• New & Renewable Energy
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• v.8 no.4
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• pp.13-20
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• 2012

This paper describes a transformerless static synchronous campensator (STATCOM) system based on cascade H-bridge multilevel inverter with star configuration. It is designed not only for the dynamic and continuous compensation of the reactive power but also for the improvement of power quality of existing wind power plant. Especially, when the induction generator of wind turbine is directly connected to the grid, reactive power are occurred by exiting current. so a reactive power compensation system based on the cascade H-bridge multilevel STATCOM is proposed because the output power quality and controllability of reactive power are required by grid code in many different countries. Using various The proposed reactive power control strategy using a STATCOM is compared with the conventional scheme using fixed-size of capacitor bank through various simulation results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1560-1565
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• 2010

The renewable resource are getting more attentions with increased concerns on the depletion of fossil fuels and several environmental issues like emission problem. Wind power is a representative option among several renewable sources and the generation capacity using wind power is being increased. However, the wind generation is so volatile on its output characteristic, so it is required to assess the grid impact of wind power generation by measuring the fluctuation effect more precisely. This paper proposes the method for measuring the generation output according to IEC 61400-21(Measurement and assessment of power quality characteristics of grid connected wind turbines) to assess the power quality of wind turbine generation. In addition, it shows an application case to a small-scale wind power generator. In the case study, it suggests a structure design of the proposed measurement instrument both on hardware and software aspects, which is composed of a remote monitoring & data analysis program and an FPGA based real-time signal processing device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.153-156
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• 2001

Maximum Power Point Tracking(MPPT) is used in wind power generation systems to maximize wind power turbin output power, irrespective of wind speed conditions and of the load electrical characteristics. In this paper we do the equivalent modeling the mechanical energy of wind power turbine according to wind speed into the synchronous generator. We analyse the equivalent modeling output part of rectifier into DC/DC converter input part theoretically. We design a control algorithm for variable voltage according to wind speed intensity and density so that load voltage of chopper is controlled steadily using the maximum power point tracking (MPPT) control method. We analyse a battery charging characteristics and a charging circuit for power storage enabling the supply of stable power to the load. We design a system and do the modeling of it analytically so that it supplies a stable power to the load by constructing a DC-AC inverter point. Also we design a charging circuit usable in actual wind power generation system of 30kW and confirm its validity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.153-156
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• 2001

Maximum Power Point Tracking(MPPT) Is used in wind power generation systems to maximize wind power turbin output power, irrespective of wind speed conditions and of the load electrical characteristics. In this paper we do the equivalent modeling the mechanical energy of wind power turbine according to wind speed into the synchronous generator. We analyse the equivalent modeling output part of rectifier into DC/DC converter input part theoretically. We design a control algorithm for variable voltage according to wind speed intensity and density so that load voltage of chopper is controlled steadily using the maximum power point tracking(MPPT) control method. We analyse a battery charging characteristics and a charging circuit for power storage enabling the supply of stable power to the load. We design a system and do the modeling of it analytically so that it supplies a stable power to the load by constructing a DC-AC inverter point. Also we design a charging circuit usable in actual wind power generation system of 30kW and confirm its validity.

• Journal of Power Electronics
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• v.14 no.2
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• pp.271-281
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• 2014

Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.145-150
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• 2017

This paper present a unified method of steady state performance analysis and limits characteristics of an autonomous three-phase self-excited induction generator (SEIG) driven by a wind turbine under different types of loads and speeds. The proposed method is based on a new mathematical function to solve for the real and imaginary components of the complex equation of the mathematical model. Performances limits, regulation and characteristics of different configurations will be thoroughly examined and compared. The proposed system will be modeled and simulated and the performance limits characteristics will be compared with variable speed and variable capacity.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.265-272
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• 2017

This paper presents the dynamic modeling, analysis, and control of an AC/DC/AC-assisted, self-excited induction generator connected to the grid. The dynamic model includes wind turbine models with pitch control, gear boxes, self-excited induction generators, excitation capacitance, inductive load models, controlled six-pulse rectifiers, and novel state-space models of a grid-connected inverter. The system has been simulated to verify its capabilities of buildup voltage, stator flux response, stator phase current, electromagnetic torque, and magnetizing inductance variation during both the dynamic and steady states with a variable-speed prime mover. The complete setup of the above dynamic models was simulated using MATLAB/SIMULINK.

• Journal of Electrical Engineering and Technology
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• v.7 no.1
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• pp.69-74
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• 2012

This paper presents a distributed winding type axial flux permanent magnet synchronous generator (AFPMSG) with reduced the total harmonic distortion (THD), suitable for wind turbine generation systems. Although the THD of the proposed distributed winding type is more reduced than the concentrated winding type, the unbalance of the phase back EMF occurs. To improve the unbalance of the phase back EMF and the output power of the distributed winding type AFPMSG, the Kriging based on the latin hypercube sampling (LHS) is utilized. Finally, these optimization results are confirmed by experimental results. As a result, the unbalance of the phase back EMF and the output power of the distributed winding type AFPMSG were improved while maintaining the total harmonic distortion (THD) and the average phase back EMF.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2221-2227
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• 2015

To arrest a frequency nadir, a stepwise inertial control (SIC) scheme generates a constant active power reference signal of a wind turbine generator (WTG) immediately after a disturbance and maintains it for the predetermined time. From that point, however, the reference of a WTG abruptly decreases to restore the rotor speed for the predefined period. The abrupt decrease of WTG output power will inevitably cause a second frequency dip. In this paper, we propose a modified SIC scheme of a doubly-fed induction generator (DFIG) that can prevent a second frequency dip. A reference value of the modified SIC scheme consists of a reference for the maximum power point tracking control and a constant value. The former is set to be proportional to the cube of the rotor speed; the latter is determined so that the rotor speed does not reach the minimum operating limit by considering the mechanical power curve of a DFIG. The performance of the modified SIC was investigated for a 100 MW aggregated DFIG-based wind power plant under various wind conditions using an EMTP-RV simulator. The results show that the proposed SIC scheme significantly increases the frequency nadir without causing a second frequency dip.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.4
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• pp.31-38
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• 2000

Wide operating range and speed control is needed for wind power generating and a Doubly Fed Induction Generator(DFIG) has good adaptivity for that purpose. This paper deals with the speed, power, and power factor control using the Grid connected DFIG in the super-synchronous speed regions, by controlling frequency and voltage fed to the rotor. Power flow of the DFIG and steady-state algebraic equations of the equivalent circuit are analyzed. The wind turbine speed and constant stator power were controlled by the rotor exciting frequency. For a normal operating region, in which the generator ratings were not exceeded, rotor exciting frequency. For a normal operating region, in which the generator ratings were not exceeded, the rotor current was either less than or equal to the rated value. Accordingly, the optimal power factor can be selected relative to the permissible rated current at the rotor coil which controls the magnitude of the injected rotor voltage to the rotor according to a given rotor frequency. Consequently, it is possible to determine the optimal drive of a DFIG for wind power generation application.