分布式电源对故障恢复初期不平衡孤网稳态特性影响

针对故障后恢复初期的薄弱三相不平衡电网,研究了以自励式异步发电机为代表的分布式电源并网后对原有不平衡系统稳态运行特性的影响。以孤网稳态运行数学模型为基础,利用对称分量法并结合相应的误差分析,得出系统的简化等值复合序网及同步发电机支路负序电流比重的理论公式。同时在此基础上分析了负荷量一定的情况下,并网后的分布式电源采用不同的运行调整策略对原系统同步发电机支路电流不平衡度的影响。研究结果表明并网的分布式电源不适当的调节策略反而可能增加原系统同步发电机支路的负序电流比重,降低同步发电机运行的安全性。仿真与理论计算结果的对比分析,验证了本文结论的正确性及有效性。

Effects of Distributed Generation on Steady-State Characteristics of Unbalanced Isolated Power System in Initial Period of Fault Restoration

The impact of self-excited induction generator on the weak three-phase unbalanced power system in the initial period of black-start is studied.The theoretical formula for the proportion of negative sequence current is obtained by analyzing the steady-state model of an isolated power grid utilizing symmetrical components method and error analysis.Based on this formula,the effect of different operational strategies for a distributed generation grid on the unbalanced degree of the branch current of a synchronous generator is analyzed under constant loading.Analysis results show that an inappropriate control strategy for a self-excited induction generator will reduce the security of the synchronous generator instead.Finally,a comparative analysis between the simulation results and the theoretical calculation verifies the accuracy and the validity of the conclusions.