Capacitive Emulation Using Predictive Current Control in LCL-Filtered Grid-Connected Converters to Mitigate Grid Current Distortion

Jose Miguel Espi and Jaime Castello
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Jose Miguel Espi: Department of Electrical Engineering, University of Valencia, Avd. Universitat S/N, 46100 Burjassot-Valencia, Spain
Jaime Castello: Department of Electrical Engineering, University of Valencia, Avd. Universitat S/N, 46100 Burjassot-Valencia, Spain

Energies, 2018, vol. 11, issue 6, 1-15

Abstract: This paper presents an improvement of the capacitive emulation (CE) method to reduce the line current distortion caused by grid-tied LCL-filtered converters. In these cases, the grid voltage is applied to the LCL’s capacitor, which generates a distorted capacitor current that pollutes the line. The CE method consists in controlling the converter currents instead of the grid currents, while the converter generates a copy of the distorted capacitor current, so that both the copy and the distorted currents cancel each other in the grid. Therefore, we can say that the converter emulates a negative capacitance connected to the grid, while at the same time delivers its active and reactive powers at the fundamental frequency. The CE method is achieved by adding an estimation of the distorted capacitor current to the converter current reference. However, an effective capacitive emulation requires a current control capable of accurately tracking all harmonics added to the current reference. In this sense, this paper proposes the use of a new integral predictive current control (IPCC), a dead-beat type of control that ensures a constant closed-loop group delay in a wide bandwidth. Unlike a PI control where the closed-loop delay varies with the frequency of the tracked harmonic, the constant control delay of the IPCC can be effectively compensated with a buffer-based advanced current reference. The effectiveness of the proposed CE method with IPCC control to reduce the total harmonic distortion (THD) of the line currents has been proved experimentally on a 10 kVA transformerless grid-connected three-phase inverter.

Keywords: capacitive emulation (CE); integral predictive current control (IPCC); converter current feedback (CCF); grid current feedback (GCF); total harmonic distortion (THD) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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