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A solar heat pump heating system with an aluminum tubular collector is proposed in this paper. Mathematical models are established for solar energy absorption and air energy absorption of the aluminum tubular collector, as well as the heat-absorption coefficient of the working substance. The electronic expansion valve is controlled via the fuzzy PID method to adjust the working substance flow rate, as well as to control the evaporator overheating and set the indoor heating temperature. TRNSYS is used to analyze the effects of the wind speed, solar radiation amount, environment temperature, and working substance flow rate on the heat transfer performance of the aluminum tubular collector. The results indicate that the heat transfer performance of the aluminum tubular collector is significantly affected not only by the solar radiation but also the wind speed. For wind speed > 2 m/s, the absorbed power of the collector increases rapidly with an increase in the wind speed; when the working-medium flow rate reaches 4 m/s, the collector absorption power tends to be saturated. Subsequently, an experimental heating system with a heating area of 170 m2 is constructed. Experiments revealed that the maximum coefficient of performance (COP) of the heating system is 4.46, and the average COP value is 3.95, indicating good heating effect.

Flywheel energy storage technology has attracted more and more attention in the energy storage industry due to its high energy density, fast charge and discharge speed, long service life, clean and pollution-free characteristics. It is wwidely used in uninterruptible power system, grid frequency modulation, energy recovery and reuse and other fields. With the development of flywheel rotor materials, motors, bearings and control technology, flywheel energy storage technology has been greatly developed. Introducing the basic structure of the flywheel energy storage system in the above three applications. Typical charge-discharge control strategies are given for the three sensor-less algorithms of model reference adaptive control, sliding mode observer andextended Kalman filter, which are suitable for flywheel energy storage devices.

Background HIV/AIDS is an issue that seriously endangers public health. With the implementation of social support policies for people living with HIV/AIDS, although the mortality of them has decreased significantly, their survival is still a big concern. Objective To understand the quality of life and influencing factors in people living with HIV/AIDS in Henan rural areas. Methods By use of cluster sampling, we selected the persons living with HIV/AIDS treated by highly active antiretroviral therapy (HAART) who were managed by the local center for disease control and prevention in a rural area of Henan from June 3 to June 12, 2020. We collected their general data and laboratory test findings, and assessed their quality of life using the Chinese version of the WHOQOL-HIV BREF. We used multiple linear regression to identify the associated factors of quality of life. Results A total of 415 cases attended the questionnaire survey, and 400 of them (96.39%) who effectively completed the questionnaire were finally included for analysis. All the respondents were Han people, most of them were diagnosed over eight years, males, and aged over 50 years, and had a spouse, no stable income, low education level and CD4+ T lymphocytes greater than 500/μl with transmission mainly through blood, and over eight years of continuous HAART. The total score of quality of life of the respondents differed by sex, age, education level, marital status, income status, route of getting HIV infection, time of HIV diagnosis, and continuous treatment duration of HAART (P

This study addresses speed sensor aging and electrical parameter variations caused by prolonged operation and environmental factors in flywheel energy storage systems (FESSs). A model reference adaptive system (MRAS) flywheel speed observer with parameter identification capabilities is proposed to replace traditional speed sensors. The proposed method uses reference and adjustable models to identify the stator resistance and permanent magnet flux (PM Flux) to mitigate the adverse effects of electrical parameter changes on control performance. The Tent chaotic mapping-improved Sparrow Search Algorithm (SSA) optimizes the Proportional-Integral (PI) controller parameters for the dual closed-loop and MRAS speed adaptation laws of the flywheel motor. Moreover, a self-switching parameter identification (SSPI) scheme, which constructs a cost function based on the current, parameter identification, and speed errors, is proposed to prevent inaccuracies in parameter identification. The MRAS observer selects the appropriate PI adaptive mechanism based on the error values, thereby enhancing identification accuracy. Simulink simulations show significant improvements in the rapidity and accuracy of the Tent-SSA optimized MRAS flywheel speed observer, enhancing the stability and robustness of the flywheel rotor. Experimental validation on a constructed FESS platform confirms the feasibility of this method. [ABSTRACT FROM AUTHOR]

In the process of accessing distributed power sources in microgrid, there will be serious coupling between active power and reactive power, which will lead to significant changes in the inverter outlet voltage and impedance and increase the circulating current phenomenon. The generation of circulating current will accelerate the aging of devices, reduce the inverter efficiency, and threaten the stable operation of the system. In this paper, the mechanism of circulating current generation is analysed, the basic characteristics of circulating current are studied, and an inverter parallel circulating current suppression strategy with adaptive virtual composite impedance and droop control dynamic adjustment algorithm is proposed. The virtual impedance setting can weaken the influence of line difference on system stability, make the system equivalent output impedance resistive, weaken the inductive device characteristics and reduce the circulating current amplitude; the adaptive droop algorithm implantation dynamically correlates the control power with the droop coefficient, enhance the power decoupling accuracy and weaken the circulating current influenced by power changes. The simulation platform and experimental setup established by the large‐scale simulation software PSCAD/EMTDC are used to study the basic scenarios of the inverter under two conditions of equal and unequal capacity, and the rationality of the proposed control strategy is tested. [ABSTRACT FROM AUTHOR]

This study presents a bridge arm attached to the FESS motor's neutral point and reconstructs the mathematical model after a phase-loss fault to assure the safe and dependable functioning of the FESS motor after such fault. To increase the fault tolerance in FESS motors with phase-loss faults, 3D-SVPWM technology was utilized to operate the motor. The parameters of the zero-axis current compensation control were modified based on the dual-closed-loop control strategy for the speed and current. The simulation experiments conducted in this study demonstrate that the fault-tolerant control strategy adopted can significantly reduce excessive torque pulsation after the phase failure of the FESS motor, stabilize the motor output torque, and improve the fault-tolerance performance of the FESS motor's control system for the FESS motor. [ABSTRACT FROM AUTHOR]