Voltage Rapid Fluctuation Suppression Strategy for Impact Loads Connected to Weak Grids
Chen Xi1, He Jinwei1, Jiang Wei2, Wang Chengshan1
1. School of Electrical and Information Engineering Tianjin University Tianjin 300072 China; 2. School of Electrical Engineering Southeast University Nanjing 210096 China
Abstract：With the widespread application of impactive loads in industrial power supply systems, the problem of rapid voltage fluctuations in weak grid environments caused by their frequent switching has become increasingly prominent. This paper develops a voltage fluctuation suppression circuit with supercapacitor energy storage. Aiming at the defects of traditional reactive power voltage regulation control methods, such as insufficient dynamic response and limited regulation bandwidth when dealing with such problems, a composite voltage control strategy combining negative feedback of voltage fluctuation quantity and feedforward of load fluctuation power is proposed. Specifically, the system adopts the coordinated control of the DC side DC-DC boost converter and the grid-connected side DC-AC converter. The DC bus voltage is stabilized through the DC-DC boost converter with supercapacitor. Then, the average voltage of the supercapacitor is stabilized by adjusting the DC component of the active power of the device. At the same time, the power fluctuation component is adjusted through the proposed composite voltage control to suppress the voltage fluctuation at the point of common coupling (PCC). In addition, a voltage fluctuation model at the PCC and a DC voltage fluctuation model of the system are established. Through the analysis of the root locus and frequency response, it is proved that the proposed method can maintain the stability of the DC bus and has a better ability to suppress rapid voltage fluctuations compared with traditional methods. The simulation results show that in the weak grid scenario with a short-circuit ratio of 7.04, the proposed voltage fluctuation suppression control reduces the voltage fluctuation rate from 10.6% to 1.7%, which is 5.4% lower than the traditional reactive power voltage regulation control. The experimental results indicate that in terms of the dynamic performance of the DC voltage, the DC bus voltage fluctuation is controlled within ±0.5%, and the supercapacitor voltage fluctuation amplitude is maintained at ±2.7%. It can be seen that the DC bus voltage of the proposed system can effectively avoid the influence of the disturbance source on the grid side. Both the simulation and experiment verify the effectiveness and superiority of the proposed voltage fluctuation suppression control. The voltage fluctuation suppression device and strategy proposed in this paper achieve a rapid response and efficient suppression of the voltage fluctuation at the PCC through the composite voltage control combining the negative feedback control of the voltage fluctuation quantity and the feedforward of the load fluctuation power. Compared with the traditional reactive power voltage regulation control, the proposed control has a better ability to suppress rapid voltage fluctuations caused by different disturbance sources. At the same time, the proposed system takes advantage of the difference in the dynamic response time between the supercapacitor voltage regulation control and the DC bus voltage regulation control. The DC bus voltage is quickly stabilized through the DC-DC boost converter with supercapacitor, and then the supercapacitor voltage is stabilized by adjusting the DC component of the output active power of the device. This prevents problems such as the amplification of harmonic currents on the grid side caused by the DC bus voltage fluctuation and the damage to the equipment caused by overcharging and over-discharging of the supercapacitor, and realizes the decoupling of the supercapacitor voltage regulation control and the output of the composite voltage control.
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2026, Vol. 41 
