation (SVM) method based on vector sequential reconstruction (VSR-SVM) for current source converters (CSCs) is proposed. First, the rules that are not affected by the overlap-time effect (OTE) are identified, and the sequence of the current vectors is adjusted on this basis to eliminate the OTE within the carrier. Next, a modulation increment is added to the adjusted modulation signal to obtain a new modulation signal to remove the OTE between carriers. Then, the driving signals are obtained by comparing the new modulation signals with the carrier. Finally, the overlap time is added after the turn-off signals to correct the dwell time. This method intentionally modifies the modulation signals so that the effective dwell time of the current vector is the same as the ideal dwell time. Simulation and experimental results show that this method can effectively improve the current quality under different power factors, loads, overlap time, and modulation indices.