Electromagnetic Analysis and Applications
Vol.3 No.03(2014), Article ID:13919,9 pages
DOI:10.12677/EAA.2014.33004

Study of SVPWM Method for Single-Phase Asymmetric Three-Level CapacitanceClamped Inverter

Lin Wang, Xuefeng Hu

School of Electrical and Information Engineering, Anhui University of Technology, Ma’anshan

Email: 407285432@qq.com, 1152830391@qq.com

Received: Jul. 30th, 2014; revised: Aug. 4th, 2014; accepted: Aug. 5th, 2014

ABSTRACT

In this paper, the space vector pulse width modulation (SVPWM) method was proposed for the topology of single-phase asymmetric three-level inverter. Based on the proposed method, the single-phase space vector diagram is divided into four regions, and the output reference voltage vector is synthesized by the two voltage vectors of the region according to the volt-second balance principle. In order to filter harmonic which is contained in the output voltage and create better sine wave, LC filter is widely used in the design to filter harmonic of the output voltage, and a parameter design method is developed for the inductor and capacitor designs. The good performance of the proposed inverter and SVPWM control method is demonstrated by the simulation results.

Keywords:Inverter, Single-Phase Asymmetric Three-Level, Space Vector Pulse Width Modulation (SVPWM), LC Filter

1. 引言

2. 电容钳位型单相不对称三电平逆变器的拓扑结构

Figure 1. Topology of single-phase asymmetric three-level capacitance-clamped inverter

Table 1. Operation states of single-phase asymmetric threelevel capacitance-clamped inverter

3. 模态分析

1) 开关模态1 [S1、S2和S6]导通，VAB = +Vin，当iL > 0时，iL流经S1、S2、L、R和S6，此时，由输入电源向负载提供能量，对应图2(a)；当iL < 0时，iL流经D6、R、L、D2和D1，此时输出端向C1、C2回馈能量，对应图2(b)

2) 开关模态2 [S2、S4和S6]导通，VAB = +Vin/2，当iL > 0时，iL流经C3、S2、L、R、S6和D4，此时由C3向负载提供能量，对应图2(c)；当iL < 0 时，iL流经D6、R、L、D2、C3和S4，此时输出端向C3回馈能量，对应图2(d)

3) 开关模态3 [S3、S4和S6]导通，VAB = +0，此时，逆变器处于续流状态，当iL > 0时，iL流经D4、D3、L、R和S6，对应图2(e)；当iL < 0时，iL流经S3、S4、D6、L和R，对应图2(f)

4) 开关模态4 [S3、S4和S5]导通，VAB = −Vin，当iL > 0时，iL流经D4、D3、L、R和D5，此时输出端

Figure 2. Equivalent circuits of the switching modes

5) 开关模态5 [S2、S4和S5]导通，VAB = −Vin/2，当iL > 0时，iL流经D4、C3、S2、L、R和D5，此时由C3向负载提供能量，对应图2(i)；当iL < 0时，iL流经S5、R、L、D2、C3和S4，此时，输出端向C3回馈能量，对应图2(j)

6) 开关模态6 [S1、S2和S5]导通，VAB = −0，此时逆变器处于续流状态，当iL > 0 时，iL流经S1、S2、L、R和D5，对应图2(k)；当iL < 0时，iL流经D2、D1、R、L和S5，对应图2(l)

4. 电容钳位型单相不对称三电平逆变器SVPWM方法

4.1. 电容钳位型单相不对称三电平逆变器SVPWM图

SVPWM方法在多电平型逆变器中得到了广泛应用[7] -[9] ，用于实现对输出电压电压矢量的合成。电容钳位型单相不对称三电平逆变器共有6个工作状态，可根据电压矢量的模长大小，将单相三电平空间矢量图分成4个区间，根据参考电压矢量V所在的区间，选择该区间内的两个电压矢量进行合成如图3所示。设逆变器希望输出的电压为VAB = MEsinωt，E为直流侧电压值，逆变器输出电压VAB为矢量V在α轴上的投影，矢量V的模长|V| = ME，且矢量以角频率ω逆时针旋转。其中M为调制比，范围在0到1之间。

Table 2. States of the switches and output voltage

Figure 3. Space voltage vector diagram for singlephase asymmetric three-level capacitance-clamped inverter

4.2. 输出电压矢量的作用时间

(1)

(2)

5. LC滤波器设计

LC滤波器的传递函数为：

(3)

LC滤波器的设计

(4)

(5)

(6)

(7)

(8)

LC滤波器截止频率fc为：

(9)

(10)

(11)

(12)

(13)

6. 仿真结果

7. 结论

Table 3. Simulation parameters of the prototype

(a) 逆变器输出电压VAB波形(M = 0.8)  (b) 输出电压VAB频谱(M = 0.8)

Figure 4. Single-phase asymmetric three-level capacitance-clamped inverter simulation waveform before filtering

(a) 逆变器输出电压Vo波形(M = 0.8)  (b) 输出电压Vo频谱(M = 0.8)

Figure 5. Single-phase asymmetric three-level capacitance-clamped inverter simulation waveform after filtering

Figure 6. Voltage stress of the switches

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