Transient Voltage Optimization Control for Paralleled Active Support Energy Storage Converters
Zhao Zhengkui1, Han Minxiao1, Chen Laijun2
1. School of Electrical and Electronic Engineering North China Electric Power University Beijing 102206 China; 2. Department of Electrical Engineering and Applied Electronics Tsinghua University Beijing 100084 China
Abstract：The high-proportion wind and solar powers have introduced weak-inertia and low-damping characteristics to power systems. These new changes reduce the ability of grid to resist the voltage and frequency disturbances. Meanwhile, due to the location far away from the main AC grid, the renewable energy bases have relatively weak grid connections. Grid-following inverters based on phase-locked loops have limited frequency and voltage regulation capabilities and cannot actively support grid voltage and frequency. With the employment of voltage-source converters (VSCs) active support control, energy storage systems can mimic the dynamic response of synchronous generators. This endows VSCs with frequency and voltage regulation capabilities and plays a crucial role in enhancing power system stability. Compared to a single VSC, paralleled multiple VSCs can provide greater redundancy and capacity. However, the differences among VSC units in paralleled system can affect system stability and voltage support during grid voltage sags. Based on the above analysis, when the grid voltage experiences a voltage sag fault, the energy storage VSC faces two demands simultaneously: the transient stability requirements and active voltage support to the grid. Furthermore, the two demands are coupled with each other. To analyze the transient coupling characteristics of the paralleled VSC energy storage system, the dynamic response characteristics of internal electromotive force and grid-connection point voltage during transients are analyzed by the geometric relationship in the phasor diagram and the effect of reactive power loop control. The transient energy interaction impact on the stability of the individual VSC is explained based on the equal-area criterion. Moreover, with the phase-plane method, the transient stability of the paralleled VSC system is analyzed. Then, the influence law of control parameters in the power control loop on the transient stability and voltage support ability is summarized. Based on the above, a joint regulation scheme for improved power loops is proposed, which enables the VSC paralleled system to retain transient stability under grid faults of varying voltage-sag severity and raises the transient voltage support capability at the same time. Finally, the theoretical analysis and the proposed method are verified by simulations and experimental results. As a result, the following conclusions can be drawn: (1) During grid voltage sags, transient energy interactions occur among multiple VSC units. This is mainly caused by the power flows during the transient response and the phase angle differences, which further determines the energy direction. (2) The transient interactions of paralleled VSC system during grid voltage sags affect their transient stability. Unstable VSC units provide transient energy to the other more stable ones, which can improve their own stability but reduce the stability of the other highly stable VSC units, until the stability of all units tends to align. (3) During the grid voltage sags, the increased power angles not only reduce the transient stability of paralleled system, but also weaken their voltage support. It is effective to enhance system stability and voltage support by increasing the reactive power voltage coefficient and reducing active power output. (4) The voltage support capability and transient stability of the VSC paralleled system are mutually coupled. By improving power loop, the joint regulation can ensure the stable operation of the multiple VSC units under different grid faults with diverse voltage sag degrees and enhance the transient voltage support performance.
赵正奎, 韩民晓, 陈来军. 主动支撑型储能变流器多机并联的暂态电压优化控制[J]. 电工技术学报, 2026, 41(9): 2991-3004.
Zhao Zhengkui, Han Minxiao, Chen Laijun. Transient Voltage Optimization Control for Paralleled Active Support Energy Storage Converters. Transactions of China Electrotechnical Society, 2026, 41(9): 2991-3004.
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2026, Vol. 41 
