Study of Star-Delta Soft Switch to Extend AC Motor High Speed Operation Region

In traction application,speed range of motor is an important index for motor drives.In AC motor control,the maximum speed of the motor is limited by the output voltage capability of the traditional three-phase inverter with star connenction of windings.Switching the star connection to delta connection in high-speed range can extend the speed range.In order to extend the speed operation region,star-delta switch proposed by many literatures relies on mechanical relay,which needs a dead zone of tens of milliseconds and seriously affects torque output.Besides,the traditional method will cause current overshoot during the switch transient process,decreasing the device security and reliability.Aiming at the defects existing in the star-delta hard switching,this paper proposes a star-delta soft switching method.Without adding extra power electronics devices,DC-bus capacitor is used to provide the path of zero axis current in the transient process,which helps to achieve the smooth torque output and zero current switch in the transient.Experiments have been done to validate the performance of the proposed method.The switching transient from star to delta connection in the motor drive can be much more stable than hard switching method.

基于Soft Switch的IN/Internet互通研究

在分析ＩＮ与Ｉｎｔｅｒｎｅｔ互通接口的基础上．基于 Ｓｏｆｔ Ｓｗｉｔｃｈ的思想提出了用 Ｖｉｒｔｕａｌ Ｓｗｉｔｃｈ实现ＩＮ／Ｉｎｔｅｒｎｅｔ互通的方案；时Ｖｉｒｔｕａｌ Ｓｗｉｔｃｈ的逻辑实体、信令功能、体系结构和业务特点等问题进行了深入分析．并利用Ｖｉｒｔｕａｌ Ｓｗｉｔｃｈ实现了Ｖｉｒｔｕａｌ ＳＳＰ和Ｖｉｒｔｕａｌ ＳＣＰ．

下一代网络及其核心技术Soft Switch

下一代网络(NGN)是目前通信领域发展的热点,业界主要指采用软交换技术而构建的新型网络。文中简要地阐述了NGN的基本概念及其在通信领域中的各方面研究。详细地分析了其核心技术———软交换在网络服务中所能提供的技术支持及其在发展中的优势与不足。这对于未来网络发展有一定的指导作用。

Closed Loop Control of Bi-Directional Soft Switched Quasi Z-Source DC-DC Converter

Quasi Z-source converter is a single stage soft switched power converter derived from Z-source converter topology, employing an impedance network coupling the source with the converter. The quasi Z-source source converter can buck or boost the voltage and current flow is bidirectional. The duty cycle of the switch can be adjusted to maintain constant voltage during load change. To obtain constant output voltage, proper controller design is a must. This paper presents closed loop control of quasi Z-source converter using PI controller where controller parameters are estimated using the small signal model of the entire system. The transfer function of the system with AC sweep is used to obtain appropriate proportional and integral gain constants to reduce transient dynamics and to reduce steady state error.

COMPOSITE SOFT SWITCHING CONFIGURATION FOR INVERTERS USING BRIDGE LEG MODULES

The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial power equipment at high switching frequencies. This paper presents an adaptive composite soft switching configuration which combines snubber functions and resonant ZCS circuits for switches in inverters using power bridge leg modules. Simulation and experimental results are included.

SIMULATION AND EXPERIMENTATION OF THE ARC WELDING INVERTER USING THE SOFT SWITCHING TECHNIQUE

The FB-ZVZCS-PWM converter is realized by the way of subjoining block-capacitor into the FB-ZVS-PWM converter.At the freewheeling interval, the primary current is attenuated fast to zero and maintained.And then, power device of the static leg becomes a zero-current-switch (ZCS), power device of the shifted leg becomes a zero-voltage-switch(ZVS).Thus, on one hand IGBT (Insulated gate bipolar transistor) with tail current can be easily used in full-bridge soft-switching converter; on the other hand additional circuiting energy is greatly reduced.At the same time, less duty cycle loss, lower secondary parasitic resonance, wider soft-switching load range can be achieved.Based on the existing component models in the Pspice software package, a combined model of IGBT is established, in which a non-linear capacitor is introduced to replace the parasitic capacitor.Using this model, computerized simulation is conducted for the FB-ZVZCS-PWM soft-switching converter, the switching and energy-transferring characteristics of the power device are analyzed.Finally, based on the achievement above, a 10 kW arc welding inverter with FB-ZVZCS-PWM converter is deve- loped.The simulation results are testified by experiments.It is proved that by adopting appropriate models, computerized simulation is an effective and useful tool for the development of the arc welding inverter.

Implementation strategy for soft switching PFC with low output voltage

This paper proposes a novel implementation strategy for soft switching PFC whose circuit is simple and can achieve low voltage output directly. The main circuit adopts current mode full-bridge converter and all the power switches can realize ZCS or ZVS in the way of phase-shifted control, using the leakage inductance of the transformer, the junction capacitor of the switches and the stored energy of the output capacitor. The problems such as the function of phase-shifted link in control circuit, the implementation conditions of soft switching and bias restrained are analyzed. The adoption of constant frequency PWM control makes the design of the input and output filter link and the high frequency transformer simple. The transformation ratio regulation so as to achieve low voltage output and electrical insulation can be realized by using high frequency transformer.

Computer Aided Analysis ofAC Drive System with Soft Switching Inverter

The design of a general simulation package for AC drive system with soft switching inverter is discussed in this paper. This package is based on the secondary developing of the nonlinear control system simulation language SIMNON. Being constructed with modularization programming, the package can be used for general purposes conveuieutly and has strong graphic functions. The design principle for this simulation package is discussed in datail in this peper; and an application example (DSC controlled AC drive system with RDCLI) as well as its simulation results are given.

Principle and parameter design of arc welding inverter using soft switching technique

The soft switching are welding inverter reduces switching losses and improves operating envitonment of devicesby using Zero-Voltage -Transition (ZVT) technique .Step-by-step analysis of each timing interval and the associatingvoltage and current waveforms are included for the Full-Bridge Zero-Voltage-Switched PWM comerter,Numerous designequations supporting the phase-shifted soft switching technique are highlighte .

Controlling the output power of soft switching arc welding inverter by two-stage continuous PWM method

The full bridge zero voltage zero current switching(FB-ZVZCS),which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg,was a common circuit of soft switching arc welding inverter power source.However,when the duty ratio of leading leg was reduced to zero,the output power stayed the constant value instead of becoming zero.The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero.It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of parallel capacitors,and the output power also could be reduced by reducing the duty ratio of lagging leg.A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper.This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.

Soft switching arc welding power source using output inductor as resonant inductor

Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circuit is made up of the parasitic capacitance of the power semiconductors and the leakage inductor of the transformer primary. In this paper two saturable inductors as magnetic switches are added to secondary, so output inductor is always reflected to primary and assists resonant transition. Full ZVS is achieved under lower load current. The above mentioned investigated results are validated by the computerized simulation and hardware circuit experiment.

Soft-switching Grid-connected PV Inverter With Interleaved Flyback Topology

提出一种应用于单个光伏组件的软开关交错反激并网逆变器拓扑及其软开关控制策略。针对反激变压器漏感问题，提出漏感能量吸收回馈电路，实现了漏感能量吸收再利用，并实现了开关管漏源电压的钳位，提高了变换效率同时降低了开关管关断电压尖峰；提出基于数字处理器的反激变换器变开关频率谐振软开关控制策略，实现了开关管的零电压开通，同时改善了逆变器的电磁兼容特性；提出的交错并联反激逆变器有助于减小变压器和滤波器的体积，提高功率密度。详细分析变换器的工作原理，分析变开关频率谐振软开关控制方式的原理和实现条件，最后进行实验验证。

Design and Experimentation of FPGA-Based Soft-Switched Interleaved Boost Converter for Telecommunication System

This paper proposes the design and experimentation of digital control of soft-switched interleaved boost converter using FPGA for Telecommunication System. The switching devices in the proposed converter are turned on and off with Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) respectively. The circuit is operated in Continuous Conduction Mode (CCM) with various load ranges having duty cycle of more than 50%. The proposed converter is studied by developing the simulation module in MATLAB/SIMULINK. A PI controller is designed and implemented in FPGA to obtain a regulated DC output for line and load variations. Simulation and experimentation results are verified with a prototype development of the proposed converter. The results indicate that the converter performance is enhanced with closed loop control.

COMPUTERIZED SIMULATION AND EXPERIMENTAL RESEARCH ON SOFT-SWITCHING ARC WELDING INVERTER POWER SOURCE

Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.

Multi-mode controller IC for soft-switched flyback converter with high efficiency over the entire load range

This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with valley switching (CCMVS) is employed to realize soft switching so as to reduce turn-on loss of power switch as well as conducted electromagnetic interference (EMI). At light load, the converter operates in discontinuous conduction mode (DCM) with valley switching and adaptive off-time control (AOT) to limit the switching frequency range and maintain load regulation. At extremely light load or in standby mode, burst mode operation is adopted to provide low power consumption through reducing both switching frequency and static power dissipation of the controller. The multi-mode control is implemented by an oscillator whose pulse duration is adjusted by output feedback. An accurate valley switching control circuit guarantees the minimum turn-on voltage drop of power switch. The pro-totype of the controller IC was fabricated in a 1.5-μm BiCMOS process and applied to a 310 V/20 V, 90 W flyback DC/DC converter circuitry. Experimental results showed that all expected functions were realized successfully. The flyback converter achieved a high efficiency of over 80% from full load down to 2.5 W, with the maximum reaching 88.8%, while the total power consumption in standby mode was about 300 mW.

Simulation on Soft-Switching PWM Converter with High Power Factor

A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (zero voltage switching) mode, therefore the loss is reduced and EMI (electromagnetic interference) is suppressed. The paper analyzes the operation of ZVS, and discusses the methods for maintaining a unit power factor and constant DC voltage. Changing the modulation index M and the phase angle θ keeps the input current in phase with the voltage. It also keeps the current sinusoidal, and ensures a constant output voltage.

RESEARCH & DESIGN OF 60 kW SOFT-SWITCHING PLASMA CONVERTER

有由利用吸引的电感，漏电感和分布式的电感软开关的完整的范围的 A 小说 60 kW 血浆变换器被介绍。当前的注射转移阶段的技术成功地被介绍进软切换的血浆变换器的研究。变压器的磁性的偏爱和交换部分的保护被解决。测试声明电源供应有优秀特征和更高的效率并且能遇见大电源血浆过程的需求很好。

Analysis of Soft-Switched High Frequency AC-AC Converter for Induction Motor Drive

The systematic mathematical analysis of the high frequency soft-switched AC-AC converter is proposed for variable frequency induction machine load in this paper. Both PWM and square-wave modes of operation have been considered. The frequency relation and phase unbalance problem due to discrete time integral half-cycle switching has been discussed in the beginning. Then, generalized Fourier series have been derived for output voltage, output current and supply current in two modes.The analytical results help to understand tbe converter characteristics, design optimally a convertermachine system of arbitrary capacity considering the various trade-off parameters.

Effects of Direct Switching Dual Bronchodilators between Dry Powder and Soft Mist Inhalers in COPD Patients

Objective: Dual bronchodilation with long-acting muscarinic antagonist and long-acting β2-agonist combinations are available worldwide in COPD patients. However, the choice of agents remains under debate. We hypothesized that switching devices between dry powder and soft mist inhalers without a wash-out period to mimic clinical practice would improve clinical symptoms and lung function. The aim of this study was to examine the effects of switching between once-daily glycopyrronium/indacaterol (GLY/IND) or umeclidinium/vilanterol (UMEC/VI), dry powder inhalers, and tiotropium/olodaterol (TIO/OLO), a soft mist inhaler, in COPD patients. Methods: This was a prospective, open-label, 8-week, observational study with follow-up. Subjects included 57 COPD patients, who attended outpatient clinics at Shizuoka General Hospital for routine check-ups between February and December 2015, receiving GLY/IND (50/110 μg) or UMEC/VI (62.5/25 μg). After an 8-week run-in period, medications were switched to TIO/OLO (5/5 μg). Study outcomes included patient’s global rating (PGR), modified MRC (mMRC), COPD assessment test (CAT), and spirometric and forced oscillatory parameters after 8 weeks. PGR used in this study was a 7-point scale ranging from 1 to 7, with 4 in the middle. Patients who consented to switch from TIO/OLO to GLY/IND or UMEC/VI were followed-up thereafter. Results: In total, 53 patients completed the study (mean age, 75 years;48 males and 5 females;GOLD 1/2/3/4 = 19/27/6/1;mMRC 0/1/2/3/4 = 14/22/12/4/1;UMEC/VI 26, GLY/IND 27). PGR, mMRC, and CAT improved in 20 (38%), 9 (17%), and 15 patients (28%), respectively. Respiratory system resistance at 5 Hz (R5), 20 Hz (R20), and the difference between R5 and R20 (R5 - R20) significantly improved. In a follow-up of 16 patients after switching from TIO/OLO to UMEC/VI (9) or GLY/IND (7), PGR, mMRC, and CAT improved in 5 (31%), 3 (12%), and 4 patients (25%), respectively, and R20 significantly improved (p = 0.011). Conclusions: Switching dual bronchodilators between dry powder and soft mist inhalers improves symptoms and airway narrowing in some COPD patients.