中点钳位型三电平逆变器并联系统的零序环流抑制策略

doi:10.19595/j.cnki.1000-6753.tces.L10022

Abstract
Figure/Table
References
Related Citation (4)

Download: PDF (10846 KB) HTML (1 KB)
Export: BibTeX | EndNote (RIS)

Abstract Parallel operation of inverters is the most common and direct means to improve power capacity and power level. However, in parallel inverter system, zero-sequence circulating current (ZSCC) occurs because of the common AC and DC bus. This will lead to distortion of output current and additional device loss, which seriously threatens the stability of the parallel system. The ZSCC of neutral-point-clamped (NPC) three-level inverter parallel system studied in this paper is more complex than that of the two-level parallel inverters, and it is necessary to take both hardware and software measures to suppress it. Most of the existing studies focused on software control strategies to suppress ZSCC. For the use of hardware measures, following the traditional scheme was a common choice. Few studies have been done to improve the traditional hardware measures. This paper optimizes the connecting pattern of the improved LCL, which is a traditional hardware measure commonly used to suppress ZSCC, and forms a module shared capacitance scheme under carrier phase-shifting control. Compared with the traditional improved LCL, the added connection cable has smaller current ripple.
Firstly, the loop of circulating circuit is analyzed according to the switch state of the bridge-leg, and the mathematical and circuit model of ZSCC are established. The circulating current is also quantified by Fourier decomposition. Then, a switch function is introduced to further refine the category of ZSCC. For different types of ZSCC, the generation mechanism is explained, and hardware measures of sharing DC side midline and improved LCL and software measures of quasi-proportional-integral-resonance controller are proposed to suppress the corresponding ZSCC. Simulations and experiments show the validity of the proposed measures. At the same time, experiments show that the proposed methods are also feasible when hardware parameters of each inverter are inconsistent and the inverter modules are put in or removed.
In addition, it should be noted that there is a large high frequency current on the connection cable between the AC filter capacitor midpoint and the DC side capacitor midpoint in the traditional improved LCL. Its overall amplitude is around 100A during the simulation verification, which contains both odd switching frequency ripple with the amplitude of 80A and even switching frequency ripple with the amplitude of 20A. Therefore, an optimization scheme of module common filter capacitance under carrier phase-shifting control is proposed, which transfers the high frequency ripple at odd switching frequency to the common capacitance with no extra circuit. Since the current ripple at odd switching frequency is opposite under carrier phase-shifting control, the auto-cancellation of current ripple component at odd switching frequency is achieved and current ripple component at even switching frequency is doubled, but in general the total current on the connection cable is reduced by nearly 50% to about 50A.
The following conclusions can be drawn from the analysis: (1) For different types of ZSCC, the combined use of hardware and software measures mentioned in this paper can effectively and reliably suppress the ZSCC in the parallel system of NPC three-level inverters. (2) The module shared filter capacitance scheme under carrier phase-shifting control has smaller high frequency ripple on the connection cable and better electromagnetic performance of the device than traditional improved LCL hardware measures while the original effect of ZSCC suppression is maintained. (3) The module shared filter capacitance scheme under carrier phase-shifting control saves the consumption of capacitive components, reduces the current stress of components, which provides the possibility for the high power density design of the prototype.

Key words： Neutral-point-clamped (NPC) three-level inverter parallel inverters system zero-sequence circulating current suppression quasi-proportional-integral-resonant (PIR) controller filter capacitor shared by modules carrier phase-shifting control

Received: 13 January 2023

PACS:

TM464

	Service

	E-mail this article
	Add to my bookshelf
	Add to citation manager
	E-mail Alert
	RSS
	Articles by authors
	Xu Chang
	Gong Jinwu
	Zhang Guoqin
	Dai Kemin
	Zha Xiaoming

Cite this article:

Xu Chang,Gong Jinwu,Zhang Guoqin等. Zero-Sequence Circulating Current Suppression Strategy of Neutral-Point-Clamped Three-Level Inverter Parallel System[J]. Transactions of China Electrotechnical Society, 2023, 38(zk1): 124-135.

URL:

https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.L10022 OR https://dgjsxb.ces-transaction.com/EN/Y2023/V38/Izk1/124

[1] 辛业春, 王延旭, 李国庆, 等. T型三电平并网逆变器有限集模型预测控制快速寻优方法[J].电工技术学报, 2021, 36(8): 1681-1692.
Xin Yechun, Wang Yanxu, Li Guoqing, et al.Finite control set model predictive control method with fast optimization based on T-type three-level grid-connected inverter[J]. Transactions of China Electrotechnical Society, 2021, 36(8): 1681-1692.
[2] 陈杰, 章新颖, 闫震宇, 等. 基于虚拟阻抗的逆变器死区补偿及谐波电流抑制分析[J]. 电工技术学报, 2021, 36(8):1671-1680.
Chen Jie, Zhang Xinyin, Yan Zhenyu, et al.Dead-time effect and background grid-voltage harmonic suppression methods for inverters with virtual impedance control[J]. Transactions of China Electrotechnical Society, 2021, 36(8): 1671-1680.
[3] 李杨, 帅智康, 方俊彬, 等. 基于阻抗测量的多逆变器系统稳定性校验方法[J]. 电力系统自动化, 2021, 45(11): 95-101.
Li Yang, Shuai Zhikang, Fang Junbin, et al.Stability check method for multi-inverter system based on impedance measurement[J]. Automation of Electric Power Systems, 2021, 45(11): 95-101.
[4] 张占俊, 李建文, 董耀, 等. 弱电网下多逆变器并网谐振失稳分析方法[J]. 电气技术, 2020, 21(10): 21-28.
Zhang Zhanjun, Li Jianwen, Dong Yao, et al.Method of resonance instability analysis of multiple grid-connected inverters in weak grid[J]. Electrical Engineering, 2020, 21(10): 21-28.
[5] 涂春鸣, 邹凯星, 高家元, 等. 基于不对称正负反馈效应的PQ功率控制并网逆变器稳定性分析[J]. 电工技术学报, 2023, 38(2): 496-509.
Tu Chunming, Zou Kaixing, Gao Jiayuan, et al.Stability analysis of grid-connected inverter under PQ power control based on asymmetric positive-negative-feedback effects[J]. Transactions of China Electrotechnical Society, 2023, 38(2): 496-509.
[6] 郭寅远, 王龙, 李宗原, 等. 多模块三电平逆变器并联系统环流谐振抑制[J]. 电力电子技术, 2020, 54(11): 121-124.
Guo Yinyuan, Wang Long, Li Zongyuan, et al.Circulating resonance suppression of multi module three-level inverter parallel system[J]. Power Electronics, 2020, 54(11): 121-124.
[7] Shen Zewei, Jiang Dong, Chen Jianan, et al.Circulating current reduction for paralleled inverters with modified zero-CM PWM algorithm[J]. IEEE Transactions on Industry Applications, 2018, 54(4): 3518-3528.
[8] Tcai A, Kwon Y, Pugliese S, et al.Reduction of the circulating current among parallel NPC inverters[J]. IEEE Transactions on Power Electronics, 2021, 36(11): 12504-12514.
[9] Xing Xiangyang, Li Xiaoyan, Qin Changwei, et al.An optimized zero-sequence voltage injection method for eliminating circulating current and reducing common mode voltage of parallel-connected three-level converters[J]. IEEE Transactions on Industrial Electronics, 2020, 67(8): 6583-6596.
[10] Jiang Dong, Shen Zewei, Wang Fei.Common-mode voltage reduction for paralleled inverters[J]. IEEE Transactions on Power Electronics, 2018, 33(5): 3961-3974.
[11] 李晓艳. 非隔离型三电平光伏并网逆变器安全高效控制技术研究[D]. 济南: 山东大学, 2020.
[12] Chen Alian, Zhang Zicheng, Xing Xiangyang, et al.Modeling and suppression of circulating currents for multi-paralleled three-level T-type inverters[J]. IEEE Transactions on Industry Applications, 2019, 55(4): 3978-3988.
[13] 张馨予, 张钢, 钱江林, 等. 具有低次谐波抑制能力的PIR控制器设计[J]. 电工技术学报, 2016, 31(增刊2): 19-27.
Zhang Xinyu, Zhang Gang, Qian Jianglin, et al.Design of PIR controller with the ability of low harmonic damping[J]. Transactions of China Electrotechnical Society, 2016, 31(S2): 19-27.
[14] Ren Biying, Sun Xiangdong, Yu Majing, et al.Circulating current analysis and the improved D-Σ digital control strategy for multiparalleled three-level T-type grid-connected inverters[J]. IEEE Transactions on Industrial Electronics, 2020, 67(4): 2810-2821.
[15] 姚修远, 金新民, 杨捷, 等. 三电平逆变器并联系统的零序环流抑制技术[J]. 电工技术学报, 2014, 29(增刊1): 192-202.
Yao Xiuyuan, Jin Xinmin, Yang Jie, et al.The technology of zero-sequence circulating current reduction for the parallel system of three-level inverters[J]. Transactions of China Electrotechnical Society, 2014, 29(S1): 192-202.
[16] Sun Kai, Lin Xiang, Li Yunwei, et al.Improved modulation mechanism of parallel-operated T-type three-level PWM rectifiers for neutral-point potential balancing and circulating current suppression[J]. IEEE Transactions on Power Electronics, 2018, 33(9): 7466-7479.
[17] 邵章平. 三电平光伏并网逆变器的模块化控制研究[D]. 合肥: 合肥工业大学, 2015.
[18] 陈甜甜. 交错并联三电平逆变器环流及中点平衡控制研究[D]. 合肥: 合肥工业大学, 2020.
[19] Li Xiaoyan, Xing Xiangyang, Zhang Chenghui, et al.Simultaneous common-mode resonance circulating current and leakage current suppression for transformerless three-level T-type PV inverter system[J]. IEEE Transactions on Industrial Electronics, 2019, 66(6): 4457-4467.
[20] Jiang Changpeng, Quan Zhongyi, Zhou Dehong, et al.A centralized CB-MPC to suppress low-frequency ZSCC in modular parallel converters[J]. IEEE Transactions on Industrial Electronics, 2021, 68(4): 2760-2771.
[21] 李林, 郭源博, 张晓华. 双陷波开关频率滤波器LCLDT的设计[J]. 电工技术学报, 2017, 32(8): 256-263.
Li Lin, Guo Yuanbo, Zhang Xiaohua.Design of a double-trap switching frequency harmonics filter LCLDT[J]. Transactions of China Electrotechnical Society, 2017, 32(8): 256-263.