Tianjin University

China National Offshore Oil Corporation

Cnooc Tianjin Chemical Research & Design Institute Co. Ltd.

Cnooc Energy Technology & Services Limited

Bin Li

Botong Li

Yongli Li

Xiaolong Chen

Jian Li

Yan Liu

Xiaowen Han

Weixin Zhang

Haibin Yu

Jiazhong Zang

Zhiying Yang

Fahui Chen

Jiawei He

Chang Shu

Jing Zhang

Zhiyu Sui

Weijie Wen

Xunzhi Zhao

Jingxin Fan

Mingrui Lv

Yueqiu Pan

Hong Qiu

Hong Cheng

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.

Multi-terminal differential protection setting method for distributed generator T-connected distribution network

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.

Islanding detection method in DC microgrids based on MPPT trapezoidal voltage disturbance

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.

Adaptive fault clearing scheme for MMC VSC-HVDC grid based on source-grid coordination

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. The present invention is mainly applied in the field of power system protection and control.

Time domain calculation method of voltage traveling-wave differential protection for VSC-HVDC transmission lines

The present invention discloses a modular multilevel dynamic switching DC-DC transformer, which consists of N DC-DC sub-modules connected in series. Each of the DC-DC sub-modules is of a symmetrical structure capable of realizing bidirectional power flow, which consists of two half-bridge sub-modules and isolating switches S, Sbetween capacitors C, Cof the two half-bridge sub-modules. The capacitors C, Care disposed in parallel between the half-bridge sub-modules and the isolating switches. Assuming that the power flows in the primary side of the DC-DC transformer and flows out from the secondary side; the half-bridge sub-module located on the primary side of the DC-DC transformer is referred to as a primary-side sub-module; and, the half-bridge sub-module located on the secondary side of the DC-DC transformer is referred to as a secondary-side sub-modules. By turning on or off the switching devices, the switch-on or switch-off of the primary-side sub-module or the secondary-side sub-module can be realized, leading to the dynamic switching in four different operating states of the DC-DC transformer and realizing the voltage conversion and energy exchange. Compared with the prior art, the present invention is able to change the transformer ratio dynamically, realizing the control of the DC power flow, and, greatly decreases the number of sub-modules, has remarkable economic efficiency, can effectively reduce the size of DC-DC transformers, and it is advantageous for popularization.

Modular multilevel dynamic switching DC-DC transformer

The present invention discloses a DC solid-state circuit breaker with self-adapt fault current limiting capability. The topology of the DC solid-state circuit breaker is a H-bridge circuit consisting of two unidirectional breakable bridge arms and two series-connected diode bridge arms, wherein the two unidirectional breakable bridge arms are connected in series to the two series-connected diode bridge arms in a same direction to form two series branches, respectively; the series branches are connected in parallel; a series branch formed by a DC reactor L and a DC biased power supply is connected to the PCC between the two unidirectional breakable bridge arms and the PCC between the two series-connected diode bridge arms; the DC line is connected to the two PCCs, respectively.

DC solid-state circuit breaker with self-adapt current limiting capability and the control method thereof

The present disclosure relates to a micro-loss combined mechanical DC circuit breaker and its control method, consisting n ports, n load current paths and a main breaker; wherein the n load current paths are parallel with the main breaker, and each load current path is divided into an upper bridge arm and a lower bridge arm at a connection point; each port is electrically connected to the connection point of a load current path; the upper bridge arm of each load current path is made of an ultra-fast mechanical switch; the lower bridge arm of each load current path is made of a residual current breaker and a fast closing switch; the main breaker consists of a high-voltage capacitor in series with a low-voltage capacitor that is pre-charged.

Micro-loss combined mechanical DC circuit breaker and its control method

There is provided a method for identifying fault types of HVDC physical transmission line, including: measuring positive and negative voltage values and current values at a j-terminal and k-terminal of the HVDC physical transmission line, and converting them to voltage and current values under mode components; calculating differential current values of travelling wave at the j-terminal and k-terminal under zero-mode and one-mode components of the HVDC physical transmission line, respectively; comparing with the calculated differential current value at the one-mode components under the current time t and the same at time t&#x2212;tto determine whether the HVDC physical transmission line is faulty; converting differential current values of the travelling wave at the j-terminal and k-terminal under the mode components to differential current values under the maximum amount, respectively; calculating fault type coefficients of both terminals; and identifying the fault types based on the fault type coefficients.

Method for identifying fault types of high voltage direct current transmission line

The present disclosure relates to a method for a simulated moving bed to adsorb and separate polycyclic aromatic hydrocarbons. Zeolite, metal oxide and metal-modified materials are employed as adsorbent. Firstly, diesel oil flows through pre-treatment adsorbent to remove the trace amount of impurities. Secondly, the purified diesel oil flows through the simulated moving bed so that the PAHs can be separated from diesel oil. In this process, the valves are switched periodically, leading to the relative movement of adsorption beds. At the same time, desorbent is pumped into the equipment to wash out PAHs, achieving the continuous adsorption-regeneration operation. Thirdly, simple distillation is employed to separate desorbent from clean diesel oil and PAHs, respectively. Finally, the fractions of clean diesel oil and PAHs can be obtained, respectively. The separated desorbent can be recycled. The PAHs removal rate can reach to 90%.

Method for simulated moving bed to adsorb and separate polycyclic aromatic hydrocarbons

Growing community of inventors

Tianjin, China

Bin Li