# Suppression of Negative Sequence Current on HVDC Modular Multilevel Converters in Offshore Wind Power

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## Abstract

**:**

## 1. Introduction

## 2. Advantages of HVDC Technology

- (1)
- The harmonic level is low.

- (2)
- The stability of the system is enhanced.

- (3)
- There is no reactive power compensation and no commutation failure.

- (4)
- It has the ability to supply electricity to isolated islands.

- (5)
- It is suitable for constructing a multi-terminal system.

## 3. Analysis of Working Mechanism of MMC Bridge Arm Circuit

#### 3.1. MMC Topology

#### 3.2. Analysis of the Principle of MMC Circulation

## 4. MMC Circulation Suppression Strategy of Improved LADRC

#### 4.1. Design of Circulating Current Suppressor Based on LADRC

#### 4.1.1. Traditional LADRC Controller Structure

#### 4.1.2. Design of Circulating Current Suppressor Based on Traditional LADRC

#### 4.1.3. MMC Control System Based on LADRC Circulating Current Suppressor

#### 4.2. Design of Circulating Current Suppressor Based on AD−LADRC

#### 4.2.1. Improving the Structural Design of LESO

#### 4.2.2. Analysis of Suppressor Performance

- (1)
- Frequency Domain Characteristics of ${\omega}_{0}$ Changes

- (2)
- Frequency Domain Characteristic Curves of LADRC Before and After Improvement

## 5. Simulation Analysis

#### 5.1. Steady-State Operating Condition

#### 5.1.1. Circulation Suppression Effect

#### 5.1.2. Arm Current and Sub-Module Capacitor Voltage

#### 5.1.3. Bridge Arm Current THD

#### 5.2. DC Voltage Transient

## 6. Conclusions

- (1)
- The improved circulating current suppressor can effectively improve the waveform distortion effect of the bridge arm current. In terms of stabilization time, the improved circulating current suppressor is 24.04% and 12.73% shorter than PI and LADRC, respectively. In terms of peak deviation, the improved circulation suppressor is reduced by 45.82% and 24.48% compared with PI and LADRC, respectively.
- (2)
- The second harmonic component is obviously suppressed, and the influence of the circulation can be improved after using the suppressor, so that the waveform is closer to the sine wave.
- (3)
- The fluctuation amplitude of the capacitor voltage and the rate of waveform distortion decreased obviously. The peak difference of the capacitor voltage of the sub-module with suppressor was 1.956 A and that of the sub-module without suppressor was 23.719 A.
- (4)
- When the circulating current suppressor is not used, the bridge arm current THD is 9.74%. When using a PI circulating current suppressor, the bridge arm current THD is 1.82%. When using a LADRC circulating current suppressor, the bridge arm current THD is 1.71%. When using an AD-LADRC circulating current suppressor, the bridge arm current THD is 1.63%. The THD is controlled within the range of 3% THD, and the improved controller is reduced by 10.44% and 4.68% compared with PI and LADRC, respectively.
- (5)
- The increased-order decoupling auto−disturbance rejection suppressor proposed in this paper has stronger rapidity, adaptability and robustness, which is helpful to improve the grid-connected ability of offshore wind farms and provide some theoretical and application support for the development and large-scale utilization of offshore wind power.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Zeng, M.; Cai, Y.; Shen, K. Optimal configuration of new energy grid connected energy storage capacity from the perspective of dual carbon. Int. J. Energy Technol. Policy
**2023**, 18, 326–342. [Google Scholar] [CrossRef] - Watson, C.S.; Somerfield, J.P.; Lemasson, J.A. The global impact of offshore wind farms on ecosystem services. Ocean Coast. Manag.
**2024**, 249, 107023. [Google Scholar] [CrossRef] - Faraggiana, E.; Ghigo, A.; Sirigu, M.; Petracca, E.; Giorgi, G.; Mattiazzo, G.; Bracco, G. Optimal floating offshore wind farms for Mediterranean islands. Renew. Energy
**2024**, 221, 119785. [Google Scholar] [CrossRef] - Han, S.; Rui, H.; Hugo, M. Power quality monitoring in electric grid integrating offshore wind energy: A review. Renew. Sustain. Energy Rev.
**2024**, 191, 114094. [Google Scholar] - Joanna, S.; Mariusz, C.; Joanna, P. Reliability of Renewable Power Generation using the Example of Offshore Wind Farms. Folia Oeconomica Stetin.
**2023**, 23, 228–245. [Google Scholar] - Samsó, R.; Crespin, J.; Olivares, G.A. Examining the Potential of Marine Renewable Energy: A Net Energy Perspective. Sustainability
**2023**, 15, 8050. [Google Scholar] [CrossRef] - Olczak, P.; Surma, T. Energy Productivity Potential of Offshore Wind in Poland and Cooperation with Onshore Wind Farm. Appl. Sci.
**2023**, 13, 4258. [Google Scholar] [CrossRef] - Milad, S.; Mateo, R.; Alejandro, H.; Rodrigo, A. A Review of Offshore Renewable Energy in South America: Current Status and Future Perspectives. Sustainability
**2023**, 15, 1740. [Google Scholar] - Mohammad, B.; Turaj, A.; Deniz, S.V. Floating Offshore Wind Turbines: Current Status and Future Prospects. Energies
**2022**, 16, 2. [Google Scholar] - David, G.; Jensen Paul, D. Chasing after the wind? Green economy strategies, path creation and transitions in the offshore wind industry. Reg. Stud.
**2022**, 56, 1671–1682. [Google Scholar] - Zhong, P.; Rong, Y.; Tai, L. Optimization Design of Voltage Level of Flexible DC Transmission with Offshore Wind Power Based on Genetic Algorithm. J. Phys. Conf. Ser.
**2023**, 2527, 012066. [Google Scholar] - Mujahid, E.; Pillai, A.C.; Longbin, T. Implications of wave–current interaction on the dynamic responses of a floating offshore wind turbine. Ocean Eng.
**2024**, 292, 116571. [Google Scholar] - González, G.W.; Montoya, D.O.; Rodríguez, T.L.C. Optimal Integration of Flexible Alternating Current Transmission Systems in Electrical Distribution Grids Using a Mixed-Integer Convex Model. Algorithms
**2023**, 16, 420. [Google Scholar] [CrossRef] - Peng, L.; Fu, Z.; Xiao, T. An Improved Dual Second-Order Generalized Integrator Phased-Locked Loop Strategy for an Inverter of Flexible High-Voltage Direct Current Transmission Systems under Nonideal Grid Conditions. Processes
**2023**, 11, 2634. [Google Scholar] [CrossRef] - Jiaqi, W.; Zhichao, F.; Xin, L.; Daoyuan, M. A PLL-free control strategy for flexible DC transmission systems. Energy Rep.
**2022**, 8, 1413–1420. [Google Scholar] - Zhu, S.; Liu, K.; Qin, L.; Qing, W.; Yuye, L. Analysis and suppression of DC oscillation caused by DC capacitors in VSC-based offshore island power supply system. IEEJ Trans. Electr. Electron. Eng.
**2019**, 14, 545–555. [Google Scholar] [CrossRef] - Mengting, C.; Peiqiang, S.; Guipeng, C.; Fengyan, F.; Xinlin, Q. Multiple criteria analysis for electrifying off-grid island using renewable energy microgrid or submarine cable. Electr. Power Syst. Res.
**2023**, 224, 109728. [Google Scholar] - Weili, Z.; Tianning, Z. Application of Flexible DC Transmission Technology in Power Grid under Large-scale Development of New Energy. IOP Conf. Ser. Earth Environ. Sci.
**2020**, 440, 032035. [Google Scholar] - Chenhao, L.; Kuan, L.; Changhui, M.; Pengfei, Z.; Qi, T.; Yingtao, S.; Xin, W. Flexible control strategy for HVDC transmission system adapted to intermittent new energy delivery. Glob. Energy Interconnect.
**2021**, 4, 425–433. [Google Scholar] - Xingyang, H.; Kun, C.; Ting, W.; Zengrui, H. Analysis of typical fault characteristics of modular multilevel converter for flexible HVDC transmission. J. Phys. Conf. Ser.
**2022**, 2369, 012067. [Google Scholar] - Pan, R.; Yang, Y.; Yang, J.; Liu, D. Enhanced grid forming control for MMC-HVDC with DC power and voltage regulation. Electr. Power Syst. Res.
**2024**, 229, 110166. [Google Scholar] [CrossRef] - Pan, R.; Liu, D.; Yang, Y.; Yang, J. Network based impedance analysis of grid forming based MMC-HVDC with wind farm integration. Electr. Power Syst. Res.
**2024**, 229, 110120. [Google Scholar] [CrossRef] - Xiaolei, W.; Quan, Z.; Jianying, Z. Control Strategy of Circulating Current Suppression for Modular Multilevel Converter. J. Phys. Conf. Ser.
**2023**, 2564, 012005. [Google Scholar] - Chun, W.; Wenxu, Y.; Wenyuan, W.; Hongyu, N.; Jie, C. The Suppression of Modular Multi-Level Converter Circulation Based on the PIR Virtual Impedance Strategy. World Electr. Veh. J.
**2023**, 14, 17. [Google Scholar] - Manchala, R.N.; J, S.; Mandi, P.R. Circulating Current Suppression Control in Surrogate Network of MMC- HVDC System. Int. J. Recent Technol. Eng.
**2020**, 8, 29–34. [Google Scholar] - Debdeep, S.; Tanmoy, B.; Saurav, D. A Reduced Switching Frequency Sorting Algorithm for Modular Multilevel Converter with Circulating Current Suppression Feature. IEEE Trans. Power Electron.
**2019**, 34, 10480–10491. [Google Scholar] - Jinyu, W.; Jun, L.; Chengfu, W.; Chengfu, W.; Xiaoming, D. Circulating Current Suppression for MMC-HVDC under Unbalanced Grid Conditions. IEEE Trans. Ind. Appl.
**2017**, 53, 3250–3259. [Google Scholar] - Mingguang, Z.; Yao, S.; Huzhong, S.; Richang, G. MMC-HVDC circulating current suppression method based on improved proportional resonance control. Energy Rep.
**2020**, 6, 863–871. [Google Scholar] - Qingrui, T.; Zheng, X.; Minyuan, G.; Xiang, Z.; Jing, Z. Design of circulating current suppression controller for modular multilevel converter. Power Syst. Autom.
**2010**, 34, 57–61. [Google Scholar] - Xiahui, Z.; Minxiao, H.; Jinggang, Y.; Xiangkun, M.; Zijian, Q. Analysis of the influence mechanism of DC side voltage fluctuation on the circulating current of MMC and its suppression method. Power Syst. Autom.
**2021**, 45, 122–131. [Google Scholar] - Semih, I.; Mohammed, A.; Subhashish, B. An Optimized Circulating Current Control Method Based on PR and PI Controller for MMC Applications. IEEE Trans. Ind. Appl.
**2021**, 57, 5074–5085. [Google Scholar] - Zhouzhou, L. MMC-HVDC control and circulation suppression strategy based on quasi-PR controller. J. Power Syst. Autom.
**2016**, 28, 70–75. [Google Scholar] - Xianzheng, L.; Xingcheng, W.; Kai, Z. IMC based circulating current controller for MMC-HVDC. In Proceedings of the 2017 36th Chinese Control Conference (CCC), Dalian, China, 26–28 July 2017; pp. 617–622. [Google Scholar]
- Jingqing, H. Auto disturbance rejection controller and its application. Control. Decis.
**1998**, 13, 19–23. [Google Scholar] - Fang, Z.; Guangyao, Z.; Yan, C. MMC Circulation suppression Strategy based on Linear Auto disturbance rejection Control. J. Electr. Power Syst. Its Autom.
**2018**, 30, 71–78. [Google Scholar] - Yang, X.; Li, Z.; Zheng, Q.T.; Zheng, T. Virtual Impedance Sliding Mode Control-Based MMC Circulating Current Suppressing Strategy. IEEE Access
**2019**, 7, 26229–26240. [Google Scholar] [CrossRef] - Farooq, A. Influence of Unified Power Flow Controller on Flexible Alternating Current Transmission System Devices in 500 kV Transmission Line. J. Electr. Electron. Eng.
**2018**, 6, 12–19. [Google Scholar] [CrossRef] - Zhang, G.; Song, J.; Li, C.; Gu, X. A Circulating Current Suppression Strategy for MMC Based on the 2N+1 PWM Approach. World Electr. Veh. J.
**2023**, 14, 106. [Google Scholar] [CrossRef] - Kun, W.; Kaipei, L.; Zhixuan, Z.; Wei, L.; Liang, Q. Capacitor voltage equalization strategy of modular multilevel converter based on fast sorting algorithm. Electr. Meas. Instrum.
**2018**, 55, 1–7. [Google Scholar] - Xitang, T.; Hongmei, Z.; Qinyue, Z.; Jiangbin, C. Capacitor voltage fluctuation analysis and equalization control of MMC module. Power Electron. Technol.
**2016**, 50, 1–4. [Google Scholar]

**Figure 13.**The effect of whether or not a suppressor is used on the arm current and capacitance voltage.

Parameter Names | Numerical Values |
---|---|

Number of MMC Arm Sub-Modules | 18 |

Sub-Module Capacitance Value/mF | 1.88 |

Arm Inductance Value/mH | 5 |

Initial Value of Sub-Module Capacitor Voltage/V | 1400 |

Frequency/Hz | 50 |

DC Side Voltage/kV | 25.2 |

${\omega}_{0}$ | ${\omega}_{c}$ | ${b}_{0}$ |

350 | 1050 | 2000 |

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## Share and Cite

**MDPI and ACS Style**

Xu, X.; Wang, D.; Zhou, X.; Tao, L.
Suppression of Negative Sequence Current on HVDC Modular Multilevel Converters in Offshore Wind Power. *J. Mar. Sci. Eng.* **2024**, *12*, 383.
https://doi.org/10.3390/jmse12030383

**AMA Style**

Xu X, Wang D, Zhou X, Tao L.
Suppression of Negative Sequence Current on HVDC Modular Multilevel Converters in Offshore Wind Power. *Journal of Marine Science and Engineering*. 2024; 12(3):383.
https://doi.org/10.3390/jmse12030383

**Chicago/Turabian Style**

Xu, Xiaoning, Di Wang, Xuesong Zhou, and Long Tao.
2024. "Suppression of Negative Sequence Current on HVDC Modular Multilevel Converters in Offshore Wind Power" *Journal of Marine Science and Engineering* 12, no. 3: 383.
https://doi.org/10.3390/jmse12030383