Narrow Pulse Suppression Strategy of Three-Level Converter Considering Digital Control Discreteness in Low Modulation Index Region
Chen Kai1,2, Wen Xuhui1,2, Li Wenshan1,2, Zhang Jian1,2, Shen Lin1,2
1. Key Laboratory of High Density Electromagnetic Power and Systems Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China; 2. University of Chinese Academy of Sciences Beijing 100049 China
Abstract：During the charging process of flywheel driving by permanent magnet synchronous motor, the three-level converter operates in a low modulation index for a long time, and the traditional virtual space vector pulse width modulation (VSVPWM) strategy frequently generates narrow pulses. Due to the discrete nature of digital control, the sector boundaries in the traditional VSVPWM strategy can shift, exacerbating the narrow pulse issue. These narrow pulses lead to significant distortion in the voltage and current waveforms of the converter and even damage the power devices. This paper proposed an analysis method considering the discreteness of motor digital control and a hybrid VSVPWM strategy based on vector sequence optimization. Firstly, the variation characteristics of the voltage reference vector and its influence on sector boundary under digital control were studied based on the steady-state mathematical model of the motor. Then, the minimum pulse width function was established to quantitatively analyze the distribution of narrow pulses in the traditional VSVPWM within the low modulation index region. Consequently, according to the narrow pulse distribution law, a hybrid VSVPWM strategy based on vector sequence optimization was proposed. The traditional VSVPWM (Seg9_VSVPWM), the thirteen-segment VSVPWM (Seg13_VSVPWM), and the proposed hybrid VSVPWM (LH_VSVPWM) were compared. The simulation results show that when the modulation index is 0.1 and 0.3, Seg9_VSVPWM continuously presents narrow pulses less than 2 μs at the boundary between sectors F and A with 672 and 219 times within 1 s. When the modulation index is 0.5, Seg13_VSVPWM would produce the narrowest pulses and accumulate 1 102 times within 1s. However, when the modulation index is 0.1, the proposed LH_VSVPWM eliminates the narrow pulse by optimizing the vector sequence. In addition, LH_VSVPWM has the fewest switching action times in the modulation index of 0.3 and 0.5, which is 5 836 and 5 875 times in 1s, respectively. Meanwhile, the proposed strategy performs well in limiting narrow pulses, occurring only 11 and 32 times within 1 s. The experimental results further demonstrate that LH_VSVPWM can effectively suppress the narrow pulse and keep the minimum pulse width above 6 μs in low modulation index region. Moreover, LH_VSVPWM improves the three-level converter’s output current waveform quality, with THD values of 22.24%, 13.78%, and 17.47% in the modulation index of 0.1, 0.3, and 0.5, respectively. It is the lowest among the three modulation strategies. Compared with Seg9_VSVPWM, the proposed LH_VSVPWM keeps the neutral-point potential balanced during motor start. The following conclusions can be drawn. (1) The discreteness of motor digital control affects the variation characteristics of the voltage reference voltage and sector boundary of VSVPWM, which aggravates the narrow pulse problem. (2) In the low modulation index region of three-level converters, the effective vector durations are short, and the first vector of switching sequence changes between sectors F and A, B and C, and D and E. Therefore, the traditional VSVPWM maximum coding vectors are prone to narrow pulses at the boundary of these sectors. (3) The proposed method effectively suppresses the narrow pulse and reduces the switching times of power devices. Besides, LH_VSVPWM improves output waveform quality and solves the problem of neutral-point potential imbalance during motor startup.
[1] 楼冠男, 秦琦, 顾伟, 等. 考虑移动式储能均衡的微电网群分布式动态协同控制策略[J]. 电力系统自动化, 2023, 47(19): 74-85. Lou Guannan, Qin Qi, Gu Wei, et al.Distributed dynamic cooperative control strategy for microgrid clusters considering equalization of mobile energy storage[J]. Automation of Electric Power Systems, 2023, 47(19): 74-85. [2] 韩应生, 孙海顺, 秦世耀, 等. 电压源型双馈风电并网系统小扰动低频稳定性分析[J]. 电工技术学报, 2023, 38(5): 1312-1324, 1374. Han Yingsheng, Sun Haishun, Qin Shiyao, et al.Low-frequency stability analysis of voltage-sourced doubly-fed wind power grid-connected system under small disturbance[J]. Transactions of China Elec-trotechnical Society, 2023, 38(5): 1312-1324, 1374. [3] 王力, 胡佳成, 曾祥君, 等. 基于混合储能的交直流混联微电网功率分级协调控制策略[J]. 电工技术学报, 2024, 39(8): 2311-2324. Wang Li, Hu Jiacheng, Zeng Xiangjun, et al.Hierarchical coordinated power control strategy for AC-DC hybrid microgrid with hybrid energy storage[J]. Transactions of China Electrotechnical Society, 2024, 39(8): 2311-2324. [4] 郝艺, 周瑀涵, 刘晨曦, 等. 含跟网型储能的新能源多馈入系统小扰动电压支撑强度分析[J]. 电工技术学报, 2024, 39(11): 3569-3580. Hao Yi, Zhou Yuhan, Liu Chenxi, et al.Small disturbance voltage support strength analysis for renewable multi-infeed system with grid-following energy storage[J]. Transactions of China Elec-trotechnical Society, 2024, 39(11): 3569-3580. [5] Li Xiaojun, Anvari B, Palazzolo A, et al. A utility-scale flywheel energy storage system with a shaftless, hubless, high-strength steel rotor[J]. IEEE Transa-ctions on Industrial Electronics, 2018, 65(8): 6667- 6675. [6] 张玮亚, 王紫钰, 汤文杰, 等. 飞轮储能系统双向准谐振软开关DC-DC变换器的研究[J]. 电气技术, 2016, 17(12): 20-24. Zhang Weiya, Wang Ziyu, Tang Wenjie, et al.Research on bi-directional quasi-resonant zero voltage switching DC-DC converter for flywheel energy storage system[J]. Electrical Engineering, 2016, 17(12): 20-24. [7] Takarli Reza, Amini Ali, Khajueezadeh, Moham-madsadegh, et al. A Comprehensive review on flywheel energy storage systems: survey on electrical machine power electronic converters, and control system[J]. IEEE Access, 2023, 11: 81224-81255. [8] Hu Cungang, Yu Xinghuo, Homels D G, et al.An improved virtual space vector modulation scheme for three-level active neutral-point-clamped inverter[J]. IEEE Transactions on Power Electronics, 2017, 32(10): 7419-7434. [9] 王金平, 刘斌, 董浩, 等. 中点钳位型三电平逆变器基于调制波分解的调制策略[J]. 电工技术学报, 2023, 38(12): 3221-3233. Wang Jinping, Liu Bin, Dong Hao, et al.A modulation strategy based on modulation wave decomposition for neutral point clamped three-level inverter[J]. Transactions of China Electrotechnical Society, 2023, 38(12): 3221-3233. [10] Qin Changwei, Li Xiaoyan.Improved virtual space vector modulation scheme for the reduced switch count three-level inverter with balanced and unbalanced neutral-point voltage conditions[J]. IEEE Transactions on Power Electronics, 2023, 38(2): 2092-2104. [11] Lee Y H, Suh B S, Hyun D S.A novel PWM scheme for a three-level voltage source inverter with GTO thyristors[J]. IEEE Transactions on Industry Appli-cations, 1996, 32(2): 260-8. [12] 李敏裕, 马晓军, 魏曙光, 等. 三电平虚拟空间矢量脉宽调制算法窄脉冲抑制研究[J]. 电工技术学报, 2018, 33(14): 3264-3273. Li Minyu, Ma Xiaojun, Wei Shuguang, at al. Research on narrow pulse suppression of three-level virtual space vector pulse width modulation algorithm[J]. Transactions of China Electrotechnical Society, 2018, 33(14): 3264-3273. [13] 李文善, 温旭辉, 张剑, 等. 高频三电平低调制比区窄脉冲抑制混合调制策略[J]. 电机与控制学报, 2021, 25(12): 116-126. Li Wenshan, Wen Xuhui, Zhang Jian, et al.Narrow pulse suppression of high frequency three level converter based on hybrid modulation strategy in low modulation index region[J]. Electric Machines and Control, 2021, 25(12): 116-126. [14] 徐华, 高菊玲, 何礼高. 三电平逆变器SVPWM的死区补偿和窄脉冲处理[J]. 电力电子技术, 2012, 46(1): 26-28. Xu Hua, Gao Juling, He Ligao.The dead-time and narrow pulse compensation of three-level inverter based on SVPWM[J]. Power Electronics, 2012, 46(1): 26-28. [15] Gao Zhan, Ge Qiongxuan, Li Yaohua, et al.Hybrid improved carrier-based PWM Strategy for three-level neutral-point-clamped inverter with wide frequency range[J]. IEEE Transactions on Power Electronics, 2021, 36(7): 8517-8538. [16] 高瞻, 王立欣, 周志达, 等. 适用于三电平逆变器低调制比区域的双极性载波脉宽调制策略研究[J]. 中国电机工程学报, 2023, 43(18): 7254-7267. Gao Zhan, Wang Lixin, Zhou Zhida, et al.Research on bipolar carrier-based PWM strategy suitable for low modulation index region of three-level inverter[J]. Proceedings of the CSEE, 2023, 43(18): 7254-7267. [17] Liu H L, Cho G H.Three-level space vector PWM in low index modulation region avoiding narrow pulse problem[J]. IEEE Transactions on Power Electronics, 1994, 9(5): 481-486. [18] 薄保中, 刘卫国, 苏彦民. 三电平逆变器PWM控制窄脉冲补偿技术的研究[J]. 中国电机工程学报, 2005, 25(10): 60-64. Bo Baozhong, Liu Weiguo, Su Yanmin.Study of compensating technique in PWM control for three-level inverters[J]. Proceedings of the CSEE, 2005, 25(10): 60-64. [19] Ran Wang, Ma Liang, Lin Feng, et al.Zero-sequence voltage injection for narrow pulse compensation and neutral point potential balancing of NPC inverter[C]/2009 IEEE 6th International Power Electronics and Motion Control Conference, Wuhan, 2009: 887-891. [20] 肖宏伟, 何英杰, 刘进军, 等. 基于窄脉冲消除的三电平逆变器矢量不对称死区补偿调制策略研究[J]. 中国电机工程学报, 2021, 41(4): 1386-1397, 1545. Xiao Hongwei, He Yingjie, Liu Jinjun, et al.Research on vector asymmetric dead-time compensation modu-lation strategy of three-level inverter based on narrow pulse elimination[J] Proceedings of the CSEE, 2021, 41(4): 1386-1397, 1545. [21] Busquets-Monge S, Bordonau J, Boroyevich D, et al.The nearest three virtual space vector PWM-a modulation for the comprehensive neutral-point balancing in the three-level NPC inverter[J]. IEEE Power Electronics Letters, 2004, 2(1): 11-15. [22] 白华, 赵争鸣, 张永昌, 等. 最小脉宽特性对高压三电平变频器的影响[J]. 电工技术学报, 2006, 19(12): 60-65. Bai Hua, Zhao Zhengming, Zhang Yongchang, et al.Effect of minimum pulse width on high voltage three-level inverters[J]. Transactions of China Elec-trotechnical Society, 2006, 19(12): 60-65. [23] Guo Feng, Yang Tao, Li Chen, et al.Active modu-lation strategy for capacitor voltage balancing of three-level neutral-point-clamped converters in high-speed drives[J]. IEEE Transactions on Industrial Electronics, 2022, 69(3): 2276-2287. [24] 董志强, 王琛琛, 周明磊, 等. 基于SHEPWM的三电平三相逆变器中点电位主动平衡控制[J]. 电工技术学报, 2024, 39(4): 1147-1158. Dong Zhiqiang, Wang Chenchen, Zhou Minglei, et al.Active NP voltage balance control strategy for three-level three phase inverter under SHEPWM[J]. Transa-ctions of China Electrotechnical Society, 2024, 39(4): 1147-1158.
2025, Vol. 40 
