Power damping synchronization control method suitable for VSC-HVDC connection extremely-weak AC power grid

Abstract

The invention discloses a power damping synchronization control method suitable for a VSC-HVDC connection extremely-weak AC power grid. The power damping synchronization control method is characterized in that: a phase locked loop (PLL) is preserved, an output phase angle theta of the phase locked loop only serves as an input reference phase angle of system DQ transformation; an external loop voltage controller controlled by a conventional current vector is kept unchanged on the basis of step 1, the external loop voltage controller outputs idref and iqref which serve as reference values of an internal loop current controller, and the capacity of restricting overcurrent of a VSC current converter is preserved; and an internal loop id current controller is redesigned, a power synchronization loop (PSL) and a power damping loop (PDL) are embedded in the internal loop id current controller so as to generate a phase angle signal delta required by output voltage of the VSC current converter, and an internal loop iq current controller generates an amplitude signal Em of the output voltage of the VSC current converter through adjusting iq component. By introducing the PSL and the PDL into the internal loop, contradiction between power synchronization control (PSC) and PLL is effectively coordinated, the negative influence of the PLL on VSC-HVDC system stability in a weak system is inhibited, and the system control performance of the VSC-HVDC under the working condition of being connected with the receiving-end extremely-weak AC power grid.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution, and in particular relates to a power damping synchronous control method suitable for a VSC-HVDC connected to a very weak AC power grid. Background technique [0002] Voltage Source Converter Based HVDC (Voltage Source Converter Based HVDC, VSC-HVDC) can theoretically operate under special working conditions of extremely weak AC systems due to the use of fully controlled devices. The current vector control strategy achieves independent decoupling control of active and reactive power by controlling the d-axis and q-axis currents in the synchronous rotating coordinate system. Research results in recent years have shown that the VSC-HVDC system based on conventional current vector control is under weak AC system conditions, such as the special condition of AC system short circuit ratio (Short CircuitRatios, SCR) SCR = 1.0, the VSC-HVDC system is relatively The gain change...

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Problems solved by technology

Research results in recent years have shown that the VSC-HVDC system based on conventional current vector control is under weak AC system conditions, such as the special condition of AC system short circuit ratio (Short CircuitRatios, SCR) SCR = 1.0, the VSC-HVDC system is relatively The gain of the phase-locked loop (PLL) is very sensitive to changes, and the system control performance will seriously deteriorate with the increase of the gain. At the same time, the maximum active power that can be transmitted by the VSC-HVDC system is also significantly limited.

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