Abstract
In a single-phase grid-tied inverter, the direct current (DC) offset error included in the measured grid side phase current has various causes, such as a non-ideal current sensor, unbalanced power supply of an operational amplifier, and nonlinear features of analog components in interface circuits, etc. If the DC offset error is included in the measured current, it causes the secondary harmonic of fundamental frequency and the DC component in grid phase current which result in degradation of inverter performance. In this paper, a theoretical detection method of the secondary harmonic of the fundamental frequency and a DC component in grid phase current for a proportional-resonant (PR) current control system is introduced. Based on the detection method, an algorithm for compensating DC offset error is also presented for single-phase grid-tied inverters. Simulation results and experimental verification of the DC offset error compensation algorithm are shown in this paper.
Highlights
Grid-tied inverters have received attention due to the high demands of distributed energy systems [1,2]
The phase current of the grid side is measured through the following process: (1) a current sensor; (2) analog signal processing circuits, and (3) analog-digital converter (ADC)
An algorithm-based direct current (DC) offset compensation is proposed in Reference [11] where scaling error and DC offset in measured phase current are integrated over one cycle of a grid frequency, and information about the error is analyzed from the integrated signal
Summary
Grid-tied inverters have received attention due to the high demands of distributed energy systems [1,2]. To prevent the DC current component, a line frequency isolation transformer was used in References [4,5], but it is applicable, typically, for three-phase inverters As another approach, an offset error was detected using a reactor [6]. An algorithm-based DC offset compensation is proposed in Reference [11] where scaling error and DC offset in measured phase current are integrated over one cycle of a grid frequency, and information about the error is analyzed from the integrated signal. For the implementation of the method in Reference [11], integration of one cycle of phase current is required for error compensation. Reference [11], integration of one cycle of phase current is required for error compensation. Simulation experimental results ofare theshown proposed algorithm experimental results and of the proposed algorithm in this paper. are shown in this paper
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