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.