Coordinated Voltage Control Method And Technology Of Active Distribution Networks

The goal of peaking carbon dioxide emissions and achieving carbon neutrality as well as the strategy of constructing the photovoltaic(PV)in the entire county lead to a larger scale of gridconnection of the distributed energy resources(DERs),as a result,traditional distribution networks have gradually evolved into the active distribution networks(ADN).However,the peak behavior and intermittency of the DERs will derive over/under voltage issues in a period of time,moreover,the randomness and fluctuation of the DERs can also cause voltage fluctuation and voltage increment issues frequently.Therefore,the broad and dispersed voltage issues have become a regular phenomenon in the ADN,which brings great economic loss for power consumers and even endangers the stable operation of the distribution networks.However,the traditional decentralized control not only needs a large number of control devices,but also captures a low efficiency due to the lack of matching relationship between the diverse voltage control devices and the critical voltage pollution sources in terms of spatial location,control function,and controllable capacity.Therefore,how to effectively solve the voltage issues has become one of the urgent problems to be solved in the ADN under the background of carbon-peaking and carbon-neutrality.Moreover,it is a challenging scientific problem to improve the efficiency of voltage regulation by virtue of the intelligent matching and coordinated control of the diverse voltage control devices.In view of the challenges mentioned above,this thesis considers the different performance of the voltage issues in the important components of ADN,which involves autonomous microgrids,multimicrogrid systems,incremental distribution networks,and regional distribution networks.Furthermore,focusing on the practical engineering requirements of these typical scenarios and based on the networked control and coordinated control,the following control theories and methods are proposed systematically: voltage security control for autonomous microgrids,voltage coordinated control for multi-microgrid systems considering different voltage quality requirements,cloud-based coordinated voltage control for incremental distribution networks,and source-grid-load cooperative voltage regulation in regional distribution networks.The main contributions of this thesis are as follows:1)Voltage security control for autonomous microgrids based on the event-triggered operation mode switching of DERs: Considering that the bus voltage can only be maintained by the inside controllable units in autonomous microgrids,first,a hierarchical control architecture is constructed by virtue of the two-level agents,which establishes the interaction mode of the DERs.Second,the online optimal matching relationship of the DER’s operation mode is analyzed,where the mode switching can be triggered by the voltage security events.Then,the operation mode switching control strategy of the DERs is proposed,which realizes online matching and fast reconstruction of the inside controllable units in autonomous microgrids.On this basis,a dynamic economic dispatch is proposed by taking into consideration of the operation mode switching of the DERs,such that the voltage security can be guaranteed by minimizing the operation costs.Finally,a model-predictive-control power tracking method is presented based on the dynamic model of the DER inverters,which effectively improves the dynamic performance of the inverters.2)Voltage coordinated control considering different voltage quality requirements of multimicrogrid systems: Taking into consideration of the different bus voltage quality requirements in multi-microgrid systems,first,the distributed voltage coordinated control architecture is constructed based on the multi-agent system,which derives the interaction mechanism between different submicrogrids.Second,the relationship between the system voltage and the power output of each submicrogrid is analyzed by means of the power flow sensitivity.Besides,the voltage regulation method for multi-microgrid systems based on the distribution model predictive control is proposed,which takes into account the economy and rapidity during the regulation process considering the different voltage quality requirements of each sub-microgrid.Finally,the effectiveness of the proposed method is validated by the simulation results,and some practical engineering applications are attempted by building a multi-inverter platform in the campus laboratory.3)Economic-driven coordinated voltage control of incremental distribution networks based on the cloud: Considering that the incremental distribution networks can be controlled with the help of the cloud,first,a cloud-edge collaborative control architecture is proposed,which involves the voltage control and economic operation of incremental distribution networks.Thus the voltage control issues can be solved by all the DGs in an ‘active’ mode with the support of the cloud.Second,a multi-objective optimization model including the operating cost of DGs and network power loss is established,which effectively improves the system economy and the consumption of DGs on the premise of ensuring system voltage safety.In addition,to deal with the delay effect of the communication network,a delay compensation mechanism considering the imprecise of prediction model is proposed,which guarantees the effective implementation of the proposed method based on the cloud-edge collaborative architecture.4)Source-grid-load cooperative voltage regulation in ADN with high penetration of RES:First,a hybrid voltage control architecture of ADN is proposed considering the operation characteristics of source-grid-load voltage regulation devices,which contains different time scales and different control modes.Second,in order to solve the global long-term voltage issues,a multimode switching control method of the on-load tap changers triggered by the voltage security events is proposed,thus the service life can be enhanced by effectively reducing the number of tap changes.Besides,a multi-objective optimization model is established considering the network power loss and operation cost,which further improves the power quality of the whole system.Finally,to solve the local transient voltage issues including over/under voltage and voltage increment issues,a sourceload distributed cooperative voltage control method is proposed,which guarantees the control effectiveness and efficiency by virtue of coordinated interaction among the source-load voltage regulation devices.