三电平逆变器中点电位平衡的综合控制策略

三电平逆变电路普遍存在中点电位不平衡的问题,中点电位的不平衡主要体现在两个方面:中点电位偏移和中点电位波动。基于传统的SVPWM算法,通过分析造成中点电位不平衡的原因,提出了前馈控制+反馈控制的综合控制策略。该方法通过采集两个电容电压和三相负载电流的实时值,通过切换函数的不同值来选择不同的控制策略,从而实现对中点电位平衡的综合控制。仿真实验证明了此综合控制策略控制精度高,并且不会出现中点电位偏移的问题,很好地控制了中点电位的平衡,弥补了在只有反馈控制策略下电压波动幅值较大的缺点,达到了很好的效果。     

NPC型三电平逆变器SVPWM算法及中点电压平衡控制的研究

为解决二极管箝位型(NPc)三电平逆变器中点电压平衡问题,文中详细介绍了三电平逆变器空间矢量调制算法的基本原理,从空间矢量控制的角度分析了中点电压波动的基本规律,提出了一种有效抑制中点电压波动的算法。该算法依照中点电荷守恒原理,通过检测输出三相电流和中点电压波动值,推导出用于精确调节中点电压小矢量冗余开关状态的分配因子表达式。仿真结果验证了该方法的可行性和精确性。     

一种新型的三电平逆变器中点电压平衡控制策略

本文首先论述了三电平逆变器SVPWM的原理，利用最近三角形合成规则，推导了三角形定点矢量的作用时间。在此基础上，提出了一种通过判断中点电容电位而合理选择和分配小矢量的无电流传感器的中点电位控制方法，并作了具体阐述。理论分析和实验结果证明了此方法的有效性。     

基于改进SVPWM的三电平NPC逆变器中点电压平衡的研究

三电平NPC逆变器具有直流电压利用率高、开关耐压低、输出电压谐波低等优点而被应用于高压大功率场合。而中点电压平衡问题一直是三电平NPC逆变器研究的关键。文中在传统的空间矢量调制方法的基础上进行改进,不改变原来矢量的模长,对各扇区的不同小三角形内影响中点电位的中、小矢量进行重新分配和虚拟,理论上能完全消除电压矢量对中点电位的影响,该方法的中点电压平衡能力在全调制度范围内控制灵活且有效。通过仿真和实验验证了所提方法的正确性。     

三电平SVPWM逆变器中点电压平衡的研究

文章简要分析了中点钳位式三电平逆变器的基本原理，提出了一种平衡中点电位的新方法，并运用TMS320F2407实现了全数字化控制系统．最后通过仿真验证了该方案的正确性。     

三电平中点电位平衡控制研究

简要的介绍了三电平逆变器电压空间矢量法实现过程,重点考虑了三点平逆变器中点电位平衡控制问题,设计控制策略,解决中点电位的漂移问题,通过MATLAB／simulinkf仿真对结果做出分析。     

三电平逆变器多模式中点电压平衡策略

逆变器一直是电气领域研究的热点问题,三电平逆变器的广泛应用得到了研究人员的大量关注,其中三电平逆变器存在的中点电压不平衡的问题限制了其使用,该问题也渐渐成为近期的研究热点。本文提出了一种三电平逆变器多模式中点电压平衡策略和算法,较好地实现了中点电压平衡,通过仿真验证和实际工程应用,验证了该算法的可行性和可靠行。     

一种新型的三电平变频器中点电位平衡控制方法

中点电位不平衡问题一直是二极管箝位三电平逆变器固有的问题。本文提出了一种新的结构模式和中点电位控制算法。它用三电平整流器代替了传统的三相桥式不控整流装置，通过对三电平整流器的控制来解决三电平逆变器所产生的中点电位平衡问题，同时达到了提高功率因数和减少电网网侧谐波的效果。这将是一种应用前途非常广泛的模式。     

有源前端型三电平逆变器中点电位平衡的一种控制策略

由三电平有源前端(AFE)和三电平逆变器构成的中高压变频器在能量再生,功率因数,输入和输出谐波方面具有良好的性能.在这种变频器中,为了实现直流侧中点电位平衡控制(NPB),以往的方法都要对逆变控制采用的SVPWM算法进行调整,这不可避免地会增加逆变输出谐波.本文提出一种无需调整SVPWM算法而只在变频器前端解决NPB问题的策略,避免了逆变输出谐波的增加,使负载电机旋转磁场具有较为理想的圆度.文中介绍了这种NPB的基本原理,对在前端控制与在逆变侧控制的输入和输出性能进行了比较分析.仿真实验研究结果证明了该控制策略的正确性和有效性.     

三电平逆变器直接转矩控制仿真分析

对三电平逆变器直接转矩控制的基本原理,拓扑结构,控制原理,及控制策略进行了详细的分析,给出了一种结合三电平特性的异步电机数学模型,通过仿真验证了建立在该模型下的中点钳位式三电平逆变器直接转矩控制的良好动静态特性.     

Novel switching method for single-phase NPC three-level inverter with neutral-point voltage control

This paper proposes a novel switching method with the neutral-point voltage control in a single-phase neutral-point-clamped three-level inverter (SP-NPCI) used in photovoltaic systems. A proposed novel switching method for the SP-NPCI improves the efficiency. The main concept is to fix the switching state of one leg. As a result, the switching loss decreases and the total efficiency is improved. In addition, it enables the maximum power-point-tracking operation to be performed by applying the proposed neutral-point voltage control algorithm. This control is implemented by modifying the reference signal. Simulation and experimental results provide verification of the performance of a novel switching method with the neutral-point voltage control.     

On-line compensation of dead-time and inverter nonlinearity with disturbance voltage observer

This paper discusses and analyses a simple on-line compensation scheme for dead-time and inverter nonlinearity in the pulse width modulated (PWM) voltage source inverter (VSI). Dead-time effect and voltage drop in switching devices cause nonlinearity between reference and output voltage. In a conventional three-phase six-switch inverter, this nonideal condition adds extraneous harmonics that badly disturb voltage characteristics. In its turn, voltage disturbance causes distortion of the current waveform and degrades performance. In this paper, an on-line dead-time compensation method based on inverse dynamics control is proposed, and it is much simpler than conventional full/reduced order observation methods adopted in dead-time compensation. Disturbance voltages are observed on-line with no additional circuitry or off-line measurements. The observed disturbance voltages are fed back to the voltage reference for compensation. Stability problem of the proposed observer arisen from inverter delay and parameter mismatch was analysed. The proposed method is applied to a surface-mounted permanent-magnet synchronous motor (SPMSM) drive. The effectiveness of the proposed scheme is validated by the experimental results.     

Carrier-based modulation strategies for a neutral point clamped inverter

This article presents carrier-based modulation strategies for a neutral point clamped inverter that substantially reduces harmonics in the output line to line voltages, phase voltages, reference voltages and common mode voltage. A graphical technique that has already been proposed in the literature and that also allows various carrier disposition modulation strategies for a diode clamped inverter is being described here. For this graphical technique two new modulation strategies – alternative phase opposite disposition (APOD) and phase disposition (PD) – are being used to create reduced harmonics for diode-clamped inverters under both continuous and discontinuous switching conditions. These strategies can be further expanded in a very simple way. A comparison of conventional-, APOD- and PD-strategies will be given by simulation results by using the software ‘Simplorer’ and ‘Post Processor Day’. The common mode voltage has been reduced particularly with PD-strategy. The strategies have been confirmed using a three level inverter for medium voltage.     

GIS设备高压试验危险点分析及控制措施研究

为了更好地在电网运行中加强GIS设备高压试验,首先必须对试验流程进行分析,并对其危险点进行分析,并加强对其的控制,才能更好地确保高压试验质量,进而更好地促进其性能的发挥。     

浅议变电站PT二次回路中性点安装过电压保护的重要性

近年来,变电站设备因遭受雷击或输电线路雷电侵入波而导致绝缘损坏的事故时有发生,由于雷电冲击传递过电压将对二次绕组绝缘耐受电压造成很大的威胁,因此,在电压互感器二次回路中性点就地安装过电压保护措施具有重要的意义。本文对电压互感器二次中性点安装过电压保护的必要性进行分析研究。     

针对矿井配电网中性点电压偏移解决方法分析

本文结合电网的整体结构、中性点消弧补偿方式与中性点偏移的数学关系，进一步改进了消弧设备的感性电流注入方式，采取了一系列措施来抑制中性点电压的过大偏移情况。     

Direct model-based predictive control scheme without cost function for voltage source inverters with reduced common-mode voltage

This paper presents a direct model-based predictive control scheme for voltage source inverters (VSIs) with reduced common-mode voltages (CMVs). The developed method directly finds optimal vectors without using repetitive calculation of a cost function. To adjust output currents with the CMVs in the range of –V_dc/6 to +V_dc/6, the developed method uses voltage vectors, as finite control resources, excluding zero voltage vectors which produce the CMVs in the VSI within ±V_dc/2. In a model-based predictive control (MPC), not using zero voltage vectors increases the output current ripples and the current errors. To alleviate these problems, the developed method uses two non-zero voltage vectors in one sampling step. In addition, the voltage vectors scheduled to be used are directly selected at every sampling step once the developed method calculates the future reference voltage vector, saving the efforts of repeatedly calculating the cost function. And the two non-zero voltage vectors are optimally allocated to make the output current approach the reference current as close as possible. Thus, low CMV, rapid current-following capability and sufficient output current ripple performance are attained by the developed method. The results of a simulation and an experiment verify the effectiveness of the developed method.     

Robust speed control algorithm with disturbance observer for uncertain PMSM

This article suggests a robust cascade speed control algorithm for a permanent magnet synchronous motor (PMSM) combining the classical feedback linearising (FL) method and the disturbance observers (DOBs) without the integrators. The contributions of this method are twofold. The first one is to provide the simple DOBs for not only guaranteeing the closed-loop performance recovery property but also removing the steady-state errors without the integrators with respect to the tracking errors. The second one is to prove that the inner and outer loops are stabilised by the proposed cascade-type controller, simultaneously. The simulation and experimental results reveal that the proposed method maintains the speed tracking performance to be satisfactory for a wide operating region with the fixed control gain despite a plant-model mismatch where a 3-kW interior PMSM is utilised.