Research On Power Control Strategy Of DC Distribution Network With High Proportion Of Distributed Photovoltaics

Compared with the AC distribution network,the DC distribution network has greater advantages in system transmission,additional losses,access to distributed energy,and power quality.At present,research on key equipment and system protection in the DC distribution network needs to be further studied,especially the problem of access to new energy in the DC distribution network.This paper conducts research on the power control strategy of the DC distribution network with a high proportion of distributed photovoltaics,focusing on the DC distribution topology problem and related power control strategies after the high proportion of distributed photovoltaics are connected to the grid.The main contents are:(1)A typical topology study with a high proportion of distributed photovoltaic DC distribution network.Analyzed and studied different types of topology in the current DC distribution network,including radial topology,end.to.end topology and ring topology.Aiming at the current control mode of the voltage source converter,a double closed.loop decoupling control method is adopted.The outer loop adjusts the power and the inner loop adjusts the current,which can better support the control of the DC distribution network.For the control requirements of photovoltaic,energy storage and load in DC distribution networks with high proportion of photovoltaics,attention needs to be paid to the equivalent circuit in photovoltaics,the maximum power algorithm and the control structure of boost converter,as well as the characteristics of the battery and DC.The control method of the DC bidirectional converter and the control method of the load port converter,and based on this,a typical simplified topology with a high proportion of distributed photovoltaic DC distribution network is proposed.(2)Research on optimization strategy of photovoltaic power generation capacity of DC distribution network.In view of the technical optimization of the operation in the DC distribution network,by establishing a model of the photovoltaic module connected to the DC distribution network,a capacity optimization strategy for the photovoltaic module and the converter station is proposed in the DC distribution network.Using time series as input,the operation mode of photovoltaic modules and energy storage modules in the DC distribution network is optimized on the basis of time series production simulation,and finally the optimal capacity and power generation capacity of the photovoltaic module are obtained.(3)Research on grid / source / storage interactive power control strategy with high proportion of distributed photovoltaic DC distribution network considering energy storage.An improved deviation slope coordinated control method is proposed.The master and slave converter stations respectively adopt constant voltage control with margin and improved voltage deviation droop control mode.While performing power adjustment,they can largely to reduce the problem of voltage deviation,the improved deviation slope control method can ensure that the power balance of the system can be maintained every time the power changes.For the steady.state situation,the coordinated operation of the system power on both sides of the converter and the single converter alone is studied separately,and the power balance is adjusted specifically for various transient conditions of the DC distribution network.Comparing the traditional deviation slope control method with the improved deviation slope control method,the proposed control strategy can maintain the stability of the DC distribution network in both steady state and transient state,and at the same time verifies the effectiveness of the control method.