新型近似无死区PWM逆变器开关控制方法及其特性分析

针对逆变器的死区补偿问题,研究了一种无电流传感器近似无死区逆变器开关控制方法.与传统逆变器死区补偿方法相比,该方法只需在逆变器输出电流正负跳变时加入固定的死区脉冲,大幅减少了死区脉冲个数,从而减小死区的影响.为了减小系统成本,采用简单的模拟电路来判别逆变器输出电流正负跳变时刻.深入分析了死区补偿方法的基波和低次谐波特性...     

Research on Control of Dead-Time Effect on Grid-Connected Inverter

通过分析逆变器的死区效应和电感输出电流正、负半周期时逆变器同桥臂上、下开关管的工作特点,得出仅在输出电流过零换向阶段加入死区,其他时间通过判断电流方向以封锁相应桥臂触发脉冲的无死区处理办法,使得死区效应导致的误差脉冲仅存在于电流过零附近,有效降低死区效应的影响.通过仿真验证了该理论分析方法的可行性和有效性.     

电磁搅拌电源死区补偿系统设计与实现

电磁搅拌电源输出低失真电流波形是电磁搅拌器负载产生标准的旋转磁场并能长期可靠运行的重要保证. 电磁搅拌专用电压型逆变器由于死区的存在不可避免地会对输出电流波形造成影响.针对电磁搅拌专用电压型逆变器 死区的影响,对电压逆变器所必需的死区时间和其特性效应进行了分析.根据死区效应分析,结合电磁搅拌负载系统 自身属重感性负载,设计了一种实时调整每个载波周期中的实际IGBT导通时间的补偿方法,达到消除死区效应影响 的目的,并且通过试验验证了所采用方法可以有效改善输出电流的波形畸变,降低输入至电磁搅拌器负载中电流的谐 波含量.     

IGBT的死区补偿方法研究

对三相桥式逆变器死区效应进行了理论分析.阐述了死区效应对逆变器输出电压的影响.介绍了加入一种死区时间的方法,在此基础上提出了一种基于SVPWM控制的逆变器死区补偿方法,即对称补偿法.该方法有效地改善了死区效应引起的电流畸变,实验结果证明了理论分析的正确性和该方法的可行性和有效性,并成功用于变频器的设计中.     

死区对电压型逆变器输出误差的影响及其补偿

针对电压型逆变器的死区效应,分析了死区对逆变器输出电压谐波和电流的影响,提出一种基于功率导通时间实时检测的死区补偿和电机相电压检测方法.为避免电流过零点的直接检测或间接预估,设计硬件电路直接检测功率管的导通时间,得到逆变器的实际死区时间,并在软件中进行补偿,同时得到电机实际的相电压.采用该方法得到的死区时间反映了开关器件导通和关断时间受结温和导通电流影响的特性,最后对上述方法进行了实验验证.     

一种低成本逆变器死区时间补偿方法

逆变器的开关死区时间是引起逆变器非线性的主要原因,逆变器的非线性会对电流控制产生不利影响,使准确的矢量转矩控制无法实现.死区补偿方法通常需要以电流检测作为基准,为降低成本及系统的复杂性,以利于死区补偿在通用变频器中的应用,研究出了一种低成本且简便易行的死区补偿方法.     

近似无死区逆变器开关控制及特性分析

针对逆变器的死区补偿问题,研究了一种无电流传感器近似无死区逆变器开关控制方法。与传统逆变器死区补偿方法相比,该方法只需在逆变器输出电流正负跳变时加入固定的死区脉冲,减小了死区脉冲个数,从而减小死区的影响。分析了本文研究的死区补偿方法的基波和低次谐波特性,指出减小死区时间可消弱死区及低次谐波对逆变器输出电压的影响。仿真及实验结果不仅验证了本文研究内容的有效性,而且还表明该死区处理方法可适用于单次频率域和谐波域。     

串联谐振逆变器死区对浪涌电压电流的影响

就逆变器死区对浪涌电压\电流的影响进行了深入的研究,分别在不同的死区宽度下,用PSPICE进行仿真分析,得出了死区选择的参数范围,过小或过大的死区时间都会产生非常高的浪涌电压电流,从而对逆变器的性能造成一定的影响。     

基于FFT的三电平逆变器的死区补偿策略

针对死区所带来的三电平逆变器输出电压和输出电流的畸变,通过分析死区效应的机理,对死区时间、功率器件的电压降、开通和关断时间如何影响三电平逆变器的输出电压进行了详细地论述,据此提出了一种基于快速傅里叶变换(FFT)的三电平逆变器的死区补偿策略,该策略利用FFT对电流进行滤波以准确判断电流的极性,进而补偿死区。最后,基于三电平逆变器进行仿真验证,结果表明,所提出的采用FFT的死区补偿策略能够有效减小死区效应造成的电流畸变,改善零电流钳位现象。     

基于卡尔曼滤波器的PMSM逆变器死区效应补偿方法

分析了死区效应及其对PMSM逆变器工作状况的影响,提出了一种基于卡尔曼滤波器的死区效应补偿方法.该方法通过对系统电流在α、β静坐标系进行系统噪声、量测噪声滤波,从而得到系统的三相电流方向,进而得到死区导致的误差电压矢量,根据误差电压矢量对电压输出进行补偿,实现对死区效应的有效抑制.实验结果表明,该方法可有效改善逆变器输出电流波形,提高PMSM系统的工作性能.     

逆变器驱动感应电机系统中的电机轴承电流

逆变器输出的高频PWM电压作用在电机绕组上,在电机内部产生共模耦合效应,形成共模耦合电流,其中流过电机轴承的共模耦合电流会造成电机轴承的损坏。分析了电机内部的共模耦合效应和轴承电流产生的机理,讨论不同情况下轴承电流表现的不同特性以及轴承电流的测量方法,为轴承电流的深入研究打下基础。     

西北电网短路电流的限制措施

介绍了电力系统短路电流产生的原因和危害以及国内外在电力系统短路电流限制技术方面的研究状况，结合西北750 kV电网的建设和发展，分析了西北电网在750 kV发展过程中短路电流增加的原因和趋势，并对限制短路电流的多种措施进行了探讨：包括实现电网分层分区运行；加装中性点电抗；实现母线分段运行；采用高阻抗变压器等。针对不同的网架情况，提出了相应的对策和建议。     

SLG Fault Detection in Presence of Strong Capacitive Currents in Compensated Networks

The detection of a single line-to-ground fault in compensated distribution networks can be hampered by important capacitive currents. The way to deal with this problem depends on the particular regime where data are acquired. In the transient regime, the relays diagnosis based on the analysis of charging components can deceive with a massive presence of discharging currents. The latter, however, will disclose data for directional function if the sampling frequency is high enough for acquisition in the wave propagation area. The fault detection can also be out of reach of steady-state methods which are based on the detection of active components in faulty currents. The efficiency of these methods vanishes when strong capacitive currents squeeze the phase shift between faulty and sound zero-sequence currents below the actual acquisition limits. In such a situation, however, it is still possible to obtain the faulty feeder indication from the way the residual currents cross the zero level soon after inception.     

特高压交流变电站母线短路电流的影响因素分析

从特高压交流变电站高、中压侧母线等值自阻抗的组成要素出发,分析确定了特高压变电站母线短路电流的影响因素,给定了特高压变电站1 000 kV侧交流电网结构、特高压交流变电站主变压器以及500 kV侧交流电网结构对高压侧和中压侧母线短路电流影响的比重关系。分析结果表明,特高压交流变电站高压侧母线的短路电流主要受1 000 kV侧交流电网结构的影响,而中压侧母线短路电流主要受500 kV侧电网结构和特高压站主变压器的影响。研究结论可为特高压交流站近区电网限流措施的优化提供理论支撑。     

Grid synchronization and control of distributed generation unit with flexible load compensation capabilities using multi-output LMS-filter

This paper deals with grid synchronization and control of single-phase voltage source inverter in distributed generation (DG) systems using a multi-output adaptive filter. Besides the active power injection, the proposed control enables the inverter to compensate load harmonic and reactive currents based on the capacity of inverter. The currents to be compensated are obtained using a multi-output adaptive filter structure that operates on the principle of variable step size (VSS) least mean squares (LMS) algorithm. The main objective of VSS-LMS filter is to decompose the load current into harmonic and reactive current components and compute their RMS values. The currents extracted by the VSS-LMS filter are used in developing a flexible compensation based on load compensation factors. The load compensation factors are calculated based on the remaining capacity of the inverter and priority. Harmonic currents compensation is given first priority over the reactive currents. In addition to harmonic currents detection, the same VSS-LMS filter is used in developing a phase locked loop unit for synchronizing the inverter with fundamental point of common coupling (PCC) voltage. Synchronizing the DG inverter with fundamental PCC voltage would make the proposed control algorithm insensitive to grid voltage harmonics and frequency fluctuations. The feasibility and the efficacy of the proposed control algorithm are demonstrated using hardware-in-the-loop (HIL) based experiments.     

1 000 kV同塔双回线路不平衡度及换位方式分析

对1 000 kV淮南－皖南同塔双回线路参数、母线电压和发电机电流的不平衡度进行了分析,研究中考虑了2种常用的换位方式,对不同换位方式下的潜供电流和恢复电压、感应电压和感应电流进行了比较。结果表明,从降低母线电压和发电机电流不平衡度的角度来看,采用换位方式2较好;从减少潜供电流和感应电压的角度来看,采用换位方式1更佳。在满足国标要求的前提下,为了限制线路的潜供电流、感应电压和感应电流,推荐淮皖线采用换位方式1。     

Reduction of common-mode currents in PWM inverter motor drives

Modern pulsewidth modulation (PWM) inverter motor drives are affected by dangerous common-mode currents due to the high rate of variation of the modulated voltage. An inexpensive alternative to low-pass filters, which are normally used to limit common-mode currents, consists in reducing such currents by using suitable modulation strategies. In this paper, a new approach for designing PWM strategies is presented, which is able to reduce common-mode currents by limiting the amount of variations of the common-mode voltage. The main characteristics of the proposed approach are experimentally evaluated on a standard PWM induction motor drive     

平行双回线电流平衡保护的仿真研究

平行双回线路电流平衡保护具有不需要通道、不需要PT输入的优点。文章提出了适用于高压平行双回线的电流平衡保护方案，首先仿真分析了基于全量、故障分量、零序分量的电流平衡保护的优缺点，在此基础上提出了利用全量电流和零序电流构成综合启动判据、由故障分量构成选线判据的电流平衡保护方案，该方案较基于全量的电流平衡保护灵敏度高、相继动作区小，而且具有选相功能。     

Modeling and simulation of transmission system shield wires under unbalanced conditions

The purpose of this investigation is to calculate the ground return current under steady-state or transient conditions, given the phase currents in the conductors of two unbalanced three-phase parallel circuits. Thus, the shield wires can be modeled to carry appropriate current depending upon the currents in the three phase conductors. For example, when a fault occurs on a phase conductor, the currents that start flowing in the phase conductors may become unbalanced. Under such conditions, the currents that are coupled into the shield wires will be more important. This investigation can help a transmission system line designer to identify the appropriate shield wires under different transmission system scenarios. A computer package that evaluates the shield wire currents under unbalanced conditions when the transmission lines are randomly spaced is developed.     

由SVPWM逆变器直流电流获取三相输出电流的方法研究

文章阐述了利用三相逆变器的直流电流构造三相输出电流的方法，并针对死区时间对电流构造的影响进行了详细分析，最后给出了利用2种解决办法所得的电流构造效果。