The AC distributed generation system (DGS) typically requires a bidirectional DC–AC converter to interface the battery with the common AC bus. However, such system inherently generates second-harmonic current on the DC side, which may degrade the battery lifetime; meanwhile, bulky buffering components would reduce the power density. To address this issue, this paper proposes a single-stage bidirectional DC–AC converter for battery applications, employing an active power decoupling-based unipolar phase-shifted sinusoidal pulse width modulation (SPWM) control strategy. The operational principle involves rectifying the sinusoidal pulse width position modulation (SPWPM) waveform from the high-frequency (HF) transformer into SPWM pulses during either the positive or negative half-cycle via a cycloconverter circuit. By analyzing the rising and falling slopes of the decoupling inductor current, real-time duty cycle allocation of the power decoupling bridge arm switches is implemented, which effectively suppresses the second harmonic current. Additionally, design criteria for the decoupling capacitor and inductor are derived in detail. Experimental results from a 1 kVA 96 V DC/220 V 50 Hz AC hardware-in-the-loop (HIL) platform validate the performance of the converter, which features single-stage power conversion, low DC-side second harmonic current distortion, high-frequency electrical isolation, and high-quality grid-connected current. These findings provide a solution for battery-integrated AC DGS and electric vehicle charging/discharging interfaces.

In the traditional ZVT soft-switching DC-DC converters, the resonant energy transmission path is complicated and the auxiliary switches may operate in hard switching. This paper proposes an energy-feedforward ZVT soft-switching Buck converter, all the switches keep soft-switching operation, and the resonant energy is transmitted directly to the load through the forward transformer instead of returning to the source or indirectly flowing to load, which is conducive to improve the conversion efficiency. After theoretical analysis, the design process of key parameters is given, and verified through simulation. Finally, an experimental prototype is constructed with 200W output, 200kHz operating frequency. The experimental results show that soft-switching operation of all switches is maintained in load range from 10 % to rated power. Compared with the traditional hard-switching Buck, the voltage and current spike of the main switch are reduced largely, the efficiency is better in the whole test range, improved from 94.54% to 97.34% at full load.

The control system of new energy electric vehicles generally uses low-voltage batteries for power supply, including contactors that control the on-off of power lines. For this reason, contactors in cars are usually driven step up-down converters. This article compares and analyzes the driving schemes between constant-type current, stepped-type current, and curved-type current by modeling and simulating the electromagnetic mechanism of the contactor. The simulation results show that the contactor driven by the curve current has better dynamic characteristics. A prototype of contactor driver with $9\sim 18\mathrm{V}$ input was constructed based on the buck-boost converter. The experimental results showed that compared with the traditional constant-type current or voltage drive scheme, the curved-type current scheme reduced the number of bounces by 67%, the bounce time by 60%, and the closing time was only extended by 2ms. At the same time, the contactor holding power consumption was only 8.3% of the original, effectively optimizing the working performance of the contactor.

When the classical buck converter is applied with large step-down ratio, the operating duty cycle is too small, which leads to the decrease of conversion efficiency and even affects the control stability. In this paper, a wide output step-down converter with variable operating mode is proposed. According to the relationship between input and output voltage, the converter toggles between buck and D 2 buck mode, so that the operating duty cycle can be kept in a reasonable range. Based on one cycle control, a smooth mode switch control scheme is proposed. The key parameters of the converter with 100V input and $\mathbf{5}\sim \mathbf{50}\mathbf{V}$ output are designed. The feasibility of the converter and control scheme are verified by psim simulation platform. The steady-state duty cycle is maintained between 0.22 and 0.54.

In this paper, a single-stage high-frequency isolated battery charging and discharging converter is proposed. The circuit topology and control strategy of this DC-AC converter are deeply studied, and the secondary ripple current of the system is decoupled by Buck active power decoupling circuit to suppress the secondary ripple current of the DC side. The control strategy uses a bidirectional rectifier circuit to convert the sinusoidal pulse width and pulse position modulation wave of the high-frequency transformer into a sinusoidal pulse width modulation (SPWM) wave that outputs a positive half-cycle or a negative half-cycle. The secondary ripple power is transferred by calculating the on-duty ratio of the switch tube in the decoupling circuit. The theoretical analysis and simulation results show that the system can realize bidirectional power flow, single-stage power conversion, high-frequency isolation of input and output, and has the characteristics of simple circuit, high conversion efficiency, small size, low cost and wide application prospect.

The parasitic capacitance of the transformer is the critical coupling path for common-mode (CM) noise conduction. The voltage pulsation assigned on winding terminals of transformers caused by switch on and off process of semiconductors switches is the main CM noise sources to conduct CM noise. In order to analyze the CM transmission characteristic of the transformer, this paper proposed a two-capacitor transformer winding capacitance model for CM noise analysis in flyback converter. Based on this model, the CM noise conduction characteristics in flyback transformer under different circuit configurations in secondary side are analyzed, respectively. For verifying the effectiveness of the proposed model, insertion loss was introduced to evaluate the CM characteristics of the designed PCB planar transformer. Finally, the experiment results prove the effectiveness of the proposed transformer winding model.

Three-phase power factor correction (PFC) converters capable of step-down voltage are attractive in lower components voltage stress, and optimal design of following dc-dc stage, which is an alternative for next-generation datacenter power conversion. An improved three-phase step-down PFC converter (swiss rectifier) based on harmonic-current-injection (HCI) concept is proposed. It improves input current quality by eliminating switching dead zone of HCI network and avoids short circuit fault from hardware level. According to one-cycle control (OCC), a novel nonlinear control strategy (termed as closed-loop OCC) is presented, which reduces the impact of dc inductor current ripple on input current. The principles of the improved swiss rectifier and closed-loop OCC are analyzed in detail, verified by simulation and on an 80 kHz, 300 V/2 kW prototype with digital controller. At rated condition, input current THD < 2%.

LED has promised to replace conventional light sources with impressive economic and environmental saving because of the realization of high efficiency and long life time light sources. Reliability issue is a key factor affecting the lighting quality and life time of LED lighting system. Each LED system includes two major aspects; optical and electrical driver. The LED driver is one of the weakest components in the LED luminaries and they tend to degrade rapidly with increasing temperature. The effect of temperature on performance and reliability of LED driver is analyzed in this paper. A thermal simulation model based on a tapped-inductor quasi-resonant Buck LED driver was set up. The thermal field and thermal stress analysis of the driver was done by using the software EFD Pro 8.2. The losses from various components of the driver were calculated in detail. The histogram of losses in various components in the driver was given. Computer simulation and a prototype rated at 5W, with an input ac voltage of 176-265Vrms and an output current of 700mA has been implemented to verify the prediction.

The model of external-inductor induction lamp is deduced, based on the theory of transformer. With the model, its Electronic ballast is analyzed in frequency domain. The electronic ballast design procedure and experimental results are given, which verify the model and analysis.