Virtual synchronous generator control system and control method thereof

Abstract

The invention provides a virtual synchronous generator control system and a control method thereof. The system comprises a unit voltage upper limit control module, a unit voltage lower limit control module, a frequency control module, an active current instruction switching module, an active current control module, a power grid synchronization module, an AC voltage control module, a reactive current control module, an active current virtual impedance module, a reactive current virtual impedance module, and a coordinate transformation module. According to the method, an active current error is adopted to adjust the output voltage phase of the converter, a damping impedance link is added in a current control loop, constant power unit capacitance average voltage control can be switched in the alternating current and direct current side transient state fault period, and stable operation can be achieved under the off-grid and grid-connected working conditions of the converter.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a virtual synchronous generator control system and a control method thereof. Background technique [0002] With the rapid development of flexible DC transmission technology, the voltage level and capacity have been continuously improved, and the application occasions cover the distribution network and the backbone network. The converter has become one of the core power equipment in the country, and the converter control technology is also one of the research hotspots in this field in recent years. one. The DC projects at home and abroad mainly adopt double-terminal back-to-back connection and multi-terminal DC interconnection structure. The operation mode of each end converter can be automatically converted according to the operation needs, including off-grid independent operation with passive load, network constant voltage control or constant power o...

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Problems solved by technology

[0003] Virtual synchronous machine control is one of the research hotspots in the direction of converter control recently. The document "A Multi-inverter Microgrid Frequency Adjustment Strategy Based on Virtual Synchronous Generator" presents a typical virtual synchronous Generator control structure, its active power control loop adopts the inertia link to simulate the natural inertia of the synchronous generator, calculates the AC voltage phase of the converter with the pure integral module, realizes self-synchronization with the grid, and can run stably under off-grid and grid-connected conditions, However, due to the series structure of the virtual inertia link and the integral module and the pure integral module, the active power adjustment speed of this structure is limited, there is no direct control link for introducing current, and the current response speed is slow

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