LLCLC Resonant Converter Based Pseudo DC Link Inverter

Technological advancements in solar power systems necessitate highly reliable power inverters with a high efficiency and a small size. An LLC resonant converter-based pseudo Direct Current (DC) link inverters offer these qualities to some extent. The resonant circuits of conventional pseudo DC link inverters lack the ability to attain a zero gain and cannot handle variable frequency control which in turn requires very large filters to produce pure sinusoidal output voltages for grid. The usage of these filters consequences in the enhanced price and size of inverters; moreover, the reliability of inverters is also reduced. We propose a novel topology for a pseudo DC link inverter based on an LLCLC resonant converter. The proposed inverter does not require large filters, because it generates rectified sinusoidal output voltages. An additional parallel LC component is added in series to the resonant circuit, which makes it able to attain a zero gain through an infinite circuit impedance. The 400 W pseudo DC link inverter with a 40 V input and a 400 V output is designed and simulated on OrCAD PSpice software. The results showed that there is a significant improvement in achieving a zero gain. The possible lowest gain achieved is approximately 0.125. The proposed technique attested to be more efficient than those formerly used, subsequently contributing satisfying outcomes.

Application of Multislice Spiral CT in Diagnosis of Ankle Joint Sports Injury

In recent years, with the continuous improvement of medical treatment at home and abroad, computerized tomography (CT) technology has developed rapidly. The market competition at home and abroad is becoming increasingly fierce. The manufacturing cost of CT machines is highly valued by manufacturers. Reducing the manufacturing costs of CT machines is of great significance to medical equipment companies. The CT host is composed of a fixed control system and a rotation control system. Based on the analysis of the existing CT host system structure, this paper designs and implements a set of low-cost asynchronous variable-frequency rotation control systems based on the unchanged control interface of the existing main rotation servo control system, improving the market competitiveness of the product. Based on the constant structure of the rotating machine of the CT machine, the simulation analysis of asynchronous variable frequency control is carried out. A set of asynchronous variable frequency control design schemes and multi-stage speed curve control methods compatible with the original system structure are obtained. The verification and analysis of the functions of acceleration and deceleration control, rotation positioning, fault protection, electromagnetic radiation and other functions at the highest speed meet the system’s main performance requirements, such as acceleration and deceleration time at the highest speed, positioning accuracy, and speed stability. Through internal system verification, testing and clinical verification, the control system designed in this paper meets the design requirements. According to experimental data, the system is fully compatible with a running accuracy of 0.3%. The main performance indicators such as acceleration time and positioning accuracy have been improved. The acceleration time from static acceleration to the maximum speed of 0.39 seconds per revolution increases from 21 seconds to 19.9 seconds, and the positioning accuracy was improved from 0.3° to 0.24°. Finally, this study explores the diagnostic value of multislice spiral CT (MSCT) in ankle trauma.

Numerical Simulation of Fluid Flow Features of Mechanical Mixer with Automatic Variable Frequency Control

For many engineering fields, it is of practical significance to construct and reasonably simplify the solid-liquid two-phase flow model in the cylinder of mechanical mixer. However, the existing studies have not considered how the control technology affects the fluid features in the mixer. From the angle of automatic variable frequency control, this paper carries out a numerical simulation of the fluid flow features in mechanical mixer. Firstly, the authors constructed the system structure for the mixer with automatic variable frequency control, and summarized the basic devices and the number of input/output points of the system. Then, the relationship between the force energy and control frequency of the mixing cylinder was detailed. Afterwards, the Euler-Euler two fluid model was introduced to numerically simulate the solid-liquid two-phase flow in the cylinder of the mixer, which contains both solid particles and liquid, followed by the establishment of control equation, the drag model, and the turbulence model. The proposed model was proved effective through experiments. The research findings provide a reference for the relevant research and the optimal design of the drive module of mixers.