非对称扰动下弱交流系统并网变流器不平衡控制策略研究OA

With the increasing penetration of distributed energy resources,the strength of AC power systems has progressively declined.In weak AC systems,the equivalent grid impedance rises,intensifying interactions between converters and the power grid.Traditional unbalanced control strategies exhibit reduced effectiveness in suppressing twice fundamental frequency power ripples and may even exacerbate transient power oscillations under disturbances.To address this issue,this paper first quantitatively analyzes the limitations of conventional unbalanced control strategies in mitigating power ripples within weak AC systems.Subsequently,a interactive power transfer model is established,incorporating dynamic characteristics of converter control loop,the phase locked loop(PLL),and the transmission line.Furthermore,a composite control-based unbalanced control strategy-dynamic power feed forward compensation(DPFC)is proposed for weak grid applications.By equivalently compensating the oscillatory power generated from closed-loop system interactions into the inverter's power outer loop,the proposed strategy effectively suppresses power ripples during both transient and steady-state operations.Finally,the effectiveness and superiority of the proposed strategy are verified by CHIL and PHIL experiments.