• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.182-187
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• 2017

Synchronous generators have been significantly applied in large-scale power plants and its monitoring systems are additionally established to sequentially observe states and outputs. We develop a computer based monitoring device for three-phase synchronous power generators in this paper. First, a test-bed of such generator system is created and then a interface board is constructed to transfer electric signals including the output voltage and the current from generators into a computer system via a data acquisition device. Its RMS(root-mean-square) values are continuously shown on a screen of computer systems and its time-histories graphs are additionally illustrated under a graphic user interface(GUI) mode. Lastly, we carry out real-time experiments using the generator system with the monitoring device to demonstrate its reliability and superiority by comparing results of a generic power analyzer which is well-used in measuring various power systems practically.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.4
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• pp.157-169
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• 2004

Motor & generator operation at widely variable speeds is needed in various applications but hybrid and electric vehicle (HEV) stand out today, as quite a few companies are launching this year their mass production of HEVs. The quest for better starter-generators is far from ended, though. The present review paper unfolds a comparative critical evaluation of various starter-generators and their control for HEV. Induction, interior PM synchronous, transverse-flux PM synchronous, switched reluctance, together with claw-pole and biaxial excitation PM synchronous (BEGA) configurations with their control are all considered in system evaluations.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.179.2-179.2
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• 2010

This research has been performed to provide fundamental design aspects of Permanent Magnet Synchronous Generators(PMSGs) for a kilowatt class wind turbine. When it comes to kilowatt class wind turbines, the typical type of generators are Axial Flux Permanent Magnet(AFPM) generators. However, Radial Flux Permanent Magnet(RFPM) generators have been optimally designed to study the output characteristics of a kilowatt class wind turbine in Graduate School of Wind Energy, POSTECH. An existing squirrel-cage rotor has been modified for another newly designed permanent magnet rotor to utilize the commercially existing stator rotor. Electromagnetic analysis utilizing Finite Element Methods tools(ANSYS, MAXWELL 2D) has been applied to analyze the system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.561-568
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• 2018

Passivity theory is significantly applied to analyze stability of nonlinear dynamic systems and construct its stable control systems. This paper presents a passivity based control design approach for exciters and governors which are employed to regulate the terminal voltage and the rotor velocity of synchronous generator systems in industry fields. We consider the IEEE type 1 exciter and the gas turbine (GT) governor models respectively in this paper. We first carry out a passivity analysis for exciter and governor control systems, which are numerically obtained from its mathematical models. And then its control parameters are selected to assure passivity conditions in a design procedure. Lastly, we investigate numerical simulations to demonstrate reliability of the proposed control approach against large-scale generators with parameter changes.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.10
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• pp.494-500
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• 2001

This paper presents the shape optimization to minimize the BEMF(Back Electro-Motive Force) harmonics of PM type synchronous generators. RSM(Response Surface Methodology) is well adapted to make analytical model for a complex problem considering a lot of interaction of design variables. In this paper, RSM is used to find the optimal solution. The 2D-Finite Element Method is used to obtain the observer data of the BEMF and SQP(Sequential Quadratic Problem method) is used to solve the constrained nonlinear optimization problem.

• Journal of Power Electronics
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• v.14 no.5
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• pp.859-865
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• 2014

This study presents an electromagnetic model for predicting shaft voltages in a 2-pole field-excited synchronous generator. After the first observations on shaft voltages were made more than a century ago, extensive work has been conducted on eliminating, mitigating, and integrating the aforementioned phenomena. Given that emphasis has been placed on modeling shaft- and bearing-induced voltages in AC motors driven by variable frequency drives, similar efforts toward a model that is dedicated to generators are insubstantial. This work endeavors to improve current physical interpretation and prediction methods for shaft-induced voltages in generators through semi-analytical derivation. Aside from the experimental validation of the model, investigations regarding the behavior of shaft voltages under varying machine complexities and operating conditions clarify previous uncertainties regarding these phenomena. The performance of the numerical method is also assessed for application in eccentricity fault diagnosis.

• Journal of the Korean Solar Energy Society
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• v.23 no.3
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• pp.29-35
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• 2003

Generator for wind power can be either synchronous or asynchronous (induction) types. Induction and synchronous generators behave in a different way when subjected to severe faults. Induction generators does not have an angle stability limit and short circuit in the neighborhood of an Induction generator causes the demagnetization of the machine when the fault is cleared, the voltage raises slowly, while the grid contributes with reactive power to the generator and the magnetic flux recovers. On the other hand in the synchronous generators the recovery of the voltage is immediate, since the excitation of the rotor angle comes from an independent circuit. This paper shows the result of the transient state analysis in the network connected to wind generation system Several case studies have been conducted to determine the effect of the clearing time of a fault on the network stability. It has been found that the critical clearing time can be as low as 61ms in the case of induction generator compared to 370ms in the case of synchronous generator.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2192-2201
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• 2016

Wind energy is currently the fastest-growing electricity source worldwide. The cost efficiency of wind generators must be high because these generators have to compete with other energy sources. In this paper, a system that utilizes an open-winding permanent-magnet synchronous generator is studied for wind-energy generation. The proposed system controls generated power through an auxiliary voltage source inverter. The VA rating of the auxiliary inverter is only a fraction of the system-rated power. An adjusted control system, which consists of two main parts, is implemented to control the generator power and the grid-side converter. This paper introduces a study on the effect of unbalanced voltages for the wind-generation system. The proposed system is designed and simulated using MATLAB/Simulink software. Theoretical and experimental results verify the validity of the proposed system to achieve the power management requirements for balanced and unbalanced voltage conditions of the grid.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2221-2230
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• 2016

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 kW prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

• Journal of Power Electronics
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• v.18 no.1
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• pp.195-203
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• 2018

In the variable speed Wind Turbine based on ElectroMagnetic Coupler (WT-EMC), a synchronous generator is coupled directly to the grid. Therefore, like conventional power plants, WT-EMC is able to inherently support grid frequency. However, due to the reduced inertia of the synchronous generator, WT-EMC is expected to be controlled to increase its output power in response to a grid frequency drop to support grid frequency. Similar to the grid frequency support control of Type 3 or Type 4 wind turbine, inertial control and droop control can be used to calculate the WT-EMC additional output power reference according to the synchronous generator speed. In this paper, an experimental platform is built to study the grid frequency support from WT-EMC with inertial control and droop control. Two synchronous generators, driven by two induction motors controlled by two converters, are used to emulate the synchronous generators in conventional power plants and in WT-EMCs respectively. The effectiveness of the grid frequency support from WT-EMC with inertial control and droop control responding to a grid frequency drop is validated by experimental results. The selection of the grid frequency support controller and its gain for WT-EMC is analyzed briefly.