Lack of Var in power system brings the system into instable state and leads to voltage drop and fluctuations. Through increasing stimulation Var is generated by generators in the plants but due to the issues such as generated capability limitation, the generation of Var is limited so the generator cannot supply all the Var required for the system by itself. Therefore if more Var is required, in addition to improve the voltage, using compensators are necessary. In this article, it is tried to determine the location and size of dynamic Var compensators in order to achieve the desired objectives in normal and possible grid circumstances. Owing to this fact that considering all disturbances makes the optimization difficult to achieve and even in some cases makes it impossible, TVSI is proposed to determine the most critical disturbances. In order to reduce the amount of calculations, a preliminary selection has been done to minimize the number of optional locations for installing Var sources. To do this, RIi is used to determine candidate buses for installing the compensators. Var planning has become an MOP issue with the aim of minimizing investment costs for compensators as well as minimizing voltage sensitivity of each bus to the changes of dynamic var requirement. Desired results including minimizing the costs, improving voltage profile, and maintaining voltage stability were obtained through using MOEA/D. the results of the simulations done in PSS/E and MATLAB software environments on the IEEE 39-Bus test case system compared with other methods, demonstrate the effective performance of the proposed method..
