Constant-switching-frequency AC-DC converter usingsecond-harmonic-injected PWM

This paper describes the operation of an AC-DC converter employing second-harmonic-injected PWM. The boost converter operating on the rectified output uses a constant switching frequency PWM and a discontinuous current mode to reduce the total harmonic distortion in the input current. The implementation and the characteristics of the converter are presented     

Optimum Trajectory Switching Control for Series-Parallel Resonant Converter

The series-parallel resonant converter (SPRC) is known to have combined merits of the series resonant converter (SRC) and PRC. However, the SPRC has a three-element LCC structure with complex transient dynamics, and without control of the resonant circuit's dynamics, the converter's closed-loop bandwidth to switching-frequency ratio will be much reduced compared to that of pulsewidth-modulation (PWM) converters. This paper presents the optimal trajectory enabling any SPRC's steady state be achieved within one cycle. Dynamics using the state-plane analysis is presented, and the optimal state trajectory for transients is derived. Experimental results with comparison to frequency control show much reduced resonant circuit response time for step changes in output voltage. This improved resonant circuit control allows subsequent current and voltage-loop controls of the SPRC to be treated as that of a conventional PWM voltage source     

A high-efficiency,low-noise power solution for a dual-channel GNSS RF receiver

A high-efficiency low-noise power solution for a dual-channel GNSS RF receiver is presented.The power solution involves a DC-DC buck converter and a followed low-dropout regulator(LDO).The pulsewidth -modulation(PWM) control method is adopted for better noise performance.An improved low-power highfrequency PWM control circuit is proposed,which halves the average quiescent current of the buck converter to 80μA by periodically shutting down the OTA.The size of the output stage has also been optimized to achieve high efficiency under a light load condition.In addition,a novel soft-start circuit based on a current limiter has been implemented to avoid inrush current.Fabricated with commercial 180-nm CMOS technology,the DC-DC converter achieves a peak efficiency of 93.1%under a 2 MHz working frequency.The whole receiver consumes only 20.2 mA from a 3.3 V power supply and has a noise figure of 2.5 dB.     

变频技术在风电设备中的应用

主要围绕变频技术在风电设备中的应用展开研究,以变速恒频双馈风力发电机为研究对象。对发电系统中交流励磁控制方式常见的变频装置进行了比较分析,对选择的双PWM变换器交流励磁变速恒频风力发电系统的两个控制单元——网侧PWM变换器和转子侧PWM变换器进行了控制策略分析及仿真。     

Soft-switched DC/DC converter with PWM control

In this paper, a new power converter with two variations is proposed. A novel asymmetrical pulse-width-modulation (PWM) control scheme is used to control the power converter under constant switching frequency operation. The modes of operation for both variations are discussed. The DC characteristics, which can be used in the design of the power converters, are also presented. Two 50 W power converters were built to verify the characteristics of the converters. Due to the zero-voltage-switching (ZVS) operation of the switches and low device voltage and current stresses, these power converters have high full- and partial-load efficiencies. They are, therefore, potential candidates for high-efficiency high-density power supply applications     

A high-power high-frequency ZCS-ZVS-PWM buck converter using afeedback resonant circuit

This paper presents a buck DC-to-DC power converter using a novel lossless commutation cell for high switching frequency and high power operation. The proposed cell consists of a main and auxiliary switches, with ZVS and ZCS switching characteristics, respectively. The power converter control using this cell is realized by the PWM technique, with constant switching frequency operation. The complete operation principles, theoretical analysis, relevant equations, state-space phase, simulation and experimental results for the buck converter are presented     

变速恒频风力发电用双PWM变换器的协调控制

文章首先分析了双馈风力发电机的原理以及其数学模型,然后分析了变速恒频风力发电技术采用双PWM变换器常规控制策略,在此基础上提出了采用双PWM变换器的协调控制策略。最后利MATLAB/SIMULINK软件对整个风力发电系统进行仿真。结果表明此策略实现了风力发电机的变速恒频运行,另外在定子电流变化的同时,保持了恒定的功率因数,实现了对双馈感应电机的有功功率和无功功率的独立控制。     

Current-fed three-phase and voltage-fed three-phase activeconverters with optimum PWM pattern scheme and their performanceevaluations

This paper describes a new approach to select the optimum sinewave pulsewidth modulation (PWM) patterns suitable for a large-capacity current-fed active PWM power converter and a practical design procedure to determine circuit constants of a low-pass filter connected to suppress higher line current harmonics flowing into the utility-grid AC power source. A feasible test is implemented by building a prototype 500 kW three-phase current-fed PWM power converter which is designed and controlled on the basis of the proposed considerations. It is verified from a practical point of view that these new conceptual considerations are more effective and acceptable to minimize higher harmonic current components flowing into the utility-grid AC power source. This experimental setup provides highly efficient steady-state characteristics of the current-fed three-phase PWM power converter under the operating condition of a unity power factor correction and sinewave line current shaping schemes. Furthermore, this unique optimum PWM pattern derived from the theoretical method proposed here is conveniently applicable to a voltage-fed three-phase PWM converter. It is verified that this optimum PWM pattern provides excellent switching performance with a lower switching frequency mode than the conventional carrier-based PWM scheme     

An improved ZCS-PWM commutation cell for IGBT's application

An improved zero-current-switching pulsewidth-modulation (ZCS-PWM) commutation cell is proposed, which is suitable for high-power applications using insulated gate bipolar transistors (IGBTs) as the power switches. It provides ZCS operation for active switches with low-current stress without voltage stress and PWM operating at constant frequency. The main advantage of this cell is a substantial reduction of the resonant current peak through the main switch during the commutation process. Therefore, the RMS current through it is very close to that observed in the hard-switching PWM converters. Also, small ratings auxiliary components can be used. To demonstrate the feasibility of the proposed ZCS-PWM commutation cell, it was applied to a boost converter. Operating principles, theoretical analysis, design guidelines and a design example are described and verified by experimental results obtained from a prototype operating at 40 kHz, with an input voltage rated at 155 V and 1 kW output power. The measured efficiency of the improved ZCS-PWM boost converter is presented and compared with that of hard-switching boost converter and with some ZCS-PWM boost converters presented in the literature. Finally, this paper presents the application of the proposed soft-switching technique in DC-DC nonisolated power converters     

一个易于系统集成的变步长反馈数字DC-DC变换模块

提出了一种采用单比较器变步长反馈控制和占空比抖动方法的数字DC- DC变换模块.它用6位二进制分辨率占空比的PWM信号实现了7位的电压分辨率.变步长反馈控制的使用使得它具有比恒定步长方案更好的动态性能,而且没有过多增加控制器的复杂度.在1MHz的开关频率下,控制器自身功耗小于0 .5 m W(不含功率开关及驱动部分) .由于电路的模拟部分极少,因此易与数字系统进行单芯片集成.     

The ZVS-PWM commutation cell applied to the DC-AC converter

This paper presents the analysis of a DC-AC power converter using a zero-voltage-switching (ZVS) commutation cell. First, the authors show the cell applied to the buck power converter. The stages of operation are presented along with the main current and voltage equations. Next, they adapt the power converter to the regenerative-operation mode. Hence, the full-bridge power converter at low-frequency operation is connected in the DC-DC output stage (at high frequency). The main switches commute at zero voltage. The power converter operated at constant frequency with pulse-width modulation (PWM), and neither overvoltage nor additional current stress was observed by digital simulation. A design example and experimental results obtained by prototype, rated at 275 V and 1 kW, are also presented     

Improved small-signal analysis for the phase-shifted PWM power converter

A closed form cycle by cycle analysis forms the basis for a new zero-voltage switching (ZVS) phase-shifted PWM (PSPWM) full bridge power converter small-signal model. The paper derives the small-signal response equations. The PSPWM converter has an implicit "slew interval," making the converter dynamics difficult to analyze using traditional averaging techniques. The converter control to output transfer function under continuous conduction mode operation and using voltage-mode control does not exhibit a second order pole associated with the output L-C filter, making it different from a conventional PWM converter. This new PSPWM converter model shows that the output L-C filter is separated into two real poles, with one pole held at constant frequency independent of operating conditions. A characteristic pole depends only upon the converter switching frequency and inductor values. This characteristic pole is fundamental to understanding the PSPWM converter natural and forced responses. The new small-signal model is shown to be in excellent agreement with experimental results.     

A new high-power-factor three-phase AC-DC converter: analysis,design, and experimentation

This paper proposes a new high-power factor three-phase AC-DC power converter, which is composed of a line interphase transformer (LIT) and two three-phase diode rectifiers, followed by a pulsewidth modulation (PWM) DC-DC boost power converter. The active switch of the boost converter is gated at a constant frequency such that the AC input current is discontinuous. This procedure provides an input current shaping without the third, fifth and seventh harmonics. The currents that flow through the LIT and boost inductors have such a high-switching frequency that ferrite cores with a small size can be utilized. In addition, the output voltage is regulated by PWM to compensate for line voltage variations and load change. Theoretical analysis, design procedure and example, along with experimental results taken from a 6 kW laboratory prototype are given     

一种基于自适应峰值电流检测的模式切换电路北大核心

在降压转换器中，为了在不同的负载情况下获得高效率，常采用的方法是在重载时使用脉冲宽度调制(PWM),在轻载时使用脉冲频率调制(PFM),因此需要模式切换信号去控制整个降压转换器的工作状态，同时模式切换信号也可以用于自适应改变功率级电路中的功率管栅宽，减小功率管的栅极电容，提高整体电路的效率。文章设计了一个自适应峰值电流模式切换电路，用于产生模式切换信号，其原理是监控峰值电流的变化，产生峰值电压，将峰值电压与参考电压进行比较，得到模式切换信号，以决定降压转换器是采用PFM模式还是PWM模式。仿真结果表明，在负载电流0.5～500 mA范围内，该电路可以在两种调制模式之间平稳切换，其峰值效率可提升到94%以上。     

Current-clamped, modified series resonant DC-link power converterfor a general purpose induction motor drive

A new AC/AC power converter topology, in which all the switches operate in a resonant fashion to reduce switching losses, is proposed. The topology enables conduction-period control of individual current pulses, whereby pulse-width modulation (PWM) could be achieved to a fair degree of accuracy with the associated controller. The scheme implements current peak (resonant) limiting by a simple diode clamp. Improved switch utilization (voltage × current) and reduced part-count could be cited as the merits of the circuit over the previous soft-switched current-sourced AC/AC configurations. It is experimentally verified that the output PWM controller could be used to implement constant V/F operation, and the results are presented. In-depth design criteria for the topology that gives optimized voltage stresses are presented. A charge-based, line current feed-forward, mode-controller is introduced at the input and digitally verified. Feasibility of the simultaneous control over both input power-factor and smooth input-output line currents are studied and the digital verification is presented     

Analysis and Design of a Novel Three-Phase AC–DC Buck-Boost Converter

This paper proposes a novel three-phase ac-dc buck-boost converter. The proposed converter uses four active switches, which are driven by only one control signal. This converter is operated in discontinuous conduction mode (DCM) by using the pulsewidth modulation (PWM) technique, and the control scheme very easily and simply achieves purely sinusoidal input current, high power factor, low total harmonic distortion of the input current and step-up/down output voltage. Also, the proposed converter provides a constant average current to the output capacitor and load in each switching period. Thus, the ripple component of sixth times line frequency will not appear in the output voltage. Therefore, a smaller output capacitor can be used in the proposed converter. Moreover, the steady-state analysis of voltage gain and boundary operating condition are presented. Also, the selections of inductor, output capacitor and input filter are depicted. Finally, a prototype circuit with simple control logic is implemented to illustrate the theoretical analysis.     

Novel topologies for DC-DC converter with PWM control

Two topologies for the buck converter are presented. The first converter consists of two active switches whereas the second converter, derived from the parent twoswitch converter, consists of only one active switch. The main feature of this new converter is the ability to operate at a constant switching frequency using a simple PWM control. The design of the gate circuit is simplified as there is only one switch. The converter has a good efficiency, as is proved by the experimental results. The operation of the parent two-switch converter, from which the new single-switch converter is derived, is also presented to gain insight into the design of the new converter.     

State-space models for current programmed pulsewidth-modulatedconverters

State-space models are derived for pulse-width-modulated (PWM) converters operating at constant switching frequency under current programmed control. One model neglects the sample-and-hold effect of the current loop and is therefore representative of the traditional approach to modeling current programmed converters. The order of the model is the same as that of the power stage. A second state-space model is derived which incorporates the sample-and-hold effect. The order of this model is two higher than that of the power stage. A comparison of the two models is made which clearly demonstrates the superiority of the second modeling approach. As the models are in state-space form they may be quite readily used in a CAD package for general converter analysis and design, to determine all transfer functions and associated pole/zero locations of interest     

基于双向PWM变换器的微燃机发电系统起动／发电控制研究

针对微型燃气轮机（微燃机）发电系统的特点,建立了以电压型双向脉宽调制（PwM）变换器为功率变换装置的起动／发电控制模型。微型燃气轮机发电系统起动时,采用矢量控制;发电运行时,采用电压外环电流内环的双环PWM整流控制。仿真实验结果表明：起动时,高速永磁同步电机（PMSG）采用矢量控制比速度开环控制性能更优,减少了起动时间,满足快速起动的要求;发电运行时,与二极管整流相比,PWM整流能使交流侧电流跟踪发电机的感应电动势,功率因数约为1,降低了发电机侧的电流谐波,即减少了谐波热。同时保证了发电机在一定宽速范围内,输出直流电压稳定,并且在起动一发电过渡转换过程中,直流母线电压降落后,快速恢复为稳定值,满足平滑转换的要求。