Starting control method and device of flexible DC power transmission converter valve

Abstract

The invention relates to a starting control method and device of a flexible DC power transmission converter valve. The control method comprises the steps of putting a soft starting resistor, and charging sub-modules of a bridge arm; executing voltage-sharing sequencing operation on the sub-modules, removing a part of sub-modules in a bridge arm; and bypassing the soft starting resistor, and shutting all sub-modules which are not removed in the bridge arm and at least one sub-module which is removed so as to adjust a voltage of the bridge arm. By controlling the sub-modules which are removed involtage-sharing sequencing operation of an input part when the soft starting resistor is bypassed, a production condition that a phase step voltage is removed by the voltage of the bridge arm to damage an impact current can be adjusted, impact brought by bypassing the soft starting resistor is eliminated so as to prevent the impact current at an AC side, and the safety of a converter valve systemis ensured.

Description

technical field [0001] The invention relates to a start-up control method and device for a flexible direct current transmission converter valve, belonging to the technical field of flexible direct current transmission. Background technique [0002] Modular multi-level flexible direct current transmission (MMC-HVDC) has the characteristics of flexible control, four-quadrant operation, and easy expansion. have great advantages. With the continuous maturity of modular multi-level flexible DC transmission technology, the control requirements for flexible DC transmission are also getting higher and higher. [0003] In general engineering applications, the start-up process of the HVDC converter valve is as follows: the HVDC system is in a locked state, and the sub-module of the bridge arm is pre-charged with a soft-start resistor; after charging to a certain stage, the soft-start resistor is bypassed , unlock the flexible direct current transmission system, and continue to charg...

AI Technical Summary

Problems solved by technology

The second time occurs when the soft-start resistor is bypassed. Due to the partial voltage of the soft-start resistor during the charging process, after the soft-start resistor is cut off, there is a voltage difference between the bridge arm voltage and the valve side voltage, resulting in an inrush current.

If DC charging is performed for other terminals through the DC side at this time, after the soft-start resistor is cut off, it will also cause an inrush current on the DC side

[0005] For reducing the first inrush current during the charging process of the starter module, without changing the system parameters, the most effective method is to increase the soft start resistance. The problem caused by increasing the soft start resistance is the soft start resistance If the divided voltage is too large, the divided voltage of the bridge arm will decrease. When the soft-start resistor is bypassed, a larger voltage difference will be brought, resulting in a larger second impulse current.

[0006] In addition, a large inrush current will also be generated during the unlocking phase, because the flexible DC transmission system generally adopts the SPWM modulation method to ensure the sinusoidal nature of the phase voltage, but its utilization rate of the DC voltage is low, and the three-phase uncontrolled rectification The DC bus voltage does not meet the minimum requirements of SPWM modulation, resulting in an inrush current during the unlocking phase

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