scholarly journals Power Transfer Control Strategy Based on True Bipolar MMC-MTDC System

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8306
Author(s):  
Can Ding ◽  
Xiaojian Tian ◽  
Taiping Nie ◽  
Zhao Yuan
Keyword(s):  
Direct Current ◽  
Control Strategy ◽  
System Stability ◽  
Power Transfer ◽  
Multilevel Converter ◽  
System Protection ◽  
System Collapse ◽  
Current Transmission ◽  
Dc Line ◽  
Better Than

The true bipolar modular multilevel converter-based multi-terminal direct current (MMC-MTDC) DC transmission line is prone to single-pole grounding fault, which may cause overload and overcurrent of the non-fault DC line with fault poles, resulting in system protection misoperation and system collapse. Therefore, the power transfer control strategy should be adopted to improve system stability. In addition, considering that the commutator stations of true bipolar MMC-MTDC system may have unipolar faults, it is necessary to adopt the control strategy of inter-pole power transfer or inter-station power transfer to improve the transmission capacity of the system under fault conditions. In this paper, a power transfer control strategy is proposed, which is widely applicable to MMC-MTDC system. In the case of line fault, the power transfer takes into account the line power margin and the power margin of converter station. The inter-pole power transfer is better than the inter-station power transfer under the converter station fault condition, and the inter-station power transfer takes into account the priority of the power margin of the converter station. At the same time, based on the Zhangbei four-terminal flexible direct current transmission project, the Zhangbei four-terminal flexible direct current transmission system is built by using PSCAD/EMTDC, and the flexibility and effectiveness of the proposed strategy are verified by simulation.

scholarly journals Hybrid Modulated Model Predictive Control in a Modular Multilevel Converter for Multi-Terminal Direct Current Systems

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1861 ◽  
Author(s):  
Zhi Wu ◽  
Jiawei Chu ◽  
Wei Gu ◽  
Qiang Huang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Direct Current ◽  
Control Strategy ◽  
Power Balance ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Dc Voltage ◽  
Passive Networks ◽  
Ac Systems

In this paper a hybrid modulated model predictive control (HM2PC) strategy for modular-multilevel-converter (MMC) multi-terminal direct current (MTDC) systems is proposed for supplying power to passive networks or weak AC systems, with the control objectives of maintaining the DC voltage, voltage stability and power balance of the proposed system. The proposed strategy preserves the desired characteristics of conventional model predictive control method based on finite control set (FCS-MPC) methods, but deals with high switching frequency, circulating current and steady-state error in a superior way by introducing the calculation of the optimal output voltage level in each bridge arm and the specific duty cycle in each Sub-Module (SM), both of which are well-suited for the control of the MMC system. In addition, an improved multi-point DC voltage control strategy based on active power balanced control is proposed for an MMC-MTDC system supplying power to passive networks or weak AC systems, with the control objective of coordinating the power balance between different stations. An MMC-HVDC simulation model including four stations has been established on MATLAB/Simulink (r2014b MathWorks, Natick, MA, USA). Simulations were performed to validate the feasibility of the proposed control strategy under both steady and transient states. The simulation results prove that the strategy can suppress oscillations in the MMC-MTDC system caused by AC side faults, and that the system can continue functioning if any one of the converters are tripped from the MMC-MTDC network.

scholarly journals Fault Characteristics and Control Strategies of Multiterminal High Voltage Direct Current Transmission Based on Modular Multilevel Converter

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Fei Chang ◽  
Zhongping Yang ◽  
Yi Wang ◽  
Fei Lin ◽  
Shihui Liu
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Wind Farm ◽  
Control Strategies ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
High Voltage Direct Current ◽  
Current Transmission

The modular multilevel converter (MMC) is an emerging voltage source converter topology suitable for multiterminal high voltage direct current transmission based on modular multilevel converter (MMC-MTDC). This paper presents fault characteristics of MMC-MTDC including submodule fault, DC line fault, and fault ride-through of wind farm integration. Meanwhile, the corresponding protection strategies are proposed. The correctness and effectiveness of the control strategies are verified by establishing a three-terminal MMC-MTDC system under the PSCAD/EMTDC electromagnetic transient simulation environment.

scholarly journals Electromechanical Transient Modeling of Line Commutated Converter-Modular Multilevel Converter-Based Hybrid Multi-Terminal High Voltage Direct Current Transmission Systems

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2102 ◽  
Author(s):  
Liang Xiao ◽  
Yan Li ◽  
Huangqing Xiao ◽  
Zheren Zhang ◽  
Zheng Xu
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Power Flow ◽  
Large Scale ◽  
Transient Stability ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Hvdc System ◽  
High Voltage Direct Current ◽  
Current Transmission

A method for electromechanical modeling of line commutated converter (LCC)-modular multilevel converter (MMC)-based hybrid multi-terminal High Voltage Direct Current Transmission (HVDC) systems for large-scale power system transient stability study is proposed. Firstly, the general idea of modeling the LCC-MMC hybrid multi-terminal HVDC system is presented, then the AC-side and DC-side models of the LCC/MMC are established. Different from the conventional first-order DC-side model of the MMC, an improved second-order DC-side model of the MMC is established. Besides considering the firing angle limit of the LCC, a sequential power flow algorithm is proposed for the initialization of LCC-MMC hybrid multi-terminal HVDC system. Lastly, simulations of small scale and large scale power systems embedded with a three-terminal LCC-MMC hybrid HVDC system are performed on the electromechanical simulation platform PSS/E. It is demonstrated that if the firing angle limit is not considered, the accuracy of the power flow solutions will be greatly affected. Steady state calculation and dynamic simulation show that the developed LCC-MMC hybrid MTDC model is accurate enough for electromechanical transient stability studies of large-scale AC/DC system.

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