Voltage source current converter overload current limiting method

Abstract

The invention relates to a voltage source current converter overload current limiting method. A voltage source current converter is applied to a monopole or double pole topology in a flexible direct current power transmission system; when a pole control system receives a water-cooled overload current limiting instruction, active power and inactive power instructions are changed at the same time according to an assigned slope, an absolute value of a current of a bridge arm of the current converter is enabled to decrease according to a fixed slope, and that active power and inactive power fall to zero at the same time can be ensured; an aim of limiting load of the current converter in water-cooled manner can be attained by reducing the current of the bridge arm; after a water-cooled overload power limiting instruction received by the pole control system is removed, current values of the active power and the inactive power remain unchanged; when the water-cooled overload power limiting instruction is received next time, current power values will continue falling till reaching zero; via use of the method, a water-cooled overload power limiting function can be fulfilled in a voltage source type monopole or double pole topology, safe operation of a current converter valve can be ensured during overload time, operation processes are simple and reliable, and the method is easy to implement.

Description

technical field [0001] The invention belongs to the field of direct current transmission, and in particular relates to a method for limiting the overload current of a voltage source converter. Background technique [0002] Flexible DC transmission uses voltage source converters, which can independently adjust the transmission of active and reactive power, improve the transmission capacity of the AC system, and easily form a multi-terminal DC transmission system. And other application fields, have obvious competitiveness. [0003] At present, the topology of flexible DC transmission voltage source converters mostly adopts modular multi-level converter technology. In the normal working state of the converter, the six bridge arms pass current, and the switching devices of the modules themselves cause heat loss. , a certain water-cooling capacity is required to lower the temperature to ensure the normal operation of the module, but if the water-cooling capacity is insufficient,...

AI Technical Summary

Problems solved by technology

[0003] At present, the topology of flexible DC transmission voltage source converters mostly adopts modular multi-level converter technology. In the normal working state of the converter, the six bridge arms pass current, and the switching devices of the modules themselves cause heat loss. , a certain water-cooling capacity is required to lower the temperature to ensure the normal operation of the module, but if the water-cooling capacity is insufficient, the water temperature of the valve outlet water will be too high and the system will not work normally. The system sends the water cooling overload limit current command

[0004] At present, after the upper computer receives the water-cooling overload limit current command, the processing method can generally adopt the method of reducing the operating DC current, or adopt the dynamic current limiting control method. The former is mostly used in the current source type traditional DC transmission method, and the latter belongs to the inner loop. Current limit, mostly used for transient current limit, has certain application limitations in voltage source converter overload current limit, because the bridge arm current of voltage source converter not only includes active components, but also includes reactive current Components, only after reducing the DC current can not fully meet the current target of the overload limit bridge arm, the transient current limit has a faster response speed, generally used for transient control, not suitable for the current limit requirements required by the overload

Images