Abstract Due to the instantaneous power imbalance between AC and DC sides, DC secondary ripple voltage is generated in the single-phase half-bridge transformer-less UPQC during grid-connected and islanded modes. In grid-connected mode, the DC secondary ripple voltage would degrade the compensation performance of UPQC. This paper introduces a trap filter to the parallel-side converter's voltage loop and improves the sub-harmonic control in the current loop. For the series-side converter, a third harmonic voltage control is added to the current loop for voltage compensation. In islanded mode, this paper proposes a novel method that utilizes the idle series-side converter and reused split DC capacitors to build an active power decoupling circuit. It can effectively suppress secondary ripple voltage without additional power decoupling circuit components. Moreover, with the proposed compensation and suppression strategies for secondary ripple, the design of DC capacitor parameters can be optimized to further reduce the volume of the UPQC equipment. Firstly, by analyzing the impact of DC voltage ripple on UPQC, different control strategies are developed for different sides of converters. Secondly, a notch filter is added to the voltage outer loop of the parallel side converter, and a sub-harmonic control is added to the current inner loop, which suppresses the impact from the DC voltage ripple. On the series side, a third harmonic voltage control is introduced to the current inner loop of the converter, significantly reducing the THD of the grid side current and load voltage. Thirdly, the generation of the secondary ripple voltage of a two-stage single-phase DC-AC converter in islanded mode is analyzed. Composed of UPQC idle series converter and DC side shunt capacitor, a symmetrical half-bridge active power decoupling circuit is proposed to reduce the voltage ripple. Simulation and experimental results show that UPQC with proposed control in grid-connected mode can achieve 30% voltage compensation for grid under voltage and overvoltage, and the grid current THD is less than 3%. In islanded mode, the DC secondary ripple voltage of a single-phase inverter can be effectively reduced by the proposed active power decoupling circuit under different loading conditions, and the maximum reduction in DC secondary ripple voltage is 75%. Moreover, 64% of the DC capacitance can be reduced compared to the traditional passive power decoupling method. The following conclusions can be drawn: (1) In grid-connected mode, compared with the transient current control, the voltage-current double-loop control based on single-phase dq decoupling with trap filters and sub-harmonic compensation can effectively reduce the grid current THD. (2) In islanded mode, the proposed active power decoupling method significantly reduces the THD of the load voltage with the increase of load power. (3) Compared with the DC capacitance increment, the proposed active power decoupling method has better performance in reducing the total DC secondary voltage ripple. Thus, the proposed compensation and suppression strategies can reduce DC bus capacitance, further improving the power density of UPQC.
Ma Lan,Cao Xiaoqi,Zhang Ying等. Secondary Ripple Compensation and Suppression Strategy for Single-Phase Unified Power Quality Conditioner[J]. Transactions of China Electrotechnical Society, 2024, 39(22): 7197-7212.
[1] Yang Ruohuan, Jin Jianxun.Unified power quality conditioner with advanced dual control for per- formance improvement of DFIG-based wind farm[J]. IEEE Transactions on Sustainable Energy, 2021, 12(1): 116-126. [2] 孟令辉, 舒泽亮, 闫晗, 等. 基于特征次谐波补偿的单相统一电能质量调节器并联变换器控制策略[J]. 电工技术学报, 2020, 35(24): 5125-5133. Meng Linghui, Shu Zeliang, Yan Han, et al.Control strategy for single-phase unified power quality conditioner of parallel converter based on specific order harmonics compensation[J]. Transactions of China Electrotechnical Society, 2020, 35(24): 5125-5133. [3] 江畅, 程启明, 马信乔, 等. 不平衡电网电压下基于模块化多电平变流器的统一电能质量调节器的微分平坦控制[J]. 电工技术学报, 2021, 36(16): 3410-3421. Jiang Chang, Cheng Qiming, Ma Xinqiao, et al.Differential flat control for unified power quality controller based on modular multilevel converter under unbalanced grid voltage[J]. Transactions of China Electrotechnical Society, 2021, 36(16): 3410-3421. [4] 杨用春, 肖湘宁, 郭世枭, 等. 基于模块化多电平变流器的统一电能质量调节器工程实验装置研究[J]. 电工技术学报, 2018, 33(16): 3743-3755. Yang Yongchun, Xiao Xiangning, Guo Shixiao, et al.Research of unified power quality conditioner engineering experiment device based on modular multilevel converter[J]. Transactions of China Electrotechnical Society, 2018, 33(16): 3743-3755. [5] Millnitz dos Santos R J, da Cunha J C, Mezaroba M. A simplified control technique for a dual unified power quality conditioner[J]. IEEE Transactions on Industrial Electronics, 2014, 61(11): 5851-5860. [6] 肖丽平, 吕超, 田紫君. 统一电能质量调节器的结构及控制策略综述[J]. 智慧电力, 2021, 49(12): 1-10. Xiao Liping, Lü Chao, Tian Zijun.Review of structure and control strategy of unified power quality conditioner[J]. Smart Power, 2021, 49(12): 1-10. [7] 张震霄, 年珩, 李培, 等. 储能型统一电能质量调节器电压补偿能力分析及提升方法[J]. 电力系统自动化, 2022, 46(23): 151-159. Zhang Zhenxiao, Nian Heng, Li Pei, et al.Voltage compensation capability analysis and improvement method for unified power quality conditioner with energy storage[J]. Automation of Electric Power Systems, 2022, 46(23): 151-159. [8] 黄晓明, 范志华, 苗世洪, 等. 含储能单元的统一电能质量调节器功率协调控制策略[J]. 高电压技术, 2018, 44(10): 3390-3398. Huang Xiaoming, Fan Zhihua, Miao Shihong, et al.Coordinated power control strategy of unified power quality conditioner with energy storage unit[J]. High Voltage Engineering, 2018, 44(10): 3390-3398. [9] Cheung V S P, Yeung R S C, Chung H S H, et al. A transformer-less unified power quality conditioner with fast dynamic control[J]. IEEE Transactions on Power Electronics, 2018, 33(5): 3926-3937. [10] da Silva S A O, Negrão F A. Single-phase to three-phase unified power quality conditioner applied in single-wire earth return electric power distribution grids[J]. IEEE Transactions on Power Electronics, 2018, 33(5): 3950-3960. [11] 刘永露, 袁银浩, 王辉, 等. 模块化解耦电路的协同控制策略[J/OL]. 电工技术学报, 2023, https://doi.org/10.19595/j.cnki.1000-6753.tces.230363. Liu Yonglu, Yuan Yinhao, Wang Hui, et al. Cooper ative control strategy for modular decoupling cir-cuits[J/OL]. Transactions of China Electrotechnical Society, 2023, https://doi.org/10.19595/j.cnki.1000-6753.tces.230363. [12] 宋健, 宋文祥, 张钦清. 直流母线小电容永磁同步电机驱动系统网侧电流谐波抑制策略[J/OL]. 电工技术学报, 2023, https://doi.org/10.19595/j.cnki.1000-6753.tces.231005. Song Jian, Song Wenxiang, Zhang Qinqing. Harmonic suppression strategy of grid side current for DC-link small capacitor permanent magnet synchronous motor drive system[J/OL]. Transactions of China Elec- trotechnical Society, 2023, https://doi.org/10.19595/j.cnki.1000-6753.tces.231005. [13] Tsai M T, Tsai C.Energy recycling for electrical AC power source burn-in test[J]. IEEE Transactions on Industrial Electronics, 2000, 47(4): 974-976. [14] 高吉磊, 张雅静, 林飞, 等. 单相PWM整流器谐波电流抑制算法研究[J]. 中国电机工程学报, 2010, 30(21): 32-39. Gao Jilei, Zhang Yajing, Lin Fei, et al.Research on harmonic current elimination method of single-phase PWM rectifiers[J]. Proceedings of the CSEE, 2010, 30(21): 32-39. [15] Choudhury S R, Das A, Anand S, et al.Adaptive shunt filtering control of UPQC for increased nonlinear loads[J]. IET Power Electronics, 2019, 12(2): 330-336. [16] 谭智力, 朱冬姣, 陈坚. 三相四线UPQC直流侧电容电压波动机理及抑制方法[J]. 电力系统自动化, 2010, 34(7): 61-65, 74. Tan Zhili, Zhu Dongjiao, Chen Jian.DC side capacitor voltage fluctuation reason and inhibition method for three-phase four-wire UPQC[J]. Automation of Electric Power Systems, 2010, 34(7): 61-65, 74. [17] 苟斌, 冯晓云, 宋文胜, 等. 牵引变流器-电机拍频现象及其抑制方法[J]. 中国电机工程学报, 2013, 33(9): 55-63. Gou Bin, Feng Xiaoyun, Song Wensheng, et al.Analysis and suppression of beat phenomenon for railway traction converters and motors[J]. Proceedings of the CSEE, 2013, 33(9): 55-63. [18] 殷晓东, 罗登, 李祖勇, 等. 一种双向隔离DC-DC变换器二次纹波电压抑制方法[J]. 电工技术学报, 2018, 33(6): 1356-1363. Yin Xiaodong, Luo Deng, Li Zuyong, et al.A second-order ripple voltage suppression algorithm of bidirectional isolation DC-DC converter[J]. Transa- ctions of China Electrotechnical Society, 2018, 33(6): 1356-1363. [19] Rong Yuanjie, Li Chunwen, Tang Honghai, et al.Output feedback control of single-phase UPQC based on a novel model[J]. IEEE Transactions on Power Delivery, 2009, 24(3): 1586-1597. [20] Kwan K H, So P L, Chu Y C.An output regulation- based unified power quality conditioner with Kalman filters[J]. IEEE Transactions on Industrial Electronics, 2012, 59(11): 4248-4262. [21] 叶宗彬, 侯波, 张延澳, 等. 一种三相对称系统快速谐波检测算法[J]. 电工技术学报, 2023, 38(2): 510-522. Ye Zongbin, Hou Bo, Zhang Yan'ao, et al. A fast harmonic detection algorithm for three-phase symmetric systems[J]. Transactions of China Electrotechnical Society, 2023, 38(2): 510-522. [22] Shu Zeliang, Xie Shaofeng, Li Qunzhan.Single-phase back-to-back converter for active power balancing, reactive power compensation, and harmonic filtering in traction power system[J]. IEEE Transactions on Power Electronics, 2011, 26(2): 334-343. [23] Meng Linghui, Ma Lan, Zhu Weiwei, et al.Control strategy of single-phase UPQC for suppressing the influences of low-frequency DC-link voltage ripple[J]. IEEE Transactions on Power Electronics, 2022, 37(2): 2113-2124. [24] 徐卿瀚, 蒙显辉, 杨苓, 等. 直流微电网储能系统的NF+QPR+LPF双闭环2次谐波电流抑制方法[J]. 电工技术学报, 2022, 37(20): 5188-5200. Xu Qinghan, Meng Xianhui, Yang Ling, et al.NF+QPR+LPF dual-loop secondary harmonic current suppression method for energy storage system in DC microgrid[J]. Transactions of China Electrotechnical Society, 2022, 37(20): 5188-5200. [25] 陈强, 李睿, 蔡旭. 链式储能系统电池侧二次脉动功率的抑制方法[J]. 电工技术学报, 2015, 30(8): 231-237. Chen Qiang, Li Rui, Cai Xu.Method of second-order ripple power suppression for battery in cascaded H-bridge storage system[J]. Transactions of China Electrotechnical Society, 2015, 30(8): 231-237. [26] 林国庆, 黄远彬. 两开关无电解电容LED驱动电路拓扑及控制策略[J/OL]. 电工技术学报, 2023, https://doi.org/10.19595/j.cnki.1000-6753.tces.231292. Lin Guoqing, Huang Yuanbin. Two-switch electrolytic capacitor-less LED driving circuit topology and control strategy[J/OL]. Transactions of China Elec- trotechnical Society, 2023, https://doi.org/10.19595/j.cnki.1000-6753.tces.231292. [27] 姚文利. 微电网中单相变换器功率解耦及优化技术研究[D]. 西安: 西北工业大学, 2017. Yao Wenli.Research on optimization of the power decoupling technology for single phase converter in Mirco-Grid[D]. Xi'an: Northwestemn Polytechnical University, 2017. [28] 刘国东. APF-双向DC/DC功能复合型变流器控制策略研究[D]. 北京: 北京交通大学, 2019. Liu Guodong.Study on control strategy of APF- bidirectional DC/DC functional composite converter[D]. Beijing: Beijing Jiaotong University, 2019. [29] Wang Ruxi, Wang Fei, Boroyevich D, et al.A high power density single-phase PWM rectifier with active ripple energy storage[J]. IEEE Transactions on Power Electronics, 2010, 26(5): 1430-1443. [30] 张帅平. 单相电压型PWM整流器直流侧二倍频脉动抑制策略研究[D]. 秦皇岛: 燕山大学, 2021. Zhang Shuaiping.Research on the strategy of suppressing the double frequency ripple in DC side of single-phase voltage source PWM rectifier[D]. Qinhuangdao: Yanshan University, 2021. [31] Shimizu T, Fujita T, Kimura G, et al.A unity power factor PWM rectifier with DC ripple compensation[J]. IEEE Transactions on Industrial Electronics, 1997, 44(4): 447-455. [32] Tang Yi, Blaabjerg F, Loh P C, et al.Decoupling of fluctuating power in single-phase systems through a symmetrical half-bridge circuit[J]. IEEE Transactions on Power Electronics, 2015, 30(4): 1855-1865. [33] Tang Yi, Qin Zian, Blaabjerg F, et al.A dual voltage control strategy for single-phase PWM converters with power decoupling function[J]. IEEE Transactions on Power Electronics, 2015, 30(12): 7060-7071. [34] Li Sinan, Qi Wenlong, Tan S C, et al.Integration of an active filter and a single-phase AC/DC converter with reduced capacitance requirement and component count[J]. IEEE Transactions on Power Electronics, 2016, 31(6): 4121-4137. [35] 唐龙飞, 刘晓东, 刘宿城, 等. 一种对称半桥解耦电路控制方法及应用分析[J]. 电力电子技术, 2021, 55(6): 91-94, 108. Tang Longfei, Liu Xiaodong, Liu Sucheng, et al.Control method and application analysis of a symmetrical half-bridge decoupling circuit[J]. Power Electronics, 2021, 55(6): 91-94, 108.
2024, Vol. 39 
