Multi-objective Coordinated Control For MV And LV Distribution Networks Adapting To PV And Energy Storage Units

In recent years,in order to solve the imbalance between energy supply and demand and the contradiction and conflict between economic development and environmental protection,distributed photovoltaic technology has been rapidly developed and widely used,and the number of household photovoltaic grid connection is increasing.The intensity of solar radiation,the temperature of the photovoltaic power generation device,and the environmental customs of the site will all have an impact on the PV output,making it significantly random and volatile,increasing the uncertainty of the distribution network system operation.Distributed energy storage technology can be an important way of regulating the efficient and stable operation of the distribution network by reasonably regulating the charging and discharging power of the energy storage to achieve peak and valley reduction,thus effectively reducing the impact of node voltage fluctuations caused by distributed PV grid connection.At the same time,the medium voltage and low voltage layers of the distribution network are different in terms of communication conditions,computing power,network architecture,optimisation objectives and controllable units,so it is necessary to combine the characteristics of different layers to choose the appropriate regulation method.This paper investigates the optimal control of low-and medium-voltage distribution networks for high proportion distributed photovoltaic and energy storage system access,as follows.Firstly,this paper illustrates the control theory basis for optimising the network loss and node voltage of the MV and LV layers of the distribution network by regulating the grid-connected power of distributed PV,analyses the mechanism of regulating the grid-connected power of the energy storage system on the network loss and voltage of the LV layer of the distribution network,and illustrates the control theory basis for optimising the matching degree of source and load storage in the LV layer and reducing the network loss and node voltage fluctuations by regulating the charging and discharging state and power of the energy storage.The control theoretical basis of the study.The second part addresses the problems of increased network loss,significant node voltage fluctuations,low PV consumption rate and poor source-load-storage matching after PV plants are integrated into the medium-voltage distribution network and distributed photovoltaic storage systems are integrated into the low-voltage distribution network,taking into account the network architecture of the medium-voltage and low-voltage layers of the distribution network,computing capability,communication conditions,characteristics of adjustable components and time scales,etc.,and establishes a centralised and distributed control model for the medium-voltage and low-voltage layers of the distribution network.The centralized and distributed optimal control model for the MV and LV layers of the distribution network is established,and the regulation commands are solved and delivered to the corresponding nodes to achieve the optimal control objectives.Finally,a centralised medium-voltage-distributed low-voltage co-ordinated control strategy is proposed for the global distribution network.The control strategy is selected according to local conditions,and the signal transmission and time scale matching are completed between different voltage levels to realise the power command transmission from the medium-voltage layer to each node,and the response of the low-voltage layer to the power command of the medium-voltage layer,thus completing the co-ordinated control of the medium-voltage and low-voltage layers of the distribution network.