Assessment Method of Regional Equivalent Inertia of New Energy Power System Based on Measured Data

The high proportion of new energy connected to the grid makes the problem of low inertia of the power system increasingly prominent, and the frequency problem more frequency problem is more serious. In order to improve the stable operation ability of the new energy power system, it is necessary to evaluate the level of system inertia and analyze the influence of new energy power generation type, permeability and virtual inertia control mode on the real-time inertia of the system At present, the most widely used evaluation methods have the problem of a large number of measurement data and difficulty in obtaining them. The evaluation accuracy is affected by the selection of frequency sampling points, measurement devices, and the processing methods of measurement data. To address these issues, this paper proposes a method for assessing the regional equivalent inertia of new energy system based on measured data. The active power, frequency, and voltage data are used to accurately calculate the inertia, measurement data are few and easy to obtain, which reduces the data processing steps and is still applicable when the internal parameters of the new energy units are unknown. Firstly, the virtual inertia response characteristics of wind power and photovoltaic power and their influence on the frequency stability of the system are analyzed. Secondly, on the basis of analyzing the principle of regional equivalent inertia assessment, the expression of regional equivalent inertia of new energy system is derived by considering the load voltage characteristics. Finally, in order to reduce the error caused by the frequency distribution characteristics, the selection of sampling points and the calculation method of regional frequency are proposed from the perspective of weighted average. Sampling points are determined according to the real-time inertia monitoring results of the SCADA system, which saves the installation cost of PMUs (phasor measurement units) and avoids large amount of calculations. In addition, the low-pass filter and sliding window technology are used to process the measurement data, which improves the accuracy of the inertia assessment results. The simulation results show that the proposed method can accurately assess the regional equivalent inertia of both traditional and new energy power system. Wind power system with additional frequency control can provide virtual inertia much larger than the actual inertia, but due to the limitation of actual speed and output, its virtual inertia response time is short, and the support power can be limited. The virtual inertia response time of the PV system controlled by VSG (virtual synchronous generators) is fast, and can provide support power according to the dispatching needs, but it needs to be equipped with large energy storage devices. The following conclusions can be drawn from the simulation analysis: (1) Changing the new energy output and virtual inertia control parameters will cause a change in the equivalent inertia and results. (2) The PV virtual inertia control using VSG has a long response time, more flexible output, and better frequency regulation effect, but it requires large-capacity energy storage, the economic benefits are not good. The wind power system with additional frequency control does not need energy storage, and the primary investment is small, but with the recovery of rotor speed, it is possible to cause a secondary reduction in system frequency. (3) From the perspective of technical economy, when the system inertia is insufficient, the power support brought by dispatching means should be considered first, if new energy power is used to provide power support, priority should be given to the use of wind turbine rotor kinetic energy control, when the actual output and rotor speed do not meet the requirements, then consider the configuration of energy storage for photovoltaic or wind turbine. Therefore, how to balance the economy and the output of new energy is a problem that needs further research. © 2024 China Machine Press. All rights reserved.