• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1219-1226
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• 2014

This paper introduces a hardware simulator for the LVRT operation analysis of the grid-tied PMSG wind power system with a power dissipation circuit. The power dissipation circuit, which is composed of chopper and resistor, suppresses the sudden increase of DC-link voltage in the back-to-back converter of the grid-tied PMSG wind power system. The LVRT operation was first analyzed using computer simulations with PSCAD/EMTDC. A wind power simulator including the power dissipation circuit and the fault simulator composed of variac and IGBT were built to analyze the LVRT operation. Various experiments were conducted to verify the effectiveness of the power dissipation circuit for the LVRT operation. The developed hardware simulator can be extensively utilized for the analysis of various LVRT operations of the grid-tied wind power system.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.375-383
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• 2011

This paper describes a real-time hardware simulator for a grid-tied Permanent Magnet Synchronous Generator (PMSG) wind power system, which consists of an anemometer, a data logger, a motor-generator set with vector drive, and a back-to-back power converter with a digital signal processor (DSP) controller. The anemometer measures real wind speed, and the data is sent to the data logger to calculate the turbine torque. The calculated torque is sent to the vector drive for the induction motor after it is scaled down to the rated simulator power. The motor generates the mechanical power for the PMSG, and the generated electrical power is connected to the grid through a back-to-back converter. The generator-side converter in a back-to-back converter operates in current control mode to track the maximum power point at the given wind speed. The grid-side converter operates to control the direct current link voltage and to correct the power factor. The developed simulator can be used to analyze various mechanical and electrical characteristics of a grid-tied PMSG wind power system. It can also be utilized to educate students or engineers on the operation of grid-tied PMSG wind power system.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.385-393
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• 2020

This study introduces an analysis and control method for the variation of neutral point current in a grid-tied three-level neutral point clamped (NPC) converter under various grid imbalance operating conditions. Various fault cases with unbalanced amplitude and phase are systematically categorized and described using a unified metric called the imbalance factor. The fundamental component of neutral point current is generated under grid imbalance cases. The pattern and behavior of this fundamental component of neutral point current highly depend on the imbalance factor regardless of the particular type of grid fault cases. The control scheme for regulating the negative sequential component of AC input current effectively reduces the size of the fundamental component of neutral point current under a wide range of grid imbalance cases. The control scheme will enable a grid-tied three-level NPC converter to operate reliably and stably under various types of grid faults.

• Advances in Energy Research
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• v.8 no.1
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• pp.59-71
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• 2022

Increasing cost of electricity due to rising price of fuel is one of the local community's main issues. In this research, switching of grid dependent system to the grid-tied Photovoltaic (PV) system with net metering for a residential building is proposed. The system is designed by considering the maximum energy demand of the building. The designed system is analyzed using RETScreen on technical, economic and environmental grounds. It is found that the system is able to produce 12,000 kWh/year. The system is capable to fulfill the electricity demand of the building during day time and is also capable to sell the energy to the local grid causing the electric meter to run in reverse direction. During night time, electricity will be purchased from grid, and electric meter will run in the forward direction. The system is economically justified with a payback period of only 3 years with net present value of PKR. 4,758,132. Also, the system is able to reduce 7.2 tons of CO₂ not produced in the entire life of the project.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1400-1408
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• 2013

This paper proposes a new grid-tied power converter for battery energy storage, which is composed of a 2-stage DC-DC converter and a PWM inverter. The 2-stage DC-DC converter is composed of an LLC resonant converter connected in cascade with a 2-quadrant hybrid-switching chopper. The LLC resonant converter operates in constant duty ratio, while the 2-quadrant hybrid-switching chopper operates in variable duty ratio for voltage regulation. The operation of proposed system was verified through computer simulations. Based on computer simulations, a hardware prototype was built and tested to confirm the technical feasibility of proposed system. The proposed system could have relatively higher efficiency and smaller size than the existing system.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.77-79
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• 2007

The phase angle of the utility voltage is used in current control of grid-tied fuel cell power converter. Therefore if the detection of phase angle is a problem, Current control is affected by the distorted phase angle. This paper presents a problem of synchronous reference frame PLL algorithm for single-phase systems and proposes compensated synchronous reference frame PLL algorithm. The proposed method helps power quality improvement of grid-tied fuel cell power converter under distorted utility conditions. Simulation and experimental results are presented to demonstrate the validity of the proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.41-49
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• 2012

This paper describes the operation mode development for the grid-tied PMSG(permanent magnet synchronous generator) wind power system combined with a battery energy storage. The development of operation modes was carried out through simulations with PSCAD/EMTDC software and experiments with a 10kW hardware prototype. The detailed simulation models for PMSG wind power system and battery energy storage were developed using user-defined models programed with C-code. A 10kW hardware simulator was built and tested in connection with the local load and the utility power. The simulation and experimental results confirm that the grid-tied PMSG wind power system combined with battery energy storage can supply highly reliable power to the local load in various operation modes.

• Journal of Power Electronics
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• v.16 no.1
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• pp.18-26
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• 2016

This paper proposes a compensation algorithm for reducing a specific ripple component on synchronous reference frame phase locked loop (SRF-PLL) in grid-tied single-phase inverters. In general, SRF-PLL, which is based on all-pass filter to generate virtual voltage, is widely used to estimate the grid phase angle in a single-phase system. In reality, the estimated grid phase angle might be distorted because the phase difference between actual and virtual voltages is not 90 degrees. That is, the phase error is caused by the difference between cut-off frequency of all-pass filter and grid frequency under grid frequency variation. Therefore, the effects on phase angle and output current attributed to the phase error are mathematically analyzed in this paper. In addition, the proportional resonant (PR) controller is adapted to reduce the effects of phase error. The validity of the proposed algorithm is verified through several simulations and experiments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.73-82
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• 2015

This paper proposes an ripple reduction algorithm and analyzes the effects of offset and scale errors generated by voltage sensor while measuring grid voltage in grid-tied single-phase inverters. Generally, the grid-connected inverter needs to detect the phase angle information by measuring grid voltage for synchronization, so that the single-phase inverter can be accurately driven based on estimated phase angle information. However, offset and scale errors are inevitably generated owing to the non-linear characteristics of voltage sensor and these errors affect that the phase angle includes 1st harmonic component under using SRF-PLL(Synchronous Reference Frame - Phase Locked Loop) system for detecting grid phase angle. Also, the performance of the overall system is degraded from the distorted phase angle including the specific harmonic component. As a result, in this paper, offset and scale error due to the voltage sensor in single-phase grid connected inverter under SRF-PLL is analyzed in detail and proportional resonant controller is used to reduce the ripples caused by the offset error. Especially, the integrator output of PI(Proportional Integral) controller in SRF-PLL is selected as an input signal of the proportional resonant controller. Simulation and experiment are performed to verify the effectiveness of the proposed algorithm.

• Journal of Power Electronics
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• v.10 no.1
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• pp.97-105
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• 2010

This paper presents the modeling, control and simulation of an interconnection system (ICS) of cascaded distributed generation (DG) modules for both grid-tied and stand-alone operations. The overall configuration of the interconnection system is given. The interconnection system consists of a cascaded DC/DC boost converters and a DC/AC inverter. Detailed modeling of the interconnection system incorporating a cascaded architecture has not been considered in previous research. In this paper, suitable control systems for the cascaded architecture of power electronic converters in an interconnection system have been studied and modeled in detail. A novel control system for DC/DC boost converters is presented based on a droop voltage controller. Also, a novel control strategy for DC/AC inverters based on the average large signal model to control the aggregated DG modules under both grid-tied and stand-alone modes is demonstrated. Simulation results indicate the effectiveness of the proposed control systems.