Abstract: The present invention proposes a multi-terminal differential protection setting method for a distributed generator T-connected distribution network. The present invention can accurately identify internal faults and external faults of the protected area in the high-proportion distributed generator T-connected distribution network, with sufficient reliability and sensitivity.

Abstract: The present invention proposes a multi-terminal differential protection setting method for a distributed generator T-connected distribution network. The present invention can accurately identify internal faults and external faults of the protected area in the high-proportion distributed generator T-connected distribution network, with sufficient reliability and sensitivity.

Abstract: The invention discloses an islanding detection method in DC microgrids based on MPPT trapezoidal voltage disturbance. The steps are as follows: start the MPPT strategy; set the starting signal threshold of disturbance; measure the output current of PVA at the maximum power; calculate the same environmental factor of PVA with different capacities under the same light intensity and temperature in real time; when the environmental factor is greater than the starting signal threshold of the disturbance, periodic trapezoidal disturbance is carried out to the PVA port voltage reference; if the PCC voltage Upcc exceeds the threshold set by the passive method, it is judged as islanding; otherwise, it is judged whether the change rule of Upcc is consistent with the change rule of the calculated PCC voltage Upccp under the trapezoidal disturbance; If it is consistent, it is judged as islanding; otherwise, it is pseudo islanding.

Abstract: The invention discloses an adaptive fault clearing scheme for an MMC VSC-HVDC grid based on source-grid coordination. A grid-side circuit breaker topology is disposed at each end of each DC line of the MMC VSC-HVDC grid to coordinate with a source-side control strategy when a fault occurs to the DC line so as to isolate the fault together. When a system runs stably, the voltage regulation controller does not actuate, after the fault occurs, the voltage regulation controller is started, and the output voltage regulation coefficient decreases, so that voltage at outlets of the converters drops accordingly, and coordinates with voltage of the pre-charging capacitor of the grid-side circuit breaker topology to realize fault isolation based on source-grid coordination. The adaptive fault clearing scheme provided by the invention greatly improves the speed of fault isolation.

Abstract: The present invention related to the field of power system protection and control, presents a voltage travelling wave differential protection method considering the influence of frequency-dependent parameters, which provides more accurate and rapid fault identification. The technical scheme of the present invention is as follows: a calculation method of voltage travelling-wave differential protection for VSC-HVDC transmission lines, taking the influence of the frequency-dependent parameters into consideration, the steps are as follows: calculating a characteristic impedance and propagation coefficient of the frequency-dependent transmission line in time domain, collecting voltage and current signals at the both ends of the transmission line and then calculating the forward and backward voltage travelling wave, respectively, comparing a differential value of voltage travelling wave with a preset threshold value to determine whether the internal fault occurs.

Abstract: The invention discloses an adaptive fault clearing scheme for an MMC VSC-HVDC grid based on source-grid coordination. A grid-side circuit breaker topology is disposed at each end of each DC line of the MMC VSC-HVDC grid to coordinate with a source-side control strategy when a fault occurs to the DC line so as to isolate the fault together. When a system runs stably, the voltage regulation controller does not actuate, after the fault occurs, the voltage regulation controller is started, and the output voltage regulation coefficient decreases, so that voltage at outlets of the converters drops accordingly, and coordinates with voltage of the pre-charging capacitor of the grid-side circuit breaker topology to realize fault isolation based on source-grid coordination. The adaptive fault clearing scheme provided by the invention greatly improves the speed of fault isolation.

Abstract: The invention discloses an islanding detection method in DC microgrids based on MPPT trapezoidal voltage disturbance. The steps are as follows: start the MPPT strategy; set the starting signal threshold of disturbance; measure the output current of PVA at the maximum power; calculate the same environmental factor of PVA with different capacities under the same light intensity and temperature in real time; when the environmental factor is greater than the starting signal threshold of the disturbance, periodic trapezoidal disturbance is carried out to the PVA port voltage reference; if the PCC voltage Upcc exceeds the threshold set by the passive method, it is judged as islanding; otherwise, it is judged whether the change rule of Upcc is consistent with the change rule of the calculated PCC voltage Upccp under the trapezoidal disturbance; If it is consistent, it is judged as islanding; otherwise, it is pseudo islanding.

Abstract: The present invention related to the field of power system protection and control, presents a voltage travelling wave differential protection method considering the influence of frequency-dependent parameters, which provides more accurate and rapid fault identification. The technical scheme of the present invention is as follows: a calculation method of voltage travelling-wave differential protection for VSC-HVDC transmission lines, taking the influence of the frequency-dependent parameters into consideration, the steps are as follows: calculating a characteristic impedance and propagation coefficient of the frequency-dependent transmission line in time domain, collecting voltage and current signals at the both ends of the transmission line and then calculating the forward and backward voltage travelling wave, respectively, comparing a differential value of voltage travelling wave with a preset threshold value to determine whether the internal fault occurs.

Abstract: A circuit interruption apparatus, for an electrical network, comprising a circuit interruption device that is operatively connectable at a source side to a source of the electrical network and at a back side to a load of an electrical network. The circuit interruption device when closed permits and when open inhibits the current flow between the source side the back side. The current interruption device is configured to open when a current flowing therethrough meets or exceeds a fault current threshold. The circuit interruption apparatus also includes a fault current level determination unit that is configured to determine a predicted fault current level as a function of measured current and voltage values at the circuit interruption device before and after a variation in the current and voltage values at the circuit interruption device that result from a change of load at the back side of the circuit interruption device.

Abstract: A method for identifying the type of faults occurred on a power line, characterized in that it comprises: calculating a fault point voltage on fault points based on terminal voltage and fault locations of the power line; adopting the fault point voltage corresponding to a maximum transition resistance as a setting value; comparing the fault point voltage on fault points with the setting value; and identifying the type of fault as a permanent type or a transient type based on the result of the comparison.

Abstract: A circuit interruption apparatus, for an electrical network, comprising a circuit interruption device that is operatively connectable at a source side to a source of the electrical network and at a back side to a load of an electrical network. The circuit interruption device when closed permits and when open inhibits the current flow between the source side the back side,. The current interruption device is configured to open when a current flowing therethrough meets or exceeds a fault current threshold. The circuit interruption apparatus also includes a fault current level determination unit that is configured to determine a predicted fault current level as a function of measured current and voltage values at the circuit interruption device before and after a variation in the current and voltage values at the circuit interruption device that result from a change of load at the back side of the circuit interruption device.

Abstract: A method for identifying the type of faults occurred on a power line, characterized in that it comprises: calculating a fault point voltage on fault points based on terminal voltage and fault locations of the power line; adopting the fault point voltage corresponding to a maximum transition resistance as a setting value; comparing the fault point voltage on fault points with the setting value; and identifying the type of fault as a permanent type or a transient type based on the result of the comparison.