Abstract
Due to the large-scale renewable energy connected to the power grid by power electronic converters, the inertia and stability of the power grid is declining. In order to improve the inertia and support the grid recovery, the three-phase converter works as a virtual synchronous generator (VSG) to respond to the frequency and voltage changes of the power grid. This paper proposes a model predictive control for the virtual synchronous generator (MPC-VSG) strategy, which can automatically control the converter output power with the grid frequency and voltage changes. Further consideration of fault-tolerant ability and reliability, the method based on improved voltage vector selection, and reconstructed current is used for MPC-VSG to ensure continuous operation for three-phase converters that have current-sensor faults, and improve the reconstruction precision. The proposed method can respond to the frequency and voltage changes of the power grid and has fault-tolerant ability, which is easy to realize without pulse width modulation (PWM) and a proportional-integral (PI) controller. The effectiveness of the proposed control strategy is verified by experiment.
Highlights
The three-phase converter is applied widely in renewable energy power generation [1,2]
The virtual synchronous generator (VSG) has been used in storage system, wind turbine, micro-grid, and multi-terminal high-voltage direct current (MTDC) systems to improve the inertia and stability of power grids [7,8,9,10,11]
The reconstructed current obtained by the improved voltage selection strategy (IVSS) is closer to the actual current, the THD of the current is smaller and the errors are fewer, which demonstrates that the current reconstruction effect by IVSS is better than traditional Model predictive control (MPC)
Summary
The three-phase converter is applied widely in renewable energy power generation [1,2]. A comprehensive VSG control method is proposed in [10] for the full converter of wind turbines with energy storage, and the power balance of the wind turbine system is achieved. To address the dc-link voltage fluctuation, an improved MPC scheme is proposed for the PWM rectifier –inverter system in [17] based on the system-level power balance model. For a permanent-magnet synchronous generator (PMSG) wind turbine system, a multiple-vector direct model predictive power control is proposed in [19] for the grid-side power converter to improve the steady-state control performance. The converter controlled by conventional MPC cannot respond to the power grid changes and provide inertial support. This paper proposes a model predictive control for VSG (MPC-VSG) with reconstructed current considering inertial support for the power grid and fault-tolerant operation.
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