Variable Frequency Speed Regulation Research Articles

Research on High-Frequency Isolated NPC Three-Level Inverter for Frequency Conversion and Speed Regulation

Mining frequency converters are the primary means for achieving variable frequency speed regulation of electromechanical equipment in coal mines, offering energy-saving benefits for coal mining enterprises. The common power supply method involves converting high voltage to low voltage using power frequency transformers before supplying equipment. However, this integration of power frequency transformers with supply devices occupies significant space, making it unsuitable for confined underground environments. Additionally, they suffer from poor output waveform quality and high harmonic content. To tackle these challenges, this paper presents a three-stage topology for high-frequency isolated frequency conversion and speed regulation, utilizing three-phase uncontrolled rectification, a single active isolated DC/DC converter, and an NPC three-level inverter. The control strategies for each stage are discussed in detail. Simulations and experimental results confirm the validity and feasibility of the proposed design, demonstrating enhanced stability and dynamic performance of the three-stage high-frequency isolated frequency converter.

Application of Variable Frequency Speed Regulation Technology in Industrial Electrical Automation Control

Before the emergence of frequency conversion speed regulation technology, the industrial electrical automation operation mode has been realized, but in the early operation, the operation mechanism of the automatic control system is relatively simple, that is, according to the unified logic, the start and stop control of electrical equipment, this mode can mainly play a reasonable allocation of electrical equipment operating time and reduce the failure rate of equipment in practical work. However, the simple start-stop control mechanism will affect the capacity level of industrial units, which shows that there are defects in early automation control. So in the context of modern technology, some scholars have proposed the application of frequency conversion speed regulation technology in automatic control, refining the startstop control mechanism to ensure the "relative maximum production capacity" as much as possible, while taking into account the energy efficiency of reducing the failure rate.

Improved self‐balancing voltage five‐level ANPC converter and its control strategy

SummaryFive‐level active neutral‐point‐clamped (5L‐ANPC) converters have great practical potential in the field of medium and high voltage variable frequency speed regulation. However, the dynamic and static voltage imbalance of the series IGBTs may cause permanent damage to the device, which limits its popularization and application. In this paper, an improved self‐balancing voltage 5L‐ANPC topology (ISBV‐5L‐ANPC) is proposed to address such voltage balancing problem as series switches and high voltage leaps, which realizes dynamic and static voltage equalization by connecting the self‐balancing module consisting of an auxiliary capacitor to the bridge arm, so that it clamps the series switches. In this paper, the operation principle of ISBV‐5L‐ANPC is given in detail, and the control strategy of ISBV‐5L‐ANPC is proposed, and the key parameters in the topology are analyzed and designed. Finally, an ISBV‐5L‐ANPC prototype was built, and the effectiveness of the proposed topology and the feasibility of the control strategy are verified through the experimental results.

The precision motor losses-based real-time optimal control method for air-conditioning system considering energy saving and thermal comfort

The power consumption of air-conditioning (AC) systems is often miscalculated due to the impact of multiple motor systems, leading to difficulties in system control and significant energy waste. In this work, we propose a precision motor losses-based real-time optimal control (PMLRTOC) strategy for AC systems, which considers fully the unique characteristics of pump load and variable frequency speed regulation. The proposed strategy offers an innovative solution to this issue, integrating constraints on the water supply temperature, the temperature difference between supply and return water, and indoor thermal comfort. The control strategy is applied and examined in the context of a 90-floor, Grade A mega office building in Hong Kong. The findings demonstrate that the proposed mathematical model implemented through the optimal control strategy is able to reduce energy consumption by 18.2% at low load rates and 23.9% at high load rates. Compared to a control strategy based on a constant temperature difference, a strategy employing variable temperature difference can further reduce energy consumption by 13.7%. Furthermore, most parameters required for the PMLRTOC strategy are fixed and can be readily obtained from equipment manuals, which enhances the practicality of the model. Therefore, this work offers a widely applicable optimal control model for various AC systems, accelerating energy savings in public buildings and contributing to the achievement of carbon peak and neutrality targets.

Research on Fuzzy PID Control of Concrete Press Based on Frequency Conversion Speed Regulation System

In the static compression elastic modulus test of concrete, controlling the value of the loading force is the key to the success of the test. The test requires that the set force value be reached quickly, and the fluctuation should be stable within the test standard range, even in the presence of external interference. There is no oscillation in the transient process, and the best adjustment process is achieved. This article uses a variable frequency speed regulation system to control the value of the loading force, but the hydraulic system is susceptible to fluctuations due to the influence of oil pressure and temperature. Conventional PID control cannot meet its performance requirements. As a result, this article proposes a fuzzy PID for the press’s variable frequency speed regulation system. It uses MATLAB/Simulink and the controller to simulate the system. Simulation experiments show that fuzzy PID control has a better control effect than conventional PID control.

A Fast and Accurate Loss Model of Converter-Fed Induction Motor in Central Air-Conditioning System

In the traditional optimization model of central air-conditioner, the loss model of converter-fed motor is very rough, resulting in a large amount of energy waste. In this paper, a new energy loss model of central air-conditioning system from power to client is proposed. In the establishment of the loss model, the characteristics of pump load and variable frequency speed regulation are fully considered, and the electromagnetic variables which are difficult to be collected are replaced by the motor speed which can be directly calculated, so that the motor loss model can be introduced into the optimization model of the central air-conditioning system. A 5.5 kW converter-fed induction motor is tested under different speeds and loads, and the two-dimensional (2-D) loss data were obtained. Then, one-dimensional data were extracted from the measured 2-D data combined with the load characteristics of the pump, and compared with the calculated values of the proposed model in this article. The results show that the proposed loss model is of good accuracy and versatility. Because the proposed analytical model only needs the variable of motor speed to accurately estimate the losses, it can be easily applied to the optimization of central air-conditioning system.

Soft-Starting Brushless Doubly Fed Machine Winding Design and Magnetic Field Analysis

With the development and maturity of control technology, brushless doubly-fed motor (BDFM) is widely used in the field of variable frequency speed regulation. In order to improve motor starting performance, a soft starting method is proposed to reduce impulse current. The core of the method is to reconstruct the stator power winding and rotor winding. The BDFM with wound rotor is flexible in structure, and the air-gap magnetic field distribution can be changed by adjusting the pitch, turns and connection mode of stator and rotor windings, so as to improve the motor starting performance. In this paper, the design process, connection mode and working principle of the stator and rotor of a BDFM with a 2/4 pole pairs are introduced in detail. In addition, a multi-loop chain equivalent circuit is used to calculate the starting torque in this connection mode. Finally, the starting performance of the motor is analyzed by finite element method, and an experimental prototype is made, which proves the effectiveness of the scheme.

Research on High-Frequency Isolation Type of Dual-PWM Variable Frequency Speed Regulation

Research on High-Frequency Isolation Type of Dual-PWM Variable Frequency Speed Regulation

Optimization Design and Simulation of Frequency Conversion and Speed Control Integrated Machine

In order to realize the rapid start of equipment, the direct start method is widely used in domestic fully mechanized coal mining equipment, which forms a great starting impulse current and reduces the service life of the equipment. If a frequency converter is used to start the equipment with frequency conversion, it will face the problem of a large area and it is difficult to apply it underground. In response to this problem, the integrated variable frequency speed regulation machine studied in this paper adopts an integrated design to meet the needs of underground coal mines. The purpose of this paper is to optimize the design and simulation of the variable frequency speed control integrated machine. The experiment, which was conducted on the design of the integrated variable frequency speed regulation machine based on the optimized design, involved the experimentation and analysis of the design of the integrated variable frequency speed regulation machine for mining. Using the induction motorized structural dimension meter formula, a simulation test was conducted to compare the mining variable frequency speed regulation integrated machine with others.

Transient Characteristic Analysis of Variable Frequency Speed Regulation of Axial Flow Pump

In order to explore the influence of different rotational acceleration on the transient internal and external flow characteristics of the axial flow pump and improve the performance of the pump, numerical simulations and experiments were used to analyze the variable frequency speed regulation characteristics of the axial flow pump. Taking three-dimensional turbulent numerical simulation as the main research method and CFX as the calculation platform, three variable frequency speed regulation methods were used to conduct transient numerical simulation; keep the acceleration constant, increased and decreased; and obtain the real-time pump performance curve and pressure characteristic curve. Uniform acceleration and deceleration with constant acceleration maintained the stable change and good stability of head and shaft power, and the pressure change was the most stable in the process. The acceleration and deceleration with decreasing acceleration ran most smoothly at high speed, and the frequency conversion effect was the best. At the same time, the transition to steady-state operation was also the most stable. The research in this paper can provide reference for the stable operation of variable frequency speed regulation of the axial flow pump.

Numerical Simulation of Axial-Flow Pump Cavitation Based on Variable Frequency Speed Regulation

In order to investigate the influence of variable voltage and variable frequency (VVVF) regulation on the cavitation performance of the axial-flow pump, numerical simulation and experiments were used to analyze the cavitation performance of an axial-flow pump under different VVVF modes. The VVVF modes were uniform acceleration with constant acceleration, variable acceleration with increasing acceleration, variable acceleration with decreasing acceleration, and its corresponding deceleration scheme. Furthermore, a comprehensive performance test rig was built for the pump to carry out cavitation visualization tests which verified the accuracy of numerical simulation. For the uniform acceleration scheme with constant acceleration, the change of flow field inside the impeller was stable, the expansion rate of cavitation was slow, and the growth rate of the cavitation volume was the slowest. For the variable acceleration scheme with decreasing acceleration, the cavitation extended rapidly due to the large initial velocity. For the variable acceleration scheme with increasing acceleration, cavitation extension was the slowest. The growth rate of the cavity volume of the two variable acceleration schemes was faster than that of the uniform acceleration scheme, and the changing trend was consistent. This feature indicates that the impeller rotation speed has a significant impact on cavitation, and excessive rotation speed will rapidly extend the cavitation. By monitoring the influence of cavitation on pressure distribution under VVVF, it was shown that the three acceleration schemes all produce large pressure fluctuation. For the uniform acceleration scheme with constant acceleration, the fluctuation range of pressure was more balanced, and the pressure dropped slowly. For the acceleration scheme with higher acceleration, the pressure fluctuation amplitude increased in the late stage of acceleration and the pressure decline speed accelerated. For the acceleration scheme with decreasing acceleration, the pressure showed a downward trend with violent fluctuations in the early stage and gradually tended to be flat in the late stage.

Induction motor efficiency maximizing based on torque per power index

<span>In this paper, efficiency maximization of induction motor variable frequency speed regulation system based on torque per power (TPP) index is proposed. The detail of the mathematical model of the induction motor considering the iron loss and the rotor field orientation, the relationship between the motor torque loss power ratio and the motor speed and slip frequency presented. The functional relationship between the torque loss power ratio and the motor speed and slip is derived, and the derivative is obtained to find the optimal slip frequency corresponding to the maximum value. The simulation model and experimental platform of the control system were built in Matlab/Simulink to verify the effectiveness of the method. The result approved the torque loss power ratio takes the maximum value, the high energy efficiency operation with the minimum power loss of the motor control system is realized.</span>

Application of PLC in Variable Frequency Constant Pressure Control System for Mine Emulsion Pump Station

Programmable logic controller (PLC) is an automatic control device made of microcomputer technology. It is based on sequential control, supplemented by loop adaptive, can complete logical judgment, timing, memory and numerical functions. The application of PLC in the variable frequency and constant pressure control system of mine emulsion pump station is studied. The emulsion pump station for mine is introduced. Based on the practice of energy saving, safety and protection equipment, the application of variable frequency speed regulation and constant pressure technology in emulsion pump is described. The working principle and PLC control system of emulsion pump control system are introduced by means of PLC circuit control. The experimental results show that the design of variable frequency and constant pressure control system based on PLC can greatly save energy consumption. In the variable frequency state, the average temperature of the pump body does not exceed 45°, indicating that the variable frequency constant voltage control system can improve the service life of the equipment.

Harmonic analysis of AC drive double PWM back to back network side

Aiming at the problem of harmonic pollution in the control system of large-scale steel rolling equipment in metallurgical plant, the mechanism of harmonic generation in AC-AC frequency conversion and AC-DC-AC variable-frequency speed regulation system is analyzed, and a double PWM back-to-back AC speed regulation system is proposed. This system can not only realize the regeneration energy of frequency converter, but also reduce the harmonic wave, and greatly improve the power factor of the system. Finally, through MATLAB simulation, the harmonic of AC-AC frequency conversion and AC-DC-AC variable-frequency speed regulation system is analyzed, and compared with PWM back-to-back AC speed regulation system, the superiority, effectiveness and feasibility of PWM back-to-back AC speed regulation system design for large-scale AC drive device control are proved.

Research of Harmonic Index and Testing Method Based on Virtual Instrument

In view of the practical problems such as the imperfect harmonic testing and evaluation methods of the variable frequency speed regulation system and the high operating cost, a harmonic evaluation index system including 9 indexes is established, and the calculation method of each index is clarified. At the same time, the harmonic testing and analysis method of the variable frequency speed regulation system based on virtual instruments is proposed. The Labview software platform is combined with an external data acquisition module to replace the traditional testing instruments for harmonic testing and signal acquisition, processing and analysis. On the basis of theoretical research, an experimental platform was built to conduct verification experiments, and then the application experiments of 2 working conditions were carried out. The results shows that the test method was correct and feasible. Based on the experimental results, further analysis of the impact of harmonics on the performance of the variable frequency speed control system, and the corresponding law of influence will be obtained, which will provide guidance for the subsequent development of harmonic prevention and other related work.

Integrated-Power-Control-Strategy-Based Electrolytic Capacitor-Less Back-to-Back Converter for Variable Frequency Speed Control System

This article presents an integrated power control strategy (IPCS) for a variable frequency speed regulation system, which consists of a back-to-back converter and a small film dc-link capacitor. Due to the lack of large-capacity energy storage components in the dc bus, there is a strong power coupling between the rectifier and the inverter. The dynamic response is limited and dc-link voltage oscillates because the traditional method controls rectification and inversion separately. The IPCS is proposed to achieve dynamic balance of the system power through synchronous control of the rectifier and inverter. High conversion efficiency guarantees the power balance of the rectifier and inverter meanwhile reduces the dc bus voltage ripple. To further reduce the dc-link voltage ripple and maintain the stability of the dc-link voltage under step changes of load, a virtual inertia control method is proposed, which consists of a virtual resistance control block and a virtual capacitor control block. As a result, the dc-link voltage ripple and the total harmonic distortion of the dc-link current can be improved. Simulations and experimental results are given to provide further validation of the proposed IPCS under different operating scenarios.

Design of Variable Frequency Speed Regulation and Constant Pressure Water Supply System

With the increase of population density and the improvement of human economic level, the emergence of high-rise buildings has put forward higher requirements on infrastructure such as building hydropower, traditional water supply methods have disadvantages such as secondary pollution, unstable water pressure, and high energy consumption. Therefore, variable frequency and constant pressure water supply have gradually become the main method of water supply for high-rise buildings. In order to meet the higher water supply requirements of urban residential quarters, a PLC-based variable frequency speed regulation and constant pressure water supply monitoring system is designed. The main control objective is to stabilize the water supply pressure. The inverter is driven by a three-step variable frequency control method. The pressure sensor of the water supply pipeline detects the pressure value in real time, uses the PID control algorithm, and outputs the frequency setting value to the inverter through the PLC, and then realizes the control of the water pump outlet pressure and achieves the purpose of constant pressure water supply. On the basis of considering the program capacity and expansion requirements, this system selects S7-1200 compact PLC as the main controller, uses modular programming as the basic concept to control the PID control program, logic switching program, and alarm breaking the program has been programmed and debugged. The test result shows that the designed control algorithm is effective, the logic function is complete, and it has a certain application and reference value. The frequency conversion constant pressure water supply system can realize the automatic switching of the operation status and the number of pumps in operation under different water supply requirements, and further improve the automation degree of the system on the basis of meeting the control requirements.

Application of Variable Frequency Speed Regulation Technology in Fan System

With regard to the problem in fan air volume control, the research on air volume method was carried out, and the air volume control method for frequency conversion speed regulation was adopted. In this regard, a motor variable frequency speed regulation system was designed, and a variable frequency control software was developed. In order to verify the control effect of the system on the fan air volume, a measurement experiment on the fan speed was carried out, and it was concluded that the variable frequency speed regulation method was highly precised, and had a sound linearity. While finally, this variable frequency speed regulation system was applied in the fan system, and the equal thickness collection experiment on the material was carried out in order to ensure the strict control over the air volume, which has obtained a relatively sound application effect.

Automation Design of Water Supply System for Residential Area

Variable-frequency constant-pressure water supply system is gradually developed based on variable frequency speed regulation technology. In this paper, it is carried out of stepless speed regulation, constant pressure control and the soft starting of the water supply system by the combination of frequency converter and PLC. This control system is recommendable for its high stability, reliability and automation.

A Novel Hybrid Control Method for Single-Phase-Input Variable Frequency Speed Control System With a Small DC-Link Capacitor

A novel hybrid control method, which consists of dual-frequency tracking control (DFTC) and virtual inertia control (VIC), is proposed for single-phase-input variable frequency speed regulation system with a small dc-link capacitor. Because of lacking a large-capacity energy storage device, the dc-link voltage is a pulsating dc, which causes a strong power coupling relationship between the rectifier and inverter side. The instantaneous power and dq -axis currents of the inverter contain both ac and dc components at the same time, which cannot be controlled well using traditional proportional-integrational (PI) controllers. Herein the DFTC that is based on a PI-resonant controller is proposed to accurately track ac and dc components of the instantaneous power and dq -axis currents respectively. With higher open-loop gain at both low frequency and the specified resonant frequency, the proposed DFTC ensures accurate tracking of the ac and dc components of power and dq -axis currents, high-power-factor, and low total harmonic distortion (THD) of input grid current. To maintain the stability of the dc-link voltage under step changes of load, a VIC is proposed. Subsequently, the input power factor and the fluctuation of dc-link voltage can be improved in the system. Simulations and experimental results are given to provide further validation of the proposed DFTC and VIC under different operating scenarios.