| Under the background that smart grid construction is widely used in the field of distributed generation(DG),the uncertainty of DG output brings to the power system problems such as voltage quality,stability.Therefore,the active distribution network(ADN)technology has become the key to support efficiently the system operation connected with high proportion of renewable energy and improve the safety and stability of the system.At present,only a few literatures report the active voltage support of ADN by micro grid.With the increase of the number of microgrids in ADN and the increasing capacity of each DG grid-connected converter in microgrid,it is of great practical significance to control microgrid for providing better active voltage support in ADN.Then,it is available to promote the comprehensive control level of regional voltage and reduce the construction cost of high-performance voltage regulator in ADN.In order to tap the potential of voltage support of micro grid in ADN,the paper presents an idea,model and scheme of reactive power optimization and coordination in ADN with microgrid voltage regulation.First of all,the area where the microgrid participates in voltage regulation in the ADN is defined.Based on the difference of the impact of microgrid’s access on node voltage,the clustering algorithm is used to cluster the voltage changes of each node,and different voltage zones are classified.Secondly,the voltage regulation scheme of microgrid in its voltage regulation area is explored.Based on the controllability of the power interaction at entry points of microgrid,a multi-objective optimal dispatching model of ADN considering the voltage regulation effect of microgrid is proposed.Moreover,the optimal dispatching scheme of the power of day-ahead entry points is obtained considering the operation cost of microgrid,the voltage deviation of ADN and the minimization of network loss.When the output of microgrid reaches the upper limit,the areas with voltage deviation and non-microgrid voltage regulation areas are classified as the reactive power compensation voltage regulation areas of distribution network.Based on the ADN control of traditional voltage regulation equipment(capacitors,distribution static synchronous compensator),an ADN reactive power optimization and coordination model considering the effect of microgrid voltage regulation is established under the constraints of investment,maintenance,operation and minimization of network loss cost of dynamic and static reactive power compensation device.Finally,the optimal reactive power allocation scheme of distribution network with micro grid participating in voltage regulation is realized.In view of the influence of the power interaction between the microgrid and the distribution network on the power flow of the ADN when the microgrid participates in the voltage regulation of the distribution network,based on the difference of the influence of microgrid’s access on the voltage change of each node in ADN,the nodes with similar voltage change are divided into one region by clustering algorithm.In the area with microgrid,the similarity of node voltage variation indirectly represents the proximity of entry point and other nodes in the area.By adjusting the power injected by microgrid to points of common connection(PCC),the voltage regulation effect can be produced on the nodes close to PCC point,which shows the feasibility of microgrid participating in ADN voltage regulation.In view of the fact that microgrid and ADN belong to two different stakeholders,in order to take into account the operation economy of microgrid and the voltage regulation demand of ADN,a multi-objective day-ahead optimal dispatching model of ADN considering the role of micro grid voltage regulation is established.Different from previous studies,micro grid is not only applied as a controllable power source installed at PCC point in ADN,which is controlled according to the voltage regulation demand of the ADN.In addition,the dispatching economy of each micro source under the condition of load change in microgrid is considered,and the power interaction between microgrid and ADN is determined by the power balance and operation cost in microgrid during the optimization period.At this time,the micro grid can be the controllable power source or the load at PCC point providing power to the ADN.Therefore,the solution of the optimal dispatching model can not only provide the power dispatching plan at PCC point to meet the demand of distribution network voltage regulation,but also provide the micro source power dispatching plan to meet the operation economy of micro grid,which matchs the actual operation of micro grid in ADN.Considering that the micro grids’ participating in the ADN voltage regulation involves the coordination and optimization of the micro grid voltage regulation and other voltage regulation equipment in ADN,the reactive power optimization collaborative allocation model of the ADN considering the micro grid voltage regulation is established.The characteristics of this paper is that the voltage regulating equipment in the ADN not only coordinates with both the variable load and the power interaction between the microgrid and the ADN.Based on the day-ahead power scheduling scheme of PCC and load real-time data,the coordination among reactive devices with different response rates is adjusted in real time with 5min as the optimization time granularity.At the same time of improving the comprehensive control level of regional voltage,we can take advantage of the good voltage regulation capacity of microgrid to reduce the construction cost of high-performance voltage regulation device in ADN.This paper shows the potential of micro grid voltage support for ADN,and the coordination between micro grid voltage regulation and reactive power compensation in ADN is realized,which effectively improves the comprehensive control level of regional voltage.The model and method proposed in this paper provide a basic idea and scheme for the research and application of voltage regulation abiliity of microgrid for ADN. |
PDF Full Text Request