Abstract
When the single-phase reclosing of the high-voltage circuit, there will be tremendous negative sequence current generation. The connection of inverter-type new energy sources may increase the negative sequence current of the power system. The risks will be greatly increased if a large negative sequence current invades the generator, and it will cause the general stator damaged and offline. Based on the chain STATCOM compensation, a new strategy of negative sequence current coordinated control protection on the generator extremity is put forward. This strategy can predict the operation time of inverse time negative sequence current protection by monitoring the negative sequence current on the generator extremity. Once it is determined that the negative sequence current has an effect on the power system, according to the relationship between the STATCOM capacity and the magnitude of negative sequence current, two schemes of full compensation and incomplete compensation are proposed. The negative sequence current output by STATCOM suppresses the magnitude of the negative sequence current invading the generator. It eliminates or prolongs the operation time of the negative sequence current protection and gets more time for power system security and stability control. Finally, the simulation results verify the correctness and feasibility of the proposed strategy.
Highlights
The development of society has brought about an increase of the electricity demand
It accurately predicts the operation time of the protection device according to the change of the negative sequence current and proposes a current control strategy to compensate the negative sequence on the generator extremity
This article analyzes the change of negative sequence current when new energy is connected to the power system
Summary
The development of society has brought about an increase of the electricity demand. Traditional electric power development concept can hardly meet the quality demand of the electric energy. Virtual synchronous generator control is widely used in wind power and photovoltaic inverters, but it may help increase the system’s large negative sequence current when the grid voltage is unbalanced. Reference [7] proposed an inverse time protection strategy when the distributed inverter power is connected, which based on the electrical characteristics of the voltage drop during a fault. This article analyzes the impact on the increase of negative sequence current It accurately predicts the operation time of the protection device according to the change of the negative sequence current and proposes a current control strategy to compensate the negative sequence on the generator extremity. Extensive simulations using the PSCAD/EMTDC software are performed to evaluate the performance of the proposed strategy
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