Precisely Simplified Time-Varying Modeling Method Based on the Small-Signal-Waveform Assumptions for a High-Ratio MMC-Based DC Transformer
Precisely Simplified Time-Varying Modeling Method Based on the Small-Signal-Waveform Assumptions for a High-Ratio MMC-Based DC Transformer
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DOI：
10.1109/tpwrd.2023.3325821
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发表时间：
2024-02
影响因子：
4.4
通讯作者：
Chuyang Wang;Li Zhang;Xuan Dong
中科院分区：
文献类型：
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作者：
Chuyang Wang;Li Zhang;Xuan Dong
与典型的MMC系统不同，基于MMC的高变比直流Transformer由于其较高的基频、两级结构和不同的移相控制策略，表现为高速、时变的非线性系统。因此，这样的系统的s域传递函数不能被导出，并且精确简化的系统模型也不可访问。因此，准确地确定系统性能和自适应调整控制器参数波动的工作条件几乎是不可能的。本文试图突破这一瓶颈。首先建立了精细的时变状态方程，同时证明了Transformer的高速时变、相移、两级结构和基于MMC的特性。一个建模方法的基础上的小信号波形假设（SSWA），然后提供了第一次分析操纵这些时变的，非线性的，高阶方程。所确定的模型随后阐明了Transformer的特性，并解决了高阶非线性表达式求解的挑战。它还平衡了模型的精确性、简单性和实用性。此外，本研究将Transformer所提出的模型、控制器的定量设计与传统的自适应控制方法有机地结合起来。这种集成有助于Transformer自动配置其控制器参数，从而确保Transformer具有足够的稳定性和动态性能。仿真和实验验证了所提出的建模方法和改进的控制策略的准确性和有效性。
Unlike the typical MMC system, the high-ratio MMC-based DC transformer behaves as a high-speed, time-varying nonlinear system due to its greater fundamental frequency, two-stage structure, and different phase-shift control strategy. Accordingly, such a system's s-domain transfer function could not be derived, and a precisely simplified system model is also inaccessible. Thus, accurately determining the system performance and adaptively regulating the controller parameters in fluctuating working conditions are scarcely possible. This article attempts to break through this bottleneck. The delicate time-varying state equations are first developed to simultaneously certify the transformer's high-speed time-varying, phase-shift, two-stage-structured and MMC-based characteristics. A modeling method based on the small-signal-waveform assumptions (SSWA) is then provided for the first time to analytically manipulate these time-varying, nonlinear, and high-order equations. The determined model subsequently clarifies the transformer's characteristics and tackles the challenge of high-order nonlinear expression solving. It also equilibrates the model's preciseness, simplicity, and practicality. Furthermore, the study organically integrates the transformer's proposed model, the controller's quantitative design, and traditional adaptive control methods. This integration assists the transformer in automatically configuring its controller parameters, thus ensuring the transformer has sufficient stability and dynamic performance. Simulations and experiments finally demonstrate the accuracy and efficiency of the proposed modeling method and improved control strategy.