Nr Electric Co., Ltd

Nr Engineering Co., Ltd

Nr Electric Engineering Co., Ltd.

Quanrong Shen

Yunlong Dong

Jie Tian

Lei Pan

Wei Yan

Yu Lu

Haiying Li

Jun Chen

Chao Liu

Kai Wang

Xinbao Wang

Baoli Chang

Guang Wang

Qixue Zhang

Huazhong Li

Weiqun Liu

Xiangjian Shi

Huimin Wang

A starting and stopping method for a static synchronous series compensator (SSSC) is provided. A starting process includes: connecting a converter to a shunt transformer, and closing a breaker which connect the AC system and the shunt transformer to charge the converter until the DC voltage is stable; opening the breaker, and connecting the converter to a series transformer through a change-over switch; and deblocking the converter, and controlling a current of a bypass switch of the series transformer to approach zero. A stopping process includes: switching a control mode of the converter to make the current of the bypass switch approaches zero when closed the bypass switch, then controlling a current of the series transformer to be gradually reduced to zero to make the series transformer out of service, and blocking the converter.

Starting method and stopping method for a static synchronous series compensator

A line power control method and system for a unified power flow controller includes outer loop line power control, inner loop valve side current control, and converter valve control. Series-side converter valve side current reference values Iand Iare calculated by means of the outer loop line power control according to line power instructions Pand Qthat are input, a measured line power U, and measured line power Pand Q; a converter output voltage reference value Uis calculated by means of the inner valve side current control according to the valve side current reference values that are output by means of the outer loop power control, a measured valve side current, and a measured valve side voltage; and finally, a converter outputs, according to the voltage reference value, a corresponding voltage to control line power to achieve a reference value.

Line power control method and system for unified power flow controller

A unified power flow controller for a double-circuit transmission line comprises at least one parallel-connection transformer, three current converters, at least two series-connection transformers, a parallel-connection side switching circuit, a series-connection side switching circuit and a direct current common bus. The series-connection transformers connected with at least one group of by-pass switches in parallel. The three current converters connected to each loop line in series after being connected with at least one series-connection transformer through the series-connection side switching circuit. The three current converters connected to an alternating current system after connected with at least one parallel-connection transformer through a parallel-connection side switching circuit starting circuit. The three current converters are connected to the direct current common bus through a transfer switch.

Unified power flow controller for double-circuit line

A frequency-conversion differential protection method for an output transformer of a static frequency convertor system. The method comprises: a protection device measuring a three-phase current at each side of an output transformer of an SFC system; according to the connection manner of the output transformer, using a triangle side as a reference to conduct phase correction on a star side; at the same time, taking into account different secondary rated currents at each side of the transformer to adjust a balance coefficient of each side, so as to form sampling values of a correcting current and a differential current at each side, and using a startup and shut-down protection algorithm free from frequency influence in generator protection to calculate amplitude values of the correcting current, the differential current and a restraint current; and according to the magnitudes of the differential current and the restraint current, using the ratio restraint differential characteristic to achieve the frequency-conversion ratio differential protection of the output transformer. The present protection method is suitable for large-scale frequency change. Compared with the current quick-breaking protection, the sensitivity of internal failure detection in the output transformer is greatly improved.

Frequency-conversion differential protection method for output transformer of static frequency converter system

Embodiments of the present invention disclose a current source converter differential protection method, including: sampling, by a relay protection device, secondary side currents of current transformers on two sides of a protected current source converter, to obtain incomer-side three-phase currents, and outgoer-side three-phase currents; rectifying the incomer-side three-phase currents and the outgoer-side three-phase currents, to obtain an incomer-side input current and an outgoer-side output current which are equivalent; converting the incomer-side input current and the outgoer-side output current according to a current ratio of the current transformers on the two sides, to acquire a transient differential current and a transient restraint current; acquiring a differential current and a restraint current according to the transient differential current and the transient restraint current; and achieving differential protection according to the differential current and the restraint current. The embodiments of the present invention further disclose a relay protection device correspondingly.

Current source converter differential protection method and relay protection device

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Jiangsu, China

Quanrong Shen