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| Active Power Backflow Suppression of Cascaded Module Medium-Voltage PV Power Generation System During Single-Phase Short-Circuit Fault |
| Du Lei1, Zhao Tao1, Feng Zhijian1, Wang Mingda2, Wu Mengze2 |
1. School of Electrical Engineering Qingdao University Qingdao 266000 China;
2. School of Electrical and Automation Engineering Hefei University of Technology Hefei 230009 China |
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Abstract Active power backflow is an inherent problem of cascaded H-bridge (CHB) PV grid- tied inverters under the asymmetric grid voltage fault conditions, which may result in the system not having a balanced operation point, the continuous increase of H-bridge DC-bus voltage, and shutdown and disconnection due to overvoltage protection. Aiming at this issue, this paper took the single-phase short-circuit fault with the highest incidence of power grid fault as the research goal, reviewed the existing control methods, and quantitatively analyzed their limitations, that is, it is impossible to avoid active power backflow in the scenario of deep power grid voltage drop and low output power of PV array. On this basis, an active power backflow suppression strategy suitable for cascaded modular medium-voltage PV power generation system under single-phase short-circuit fault was proposed. According to the actual output active power of PV array, the operation of the system is divided into two areas. By reasonably designing the system regulation and adopting different control methods in different operation areas, the adaptability of the CHBPV grid-tied inverter to different output powers and different grid drop depths is improved, and the fault ride through ability of the system is also improved. Finally, the effectiveness and feasibility of the proposed control strategy were verified by the experimental results.
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Received: 21 December 2021
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2022, Vol. 37 
