为了准确评估孤岛检测的实际性能,在传统的反孤岛测试电路的基础上,给出一种带整流性负载的反孤岛测试电路。利用公共连接点(Point of Common Coupling,PCC)处功率流的规律,得出了功率不匹配度的表达式。在不同的功率不匹配度下,利用该...为了准确评估孤岛检测的实际性能,在传统的反孤岛测试电路的基础上,给出一种带整流性负载的反孤岛测试电路。利用公共连接点(Point of Common Coupling,PCC)处功率流的规律,得出了功率不匹配度的表达式。在不同的功率不匹配度下,利用该测试电路与传统的测试电路,分别对过/欠压、过/欠频以及电压谐波检测方法进行仿真分析与比较。仿真结果表明,整流性负载的存在会导致过/欠压、过/欠频检测方法的检测盲区(Non-Detection Zone,NDZ)发生偏移,且偏移程度与整流性负载电阻、滤波电容的大小有关;同时,带整流性负载的测试电路是有效和实用的。该测试电路能准确反映孤岛情况下电压谐波的实际响应特性,且电压谐波的大小与整流性负载电阻的大小有关。展开更多
High quality electric power supply is the prime goal in the modern power systems around the world.One of the main ways to achieve this is the protection of the system which needs to be fast,reliable and cost effective...High quality electric power supply is the prime goal in the modern power systems around the world.One of the main ways to achieve this is the protection of the system which needs to be fast,reliable and cost effective.The objective of this paper is to provide protection of equipments in low voltage(LV)distribution system and thereafter to avoid their failure due to abnormal operating conditions.The proposed device provides protection for industrial,commercial and residential equipments by monitoring under voltage,over voltage and over current conditions using microcontroller,transistor and other discrete components.The microcontroller is the heart of this protective device which performs the major control of the device.The designed circuit can withstand the loads and the set voltage range so as to supply the connected load for any voltage variation between 220 and 240 Volts.It can be used to protect loads such as refrigerator,TV,VCR/DVD player etc.against undesirable over and under voltage conditions as well as surges caused due to sudden failure of power supply mains.This device can also be used directly as standalone equipment between the supply mains and the load.The over/under voltage and over current cut-off with time delay provides over/under-voltage and over current protection and also protection against any transients.展开更多
One-cycle-controlled(OCC)inverters are suitable for small single-phase photovoltaic distributed-generator systems because of their simplicity,phase-locked-loop free structure,grid voltage sensor-less operation,and cos...One-cycle-controlled(OCC)inverters are suitable for small single-phase photovoltaic distributed-generator systems because of their simplicity,phase-locked-loop free structure,grid voltage sensor-less operation,and cost-effectiveness.Grid voltage sensor-less control helps reduce cost and increases reliability in operation.However various sensors are used for implementation of a protection mechanism.In this paper,a grid voltage sensorless protection scheme for OCC based single-phase inverter systems is proposed.The estimated value of voltage at point of common coupling(VPCC)is used for protecting the system during over/under voltage conditions of the grid,implementing of voltage ride through conditions,and for disconnecting the grid during islanded conditions.The VPCC is estimated from the measured inverter current,switching pulses,and the measured dc-link voltage using a second-order filter.Simulation and experimental studies are performed to verify the efficacy of the proposed voltage sensor-less protection mechanism triggered using estimated VPCC.展开更多
文摘为了准确评估孤岛检测的实际性能,在传统的反孤岛测试电路的基础上,给出一种带整流性负载的反孤岛测试电路。利用公共连接点(Point of Common Coupling,PCC)处功率流的规律,得出了功率不匹配度的表达式。在不同的功率不匹配度下,利用该测试电路与传统的测试电路,分别对过/欠压、过/欠频以及电压谐波检测方法进行仿真分析与比较。仿真结果表明,整流性负载的存在会导致过/欠压、过/欠频检测方法的检测盲区(Non-Detection Zone,NDZ)发生偏移,且偏移程度与整流性负载电阻、滤波电容的大小有关;同时,带整流性负载的测试电路是有效和实用的。该测试电路能准确反映孤岛情况下电压谐波的实际响应特性,且电压谐波的大小与整流性负载电阻的大小有关。
文摘High quality electric power supply is the prime goal in the modern power systems around the world.One of the main ways to achieve this is the protection of the system which needs to be fast,reliable and cost effective.The objective of this paper is to provide protection of equipments in low voltage(LV)distribution system and thereafter to avoid their failure due to abnormal operating conditions.The proposed device provides protection for industrial,commercial and residential equipments by monitoring under voltage,over voltage and over current conditions using microcontroller,transistor and other discrete components.The microcontroller is the heart of this protective device which performs the major control of the device.The designed circuit can withstand the loads and the set voltage range so as to supply the connected load for any voltage variation between 220 and 240 Volts.It can be used to protect loads such as refrigerator,TV,VCR/DVD player etc.against undesirable over and under voltage conditions as well as surges caused due to sudden failure of power supply mains.This device can also be used directly as standalone equipment between the supply mains and the load.The over/under voltage and over current cut-off with time delay provides over/under-voltage and over current protection and also protection against any transients.
基金supported by the Science and Engineering Research Board,Department of Science and Technology,Government of India,under Grant ECR/2016/000876.
文摘One-cycle-controlled(OCC)inverters are suitable for small single-phase photovoltaic distributed-generator systems because of their simplicity,phase-locked-loop free structure,grid voltage sensor-less operation,and cost-effectiveness.Grid voltage sensor-less control helps reduce cost and increases reliability in operation.However various sensors are used for implementation of a protection mechanism.In this paper,a grid voltage sensorless protection scheme for OCC based single-phase inverter systems is proposed.The estimated value of voltage at point of common coupling(VPCC)is used for protecting the system during over/under voltage conditions of the grid,implementing of voltage ride through conditions,and for disconnecting the grid during islanded conditions.The VPCC is estimated from the measured inverter current,switching pulses,and the measured dc-link voltage using a second-order filter.Simulation and experimental studies are performed to verify the efficacy of the proposed voltage sensor-less protection mechanism triggered using estimated VPCC.
