Protection control system and control method for AC/DC hybrid grid power converter

Abstract

The invention discloses a protection control system for a power converter of an alternating-current and direct-current hybrid power grid, and aims to solve the problem in control on an output behavior of an access converter when faults occur on the alternating-current power grid side. The protection control system is suitable for unbalanced alternating-current power grids. The influence of the negative sequence component of the power grid on the system has to be reasonably controlled as the safety of the converter is endangered and the service life of the converter is shortened due to the problems of unbalanced or non-sinusoidal three-phase current, relatively large voltage ripple on the direct-current side, power fluctuation and the like of the system caused by the negative sequence component of the power grid during fault occurrence of the alternating-current power grid. The positive and negative sequence content of an alternating-current grid-side current reference is reasonably adjusted by adjusting parametric variables according to flexible positive and negative sequence control strategies in a d-q synchronous coordinate system, so that the waveform quality of the grid-side current and the instantaneous active power and instantaneous reactive power of the system can be reasonably controlled and the protection control of the converter can be realized.

Description

technical field [0001] The invention discloses a protection control system and a control method for a power converter of an AC-DC hybrid grid suitable for unbalanced AC grids, and belongs to the technical field of converter control in AC-DC hybrid grids. Background technique [0002] The application of AC and DC grids has expanded the application of power electronic conversion technology in the field of power system distribution. However, the existing control methods are based on the three-phase AC grid voltage as the premise, and the failure of the three-phase grid is inevitable. In new energy grid connection, if the three-phase grid fails, the regulations stipulate that the converter cannot leave the grid immediately at this time, and must have low voltage ride-through capability within a certain period of time; Due to the existence of the negative sequence component of the power grid, the three-phase current of the system will be unbalanced or non-sinusoidal, and there wi...

AI Technical Summary

Problems solved by technology

In new energy grid connection, if the three-phase grid fails, the regulations stipulate that the converter cannot leave the grid immediately at this time, and must have low voltage ride-through capability within a certain period of time; Due to the existence of the negative sequence component of the power grid, the three-phase current of the system will be unbalanced or non-sinusoidal, and there will be large voltage ripples and power fluctuations on the DC side, which will endanger the converter and power grid equipment and shorten their life.

If the three-phase current is non-sinusoidal, it will cause serious harm to the public power grid, such as causing additional harmonic loss to the power grid components, causing the line to overheat or even cause a fire, causing relay protection and automatic device malfunction, and causing electrical measuring instruments to measure Inaccurate, causing interference to adjacent communication systems; if there is a large ripple on the DC side, it is also extremely harmful, such as reducing system efficiency, interfering with the logical relationship of digital circuits, generating harmonics on electrical appliances, and generating surge voltage or current ; If the reactive power fluctuation of the system cannot be reasonably controlled, it will seriously affect the power factor of the system and bring adverse effects on the public power grid, such as increasing the current and equipment capacity, increasing the loss of equipment and lines

Images