一种新的关于多电平变换器直流侧母线电容电压平衡的研究

本文在分析二极管箝位型逆变器直流侧母线电容电压不平衡原因的基础上,提出了一种采用滞环控制的辅助斩波电路。仿真结果表明,应用这种电路可以实现直流侧电容电压平衡,同时逆变器输出电压具有较好的谐波性能。     

二极管箝位型五电平逆变器电容电压平衡域的研究

本文分析了二极管箝位型多电平逆变器在全负载范围内的电容电压平衡问题。首先，在五电平逆变器数学模型的基础上，对电容电压平衡规律进行分析；然后详细研究了逆变器开关切换规则与PWM控制策略，进一步提出采用目标函数最优的方法对可行开关序列寻优，实现电容电压平衡控制。仿真分析得出了全负载范围内的电容电压平衡域曲线。结果表明，在高功率因数和大调制比下，电容电压很难达到动态平衡，五电平逆变器无法直接应用于全速度范围的中压交流调速领域。     

多电平逆变器主要控制策略综述

过出的十年中，多电平逆变器在中压大功率领域受到了广泛的关注。提出了各种各样的拓扑结构和控制策略，并广泛应用于各种场合。本文介绍了在多电平逆变器中重要的控制策略，包括载波调制、空间矢量、波形逼近和闭环调制等方法。     

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。     

电网电压不平衡时模块化多电平换流器控制策略研究

在电网电压不平衡状态下,负序电流的存在引起模块化多电平换流器(MMC)内部环流包括负序、零序和正序二倍频分量,导致传输有功功率、无功功率及直流侧电压二倍频波动,严重时会影响装置内外特性。为提高电能传输质量及确保换流器安全运行,研究MMC内外不平衡控制策略尤其关键。文中从传统方法、改进方法和创新方法三个方面分别介绍关于电网电压不平衡时MMC外特性和内特性不平衡控制策略的研究进展,并比较其优缺点;总结MMC不平衡控制策略及探讨其未来的研究方向。     

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。     

二极管箝位型多电平逆变器载波PWM控制方法的研究

在分析二极管箝位型多电平逆变器不同的载波PWM控制方法的基础,提出了一种新型的载波PWM方法。为了验证所提出的PWM方法，对二极管箝位型五电平逆变器进行了仿真研究。仿真结果表明，该方法在低调制度下具有良好的谐波特性，同时可以提高调制度，增加直流电压利用率。     

三电平逆变器中共模电压抑制方法的研究与仿真

文章对三电平逆变器输出中的共模电压进行了分析,为了减小共模电压带来的危害,文中采用了两种SPWM控制策略即传统三电平SPWM控制策略和降低共模电压的三电平SPWM控制策略。通过Matlab/Simulink仿真比较,结果表明两种策略都起到了抑制共模电压的作用,其中降低共模电压的三电平SPWM控制技术效果更为明显。     

有源箝位逆变器中点电压平衡控制研究

针对有源箝位三电平逆变器的特点,提出无差拍控制和新型载波调制方法,实现其电流快速跟踪控制和中点电位振荡抑制,而且,为了解决有源箝位三电平逆变器的开关损耗不均问题,提出一种载波输出方法,实现开关管损耗均衡控制,仿真和实验结果验证了提出新型无差拍控制和调制方法能够很好的跟踪给定电流、中点电位振荡和开关损耗均衡控制。     

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。     

模块化多电平换流器的技术研究综述

随着电力电子器件的发展,电压源换流器(VSC)广泛应用于高压直流输电领域。与传统的两电平或三电平VSC相比,模块化多电平换流器(MMC)具有电压等级控制灵活、谐波含量少、开关损耗低等特点,因此受到了科研工作者的广泛关注。本文从MMC的工作原理、调制策略以及电容电压均衡策略等方面综述了目前MMC的研究现状,并对其应用前景以及存在的问题作出了展望。     

Voltage Balancing Control of Diode-Clamped Multilevel Converters With Passive Front-Ends

In the previous literature, it has been reported that it is not possible to guarantee the balance of the dc-link capacitor voltages of multilevel three-phase diode-clamped dc–ac converters with passive front-ends for high modulation indices, especially for more than three levels. This paper proposes a novel closed-loop control approach capable of guaranteeing such balance for all operating conditions of the converters without the need for additional hardware. Three different phase duty-ratio perturbation schemes are proposed. They are compared through simulation for the case of a four-level three-phase diode-clamped dc–ac converter operated with a virtual-vector-based modulation. The most simple and effective perturbation scheme, only requiring the sensing of all dc-link capacitor voltages, is tested experimentally in the same four-level converter. The results demonstrate the feasibility of guaranteeing the dc-link capacitor voltage balance for all converter operating conditions.      

A Simple Voltage Balancing Scheme for m-Level Diode-Clamped Multilevel Converters Based on a Generalized Current Flow Model

This paper presents a simple voltage balancing scheme for m-level diode-clamped multilevel converters (DCMC). This paper first introduces a novel and simple current flow model for general $m$ -level DCMCs. The superiority of the proposed model is its independence from the modulation scheme and its simplicity. It also provides a new perspective for voltage sharing accessibility among the dc link capacitors. The proposed current flow model, a cost function, and a space vector modulation (SVM) switching strategy are then used to balance the capacitors' voltages of the DCMCs in a very simple and optimized manner. Such a voltage balancing scheme was not developed for converters of five levels or greater due to the complexity of the converter and its modeling approaches. To validate the feasibility of the proposed voltage balancing scheme, this paper presents analytical and simulation results obtained from a five-level DCMC. In particular, this paper introduces a stability region within which the voltage balancing strategy converges. The impact of the cost function on the stability margins and converter performance is examined and discussed by means of comparison with different cost functions, and it is shown that the proposed cost function will improve the stability margins. The performance of the strategy for unbalanced and polluted loads shows that, unexpectedly, in some specific cases output current harmonics will improve the stability margin.      

空间行波管用LCLC谐振变换器的研究

该文研究了LCLC谐振变换器在空间行波管放大器中的应用。基于电路分析的方法,研究了工作于零电压和零电流状态下的LCLC谐振电路的工作原理,并得到了各个工作模式的等效电路;基于该电路的工作原理,推导了该电路的参数;为验证分析的正确性,在PSIM仿真软件中对其进行仿真,并将仿真结果与计算结果进行了对比,仿真结果与分析结果高度一致;最后,设计了输入20 V,输出4600 V,开关频率200 kHz,输出功率280 W,效率高达93.38%的LCLC谐振变换器。仿真结果与实验结果都证实了分析的有效性。     

高压大功率变频器主电路拓扑和控制策略

本文对高压在功率变频器的拓朴结构和控制策略进行了分析的介绍，并给出了一些仿真和实验波形。     

并联型有源电力滤波器直流侧电压柔性控制策略

针对并联型有源电力滤波器的直流侧电压控制特点,提出了一种对直流侧电压进行柔性控制的并联型有源电力滤波器控制策略。该策略中,在直流侧电压控制部分引入反馈低通滤波器,削弱直流侧固有谐波对输出电流控制的影响;在电流控制的输出部分通过增加直流侧电压前馈系数,抵制在变换桥中可能引入的直流侧电压谐波影响。仿真结果表明直流侧电压柔性控制策略能够降低APF系统补偿后的电源电流总谐波畸变率,从而改善并联型有源电力滤波器的谐波补偿性能。     

An Improved Control Strategy of Limiting the DC-Link Voltage Fluctuation for a Doubly Fed Induction Wind Generator

The paper presents to develop a new control strategy of limiting the dc-link voltage fluctuation for a back-to-back pulsewidth modulation converter in a doubly fed induction generator (DFIG) for wind turbine systems. The reasons of dc-link voltage fluctuation are analyzed. An improved control strategy with the instantaneous rotor power feedback is proposed to limit the fluctuation range of the dc-link voltage. An experimental rig is set up to valid the proposed strategy, and the dynamic performances of the DFIG are compared with the traditional control method under a constant grid voltage. Furthermore, the capabilities of keeping the dc-link voltage stable are also compared in the ride-through control of DFIG during a three-phase grid fault, by using a developed 2 MW DFIG wind power system model. Both the experimental and simulation results have shown that the proposed control strategy is more effective, and the fluctuation of the dc-link voltage may be successfully limited in a small range under a constant grid voltage and a non-serious grid voltage dip.     

A Modular Strategy for Control and Voltage Balancing of Cascaded H-Bridge Rectifiers

In this paper, a new strategy for voltage balancing of distinct dc buses in cascaded H-bridge rectifiers is presented. This method ensures that the dc bus capacitor voltages converge to the reference value, even when the loads attached to them are extracting different amounts of power. The proposed method can be used for an arbitrary number of series H-bridges, different voltage levels, and different power levels in unidirectional or bidirectional rectifiers. To reduce the current harmonics and distortion, the input current is programmed to be sinusoidal and in phase with the input voltage; however, it is possible to adjust the input power factor to control both the active and reactive powers. In the proposed approach, both the low frequency (stepped modulation) and high frequency [pulse-width modulation (PWM)] switching methods are utilized to improve the performance of the rectifier. Using theoretical analysis, the acceptable load power limits for a rectifier with N-H-bridge cells are derived. The validity of the proposed method is verified by simulation and experimental results.      

双PWM型变流器协同控制策略仿真研究

为了抑制直流母线电压波动,提高交-直-交变流器的动态性能,需对其采用协调控制策略。本文对现有协调控制策略进行了总结,从功率平衡的角度,研究了交-直-交变流器的静态与动态模型。并在分析异步电动机动态模型的基础上,进行了交-直-交协调控制策略的仿真分析,仿真结果表明,这种控制算法具有直流母线响应速度更快、波动小等特点。