The hybrid dc circuit breaker(HCB)has the advantages of fast action speed and low operating loss,which is an idealmethod for fault isolation ofmulti-terminal dc grids.Formulti-terminal dc grids that transmit power thr...The hybrid dc circuit breaker(HCB)has the advantages of fast action speed and low operating loss,which is an idealmethod for fault isolation ofmulti-terminal dc grids.Formulti-terminal dc grids that transmit power through overhead lines,HCBs are required to have reclosing capability due to the high fault probability and the fact that most of the faults are temporary faults.To avoid the secondary fault strike and equipment damage that may be caused by the reclosing of the HCB when the permanent fault occurs,an adaptive reclosing scheme based on traveling wave injection is proposed in this paper.The scheme injects traveling wave signal into the fault dc line through the additionally configured auxiliary discharge branch in the HCB,and then uses the reflection characteristic of the traveling wave signal on the dc line to identify temporary and permanent faults,to be able to realize fast reclosing when the temporary fault occurs and reliably avoid reclosing after the permanent fault occurs.The test results in the simulation model of the four-terminal dc grid show that the proposed adaptive reclosing scheme can quickly and reliably identify temporary and permanent faults,greatly shorten the power outage time of temporary faults.In addition,it has the advantages of easiness to implement,high reliability,robustness to high-resistance fault and no dead zone,etc.展开更多
直流输电线路故障行波波速不确定、波头提取困难以及噪声干扰等因素制约了直流电网中故障测距技术的应用。为了降低上述因素对定位准确性的影响,提出一种基于局部特征有理样条插值均值分解(LMD based on characteristic rational spline...直流输电线路故障行波波速不确定、波头提取困难以及噪声干扰等因素制约了直流电网中故障测距技术的应用。为了降低上述因素对定位准确性的影响,提出一种基于局部特征有理样条插值均值分解(LMD based on characteristic rational spline,CRS-LMD)和奇异值分解(singular value decomposition,SVD)的故障测距方法。首先,利用特征尺度选取最优极点系数,结合有理样条插值调节拟合曲线的松紧程度,实现对故障电压行波的局部均值分解。其次,采用奇异值分解对故障行波波头进行准确提取。最后,在PSCAD/EMTDC中搭建了张北±500 kV柔性直流电网的仿真模型,模拟各种故障情况并输出故障数据,利用Matlab对故障数据进行处理并验证定位算法。最后,仿真结果表明,所提故障测距算法在不同故障距离和故障类型下均能实现故障测距,且在叠加噪声和过渡电阻的情况下也能保障较高的精确性。展开更多
Security constrained multi area multi objective dynamic economic dispatch (SCMAMODED) with renewable energy (RE) and all the possible MTDC stability constraints is formulated for the first time. The stability merits o...Security constrained multi area multi objective dynamic economic dispatch (SCMAMODED) with renewable energy (RE) and all the possible MTDC stability constraints is formulated for the first time. The stability merits of multi terminal DC (MTDC) tie lines as compared to the traditional HVAC forms the main objective of this paper. Probabilistic load flow (PLF) is applied to determine the system parameters while the uncertainties are modelled using Scenario Based Method (SBM). The simulation results reveal that with the use of MTDC tie lines, the frequency and voltage stability in the MAMODED with renewable energy sources (RES) are enhanced while keeping the MTDC power exchange interface nodes at secure levels.展开更多
模块化多电平换流器高压直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)由于具备自换相能力,尤其适用于向弱交流电网供电。交流系统强度降低时,会制约系统的直流功率传输能力,甚至导致系统失稳。...模块化多电平换流器高压直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)由于具备自换相能力,尤其适用于向弱交流电网供电。交流系统强度降低时,会制约系统的直流功率传输能力,甚至导致系统失稳。针对联接弱交流电网时MMC-HVDC系统功率传输受限的问题,建立了状态空间与直流阻抗模型,从时域、频域两方面研究了交流系统强度对直流功率传输能力的影响,明确了弱交流电网工况下功率传输受限的原因。基于参与因子定位结果,提出了在定直流电压控制环节引入直流电流反馈的功率传输能力提升方法,从时域、频域两方面对控制策略的提升作用进行了机理分析,并定量得出了控制参数的可行域及功率传输能力的最大提升水平。该方法在避免稳态误差的前提下,有效提升了MMC-HVDC系统的直流功率传输能力。展开更多
The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale...The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load;this ensures safe and stable operation of non-grid connected wind turbines.展开更多
Segmentation of large AC systems through DC links introduces a new concept that utilizes the advantages of direct current transmission to improve network reliability and increase power transfer capacity. Technical lit...Segmentation of large AC systems through DC links introduces a new concept that utilizes the advantages of direct current transmission to improve network reliability and increase power transfer capacity. Technical literature argues that the segmentation of the AC network and the introduction of DC links at these systems connection points bring benefits to system operation, once contingencies generated on one side of the DC connection point would not be reflected on the other side of DC connection, thereby reducing the likelihood of cascading shutdowns and blackouts due to load restraint on transmission lines and transformers. Amidst this scenario, this paper presents a study of the main topics regarding the use of this new network segmentation philosophy, bringing a practical point of view for the use of this concept at the electrical power system planning. The effect of DC segmentation before a contingency that would initiate major outages in an adapted electrical system model IEEE-14 bus is studied and simulations have been performed with test HVAC systems and segmented by HVDC link. The results have been compared, principally in relation to the voltage bus, reactive power generation, system losses and power flow at the lines, and demonstrated that this new concept improved the grid reliability.展开更多
如何对直流故障电流进行有效抑制是实现柔性直流电网大规模发展的关键。为此,研究模块化多电平变换器(modular multilevel converter,MMC)的控制方法,提出一种针对半桥型MMC的两段式限流保护策略,通过减少子模块的投入数目来降低换流站...如何对直流故障电流进行有效抑制是实现柔性直流电网大规模发展的关键。为此,研究模块化多电平变换器(modular multilevel converter,MMC)的控制方法,提出一种针对半桥型MMC的两段式限流保护策略,通过减少子模块的投入数目来降低换流站直流出口电压,达到限制短路电流的目的。首先,介绍MMC的拓扑结构及基于MMC的高压直流输电(MMC based high voltage direct current,MMC-HVDC)系统控制策略;其次,分析两段式限流保护策略的原理与直流故障电流特性,介绍MMC-HVDC系统的直流故障保护策略;最后,通过双端MMC-HVDC系统仿真实验,对所提限流保护策略的有效性进行验证。仿真结果表明,两段式限流保护策略可以有效降低断路器开断电流和吸收能量,节约成本。展开更多
China Southern Power Grid is a unique EHV AC/DC hybrid transmission network that operates in China. In its service area, the distribution of energy resources and the development of economy are extremely unbalanced, so...China Southern Power Grid is a unique EHV AC/DC hybrid transmission network that operates in China. In its service area, the distribution of energy resources and the development of economy are extremely unbalanced, so long-distance and bulk power transmission are needed; besides, the geography and climate conditions are serious, rains, fogs, lightning and typhoon as well as high temperature are common all the year round. Facing these challenges, the power grid enhanced stability control, improved the equipment and strengthen the network structure. In the future, the power grid plans to optimize the disposition of power sources and build digitalized power system.展开更多
Among the factors determining the performance of the new renewable energy system, the processing part of the untreated DC power is a very important element. In fact, the area where the loss of the new renewable energy...Among the factors determining the performance of the new renewable energy system, the processing part of the untreated DC power is a very important element. In fact, the area where the loss of the new renewable energy system is greatest is also the DC transmission and distribution technology. It is critical to prevent this loss and to improve the performance of the system, and analyze the performance of the resulting through the application of the resulting algorithms. In this thesis, we are discussing ways to calibrate the error in the PV distribution system within the solar power generation system using the Bypass Line Configuration Algorithm. I would like to note that if the operation of the Bypass Line device generates electrical abnormalities in the system’s circuits, it can recover the performance of the system, thereby improving performance.展开更多
Nowadays, the DC distribution system has been suggested, as a replacement for the AC power distribution system with electric propulsion. This idea signifies a fresh approach of issuing energy for low-voltage installat...Nowadays, the DC distribution system has been suggested, as a replacement for the AC power distribution system with electric propulsion. This idea signifies a fresh approach of issuing energy for low-voltage installations. It can be used for any electrical application up to 20 MW and works at a nominal voltage of 1000 V DC. The DC distribution system is just an extension of the multiple DC links that previously available in all propulsion and thruster drives, which typically comprise more than 80% of the electrical power consumption on electric propulsion vessels. A fault detection and islanding scheme for DC grid connected PV system is presented in this paper. Unlike traditional ac distribution systems, protection has been challenging for dc systems. The goals of this paper are to classify and detect the fault in the PV system as well as DC grid and to isolate the faulted section so that the system keeps operating without disabling the entire system. The results show the measured values of power at PV panel and DC grid side under different fault condition, which indicates the type of fault that occurs in the system.展开更多
Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can ...Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can be achieved. This paper presents a fuzzy logic control for dual active bridge series resonant converters for DC smart grid application. The DC smart grid consists of wind turbine and photovoltaic generators, controllable and DC loads, and power converters. The proposed control method has been applied to the controllable load＇s and the grid side＇s dual active bridge series resonant converters for attaining control of the power system. It has been used for management of controllable load＇s state of charge, DC feeder＇s voltage stability during the loads and power variations from wind energy and photovoltaic generation and power flow management between the grid side and the DC smart grid. The effectiveness of the proposed DC smart grid operation has been verified by simulation results obtained by using MATLAB and PLECS cards.展开更多
Renewable energy sources like solar,wind,and hydro are becoming increasingly popular due to the fewer negative impacts they have on the environment.Because,Since the production of renewable energy sources is still in ...Renewable energy sources like solar,wind,and hydro are becoming increasingly popular due to the fewer negative impacts they have on the environment.Because,Since the production of renewable energy sources is still in the process of being created,photovoltaic(PV)systems are commonly utilized for installation situations that are acceptable,clean,and simple.This study presents an adaptive artificial intelligence approach that can be used for maximum power point tracking(MPPT)in solar systems with the help of an embedded controller.The adaptive method incorporates both the Whale Optimization Algorithm(WOA)and the Artificial Neural Network(ANN).The WOA was implemented to enhance the process of the ANN model’s training,and the ANN model was developed using the WOA.In addition to this,the inverter circuit is connected to the smart grid system,and the strengthening of the smart grid is achieved through the implementation of the CMCMAC protocol.This protocol prevents interference between customers and the organizations that provide their utilities.Using a protocol known as Cross-Layer Multi-Channel MAC(CMCMAC),the effect of interference is removed using the way that was suggested.Also,with the utilization of the ZIGBEE communication technology,bidirectional communication is made possible.The strategy that was suggested has been put into practice,and the results have shown that the PV system produces an output power of 73.32 KW and an efficiency of 98.72%.In addition to this,a built-in regulator is utilized to validate the proposed model.In this paper,the results of various experiments are analyzed,and a comparison is made between the suggested WOA with the ANN controller approach and others,such as the Particle Swarm Optimization(PSO)based MPPT and the Cuckoo Search(CS)based MPPT.By examining the comparison findings,it was determined that the adaptive AI-based embedded controller was superior to the other alternatives.展开更多
基金supported by the Science and Technology Project of State Grid Corporation of China under Grant 520201210025。
文摘The hybrid dc circuit breaker(HCB)has the advantages of fast action speed and low operating loss,which is an idealmethod for fault isolation ofmulti-terminal dc grids.Formulti-terminal dc grids that transmit power through overhead lines,HCBs are required to have reclosing capability due to the high fault probability and the fact that most of the faults are temporary faults.To avoid the secondary fault strike and equipment damage that may be caused by the reclosing of the HCB when the permanent fault occurs,an adaptive reclosing scheme based on traveling wave injection is proposed in this paper.The scheme injects traveling wave signal into the fault dc line through the additionally configured auxiliary discharge branch in the HCB,and then uses the reflection characteristic of the traveling wave signal on the dc line to identify temporary and permanent faults,to be able to realize fast reclosing when the temporary fault occurs and reliably avoid reclosing after the permanent fault occurs.The test results in the simulation model of the four-terminal dc grid show that the proposed adaptive reclosing scheme can quickly and reliably identify temporary and permanent faults,greatly shorten the power outage time of temporary faults.In addition,it has the advantages of easiness to implement,high reliability,robustness to high-resistance fault and no dead zone,etc.
文摘直流输电线路故障行波波速不确定、波头提取困难以及噪声干扰等因素制约了直流电网中故障测距技术的应用。为了降低上述因素对定位准确性的影响,提出一种基于局部特征有理样条插值均值分解(LMD based on characteristic rational spline,CRS-LMD)和奇异值分解(singular value decomposition,SVD)的故障测距方法。首先,利用特征尺度选取最优极点系数,结合有理样条插值调节拟合曲线的松紧程度,实现对故障电压行波的局部均值分解。其次,采用奇异值分解对故障行波波头进行准确提取。最后,在PSCAD/EMTDC中搭建了张北±500 kV柔性直流电网的仿真模型,模拟各种故障情况并输出故障数据,利用Matlab对故障数据进行处理并验证定位算法。最后,仿真结果表明,所提故障测距算法在不同故障距离和故障类型下均能实现故障测距,且在叠加噪声和过渡电阻的情况下也能保障较高的精确性。
文摘Security constrained multi area multi objective dynamic economic dispatch (SCMAMODED) with renewable energy (RE) and all the possible MTDC stability constraints is formulated for the first time. The stability merits of multi terminal DC (MTDC) tie lines as compared to the traditional HVAC forms the main objective of this paper. Probabilistic load flow (PLF) is applied to determine the system parameters while the uncertainties are modelled using Scenario Based Method (SBM). The simulation results reveal that with the use of MTDC tie lines, the frequency and voltage stability in the MAMODED with renewable energy sources (RES) are enhanced while keeping the MTDC power exchange interface nodes at secure levels.
文摘模块化多电平换流器高压直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)由于具备自换相能力,尤其适用于向弱交流电网供电。交流系统强度降低时,会制约系统的直流功率传输能力,甚至导致系统失稳。针对联接弱交流电网时MMC-HVDC系统功率传输受限的问题,建立了状态空间与直流阻抗模型,从时域、频域两方面研究了交流系统强度对直流功率传输能力的影响,明确了弱交流电网工况下功率传输受限的原因。基于参与因子定位结果,提出了在定直流电压控制环节引入直流电流反馈的功率传输能力提升方法,从时域、频域两方面对控制策略的提升作用进行了机理分析,并定量得出了控制参数的可行域及功率传输能力的最大提升水平。该方法在避免稳态误差的前提下,有效提升了MMC-HVDC系统的直流功率传输能力。
文摘The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load;this ensures safe and stable operation of non-grid connected wind turbines.
文摘Segmentation of large AC systems through DC links introduces a new concept that utilizes the advantages of direct current transmission to improve network reliability and increase power transfer capacity. Technical literature argues that the segmentation of the AC network and the introduction of DC links at these systems connection points bring benefits to system operation, once contingencies generated on one side of the DC connection point would not be reflected on the other side of DC connection, thereby reducing the likelihood of cascading shutdowns and blackouts due to load restraint on transmission lines and transformers. Amidst this scenario, this paper presents a study of the main topics regarding the use of this new network segmentation philosophy, bringing a practical point of view for the use of this concept at the electrical power system planning. The effect of DC segmentation before a contingency that would initiate major outages in an adapted electrical system model IEEE-14 bus is studied and simulations have been performed with test HVAC systems and segmented by HVDC link. The results have been compared, principally in relation to the voltage bus, reactive power generation, system losses and power flow at the lines, and demonstrated that this new concept improved the grid reliability.
文摘如何对直流故障电流进行有效抑制是实现柔性直流电网大规模发展的关键。为此,研究模块化多电平变换器(modular multilevel converter,MMC)的控制方法,提出一种针对半桥型MMC的两段式限流保护策略,通过减少子模块的投入数目来降低换流站直流出口电压,达到限制短路电流的目的。首先,介绍MMC的拓扑结构及基于MMC的高压直流输电(MMC based high voltage direct current,MMC-HVDC)系统控制策略;其次,分析两段式限流保护策略的原理与直流故障电流特性,介绍MMC-HVDC系统的直流故障保护策略;最后,通过双端MMC-HVDC系统仿真实验,对所提限流保护策略的有效性进行验证。仿真结果表明,两段式限流保护策略可以有效降低断路器开断电流和吸收能量,节约成本。
文摘China Southern Power Grid is a unique EHV AC/DC hybrid transmission network that operates in China. In its service area, the distribution of energy resources and the development of economy are extremely unbalanced, so long-distance and bulk power transmission are needed; besides, the geography and climate conditions are serious, rains, fogs, lightning and typhoon as well as high temperature are common all the year round. Facing these challenges, the power grid enhanced stability control, improved the equipment and strengthen the network structure. In the future, the power grid plans to optimize the disposition of power sources and build digitalized power system.
文摘Among the factors determining the performance of the new renewable energy system, the processing part of the untreated DC power is a very important element. In fact, the area where the loss of the new renewable energy system is greatest is also the DC transmission and distribution technology. It is critical to prevent this loss and to improve the performance of the system, and analyze the performance of the resulting through the application of the resulting algorithms. In this thesis, we are discussing ways to calibrate the error in the PV distribution system within the solar power generation system using the Bypass Line Configuration Algorithm. I would like to note that if the operation of the Bypass Line device generates electrical abnormalities in the system’s circuits, it can recover the performance of the system, thereby improving performance.
文摘Nowadays, the DC distribution system has been suggested, as a replacement for the AC power distribution system with electric propulsion. This idea signifies a fresh approach of issuing energy for low-voltage installations. It can be used for any electrical application up to 20 MW and works at a nominal voltage of 1000 V DC. The DC distribution system is just an extension of the multiple DC links that previously available in all propulsion and thruster drives, which typically comprise more than 80% of the electrical power consumption on electric propulsion vessels. A fault detection and islanding scheme for DC grid connected PV system is presented in this paper. Unlike traditional ac distribution systems, protection has been challenging for dc systems. The goals of this paper are to classify and detect the fault in the PV system as well as DC grid and to isolate the faulted section so that the system keeps operating without disabling the entire system. The results show the measured values of power at PV panel and DC grid side under different fault condition, which indicates the type of fault that occurs in the system.
文摘Over the last few years, smart grids have become a topic of intensive research, development and deployment across the world. This is due to the fact that, through the smart grid, stable and reliable power systems can be achieved. This paper presents a fuzzy logic control for dual active bridge series resonant converters for DC smart grid application. The DC smart grid consists of wind turbine and photovoltaic generators, controllable and DC loads, and power converters. The proposed control method has been applied to the controllable load＇s and the grid side＇s dual active bridge series resonant converters for attaining control of the power system. It has been used for management of controllable load＇s state of charge, DC feeder＇s voltage stability during the loads and power variations from wind energy and photovoltaic generation and power flow management between the grid side and the DC smart grid. The effectiveness of the proposed DC smart grid operation has been verified by simulation results obtained by using MATLAB and PLECS cards.
基金funding this research work through the Small Group Research Project under Grant Number RGP1/70/44.
文摘Renewable energy sources like solar,wind,and hydro are becoming increasingly popular due to the fewer negative impacts they have on the environment.Because,Since the production of renewable energy sources is still in the process of being created,photovoltaic(PV)systems are commonly utilized for installation situations that are acceptable,clean,and simple.This study presents an adaptive artificial intelligence approach that can be used for maximum power point tracking(MPPT)in solar systems with the help of an embedded controller.The adaptive method incorporates both the Whale Optimization Algorithm(WOA)and the Artificial Neural Network(ANN).The WOA was implemented to enhance the process of the ANN model’s training,and the ANN model was developed using the WOA.In addition to this,the inverter circuit is connected to the smart grid system,and the strengthening of the smart grid is achieved through the implementation of the CMCMAC protocol.This protocol prevents interference between customers and the organizations that provide their utilities.Using a protocol known as Cross-Layer Multi-Channel MAC(CMCMAC),the effect of interference is removed using the way that was suggested.Also,with the utilization of the ZIGBEE communication technology,bidirectional communication is made possible.The strategy that was suggested has been put into practice,and the results have shown that the PV system produces an output power of 73.32 KW and an efficiency of 98.72%.In addition to this,a built-in regulator is utilized to validate the proposed model.In this paper,the results of various experiments are analyzed,and a comparison is made between the suggested WOA with the ANN controller approach and others,such as the Particle Swarm Optimization(PSO)based MPPT and the Cuckoo Search(CS)based MPPT.By examining the comparison findings,it was determined that the adaptive AI-based embedded controller was superior to the other alternatives.
