Study On Coordinated Control Strategy Of Multi-zone Active Distribution Networks

As the penetration of distributed generations(DGs)grow in distribution networks,the characteristic of a distribution network is becoming similar to an active transmission network,which is called active distribution network(ADN).The implementation of DGs in ADNs promises many benefits,such as power loss reduction,improve energy efficiency and environmental quality.However,the output of DGs,especially renewables,are prone to intermittency,randomness and uncertainty,which will have bad influence on power flow distribution and power quality if there are no reasonable controls.Therefore,traditional voltage control methods are required to be improved or even fundamentally changed.This paper studies on the economic operation and voltage control of ADNs containing multiple zones by considering the change of the ownerships in the process of electric market reform and the coordination between DGs and the traditional voltage regulators respectively.The proposed coordinated control strategy adapts to the development of the distribution network to ensure the economy and stable operation of ADNs.Firstly,based on the background of global energy transformation and the large-scale development of DGs,this paper summarizes the general situation of ADNs,zoning method of ADN and coordinated control strategy of ADN,and introduces the research status of the coordinated control strategy of multi-zone ADNs in detail.Secondly,this paper adopts the rule-based zoning method combining the background of electric marketization to clarify the zoning form,as the reasonable architecture of ADNs.According to the drawbacks and limitations of existing researches on coordinated control strategy,this paper analysis the characteristics of the two typical control objectives of the distribution networks,such as economic optimization and voltage control.the paper depicts strategy and the cooperative control framework of the coordinated control considering economy and regulating speed respectively.Then,this paper studies on the characteristics of DGs and establishes local collaborative performance model to reflect the local interests.The collaborative performance model mainly includes the adjustable range,cooperation cost.Based on the distributed model predictive control theory,this paper formulates the coordinated control model aiming to minimize the power loss during electric transmission and minimize the zones' cost at the same time for economic operation of ADNs.The implementation process of the strategy is given.At last,the rationality of the proposed cooperation cost is validated,and the strategy is feasible in a ADN containing three zones.Finally,considering the zones contain various controllable devices,the regulation performances of which are different.This paper proposes a regulating speed model to reflect the local adjustment speed of each zone.Furthermore,a distributed coordinated voltage control strategy based on distributed model predictive control theory is studied.The weight setting rules of adjusting speed under different voltage limits and the prediction model of output variables with different regulating speed are studied respectively in the initial value calculation and iterative solution of distributed control.At last,a numerical simulation is carried out under two different voltage exceeding level to verify the correctness and validity of the proposed strategy.