Direct current voltage deviation slope control method for multi-end flexible direct current power transmission system

Abstract

The invention discloses a direct current voltage deviation slope control method for a multi-end flexible direct current power transmission system. By using the direct current voltage deviation slope control method, direct current voltage of the system is stabilized within a power running range by taking a converter station as a direct current voltage main control station in the multi-end flexible direct current power transmission system; a plurality of other converter stations are connected with an active network; and by combining a deviation characteristic of a direct current voltage deviation control mode with a slope characteristic of a direct current voltage slope control mode, a plurality of converter stations have tide adjusting capacity and transient quick direct current network power stabilization capacity. By using the method, the direct current voltage deviation control mode and the direct current voltage slope control mode are combined, active power can be adjusted in the transient state of the converter stations according to the deviation characteristic of the direct current voltage deviation control mode, and the converter stations can realize functions of preparing fixed direct current voltage according to the slope characteristic of the direct current voltage slope control mode; and the dynamic response of the system is accelerated.

Description

technical field [0001] The invention relates to the technical fields of multi-terminal flexible power transmission and distribution, power electronics and user electric power in power systems, and more specifically relates to a DC voltage deviation slope control method for multi-terminal flexible DC power transmission. Background technique [0002] In recent years, with the continuous development of wind power systems, the grid connection of large-scale wind power systems has become a hot topic. Among the many solutions to grid-connected problems of wind power systems, VSC-MTDC (Voltage Source Converter Multi-Terminal DC Transmission system, a multi-terminal flexible DC transmission system using voltage source converters) has received extensive attention and applications. Compared with the traditional LCC-MTDC (Line Commutated Converter Multi-Terminal DC Transmission system, a multi-terminal DC transmission system using phase-controlled converters), VSC-MTDC has the advantag...

AI Technical Summary

Problems solved by technology

[0004] However, the DC voltage deviation control method and the DC voltage slope control method have their own defects, which limits the application of these two control methods.

The DC voltage deviation control method has the following defects: 1. Since only a single converter station participates in power regulation at the same time, its response speed is not as good as the DC voltage slope control method; 2. Multiple backup constant voltage converter stations require multiple constant voltages 3. When the scale of the DC system becomes larger, the number of backup constant DC voltage converter stations required by the DC system will increase. Since each backup constant DC voltage in the DC voltage deviation control mode The greater the deviation will be, however, there is a DC voltage operating range between the voltage source converter station and the DC line, that is, in order to maintain the stable power operation of the voltage source converter station, the DC voltage has an operating lower limit, and in order to maintain the insulation level of the DC network, There is an operating upper limit for DC voltage; therefore, the deviation value cannot exceed the range of DC voltage operation, which limits the number of backup constant DC voltage converter stations

For the DC voltage slope control method, the converter station can quickly respond to the power flow change of the DC network and adjust its DC power, so this control method is more suitable for flexible DC transmission systems with frequent power changes, such as wind power In the multi-terminal flexible DC transmission system of the field, but its defect is that the DC power of the converter station using the slope controller cannot accurately track its set value, so that the precise control of the DC power cannot be achieved

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