Analysis the Transient Process of Wind Power Resources when there are Voltage Sags in Distribution Grid

Transcription

1 Analyi the Tranient Proce of Wind Power Reource when there are Voltage Sag in Ditribution Grid Do Nhu Y 1,* 1 Hanoi Univerity of ining and Geology, Deartment of Electrification, Electromechanic Faculty, Viet Nam Abtract. Vietnam ha many advantage of wind ower reource. Time by time there are more and more caacity a well a number of wind ower roject in Vietnam. Correonding to the increae of wind ower emitted into national grid, It i neceary to reearch and analyze in order to enure the afety and reliability of win ower connection. In national ditribution grid, voltage ag occur regularly, it can trongly influence on the oeration of wind ower. The mot eriou conequence i the diconnection. The aer reent the analyi of ditribution grid tranient roce when voltage i agged. Bae on the analyi, the olution will be recommended to imrove the reliability and effective oeration of wind ower reource. Key word wind ower, tranition roce, reliability. 1 Introduction Wind ower i renewable and green energy in Vietnam. According to accounting data, Vietnam ha rich wind ower caacity with 8,6% area that i alicable to build u big wind ower tation, among that 41% area in urban area i uitable to build mall tation. Total caacity of wind ower i about W [1] Voltage ag i a oular henomenon in ower ytem that make wind ower arameter changed. Therefore analyzing the tranient of wind ower ource at voltage ag moment, in order to recommend uitable oeration for ower ytem containing wind ower, lay an imortant meaning. Reearch method Nowaday, mot of wind ower tation utilize Double-feed-Induction-Generator (DFIG) becaue they have the rior advantage when tator i directly connected to the grid wherea rotor i connected to the grid through controllable ower electronic device. Becaue the controller in rotor, therefore it ower i much maller than the ower of generator; ower flow directly from tator to grid, eecially with big caacity generator. In the limit range * Correonding author: donhuy@humg.edu.vn; donhuy.humg@gmail.com The Author, ublihed by EDP Science. Thi i an oen acce article ditributed under the term of the Creative Common Attribution Licene 4.0 (htt://creativecommon.org/licene/by/4.0/).

2 of eed, the ower of converter i only 30% grid tranmitting ower. The tructure of wind ower generator DFIG i hown in Figure 1 [3]. Fig. 1. Structure of wind ower DFIG In Figure 1 (SC) i the converter on generator ide ued to control generator eed in order to get maximum ower. Inut ignal of eed controller i deducted from wind velocity. Outut ignal of eed controller i the ref ignal for ower loo controller. Grid ource converter (GCS) control DC voltage ( ). dc U It i alo ued to control reactive ower Q. To analyze the tranient occurred in wind ower when there i voltage ag, ower ytem i imulated on atlab-simulink. Power generator DFIG i imulated on dq axi a Figure. Fig.. Simulation of DFIG generator on ace vector Relacing equivalent model of DIFG i exreed in tator ace vector a hown in Figure 3. Fig. 3. Equivalent diagram of DFIG on ace vector

3 Where: R tator winding reitor; L agnetic induction; L Induction of tatorand rotorconverted into tator ide; R R Rotor reitor converted to tator. Letter mean ace vector ref on tatorof DFIG. According to [], Kirchhoff equation for loo circuit: u u Ri d Ri d S S S S R R R R (1) The field of tator, rotor, and electromagnetic torque are comuted by the following equation: L i i S S R L i L i i R R S R * Te 3Z I m i R Where: L agnetizing induction; L Convert induction () L gl L S l rl Ll L L (3) Where: Convert factor; Ll ; L rl Induction oftator, rotor; Z generator ole air. echanical equation of ytem i exreed by: J Z d r T e T (4) Where: J Inertia torque; r rotor rotating velocity; mechanic torque on rotor haft. T e electromagnetic torque;t ath exreion of filter on grid ide include Rf and Lf, relace model i hown in Figure 4. Fig. 4. odel of filter on grid ide in ace vector 3

4 According to [], Kirchhoff equation on dq axie: di f Eg Ri f f Lf uf (5) ath exreion of DC Link, relaced model i hown in Figure 5. Fig. 5. odel of DC Link EnergyW dc i deducted from caacitor C and i comuted by the following equation: W 1 C U dc dc dc dwdc 1 d C u P P dc dc f r d Cdcudc udc Pf Pr (7) Outut ower of wind generator i calculated by: A 3 Pm C, (8) Where: P m Outut ower of wind turbine; C (, ) ower converion factor (ratio of wing velocity and wing angle ); A cro ection of; air denity; wind velocity. Power converion factor C i determined a: C 1 i e 116, 0, , 45 0, , ,08 1 i (9) Ratio of wing velocity and wind velocity i determined by: R (10) Where: Turbine rotating velocity; R Turbine radiou 4

5 On other hand wind turbine can be oerated by different controlling rule bae on wind velocity. Figure 6 i the exreion of relation between wind turbine ower and wind velocity. Fig. 6. The relation of wind turbine ower and wind velocity Utilizing the imulation on atlab-simulink, above mentioned equation are exreed in Figure 7 []. Fig. 7. Simulation diagram 3 Reult Simulation reult are imlemented on ytem with the following arameter: outut voltage 690 V, te-u tranformer i 690 V/ kv, the wind ower ytem i connected with ower ytem on kv bu bar. In the oeration of the ytem, there i a voltage ag, conequently voltage on kv bu bar i reduced (a hown in Figure 8 The tranient roce of outut voltage of wind ower i hown in Figure 9, the current changing i reented in Figure 10 and the tranient velocity of motor i on Figure 11. Fig. 8. Voltage on kv bu bar (B) 5

6 Fig. 9. Reone voltage of wind ower Fig. 10. Reone current of wind ower Fig. 11. The tranient of generator velocity The above imulation how that, when there i voltage ag on ditribution grid ( kv bu bar) outut voltage of generator i alo down (Fig. 9), conequently current of generator i increaed (Fig. 10). If the roce i long lating can caue over load or detroy the generator. At the moment of voltage recovery, wind ower voltage i alo recovered, but it i tranient much over rated voltage. Thi caue to the tranient of generator velocity (Fig. 11). 4 Concluion Wind ower i increaed raidly in both quantitie and caacity. The Power ytem containing wind ower reource need a table oeration becaue it voltage ag could decreae the outut voltage of generator. Conequently, generator current will increae. The long lating increaing of current could lead to over load or detroy the generator.furthermore, at the moment of votage recovery on ditribution grid, voltage i alo fluctuated raidly. The imulation reult exre the tranient of wind ower energy at the moment of voltage ag in ditribution grid. The reult will be ued to recommended olution for imroving the tabilitie, effectivene of wind ower. Reference 1. Do Nhu Y, Le Xuan Thanh, Imrovement to the oreation of wind ower genertor in Vietnam, Journal of Vietnam Environment (ISSN ), Vol. 8, , (016). Do Nhu Y, Reearch uing SVC to Imrove the Oeration of Wind Power generator in Vietnam, Euroean of technology Journal and deign, Vol. 14, , (016) 3. Lai Khac Lai, Duong Quoc Hung, Tran Thi Thanh Hai, Deign the grid ynchronizing controller for wind ower uing Double-Feed Induction Generator DIFG, Journal of Science and Technology, Vol. 10,. 19 5, (010) 6