Bipolar Modular Multilevel DC Transformer Based on Magnetic Component Self-Balancing

doi:10.16628/j.cnki.2095-8188.2023.05.005

Abstract

Abstract:

The bipolar modular multilevel DC transformer meets the needs of low-voltage users for multiple voltage levels,reliable power supply and power safety.The voltage imbalance and instability caused by the power imbalance between the two DC poles are a technical challenge.A bipolar modular multilevel DC transformer topology based on magnetic component self-balancing is proposed based on a diode-neutral clamped three level half bridge converter.The self-balancing mechanism is described,the current stress on the switching devices is analysed,and an overall control strategy is given.Compared to the additional use of a voltage balancer,it has the advantages of a smaller number of switching devices,a smaller footprint and a higher voltage balancing capability.Finally,a simulation model based on MATLAB/Simulink is built to verify the effectiveness and feasibility of the proposed topology and control strategy.

Key words: modular multilevel, DC transformer, bipolar wiring, self-balancing

CLC Number:

TM464

WANG Fu, LI Zheng. Bipolar Modular Multilevel DC Transformer Based on Magnetic Component Self-Balancing[J]. LOW VOLTAGE APPARATUS, 2023, 0(5): 30-36.

Figures/Tables 11

References 18

[1]	PEI W, DENG W, ZHANG X, et al. Potential of Using Multiterminal LVDC to Improve Plug-In Electric Vehicle Integration in an Existing Distribution Network[J]. IEEE Transactions on Industrial Electronics, 2015, 62(5):3101-3111. doi: 10.1109/TIE.2014.2379219
[2]	MOHAMMED A A, JOSEPH S C, DHANESH P R. LVDC architecture for residential application:2016 IEEE International Conference on Power Electronics,Drives and Energy Systems (PEDES)[C]. 2016.
[3]	李学军, 张一瑾, 赵尔敏, 等. 接入氢储能的低压直流系统及其商业模式构建[J]. 电器与能效管理技术, 2021(7):29-33.
[4]	韩文辉. 用于直流配电网的双有源桥直流偏置抑制研究[J]. 电器与能效管理技术, 2021(9):91-99.
[5]	RODRIGUEZ-DIAZ E, FANG C, VASQUEZ J C, et al. Voltage-level selection of future two-level lvdc distribution grids:a compromise between grid compatibiliy,safety,and efficiency[J]. IEEE Electrification Magazine, 2016, 4(2):20-28. doi: 10.1109/MELE.2016.2543979
[6]	KAKIGANO H, MIURA Y, ISE T. Low-voltage bipolar-type dc microgrid for super high quality distribution[J]. IEEE Transactions on Power Electronics, 2010, 25(12):3066-3075. doi: 10.1109/TPEL.2010.2077682
[7]	GU Y, LI W, HE X. Analysis and control of bipolar lvdc grid with dc symmetrical component method[J]. IEEE Transactions on Power Systems, 2015, 31(1):685-694. doi: 10.1109/TPWRS.2015.2403310
[8]	张建文, 周剑桥, 施刚, 等. 基于环流注入控制的MMC型固态变压器低压直流真双极运行方案[J]. 中国电机工程学报, 2021, 41(7):2350-2363.
[9]	LEE J, CHO Y, JUNG J. Single-stage voltage balancer with high-frequency isolation for bipolar lvdc distribution system[J]. IEEE Transactions on Industrial Electronics, 2020, 67(5):3596-3606. doi: 10.1109/TIE.41
[10]	LI B, FU Q, MAO S, et al. DC/DC converter for bipolar lvdc system with integrated voltage balance capability[J]. IEEE Transactions on Power Electronics, 2021, 36(5):5415-5424. doi: 10.1109/TPEL.63
[11]	KENZELMANN S, DUJIC D, CANALES F, et al. Modular DC/DC converter:Comparison of modulation methods:Power Electronics & Motion Control Conference[C]. 2012.
[12]	ZHAO B, SONG Q, LI J, et al. High-frequency-link modulation methodology of DC/DC transformer based on modular multilevel converter for hvdc application:Comprehensive analysis and experimental verification[J]. IEEE Transactions on Power Electronics, 2017, 32(5):3413-3424. doi: 10.1109/TPEL.2016.2586196
[13]	GOWAID I A, ADAM G P, MASSOUD A M, et al. Quasi two-level operation of modular multilevel converter for use in a high-power dc transformer with dc fault isolation capability[J]. IEEE Transactions on Power Electronics, 2014, 30(1):108-123. doi: 10.1109/TPEL.2014.2306453
[14]	MEI J, SHEN K, XIAO B L, et al. A new selective loop bias mapping phase disposition pwm with dynamic voltage balance capability for modular multilevel converter[J]. IEEE Transactions on Industrial Electronics, 2013, 61(2):798-807. doi: 10.1109/TIE.2013.2253069
[15]	DARUS R, POU J, KONSTANTINOU G, et al. A modified voltage balancing algorithm for the modular multilevel converter:evaluation for staircase and phase-disposition PWM[J]. Power Electronics IEEE Transactions on, 2015, 30(8):4119-4127. doi: 10.1109/TPEL.2014.2359005
[16]	SUN C, MOU Y, ZHANG J, et al. Cell voltage balancing control of isolated modular multilevel DC/DC converter using inter-submodule phase-shift modulation scheme:2016 IEEE 11th Conference on Industrial Electronics and Applications (ICIEA)[C]. 2016.
[17]	赖锦木, 尹项根, 孙冠群, 等. 隔离型模块化多电平直流变换器子模块电容电压综合控制策略[J]. 中国电机工程学报, 2021, 41(21):7410-7425.
[18]	赵彪, 宋强. 双主动全桥DC/DC变换器的理论和应用技术[M]. 北京: 科学出版社, 2017.

参数	符号	数值
中压侧电压/kV	U_MV	20
正、负极直流线路间的电压/V	U_LV	750
正、负极输出电容/mF	C_LV1,C_LV2	50
隔直电容/mF	C_b	7
子模块电容/μF	C_SM	10
子模块个数/个	N	4
平衡电感/μH	L_b	26.5
桥臂电感/mH	L_p	0.2
折算到一次侧的隔离变压器漏感/mH	L_σ	0.05
外接电感/mH	L_k	3.5
开关频率/kHz	f_s	10
隔离变压器匝数比	n	53.33
负载工况1/Ω	R₁,R₂	0.28,0.28
负载工况2/Ω	R₁,R₂	0.28,￥