| The receiving system with the characteristics of heavy load, a large proportion of external power input and a rapid increase of air-conditioning and constant power load must have adequate reactive power support. Since dynamic reactive power compensation device can achieve fast dynamic Var compensation well, it has become an important means to solve the voltage / reactive power problem. This paper aims to propose a scientific and effective method to optimize dynamic Var configuration, and the research work around the selection method of number, installation locations and capacities of the dynamic reactive power compensation devices is as follows:First, this paper expounds the relationship between voltage and reactive power,explores the mechanism of transient voltage instability of the receiving system and analyzes the basic principle of dynamic Var compensation in order to lay the theoretical foundation for the research on optimal allocation method of dynamic reactive power compensation device. Then, as the optimal configuration methods of dynamic Var based on a single criterion only focus on a certain technical target so that factors affecting the system transient voltage stability are not considered comprehensively, this paper proposes a multi-criterion optimal configuration method of dynamic Var considering the characteristics of power grid. Each criterion is not independent and has its own focus, including the node importance index, voltage stability index and improved trajectory sensitivity index. The nodes that have an important position in the topological structure and power allocation of the power grid can be identified by node importance index which can also globally and quantificationally analyze the weak nodes that have an important influence on transient voltage stability of the system. At the same time, the nodes whose actual operation voltages are weak through the simulation analysis under the critical faults leading to transient voltage instability of the system can be selected as candidate installation points from the weak nodes determined by the essential characteristics of the power grid in order to reduce the amount of subsequent calculation. Considering the dynamic characteristics of the system, the enhancement effect of transient voltage stability for the whole system can be reflected by trajectory sensitivity index based on the transient voltage stability analysis method, and this index is improved on the basis of existing research, which can determine the set of optimal installation points.Furthermore, for determining the optimal capacity and selecting the location scheme from the installation points determined by the multi-criterion method taking both economic cost and technical performance into account, this paper establishes the objective function of reactive power optimization considering the investment and management cost, the annual electrical energy loss cost and the penalty function of voltage beyond the boundaries. Finally, the allocation scheme meeting the constraints and making the objective function optimal can be determined using quantum genetic algorithm, and the enhancement effect of the transient voltage stability will be verified with simulation under the critical faults based on the transient voltage stability criteria so that the final optimal allocation scheme meeting the requirements of transient voltage stability can be determined.Based on IEEE 39-bus system, each index is calculated and analyzed, and the optimal allocation scheme of dynamic reactive power compensation devices is determined. The effectiveness of the improvement in trajectory sensitivity index and the proposed optimal configuration method of dynamic Var is verified by the simulation. The simulation results show that the proposed method can make dynamic reactive power compensation device give full play to the advantage of improving the power quality and keeping safe and stable operation of the system considering economy simultaneously. |
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