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Volume 51,Issue 8,2024 Table of Contents
2024, 51(8):1-11.
DOI: 10.12177/emca.2024.081
Abstract:
As an important part of the new power system, the energy interaction and sharing of multi-microgrids are conducive to the consumption of renewable energy and the enhancement of multi-agents operation efficiency. Aiming at the multi-microgrids source-load uncertainty and data privacy problems, a multi-microgrids cooperative optimal scheduling method based on energy sharing is proposed. Firstly, a shared energy storage and microgrid economic dispatching model based on a multi-agent interaction framework is constructed. Then, the power pricing strategies for shared energy storage and the economic scheduling decisions for multi-microgrids are realized by deep reinforcement learning method and mathematical planning method, respectively. Finally, simulation data analysis shows that the proposed cooperative optimal scheduling method can quickly cope with the stochastic variation of source-load, as well as effectively reduce the operation cost of multi-microgrids.
As an important part of the new power system, the energy interaction and sharing of multi-microgrids are conducive to the consumption of renewable energy and the enhancement of multi-agents operation efficiency. Aiming at the multi-microgrids source-load uncertainty and data privacy problems, a multi-microgrids cooperative optimal scheduling method based on energy sharing is proposed. Firstly, a shared energy storage and microgrid economic dispatching model based on a multi-agent interaction framework is constructed. Then, the power pricing strategies for shared energy storage and the economic scheduling decisions for multi-microgrids are realized by deep reinforcement learning method and mathematical planning method, respectively. Finally, simulation data analysis shows that the proposed cooperative optimal scheduling method can quickly cope with the stochastic variation of source-load, as well as effectively reduce the operation cost of multi-microgrids.
2024, 51(8):12-19.
DOI: 10.12177/emca.2024.067
Abstract:
In response to the challenges posed by the weak support of power electronics based renewable energy systems and the resulting decrease in the stability of high-proportion renewable energy power grids, the grid integration technology for synchronous motor-generator pair (MGP) is proposed, which enables renewable energy units to integrate into the grid via a real synchronous machine interface and actively provide frequency and voltage support to the grids. While some theoretical and experimental research has been conducted on MGP system, there remains a lack of actual operation experience and complete equipment. Addressing the operational issues of MGP systems integrated into actual microgrids, based on a practical MGP application case, investigates the coordinated operation methods and hardware for MGP. A coordinated control method in microgrids for MGP system is proposed, which can achieve control of power transmission and stable grid integration of MGP. Furthermore, a 10 kW integrated MGP grid integration device is developed, and through experiments, feasibility of the developed device is validated.
In response to the challenges posed by the weak support of power electronics based renewable energy systems and the resulting decrease in the stability of high-proportion renewable energy power grids, the grid integration technology for synchronous motor-generator pair (MGP) is proposed, which enables renewable energy units to integrate into the grid via a real synchronous machine interface and actively provide frequency and voltage support to the grids. While some theoretical and experimental research has been conducted on MGP system, there remains a lack of actual operation experience and complete equipment. Addressing the operational issues of MGP systems integrated into actual microgrids, based on a practical MGP application case, investigates the coordinated operation methods and hardware for MGP. A coordinated control method in microgrids for MGP system is proposed, which can achieve control of power transmission and stable grid integration of MGP. Furthermore, a 10 kW integrated MGP grid integration device is developed, and through experiments, feasibility of the developed device is validated.
2024, 51(8):20-29.
DOI: 10.12177/emca.2024.069
Abstract:
In the sensorless control system for interior permanent magnet synchronous motor based on the extended Kalman filter (EKF) approach, accurate estimation of motor speed and rotor position is important. To address the issue of decreased estimation accuracy for speed and rotor position due to phase current gain errors, a method for compensating position estimation errors is proposed. Firstly, through theoretical derivation, it is shown that phase current gain errors can cause estimated speed and rotor position to oscillate at twice the supply frequency during the EKF estimation process. Secondly, a novel structure for the EKF observer is designed by adding a gain error coefficient solving section to the traditional EKF observer, which reduces the pulsations in estimated speed and rotor position caused by phase current gain errors, thereby improving estimation accuracy. Finally, simulations and experiments validate the feasibility of the proposed compensation method.
In the sensorless control system for interior permanent magnet synchronous motor based on the extended Kalman filter (EKF) approach, accurate estimation of motor speed and rotor position is important. To address the issue of decreased estimation accuracy for speed and rotor position due to phase current gain errors, a method for compensating position estimation errors is proposed. Firstly, through theoretical derivation, it is shown that phase current gain errors can cause estimated speed and rotor position to oscillate at twice the supply frequency during the EKF estimation process. Secondly, a novel structure for the EKF observer is designed by adding a gain error coefficient solving section to the traditional EKF observer, which reduces the pulsations in estimated speed and rotor position caused by phase current gain errors, thereby improving estimation accuracy. Finally, simulations and experiments validate the feasibility of the proposed compensation method.
2024, 51(8):30-38.
DOI: 10.12177/emca.2024.077
Abstract:
Internal short circuit (ISC) in lithium-ion batteries is the main cause of thermal runaway accidents, and early identification of ISC faults is crucial to reduce the risk associated with fire or explosion, and traditional detection methods based on filtered capacity increment curves are susceptible to interference. Aiming at the problem of how to extract the characteristic parameters on the capacity increment curve for early internal short circuit detection, a voltage reconstruction model based on the second-order RC equivalent circuit is proposed. Firstly, the capacity increment analysis of lithium battery is carried out using the traditional filtering method, and then the voltage reconstruction model is used for comparison. And the voltage reconstruction model is subjected to anti-noise interference experiments, and the error of the voltage reconstruction is only 0.000 8 V, which lays a foundation for the early internal short circuit detection work. Finally, experiments are carried out on publicly available experimental data to investigate the effects of different charging rates and different battery types on the capacity increment curve. Based on thus, the characteristic peaks used to diagnose short-circuit faults are obtained. The experimental results show that the proposed method based on voltage reconstruction model can effectively counteract noise interference and provide reference for early micro-inner short circuit detection.
Internal short circuit (ISC) in lithium-ion batteries is the main cause of thermal runaway accidents, and early identification of ISC faults is crucial to reduce the risk associated with fire or explosion, and traditional detection methods based on filtered capacity increment curves are susceptible to interference. Aiming at the problem of how to extract the characteristic parameters on the capacity increment curve for early internal short circuit detection, a voltage reconstruction model based on the second-order RC equivalent circuit is proposed. Firstly, the capacity increment analysis of lithium battery is carried out using the traditional filtering method, and then the voltage reconstruction model is used for comparison. And the voltage reconstruction model is subjected to anti-noise interference experiments, and the error of the voltage reconstruction is only 0.000 8 V, which lays a foundation for the early internal short circuit detection work. Finally, experiments are carried out on publicly available experimental data to investigate the effects of different charging rates and different battery types on the capacity increment curve. Based on thus, the characteristic peaks used to diagnose short-circuit faults are obtained. The experimental results show that the proposed method based on voltage reconstruction model can effectively counteract noise interference and provide reference for early micro-inner short circuit detection.
2024, 51(8):39-49.
DOI: 10.12177/emca.2024.078
Abstract:
Wind shear and tower shadow effects can lead to forced power oscillations in direct-drive wind turbines, affecting the safe and stable operation of the system. Thus, a virtual inertia control method based on active disturbance rejection control is proposed, which optimizes the control power of the wind turbine by estimating the system disturbance power through extended state observer observation. And at the same time, using tracking differentiator to adjust the reference value of the system frequency. Simulation results show that, compared with the traditional virtual inertia control, the proposed method has better immunity to disturbances, and can more effectively observe and estimate the disturbance and compensate for it, so as to achieve the purpose of suppressing the forced oscillation of direct drive wind power grid connected system.
Wind shear and tower shadow effects can lead to forced power oscillations in direct-drive wind turbines, affecting the safe and stable operation of the system. Thus, a virtual inertia control method based on active disturbance rejection control is proposed, which optimizes the control power of the wind turbine by estimating the system disturbance power through extended state observer observation. And at the same time, using tracking differentiator to adjust the reference value of the system frequency. Simulation results show that, compared with the traditional virtual inertia control, the proposed method has better immunity to disturbances, and can more effectively observe and estimate the disturbance and compensate for it, so as to achieve the purpose of suppressing the forced oscillation of direct drive wind power grid connected system.
2024, 51(8):50-58.
DOI: 10.12177/emca.2024.073
Abstract:
The principles of magnetic field modulation and axial magnetic gear composite motors are firstly systematically described. Based on thus, an axial magnetic gear composite motor with a spoke-type rotor structure is proposed. And the finite element analysis method is adopted to carry out three-dimensional numerical simulation analysis of the electromagnetic performance of the composite motor, which verifies the reasonableness of the structure of the motor. The influence of each parameter of the spoke-type rotor on the output torque and axial magnetic pulling force of the motor is further analyzed, and it is concluded that the influence of the rotor parameters on the circumferential and axial magnetic pulling force of the two sides of the rotor is similar, which provides a theoretical basis for subsequent experimental research.
The principles of magnetic field modulation and axial magnetic gear composite motors are firstly systematically described. Based on thus, an axial magnetic gear composite motor with a spoke-type rotor structure is proposed. And the finite element analysis method is adopted to carry out three-dimensional numerical simulation analysis of the electromagnetic performance of the composite motor, which verifies the reasonableness of the structure of the motor. The influence of each parameter of the spoke-type rotor on the output torque and axial magnetic pulling force of the motor is further analyzed, and it is concluded that the influence of the rotor parameters on the circumferential and axial magnetic pulling force of the two sides of the rotor is similar, which provides a theoretical basis for subsequent experimental research.
2024, 51(8):59-66.
DOI: 10.12177/emca.2024.080
Abstract:
With the increasing promotion of national energy conservation and emission reduction policies, hydropower, turbine power generation and wind power generation have developed rapidly, and various generators and motors are developing in the direction of high voltage and miniaturization. It is the key to reduce the volume of the motor at the same power, reduce the insulation size (including inter-turn insulation and main insulation) and increase the slot full rate. The reduction of insulation size is a contradiction with insulation quality and insulation reliability. Only a scientific and reasonable insulation structure can make the motor not only have excellent performance, but also meet the needs of larger power and smaller volume. The insulation thinning of high voltage motor can improve the heat dissipation capacity of main insulation, reduce the temperature rise of motor, and reduce the aging of insulation near copper wire caused by temperature rise. In addition, reducing the insulation thickness can increase the utilization rate of the slot, reduce the size of the motor under the same temperature rise, and reduce the copper consumption and mechanical energy consumption. High voltage motor insulation thinning is an important way to improve motor efficiency and reduce manufacturing costs, but to achieve insulation thinning, it is necessary to develop new high-performance insulation materials and optimize integrated insulation system, without reducing electrical insulation, aging and other properties of the premise of insulation thinning. Electromagnetic wire, mica tape with less glue, environmental protection epoxy vacuum pressure impregnation (VPI) resin and high resistance anti-halo material are studied, and integrated insulation system is optimized for systematic performance evaluation. The results show that the optimized 10 kV insulation system has the insulation thickness between turns 0.40 mm, the main insulation thickness 1.8 mm, the corona voltage ≥1.7 UN, and the electric aging life ≥350 h. At the same time, it has excellent electrical insulation performance and meets the technical requirements of high voltage motor.
With the increasing promotion of national energy conservation and emission reduction policies, hydropower, turbine power generation and wind power generation have developed rapidly, and various generators and motors are developing in the direction of high voltage and miniaturization. It is the key to reduce the volume of the motor at the same power, reduce the insulation size (including inter-turn insulation and main insulation) and increase the slot full rate. The reduction of insulation size is a contradiction with insulation quality and insulation reliability. Only a scientific and reasonable insulation structure can make the motor not only have excellent performance, but also meet the needs of larger power and smaller volume. The insulation thinning of high voltage motor can improve the heat dissipation capacity of main insulation, reduce the temperature rise of motor, and reduce the aging of insulation near copper wire caused by temperature rise. In addition, reducing the insulation thickness can increase the utilization rate of the slot, reduce the size of the motor under the same temperature rise, and reduce the copper consumption and mechanical energy consumption. High voltage motor insulation thinning is an important way to improve motor efficiency and reduce manufacturing costs, but to achieve insulation thinning, it is necessary to develop new high-performance insulation materials and optimize integrated insulation system, without reducing electrical insulation, aging and other properties of the premise of insulation thinning. Electromagnetic wire, mica tape with less glue, environmental protection epoxy vacuum pressure impregnation (VPI) resin and high resistance anti-halo material are studied, and integrated insulation system is optimized for systematic performance evaluation. The results show that the optimized 10 kV insulation system has the insulation thickness between turns 0.40 mm, the main insulation thickness 1.8 mm, the corona voltage ≥1.7 UN, and the electric aging life ≥350 h. At the same time, it has excellent electrical insulation performance and meets the technical requirements of high voltage motor.
2024, 51(8):67-75.
DOI: 10.12177/emca.2024.070
Abstract:
To address the fixed air-gap magnetic field of permanent magnet synchronous motors and the inefficiencies of traditional electrically excited motors, a novel parallel dual-rotor hybrid self-excited motor is introduced. Firstly, the proposed motor utilizing the harmonic excitation principle, it allows for flexible control of excitation current by adjusting harmonic voltage, which enhances speed control in medium and high-speed ranges. Secondly, under the premise of ensuring that the power remains unchanged, the proportion of each of the two parts is analyzed, and then the excitation source parameters are optimized and designed. Finally, the performance of the proposed motor is verified by adjusting the magnitude and direction of the excitation current and using the two-dimensional finite element model. The simulation results show that the proposed motor has a good ability to adjust the magnetism, and in the case of weak field, the amplitude of the back electromotive force is close to 0, which can effectively realize the speed adjustment.
To address the fixed air-gap magnetic field of permanent magnet synchronous motors and the inefficiencies of traditional electrically excited motors, a novel parallel dual-rotor hybrid self-excited motor is introduced. Firstly, the proposed motor utilizing the harmonic excitation principle, it allows for flexible control of excitation current by adjusting harmonic voltage, which enhances speed control in medium and high-speed ranges. Secondly, under the premise of ensuring that the power remains unchanged, the proportion of each of the two parts is analyzed, and then the excitation source parameters are optimized and designed. Finally, the performance of the proposed motor is verified by adjusting the magnitude and direction of the excitation current and using the two-dimensional finite element model. The simulation results show that the proposed motor has a good ability to adjust the magnetism, and in the case of weak field, the amplitude of the back electromotive force is close to 0, which can effectively realize the speed adjustment.
2024, 51(8):76-84.
DOI: 10.12177/emca.2024.079
Abstract:
During the operation of ultrasonic motors, the series resonant frequency of the motor may drift due to factors such as load and temperature rise. In order to achieve precise control of the motor, it is necessary to accurately identify and track the series resonant frequency of the motor. A series resonant frequency identification method for ultrasonic motors based on Butterworth-Van Dyke (BVD) equivalent circuit model of the motor is proposed. The driving voltage and current of the motor are used as feedback signals, which are then processed to obtain a differential voltage. The phase difference between the driving voltage and the differential voltage is compared. And the relationship between the phase difference and the series resonant frequency is analyzed. A circuit implementation scheme is designed and a physical circuit is manufactured. The series resonant frequency of the prototype motor is then identified with the proposed method. Moreover, the series resonant frequency of the motor is also measured with impedance analyzer. The result shows that the frequency identified with the proposed method is in good agreement with the measured one, which verifies the accuracy of the proposed series resonant frequency identification method for ultrasonic motors.
During the operation of ultrasonic motors, the series resonant frequency of the motor may drift due to factors such as load and temperature rise. In order to achieve precise control of the motor, it is necessary to accurately identify and track the series resonant frequency of the motor. A series resonant frequency identification method for ultrasonic motors based on Butterworth-Van Dyke (BVD) equivalent circuit model of the motor is proposed. The driving voltage and current of the motor are used as feedback signals, which are then processed to obtain a differential voltage. The phase difference between the driving voltage and the differential voltage is compared. And the relationship between the phase difference and the series resonant frequency is analyzed. A circuit implementation scheme is designed and a physical circuit is manufactured. The series resonant frequency of the prototype motor is then identified with the proposed method. Moreover, the series resonant frequency of the motor is also measured with impedance analyzer. The result shows that the frequency identified with the proposed method is in good agreement with the measured one, which verifies the accuracy of the proposed series resonant frequency identification method for ultrasonic motors.
2024, 51(8):85-96.
DOI: 10.12177/emca.2024.074
Abstract:
Aiming at the low harmonics caused by open winding permanent magnet synchronous motor (OW-PMSM) with the common DC bus, the adaptive notch filter (ANF) based on the least mean square (LMS) algorithm is adopted to control the 3rd, 5th, and 7th harmonics in the system. And, an ANF based on the LMS algorithm is used to suppress the 3rd, 5th and 7th harmonics in the system. Firstly, the mechanism of the low harmonics generation in the OW-PMSM is analyzed. Then, with the help of Matlab/Simulink, a 120° decoupling modulation strategy is explored to eliminate the zero-sequence currents caused by the modulation on the inverter side, and the ANF is used to extract the harmonics of the corresponding frequencies in the system, and the extracted harmonics are compensated into the current loop. More, the low harmonics caused by nonlinear factors are suppressed. Finally, the simulation and experimental results show that the contents of the 3rd, 5th, and 7th harmonics in the system are significantly reduced by adopting the ANF.
Aiming at the low harmonics caused by open winding permanent magnet synchronous motor (OW-PMSM) with the common DC bus, the adaptive notch filter (ANF) based on the least mean square (LMS) algorithm is adopted to control the 3rd, 5th, and 7th harmonics in the system. And, an ANF based on the LMS algorithm is used to suppress the 3rd, 5th and 7th harmonics in the system. Firstly, the mechanism of the low harmonics generation in the OW-PMSM is analyzed. Then, with the help of Matlab/Simulink, a 120° decoupling modulation strategy is explored to eliminate the zero-sequence currents caused by the modulation on the inverter side, and the ANF is used to extract the harmonics of the corresponding frequencies in the system, and the extracted harmonics are compensated into the current loop. More, the low harmonics caused by nonlinear factors are suppressed. Finally, the simulation and experimental results show that the contents of the 3rd, 5th, and 7th harmonics in the system are significantly reduced by adopting the ANF.
2024, 51(8):97-108.
DOI: 10.12177/emca.2024.075
Abstract:
The single-phase T-type three-level inverter is firstly applied to the electric spring with switchable smart load, which reduces the harmonic content of the load voltage and a mathematical model of the T-type three-level electric spring with switchable smart load is established. And, the influence of the traditional carrier modulation on the mid-point potential of the T-type three-level electric spring with switchable smart load on the DC side is derived, and the control scheme of the mid-point potential is introduced, which combines with the integral separation control idea to obtain the control strategy of the T-type three-level electric spring with switchable smart load. The control strategy can effectively reduce the overshoot of the load voltage during the fluctuation of the grid voltage. Finally, it is verified by Matlab/Simulink simulation that the improved harmonic content is reduced by 3.47% and 1.65%, and the overshoot is reduced by 0.34%and 0.1% when stabilizing the critical and non-critical load voltages.
The single-phase T-type three-level inverter is firstly applied to the electric spring with switchable smart load, which reduces the harmonic content of the load voltage and a mathematical model of the T-type three-level electric spring with switchable smart load is established. And, the influence of the traditional carrier modulation on the mid-point potential of the T-type three-level electric spring with switchable smart load on the DC side is derived, and the control scheme of the mid-point potential is introduced, which combines with the integral separation control idea to obtain the control strategy of the T-type three-level electric spring with switchable smart load. The control strategy can effectively reduce the overshoot of the load voltage during the fluctuation of the grid voltage. Finally, it is verified by Matlab/Simulink simulation that the improved harmonic content is reduced by 3.47% and 1.65%, and the overshoot is reduced by 0.34%and 0.1% when stabilizing the critical and non-critical load voltages.
12 Study on Voltage Balance and Ripple Suppression Strategy of Single-Phase Cascade H-bridge Rectifier
2024, 51(8):109-117.
DOI: 10.12177/emca.2024.071
Abstract:
The main circuit of the traditional single-phase cascade H-bridge rectifier is improved, the power decoupling arm is added, the mathematical model is established, and the voltage balance and ripple suppression strategies are studied. Firstly, the whole loop is controlled by double closed-loop, and the extraction scheme of fundamental signal is optimized by the second-order generalized integration method. Secondly, the power balance relationship of the system is derived, the primary relationship model of the grid-side current and the capacitance voltage squared is established, and the variable proportion link is introduced to effectively improve the robustness of the system to resist parameter changes. Then, the independent Buck-type active power decoupling control strategy is adopted, and the duty cycle of the decoupled bridge arm switch tube is distributed in real time by calculation, and an adaptive frequency selector is designed to separate the secondary ripple signal to realize the suppression of the secondary ripple voltage ripple of the DC bus. Finally, the experimental verification based on Matlab/Simulink software shows that the proposed method can effectively solve the problems of voltage balance and secondary ripple power suppression.
The main circuit of the traditional single-phase cascade H-bridge rectifier is improved, the power decoupling arm is added, the mathematical model is established, and the voltage balance and ripple suppression strategies are studied. Firstly, the whole loop is controlled by double closed-loop, and the extraction scheme of fundamental signal is optimized by the second-order generalized integration method. Secondly, the power balance relationship of the system is derived, the primary relationship model of the grid-side current and the capacitance voltage squared is established, and the variable proportion link is introduced to effectively improve the robustness of the system to resist parameter changes. Then, the independent Buck-type active power decoupling control strategy is adopted, and the duty cycle of the decoupled bridge arm switch tube is distributed in real time by calculation, and an adaptive frequency selector is designed to separate the secondary ripple signal to realize the suppression of the secondary ripple voltage ripple of the DC bus. Finally, the experimental verification based on Matlab/Simulink software shows that the proposed method can effectively solve the problems of voltage balance and secondary ripple power suppression.
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Electric Machines & Control Application ® 2025
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沪ICP备16038578号-3
Electric Machines & Control Application ® 2025
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
