A New Discontinuous PWM Method of Three-Level Inverter for Neutral-Point Voltage Balancing Control

doi:10.11985/2017.04.005

Abstract

Abstract:

In a medium-voltage high-power inverter, there are problems such as high switching frequency and high switching loss. Discontinuous pulse-width modulation (DPWM) can reduce the switching frequency and the switching loss. Generally, the offset voltage is added to reference voltages in the conventional voltage balancing method. However, when using DPWM, the performance of conventional balancing method is limitary because turn-on and turn-off switching occurs at regular interval. In this paper, the causes of the imbalance of the neutral-point are analyzed at first, and then the limitations of traditional control methods are analyzed, and finally the method of adaptive control of intermittent pulse width angle is proposed. The proposed method maintains low switching losses and achieves the effective voltage balancing, without additional hardware and complex calculation. Finally the results obtained through the Matlab/Simulink simulation verify that the effectiveness of the proposed method.

Key words: Three-level inverter, discontinuous pulse width modulation, neutral-point voltage balancing

CLC Number:

TM351

Liu Siqiang,Wang Limei. A New Discontinuous PWM Method of Three-Level Inverter for Neutral-Point Voltage Balancing Control[J]. Journal of Electrical Engineering, 2017, 12(4): 27-32.

Figures/Tables 12

Fig.1

Ta.1

Fig.2

Tab.2

Fig.3

Fig.4

Fig.5

Fig.6

Fig.7

Fig.8

Fig.9

Fig.10

References 12

[1]	谢路耀, 金新民, 吴学智 . 基于零序注入的NPC 三电平变流器中点电位反馈控制[J]. 电工技术学报, 2012,27(12):117-128.
	Xie Luyao, Jin Xinmin, Wu Xuezhi . Neutral point voltage feedback control based on zero sequence injection for NPC three-level converter[J]. Transactions of China Electrotechnical Society, 2012,27(12):117-128.
[2]	D L, J B . Comparison of a soft switched TCM T-type inverter to hard switched inverters for a 3-phase PV grid interface[C]. IEEE Power Electronics and Motion Control Conference(EPE/PEMC), 2012: 1-8.
[3]	周京华, 沈传文, 苏彦民 , 等. 多电平逆变器不连续空间矢量调制策略的研究[J]. 电力电子技术, 2005,39(5):15-19.
	Zhou Jinghua, Shen Chuanwen, Su Yanmin , et al. Research on discontinuous space vector modulation strategy for multilevel inverters[J]. Power Electronic Technology, 2005,39(5):15-19.
[4]	Depenbrock M . Pulse width control of a 3-phase inverter with non-sinusoidal phase voltage[C]. IEEE International Semiconductor Power Conference Record, Lake Buena, 1997: 399-403.
[5]	Alexander D, Williams S . An optimal PWM algorithm implementation in high performance 125 kV·A inverter[C]. IEEE Applied Power Electronics Conference and Exposition, San Diego, USA, 1993: 771-777.
[6]	Kolar J, Ertl H, Zach F . Influence of the modulation method on the conduction and switching losses of a PWM converter system[J]. IEEE Transactions on Industry Application, 1991,27(6):1063-1075. doi: 10.1109/28.108456
[7]	Asiminoaei L, Rodriguez P, Blaabjerg F . Application of discontinuous PWM modulation in active power filters[J]. IEEE Trans. on Power Electronics, 2008,37(4):1692-1706.
[8]	武强 . 二极管箝位型三电平逆变器SVPWM及中点平衡电位研究[D]. 阜新:辽宁工程技术大学, 2010.
[9]	刘凤君 . 多电平逆变技术及其应用[M]. 北京: 机械工业出版社, 2007.
[10]	童鸣庭 . 三相T型三电平非隔离并网逆变器的研究[D]. 合肥:合肥工业大学, 2013.
[11]	张伦健, 谭国俊, 陈利萍 . 基于双调制波技术的三电平Z源逆变器中点电位平衡控制[J]. 电力系统保护与控制, 2013,41(7):91-96. doi: 10.7667/j.issn.1674-3415.2013.07.015
	Zhang Lunjian, Tan Guojun, Chen Liping . Neutral-point potential balance control for three-level Z-source inverters based on double modulation wave technique[J]. Power System Protection and Control, 2013,41(7):91-96. doi: 10.7667/j.issn.1674-3415.2013.07.015
[12]	安少亮, 孙向东, 陈樱娟 , 等. 一种新的不连续PWM统一化实现方法[J]. 中国电机工程学报, 2012,32(24):59-66.
	An Shaoliang, Sun Xiangdong, Chen Yingjuan , et al. A new generalized implementation method of discontinuous PWM[J]. Proceedings of the CSEE, 2012,32(24):59-66.

开关状态	VT_a1	VT_a2	VT_a3	VT_a4	输出电平
P	通	通	断	断	+U_dc/2
O	断	通	通	断	0
N	断	断	通	通	-U_dc/2

矢量	幅值	开关状态		中性点电流
零矢量	0	PPP OOO NNN		–
小矢量	$\frac{1}{3}U_{dc}$	P型	N型	P型	N型
		POO	ONN	I_b+I_c	I_a
		PPO	OON	I_c	I_a+I_b
		OPO	NON	I_a+I_c	I_b
		OPP	NOO	I_a	I_b+I_c
		POP	ONO	I_b	I_a+I_c
		OOP	NNO	I_a+I_b	I_c
中矢量	$\frac{\sqrt{3}}{3}U_{dc}$	PON		I_b
		OPN		I_a
		NPO		I_c
		NOP		I_b
		ONP		I_a
		PNO		I_c
大矢量	$\frac{2}{3}U_{dc}$	PNN		–
		PPN		–
		NPN		–
		NPP		–
		NNP		–
		PNP		–