Based on the time series production simulation, the new energy consumption capacity of the target power grid is analyzed by comprehensively considering carbon emission, power abandonment cost, comprehensive benefit and other factors, and suggestions are provided for the new energy installation planning of the power grid and the reasonable utilization rate improvement of new energy.

New energy power system time series production simulation (see Figure 1), with the goal of maximum new energy generation or minimum comprehensive system cost, and comprehensive consideration of system balance, grid security, reserve, power, unit operation. The mathematical model is established under the constraint conditions such as connection line exchange plan, maintenance plan, new energy power prediction curve, system load prediction curve, bus load prediction curve, network topology, generating capacity of units, and power plant operation. By optimizing the solution model, the output plan of conventional units and new energy is obtained, especially the evaluation result of new energy consumption capacity.

FIG. 1 Schematic diagram of time series production simulation of new energy power system

The application of time series production simulation in power system can be traced back to the 1970s. Westinghouse Electric Company in the United States realized the economic optimization calculation for the operation of photovoltaic power plants with the goal of minimum cost. In the late 1990s, power companies and research institutes in the Baltic Sea region jointly developed a mathematical model based on mixed integer linear programming for hour-level simulation of power system production, which was subsequently widely used in Europe.

In China, the production simulation research of interconnected power system has been carried out since 1980s. In view of the urgent problems faced by China's new energy consumption assessment, China Electric Power Research Institute Co., Ltd. proposed a new energy annual consumption assessment method based on time-series production simulation, established a time-series production simulation model of new energy power system considering the constraints related to power system operation, and adopted mixed integer linear programming method to solve the model. The new energy production simulation system has been developed, and annual and quarterly consumption capacity assessment and early warning have been carried out on a rolling basis, based on which the installation timing and major maintenance arrangements have been optimized, and has been applied to 27 power grids above the provincial level.

In the future, with the application of various forms of energy storage in the power system, the load characteristics brought by electric vehicles, adjustable loads, interruptible loads, etc., will have subversive changes; The power system is larger and more complex, so it needs more perfect and refined power supply model, load model, energy storage model and grid model. With the advancement of power market reform, power trading results become an important part of power generation plan, and the structure and dispatching operation ideas of power grid will also change. Therefore, attention should be paid to the simulation and application of power market and power trading results.

The new power system has the characteristics of "double high" with high proportion of new energy and high proportion of power electronic equipment, and its safety and stability mechanism and characteristics have great changes compared with the traditional power system. Analyzing the stability mechanism of the "double high" system, extracting quantitative evaluation indicators, and proposing the minimum boundary conditions for future system construction, so as to quantify the technical requirements of frequency support and voltage support of new energy, plays a key role in ensuring the construction and safe and stable operation of the new power system.

At present, the cognition of different stability forms such as power Angle stability, voltage stability and frequency stability of traditional power systems has been formed, covering stability mechanism, instability performance and key influencing factors. However, the understanding of the stability mechanism of the new power system, such as the instability form and the key influencing factors, is not sufficient, and the identification method of the dominant instability form has not been established. The construction conditions of the new power system and its quantitative analysis method are not yet clear. The system based on high proportion of new energy and converters has insufficient quantification of the demand for frequency and voltage support of new energy, and the boundary conditions for the construction and operation of the corresponding system are lacking. Although some institutions have proposed evaluation indexes such as short-circuit ratio and system inertia for the stability of "double-high" power systems, a unified quantitative analysis system of stability mechanism, frequency support and voltage support has not yet been formed.

Based on the dynamic interaction mechanism between power electronic equipment and system, multi-equipment, and equipment and generator, the leading dynamic process of instability after large/small disturbance is studied, and the large/small disturbance instability form of new power system is found. It is a developing trend to study the stability region estimation and stability boundary characteristics of new power systems.

In the new power system frequency support analysis and quantitative evaluation technology, the establishment and improvement of the system frequency response model considering the characteristics of hydropower and thermal power units is the development direction of the moment of inertia online monitoring and evaluation technology. With the continuous increase of the proportion of new energy, the quantitative relationship between the demand for moment of inertia and the penetration rate of new energy needs to be studied.

In terms of voltage support analysis and quantitative evaluation technology of new power system, the short-circuit ratio calculation process of new energy multi-station needs to introduce the voltage control model of new energy unit, the static reactive power compensator model, and the static reactive power generator model, which reflects the influence of different types of power electronic equipment on the short-circuit current contribution. It is also urgent to study the relationship between short-circuit ratio of new energy multi-station and other voltage support evaluation indexes, as well as multi-dimensional power grid voltage strength evaluation indexes.

There are complex interactions between a variety of power electronic equipment and traditional power generation and transmission equipment in new power systems. As the proportion of new energy and power electronic equipment continues to increase, multi-frequency oscillations such as ultra-low frequency, low frequency, sub-synchronous and high frequency may occur among power electronic equipment, traditional equipment and AC network, and there are technical requirements for oscillation analysis and suppression.

At present, the analysis and suppression technologies of low frequency/ultra-low frequency oscillation and sub-synchronous oscillation of turbine units are relatively mature, while sub-synchronous oscillation and high-frequency oscillation caused by new energy and flexible DC are still in the research stage. The state space method and impedance method are proposed and used in the research of oscillation mechanism, but the quantitative evaluation technology of oscillation risk is not mature. Some methods of vibration suppression such as parameter optimization and additional damping control are proposed, but their application in engineering is insufficient. In some areas of China, the secondary/supersynchronous oscillation caused by large-scale wind power access leads to torsional vibration of turbine shafting in the near area. Based on the state space method and impedance method, the oscillation mechanism is defined, and the fan parameter optimization measures are taken to effectively alleviate the oscillation. In the future, the quantitative analysis based on fine simulation and online analysis of early warning, and the suppression based on wide-band damping control will be the main direction to deal with the problem of all-band oscillation.