计及电压稳定约束的微电网动态最优潮流

为使微电网并网运行满足电压稳定性和经济性要求,将改进后的小扰动电压稳定指标引入微电网最优潮流模型中,并研究了多时段动态负荷下的最优潮流算法。在有载调压变压器模型中引入虚拟节点,以消除模型中的变比及因变比而产生的高阶项,并计及分布式电源及储能单元的影响在直角坐标系中建立了微电网动态优化潮流的二阶新模型。进一步通过在拉格朗日方程进行泰勒展开时保留高阶项和利用近似最小度算法进行节点优化编号,对传统内点法进行改进。修正计算中所使用的常系数海森矩阵与改进内点法相结合,从而提出一种常系数海森矩阵内点法,有效地解决了计算精度与迭代效率之间的矛盾。在ETAP环境下建立微电网模型,应用所提方法进行优化计算,计算结果表明,在改进的小扰动电压稳定指标约束下,所提模型和算法能够满足微电网运行经济性和电压稳定性的要求。

Dynamic Optimal Power Flow of Microgrid Considering Voltage Stability Constraints

In order to meet the demand of voltage stability and operation economy, an improved small disturbance voltage stability index is introduced into the optimized power flow model of microgrid, and a multi-period dynamic optimal power flow algorithm considering load fluctuation is studied. The transformation ratio and high order terms from transformation ratio are eliminated by adding the voltage of the dummy nodes in the on-load tap changer transformer model. In consideration of the influence of the distributed generation and energy storage unit, a new dynamic optimized microgrid second-order model is established in the rectangular coordinate system. The traditional interior point method is improved by keeping the higher order terms during Taylor expansion of the Lagrange equation and numbering of nodes with the adaptive minimum degree(AMD)algorithm. The constant coefficient Hessian matrix used in calculation is combined with the improved interior point method to find the constant coefficient Hessian matrix interior point method. Thus the contradiction between the calculation precision and efficiency of iteration is solved effectively. The microgrid model is established with ETAP software, and the optimal power flow is carried out with the proposed algorithm. The results show that the model and the algorithm can satisfy the requirement of operation economy and voltage stability of microgrid under the constraint on the improved small disturbance voltage stability index.