For effective aggregation and equivalence of distribution network containing different control types of distributed photovoltaic systems,a generalized composite load model and a two-stage model parameter aggregation and equivalent method considering grid-following and grid-forming distributed photovoltaic systems are proposed. The generalized composite load model is formed by paralleling the equivalent models of grid-following and grid-forming photovoltaic systems with the traditional composite load models to effectively fit the grid-connected characteristic of the actual distribution network. Based on the parameter sensitivity analysis and the improved differential evolution algorithm,the model parameters are determined by the aggregation and equivalence,which avoids the disadvantage of large dispersibility of identification solutions caused by too many unknown model parameters. The self-description ability,generalization ability and parameter stability of the proposed model are verified based on PSCAD and MATLAB.

In order to solve the stability problem caused by the interaction between the inverter side and the grid side when a large number of distributed grid-connected inverters are connected to the public grid, the frequency domain fitting method is introduced into the analysis of new power system in this paper. In this paper, the frequency domain fitting method of transfer function is introduced firstly, and then the process of generating system equations required by the method when the system contains control and nonlinear parts is demonstrated by taking a single grid-connected inverter closed-loop system as an example. In this method, the transfer function of the grid-connected inverter under any given input and output can be obtained only by the topology structure information and control strategy information of the grid-connected inverter. The frequency domain fitting method effectively avoids the tedious problem of deriving the equivalent output impedance manually for the stability analysis of power electronic converters under different topologies and control strategies. This method can fit the topology and control strategy of the new grid-connected inverter effectively in frequency domain.

Modern power system because of its high voltage, high power characteristics, makes the hardware experiment with certain safety risk and grid security risks. As a more complex simulation method, digital twins are more extensive in time scale compared with the traditional power system simulation, and more frequent in data interaction with the real system. Digital twins can be applied in power systems in a variety of ways. But at present, the application of digital twin still stays on the application of the whole product life cycle. This paper proposes a new real-time interactive power system simulation architecture based on the digital twin, and set up an electric power system based on SoC platform of digital twin, PL part has set up a twin body for the electric power system, the PS part compare the difference between the twin body and the actual body and then modify the twin body. It also provides the control part which is consistent with the hardware control logic. The platform is lightweight, economical, heterogeneous and compatible with a variety of computing tasks, rich interfaces and strong expansibility. This paper provides a framework for the application of digital twins in power system and provides the platform with rich application value.