A control method for improving the fault ride-through capability of AC side of flexible direct current transmission

Abstract

The invention discloses a control method for improving the fault ride-through capability of the AC side of flexible direct current transmission. According to the mathematical model, the analytical relationship between the real-time power value of the AC and DC side of the MMC converter station and the voltage value of the DC side of the MMC converter station is analyzed. The relationship between the unbalanced degree of the DC side power and the voltage drop of the DC side, and then according to the relationship, the real-time target value of the power adjustment of the converter station is determined. The present invention significantly reduces the power unbalance degree of the AC and DC sides of the converter station, thereby reducing the power adjustment pressure of the existing outer loop power control and inner loop current control, indirectly improving the control effect of the existing control strategy, and can be very good Improve the stability of DC voltage.

Description

technical field [0001] The invention belongs to the technical field of two-terminal or multi-terminal flexible direct current transmission systems based on MMC converters, and in particular relates to a control method for improving the fault ride-through capability of the AC side of flexible direct current transmission. Background technique [0002] my country's energy distribution and load distribution do not match, and the distance between energy-rich areas and heavy-load areas is relatively long. In order to achieve efficient allocation and full utilization of energy, it is necessary to develop large-capacity long-distance transmission technology. At the same time, DC asynchronous interconnection also avoids large-scale chain links. Faults occur, eliminate low-frequency oscillation problems, and will not aggravate the short-circuit current of the AC power grid. Modular multi-level flexible DC transmission technology has many excellent characteristics such as small footprin...

AI Technical Summary

Problems solved by technology

These control methods all have a controllable margin in power adjustment. When a serious fault occurs on the AC side, the switching power of the AC and DC side of the converter station will be greatly unbalanced at the moment of the fault, and the degree of this imbalance will exceed The power adjustment controllable margin of the existing control method has insufficient adjustment ability, resulting in voltage instability on the DC side and the shutdown of the converter station

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