The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based curre...The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based current differential protection scheme.The d-axis current characteristics of inverter-interfaced distributed generators and synchronous generators are analyzed.The differential protection criterion using sampling values of the d-axis current component is then constructed.Compared to conventional phase-based current differential protection,the proposed protection reduces the number of required communication channels,and is suitable for distribution networks with inverter-interfaced distributed generators with complex fault characteristics.Finally,a 10 kV active distribution network model is built in the PSCAD platform and protection prototypes are developed in RTDS.Superior sensitivity and fast speed are verified by simulation and RTDS-based tests.展开更多
In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,...In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,and reliable.When the uncontrolled rectification stage ends,a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation,then the signal is transmitted to the three-phase inverter bridge.The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid.The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value,then the soft-start resistor is removed,which means the shock-free soft-start process is completed.Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper.展开更多
基金supported by China Southern Power Grid Technology Project.
文摘The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based current differential protection scheme.The d-axis current characteristics of inverter-interfaced distributed generators and synchronous generators are analyzed.The differential protection criterion using sampling values of the d-axis current component is then constructed.Compared to conventional phase-based current differential protection,the proposed protection reduces the number of required communication channels,and is suitable for distribution networks with inverter-interfaced distributed generators with complex fault characteristics.Finally,a 10 kV active distribution network model is built in the PSCAD platform and protection prototypes are developed in RTDS.Superior sensitivity and fast speed are verified by simulation and RTDS-based tests.
基金Supported by the Natural Science Foundation of Anhui Province(KJ2017A044).
文摘In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,and reliable.When the uncontrolled rectification stage ends,a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation,then the signal is transmitted to the three-phase inverter bridge.The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid.The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value,then the soft-start resistor is removed,which means the shock-free soft-start process is completed.Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper.
