A low-voltage ride-through method for wind power flexible DC transmission system

Abstract

The invention discloses a low-voltage ride-through method for a wind power flexible DC transmission system. Firstly, the positive and negative sequence dual synchronous rotating coordinate system current controller adopted by the full power and partial power conversion power supply is designed to be suitable for the low voltage of the wind power flexible DC transmission system. The expression of the steady-state operating current under the condition of voltage ride-through, and establish a full-power and partial-power conversion power supply model based on it; according to the difference between the wind power flexible DC transmission system and the traditional power transmission system, design a flexible DC transmission system that meets the wind power flexible DC transmission system System control strategy; In view of the serious fault condition of the wind power flexible DC transmission system line, the DC line voltage continues to rise, endangering the safety of the line and MMC converter power electronic devices, the low-voltage ride-through circuit is used to achieve low-voltage ride-through. The application of the above method can make the flexible direct current transmission line play the role of fault isolation, and improve the operation stability of the wind power direct transmission system.

Description

technical field [0001] The invention relates to the technical field of grid-connected new energy power generation, in particular to a low-voltage ride-through method for a wind power flexible DC transmission system. Background technique [0002] At present, in order to solve the world's over-reliance on fossil energy, environmental pollution, energy resource shortage and other problems, the power generation technology using renewable energy such as wind energy has been developed rapidly. With the maturity of wind power technology and the strong support of policies, the development of wind farms has the characteristics of large scale and far away from the load center. These large-scale wind power cannot be accommodated locally, so they need to be transported to the load center through the transmission grid over long distances. In the past, most of the substations were AC convergence. However, the current flexible DC transmission technology is mature. Compared with AC transmi...

AI Technical Summary

Problems solved by technology

[0003] However, when a fault occurs on the AC side, the output power capability of the grid-side converter is reduced, the output power of the wind farm remains unchanged, and excess power is accumulated on the DC transmission line, resulting in an increase in the DC voltage.

The low-voltage ride-through strategy of the existing technology focuses on the coordinated control of MMC converters on the wind farm side of wind power and flexible direct current transmission lines. Although the method of increasing frequency or reducing voltage does not require additional equipment, it is too large Frequency or voltage changes within a certain range may have a great impact on the wind turbine, and even cause the shutdown action, which cannot completely solve the problem of the power difference between the two ends

Images