Decreasing costs and favorable policies have resulted in increased penetration of solar photovoltaic(PV)power generation in distribution networks.As the PV systems penetration is likely to increase in the future,utili...Decreasing costs and favorable policies have resulted in increased penetration of solar photovoltaic(PV)power generation in distribution networks.As the PV systems penetration is likely to increase in the future,utilizing the reactive power capability of PV inverters to mitigate voltage deviations is being promoted.In recent years,droop control of inverter-based distributed energy resources has emerged as an essential tool for use in this study.The participation of PV systems in voltage regulation and its coordination with existing controllers,such as on-load tap changers,is paramount for controlling the voltage within specified limits.In this work,control strategies are presented that can be coordinated with the existing controls in a distributed manner.The effectiveness of the proposed method was demonstrated through simulation results on a distribution system.展开更多
At present, an automatic-mechanic contact tap-changer is widely used in power system, but it can not frequently operate. In addition, arc will occur when the switch changes. In order to solve these two problems, this ...At present, an automatic-mechanic contact tap-changer is widely used in power system, but it can not frequently operate. In addition, arc will occur when the switch changes. In order to solve these two problems, this paper presented an automatic on-load voltage-regulating distributing transformer which employed non-contact solid-state relay as tap-changer, and mainly introduced its structure, basic principal, design method of each key link and experimental results. Laboratory simulation experiments informed that the scheme was feasible. It was a smooth and effective experiment device, which was practical in application.展开更多
The continuous operation of On-Load Tap-Changers (OLTC) is essential for maintaining stable voltage levels in power transmission and distribution systems. Timely fault detection in OLTC is essential for preventing maj...The continuous operation of On-Load Tap-Changers (OLTC) is essential for maintaining stable voltage levels in power transmission and distribution systems. Timely fault detection in OLTC is essential for preventing major failures and ensuring the reliability of the electrical grid. This research paper proposes an innovative approach that combines voiceprint detection using MATLAB analysis for online fault monitoring of OLTC. By leveraging advanced signal processing techniques and machine learning algorithms in MATLAB, the proposed method accurately detects faults in OLTC, providing real-time monitoring and proactive maintenance strategies.展开更多
Distribution networks have been experiencing significant changes under the pressure of the energy transition.The high integration of renewable energy sources combined with the electrification process introduces new ch...Distribution networks have been experiencing significant changes under the pressure of the energy transition.The high integration of renewable energy sources combined with the electrification process introduces new challenges in managing distribution networks.Innovative solutions aimed at optimizing the control of complex problems,starting from historical data instead of a detailed system model,have been growing due to rapid development in artificial intelligence and machine learning.This paper proposes a Q-learning algorithm to control the tap setting of the on-load tap changer installed in primary substation transformers.The ultimate goal is to maintain voltage magnitudes at all busses of the medium-voltage distribution network within a safe range,simultaneously optimizing on-load tap changer operations.As a case study,the effectiveness of the proposed algorithm is assessed using a real medium-voltage distribution network with high penetration of renewable energy sources that supplies more than 2500 users/prosumers.The ability of the proposed algorithm to control bus voltages is tested in several scenarios characterized by significant variability and uncertainty.Outcomes show that the proposed algorithm is suitable for optimizing voltage control in distribution networks using a data-driven approach.展开更多
As one of the key components of a UHV converter transformer,the suitable switching condition of the vacuum onload tap changer(OLTC)is essential for the stability of the power system.It is highly desirable to interpret...As one of the key components of a UHV converter transformer,the suitable switching condition of the vacuum onload tap changer(OLTC)is essential for the stability of the power system.It is highly desirable to interpret OLTC’s switching procedure to assess OLTC’s switching condition.However,such work can’t be solved by vibration analysis alone.Therefore,this paper proposes an innovative electromechanical comprehensive analysis method.First,a joint motor drive current,vibration,and electromagnetic signals online monitoring system is established and deployed in a VRG type OLTC in±800 kV converter station.Second,independent component analysis(ICA),dynamic time warping(DTW),and wavelet transform(WT)are used for processing motor current,UHFCT,and vibration signals,respectively,to extract electromechanical pulses corresponding to OLTC’s contact actions.Third,the switching procedure of OLTC is revealed by comprehensively analyzing the corresponding time relationship between these extracted pulses,combined with OLTC’s timing sequence.The methodologies developed in this paper can help to interpret OLTC’s switching procedure for deeper and finer online condition assessment.展开更多
In addressing voltage overruns and line lossesin distribution networks with a high percentage of distributed photovoltaic(PV)connections,traditional on-load regulator transformers can achieve only fixed-step voltage r...In addressing voltage overruns and line lossesin distribution networks with a high percentage of distributed photovoltaic(PV)connections,traditional on-load regulator transformers can achieve only fixed-step voltage regulation and have a limited switching lifespan.Consequently,a discrete-continuous two-layer optimization methodology for distribution networks,which accounts for power-converter-embeddedhybrid on-load regulator transformers,has been proposed to adapt to rapid stochastic fluctuations associatedwith distribution networks having a high percentage of PV access.In the discrete layer,the mechanical ratio is employed as the decision variable at each moment.In the continuous layer,the power electronic converterratio,STATCOM compensation capacity,and energy storage charging and discharging power are utilized as decision variables at each moment.Acomposite optimal allocation model is established with an integrated objective function comprising the PV consumption rate,operating costs,and line losses,while simultaneously ensuring that the voltage at each node remains within the prescribed limits.Based on this model,an improved particle swarm algorithm is employed to determine the optimalconfiguration.Finally,the efficacy of the proposed method is validated through enhancements of the IEEE33node system example.展开更多
This paper proposes an on-load voltage distortion compensation method,in which the voltage distortion is mainly produced in the surface-mounted permanent magnet machines having closed slot.Apart from the voltage disto...This paper proposes an on-load voltage distortion compensation method,in which the voltage distortion is mainly produced in the surface-mounted permanent magnet machines having closed slot.Apart from the voltage distortions caused by the inverter,such as dead time and inverter non-linearity,the on-load voltage distortion has relatively large magnitude dependent of machine speed.As a result,it causes a significant distortion of current waveforms and deteriorates control performance.Hence,a voltage disturbance compensation method using a disturbance observer is proposed and implemented.Based on the machine model,the disturbance observer is chosen which helps to observe a voltage disturbance,while the error between measured and estimated currents is minimized.The disturbance observer only compensates the sixth-multiple harmonic components of the inverter voltage in synchronous reference frame.The harmonic compensator with multiple narrow-band pass based adaptive filter is proposed and implemented in the feedback loop with current controllers.The observed voltage disturbances are compensated to the reference voltages.In addition,robust performance of the proposed method is shown against the parameter uncertainties.The effectiveness of the proposed compensation scheme is validated by the experiments.展开更多
With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs durin...With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process.This erosion causes significant wear on the contacts,thereby reducing their lifespan.Therefore,the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs.To achieve this,a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures.Additionally,finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy.The surface morphology of the contacts was observed using an optical microscope.The findings revealed that as the sliding speed increased,the arc energy,arc initiation rate,and contact resistance initially exhibited an upward trend,then decreased,and eventually increased again.The minimum values were observed at a sliding speed of 90 mm/s.Moreover,the arc energy,arc initiation rate,and contact resistance decreased gradually as the contact pressure increased.After reaching a contact pressure of 1.5 N,the variation in the arc energy stabilized.At lower contact pressures,arc erosion dominated the wear on the contact surface.However,at higher contact pressures,the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion.In summary,experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion,contact resistance,and surface damage of OLTC contacts in oil-immersed systems.展开更多
基金by a project under the scheme entitled“Developing Policies&Adaptation Strategies to Climate Change in the Baltic Sea Region”(ASTRA),Project No.ASTRA6-4(2014-2020.4.01.16-0032).
文摘Decreasing costs and favorable policies have resulted in increased penetration of solar photovoltaic(PV)power generation in distribution networks.As the PV systems penetration is likely to increase in the future,utilizing the reactive power capability of PV inverters to mitigate voltage deviations is being promoted.In recent years,droop control of inverter-based distributed energy resources has emerged as an essential tool for use in this study.The participation of PV systems in voltage regulation and its coordination with existing controllers,such as on-load tap changers,is paramount for controlling the voltage within specified limits.In this work,control strategies are presented that can be coordinated with the existing controls in a distributed manner.The effectiveness of the proposed method was demonstrated through simulation results on a distribution system.
文摘At present, an automatic-mechanic contact tap-changer is widely used in power system, but it can not frequently operate. In addition, arc will occur when the switch changes. In order to solve these two problems, this paper presented an automatic on-load voltage-regulating distributing transformer which employed non-contact solid-state relay as tap-changer, and mainly introduced its structure, basic principal, design method of each key link and experimental results. Laboratory simulation experiments informed that the scheme was feasible. It was a smooth and effective experiment device, which was practical in application.
文摘The continuous operation of On-Load Tap-Changers (OLTC) is essential for maintaining stable voltage levels in power transmission and distribution systems. Timely fault detection in OLTC is essential for preventing major failures and ensuring the reliability of the electrical grid. This research paper proposes an innovative approach that combines voiceprint detection using MATLAB analysis for online fault monitoring of OLTC. By leveraging advanced signal processing techniques and machine learning algorithms in MATLAB, the proposed method accurately detects faults in OLTC, providing real-time monitoring and proactive maintenance strategies.
基金supported by the Research Fund for the Italian Electrical System under the Three-Year Research Plan 2022-2024(DM MITE No.337,15.09.2022),in compliance with the Decree of April 16,2018.
文摘Distribution networks have been experiencing significant changes under the pressure of the energy transition.The high integration of renewable energy sources combined with the electrification process introduces new challenges in managing distribution networks.Innovative solutions aimed at optimizing the control of complex problems,starting from historical data instead of a detailed system model,have been growing due to rapid development in artificial intelligence and machine learning.This paper proposes a Q-learning algorithm to control the tap setting of the on-load tap changer installed in primary substation transformers.The ultimate goal is to maintain voltage magnitudes at all busses of the medium-voltage distribution network within a safe range,simultaneously optimizing on-load tap changer operations.As a case study,the effectiveness of the proposed algorithm is assessed using a real medium-voltage distribution network with high penetration of renewable energy sources that supplies more than 2500 users/prosumers.The ability of the proposed algorithm to control bus voltages is tested in several scenarios characterized by significant variability and uncertainty.Outcomes show that the proposed algorithm is suitable for optimizing voltage control in distribution networks using a data-driven approach.
基金supported by the Science and Technology Project of State Grid Corporation of China(NO.5500-202016076A-0-0-00).
文摘As one of the key components of a UHV converter transformer,the suitable switching condition of the vacuum onload tap changer(OLTC)is essential for the stability of the power system.It is highly desirable to interpret OLTC’s switching procedure to assess OLTC’s switching condition.However,such work can’t be solved by vibration analysis alone.Therefore,this paper proposes an innovative electromechanical comprehensive analysis method.First,a joint motor drive current,vibration,and electromagnetic signals online monitoring system is established and deployed in a VRG type OLTC in±800 kV converter station.Second,independent component analysis(ICA),dynamic time warping(DTW),and wavelet transform(WT)are used for processing motor current,UHFCT,and vibration signals,respectively,to extract electromechanical pulses corresponding to OLTC’s contact actions.Third,the switching procedure of OLTC is revealed by comprehensively analyzing the corresponding time relationship between these extracted pulses,combined with OLTC’s timing sequence.The methodologies developed in this paper can help to interpret OLTC’s switching procedure for deeper and finer online condition assessment.
基金Supported by the National Key Research and Development Program of China(2023YFB2405905)the National Natural Science Foundation of China(72371037,72061147004,72342001)+1 种基金the Shandong Energy Institute(SEI U202310)the Science and Technology Projects of Hunan Province(2023JJ30049,2023JJ50312,2023JJ50010,2024RC9012,2024Kfjj04).
文摘In addressing voltage overruns and line lossesin distribution networks with a high percentage of distributed photovoltaic(PV)connections,traditional on-load regulator transformers can achieve only fixed-step voltage regulation and have a limited switching lifespan.Consequently,a discrete-continuous two-layer optimization methodology for distribution networks,which accounts for power-converter-embeddedhybrid on-load regulator transformers,has been proposed to adapt to rapid stochastic fluctuations associatedwith distribution networks having a high percentage of PV access.In the discrete layer,the mechanical ratio is employed as the decision variable at each moment.In the continuous layer,the power electronic converterratio,STATCOM compensation capacity,and energy storage charging and discharging power are utilized as decision variables at each moment.Acomposite optimal allocation model is established with an integrated objective function comprising the PV consumption rate,operating costs,and line losses,while simultaneously ensuring that the voltage at each node remains within the prescribed limits.Based on this model,an improved particle swarm algorithm is employed to determine the optimalconfiguration.Finally,the efficacy of the proposed method is validated through enhancements of the IEEE33node system example.
基金Supported by Guangdong Welling Motor Manufacturing Co.,Ltd and Guangdong Innovative Research Team Program(No.2011N084),China。
文摘This paper proposes an on-load voltage distortion compensation method,in which the voltage distortion is mainly produced in the surface-mounted permanent magnet machines having closed slot.Apart from the voltage distortions caused by the inverter,such as dead time and inverter non-linearity,the on-load voltage distortion has relatively large magnitude dependent of machine speed.As a result,it causes a significant distortion of current waveforms and deteriorates control performance.Hence,a voltage disturbance compensation method using a disturbance observer is proposed and implemented.Based on the machine model,the disturbance observer is chosen which helps to observe a voltage disturbance,while the error between measured and estimated currents is minimized.The disturbance observer only compensates the sixth-multiple harmonic components of the inverter voltage in synchronous reference frame.The harmonic compensator with multiple narrow-band pass based adaptive filter is proposed and implemented in the feedback loop with current controllers.The observed voltage disturbances are compensated to the reference voltages.In addition,robust performance of the proposed method is shown against the parameter uncertainties.The effectiveness of the proposed compensation scheme is validated by the experiments.
文摘With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process.This erosion causes significant wear on the contacts,thereby reducing their lifespan.Therefore,the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs.To achieve this,a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures.Additionally,finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy.The surface morphology of the contacts was observed using an optical microscope.The findings revealed that as the sliding speed increased,the arc energy,arc initiation rate,and contact resistance initially exhibited an upward trend,then decreased,and eventually increased again.The minimum values were observed at a sliding speed of 90 mm/s.Moreover,the arc energy,arc initiation rate,and contact resistance decreased gradually as the contact pressure increased.After reaching a contact pressure of 1.5 N,the variation in the arc energy stabilized.At lower contact pressures,arc erosion dominated the wear on the contact surface.However,at higher contact pressures,the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion.In summary,experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion,contact resistance,and surface damage of OLTC contacts in oil-immersed systems.
