Z源逆变器直流链电压滑模控制研究

提出一种Z源逆变器直流链电压的滑模控制方法。首先指出直通占空比至Z源网络电容电压和直通占空比至直流链电压的传递函数均含有右半平面零点,但基于控制电容电压的间接控制比控制直流链电压峰值的直接控制更为优越;在此基础上,设计了以电感电流误差、电容电压误差和电容电压误差的积分为状态变量的直流链电压滑模控制器,推导了控制律和使系统满足存在条件和稳定条件的滑模系数范围。所设计的滑模控制器比PI控制器具有更快的动态响应,而且工作状态在较大范围变化时可保证系统稳定,鲁棒性强。通过仿真和实验证明了直流链电压滑模控制器的有效性。     

Z-源逆变器直流链升压电路控制器的研究

本文提出了一种PID控制器控制Z-源逆变器Z-源网络电容两端的电压,得到较为恒定的直流链电压.基于Z-源网络小信号模型和直通占空比调制信号传递函数的基础上,得到整个环路的开环增益,设计了PID控制器.该控制器具有抑制诸如电源电压波动、负载电流扰动等的功能.同时,由于增加了微分(D)调节,系统的动态性能和稳定裕度都得到了很大程度的改善;能够克服由于Z-源网络电容和直通占空比之间的非线性关系给系统带来的闭环控制器设计困难、系统的动态性能差等缺点,使控制器参数设计非常准确、简单,动态、静态有了明显的提高.通过仿真和实验结果验证了理论分析的正确性.     

Multilevel inverter modulation schemes to eliminate common-mode voltages

It is well known that conventional two-level pulsewidth modulated (PWM) inverters generate high-frequency common-mode voltages with high dv/dt. Similarly, commonly used multilevel inverter modulation schemes generate common-mode voltages. Common-mode voltages may cause motor shaft voltages and bearing currents and conducted electromagnetic interference (EMI). Premature motor bearing failures and electronic equipment malfunctions have been reported to be directly related to bearing currents and EMI. In this paper, approaches to eliminating common-mode voltage when using multilevel PWM inverters are presented. It is shown that inverters, which have an odd number of levels, will generate zero common-mode voltage by switching among certain states. Therefore, motor bearing currents will be eliminated and conducted EMI will be reduced. Both sinusoidal PWM and space-vector modulation (SVM) schemes are discussed and detailed comparative simulation results between conventional and novel modulation schemes are provided. The value of the proposed technique is demonstrated experimentally by applying the novel SVM approach to a conventional multilevel inverter.     

Multilevel inverter using cascaded 3-phase transformers with common-arm configuration

In multilevel inverter development for 3-phase applications, total number of transformer in the circuit can be reduced by using of cascaded 3-phase transformer circuit instead of single-phase transformer circuit. In the scheme, total number of switching components in the circuit is still a drawback to achieve lower cost and smaller size of the inverter compared with conventional multilevel inverter. This paper includes a challenging method to reduce total switching components in the multilevel inverter by adopting common-arm structure.The proposed inverter has been operated by two control schemes, Newton-Raphson and Equal-area method. After theoretical and experimental comparison of the methods, we found that Newton-Raphson method is useful to eliminate a specific harmonic order. However, the method has a shortcoming in real time operation which is performed by iterative calculation of the nonlinear equations. With Equal-area method, we can easily find the switching angles by calculating a trigonometric function. It can sufficiently minimize Total Harmonic Distortion (THD) of output voltage in real time operation of Digital Signal Processor (DSP).     

A reduced-switch dual-bridge inverter topology for the mitigationof bearing currents, EMI, and DC-link voltage variations

This paper presents a reduced-switch-count dual-bridge inverter approach for the mitigation of motor bearing currents and electromagnetic interference (EMI). The proposed inverter employs two four-switch inverters and is controlled to generate balanced excitation of dual-voltage-rating induction motors under pulsewidth modulated operation. The proposed approach eliminates the common-mode voltage and, thus, prevents the motors from premature bearing failures in addition to reducing the conducted EMI. Compared to the conventional four-switch inverters, the proposed inverter also eliminates the single-phase circulating current and voltage variations across the DC-link capacitors, which allows smaller capacitance to maintain the DC-bus voltage. Theoretical analysis as well as simulation and experimental results are presented to verify this concept     

Study of dead time of PWM rectifier of Voltage-source inverter without DC-link components and its operating characteristics of induction motor

A voltage-source inverter without dc-link components is an ac-to-ac converter having dual bridges of a pulsewidth-modulated (PWM) rectifier and a PWM inverter that can be controlled independently. While conventional matrix converters have disadvantages, such as a complicated commutation scheme and necessity of a large-sized clamp circuit, commutation, and protection of our inverter can be implemented easily. In order to control the PWM rectifier and the PWM inverter independently, snubber circuits for the PWM rectifier are required to assure the path of load current during dead time. In this paper, analytical method of a snubber circuit and operating characteristics of a snubber circuit are described when a 0.75-kW induction motor is driven by our inverter.     

谐振直流环节逆变电源研究

谐振电路的Lr,Cr受MSPWM（改进的脉宽调制）方式控制,在调制波的半个周期内产生一连串的准正弦脉冲,其峰值包络线为半波正弦。由周波变流器变换为正负半周对称,包络为正弦波的脉冲群序列,经滤波便得到光滑的正弦波输出,逆变器的电压环用于稳定电压输出,电流环调节载波频率,使负载获得足够的功率,直流谐振环节的主控开关具有良好的软开关特性,周波变流器均为零压开关,文章详细分析了各工作阶段的原理,并进行了仿真,最后给出了实验结果。     

SVG的直流电容选择分析

SVG中逆变器直流电容的选择与逆变器结构、控制策略、线路参数等都有很大的联系。从矢量分析的角度出发,通过RLC动态过程的数学模型,分析SVG直流电容的大小在不同逆变器结构和控制方式下对系统的影响;在保证系统动态稳定条件下,同时给出了不同系统结构和负载扰动下的电容选择范围。     

直流支撑电容器杂散电感测量方法研究

自1997年第一条柔性直流输电试验工程在瑞典Hellsjon投运以来,经过多年的发展,国内外已建成并投运数十条柔性直流输电线路,但模块化多电平结构的柔性直流输电线路在2010年左右才开始投入建设、运行,总体运行时间较短,各设备运行参数仍处于积累阶段.对于MMC功率模块中使用的直流支撑电容器(DC?Link capacitor),对于其具体使用工况和应用条件等详细参数仍需要进一步的研究,因此,对于此类电容器的试验条件和方法仍有待研究,本文从实际应用角度出发,分析了杂散电感测量试验的目的,讨论了相关试验方法,可为实验室实施提供一定参考.     

光伏逆变器中DC-link电容的选型计算

DC-link电容是光伏逆变器直流侧电路的重要组成部分,其设计选型对逆变器的性能、体积、重量及成本均有一定影响.以单级三相全桥拓扑的光伏逆变器为例,重点讨论了薄膜电容的额定电压、容量及纹波电流等参数所需满足的要求,进行了理论分析、计算和仿真,以期对实际应用中的电容选取提供参考.     

有源电力滤波器最小直流侧电压设计

分析了三相4线制并联型有源电力滤波器的原理,并建立系统的单相模型。在此基础上,通过数学推导得出APF正常运行所需的直流侧最小电压值。对比传统依靠经验确定的直流侧电压值,运用所提出的最小电压值设计,可以在保证系统正常运行和补偿效果的前提下,使直流侧电压维持在所需的最小值,系统因直流侧电压产生的电能消耗及开关损耗将得到有效减小。通过APF样机实验,结果证明APF直流侧最小电压值推导的正确性和优越性,并讨论了直流侧电压对APF补偿效果的影响。     

H桥级联型整流器直流电压平衡控制改进算法

直流母线电压平衡控制是H桥级联型整流器（CHBR）主要的研究问题。为此在建立CHBR的数学模型基础上,分析了一种基于比例-积分（PI）调节器的CHBR直流电压平衡控制算法,并针对其不能空载运行的问题展开研究,利用相量图法揭示了该方法在空载时失控的内在机理;同时根据分析的结果提出了改进算法。改进算法的主要特点是通过使各功率单元的交流侧电压基波相位保持相同来实现空载条件下的电压控制,它不仅适用于直流电压给定值相同或者不相同的CHBR控制,同时也易于扩展到多单元的CHBR。对所提的算法进行了仿真研究,并搭建两单元CHBR的实验样机,对文中提到的改进算法进行了实验验证。实验结果表明了改进算法的有效性,同时也验证了改进算法和原算法在空载运行特性上的差异。     

两级单相光伏并网逆变器母线电压控制策略

传统的两级光伏并网逆变器常常采用在直流母线处并联大容量的电解电容作为前后两级的功率解耦方法,电解电容具有体积大、寿命短等缺点,成为制约逆变器寿命和可靠性的关键性因素。该文提出一种应用于两级单相光伏并网逆变器直流母线电压控制方法。所提出的控制方法基于光伏板输出能量、直流母线电容存储能量和逆变器交流输出能量守恒分析,在该分析的基础上得到一个快速的直流母线电压控制器,快速的响应意味着可以采用更小的直流母线电容,从而降低逆变器系统的体积和成本。基于Matlab/Simulink下的系统模型的仿真验证了所提出控制方法的可行性与有效性。     

十二相H桥变频器直流支撑电容分析研究

直流支撑电容的设计是变频器设计的一个重要方面,重点进行了十二相H桥变频器的直流支撑电容研究,在分析单相H桥直流支撑电容的基础上,提出了一种新方法来求取十二相H桥支撑电容纹波电流有效值的解析表达式及其谐波频谱。最后通过Matlab仿真和实验验证了该方法的有效性。     

变频空调器全数字化SPWM型逆变器研究

面对竞争日益激烈的市场,对变频空调器的性能价格比要求越来越高,一方面要最大限度地降低成本,另一方面要使产品性能达到或领先国内国际先进水平,我们必须立足国内,自行开发变频调速技术及模糊控制技术。针对国际国内市场需求,我们研究了适合于交流变频一拖多的变频压缩机逆变器,其中变频调速采用交—直—交ＰＷＭ控制方式,变频功率放大电路用最新ＩＧＢＴ实现,这种ＩＧＢＴ功率器件不需反向关断控制电压,驱动电路简单可靠,与采用现有国际市场上的适用于变频空调器的ＩＰＭ功率模块相比,价格大幅度降低,并可使ＰＷＭ载波频率提…     

一种APF直流侧电压波动分析及其吸收电路设计

此处根据瞬时功率平衡理论,对并联有源电力滤波器(SAPF)的直流侧电压波动进行了详细地分析,得到了SAPF直流侧产生波动的原因,并建立了相应的模型.更进一步地分析发现直流环节电压纹波会严重影响SAPF的输出电流畸变率,从而影响SAPF的补偿性能.因此,此处设计了一种直流环节电压纹波抑制电路(RSC),此处设计的RSC可...     

浅谈油浸式直流支撑金属化电容器的工艺控制

通过优化比较不同的金属化膜、卷绕方式、卷绕张力、卷绕错边等卷绕参数;压紧系数;热聚合的时间和温度参数;喷金工艺参数和喷金灰污染的控制;真空浸渍的时间、温度和真空度以及油介质的水分和残余气体控制;检漏与热老练试验的温度和时间参数等工艺条件,提出选择合理的工艺参数,形成一套完善的生产油浸式直流支撑金属化电容器的工艺。     

Voltage source inverter

A design optimization tool is developed for a three-phase voltage source inverter (VSI) with diode frontend rectifier. The insulated gate bipolar transistor (IGBT)-based pulsewidth modulation (PWM) voltage source inverter with diode front-end rectifier has become the converter of choice for three-phase ac-fed general-purpose industrial motor drives. The converter power stage, which mainly consists of the front-end rectifier, the inverter, the dc link capacitor, the harmonic and electromagnetic interference (EMI) filter, and the thermal management system, as shown in Figure 1 with a motor load, is the primary contributor to the overall converter cost and size. Since there are interdependencies and tradeoffs among components or subsystems in the power converter, it is very desirable to have a systematic methodology and tool for achieving a cost-optimized or size-optimized converter design while meeting the system performance requirement. A design tool will also reduce the development cycle and effort.     

双向电流源高频环节静止变流器的设计

设计了推挽双向电流源高频环节静止变流器部分,并分析了电路构成和电路等关键参数,最后通过实验说明推挽双向电流源高频环节静止变流器的可行性,同时具有拓扑简洁、使用器件少、控制电路简单、调试方便、系统静态稳定范围大、动态响应速度快等优点,在低输入电压的小功率场合有良好的应用前景。