Multilevel Multiphase Space Vector PWM Algorithm

In the last few years, interest in multiphase converter technology has increased due to the benefits of using more than three phases in drive applications. Besides, multilevel converter technology permits the achievement of high power ratings with voltage limited devices. Multilevel multiphase technology combines the benefits of both technologies, but new modulation techniques must be developed in order to take advantage of multilevel multiphase converters. In this paper, a novel space vector pulsewidth modulation (SVPWM) algorithm for multilevel multiphase voltage source converters is presented. This algorithm is the result of the two main contributions of this paper: the demonstration that a multilevel multiphase modulator can be realized from a two-level multiphase modulator, and the development of a new two-level multiphase SVPWM algorithm. The multiphase SVPWM algorithm presented in this paper can be applied to most multilevel topologies; it has low computational complexity and it is suitable for hardware implementations. Finally, the algorithm was implemented in a low-cost field-programmable gate array and it was tested in a laboratory with a real prototype using a five-level five-phase inverter.     

多电平逆变器通用简化空间矢量调制法

空间矢量调制法在多电平逆变器中已得到广泛使用,然而传统SVPWM算法需要扇区判断和繁琐的三角函数运算,且所有的基本电压矢量必须预先计算并储存起来供后续运算调用,这样既增加了控制器的计算量,影响响应速度,又占用了一定的存储空间。此外,随着电平数的增加,算法会越来越复杂。为此,提出了一种通用的简化空间矢量调制法,在定位了参考电压矢量后,基于两个表格进行简单的逻辑运算即可得到所需的开关状态和开关顺序,且该算法适用于更高电平的逆变器。最后,搭建了三电平NPC逆变器和五电平NPC/H桥逆变器的MATLAB仿真模型,并对三电平NPC逆变器做了实验研究,仿真和实验结果验证了该算法的有效性和通用性。     

A Space Vector PWM Scheme for Multilevel lnverters Based on Two-Level Space Vector PWM

1. INTRODUCTION MULTILEVEL inverters are increasingly being used in high-power medium voltage applications due to their superior performance compared to two-level inverters, such as lower common-mode voltage, lower dv/dt, lower harmonics in output voltage and current, and reduced voltage on the power switches.     

Multilevel Multiphase Space Vector PWM Algorithm With Switching State Redundancy

Multilevel multiphase technology combines the benefits of multilevel converters and multiphase machines. Nevertheless, new modulation techniques must be developed to take advantage of multilevel multiphase converters. In this paper, a new space vector pulsewidth modulation algorithm for multilevel multiphase voltage source converters with switching state redundancy is introduced. As in three-phase converters, the switching state redundancy permits to achieve different goals like extending the modulation index and reducing the number of switchings. This new algorithm can be applied to the most usual multilevel topologies; it has low computational complexity, and it is suitable for hardware implementations. Finally, the algorithm was implemented in a field-programmable gate array, and it was tested by using a five-level five-phase inverter feeding a motor.      

A Space Vector Modulation Scheme to Reduce Common Mode Voltage for Cascaded Multilevel Inverters

Multilevel inverters can reduce the common mode voltage generated. Schemes have been reported for multilevel inverters that reduce the common mode voltage. However, most of the schemes result in reduced modulation depth, high switching losses, and high harmonic distortion. This paper proposes a space-vector modulation scheme to reduce common mode voltage for cascaded multilevel inverters. The proposed scheme can increase the voltage range of operation by about 17% and can produce lower total harmonic distortion than the previously proposed schemes. The scheme is explained for five-level inverter. The scheme can be easily extended to a n-level inverter. Both experimental and simulation results are provided.     

A Space Vector PWM Scheme for Multifrequency Output Voltage Generation With Multiphase Voltage-Source Inverters

Multiphase variable-speed drives, supplied from two-level voltage-source inverters (VSIs), are nowadays considered for various industrial applications. Depending on the drive structure and/or the motor design, the VSI is required to generate either sinusoidal voltages or voltages that contain a certain number of sinusoidal components (ldquomultifrequency output voltagesrdquo). The existing space vector pulsewidth-modulation (SVPWM) schemes are based on selection of (n-1) active space vectors (for odd phase numbers) within a switching period and they yield either sinusoidal voltage or sinusoidal fundamental voltage in combination with a limited amount of other harmonic terms. This paper develops a SVPWM scheme, which enables multifrequency output voltage generation with arbitrary values of various sinusoidal components in the output voltage. The method is based on initial selection of (n-1)²/2 active space vectors within a switching period, instead of the common (n-1) active vectors. By properly arranging the sequence of the vector application, it is possible to provide an automatic postreduction of the number of applied active vectors to (n-1), thus maintaining the same switching frequency as with the existing schemes while simultaneously avoiding the limiting on the generated sinusoidal output voltage components. Theoretical considerations are detailed using a five-phase VSI. The experimental verification is provided using a five-phase two-motor series-connected induction motor drive, supplied from a custom-designed five-phase DSP-controlled VSI.     

A General PWM Strategy for Four-Switch Three-Phase Inverters

A general pulsewidth modulation (PWM) method for control of four-switch three-phase inverters is presented. The proposed vector PWM offers a simple method to select three or four vectors that effectively synthesize the desired output voltage, even in presence of voltage oscillations across the two dc-link capacitors. The method utilizes the so called space vector modulation, and includes its scalar version. Different vector combinations are compared. The effect of Wye and delta motor winding connections over the pulse width modulator is also considered. The common mode voltage generated by the four-switch three-phase converter is evaluated and compared to that provided by the standard six-switch three-phase inverter. Simulation and experimental results are presented to demonstrate the feasibility of the proposed approach     

Multicarrier PWM With DC-Link Ripple Feedforward Compensation for Multilevel Inverters

Like most power converter topologies, multilevel inverters are controlled with modulation techniques that are conceptually based on nonlinear waveform synthesis assuming constant dc-link voltages. However, real applications have load and supply dependent dc-links that usually present important low frequency ripple, which is also modulated and transmitted to the load, generating undesirable low frequency voltage and current distortion. This paper introduces a simple but effective dc-link ripple feedforward strategy into traditional carrier-based modulation techniques. The dc-link ripples are measured and used to modify the carriers or the reference directly in the modulation stage. Simulation and experimental results show the accuracy of the proposed method, eliminating low order harmonics in the load current.     

Phase-Shifted Carrier PWM Technique for General Cascaded Inverters

Phase-shifted carrier (PSC) pulsewidth modulation (PWM) in its conventional form is a good solution for single-phase Cascaded inverters as alternative phase opposition disposition (APOD) PWM for single-phase diode clamped inverters. PSC distributes the switching angles of APOD PWM waveform among the legs uniformly and reduces the switching frequency of each leg. This paper proposes a modified PSC technique based on partly shifted carriers for all disposition types including phase disposition (PD) which is suitable for three-phase cascaded inverters. Simulation results are also included for using carrier-based space-vector PWM (SVPWM).     

n电平空间矢量算法的优化及其硬件实现

 本文提出了一种适合硬件实现的多电平空间矢量调制算法,该算法利用空间矢量图的几何对称性来实现算法优化.多电平空间矢量图可以划分为几何形状完全一致的六大扇区,优化算法通过扇区之间的对应关系把矢量调制算法的计算集中在一个扇区内完成.与传统的空间矢量算法相比,计算量减少为原来的1/6,更适合用硬件实现.为了设计出的硬件电路具有通用性,本文给出了具体设计过程.最后,文章以两电平和三电平IP(Intellectual Property)核的设计为实例验证了优化算法的正确性和有效性.     

Space Vector Modulation for Two-Level Unidirectional PWM Rectifiers

This paper presents the concepts for application of space vector modulation to two-level unidirectional pulsewidth modulation (PWM) rectifiers, and a methodology for the use of this modulation is proposed and applied in three different groups of rectifiers. For each group of rectifiers, the converter switching stages are analyzed to determine switch control signals for space vector modulation. One switching sequence is proposed for all rectifiers in order to minimize the number of switch commutations and reduce the switching losses. Duty cycle functions are determined, and the desired switching sequences are performed by a simple PWM, without the need to determine the present sector of the vector. For this purpose, it is necessary to impose the desired current sectors from input voltage references only. In order to validate the proposed modulation techniques, simulation and experimental results are presented for a 20-kW prototype.      

Space Vector Based Hybrid PWM Techniques for Reduced Current Ripple

This paper investigates certain novel switching sequences involving division of active vector time for space vector based pulsewidth modulation (PWM) generation for a voltage source inverter. This paper proposes two new sequences, and identifies all possible sequences, which result in the same average switching frequency as conventional space vector PWM (CSVPWM) at a given sampling frequency. This paper brings out a method for designing hybrid PWM techniques involving multiple sequences to reduce line current ripple. The three proposed hybrid PWM techniques (three-zone PWM, five-zone PWM and seven zone PWM) employ three, five and seven different sequences, respectively, in every sector. Each sequence is employed in a spatial region within the sector where it results in the lowest rms current ripple over the given sampling period. The proposed techniques lead to a significant reduction in THD over CSVPWM at high line voltages. The five-zone technique results in the lowest THD among real-time techniques with uniform sampling, while the seven-zone technique is the best among real-time techniques with twin sampling rates. The superior harmonic performance of the proposed techniques over CSVPWM and existing bus-clamping PWM techniques is established theoretically as well as experimentally.     

A Novel Three-Phase Reference Sine-Wave Generator for PWM Inverters

A hybrid circuit for producing a three-phase reference sine wave required with PWM inverters is described in this paper. The principle of the circuit is simple and the implementation of the circuit is easy. The circuit has all the features discussed in the literature. The unit built has, apart from the three-phase sine waves, balanced three-phase square and triangular waves. A high-frequency triangular wave already available in the circuit can be used for the PWM control circuitry. The scheme can easily be extended to generate sine waves of any number of phases.     

逆变器的空间电压矢量控制及DSP设计

介绍了空间电压矢量脉宽调制(SVPWM)的基本原理,提出了矢量时间计算的简单算法,采用了快速扇区判断方法,在Matlab/Simulink环境下对SVPWM控制的逆变器系统进行了仿真,并给出了相应的仿真结果,同时基于TI公司DSPLF2407芯片进行了控制算法的设计,给出了算法流程。     

空间矢量脉宽调制在有源滤波器中的应用

文章针对典型的三相整流电路中产生的谐波对电网产生的影响,研究易于数字化的SVPWM,将其应用于并联有源电力滤波器内层跟踪控制中,给出一种补偿功能较为完善的并联有源电力滤波器及其控制方法。仿真结果表明：SVPWM调制用于并联有源滤波控制可以明显改进补偿的动态性能,提高滤波效果。     

General Modulation Strategy for Seven-Phase Inverters With Independent Control of Multiple Voltage Space Vectors

This paper focuses on the analysis of a seven-phase voltage-source inverter for high-performance motor drives. The problem of the modulation strategy of the inverter is solved by combining the multiple space vector representation with traditional carrier-based pulsewidth modulation. This approach leads to the definition of a general modulation strategy that can be usefully utilized in multimotor drives, as well as in multiphase motor drives for improving the torque density. The inverter output voltage capability is investigated, showing that the proposed modulation strategy is able to fully exploit the dc input voltage either in sinusoidal or nonsinusoidal operating conditions. The results obtained in the analytical investigation are confirmed by experimental tests.     

AT89S52单片机在电压空间矢量控制中的应用研究

结合电压空间矢量控制算法的基本原理,提出了一种采用8位单片机控制输出脉宽调制信号的方法,概述了整个硬件组成和软件设计方法,并给出实验数据,波形稳定可靠.