Decentralized Control for Multi-Terminal Cascaded Medium-Voltage Converters Considering Multiple Crossovers
Decentralized Control for Multi-Terminal Cascaded Medium-Voltage Converters Considering Multiple Crossovers
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DOI：
10.1109/tpwrd.2023.3268829
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发表时间：
2024-02
影响因子：
4.4
通讯作者：
Jinlei Chen;Sheng Wang;Jun Liang;R. Navaratne;Wenlong Ming
中科院分区：
文献类型：
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作者：
Jinlei Chen;Sheng Wang;Jun Liang;R. Navaratne;Wenlong Ming
采用多下垂特性的分散控制可以显著提高中压直流电网潮流的精度。然而，由于控制特性的不同而引起的多次交叉会导致功率和电压的漂移和不稳定问题。当在级联三电平中性点箝位（C3L-NPC）变换器中实现这种类型的控制时，一方面，没有研究这种功率和电压漂移的机理。另一方面，功率控制精度、跨子模块直流电压平衡和多个分频器都需要考虑，这就需要合适的控制方法。为了解决这些问题，首先分析了电源和直流电压漂移的机制。其次，提出了一种提高功率控制精度和直流电压平衡并行性的控制方案，避免了多次交叉；这是通过适当的下垂增益设计和增加二次功率补偿器来实现的。通过MATLAB/Simulink仿真验证了所提出的控制方案，并在三端MVdc试验台上进行了实验验证。结果表明，由于消除了多次交叉，稳态潮流精度提高了15%，而二次功率补偿器的动态功率精度提高了13%。
Decentralized control with multiple droop characteristics can significantly improve the accuracy of power flow in medium-voltage direct-current (MVdc) networks. However, multiple crossovers caused by different control characteristics can lead to the drifts of power and voltage and instability issues. When this type of control is implemented in the cascaded three-level neutral-point-clamped (C3L-NPC) converters, on one hand, the mechanism of such the power and voltage drifts was not investigated. On the other hand, power control accuracy, dc voltage balancing across submodules (SMs) and multiple crossovers should all be considered, which requires suitable control methods. To address the challenges, firstly, the mechanism behind the power and dc voltage drifts is analyzed. Secondly, a control scheme is presented to improve the power control accuracy and dc voltage balancing and concurrently, to avoid the multiple crossovers. This is achieved by suitable droop gain design and adding a secondary power compensator. The presented control scheme is verified in MATLAB/Simulink simulation and experimentally validated in a three-terminal MVdc testbed. Results show that the accuracy of steady-state power flow is improved by 15% due to the elimination of multiple crossovers, while the power accuracy at dynamics improved by 13% with the secondary power compensator.