Switched reluctance motor power converters are prone to open-circuit faults because it need to withstand large voltages and currents.Due to the small number of traditional asymmetrical half bridge topology switches,it...Switched reluctance motor power converters are prone to open-circuit faults because it need to withstand large voltages and currents.Due to the small number of traditional asymmetrical half bridge topology switches,it is difficult to carry out fault tolerant control when power converters has an open-circuit fault,resulting in larger output torque ripple.This paper presents a five-level power converter based on the traditional asymmetric half-bridge power converter.The five-level topology has more switching states and can work in multi-level mode.Based on the topology,different excitation and demagnetization voltages can be choose at different speeds.A fault-tolerance strategy is developed to decrease the influence of the open-circuit fault.The five-level power converter has four switches per phase,and two of them will be used in one of the operating mode.So the remaining two of the switches can be used for safe backup,enabling fault-tolerant control when an open-circuit occur.Since each phase of the five-level power converter proposed in this paper is independent of each other,a reasonable control strategy can be used to avoid the unbalance of the midpoint potential.Finally,the topology and fault-tolerant strategy proposed in this paper are verified by simulation and experiment.展开更多
The poor outdoor operating conditions of household photovoltaic(PV)make the power station prone to various faults.However,the dispersion of household PV installations often increases the difficulty and cost of operati...The poor outdoor operating conditions of household photovoltaic(PV)make the power station prone to various faults.However,the dispersion of household PV installations often increases the difficulty and cost of operation and maintenance(O&M).Although the remote monitoring and fault detection of a PV power station can be realized by the use of operation data,the particularity of a household power station also brings many problems to fault detection.In this study,we propose a shading fault detection method of household PV power based on inherent characteristics of monthly string current data mapping.The ideal current peak obtained by a new fitting method is used to normalize string current data.The current probability density function(PDF)at each time point is estimated by kernel density estimation(KDE).Through the normalized current data corresponding to the maximum probability density,the inherent characteristics of the strings are obtained,such that whether the strings have shading can be judged and the shading degree can then be evaluated.Not only are no additional sensors needed to collect environmental data,such as irradiation and temperature,but also simulating the detailed parameters of the power station is not required.The interference caused by meteorological factors can thus be eliminated,which can be easily used in old power stations and newly constructed power stations.The effectiveness and performance of the proposed shading fault detection method is verified by experimental data collected from the actual household PV power station.Index Terms-Data fitting,fault detection,household photovoltaic(PV),kernel density estimation(KDE),shading degree.展开更多
Real-time simulation of power electronics has been recognized by the industry as an effective tool for developing power electronic devices and systems.Since there is no energy transfer during the course of the usage,r...Real-time simulation of power electronics has been recognized by the industry as an effective tool for developing power electronic devices and systems.Since there is no energy transfer during the course of the usage,real-time simulation has a lot of advantages in the process of development and experimentation.From the perspective of real-time simulation,this paper focuses on the main problems in modeling accuracy,system bandwidth and stability,limitations on communication interface and energy interface,and the cost of platform construction.Finally,we provide further research directions.展开更多
A novel 12 voltage vector control strategy for switched reluctance motors(SRM)with a T-type three-level converter is proposed in this study.Based on a causal analysis of torque ripple under the control of conventional...A novel 12 voltage vector control strategy for switched reluctance motors(SRM)with a T-type three-level converter is proposed in this study.Based on a causal analysis of torque ripple under the control of conventional six voltage vectors,six new voltage vectors are added for further reduction of torque ripple.An optimized control rule is adopted based on the division method of the 12 new voltage vectors.A zero-voltage vector is used to adjust the duration of the 12 voltage vectors,the time of which is varied at different parts of the vector sectors according to the torque error.In addition,the windings are connected in a delta configuration,therefore,the number of connections between the converter and SRM is reduced.Finally,the results of MATLAB/Simulink and RT-LAB are presented to verify the validity of the proposed scheme.展开更多
Requirements of the Internet of things for the network includes the ability to monitor the equipment and devices.Nowadays,the reliability of a power electronics converter has raised concerns of both academia and indus...Requirements of the Internet of things for the network includes the ability to monitor the equipment and devices.Nowadays,the reliability of a power electronics converter has raised concerns of both academia and industry.In particular,power semiconductor devices are continuously exposed to excessive stress while being designed with high power handling capability and are considered as the most fragile component in power converters suffering from a high failure rate.Aiming to find an effective monitoring method which is also helpful for the Internet of Things and improve the reliability of a three-level neutral-point-clamped power inverter,an in-situ health monitoring method is proposed by harnessing the inverter operational characteristics and degradation sensitive electrical parameters to address the IGBT wire bonding faults.The zero voltage state provides an inherent redundant feature that allows for a power switch to be diagnosed during its normal operation in a neutralpoint-clamped power inverter.The proposed prognostic approach obtains both the wire bonding failure features and junction temperature from the terminals of an IGBT module,which is regarded as non-invasive on-line health monitoring.The system performance can be affected by the designated testing point and testing window,which is discussed and experimentally validated.The proposed technique allows unhealthy wire bonding in IGBT modules online monitoring during the operational period of the inverter.And the proposed in-situ health monitoring of IGBT modules can be used for the industrial Internet of things.展开更多
Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between...Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between supply and exhaust air volumes.The door gap is the channel of air flow between rooms,so its height has an important influence on the pressure difference and infiltration air volume of the room.There is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the building.In this study,model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM,and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases department.The results show that in a building with ventilation system divided by functional area,the difference in the height of the door gaps requires different active infiltration air volumes.Pressure fluctuations in the medical and patient corridors are greater than in other rooms.The significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 patients.It is also instructive for the design of pressure gradients in clean workshops,biological laboratories,and other similar buildings.展开更多
文摘Switched reluctance motor power converters are prone to open-circuit faults because it need to withstand large voltages and currents.Due to the small number of traditional asymmetrical half bridge topology switches,it is difficult to carry out fault tolerant control when power converters has an open-circuit fault,resulting in larger output torque ripple.This paper presents a five-level power converter based on the traditional asymmetric half-bridge power converter.The five-level topology has more switching states and can work in multi-level mode.Based on the topology,different excitation and demagnetization voltages can be choose at different speeds.A fault-tolerance strategy is developed to decrease the influence of the open-circuit fault.The five-level power converter has four switches per phase,and two of them will be used in one of the operating mode.So the remaining two of the switches can be used for safe backup,enabling fault-tolerant control when an open-circuit occur.Since each phase of the five-level power converter proposed in this paper is independent of each other,a reasonable control strategy can be used to avoid the unbalance of the midpoint potential.Finally,the topology and fault-tolerant strategy proposed in this paper are verified by simulation and experiment.
基金supported in part by the National Natural Science Foundation of China under Grant No.52061635101.
文摘The poor outdoor operating conditions of household photovoltaic(PV)make the power station prone to various faults.However,the dispersion of household PV installations often increases the difficulty and cost of operation and maintenance(O&M).Although the remote monitoring and fault detection of a PV power station can be realized by the use of operation data,the particularity of a household power station also brings many problems to fault detection.In this study,we propose a shading fault detection method of household PV power based on inherent characteristics of monthly string current data mapping.The ideal current peak obtained by a new fitting method is used to normalize string current data.The current probability density function(PDF)at each time point is estimated by kernel density estimation(KDE).Through the normalized current data corresponding to the maximum probability density,the inherent characteristics of the strings are obtained,such that whether the strings have shading can be judged and the shading degree can then be evaluated.Not only are no additional sensors needed to collect environmental data,such as irradiation and temperature,but also simulating the detailed parameters of the power station is not required.The interference caused by meteorological factors can thus be eliminated,which can be easily used in old power stations and newly constructed power stations.The effectiveness and performance of the proposed shading fault detection method is verified by experimental data collected from the actual household PV power station.Index Terms-Data fitting,fault detection,household photovoltaic(PV),kernel density estimation(KDE),shading degree.
基金supported by the National Natural Science Foundation of China(No.51707053)the Anhui Provincial Natural Science Foundation(No.1808085QE155)the Fundamental Research Funds for the Central Universities(No.JZ2019HGTB0080)
文摘Real-time simulation of power electronics has been recognized by the industry as an effective tool for developing power electronic devices and systems.Since there is no energy transfer during the course of the usage,real-time simulation has a lot of advantages in the process of development and experimentation.From the perspective of real-time simulation,this paper focuses on the main problems in modeling accuracy,system bandwidth and stability,limitations on communication interface and energy interface,and the cost of platform construction.Finally,we provide further research directions.
基金Supported by the National Natural Science Foundation of China(51977054).
文摘A novel 12 voltage vector control strategy for switched reluctance motors(SRM)with a T-type three-level converter is proposed in this study.Based on a causal analysis of torque ripple under the control of conventional six voltage vectors,six new voltage vectors are added for further reduction of torque ripple.An optimized control rule is adopted based on the division method of the 12 new voltage vectors.A zero-voltage vector is used to adjust the duration of the 12 voltage vectors,the time of which is varied at different parts of the vector sectors according to the torque error.In addition,the windings are connected in a delta configuration,therefore,the number of connections between the converter and SRM is reduced.Finally,the results of MATLAB/Simulink and RT-LAB are presented to verify the validity of the proposed scheme.
基金This work was supported by National Natural Science Foundation of China(U1834204).
文摘Requirements of the Internet of things for the network includes the ability to monitor the equipment and devices.Nowadays,the reliability of a power electronics converter has raised concerns of both academia and industry.In particular,power semiconductor devices are continuously exposed to excessive stress while being designed with high power handling capability and are considered as the most fragile component in power converters suffering from a high failure rate.Aiming to find an effective monitoring method which is also helpful for the Internet of Things and improve the reliability of a three-level neutral-point-clamped power inverter,an in-situ health monitoring method is proposed by harnessing the inverter operational characteristics and degradation sensitive electrical parameters to address the IGBT wire bonding faults.The zero voltage state provides an inherent redundant feature that allows for a power switch to be diagnosed during its normal operation in a neutralpoint-clamped power inverter.The proposed prognostic approach obtains both the wire bonding failure features and junction temperature from the terminals of an IGBT module,which is regarded as non-invasive on-line health monitoring.The system performance can be affected by the designated testing point and testing window,which is discussed and experimentally validated.The proposed technique allows unhealthy wire bonding in IGBT modules online monitoring during the operational period of the inverter.And the proposed in-situ health monitoring of IGBT modules can be used for the industrial Internet of things.
文摘Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between supply and exhaust air volumes.The door gap is the channel of air flow between rooms,so its height has an important influence on the pressure difference and infiltration air volume of the room.There is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the building.In this study,model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM,and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases department.The results show that in a building with ventilation system divided by functional area,the difference in the height of the door gaps requires different active infiltration air volumes.Pressure fluctuations in the medical and patient corridors are greater than in other rooms.The significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 patients.It is also instructive for the design of pressure gradients in clean workshops,biological laboratories,and other similar buildings.
