Research On Model And Algorithm Of Powel Flow Calculation In DC Distribution Network

With the rapid growth of economy and the development of new energy technology, the load density increases, and the urban AC distribution network is faced with the problem of insufficient power supply capability and the access of distributed generation, and is not suited to the load and urban development. The DC distribution network is different from the AC distribution network in many aspects, such as power supply capacity, line losses, and the adaptability for all kinds of power and load access, which makes it a good prospect.The power flow model and algorithm of DC distribution network is studied in this paper. The DC distribution network is suitable for the access of all kinds of distributed generation. The principle of five common distributed generations is analyzed, and the power flow models are established. For the electric converters in DC distribution network, the appropriate topologies are chosen. With the loss of switches, transformers, and nonlinear inductor and capacitor taken into consideration, and the loss analyzed when the switches are off and on based on certain assumptions, the non-ideal power flow models of AC-DC, DC-AC and DC-DC converters are established according to energy conservation principle.The buses are reclassified according to the characteristics of DC distribution network, and the improved Newton-Raphson method is proposed to calculate the power flow. For AC-DC and DC-AC converter, when the AC side is controlled, an inside iteration is nested in the outside iteration, and the equation for each converter is established according to the converter power flow model to get the state variables needed in outside iteration. For the DC-DC converter, when under constant voltage control, combine the end power with the parameters in power flow model to correct duty cycle in each iteration.The cases are structured and calculated in MATLAB, while the simulation models are built in PSCAD. The results from MATLAB and PSCAD are compared and the errors are analyzed to show the rationality and effectiveness of the proposed model and algorithm in DC distribution network.