HALAMAN PENGESAHANcot.unhas.ac.id/seminar/sinastek2018/wp-content/uploads/2018/0… · Web viewThe rotor currents are controlled at any desired phase, frequency and magnitude to

PROSIDING 2015© HASIL PENELITIAN TEKNOLOGI TERAPAN

Volume 9 : Desember 2015

Group Teknik Elektro ISBN : 978-979-127255-0-6

DYNAMIC AND STEADY STATE SIMULATION OF DOUBLY FED INDUCTION GENERATOR (DFIG) ON VARIABLE SPEED CONSTANT FREQUENCY (VSCF) POWER GENERATION

Tajuddin Waris & B. M. Diah

Jurusan Teknik Elektro Fakultas Teknik Universitas HasanuddinJl. Perintis Kemerdekaan Km. 10 Tamalanrea - Makassar, 90245

Telp./Fax: (0411) 588111e-mail: [email protected]

AbstractThis research deals with mathematical modeling and simulation of doubly fed induction generator (DFIG) on Variable Speed Constant Frequency Power Generation. In the system under consideration, the stator is directly connected to the constant frequency three phase grids and the rotor is supplied by two back-to-back three phase voltage source inverters with a common dc link. Such a configuration is attractive in large power applications with limited speed range of operation. The rotor currents are controlled at any desired phase, frequency and magnitude to control the active and reactive powers of the machine independently. A mathematical modeling of DFIG is presented in stator flux oriented model of the doubly-fed wound rotor induction machine is presented. Simulation is presented both in transient and steady state.Keywords: variable speed, power generation, DFIG

INTRODUCTION

There is an increased attention towards doubly fed induction generator controlled from the rotor side for variable speed constant frequency (VSCF) applications. DFIG or wound rotor induction generator has, as the name implies, a rotor containing 3-phase winding. These windings are made accessible to the outside controller via slip rings. The main advantages of DFIG for VSCF applications are: (Waris, Tajuddin.,and C. Nayar., 2007)

Easier generator torque control using rotor current control. Smaller generator capacity as the generated power can be accessed from the stator as well as from the rotor.

Usually the rotor power is proportional to the slip speed (shaft speed-synchronous speed). Smaller capacity for the power electronics, rated at 20-30% of the nominal generator power.

The possibility of accessing the rotor in a doubly fed induction generator enables a number of control configurations possible. These include slip power recovery using a cyclo-converter, which converts ac voltage of one frequency to another without an intermediate dc link or back to back converter configurations. Fig. 1 shows the application of DFIG on variable diesel Generator using PWM back to back converter.

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Dynamic and Steady State… Tajuddin W. & B. M. Diah


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Figure 1. Variable Power Generation with Doubly Fed Induction Generator using Back to Back PWM Converter

With a PWM converter connected in the rotor circuit, the rotor currents can be controlled in a desired phase, frequency and magnitude. This enables reversible flow of active power in the rotor and the system would be operated in sub-synchronous and super-synchronous speed. The dc link capacitor acts as a source of reactive power and it is possible to supply the magnetizing current, partially or fully, from the rotor side. Therefore the stator side power factor can also be controlled. Using vector control techniques, the active and reactive powers can be controlled independently and hence fast dynamic performance can be achieved

The converter used at the grid interface is termed as the line-side converter or the Grid Side Converter (GSC) and operates at the grid frequency. Flow of active and reactive powers is controlled by adjusting the phase and amplitude of the inverter terminal voltage respect to the grid voltage. Active power can be either injected or absorbed to the rotor circuit depending on the mode of operation. In which, the dc bus voltage is regulated within a small band. Control of reactive power enables unity power factor operation at the grid interface. In fact, the GSC can be operated at a leading and lagging power factor. Due to the slip range is limited as a consequence the dc bus voltage is less in comparison with the stator voltage. Therefore, a transformer is necessary to match the voltage levels between the grid and the dc side of the GSC. (Waris,Tajuddin., and C. Nayar., 2008)

MATHEMATIC MODELING OF DFIG The stator and rotor winding of DFIG can be assumed as two balanced three-phase windings coupled with each other. In which, Clark transformation may be applied for simplification by reducing a coupled balanced of three-phase winding into an uncoupled two-phase winding. By doing so, the machine equations can be expressed with respect to a reference frame rotating with the synchronous speed. (Richard,G., 2005)

For transforming stator equation to field coordinate, both stator - rotor voltages and current have to be priory transformed from their natural reference frames. It means, the stator current and voltage components are referred to a stationary reference frame, while the rotor current and rotor voltage are referred to rotor reference frame (Liu Xu, Yi Wang, 2007). Relationship coordinate system and angle determination is presented in Fig.2

The general mathematical model of symmetrical induction machine may be applied to generate the mathematical model of DFIG. Single line diagram of DFIG is presented in Fig. 3.

ISBN : 978-979-127255-0-6

Group Teknik Elektro Volume 6 : Desember 2012

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d axis

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Figure 2. Phasor Diagram of Stator Flux Orientation

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Based on Fig 3, the vectorial stator and rotor voltage equation in stator reference can be generated as given in equation 1-2.

(1)

(2)

Then, the stator voltage equation (1) and the rotor voltage equation (2) are used for designing the grid side converter (GSC) and the rotor side converter (RSC) respectively. By assuming that rotor side is a controllable current source with current injecting capability at appropriate phase, frequency and magnitude to the machine. So, these rotor currents are transformed to the stator reference frame using operator. Thus, Fig.3 could be transformed as presented in Fig.4.

The, stator voltage equation (1) can be re-written as follows.

(3)

(4)

Where, is magnetizing current which is responsible generating stator flux.

(5)

Because the control parameter is in rotor currents quantity, thus equation (3) needs to be formed as the rotor currents and magnetizing currents quantity. It can be realized by using equation (5), results in.

(6)

or,


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Figure 3. Single Line Diagram of DFIG

Figure 4. Equivalent Circuit of DFIG with Rotor as Controllable Current Sources

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Left indentMASIH KELIRU(harusnya 0,95)

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(7)

SIMULATION RESULTS

The entire system is simulated on the MATLAB-SIMULINK platform. `Fig 1 shows instantaneous stator voltage and stator current in steady state. Its frequency, magnitude and phase is independent from the rotor speed. In grid connected stator flux is maintained constant by grid. In stand alone mode, stator flux is keep constant by RSC.

Fig. 6 presents rotor voltage around synchronous speed. Its magnitude, frequency and phase depend on mechanical rotor speed.

CONCLUSIONS

This paper presented mathematical modelling of DFIG in VSCF power generation. For clarifying the mathematical modelling, simulation results both in dynamic and steady state also be presented. It shown that VSCF with DFIG provides better performance due to control flexibility. Decoupled control both rotor side converter (GSC) and rotor side converter (RSC) enable this system will be more flexible in controlling active reactive power. The capability of DFIG in providing power from both stator and rotor side enables optimizing of the prime mover capacity. With a PWM converter in the rotor circuit, the rotor currents can be controlled in a desired phase, frequency and magnitude. This enables reversible flow of active power in the rotor and the system can operate in sub synchronous and super-synchronous speeds generating modes

REFERENCES

Waris, Tajuddin., and C. Nayar., 2007. “Variable Speed Power Generation with DFIG”, Proceeding of the Australasia Power Electrical Conference (AUPEC) Perth, W.,A 2007, pp. 352-365.

Richard,G., 2005. Modelling and Real Time Simulation of a Doubly Fed Induction Generator driven by Wind Turbine , Presented at International Transients (IPTS 05) , in Montreal Canada June 19, 2005 Klir, J., and Yuan, B., 2001..

ISBN : 978-979-127255-0-6


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Figure 5. Simulated instantaneous stator voltage and current voltage

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CATATAN

1. Pengaturan Margin


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2. Pengaturan paragraf di setting (kemungkinan harus selalu di cek dan di setting berulang-ulang):

3. Setiap artikel diupayakan jumlah halamannya GENAP (misalnya 8, 10 atau 12 halaman) agar artikel selanjutnya dapat dimulai lagi pada halaman GANJIL.

ISBN : 978-979-127255-0-6


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4. Mohon aktifkan fitur proofing language untuk memeriksa kesalahan penulisan maupun ejaaannya.Kami sertakan data base proofing bahasa Indonesia yang dapat digabung dengan data base proofing default-nya MS word, English (United States)


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HALAMAN PENGESAHANcot.unhas.ac.id/seminar/sinastek2018/wp-content/uploads/2018/0… · Web viewThe rotor currents are controlled at any desired phase, frequency and magnitude to