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The current study aims to examine the longitudinal impact of the sense of control over COVID-19 infection on mental health and substance use. According to the stress process model (Pearlin & Schooler, 1978), self-concept factors are conceptualized as mechanisms through which stressors, in this case, risk of COVID-19 infection, impact mental health (Reed-Fitzke, 2020). Victimized individuals often respond to these self-concept factors (e.g., a diminished sense of mastery and control) with avoidance coping behaviors (e.g., substance use).

Full power converter wind turbine is the main type of wind power, so the simulation calculation needs to establish accurate model parameters. This paper analyzes the model structure of PSASP program according to its low voltage ride through control and physical characteristics, and puts forward the parameter identification method of LVRT characteristics of full power converter wind turbine, and to use the LVRT data of 5. 5MW unit for parameter identification and simulation verification. This paper proposes that the electromechanical transient simulation can ignore the part of the generator model of the full power converter wind turbine, and simulates the grid side converter with the controlled current source. The main characteristics of LVRT are determined by the control system of the converter. In order to do the parameter identification, it is necessary to calculate and analyze the control characteristics of multiple measured data. First, determine the control mode, then determine the control parameters to complete the parameter identification. In this paper, the modeling conditions and model structure of the full power converter wind turbine are confirmed. The correlation between the parameters during the LVRT fault and the parameters during the LVRT recovery period and the LVRT characteristics is analyzed. In this paper, a parameter identification method is proposed to analyze the active current and reactive current during the LVRT fault, which has strong physical significance and operability. Based on the actual LVRT characteristics of 5. 5MW wind turbine, the parameter identification and simulation are carried out to verify the correctness of the method.

Due to the increase of the proportion of nuclear power unit capacity in the power grid, the simulation analysis of the PWR nuclear power unit is increasingly important for power grid stability analysis, which is regarded as one of the important parts of China’s nuclear power unit. The original mathematical model of the PWR nuclear power unit is very complex and not suitable for the stable calculation and actual measurement modeling of the power grid. Based on the actual modeling of conventional islands, a simplified simulation model of the nuclear island is proposed in this paper and is conducted the actual modeling test of nuclear islands and conventional islands at the NINGDE Nuclear Power Station and FUQING Nuclear Power Station in Fujian Province. In the load test, the models and parameters of the nuclear reactor control system, temperature control circuit, steam generator, speed control system, actuator, and steam turbine were measured. The nuclear island uses the mathematical model built by MATLAB in conjunction with PSD-BPA software for simulation verification. The simulation results can truly reflect the dynamic characteristics of the nuclear islands and conventional islands of PWR nuclear power units, providing mathematical models and parameters for grid stability calculations, which can be used for dispatching safety and stability calculations.

Power and Load Unbalance protection (PLU protection) is one of major turbine protections to preventing steam turbine overspeed. The start condition is that if unbalance of mechanical power and electrical power exceeds the limitation, the PLU protection will be actuated to close the valves but not stop the generators. But the accidents have happened and power grid simulation show that the grid faults may make the PLU protection false trip, that maybe turn the valves on and off frequently, seriously, it may even create power oscillation. In order to solve this problem, the generator rotating speed constraint is introduced into the PLU protection and the simulation model is established in this paper. The setting method of rotating speed constraint parameter is proposed. The simulation results verify that this method can effectively prevent the PLU false trip and improve the reliability of PLU protection.

The double-fed inductor generator (DFIG) is one important type of wind generator. Because of high percentage of wind energy, it is necessary to build accurate wind generator model and parameters for power system electro-mechanic simulation. The paper mainly presents the simulation model and parameter identification method of DFIG type wind generators. For power system transient simulation, the characteristic related to low voltage ride-through (LVRT) is most important, and the model related to LVRT is mainly presented. The parameters of the model are divided into three types and use different identification method. The identification method of important parameters is mainly presented. One actual wind generator is used as an example to explain the identification process and testify the validity of the model.

This paper presents an investigation on the mechanism of the impact of the governor control on power system dynamics, and an introduction of boundary frequency. The well-known Hefferon-Phllips math model has been extended to include the math model of the turbine and its governor. By using this model the impact can be divided into the synchronizing and the damping torques. Based on the analysis of the frequency response, a new concept of the boundary frequency has been drawn out and that provides a performance index in characterizing the nature of the turbine and its governor in system dynamics. The damping provided by governor will be opposite in polarity, if the oscillation frequencies are located in different sides of the boundary frequency. This study also provides the values of the boundary frequencies for thermal and hydro generators under different control input signals ΔΩ or ΔP E . Study has also been conducted for input signals ΔΩ and ΔP E .

The influence of tie-line reactance on damping of inter-area oscillation mode is studied. The phenomenon of the inter-area mode damping ratio decreasing when inter-connection is strengthened is proposed. Main interconnected grids in China are tested by calculating sensitivity of eigenvalue to tie-line reactance, including Chuanyu-Mid China Grids, Northeast-North Grids, North-Mid Grids and Fujian-East Grids. A two- area system is constructed for further investigation. The study shows there is no strict linear relationship between tie-line reactance and damping of inter-area oscillation mode. For a large-scale system, the power transferred of which is comparatively small, it is possible that damping of inter-area mode decreases as tie-line reactance decreases, which is opposite to the commonly accepted opinion. Although the phenomenon is comparatively rare, it should be carefully paid attention to considering its strong influence under some critical stage. These tests also demonstrate that reinforcement of the conection between two bulk power grids is an effective way to mitigate oscillations in systems.