Since that high-frequency isolated resonant converters are featured with low switching losses due to wide soft-switching operation range, to minimize the resonant tank current is able to enhance the overall system efficiency and reduce the component stresses as well. In this work, a bidirectional series resonant converter under phase-shifted modulation combined with a modified pulse-width modulation gating scheme is addressed. The modified pulse-width modulation gating scheme is helpful to keep more switches operating in zero-voltage switching at light load. According to the steady-state analysis with fundamental-harmonic approximation approach, a specified control strategy with minimum rms tank current based on three control dimensions is proposed in closed form. The validity of the proposed control strategy is verified through experimental tests. Compared with existing control strategies for minimum current operation, the proposed control strategy demonstrates comparable performance in depressing conduction loss and wider soft-switching range as well so that it is able to achieve high efficiency especially at light load.

To enhance the overall efficiency of a dual-bridge resonant converter, a new asymmetric pulsewidth modulation (PWM) control named extended pulsewidth modulation (EPWM) with both variable pulsewidth and variable symmetry is introduced in this article, which is applied to the high-voltage-side bridge of the converter and is combined with phase-shift control to form a 3-D gating scheme. A specified control strategy based on the 3-D gating scheme is then derived for the purpose of minimum tank current operation. Thanks to the flexibility brought by EPWM, full zero-voltage switching (ZVS) operation range is maintained as large as that of a conventional PWM-based minimum current trajectory, and only one switch loses ZVS at light load. The modulated voltage pulsewidth is kept at high level in a wide load range, which compromises the by-effect of high-order harmonics due to asymmetric modulation. Besides, the backflow power on both sides is almost minimized naturally. Therefore, the proposed control trajectory can have better performance in a light-load region than previous reported solutions. Experimental results prove the accuracy and effectiveness of the proposed minimum current operation with wide ZVS range and show the improvement of overall conversion efficiency.

This paper presents a novel zero-sequence-current suppression method for open-end winding permanent magnet synchronous motor. Firstly, a pair of orthogonal DC signals proportional to the amplitude of the zero-sequence-current are detected through the orthogonal gate-integral circuit, which will be regarded as the projection of the zero-sequence-current on the three times synchronous rotating coordinate system. Secondly, by imitating the idea of vector control, the two projections are tracked respectively, and two orthogonal voltage components are obtained. Finally, the zero-sequence-voltage for compensating the zero-sequence-current is obtained by performing synchronous rotation inverse transformation on the two voltage components. The algorithm is simple and can realize the error-free tracking of the zero-sequence-current by common PI regulator. It can not only significantly improve the suppression accuracy of zero-sequence-current, but also reduce the design difficulty of the controller. The experimental results verify the effectiveness and feasibility of this strategy.

This article proposes a novel modulation strategy forthe open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by dual three-level inverters with common dc bus. First, by constructing a virtual orthogonal zero-sequence current, the tracking of the sinusoidal signal is transformed into the tracking of the dc signal, which improves the performance of suppressing the zero-sequence current. Second, making use of the characteristic that the phase voltage of the OEW-PMSM can be controlled independently, the neutral point voltage is balanced by synchronously adjusting the reference voltages of the dual inverters in each phase, which does not need to inject zero-sequence voltage like in the traditional method and will not conflict with the suppression of the zero-sequence current. Finally, by carefully setting the adjustment direction and amplitude of the reference voltages of dual inverters, the switching times are reduced to the same level as that of the single inverter, and the switching loss of the two inverters is equalized. The experimental results verify the effectiveness and feasibility of this strategy.

In this brief, a single-phase single-stage semi-dual-active-bridge (SDAB) ac/dc converter with fully soft-switched and power-factor-correction (PFC) features is proposed for battery charging applications. The unidirectional SDAB dc/dc converter is properly designed and modulated to produce a sinusoidal charging current, such that the conventional bulky intermediate-stage electrolytic capacitors are not required. Meanwhile, the input PFC function can be realized easily in the dc/dc conversion stage by means of fixed-frequency single-phase-shift modulation. As the SDAB converter is designed to operate with just continuous current mode (JCCM) or discontinuous current mode (DCM), all power switches including diodes can be switched softly. Step-by-step analysis and design procedures for the proposed ac/dc conversion scheme are provided. Finally, this work is validated by both simulation and experimental tests.

For the open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by dual three-level inverters with a common dc bus, it is necessary to balance the neutral point (NP) voltage and suppress the zero-sequence current to improve system performance. The traditional methods to solve these two problems are usually contradictory and are difficult to obtain satisfactory results. This article proposes a novel modulation strategy to deal with this dilemma. In this strategy, the NP voltage balance is achieved by automatically equalizing the distribution proportion of the reference voltage of OEW-PMSM between the two inverters. At the same time, the strategy makes full use of the control freedom brought by dual inverters to control the three-phase voltages of OEW-PMSM independently, in order to ensure that the average value of zero-sequence voltage in a sampling period is zero in any case, and thus greatly reducing the zero-sequence current. The experimental results verify the effectiveness and feasibility of this strategy.