Modified Phase-Shifted PWM Control for Flying Capacitor Multilevel Converters

The issue of voltage imbalance remains a challenge for the flying capacitor multilevel converter. The phase-shifted pulsewidth modulation (PS-PWM) method has a certain degree of self-balancing properties. However, the method alone is not sufficient to maintain balanced capacitor voltages in practical applications. The paper proposes a closed-loop modified PS-PWM control method by incorporating a novel balancing algorithm. The algorithm takes advantage of switching redundancies to adjust the switching times of selected switching states and thus maintaining the capacitor voltages balanced without adversely affecting the system's performance. Key techniques of the proposed control method, including selection of switching states, calculation of adjusting times for the selected states, and determination of new switching instants of the modified PS-PWM are described and analyzed. Simulation and experimental results are presented to confirm the feasibility of the proposed method     

Capacitor voltage balancing in full binary combination schema flying capacitor multilevel inverters

Recently, the full binary combination schema (FBCS) method has been introduced to control the flying capacitor multilevel inverter. This method has the primary advantage that the number of voltage levels can be increased for a given number of semiconductor devices when compared to the conventional control methods. However, due to the difficulty of balancing the capacitors, the new schema requires fixed floating sources to provide the DC voltages. This paper reveals an approach of balancing the capacitors, thus expanding the application fields of FBCS inverters to the family of the flying capacitor multilevel inverters under the condition of choosing a suitable modulation index. Simulation results demonstrate the proposed voltage balancing control.     

基于预测控制的三相双降压逆变器统一调制策略

针对三相双降压逆变器(Dual Buck Inverter,DBI)这种无需死区时间、开关频率较高、输出高功率因数的变换器调制策略较多的问题,将现有的3种不同的调制策略进行结合,引入预测控制方法,提出统一的调制策略。所提方法能够在同一种控制方法下切换正弦脉宽调制策略(SPWM),空间矢量脉宽调制策略(SVPWM)和不连续空间矢量脉宽调制策略(DSVPWM)3种不同的调制方法,实现控制方法的简化。通过仿真与实验验证了3种调制方法之间的切换,同时对比了3种不同调制方法下的逆变器传输效率。     

基于MATLAB的司接式矩阵变换器的调制策略仿真研究

作为一种新型矩阵变换器,间接矩阵变换器除了保留了传统矩阵变换器具有的无大体积储雏电容、输入输出电流为正弦波、可实现单位输入功率因数、能量可双向流动等优点外,还具有相对独立的整流侧和逆变侧,通过使用相对成熟的整流和逆变控制策略分别对其整流侧和逆变侧进行调制．仿真结果证实该控制策略设计可靠,控制过程得以简化,控制效果良好．给实际研究和设计提供方便。     

Three-Level Inverter Scheme With Common Mode Voltage Elimination and DC Link Capacitor Voltage Balancing for an Open-End Winding Induction Motor Drive

A dc link capacitor voltage balancing scheme along with common mode voltage elimination is proposed for an induction motor drive, with open-end winding structure. The motor is fed from both the ends with three-level inverters generating a five level output voltage space phasor structure. If switching combinations, with zero common mode voltage in the pole voltage, are used, then the resultant voltage space vector combinations are equivalent to that of a three-level inverter. The proposed inverter vector locations exhibit greater multiplicity in the inverter switching combinations which is suitably exploited to arrive at a capacitor voltage balancing scheme. This allows the use of a single dc link power supply for the combined inverter structure. The simultaneous task of common mode voltage elimination with dc link capacitor voltage balancing, using only the switching state redundancies, is experimentally verified on a 1.5-kW induction motor drive     

H桥级联多电平逆变器相移SVPWM技术的研究

载波相移SPWM调制法是级联型逆变器的主流控制方法,其等效载波频率高、谐波特性好、功率单元之间输出功率平衡。而空间矢量法谐波特性好、电压利用率高、控制方法简单便于数字实现。文中针对H桥级联型多电平逆变器的结构特点,综合采用载波移相SPWM法和空间矢量法,并用一种新的空间矢量算法取代传统的方法。该算法中无需三角函数和无理数计算,计算过程非常简单,节约了计算时间,结果更为准确。最后通过系统仿真验证该算法的正确性和有效性。     

Optimized space vector switching sequences for multilevel inverters

Previous work has shown that space vector modulation and carrier modulation for two-level inverters achieve the same phase leg switching sequences when appropriate zero sequence offsets are added to the reference waveforms for carrier modulation. This paper presents a similar equivalence between the phase disposition (PD) carrier and space vector modulation strategies applied to diode clamped, cascaded N-level or hybrid multilevel inverters. By analysis of the time integral trajectory of the converter voltage, the paper shows that the optimal harmonic profile for a space vector modulator occurs when the two middle space vectors are centered in each switching cycle. The required zero sequence offset to achieve this centring for an equivalent carrier based modulator is then determined. The results can be applied to any multilevel converter topology without differentiation. Discontinuous behavior is also examined, with the space vector and carrier based modulation methods shown to similarly produce identical performance. Both simulation and experimental results are presented.     

Switching Characterization of Cascaded Multilevel-Inverter-Controlled Systems

In this paper, the method of triangular carrier switching control of two-level inverters is extended to cascaded multilevel inverters using phase-shifted multicarrier unipolar pulsewidth modulation (PWM). The condition for smooth modulation is obtained using the Bessel's function representation of the PWM output and the switching condition of the multilevel-inverter-controlled system. A method is proposed for the determination of the minimum amplitude of the triangular carrier for smooth modulation at fixed switching frequency. It is shown that the multilevel modulation based on the phase-shifted carriers significantly reduces the ripple magnitude in the switching function and allows the use of a smaller carrier amplitude under closed loop. This increases the forward gain and, hence, improves the tracking characteristics. The proposed cascaded multilevel inverter control is implemented for the operation of a distribution static compensator (DSTATCOM) in the voltage control mode. The experimental verification of the theoretical and simulation results is provided through a field-programmable gate array (FPGA) based control of a laboratory model of a single-phase DSTATCOM.     

A Predictive Control With Flying Capacitor Balancing of a Multicell Active Power Filter

Unlike traditional inverters, multicell inverters have the following advantages: lower switching frequency, high number of output levels, and less voltage constraints on the insulated-gate bipolar transistors. Significant performances are provided with this structure which is constituted with flying capacitors. This paper deals with a predictive and direct control applied to the multicell inverter for an original application of this converter: a three-phase active filter. To take advantage of the capabilities of the multicell converter in terms of redundant control states, a voltage control method of flying capacitor is added, based on the use of a switching table. Flying capacitor voltages are kept on a fixed interval, and precise voltage sensors are not necessary. The association of predictive control and voltage balancing increases considerably the bandwidth of the active filter.      

基于开关函数法的SVPWM实现技术

基于电压空间矢量PWM（SVPWM）与正弦波PWM（SPWM）等效原理,建立了逆变器控制用的SVPWM的开关函数矩阵,并利用该开关函数矩阵具体实现了这种SVPWM的全数字控制,且很好地运用到工业变频器的产品开发中,最后给出了有关实验结果和波形。     

基于TMS320LF2407的三相应急电源

逆变控制技术直接影响三相应急电源（EPS）输出波形的质量和整机效率。文中采SVPWM算法和数字控制技术,与传统SPWM算法相比,提高了EPS输出波形的质量和输出电能的效率;波形控制中采用电压瞬时值内环、平均值外环的双环控制,降低了波形畸变率,使正弦波电压输出更稳定。     

一种优化三电平逆变器的SVPWM算法的研究

针对传统SVPWM算法计算复杂的缺点,提出一种基于60°坐标下三电平逆变器SVPWM调制算法的控制策略。该控制策略可大幅简化传统SVPWM算法参考矢量扇区判定及开关矢量作用时间的运算,通过在g-h非正交坐标系内对大小扇区规则判断、基本矢量作用时间计算和作用顺序方法进行了研究,减小了控制器的计算工作量。采用Matlab/Simulink仿真软件对该控制策略进行了仿真,仿真结果验证了该控制策略的正确性及有效性。     

基于SVPWM调制抽油机能量回馈装置设计

传统抽油机能耗制动将其下冲过程中的能量以热量的形式散发掉,这样既不安全亦不经济。通过能量回馈装置将这部分能量回馈至电网,对于油田的节能降耗具有重要的意义。论文基于SVPWM调制构建了能量回馈装置,结果表明能量回馈装置的输出电压波形接近正弦波,三次谐波含量为3.91%,可满足实际应用的相关要求。SVPWM调制方式相比SPWM调制明显的提高直流电压的利用率,具有良好的应用前景。     

New zero voltage switching DC converter with flying capacitors

A new soft switching converter is presented for medium power applications. Two full-bridge converters are connected in series at high voltage side in order to limit the voltage stress of power switches at V_in/2. Therefore, power metal–oxide–semiconductor field-effect transistors (MOSFETs) with 600 V voltage rating can be adopted for 1200 V input voltage applications. In order to balance two input split capacitor voltages in every switching cycle, two flying capacitors are connected on the AC side of two full-bridge converters. Phase-shift pulse-width modulation (PS-PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active MOSFETs can be turned on under zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. Two full-bridge converters are used in the proposed circuit to share load current and reduce the current stress of passive and active components. The circuit analysis and design example of the prototype circuit are provided in detail and the performance of the proposed converter is verified by the experiments.     

基于Saber的SVPWM逆变器控制仿真

为了对航空航天飞机供电系统的变频系统的逆变部分做仿真,采用了空间矢量PWM（SVPWM）控制策略,使变频后输出的电流在正弦波附近变化。SVPWM是依据变流器空间电压（电流）矢量切换来控制变流器的一种控制策略。在仿真软件Saber环境下运用MAST语言根据SVPWM的控制算法建立了SVPWM的逆变模型的实验,得到了与理论分析符合的仿真实验结果。     

Multilevel inverters: a survey of topologies, controls, and applications

Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.     

基于虚坐标系的三电平逆变器SVPWH算法的研究

对于中点箝位三电平逆变器,传统的空间矢量脉宽调制方法需要进行大量的三角函数运算及扇区判定,增大了控制器的计算工作量。为解决这一问题,该文研究一种基于虚坐标系的空间矢量脉宽调制方法。该方法主要包括两个部分：一是根据参考矢量计算合成基本矢量的作用时间：二是根据控制策略对零序分量进行控制选择合适的开关状态。通过对零序分量的选择实现了对中点电位平衡的控制,最后matIab／SimuIink仿真验证给出了实验结果,证明了控制方法的正确性。     

基于TMS320F240的三电平逆变器SVPWM实现

在两电平的常规空间矢量PWM算法的基础上，给出了三电平空间矢量PWM算法，并提出一种改进的三电平空间矢量PWM调制策略来进行二极管钳位型三电平逆变器的控制，从而实现最小开关损耗。基于TMS320F240 USP实现了三电平逆变系统的数字控制，实验结果论证了该方案的可行性。     

电压空间矢量脉宽调制原理及其在DSP上的实现

介绍了电压空间矢量脉宽调制技术（SVPWM）的基本工作原理,给出了求解相关参数的公式.介绍了TMS320F2812DSP事件管理器的硬件结构,利用事件管理器可以很方便地产生SVPWM波形,减少了DSP运算单元CPU的工作量并给出了由事件管理器产生SVPWM的流程图.最后给出了实验结果,分析了此种方案的优缺点.     

三相电压源整流器最小开关损耗调制算法的研究(上)

三相全桥PWM电压源整流器(VSR)是一种优质的升压型四象限AC·DC变换器,能够输出稳定的直流电压和获得可调的输入电流位移因数。在许多应用领域中.对三相电压源整流器的整体效率要求日益提高。考虑到三相电压源整流器的开关损耗与调制算法密切相关.为此需要改进已有的调制算法.本文在理论上推导了电压源整流器多解性原理基础上.分析了传统SPWM和SVPWM算法的本质联系.提出了一种在三相电压源整流器目标函数中注入零序分量的最小开关损耗SPWM和SVPWM调制算法.并推导了功率器件的功耗计算公式。在利用MATLAB/SIMULINK对采用最小开关损耗SPWM和SVPWM调制算法的整流器进行仿真分析之后,采用DSP F28335实现了最小开关损耗PWM调制算法的电压源整流器实验平台.验证了有关结论。相比传统的SPWM和SVPWM调制算法.最小开关损耗PWM算法能够将整流电路提升效率2~3%