Next Article in Journal
Energy Performance Investigation of a Direct Expansion Ventilation Cooling System with a Heat Wheel
Next Article in Special Issue
Hybrid PWM Control for Regulating the High-Speed Operation of BLDC Motors and Expanding the Current Sensing Range of DC-link Single-Shunt
Previous Article in Journal
Development and Numerical Performance Analysis of a Pump Directly Driven by a Hydrokinetic Turbine
Open AccessFeature PaperArticle

Frequency Adaptive Current Control Scheme for Grid-connected Inverter without Grid Voltage Sensors Based on Gradient Steepest Descent Method

1
Department of Electrical and Information Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea
2
Automotive Components R&D Group, Korea Institute of Industrial Technology, 6 Cheomdan-gwagiro 208-gil, Buk-gu, Gwangju 61012, Korea
*
Author to whom correspondence should be addressed.
Energies 2019, 12(22), 4266; https://doi.org/10.3390/en12224266
Received: 28 August 2019 / Revised: 16 October 2019 / Accepted: 6 November 2019 / Published: 8 November 2019
(This article belongs to the Special Issue Power Electronics and AC Machine Drive System)
This paper presents a frequency adaptive grid voltage sensorless control scheme of a grid-connected inductive–capacitive–inductive (LCL)-filtered inverter, which is based on an adaptive current controller and a grid voltage observer. The frequency adaptive current controller is constructed by a full-state feedback regulator with the augmentation of multiple control terms to restrain not only the inherent resonance phenomenon that is caused by LCL filter, but also current harmonic distortions from an adverse grid environment. The number of required sensing devices is minimized in the proposed scheme by means of a discrete-time current-type observer, which estimates the system state variables, and gradient-method-based observers, which estimate the grid voltages and frequency simultaneously at different grid conditions. The estimated grid frequency is utilized in the current control loop to provide high-quality grid-injected currents, even under harmonic distortions and the frequency variation of grid voltages. As a result, the grid frequency adaptive control performance as well as the robustness against distorted grid voltages can be realized. Finally, an inverter synchronization task without using grid voltage sensors is accomplished by a fundamental grid voltage filter and a phase-locked loop to detect the actual grid phase angle. The stability and convergence performance of the proposed observers have been studied by means of the Lyapunov theory to ensure a high accuracy tracking performance of estimated variables. Simulation and experimental results are presented to validate the feasibility and the effectiveness of the proposed control approach. View Full-Text
Keywords: distorted grid; frequency adaptation; gradient steepest descent; grid-connected inverter; LCL filter; least-mean-square; voltage sensorless control distorted grid; frequency adaptation; gradient steepest descent; grid-connected inverter; LCL filter; least-mean-square; voltage sensorless control
Show Figures

Figure 1

MDPI and ACS Style

Tran, T.V.; Kim, M.; Kim, K.-H. Frequency Adaptive Current Control Scheme for Grid-connected Inverter without Grid Voltage Sensors Based on Gradient Steepest Descent Method. Energies 2019, 12, 4266.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop