模块化多电平固态变压器单桥臂电压传感器的电容电压监测与平衡方法

doi:10.19595/j.cnki.1000-6753.tces.251496

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Abstract Real-time monitoring and balancing of submodule（SM）capacitor voltages are prerequisites for the safe and stable operation of modular multilevel converter-based solid-state transformer（MMC SSTs). However, conventional multi-sensor balancing methods require numerous voltage sensors, leading to high hardware costs, while sensorless balancing methods struggle to monitor the real-time status of SM capacitor voltages. Existing research lacks effective methods for reducing the number of sensors in MMC SST capacitor voltage monitoring and balancing. Therefore, this paper proposes a capacitor-voltage monitoring and balancing method using a single-arm voltage sensor, reducing the number of voltage sensors per arm from N to 1.
First, the mathematical model of the MMC SST under sine-square-wave modulation is established. Based on the switching patterns of medium-and high-frequency MMCs, a prediction algorithm for SM capacitor voltages is proposed using a single arm-voltage sensor. Subsequently, by establishing a model for the incremental charge on SM capacitors, the charge-accumulation effect is revealed, clarifying the mechanism behind the voltage imbalance in SM capacitors. Finally, according to the prediction algorithm and the charge-accumulation effect, a monitoring and balancing method for MMC SST SM capacitor voltages is proposed. This method utilizes the pulse width of switching signals and operates with a single sensor. Through real-time monitoring and dynamic adjustment, it monitors and balances SM capacitor voltages under a single-arm-voltage-sensor configuration, ensuring the safe and stable operation of the MMC-H system.
A 10 kV MMC-H SST simulation model was built in Matlab/Simulink. The results demonstrate that compared with traditional N-sensor and sensorless methods, the proposed method achieves comparable capacitor voltage balancing and ripple suppression while significantly reducing the number of sensors. The proposed method offers greater resilience to voltage deviations and lower transmission current stress than the sensorless balancing method. Simulations with added noise and a signal delay show that the proposed method has good anti-interference capability.
A hardware-in-the-loop platform was established for a 10 kV/1 MW MMC-H SST using a Yuankuan MT6060 circuit emulator and a self-developed controller. Comparative experiments on SM capacitor voltage monitoring and balancing were conducted. The results show that, compared to the N-sensor monitoring and balancing method, the proposed method achieves a capacitor voltage prediction error of less than 1%, delivers nearly equivalent capacitor voltage balancing performance, dynamic self-recovery characteristics, and system power transfer performance. Furthermore, it enables capacitor voltage balancing across the entire voltage-gain and full-power-transfer range, exhibiting strong dynamic stability and robustness.

Key words： Capacitor voltage balancing modular multilevel converter based solid-state transformer（MMC SST) single arm-voltage sensor voltage prediction

Received: 28 August 2025

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	Pan Jianyu
	Yin Qian
	Xi Shuyi
	Xu Zhong
	Li Jian

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Pan Jianyu,Yin Qian,Xi Shuyi等. Capacitor Voltage Monitoring and Balancing Method for MMC-Based Solid-State Transformers with Single Arm-Voltage Sensor[J]. Transactions of China Electrotechnical Society, 2026, 41(16): 5564-5577.

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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.251496 OR https://dgjsxb.ces-transaction.com/EN/Y2026/V41/I16/5564

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