Resistance Selection and Control Strategy Considering the Coordination of Protection Performance and Low Voltage Ride Through of a Large-Scale Photovoltaic Power Station

Abstract

Neutral grounding through resistance is widely applied in large-scale centralized grid-connected photovoltaic power stations (PVPS), while protection measures, which are supposed to cut off the single-phase grounding fault of the collection system quickly, are required according to the grid code. Analyses on the coordination between protection performances and low voltage ride through (LVRT) are missing in current researches. Hence there could be a risk that large-scale photovoltaic units may disconnect from the grid as a result of a mismatch between the protection and LVRT. In view of the above, this paper makes contributions in two aspects. Firstly, this paper proposes a scheme on neutral point resistance selection, which is to analyze the influences on protection performances by the fault characteristics of the single-phase grounding fault of the PVPS collection system in different test environments, and then to quantify the speed and the selectivity of the zero-sequence current protection performance as assessment indexes, as required in the coordination between protection performances and LVRT, and in the coordination between protection performances of tie lines and collector lines of the collection system, and finally to select neutral point resistance based on the indexes. Secondly, this paper proposes a comprehensive control strategy on the large-scale PVPS, which can effectively improve the assessment indexes mentioned above of the protection under different active power production scenarios. Finally, a simulation will be conducted to verify the correctness and the feasibility of the resistance selection scheme and the control strategy proposed in this paper.

Keywords

• Large-scale photovoltaic power station
• neutral grounding resistance
• low voltage ride through control strategy
• protection performance index