Control method of back-to-back DC power transmission system accessed to weak AC system

Abstract

The invention relates to a control method of a back-to-back DC power transmission system accessed to a weak AC system. The method comprises the following content: 1, an inversion station employs variable AC voltage control, i.e., a DC voltage instruction value is determined through a DC power instruction value and a DC voltage operation value is determined through the DC voltage instruction value; 2, coordinated control of inversion station converter transformer tapping-off switches and reactive groups is performed; and 3, and coordinated control of rectification station converter transformer tapping-off switches and reactive groups is performed. According to the invention, safe and stable operation of a power grid is ensured, and the service life of the back-to-back DC power transmission system is also prolonged.

Description

technical field [0001] The invention relates to a control method of a back-to-back DC power transmission system, in particular to a control method of a back-to-back DC power transmission system connected to a weak AC system. Background technique [0002] The back-to-back DC transmission system refers to the DC transmission system without DC transmission lines, and the rectifier station and inverter station are usually placed in the same converter station. The back-to-back DC transmission system has the characteristics of low difficulty in equipment manufacturing, flexible control, and low investment. It has played an active role in realizing the mutual benefit and interoperability of large-scale power grids and improving the safety and stability of AC systems. With the development of the power grid, the demand for interconnection capacity of the regional power grid will further increase, and the back-to-back DC transmission system will play a more important role in the devel...

AI Technical Summary

Problems solved by technology

(2) The inverter station does not have the ability to suppress the fluctuation of the AC bus voltage, which is not conducive to the voltage stability of the weak AC system

(2) The inverter station has the function of suppressing the voltage fluctuation of the AC system. When the AC bus voltage rises, the arc extinguishing angle will increase, and the reactive power consumption of the inverter station will increase, and vice versa

(3) As the DC power changes from the minimum power to the rated power, the DC voltage remains unchanged, which makes the tap changer need to operate with the adjustment of the DC power, and the tap changer operates more times

Under the relevant control method, a series of problems have been exposed in the operation of the back-to-back DC transmission system. The problems associated with the operation of the power group and the converter transformer tap changer

From 2014 to 2015, the Heihe back-to-back HVDC transmission system also had the problem of the switching of reactive power group on the Chinese side and the action of the converter transformer tap changer, and the accompanying actions of the switching of the reactive power group on the Russian side and the tap changer of the converter transformer

In addition, in the Gaoling and Heihe back-to-back DC power transmission systems, there were many times that the tap changer moved to one gear, causing the reactive power group to switch, and then the tap changer moved in the opposite direction to another gear.

Since the design operation times of the converter transformer tap-changer is about 200,000 times, and it is a built-in type, it is difficult to replace; the design switching times of the reactive power group is 5000 times; the converter transformer tap-changer repeatedly operates and the reactive power group switches frequently It will directly affect the service life of the back-to-back DC transmission system and the safe and stable operation of the power grid

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