New Isolated Single-Phase AC-DC Converter for Universal Input Voltage Ming-Rong Lee*, Lung-Sheng Yang†, and Chia-Ching Lin*

New Isolated Single-Phase AC-DC Converter for Universal Input Voltage Ming-Rong Lee*, Lung-Sheng Yang†, and Chia-Ching Lin* *†Dept. of Electrical Engineering, Far East University, Tainan City, Taiwan Abstract This paper investigates a new isolated single-phase AC-DC converter, which integrates a modified AC-DC buck-boost converter with a DC-DC forward converter. The front semi-stage is operated in discontinuous conduction mode (DCM) to achieve an almost unity power factor and a low total harmonic distortion of the input current. The rear semi-stage is used for step-down voltage conversion and electrical isolation. The front semi-stage uses a coupled inductor with the same winding-turn in the primary and secondary sides, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. The discharging time can be shortened. In other words, the duty ratio can be extended. This semi-stage can be operated in a larger duty-ratio range than the conventional AC-DC buck-boost converter for DCM operation. Therefore, the proposed converter is suitable for universal input voltage (90~264 Vrms) and a wide output-power range. Moreover, the voltage stress on the DC-link capacitor is low. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.
 LINK
http://jpe.or.kr/archives/view_articles.asp?seq=760

Modeling and Control Method for High-power Electromagnetic Transmitter Power Supplies Fei Yu† and Yi-ming Zhang*

Modeling and Control Method for High-power Electromagnetic Transmitter Power Supplies Fei Yu† and Yi-ming Zhang* †*College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing, China
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=769

Study on the Influence of Distribution Lines to Parallel Inverter Systems Adopting the Droop Control Method Xuan Zhang*, Jinjun Liu*, Zhiyuan You†, and Ting Liu*

Study on the Influence of Distribution Lines to Parallel Inverter Systems Adopting the Droop Control Method Xuan Zhang*, Jinjun Liu*, Zhiyuan You†, and Ting Liu* *†Dept. of Electronic Engineering, Xi’an Jiaotong University, Xi'an, China Abstract This paper takes into account the influence of the different impedances of distribution lines on power distribution among inverters when the inverters are paralleled with the droop control method. The impact of distribution lines on the power distribution of inverters can be divided into two aspects. Firstly, since the distributed generators are in low voltage grids, there is resistive impedance in the distribution lines, which will cause control coupling and reduce system stability. The virtual negative resistive impedance of inverters is adopted in this paper to neutralize the resistive element of distribution lines and thus make the distribution line impedance purely inductive. Secondly, after solving the resistive impedance problem, the difference in the inductive impedance value of distribution lines due to the low density of distributed generators will cause an unequal share of reactive power. With regards to this problem, modification is put forward for the droop control strategy to share the reactive power equally. The feasibility of the design is validated by simulation and experimental results.
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=771

Control Method for Reducing the THD of Grid Current of Three-Phase Grid-Connected Inverters Under Distorted Grid Voltages

Control Method for Reducing the THD of Grid Current of Three-Phase Grid-Connected Inverters Under Distorted Grid Voltages Thanh-Vu Tran*, Tae-Won Chun†, Hong-Hee Lee*, Heung-Geun Kim**, and Eui-Cheol Nho*** *†Dept. of Electrical Engineering, University of Ulsan, Ulsan, Korea **Dept. Of Electrical Engineering, Kyungpook National University, Daegu, Korea ***Dept. of Electrical Engineering, Pukyong National University, Busan, Korea
Abstract This paper proposes a control method for reducing the total harmonic distortion (THD) of the grid current of three-phase grid-connected inverter systems when the grid voltage is distorted. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for the minimum point of the THD. Both the gain and angle of the compensation voltage at the minimum point of the THD of the grid current are derived with the variation of cut-off frequencies of the hardware LPF. Simulation and experimental results show the validity of the proposed control methods.
LINK
 http://jpe.or.kr/archives/view_articles.asp?seq=772

The Effect of Transformer Leakage Inductance on the Steady State Performance of Push-pull based Converter with Continuous Current Qian Chen†, Trillion Q. Zheng*, Yan Li*, and Tiancong Shao*

The Effect of Transformer Leakage Inductance on the Steady State Performance of Push-pull based Converter with Continuous Current Qian Chen†, Trillion Q. Zheng*, Yan Li*, and Tiancong Shao* †*School of Electrical and Engineering, Beijing Jiaotong University, Beijing, China Abstract As a result of the advantages such as high efficiency, continuous current and high stability margin, push-pull converter with continuous current (PPCWCC) is competitive for battery discharge regulator (BDR) which plays an important role in power conditioning unit (PCU).Leakage inductance yields current spike in low-ripple current of PPCWCCs. The operating modes are added due to leakage inductance. Therefore the steady state performance is affected, which is embodied in the spike of low-ripple current. PPCWCCs which are suitable for BDR can be separated into three types by current spike characteristics. Three representative topologies IIs1, IIcb2 and Is3 are analyzed in order to investigate the factors on the magnitude and duration of spike. Equivalent current sampling method (ECSM) which eliminates the sampling time delay and achieves excellent dynamic performance is adopted to prevent the spike disturbance on current sampling. However, ECSM reduces the sampling accuracy and telemetry accuracy due to neglecting the spike. In this paper, ECSM used in PPCWCCs is summarized. The current sampling error is analyzed in quality and quantity, which provides the foundation for offsetting and enhancing the telemetry accuracy. Finally, current sampling error rate of three topologies is compared by experiment results, which verify the theoretical analysis.
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=735