S. Y. Mosazade ¹, S. H. Fathi ¹, H. Radmanesh ²

Affiliations
1 Electrical Engineering Department, Amirkabir University of Technology, Tehran, IR
2 Department of Electrical Engineering, Islamic Azad University, Takestan Branch, Takestan, IR

Abstract

In this paper different high frequency switching methods for multilevel inverters which has been proposed for PV applications is analyzed; furthermore, the output harmonics content of phase shifted PWM (PSPWM) and in phase disposition PWM (IPDPWM) switching methods are comprised. This simulation results show that total harmonics content in IPDPWM is less than PSPWM method; besides, modified switching method of IPDPWM which solves the unequal power sharing problem of it is also proposed. This switching method is applied to a 7 levels inverter which is fed by three PV array DC sources and supply an AC load. These PV arrays deliver maximum power via DC-DC converter and perturb and observe algorithm. Simulation results show effectiveness of this method in sharing equal powers among different cells of the multilevel inverter which are supposed to be PV arrays; furthermore, results show that DC voltage ripples which cause inter harmonics are less than previous similar switching method; Hence for allowable DC voltage ripple, smaller capacitor is required. Simulation is implemented by MATLAB/SIMULINK software.

Keywords

Multilevel Inverter, Photovoltaic System, Power Conditioning

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M. Nasiri ¹, J. Milimonfared ¹, S. H. Fathi ¹

Affiliations
1 Department of Electrical Engineering, Amirkabir University of Technology, Tehran, 15875–4413, IR

Abstract

This paper presents modeling of a direct-driven permanent magnet synchronous generator – based wind turbine and proposes a new controller for Back-To-Back (BTB) converters to enhance Low Voltage Ride Through (LVRT). The LVRT is implemented without any additional devices during grid fault conditions. In this structure, the Proportional-Integral (PI) controllers of Machine Side Converter (MSC) and Grid Side Converter (GSC) are replaced by Sliding Mode (SM) controllers. The MSC controls dc-link voltage and the GSC controls Maximum Power Point Tracking (MPPT) by regulating turbine-generator speed. This control strategy implements different grid code requirements such as Danish grid code. The proposed SM controller in comparison with the PI controller can eliminate dc-link voltage oscillations and reduce the converter voltage and current stresses. Simulation results verify the robustness and effectiveness of the proposed strategy. Hence, by using SM controller, there is no need for additional equipments to enhance LVRT in PMSG-based wind turbines and cost and complexity are significantly reduced.

Keywords

DC-Link Voltage, Low Voltage Ride-Through (LVRT), PMSG, Sliding Mode Control, Wind Energy

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Roozbeh Kamali ¹, Reza Sharifi ², Hamid Radmanesh ¹, S. H. Fathi ²

Affiliations
1 Electrical Engineering Department, Aeronautical University of Science and Technology, Tehran, IR
2 Electrical Engineering Department, Amirkabir University of Technology, Tehran, IR

Abstract

This paper present an Artificial Neural Network (ANN) model for online profile voltage estimation to aim distribution network voltage regulation with consider Distributed Generation (DG). Arrival of DG to the distribution network affect the feeder voltages. Commonly, the On-Load Tap Changer (OLTC) transformer with a Line Drop Compensation (LDC) that monitors the voltage along the feeder is used to regulate the voltage within allowable limits. But with presence DG because of multi-directional power flow, there are complications for the operation of the LDC to detect the correct amount of voltage profile along the feeder. The proposed estimation method employs Artificial Neural Network (ANN) concept and eliminates utilization of power flow calculations, resulting in low computational burden and online operation especially in case of systems with high order of complexity. Proposed technique is tested on a 13 bus distribution network and simulation outcomes validate effectiveness and efficiency of the suggested scheme.

Keywords

Artificial Neural Network (ANN), Distributed Generation, On-Load Tap Changer.

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