基于电流无差拍和PI复合控制的新能源并网技术

为了提高新能源整个并网系统的性能,在分析无差拍控制和PI控制的工作原理基础上,提出了基于电流无差拍和PI复合控制的PWM逆变的控制策略。通过Matlab/Simulink建模仿真三相并网系统,采用LCL滤波器滤波。当系统接三相对称纯阻性负载和整流性负载时,将系统逆变电压与电网电压、逆变电流与电网电压进行比较,以及对三相逆变电流进行谐波分析。仿真结果表明,该并网控制策略能较好地跟踪电网电压,波形畸变较小、动态响应快。     

西门子70系列变频器过载能力分析及实际应用

本文主要介绍了对西门子70系列变频器的过载能力的分析以及在未对设备进行扩容改造的前提下使现有设备充分发挥过载能力满足新产品矫直工艺要求的实际应用。     

Harbourne constants and conic configurations on the projective plane

In this note we exhibit the so‐called Harbourne constants which capture and measure the bounded negativity on various birational models of an algebraic surface. We show an estimation for Harbourne constants for conic configurations on the complex projective plane with transversal intersection points.     

基于3D-DIFA的逆变器输出电压非线性失真分析

提出了一种基于三维双重积分傅立叶分析(3D-DIFA)对电压源型逆变器非方波开关波形中非线性失真谐波的建模方法。针对传统的双重傅立叶分析更适用于线性方波脉冲序列的局限,提出了一种三维双重傅里叶积分的单位单元模型,并以交错并联式零电流开关逆变器为例,分析了该拓扑中的输出波形非线性失真,且利用三维双重积分傅立叶分析对含非线性畸变的输出电压谐波建立了解析模型。结果显示,三维双重傅里叶积分分析的解析计算结果与仿真和实验结果一致,验证了上述方法的可行性和正确性。     

窄带波导滤波器物理尺寸的快速确定方法

介绍了窄带波导滤波器物理尺寸的快速确定方法。推导出一种用于计算耦合窗散射参数的显式表 达式,借此能够方便地结合电磁(EM)仿真软件确定耦合结构的物理尺寸。此外,考虑到补偿相位的影响,对于交叉 耦合中电耦合孔中心位置的确定给出了更加精确的修正方法。最后,用一个四阶交叉耦合滤波器实例验证了方法 的有效性。     

Quasi-Z源逆变器PMSM系统直流环节电压控制方法

可变直流环节电压控制能够提高电动机驱动系统的运行效率。目前,Z源逆变器电机系统直流环节电压参考值由电机电流和转速计算得到,但电机电流变化时,电压参考值会产生非必要波动,影响电机稳定运行。为降低参考电压波动对系统的影响,该文提出了一种直流环节参考电压线性计算方法。该文介绍了直流环节电压控制原理,并说明了推导方法。与一般方法相比,线性控制方法摆脱了电流波动对直流环节电压的影响。最后,通过仿真验证了该方法的可行性和有效性。     

Metal Halide Perovskite Arrays: From Construction to Optoelectronic Applications

Inorganic semiconductor arrays revolutionize many areas of electronics, optoelectronics with the properties of multifunctionality and large-scale integration. Metal halide perovskites are emerging as candidates for next-generation optoelectronic devices due to their excellent optoelectronic properties, ease of processing, and compatibility with flexible substrates. To date, a series of patterning technologies have been applied to perovskites to realize array configurations and nano/microstructured surfaces to further improve device performances. Herein, various construction methods for perovskite crystal or thin film arrays are summarized. The optoelectronic applications of the perovskite arrays are also discussed, in particular, for photodetectors, light-emitting diodes, lasers, and nanogratings.     

一种改进型逆变器控制策略的研究

通过比较单极性和双极性调制方式的优缺点,指出目前常用的单极性控制策略存在输出电压过零点振荡的现象。针对正弦波电压过零点附近的振荡情况,提出一种半周期工频半周期高频的逆变器控制策略,在低频臂换向处无占空比突变,从而有效解决了输出电压过零点振荡问题,提高了波形质量。经过仿真和电路实验与前快后慢逆变控制方式比较,证明了所提出的改进型逆变器控制策略的有效性。     

无源器件辅助换流的单相全桥软开关逆变器

为提高单相全桥逆变器的转换效率,提出了一种无源器件辅助换流的单相全桥软开关逆变器拓扑结构,通过在逆变器桥臂上增加辅助谐振电路,实现了开关器件的软开关动作.辅助谐振电路中无辅助开关器件,只含有电感、电容和二极管等少量无源器件,这有利于降低辅助电路的成本,而且不会使逆变器的控制策略复杂化.此外,在逆变器处于死区状态时,负载电流能通过辅助谐振电路续流,可以改善逆变器输出电流波形的畸变率,减小了死区的不利影响.文中详细分析了电路的工作过程,在功率为4kW的单相实验样机上进行了实验验证,获得的实验结果表明在轻载和满载时逆变器的开关器件都能实现软开关,逆变器输出电流波形的畸变率都得到了改善.因此,该无源器件辅助换流的单相全桥软开关拓扑结构对于提高逆变器的性能具有重要意义.     

Phase compensation second-order repetitive control for CVCF PWM inverters

Phase compensation for high-order repetitive control (HORC) can improve system transient and steady-state performances. The phase compensator is often designed as the inverse transfer function of a closed-loop system. No other phase compensation methods for HORC have been reported up to now. Hence, in this paper, a simple approximate phase cancellation second-order repetitive control (RC) is proposed. The compensator is a linear combination of two different linear phase lead compensators, which can better fit the inverse of a plant model phase curve compared with the conventional linear phase compensator. Optimisation is introduced to design the parameters of the approximate phase cancellation second-order RC. Analysis and design of the second-order repetitive controlled pulse width modulation inverter system are presented. Simulations and experiments are provided to demonstrate the effectiveness of the optimisation method and verify the advantage of the approximate phase cancellation compensator.