Nr Electric Co., Ltd

Nr Engineering Co., Ltd

Nr Electric Engineering Co., Ltd.

Chinese Academy of Sciences

Jiangsu University

Nanjing Inst of Astronomical Optics & Tech Nat Astronomical Observatories Chinese Acad of Science

Jie Tian

Yunlong Dong

Yu Lu

Haiying Li

Nannan Wang

Dongming Cao

Gang Li

Zhaoqing Hu

Jiudong Ding

Jiang Lu

Lei Pan

Haibin Liu

Chongxue Jiang

Ke Wang

Chao Liu

Yongping Wang

Tiangui Jiang

Quanrong Shen

Defeng Qiu

Wenqiang Zhao

Jinfeng Wang

Shunke Sui

Ruhai Huang

Jiacheng Wang

Jianyang Lian

Xinbao Wang

Baoli Chang

Yeru Wang

Gang Shen

Yu Wang

Bin Ma

Jie Ma

Hui Wang

Yeyuan Xie

Minglian Zhu

Fengfeng Ding

Ming Hu

Zhongfeng Zhang

Yadong Feng

Xinyi Tang

Huaxi Xu

Baoshun Zhang

Hua Xie

Jianchun Li

Meng Huang

Jianmin Xiao

Qiwen Zhou

Xinnan Li

Guorong Shen

Zhenxia Shao

Xinyan Jiao

Chen Xie

Jian Ge

Shengjun Wang

Yungang Wang

Ke Rui

Disclosed are a control method and system for a parallel converter system, including a common AC voltage controller and a separate current controller for each converter; the AC voltage controller generates an active current, a wattless current, and a system voltage phase reference value and, by means of communication, sends same to the current controller of each converter in island control mode to be a converter control signal; the active and wattless current outputted by each converter, along with the corresponding current reference value, accomplish the objective of the parallel converter system collectively controlling the amplitude and frequency of an AC bus voltage. The method and system are highly reliable and effectively ensure the synchronization of a plurality of converters.

Control system and control method for parallel converter system

A magnetron sputtering scanning method for manufacturing a silicon carbide optical reflector surface modification layer and improving surface profile includes (1) for a silicon carbide plane mirror to be modified, first utilizing diamond micro-powders to grind and roughly polish an aspherical silicon carbide reflector with a conventional polishing or CCOS numerical control machining method; (2) after the surface profile precision of the silicon carbide reflector satisfies a modification requirement, utilizing a strip-shaped magnetron sputtering source to deposit a compact silicon modification layer on the surface of the silicon carbide reflector; (3) then, utilizing a circular sputtering source to modify and improve the surface profile of the reflector; and (4) finally, finely polishing the modification layer, and achieving the requirements for machining the surface profile and roughness of the reflector.

Magnetron sputtering scanning method for modifying silicon carbide optical reflector surface and improving surface profile

Disclosed in the present invention is a voltage and current control method for a direct-current transmission system. The method comprises: calculating a DC voltage reference value of a voltage source converter of a DC voltage control end, on the basis whether a direct-current voltage end of a direct-current pole of a direct-current transmission system substantially controls a direct-current voltage; using &#xbd; of the calculated direct-current voltage reference value of the voltage source converter as a bridge arm voltage direct-current bias, calculating a difference between the direct-current voltage reference value of the voltage source converter and a measured direct-current voltage value, and inputting the difference into a direct-current voltage control outer loop of the voltage source converter to perform closed-loop control, so as to control the direct-current voltage or the direct current of the direct-current pole. Correspondingly, also provided is a voltage and current control device for the direct-current transmission system. By the means of the present invention, the direct-current voltage and the direct current of the direct-current transmission system provided with the voltage source converter can be effectively controlled.

Voltage and current control method and device for direct-current power transmission system

The present invention provides a series compensator and a control method. The series compensator includes a series transformer, a series transformer bypass device, a voltage source converter, a high-speed converter bypass device, a high-speed switch, and a reactor. The reactor and the high-speed switch are connected in parallel to form a current limiting module; one winding of the series transformer has two ends connected in series to a line, and the other winding thereof is sequentially connected to the current limiting module and the high-speed converter bypass device; the voltage source converter and the high-speed converter bypass device are connected in parallel; and at least one winding of the series transformer are connected in parallel to at least one series transformer bypass device. The series compensator of the present invention indirectly provides the current limiting module, so as to effectively limit the short-circuit current of a system, reduce the fault current to which the compensator is subjected, and improve the reliability of an alternating current system and the series compensator. Moreover, the current limiting module has a low voltage level, and the high-speed switch has a small breaking current, thereby providing good industrial applicability.

Series compensator and control method

A bipolar bidirectional DC converter comprises at least two valve group series () and at least six magnetic elements (), and said valve group series are divided into a Type-I valve group series () and a Type-II valve group series () each valve group series () comprises a high-voltage DC port, a low-voltage DC port and at least three AC ports, and each AC port is connected to a magnetic element (); and the other ends of the magnetic elements (), which are connected to all the AC ports in the same valve group series (), are connected.

Bipolar bidirectional DC converter, and control method and control device therefor

A DC voltage coordination control method is applied to a multi-terminal VSC-HVDC power transmission system or a VSC-HVDC power grid system. When a lower-level control is used in the active power control mode, the active power reference value of the converter is generated according to the converter DC voltage and the converter DC voltage active power curve; it also includes an upper-level control to adjust the control mode and active power setting value of the lower-level control to ensure the steady-state performance of the system. This method has low dependence on communication, avoids the problem that the fixed slope and margin cannot meet all operating conditions, and is suitable for large-scale VSC-HVDC systems, and has scalability.

Direct current voltage coordination control method

Provided are exosomes sourced from a granulocyte myeloid-derived suppressor cell and an application thereof. The exosomes are named as G-MDSC exo. Also provided is a use of the exosomes in preparing a drug used for suppressing autoimmune diseases. The G-MDSC exo can effectively suppress proliferation of CD4+T cells in vitro, promote induced proliferation of T regulatory (Treg) cells, alleviate foot swelling of model mice having delayed-type hypersensitivity, and suppress attacks of inflammatory bowel disease (IBD) and collagen-induced arthritis (CIA) of the mice.

Exosomes sourced from granulocytic myeloid-derived suppressor cells and application thereof

A coordinated control method for series voltage source converter valve groups comprises: allocating a total direct-current voltage reference value or a total active power reference value at the end where a direct-current electrode series voltage source converter valve group is located according to the total number of voltage source converter valve groups in series; for a direct-current voltage control end, controlling the direct-current voltage of each valve group according to the assigned direct-current voltage reference value for each valve group; for an active power control end, controlling the active power of each valve group according to the assigned active power reference value for each valve group and based on adding the active power compensation amount of the valve group which has voltage equalization effects on the valve group. Correspondingly, also providing a coordinated control device for series voltage source converter valve groups. The direct-current voltage equalization of each valve group in operation of the direct-current voltage control end or the active power control end of the series voltage source converter valve group is achieved.

Coordinated control method and device for series voltage source converter valve group

A method and apparatus for suppressing the impact of a compensator on line distance protection is provided, wherein the method comprises: obtaining a first current of a line connected to a compensator or series converters in the compensator, and a first voltage of a bus connected to the compensator or the line connected to the compensator; exiting the series converters and series transformers if the first current is greater than a preset current threshold and a duration is greater than a first preset time threshold; exiting the series converters and the series transformers if the first voltage is less than or equal to a preset voltage threshold and duration is greater than a second preset time threshold set the output voltage of the series converters to zero, and if a second current of an element corresponding to the first current meets conditions which the first current needs to meet; and otherwise, canceling the setting of the output voltage of the series converters to zero and obtaining a first current if a second voltage of the line corresponding to the first voltage is greater than the preset voltage threshold and the duration is greater than a third preset time threshold.

Method and apparatus for suppressing impact of compensator on line distance protection

A fault switch configuration and clearing method in a flexible DC converter station, the flexible DC converter station is configured with a grid side switch and a valve side phase-split switch in the converter station. When a fault occurs, a faulty phase and a non-faulty phase are detected and identified by means of differential protection or low voltage overcurrent. An alternating current zero crossing condition is created by means of firstly turn off the non-faulty phase valve side phase-split switch and the grid side switch, thereby cutting off the faulty phase, disconnecting the connection between a power supply and a fault point, and achieving the clearing for faults. The described fault-clearing method is simple and practical, highly reliable, and connection between the fault point and the power supply is quickly and effectively cut; converter station equipment is effectively protected, and further expansion of the fault is avoided.

Fault switch configuration and clearing method in flexible DC converter station

Provided is an on-line input and quit control method for a voltage-source converter unit. The method achieves the on-line input of a voltage-source converter unit by means of performing steps, such as charging control, deblocking transfer control and operation adjustment control, on a voltage-source converter to be input, and achieves the on-line quitting of the voltage-source converter unit by means of performing steps, such as direct-current voltage reduction control, bypass transfer control and converter blocking control, on a voltage-source converter to be quit. Correspondingly, provided is an on-line input and quit control device for a voltage-source converter unit, which can achieve the on-line steady input and quitting of a voltage-source converter in a series-type hybrid direct-current power transmission system or a series-type flexible direct-current power transmission system, without affecting the normal and stable operation of other already running converters.

On-line input control method, on-line input and quit device for voltage-source converter unit

A sub-module based hybrid converter is provided. By setting a half-controlled charging link of changing full bridge sub-modules from a blocked state to a half-blocked state one by one in a charging process, and raising the voltages of half bridge sub-modules to reach the starting point of a half bridge sub-module based self-powered supply in an uncontrolled stage of the half bridge sub-modules, the starting point of the sub-module based self-powered supply is increased, and the design difficulty of the sub-module based self- powered supply is reduced. The present invention also includes another charging method for a sub-module based hybrid converter.

Charging method for sub-module based hybrid converter

A reconfigurable MMC sub-module unit and a control unit thereof are provided, the reconfigurable MMC sub-module unit is mainly formed by an MMC sub-module unit and a reconfigurable mechanism, wherein the reconfigurable mechanism is formed by switches, and the conversion of MMC sub-module unit topology is achieved through switching on and off the switches in the reconfigurable mechanism. According to the reconfigurable MMC sub-module unit and the control unit thereof, the rapid change of a topology structure for a converter can be achieved, which is suitable for the demand of the line connection of the medium-voltage power distribution network and variable topologies, and meets requirements of dynamic simulation experiment for different converter topologies in the dynamic simulation experiment, thereby reducing construction costs and duration, improving experiment efficiency, and having high flexibility and strong versatility.

Reconfigurable MMC sub-module unit and control unit thereof

The present invention discloses a charging method for a sub-module based hybrid converter. By setting a half-controlled charging link of half-blocking all full bridge sub-modules in a charging process, and raising the voltages of half bridge sub-modules to reach the starting point of a half bridge sub-module based self-powered supply in an uncontrolled stage of the half bridge sub-modules, the starting point of the sub-module based self-powered supply is increased, and the design difficulty of the sub-module based self-powered supply is reduced. The present invention also discloses another charging method for a sub-module based hybrid converter. The above objective can also be achieved by setting a half-controlled charging link of bypassing all full bridge sub-modules in the charging process.

A method for fault positioning and recovery of a voltage source converter includes following steps. Locking a converter station when it is detected that an alternating-current voltage contains a zero sequence voltage or a direct-current voltage contains an unbalanced voltage. Positioning a fault by continuing to detect the zero sequence voltage of an alternating-current side of the converter. Recovering operation of each station after the fault is positioned. The method for fault positioning and recovery is simple, practical, has high reliability, and can effectively detect the problems that each station contains a zero sequence voltage of an alternating-current side and cannot easily position a fault caused due to transmission of the zero sequence voltage of the alternating-current side to an opposite-side alternating-current system via a voltage source converter.

Method and system for fault positioning and recovery of voltage source converter

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Jiangsu, China

Jie Tian