Islanding refers to a condition where distributed generators(DGs)inject power solely to the local load after electrical separation from power grid.Several islanding detection methods(IDMs)categorized into remote,activ...Islanding refers to a condition where distributed generators(DGs)inject power solely to the local load after electrical separation from power grid.Several islanding detection methods(IDMs)categorized into remote,active,and passive groups have been reported to detect this undesirable state.In active techniques,a disturbance is injected into the DG’s controller to drift a local yardstick out of the permissible range.Although this disturbance leads to more effective detections even in well-balanced island,it raises the total harmonic distortion(THD)of the output current under the normal operation conditions.This paper analyzes the power quality aspect of the modified sliding mode controller as a new active IDM for grid-connected photovoltaic system(GCPVS)with a string inverter.Its performance is compared with the voltage positive feedback(VPF)method,a well-known active IDM.This evaluation is carried out for a 1 k Wp GCPVS in MATLAB/Simulink platform by measuring the output current harmonics and THD as well as the efficiency under various penetration and disturbance levels.The output results demonstrate that since the proposed disturbance changes the amplitude of the output current,it does not generate harmonics/subharmonics.Thereby,it has a negligible adverse effect on power quality.It is finally concluded that the performance of the sliding mode-based IDM is reliable from the standpoints of islanding detection and power quality.展开更多
Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids.Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintai...Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids.Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintained dur-ing the operation of VSC-MTDC systems,particularly in post-contingency conditions.The traditional droop control methods cannot satisfy these requirements,and accordingly,this paper proposes a novel centralized control strategy based on a look-up table to ensure optimal power sharing and minimum DC voltage deviation immediately during post-contingency conditions by considering converter limits.It also reduces destructive effects(e.g.,frequency devia-tion)on onshore AC grids and guarantees the stable operation of the entire MTDC system.The proposed look-up table is an array of data that relates operating conditions to optimal droop coefficients and is determined according to N-1 contingency analysis and a linearized system model.Stability constraints and contingencies such as wind power changes,converter outage,and DC line disconnection are considered in its formation procedure.Simulations performed on a 4-terminal VSC-MTDC system in the MATLAB-Simulink environment validate the effectiveness and superiority of the proposed control strategy.展开更多
Monkeypox(Mpox)has posed a novel challenge and emerged as a threat to global public health since the onset of its outbreak in 2022.Mpox is spreading throughout the world in both endemic and non-endemic countries,indic...Monkeypox(Mpox)has posed a novel challenge and emerged as a threat to global public health since the onset of its outbreak in 2022.Mpox is spreading throughout the world in both endemic and non-endemic countries,indicating that its behavior is evolving.The prevalence of Mpox and the risk of a global pandemic necessitate a better understanding of Mpox virus replications and interactions with the host.Here,we attempted to provide a detailed comprehensive review of Mpox virus behavior at the molecular level from the entry level to the establishment of a successful infection,including attachment and entry,DNA replication,protein expression and viron assembly and egress.This review also describes its strategies to evade host immune responses and inhibit apoptosis,and uncovers underlying molecular mechanisms such as subverted signaling pathways and cellular factors behind host-viral interactions.展开更多
文摘Islanding refers to a condition where distributed generators(DGs)inject power solely to the local load after electrical separation from power grid.Several islanding detection methods(IDMs)categorized into remote,active,and passive groups have been reported to detect this undesirable state.In active techniques,a disturbance is injected into the DG’s controller to drift a local yardstick out of the permissible range.Although this disturbance leads to more effective detections even in well-balanced island,it raises the total harmonic distortion(THD)of the output current under the normal operation conditions.This paper analyzes the power quality aspect of the modified sliding mode controller as a new active IDM for grid-connected photovoltaic system(GCPVS)with a string inverter.Its performance is compared with the voltage positive feedback(VPF)method,a well-known active IDM.This evaluation is carried out for a 1 k Wp GCPVS in MATLAB/Simulink platform by measuring the output current harmonics and THD as well as the efficiency under various penetration and disturbance levels.The output results demonstrate that since the proposed disturbance changes the amplitude of the output current,it does not generate harmonics/subharmonics.Thereby,it has a negligible adverse effect on power quality.It is finally concluded that the performance of the sliding mode-based IDM is reliable from the standpoints of islanding detection and power quality.
文摘Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids.Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintained dur-ing the operation of VSC-MTDC systems,particularly in post-contingency conditions.The traditional droop control methods cannot satisfy these requirements,and accordingly,this paper proposes a novel centralized control strategy based on a look-up table to ensure optimal power sharing and minimum DC voltage deviation immediately during post-contingency conditions by considering converter limits.It also reduces destructive effects(e.g.,frequency devia-tion)on onshore AC grids and guarantees the stable operation of the entire MTDC system.The proposed look-up table is an array of data that relates operating conditions to optimal droop coefficients and is determined according to N-1 contingency analysis and a linearized system model.Stability constraints and contingencies such as wind power changes,converter outage,and DC line disconnection are considered in its formation procedure.Simulations performed on a 4-terminal VSC-MTDC system in the MATLAB-Simulink environment validate the effectiveness and superiority of the proposed control strategy.
文摘Monkeypox(Mpox)has posed a novel challenge and emerged as a threat to global public health since the onset of its outbreak in 2022.Mpox is spreading throughout the world in both endemic and non-endemic countries,indicating that its behavior is evolving.The prevalence of Mpox and the risk of a global pandemic necessitate a better understanding of Mpox virus replications and interactions with the host.Here,we attempted to provide a detailed comprehensive review of Mpox virus behavior at the molecular level from the entry level to the establishment of a successful infection,including attachment and entry,DNA replication,protein expression and viron assembly and egress.This review also describes its strategies to evade host immune responses and inhibit apoptosis,and uncovers underlying molecular mechanisms such as subverted signaling pathways and cellular factors behind host-viral interactions.
