A Robust Repetitive Control Strategy for CVCF Inverters with Very Low Harmonic Distortion

Repetitive control (RC) is gradually used in inverters tied with weak grid. To achieve the zero steady-state error tracking of inverter current and compensate the harmonic distortion caused by frequency fluctuation, a frequency adaptive (FA) control scheme for LCL-type inverter connected with weak grid is proposed. This scheme adopts a proportional resonance (PR) controller in parallel with RC (PRRC) to overcome the disadvantages caused by RC inherent one-cycle time delay. A fractional delay (FD) filter based on the Newton structure is proposed to approximate the fraction item of fs/f, where fs and f are sample frequency and grid frequency, respectively. The structure of the proposed FD filter is relatively simple; moreover, coefficients of the filter maintain constant so as not to need online tuning even when grid frequency fluctuates, which decreases the computational burden considerably. The feasibility and effectiveness of the proposed FA control scheme, named as Newton-FAPRRC, are all verified by the simulation and experimental results.

Download Full-text

PI and Fuzzy-Controlled 3-Phase 4-Wire Interleaved Buck Active Power Filter with Shoot-Through Elimination for Power Quality Improvement using RTDS Hardware

International Journal of Emerging Electric Power Systems ◽

10.1515/ijeeps-2013-0104 ◽

2014 ◽

Vol 15 (2) ◽

pp. 177-194 ◽

Cited By ~ 4

Author(s):

Anup Kumar Panda ◽

Ranjeeta Patel

Keyword(s):

Control Strategy ◽

Fuzzy Logic Controller ◽

Supply Voltage ◽

Harmonic Distortion ◽

Active Power Filter ◽

Active Power ◽

Current Harmonics ◽

Power Filter ◽

Power Quality Improvement ◽

Real Time Digital Simulator

Abstract In this paper, shoot-through current elimination DC–AC converter circuit has been presented with the application of active power filter (APF). The intuitive analysis of the shoot-through in the conventional DC–AC converter has been reported first. Interleaved buck (IB) converter is adopted to eliminate the shoot-through current, thereby increasing the reliability of the interleaved buck–based active power filter (IB-APF). The 3-phase 4-wire IB-APF eliminates the current harmonics produced by the load just as a conventional one does and are innately immune to “shoot-through” phenomenon, with the elimination of special protection features required in conventional inverter circuits. A comparison has been made about the compensation capabilities of the IB-APF with the PI and fuzzy logic controller (FLC) used by id–iq control strategy under different supply voltage conditions. The id–iq control strategy used for extracting the three-phase reference current for IB-APF, evaluating their performance here in MATLAB/Simulink environment and also implemented using real-time digital simulator hardware (OPAL-RT hardware). The RTDS result verifies that the total harmonic distortion percentage of the source current can be reduced below 5% according to IEEE-519 standard recommendations on harmonic limits.

Download Full-text

A local harmonic compensation and power sharing control strategy in islanded microgrid based on PI+repetitive control

2015 Chinese Automation Congress (CAC) ◽

10.1109/cac.2015.7382719 ◽

2015 ◽

Author(s):

Meijie Yi ◽

Mei Su

Keyword(s):

Control Strategy ◽

Repetitive Control ◽

Power Sharing ◽

Harmonic Compensation ◽

Islanded Microgrid

Download Full-text

An internal parallel capacitor control strategy for DC-link voltage stabilization of PMSG-based wind turbine under various fault conditions

Wind Engineering ◽

10.1177/0309524x211060684 ◽

2021 ◽

pp. 0309524X2110606

Author(s):

Mohamed Metwally Mahmoud ◽

Mohamed M Aly ◽

Hossam S Salama ◽

Abdel-Moamen M Abdel-Rahim

Keyword(s):

Wind Turbine ◽

Wind Power ◽

Control Strategy ◽

Low Voltage ◽

Harmonic Distortion ◽

Synchronous Generator ◽

Parallel Capacitor ◽

Wind Generators ◽

Fast Fourier Transform Analysis ◽

Energy Conversion Systems

In recent years, wind energy conversion systems (WECSs) have been growing rapidly. Due to various advantages, a permanent magnet synchronous generator (PMSG) is an appealing solution among different types of wind generators. As wind power penetration level in the grid increases, wind power impacts the grid and vice versa. The most essential concerns in the system are voltage sag and swell, and grid code compliance, particularly for low voltage ride-through (LVRT) and high voltage ride-through (HVRT) capability, is a pressing necessity. This paper presents a parallel capacitor (PC) control strategy to enhance the LVRT and HVRT capability of PMSG. Furthermore, this study presents a method for the sizing of a PC system for the reduction of the overvoltage of the DC-link during voltage sags and swell. Fast Fourier transform analysis is used to determine the total harmonic distortion (THD) for the injected current into the grid. The obtained results illustrate the effectiveness of the proposed system in keeping the DC-link voltage below the limit, power quality improvement, and increasing the LVRT and HVRT capability. Models of wind turbine, PMSG, and PC control system are built using MATLAB/SIMULINK software.

Download Full-text

Composite Control Strategy of Output Current of LCL Photovoltaic Grid-Connected Inverter

Journal of Physics Conference Series ◽

10.1088/1742-6596/2136/1/012015 ◽

2021 ◽

Vol 2136 (1) ◽

pp. 012015

Author(s):

Shengqing Li ◽

Xinluo Li ◽

Qiang Wu ◽

Xiafei Long

Keyword(s):

Control Strategy ◽

Block Diagram ◽

Harmonic Distortion ◽

Harmonic Suppression ◽

Output Current ◽

Control Block ◽

Current Harmonics ◽

Suppression Effect ◽

Composite Control ◽

Grid Connected Inverter

Abstract In order to further optimize the output current harmonic suppression effect of photovoltaic grid-connected inverters, a composite control strategy of LCL type photovoltaic grid-connected inverter output current is proposed. This strategy combines proportional complex integral (PCI) control and repetitive control (RC) in parallel, draws a composite control block diagram, introduces a transfer function, and designs PCI and RC control parameters. Prove that the compound control can reduce current harmonics, achieved the purpose of reducing the steady-state error of the fundamental frequency. And adopts a new PCI composite control strategy, which helps to save the cost of the control system. By building the MATLAB/Simulink simulation platform and establishing the PCI+RC composite control model of LCL photovoltaic grid-connected inverter, the comparison of the simulation results shows that compared with the PI+RC control strategy, the total harmonic distortion rate of the grid-connected current is reduced by 25.77. %, significantly improving the quality of grid-connected current.

Download Full-text