Theory And Method Of Multi-rate Parallel Simulation Of Electromagnetic Transients In Complex Active Distribution Networks

As new clean energy sources such as wind power generation and distributed photovoltaic power generation,as well as new loads and energy storage such as electric vehicle integrated services and distributed energy storage,have been introduced into the distribution network on a large scale,the operation mode of the distribution network has changed from the traditional power tracking load operation mode to an active distribution network "source-grid-load-storage" model,with more coordination and flexible interaction.At this time,the distribution network has gradually presented the characteristics of a "multi-time scale and wide frequency domain",and its dynamic process is significantly different from that of the traditional distribution network.Therefore,considering that the traditional power system simulation tools are mainly used to simulate the AC system,they cannot efficiently and accurately simulate the dynamic process of the highfrequency power electronic devices in the active distribution network on a smaller time scale.In addition,the high efficiency of multi-rate parallel simulation of power systems based on the idea of parallel computing has been verified in many studies,and it provides an effective method for the simulation of large-scale power systems.Based on the above analysis,this paper will start from the traditional digital simulation method of power system,take the currently active distribution network as the research object,and study the electromagnetic transient parallel simulation method that meets the actual operating conditions of the active distribution network.The main research content,the related results,and conclusions are as follows:(1)Research on active distribution networks’ parallel simulation segmentation strategy.The study analyzes the principle and purpose of three network partition strategies,regarding the early power system partition method,the network partition method based on the eigenvalues of the state space matrix,and the parallel computing efficiency based on the segmentation strategy.Besides,the study comprehensively evaluation the index of network partition effectiveness for equilibrium degree,calculation accuracy,and numerical stability.In addition,the simulation example based on the IEEE-13 node test feeder directly reflects the application value of the proposed sub-network evaluation index.(2)Research the decoupling method of active distribution networks.By comparing the two network equation decoupling methods: the power system network equivalent method and the transmission line model decoupling method,the study proposes a network decoupling method based on distributed parameter line model applied to distribution network lines.In addition,by analyzing the limitations of the well-developed Bergeron model in the distribution network scenario,an improved line model based on the segmented transmission delay idea is proposed,which effectively improves the network decoupling accuracy.Finally,a simulation example based on the IEEE-34 node test feeder successfully verifies the validity of the line model proposed in the work.(3)Research on multi-rate data interaction interface and multi-rate parallel simulation method.The study firstly analyzes the advantages and disadvantages of serial,parallel,and iterative interaction sequences in the data interaction interface for parallel simulation.In addition,given the low degree of parallelism in typical simulation architectures,a multi-subsystem synchronization coordination method with higher efficiency is developed,which effectively improves the parallelism of parallel simulations.Subsequently,for the data interpolation problem of the multi-rate interface,the study proposes an improved linear interpolation method applied to the parallel simulation data interaction interface by analyzing the error generation mechanism of the linear interpolation method in the process of simulating higher harmonics.Finally,a simulation example based on the IEEE-123 node test feeder successfully verifies the effectiveness of the multi-rate parallel simulation method proposed in the study.