A Novel Square-wave Pulse Rotation Modulation Strategy for Modular Multilevel Converters

悬浮直流电容电压的均衡问题是模块组合多电平变换器（modular multilevel converter,MMC）的关键问题之一。提出一种可实现MMC直流电容电压平衡的方波脉冲循环调制（square-wave pulse rotation modulation,SWPRM）策略,在保证合成的阶梯波输出波形不变的前提下,根据MMC的拓扑结构和工作原理,对传统方波脉冲列进行脉冲优化,并按照一定的次序和切换周期进行循环和判断反相调整,获得的循环方波脉冲列作为最终驱动脉冲用于实现对MMC的控制。实验结果表明,采用提出的方波脉冲循环调制策略无需任何电容电压控制措施,在较低开关频率下,实现了MMC各功率单元间有功能量的平均分配和直流电容电压的均衡。

PULSE SHRINKING TIME-TO-DIGITAL CONVERTER FOR UWB APPLICATION

A kind of architecture of Time-to-Digital Converter(TDC) for Ultra-WideBand(UWB) application is presented. The proposed TDC is based on pulse shrinking, and implemented in a Field Programmable Gate Array(FPGA) device. The pulse shrinking is realized in a loop containing two Programmable Delay Lines(PDLs) or a two-channel PDL. One line(channel) delays the rising edge and the other line(channel) delays the falling edge of a circulating pulse. Delay resolution of PDL is converted into a digital output code under known conditions of pulse width. This delay resolution measurement mechanism is different from the conventional time interval measurement mechanism based on pulse shrinking of conversion of unknown pulse width into a digital output code. This mechanism automatically avoids the influence of unwanted pulse shrinking by any circuit element apart from the lines. The achieved relative errors for four PDLs are within 0.80%–1.60%.

Pulse Skipping Modulated Buck Converter - Modeling and Simulation

Modeling and simulation results of a pulse skipping modulated buck converter for applications involving a source with widely varying voltage conditions with loads requiring constant voltage from full load down to no load is presented. The pulses applied to the switch are blocked or released on output voltage crossing a predetermined value. The regulator worked satisfactorily over a wide input voltage range with good transient response but with higher ripple content. Input current spectrum indicates a good EMI performance with crowding of components at audio frequency range for the se-lected switching frequency.

An Approach towards Pulse Data Transmission Using Modified Negative Luo Converter (MNLC) for Telecoms

Telecom sectors generally operate at negative voltages to reduce the effect of corrosion caused in the metallic wire due to electrochemical reaction while communicating signals. To feed those lines and to have an effective digital data transmission, a power electronic converter referred as Modified Negative Luo Converter (MNLC) is proposed in this paper. MNLC is a high gain converter in which the output voltage increases in geometric progression. This paper portrays a novel concept of a 50 Hz pulse data transmission through RLCG (Resistance-inductance-capacitance with a shunt conductance) transmission line using MNLC. Signal frequency of 50 Hz to be transmitted is anded with a high frequency pulse that charges and discharges MNLC and produces the boosted negative output voltage. The boosted output is again transmitted through the RLCG transmission line from which 50 Hz data pulse is retrieved at the output of the transmission line by comparing with a comparator signal. This sort of MNLC aided data transmission not only introduces less loss in its transmitted data but also overcomes various health hazards of conventional radio frequency (RF) communication. This technique also proves that any data bit stream can be transmitted and retrieved using the proposed high gain DC-DC converter. The simulation model of the proposed system is implemented in MATLAB for various switching frequencies with its prototype of the converter developed and the results are verified.

A novel ultrafast-convert hybrid pulse square-wave VP-GTAW process for aluminum alloys

A novel ultrafast-convert hybrid pulse square-wave variable polarity arc welding power source was developed. The variable polarity current which crossed zero with no dead time possessed the ultrafast converting speed and the series of ultrasonic pulse current were superimposed in the positive polarity current duration. A high-efficiency hybrid pulse variable polarity gas tungsten arc welding （HPVP-GTAW）process for aluminum alloys was achieved. With X-ray inspection, microstructure analysis, tensile tests and scanning electron microscopy （SEM） for fracture surface, the square butt welding cbaracteristics of 5A06, 2A14 and 2219 aluminum alloys were tested, respectively. Experimental results show that microstructure and mechanical properties of these aluminum alloy welded joints are influenced significantly by the introduction of ultrasonic pulse current. The weld quality is improved predominantly by the novel HPVP-GTA W process.

Four-quadrant Force Control with Minimal Ripple for Linear Switched Reluctance Machines

Linear switch reluctance machine(LSRM)has been tried to act as an alternative generator for direct drive linear wave energy converter(WEC).Many researchers have proposed new topologies of LSRM to improve the power density,efficiency and reliability.However,the control methods for LSRM applied in direct drive WEC have been paid little attention,especially control methods considering the wave energy generator operating characteristics.In this paper,according to the generator control requirements of the direct drive WEC,force control algorithm for LSRM operating in four quadrants without a speed closed loop is put forward.The force ripple of LSRM is suppressed using force sharing function method.The four-quadrant control is easy to realize requiring only phase currents information.Simulation results validate the proposed method and indicate that LSRM is able to be used as the generator for direct drive WEC.

A Review of Modular Multilevel Converters

模块组合多电平变换器（modular multilevel converter，MMC）具有高度模块化、易于扩展、输出电压波形好等特点，尤其适用于中高压大功率系统应用。首先介绍MMC的电路拓扑和工作原理，总结MMC的主要技术特点；然后分别回顾MMC在脉冲调制、直流电压控制、预充电、环流、谐波、数学模型、主电路参数设计、故障保护等关键问题的最新研究进展，以及其在电力传动、电能质量问题治理领域的工程应用现状，在此基础上指出MMC今后亟待研究的关键问题。相关研究结果表明，MMC在电力系统中有广泛的应用前景，是未来中高压大功率系统，尤其是高压输电技术的重要发展方向。

High Performance Control of Matrix Converter Fed Induction Motor Drive System

Matrix converter fed motor drive is superior to pulse width modulation inverter drives since it not only provides bi-directional power flow,sinusoidal input/output currents,unity input power factor,but also allows a compact design due to the lack of DC-link capacitors for energy storage.In this paper,model and control of matrix converter fed induction motor drive system are analyzed.A combined control strategy is simplified and improved,which realizes space vector pulse width modulation of matrix converter and rotor flux oriented vector control technique for induction motor drive simultaneously.This control strategy combines the advantages of matrix converter with the good drive performance of vector control technique.Experimental results demonstrate the feasibility and effectiveness of the proposed control strategy.

A Method of Peak Detecting for Nanosecond Pulse in Optical Performance Monitoring System

In optical performance monitoring system,the analog to digital converter is needed to detect the peak of nanosecond pulse and get the signal envelope.A scheme based on a designed anti-aliasing filter and analog to digital converter is proposed to broaden the nanosecond pulse and make it easier for the analog to digital converter to catch the peak of the nanosecond pulse.The experimental results demonstrate that,with the proposed scheme,the optical performance system needs less time to get the recovered eye-diagram of high speed optical data signal,and is robust to phase mismatch in the analog to digital converter circuit.

Design of a new vacuum Compton gamma-ray detector with clad metal electron-converter plate

A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher than that with Fe converter plate. The designed detector has the merits of well processed and static vacuum keeping and can be used for intense pulsed gamma ray detecting.

The Usage of the Digital Controller in Regulating Boost Converter

This paper proposes the modeling and simulation technique to analyze and design a Boost converter using generalized minimum variance method with discrete-time quasi-sliding mode to adjust the converter switch through a pulse width modulation (PWM), so as to enhance a stable output voltage. The control objective is to maintain the sensed output voltage stable, constant and equal to some constant reference voltage (8 volt) in the load resistance variation (24, 48, 240) Ω and input voltage variation (20, 24, 28) volt circumstances. This control strategy is very appropriate for the digitally controlled power converter and for the system requirement accomplishment, resulting high output voltage accuracy. The performance degradation in practical implementation can be expected due to noise, PWM nonlinearities, and components imperfection. The digital simulation using MATHLAB/Simulink is performed to validate the functionality of the system.

A General Approach for Direct Conversion of Single Phase AC to AC Converter for Induction Heating System

This paper signifies the study of modeling and simulation of a single phase matrix converter for induction heating system. The working principle and the control method, using PID are revealing in detail. The performance of the system is carried out in MATLAB/Simulink environment with pulse width modulation switching strategy by varying the duty cycle. PID control is employed to obtain the better performance for a specified input supply for various output frequencies. The proposed control strategy of AC to AC converter has been discussed with a wide range of operating frequencies and results in low Total Harmonic Distortion.

Design of low-power high-frequency digital controlled DC-DC switching power converter

This paper models a low-power high-frequency digitally controlled synchronous rectifier （SR） OUCK converter. The converter is a hybrid system with three operation modes. Digital PID controler is used. Key problems such as quantization resolution of digital pulse-width modulation （DPWM） and steady-state limit cycles of digital control switching model power supply （SMPS） are discussed, with corresponding solutions presented. Simulation of a digital control synchronous buck is performed with a fixed-point algorithm. The results show that the described approach enables high-speed dynamic performance.

Spectral Calculation of the Output Voltage of an Inverter with Bipolar Pulse Width Modulation

Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for powering induction furnaces, in audio technique. Spectrum of signals sampled by pulse amplitude modulation and output voltage spectrum of the converter with pulse width modulation have similar properties. Spectrum of signals sampled by pulse amplitude modulation contains a harmonic of frequency equal to the frequency of the modulating signal and the harmonics of frequencies equal to the sum of frequency of the modulating signal and multiples of the sampling frequency. The output voltage spectrum of the converter with bipolar pulse width modulation contains harmonic of frequency equal to the frequency of the modulating signal and harmonics of frequencies equal to sum of the frequency of the modulating signal and multiples of the frequency of the carrier signal. It also contains harmonics of frequencies equal to the sum of the multiples of the frequency of the modulating signal and the multiples of the carrier signal. The comparison analysis was carried out for the harmonics of the output voltage of the converter with bipolar pulse width modulation in time domain. The dependency of the amplitudes and frequency spectrum on the wave forms of the carrier signal and modulating signal was shown. Similarity of the output voltage spectrum of the converter and signal spectrum sampled by the pulse width modulation was also shown. Key words： Output voltage converter with bipolar pulse width modulation, spectral analysis, Fourier series, carrier signal, reference signal.

A Dual-Mode Step-up DC/DC Converter IC with Current-Limiting and EMI Reduction Techniques

This paper presents a novel dual-mode step-up （boost） DC/DC converter. Pulse-frequency modulation （PFM） is used to improve the efficiency at light load. This converter can operate between pulse-width modulation （PWM） and pulse-frequency modulation. The converter will operate in PFM mode at light load and in PWM mode at heavy load. The maximum conversion efficiency of this converter is 96%. The conversion efficiency is greatly improved when load current is below 100 mA. Additionally, a soft-start circuit and a variable-sawtooth frequency circuit are proposed in this paper. The former is used to avoid the large switching current at the start up of the converter and the latter is utilized to reduce the EMI of the converter.

Carrier dynamic overlapping switching frequency optimal pulse width modulation method for modular multilevel converters

Modular multilevel converters(MMCs) operate in the low modulation index region in many applications.However, when utilized at the low modulation index region, large harmonics appear in the output voltage, which degrade the performance of the MMC. To improve the harmonic characteristic in the low modulation index, the carrier dynamic overlapping switching frequency optimal pulse width modulation(CDOSFOPWM) method is proposed for the MMC here. The whole modulation index region is divided into three regions: high modulation index region, middle modulation index region, and low modulation index region. The carrier amplitude, carrier overlap ratio, and frequency of triangular carriers are chosen dynamically according to the modulation index region of the modulation signals, to achieve the optimal harmonic characteristic in the whole modulation index region and maintain the switching loss. The number of on-state submodules(SMs) can be calculated by CDOSFOPWM, and the selection of SMs is performed by a reducing switching frequency voltage balancing algorithm. Finally, the proposed method is verified by simulation and experimental results.

一种新型三电平变换器中点电压平衡调制策略

在大功率轨道交通装备领域中,三电平变换器因具有众多优点,在实际中得到广泛应用,但是也存在中点电压不平衡这一固有问题。为解决三电平中点箝位(NPC)型变换器存在的中点电压不平衡问题,减少输出相电流畸变情况,提高系统运行稳定性,文章提出了一种基于分析中点电荷量的双自由度新型中点电压平衡调制策略。该调制策略首先从数学分析的角度介绍了三电平变换器直流侧中点电压不平衡问题的原因;之后分析了在空间矢量脉宽调制(SVPWM)技术中,电压矢量输出序列对中点电压的影响;最后基于上述分析结果,改进传统的电压矢量输出序列,并基于改进序列的特点提出了一种新的双自由度中点电压平衡调制策略,通过双自由度的平衡因子调节作用时间。理论上,所提出的新型调制策略具有更多可控电荷量,相较于传统方法具有更良好的控制效果;仿真和试验结果验证了所提的新型调制策略对中点电压的控制效果具有更好的快速性和稳定性。综上所述,文章所提的新型双自由度调制策略可更有效解决三电平变换器存在的中点电压不平衡问题。

抑制级联H 桥变换器共模电压的简化SVPWM 策略

为解决传统空间矢量调制策略难以拓展至高电平数级联H桥多电平变换器,以及抑制级联H桥多电平变换器调制策略实现过程中产生的共模电压的问题,本文提出一种简化空间矢量调制策略。该策略基于α'β'坐标系,通过判断空间矢量所处区域,得出其边界开关状态,再引入修正参数K对边界开关状态进行修正,以此提高策略的快速性并完成共模电压抑制。仿真和实验结果表明该策略实现简单,可以将级联H桥多电平变换器共模电压抑制在最小变化范围内。

一种混合滞环控制的LLC控制器应用研究

为优化LLC变换器的瞬态性能、间歇工作特性及轻载效率,提出了一种LLC的混合滞环控制方法及变换器实现方案。在深入分析混合滞环控制原理、对称半桥LLC变换器设计方法的基础上,给出基于混合滞环控制的模拟控制器应用方法及200 W对称半桥LLC变换器的关键参数设计,包括控制器外围电路设计,对称半桥电路设计,驱动电路设计,LLC谐振腔各项参数设计等,并通过实验样机进行详细验证。实验结果表明,所提出的混合滞环控制方法及控制器的应用设计科学可行。

牵引电机轴承电蚀关键影响因素研究

轴承电蚀一直是困扰电机研发人员的难题之一。对大量发生轴承电蚀的电机进行分析,发现采用变频电源供电的电机最易发生轴承电蚀,经研究发现变流器共模电压是导致轴承电蚀的重要因素之一。基于地铁车辆牵引传动系统搭建仿真模型,从变流器主电路拓扑结构和脉宽调制策略两个方面,深入分析了变流器共模电压对轴承电蚀的影响机理。研究结果可为制定轴承电蚀抑制方案提供有力的理论支撑。