Mobile website
Volume 48,Issue 6,2021 Table of Contents
2021, 48(6):1-9，23.
DOI: 10.12177/emca.2021.037
Abstract:
Compared with the conventional pulse width modulation (PWM) technology, random PWM (RPWM) has effective ability of harmonic spectrum dispersion, which can reduce the noise of electromechanical load. The RPWM technology includes three basic methods: initial random switch modulation, and subsequent random pulse position and random switching frequency modulation. With the overall development of power electronics technology, RPWM has been gradually expanded from conventional carrier modulation to space vector modulation, the application prospect is increasingly broad, and the effect of power spectrum peak suppression is continuously improved. At the same time, new optimization schemes are put forward constantly, and the dispersion effect of harmonic and power spectrum is also continuously improved. The research history of RPWM is reviewed, the basic principles of some typical RPWM technologies are introduced, and the future research directions of random PWM are prospected, so as to provide a reference for further research of RPWM technology.
Compared with the conventional pulse width modulation (PWM) technology, random PWM (RPWM) has effective ability of harmonic spectrum dispersion, which can reduce the noise of electromechanical load. The RPWM technology includes three basic methods: initial random switch modulation, and subsequent random pulse position and random switching frequency modulation. With the overall development of power electronics technology, RPWM has been gradually expanded from conventional carrier modulation to space vector modulation, the application prospect is increasingly broad, and the effect of power spectrum peak suppression is continuously improved. At the same time, new optimization schemes are put forward constantly, and the dispersion effect of harmonic and power spectrum is also continuously improved. The research history of RPWM is reviewed, the basic principles of some typical RPWM technologies are introduced, and the future research directions of random PWM are prospected, so as to provide a reference for further research of RPWM technology.
2021, 48(6):10-16.
DOI: 10.12177/emca.2021.017
Abstract:
Compared with the traditional single layer air-gap motors, larger parasitic torque ripple exists in field-modulation double-stator (FMDS) motor. The torque ripple varies periodically with rotor position, which leads to speed ripple. For the existence of periodic torque ripple, the contradiction between response and overshoot, and the presence of external uncertain disturbances, a novel outer-loop speed controller based on iterative learning control and active disturbance rejection control (ILC-ADRC) is proposed. By arranging the transition process of expected speed, the excessive overshoot of speed caused by stepped input is avoided, and the initial condition requirements of iterative learning are reduced. A linear expanded state observer (LESO) is designed to simplify parameter adjustment. The past periodic rotational speed error information is added to compensate the torque ripple. Finally, the state error feedback controller is used to generate control signals. The simulation results show that the system responds quickly without overshoot, and the torque ripple of the motor is effectively reduced.
Compared with the traditional single layer air-gap motors, larger parasitic torque ripple exists in field-modulation double-stator (FMDS) motor. The torque ripple varies periodically with rotor position, which leads to speed ripple. For the existence of periodic torque ripple, the contradiction between response and overshoot, and the presence of external uncertain disturbances, a novel outer-loop speed controller based on iterative learning control and active disturbance rejection control (ILC-ADRC) is proposed. By arranging the transition process of expected speed, the excessive overshoot of speed caused by stepped input is avoided, and the initial condition requirements of iterative learning are reduced. A linear expanded state observer (LESO) is designed to simplify parameter adjustment. The past periodic rotational speed error information is added to compensate the torque ripple. Finally, the state error feedback controller is used to generate control signals. The simulation results show that the system responds quickly without overshoot, and the torque ripple of the motor is effectively reduced.
2021, 48(6):17-23.
DOI: 10.12177/emca.2021.023
Abstract:
Conventional PID and fuzzy algorithms have the problems of strong coupling and nonlinearity in the brushless DC motor (BLDCM) control system, and signal distortion is prone to appear under the action of interference. In order to solve these problems, the taxi light servo steering system is taken as the application background, the BLDCM three-closed-loop control system is taken as the research object, BP neural network, fuzzy control and PID algorithm are combined, and a kind of PID control based on fuzzy parameter modified BP neural network is proposed. Through Simulink modeling and simulation, the dynamic response characteristics of this strategy and conventional control algorithms under torque disturbance and magnetic flux disturbance are compared. The simulation results show that this improved control algorithm has excellent performance in the BLDCM position control system.
Conventional PID and fuzzy algorithms have the problems of strong coupling and nonlinearity in the brushless DC motor (BLDCM) control system, and signal distortion is prone to appear under the action of interference. In order to solve these problems, the taxi light servo steering system is taken as the application background, the BLDCM three-closed-loop control system is taken as the research object, BP neural network, fuzzy control and PID algorithm are combined, and a kind of PID control based on fuzzy parameter modified BP neural network is proposed. Through Simulink modeling and simulation, the dynamic response characteristics of this strategy and conventional control algorithms under torque disturbance and magnetic flux disturbance are compared. The simulation results show that this improved control algorithm has excellent performance in the BLDCM position control system.
2021, 48(6):24-29，36.
DOI: 10.12177/emca.2021.022
Abstract:
Conventional model predictive control (MPC) requires receding horizon optimization and prediction of all voltage vectors in a threephase twolevel inverterdriven induction motor system, and has disadvantages of high computational cost and difficulty in implementation. To solve these problems, a deadbeat MPC is proposed, which reduces the receding horizon optimization prediction voltage vector from 8 to 3. The deadbeat voltage vector is calculated and the deadbeat sector is divided. The sector is determined based on the space voltage vector position. A singlestep receding horizon optimization prediction of the vectors in the sector is performed, and the corresponding optimal switch state is output. The simulation results show that the deadbeat MPC can achieve almost the same steadystate tracking performance as the traditional MPC while reducing the computational burden of the system.
Conventional model predictive control (MPC) requires receding horizon optimization and prediction of all voltage vectors in a threephase twolevel inverterdriven induction motor system, and has disadvantages of high computational cost and difficulty in implementation. To solve these problems, a deadbeat MPC is proposed, which reduces the receding horizon optimization prediction voltage vector from 8 to 3. The deadbeat voltage vector is calculated and the deadbeat sector is divided. The sector is determined based on the space voltage vector position. A singlestep receding horizon optimization prediction of the vectors in the sector is performed, and the corresponding optimal switch state is output. The simulation results show that the deadbeat MPC can achieve almost the same steadystate tracking performance as the traditional MPC while reducing the computational burden of the system.
2021, 48(6):30-36.
DOI: 10.12177/emca.2021.030
Abstract:
The setting of weight coefficients of permanent magnet synchronous motor (PMSM) traditional model predictive torque control (MPTC) is cumbersome, and torque and magnetic flux pulsations are large. In order to solve these problems, an improved dual-vector MPTC method of PMSM is proposed. The method expands the virtual vector to increase the candidate voltage vector, and the principle that the voltage vector acts on the torque and flux linkage is used to reduce the calculation amount of selecting the candidate vector. For torque deadbeat and magnetic flux deadbeat, optimization rules are constructed by using the torque duty cycle and flux duty cycle of the candidate vector to replace the cost function in the traditional predictive torque control, avoiding the problem of setting weight coefficients. The simulation results show that the proposed method not only improves the steadystate performance, but also maintains the rapid dynamic response of MPTC.
The setting of weight coefficients of permanent magnet synchronous motor (PMSM) traditional model predictive torque control (MPTC) is cumbersome, and torque and magnetic flux pulsations are large. In order to solve these problems, an improved dual-vector MPTC method of PMSM is proposed. The method expands the virtual vector to increase the candidate voltage vector, and the principle that the voltage vector acts on the torque and flux linkage is used to reduce the calculation amount of selecting the candidate vector. For torque deadbeat and magnetic flux deadbeat, optimization rules are constructed by using the torque duty cycle and flux duty cycle of the candidate vector to replace the cost function in the traditional predictive torque control, avoiding the problem of setting weight coefficients. The simulation results show that the proposed method not only improves the steadystate performance, but also maintains the rapid dynamic response of MPTC.
2021, 48(6):37-43.
DOI: 10.12177/emca.2021.016
Abstract:
Compared with the traditional vector control, the drive signal is directly obtained by the finite control set model predictive control (FCS-MPC) through the algorithm. The method omits the pulse width modulation link, and has superior response performance. The transfer function of the control system only containing the speed loop is constructed by the improved FCS-MPC algorithm. In the load changes and parameter disturbance conditions, the frequency characteristic analysis method of the transfer function and the typical system tuning method are used to design the PI self-tuning control system based on the speed loop. Simulation comparison and verification show that the proposed method has smaller fluctuation of the speed change caused by the load torque and parameter changes and recovers faster than the traditional control. The results verify the feasibility and effectiveness of the method.
Compared with the traditional vector control, the drive signal is directly obtained by the finite control set model predictive control (FCS-MPC) through the algorithm. The method omits the pulse width modulation link, and has superior response performance. The transfer function of the control system only containing the speed loop is constructed by the improved FCS-MPC algorithm. In the load changes and parameter disturbance conditions, the frequency characteristic analysis method of the transfer function and the typical system tuning method are used to design the PI self-tuning control system based on the speed loop. Simulation comparison and verification show that the proposed method has smaller fluctuation of the speed change caused by the load torque and parameter changes and recovers faster than the traditional control. The results verify the feasibility and effectiveness of the method.
2021, 48(6):44-48.
DOI: 10.12177/emca.2021.018
Abstract:
Poor robustness and slower torque recovery of sudden load torque occur in permanent magnet synchronous motor (PMSM) speed control system using PI control algorithm and exponential sliding mode control (SMC) algorithm. In order to solve these problems, an improved reaching law SMC algorithm is designed, which is used in the speed controller of the PMSM speed control system. In order to verify the feasibility of the proposed SMC algorithm, MATLAB/Simulink is used to simulate the PMSM double-closedloop speed control system, and the traditional exponential reaching law SMC algorithm and PI control algorithm are compared. The results show that the improved reaching law sliding mode speed controller has better robustness and resistance to load disturbance.
Poor robustness and slower torque recovery of sudden load torque occur in permanent magnet synchronous motor (PMSM) speed control system using PI control algorithm and exponential sliding mode control (SMC) algorithm. In order to solve these problems, an improved reaching law SMC algorithm is designed, which is used in the speed controller of the PMSM speed control system. In order to verify the feasibility of the proposed SMC algorithm, MATLAB/Simulink is used to simulate the PMSM double-closedloop speed control system, and the traditional exponential reaching law SMC algorithm and PI control algorithm are compared. The results show that the improved reaching law sliding mode speed controller has better robustness and resistance to load disturbance.
2021, 48(6):49-56，62.
DOI: 10.12177/emca.2021.025
Abstract:
In order to analyze the control strategy of doubly salient electromagnetic motor (DSEM), it is necessary to establish an accurate control model. The stator and rotor of DSEM are both doubly salient structure, which has obvious edge effects and high local saturation. The flux linkage and torque of the motor are both nonlinear functions of armature current, excitation current and rotor position angle. Therefore, it is difficult to establish accurate control model by conventional methods. Based on the indepth analysis of the electromagnetic characteristics of the motor, the data table of flux linkage and torque about the relationship between current and rotor position angle is established by finite element simulation. The flux linkage and torque model functions of DSEM are built by using the threedimensional lookup table Simulink method, which is then used to establish the simulation model of DSEM together with the voltage equation. All aspects of the model are analyzed and verified. Taking the noload back electromotive force (EMF) of hysteresis chopping of excitation winding and asymmetric control strategy for armature current as an example, the simulation results are compared with the finite element simulation and experiment. The results verify the accuracy, effectiveness and feasibility of the model.
In order to analyze the control strategy of doubly salient electromagnetic motor (DSEM), it is necessary to establish an accurate control model. The stator and rotor of DSEM are both doubly salient structure, which has obvious edge effects and high local saturation. The flux linkage and torque of the motor are both nonlinear functions of armature current, excitation current and rotor position angle. Therefore, it is difficult to establish accurate control model by conventional methods. Based on the indepth analysis of the electromagnetic characteristics of the motor, the data table of flux linkage and torque about the relationship between current and rotor position angle is established by finite element simulation. The flux linkage and torque model functions of DSEM are built by using the threedimensional lookup table Simulink method, which is then used to establish the simulation model of DSEM together with the voltage equation. All aspects of the model are analyzed and verified. Taking the noload back electromotive force (EMF) of hysteresis chopping of excitation winding and asymmetric control strategy for armature current as an example, the simulation results are compared with the finite element simulation and experiment. The results verify the accuracy, effectiveness and feasibility of the model.
2021, 48(6):57-62.
DOI: 10.12177/emca.2021.027
Abstract:
The torque density of five-phase permanent magnet synchronous motor (PMSM) can be increased by injecting the third harmonic current. Besides the third harmonic, weakening the other spatial harmonics generated by the permanent magnet can reduce the torque ripple, vibration and noise of the motor. Therefore, an optimization design method of rotor shape is proposed for the third harmonic injection five-phase interior permanent magnet synchronous motor (IPMSM). The analytical expression of the rotor core shape is deduced theoretically, and the finite element model is built according to the motor parameters. The air-gap flux density harmonic content and torque ripple of the optimized motor model are obtained. The motor models before and after optimization are compared in simulation, and the simulation results are consistent with the theoretical analysis, proving the significant optimization effect of air-gap magnetic field.
The torque density of five-phase permanent magnet synchronous motor (PMSM) can be increased by injecting the third harmonic current. Besides the third harmonic, weakening the other spatial harmonics generated by the permanent magnet can reduce the torque ripple, vibration and noise of the motor. Therefore, an optimization design method of rotor shape is proposed for the third harmonic injection five-phase interior permanent magnet synchronous motor (IPMSM). The analytical expression of the rotor core shape is deduced theoretically, and the finite element model is built according to the motor parameters. The air-gap flux density harmonic content and torque ripple of the optimized motor model are obtained. The motor models before and after optimization are compared in simulation, and the simulation results are consistent with the theoretical analysis, proving the significant optimization effect of air-gap magnetic field.
2021, 48(6):63-68.
DOI: 10.12177/emca.2021.021
Abstract:
The fast design of the stator and rotor of the complex synchronous reluctance motor (SynRM) with multi-layer magnetic barrier is studied. Taking a 3 kW, 4-pole motor as an example, the performance of the SynRM with different winding forms is compared. In order to reduce the torque ripple, a simplified model of the typical C-type magnetic barrier rotor is proposed. The influences of various parameters on the motor output torque and torque ripple are studied, and the parameters of the magnetic barrier are further optimized with the help of multi-objective optimization algorithm, which provides a reference for the design and analysis of similar motors.
The fast design of the stator and rotor of the complex synchronous reluctance motor (SynRM) with multi-layer magnetic barrier is studied. Taking a 3 kW, 4-pole motor as an example, the performance of the SynRM with different winding forms is compared. In order to reduce the torque ripple, a simplified model of the typical C-type magnetic barrier rotor is proposed. The influences of various parameters on the motor output torque and torque ripple are studied, and the parameters of the magnetic barrier are further optimized with the help of multi-objective optimization algorithm, which provides a reference for the design and analysis of similar motors.
2021, 48(6):69-76.
DOI: 10.12177/emca.2021.032
Abstract:
In view of the serious heating problem of drive motor for vacuum pump in extreme vacuum environment, the cooling system of the drive motor for vacuum pump is designed and analyzed. A 2.9 kW shielded asynchronous motor is taken as the research object. The three-dimensional model of the motor with spiral waterway is established by finite element software, and the loss is calculated. According to the velocity and pressure distribution of spiral waterway, the rationality of waterway size design is verified, and the temperature distribution of each part of the motor is simulated and analyzed. According to the temperature changes of the motor under double rated load and cooling water fault conditions, the safe operation time of the motor is analyzed. Finally, the temperature rise test of the prototype is carried out, and the test results and simulation results are compared and analyzed. It is verified that the cooling system with spiral channel in the shell has a certain cooling effect on the drive motor for the vacuum dry pump, which provides a scientific basis for the research of the drive motor for vacuum pump in the extreme vacuum environment in the future.
In view of the serious heating problem of drive motor for vacuum pump in extreme vacuum environment, the cooling system of the drive motor for vacuum pump is designed and analyzed. A 2.9 kW shielded asynchronous motor is taken as the research object. The three-dimensional model of the motor with spiral waterway is established by finite element software, and the loss is calculated. According to the velocity and pressure distribution of spiral waterway, the rationality of waterway size design is verified, and the temperature distribution of each part of the motor is simulated and analyzed. According to the temperature changes of the motor under double rated load and cooling water fault conditions, the safe operation time of the motor is analyzed. Finally, the temperature rise test of the prototype is carried out, and the test results and simulation results are compared and analyzed. It is verified that the cooling system with spiral channel in the shell has a certain cooling effect on the drive motor for the vacuum dry pump, which provides a scientific basis for the research of the drive motor for vacuum pump in the extreme vacuum environment in the future.
2021, 48(6):77-82.
DOI: 10.12177/emca.2021.019
Abstract:
In order to analyze the fluid flow and temperature distribution of 10 kV compact asynchronous motor under the action of internal and external fans under rated working conditions, a three-dimensional heat dissipation model of the motor is established by coupling the flow field with the temperature field, and a rotating air region model is established for the internal and external fans and the air around the rotor self-propelled fan. Based on the theoretical analysis of computational fluid dynamics, the reasonable basic assumption of the temperature field of the motor is made and the corresponding boundary conditions are given. Through the fluid thermal coupling simulation, the fluid flow field inside and outside the motor under the condition of double fans rotating with the shaft and the spatial distribution characteristics of the temperature of each component of the motor are obtained. The simulation results show that the maximum temperature of the motor is located in the middle of the rotor bar, and the maximum temperature of the stator winding is 113 ℃, which meets the F-class insulation requirements. The stator and rotor temperature can be effectively reduced when the internal fan is working.
In order to analyze the fluid flow and temperature distribution of 10 kV compact asynchronous motor under the action of internal and external fans under rated working conditions, a three-dimensional heat dissipation model of the motor is established by coupling the flow field with the temperature field, and a rotating air region model is established for the internal and external fans and the air around the rotor self-propelled fan. Based on the theoretical analysis of computational fluid dynamics, the reasonable basic assumption of the temperature field of the motor is made and the corresponding boundary conditions are given. Through the fluid thermal coupling simulation, the fluid flow field inside and outside the motor under the condition of double fans rotating with the shaft and the spatial distribution characteristics of the temperature of each component of the motor are obtained. The simulation results show that the maximum temperature of the motor is located in the middle of the rotor bar, and the maximum temperature of the stator winding is 113 ℃, which meets the F-class insulation requirements. The stator and rotor temperature can be effectively reduced when the internal fan is working.
2021, 48(6):83-88，99.
DOI: 10.12177/emca.2021.026
Abstract:
In order to better guide the wind generator design, a 3 MW air-air cooled doubly-fed wind generator is taken as an example for the research of flow and heat transfer characteristics. Based on the theory of hydromechanics and numerical heat transfer, the 3D fluid flow and heat transfer coupled physical and mathematical models are established according to the model of air-air cooler and wind generator. Fluent software is used to numerically simulate the steady 3D flow and temperature fields of the wind generator under rated working conditions with given fundamental assumptions and boundary conditions, and the experimental data of winding temperature rise are obtained by adopting resistance and embedded temperature detector (ETD) methods under the same working conditions. It is found that the error is within 5 K between the numerical simulation results and experimental data, indicating that the numerical method is credible. Finally, the distributions of the wind generator flow and temperature fields are analyzed, and the flow rate of the 18-vent motor is calculated in detail. This method provides a theoretical support for the simulation and optimization of new wind generators.
In order to better guide the wind generator design, a 3 MW air-air cooled doubly-fed wind generator is taken as an example for the research of flow and heat transfer characteristics. Based on the theory of hydromechanics and numerical heat transfer, the 3D fluid flow and heat transfer coupled physical and mathematical models are established according to the model of air-air cooler and wind generator. Fluent software is used to numerically simulate the steady 3D flow and temperature fields of the wind generator under rated working conditions with given fundamental assumptions and boundary conditions, and the experimental data of winding temperature rise are obtained by adopting resistance and embedded temperature detector (ETD) methods under the same working conditions. It is found that the error is within 5 K between the numerical simulation results and experimental data, indicating that the numerical method is credible. Finally, the distributions of the wind generator flow and temperature fields are analyzed, and the flow rate of the 18-vent motor is calculated in detail. This method provides a theoretical support for the simulation and optimization of new wind generators.
2021, 48(6):89-94.
DOI: 10.12177/emca.2021.029
Abstract:
The good operation characteristics of permanent magnet (PM) assisted synchronous reluctance motors are closely related to the inductance parameters, so it is necessary to accurately calculate the inductance parameters in the electromagnetic design. The principles of the equivalent d-q axis method, static field method, transient field method and frozen permeability method are introduced, and the d-q axis inductance parameters are calculated. The inductance parameters of the prototype are tested by voltammetry experiment. The simulation results are compared with the test results to verify the accuracy of the methods. It is shown that the difference between the simulation results of frozen permeability method and the test results is within 3% and the frozen permeability method is more accurate among the four methods analyzed.
The good operation characteristics of permanent magnet (PM) assisted synchronous reluctance motors are closely related to the inductance parameters, so it is necessary to accurately calculate the inductance parameters in the electromagnetic design. The principles of the equivalent d-q axis method, static field method, transient field method and frozen permeability method are introduced, and the d-q axis inductance parameters are calculated. The inductance parameters of the prototype are tested by voltammetry experiment. The simulation results are compared with the test results to verify the accuracy of the methods. It is shown that the difference between the simulation results of frozen permeability method and the test results is within 3% and the frozen permeability method is more accurate among the four methods analyzed.
2021, 48(6):95-99.
DOI: 10.12177/emca.2021.031
Abstract:
In order to meet the requirements of automatic inspection equipment in non-destructive testing (NDT) of nuclear power plant, a universal, low-cost, small DC motor motion controller based on STM32 is developed. The controller is mainly composed of micro control unit (MCU) minimum system, motor driving circuit, signal processing circuit of encoder and communication circuit. The duty cycle of pulse width modulation (PWM) is adjusted by incremental PID algorithm and integral separation position PID algorithm in STM32, achieving the ideal effect of rapidity, stability and small steady-state error. Based on this controller, a two-axis motion control system is developed to realize the application of automatic raster scan for the weld joint region of the pipeline outer wall.
In order to meet the requirements of automatic inspection equipment in non-destructive testing (NDT) of nuclear power plant, a universal, low-cost, small DC motor motion controller based on STM32 is developed. The controller is mainly composed of micro control unit (MCU) minimum system, motor driving circuit, signal processing circuit of encoder and communication circuit. The duty cycle of pulse width modulation (PWM) is adjusted by incremental PID algorithm and integral separation position PID algorithm in STM32, achieving the ideal effect of rapidity, stability and small steady-state error. Based on this controller, a two-axis motion control system is developed to realize the application of automatic raster scan for the weld joint region of the pipeline outer wall.
2021, 48(6):100-107，113.
DOI: 10.12177/emca.2021.020
Abstract:
In order to overcome the problems of limited boost capacity and high switching stress of the quadratic boost converter, a non-isolated improved quadratic boost high-gain DC-DC converter is proposed, with two topological structures. The operation principles of the two topologies are analyzed, and the voltage gain and switching stress of the circuit topology are theoretically deduced and compared with existing converters. The proposed converter raises the output gain while reducing the switching stress and enhancing the efficiency. A simulation model is established in MATLAB/Simulink, and the simulation results verify the correctness of the theoretical calculations. Finally, an experimental prototype of the converter is built, and the feasibility of the converter design scheme is verified through the comparative analysis of theoretical deduction and experimental results.
In order to overcome the problems of limited boost capacity and high switching stress of the quadratic boost converter, a non-isolated improved quadratic boost high-gain DC-DC converter is proposed, with two topological structures. The operation principles of the two topologies are analyzed, and the voltage gain and switching stress of the circuit topology are theoretically deduced and compared with existing converters. The proposed converter raises the output gain while reducing the switching stress and enhancing the efficiency. A simulation model is established in MATLAB/Simulink, and the simulation results verify the correctness of the theoretical calculations. Finally, an experimental prototype of the converter is built, and the feasibility of the converter design scheme is verified through the comparative analysis of theoretical deduction and experimental results.
2021, 48(6):108-113.
DOI: 10.12177/emca.2021.033
Abstract:
A novel single-phase grounding fault protection scheme for outgoing transmission lines of doubly-fed wind farms based on waveform similarity factor is proposed. The short-circuit current expression of wind turbine port under grid fault is derived, and the characteristics of transient fault current after the faults on wind power outgoing transmission line are analyzed. On this basis, a zero-mode instantaneous model of the wind power outgoing transmission system is established. Then the zero-mode voltage similarity factor is constructed by using the characteristics of the model difference between the internal and external faults to locate the fault. Finally, the simulation verifies that this method can correctly identify the internal and external faults in various single-phase grounding fault conditions, and the result is not affected by fault resistance and current frequency deviation.
A novel single-phase grounding fault protection scheme for outgoing transmission lines of doubly-fed wind farms based on waveform similarity factor is proposed. The short-circuit current expression of wind turbine port under grid fault is derived, and the characteristics of transient fault current after the faults on wind power outgoing transmission line are analyzed. On this basis, a zero-mode instantaneous model of the wind power outgoing transmission system is established. Then the zero-mode voltage similarity factor is constructed by using the characteristics of the model difference between the internal and external faults to locate the fault. Finally, the simulation verifies that this method can correctly identify the internal and external faults in various single-phase grounding fault conditions, and the result is not affected by fault resistance and current frequency deviation.
2021, 48(6):114-117.
DOI: 10.12177/emca.2021.028
Abstract:
In the process of eliminating the abnormal temperature rise of motor bearing, a motor online maintenance method is proposed, which can avoid the shutdown accident caused by abnormal temperature of motor bearing. In this method, the lubricating grease is replaced online rather than offline. This technology prolongs the service life of motor bearing, reduces the labor intensity of workers, and improves the economic benefits of enterprises.
In the process of eliminating the abnormal temperature rise of motor bearing, a motor online maintenance method is proposed, which can avoid the shutdown accident caused by abnormal temperature of motor bearing. In this method, the lubricating grease is replaced online rather than offline. This technology prolongs the service life of motor bearing, reduces the labor intensity of workers, and improves the economic benefits of enterprises.
You are thevisitor
沪ICP备16038578号-3
Electric Machines & Control Application ® 2025
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
沪ICP备16038578号-3
Electric Machines & Control Application ® 2025
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
