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Statik var kompanzatörü ile reaktif güç kontrolü ve kompanzasyonu

Başlık çevirisi mevcut değil.

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  1. Tez No: 75431
  2. Yazar: OKAN İHSAN ÖZTÜRK
  3. Danışmanlar: PROF. DR. NESRİN TARKAN
  4. Tez Türü: Yüksek Lisans
  5. Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
  6. Anahtar Kelimeler: Kompansatör, Reaktif güç kompanzasyonu, Compensator, Reactive power compensation
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Elektrik Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: Belirtilmemiş.

Özet

Alternatif akım sistemlerinde fazların dengeli olması ve reaktif gücün kontrolü kayıpların minimize edilmesi ve sistemin enerji kapasitesinin arttırılabilmesi için gereklidirler.Tezde. bunların gerçeklenebilmesi için gerekli matematiksel ifadeler çıkartılmış, tristör kontrollü statik VAR kompanzatörleri ele alınmış, dengesiz yüklerin dengelenmesi incelenmiştir.Tezde yapılan çalışmalar şöyle özetlenebilir. Birinci bölümde, reaktif güç kompanzasyonunun gerekliliği vurgulanmış ve izlenen yöntem hakkında genel bilgi verilmiştir. ikinci bölümde, reaktif güç kompanzasyon tanımı, matematiksel esaslar ve temel tanımlar verilmiş, şebeke ve tüketiciler açısından faydalan incelenmiştir. Üçüncü bölümde, kompanzasyon tesislerinin kurulmasının temel ilkeleri incelenmiştir. Dördüncü bölümde, yük kompanzasyonunun temel esasları verilmiş olup simetrili bileşen akımları cinsinden matematiksel ifadeler çıkartılmıştır. Aynı zamanda optimum kondansatör hesabı için akış diyagramı oluşturulmuş ve EK-B'de bu akış diyagramını kullanarak yazılan MATLAB programı bir örnekle verilmiştir. Beşinci bölümde, alternatif akım kıyıcısı ile kompanzasyon anlatılmış ve statik kompanzatörün çeşitli karakteristikleri incelenmiştir. Altıncı bölümde statik kompanzatör için gerekli kontrol devresi incelenmiş, bir fazlı devre modeli verilmiş ve PID kontrolör kullanılarak kapalı çevrimli reaktif güç kontrolünü sağlayan bir sistemin akış diyagramı çıkarılmış ve MATLAB programı yapılarak bir örnek üzerine uygulanmıştır. XII

Özet (Çeviri)

In recent years, there has been greatly increased demand for reactive power compensation network to improve the power systems quality. This thesis concerns the application of static reactive compensators (SVCs) to power transmission systems. Emphasis is placed on controlling the SVC systems. The static VAR compensator (SVC) is an integrated system of static electrical components ( e.g. capacitors, reactors, transformers...) combined in such manner to provide rapid, continuously controllable shunt reactive power compensation. In this thesis static VAR compensators, namely Thyristor controlled reactor- fixed capacitor is used as reactive devices. Therefore its possible to control large and rapid variation in the reactive power due to the loads and generation. Two types of compensation problems are normally encountered in practically applications. The first type compensation is load compensation where the requirements are usually to reduce or cancel recactive power demand of large fluctuating industrial loads such as electric arc furnaces, rolling mills, etc. and to balance the real power drawn from the ac supply lines. This types of heavy industrial loads are normally concentrated in one plant and served from one network terminal and therefore can be handled best by a local compensators connected to the same terminal. The second type of compensation is releated to the voltage support of transmission lines ata given terinal in the face of disturbance of both loads and generation. Here the load is not localized several loads and generation units may be tied by transmission network and the objective is the simply to regulate the voltage at the compensator terminal. In the second chapter the load compensation requirements and reactive power releationship are discussed. Load compensation is the management of reactive power to improve the quality of supply in ac power systems. The term load compensation is used where the reactive power management is affected for a single load, the compensating equipment usually being installed on the consumer's own premises near to the load. The techniqiues used, and indeed some of the objectives, differ considerably from those met in the compensation of bulk supply networks (transmission compensation). In load compensation there are three main objectives: Power factor correction Improvement of voltage regulation Load balancing XlllPower factor correction and load balancing are desirable even when the supply voltage is very“stiff (constant and independent of the load. These requirements are supplied by compensators. In the third chapter the local and center compensation are explained. Local compansations specially for the asynchronous motors, transformers are examined in this section. In the forth chapter reactive power problem is considered by using mathematical equaitons. A general three phase delta connected load can be considered with compensators show in figure 1. Figure I. Three phase unbalanced loads represented by delta connected admittance and th delta connected compensator. If the load admitance are composed of real component and reactive component. Y- Y,, Gab + j Bab Gbc+j Bbc Gbc+ j Bca d) The reactive parts can as a fisrt step of the compensation, be cancelled by an appropriate compensating suseptance -Bab, -Bbc. -Bca. As a second step of the compensation, real admitance has to be complemented with a reactive admitance network so as to obtain a resultant balanced load on the ac supply. This reactive admitances are r> tabl_. ^-r q «abı _. ”be -J -. Dca - -J B. ib. «._ : <?, j ~t - Bab (bo _. Çk_ V3 (2) XIVab - J r-. Dbc ~ "J V3 Superscript (ab). (be), (ca) are used the indicate that the suseptances are needed to compensate phases ab. be and ca. Subscript ab. be and ca are shown reactive suseptances which are connected to the phases. The three suseptances required to compensate a general unbalanced load, can be expressed in term of the real and reactive ports of the oad admitance. that is. Bab(c' = -jBab + j(Gac-Gbc)/ V3 Bbc,c, = -jBbc + j(Gab-Gca)/V3 (3) Bca,c' = -jBca+j(Gbc-Gab)/ V3 This equaition transform any linear unbalanced reactive load into balanced real load. It is difficult to measure load admitances therefore it can be used symmetrically component analysis to determine compensator suseptances. The objectives of load compensation can be stated in terms of the symmetrical line current components as folllows:. Eliminate the negative sequence components (balancing).. Eliminate the reactive part of the positive sequence components The compensation requirements can be formulated mathematically as follows: Ia2 - Ia: ' c ' = 0 imla,- lai,c, = 0 (4) Iai and Ia2 are positive and negative sequence components of line currents. Iai and 1^ are positive and negative sequence components of compensators. The symmetrical components analysis gives the suseptances in terms of complex line currents as follows: Bab' c ' = - - Im la, + - - Re Ia2 - - - Im la! 2 1 Bbc1 c ' = - Im la, - - Im la, (5) Bca1 c ' = - - Im la, - - - Re Ia2 - - Im la, jI il jl XVThe results in (5) are the same as (3) but compensator suseptances are defined with respect to line currents and voltages. The transmission network compensation requires a different approach than load compensation. It may not be possible or practical to measure the quantities that would meaningfully characterize the load. The primary interest at the terminal of a transmission line is generally the voltage. The objectives of compensation may be stated as follows:. Eliminate the negative sequence voltage,. Stabilize the positive sequence voltage at the terminal. Mathematically this means that, Va2= 0, Vat=V=constant (6) The structure of the used static compensator is shown in figure 2. The basic components of the compensator are: A thyristor controlled inductance and fixed capacitor. Ix Xs I Q V(t) Bc İ2Û I Bio flload Figure 2. Static Reactive compensator Vn Vref.Q Other signals Voltage v Regulator Measuring Circuit <? Other Signals Line Voltage Thyristor Suseptance Control Interface Isvc Figure 3. Control Block Diagram XVIA fixed capacitor thyristor controlled reactor type controlled reactor type VAR compensator is shown in figure 2. The current in the reactor and total compensating current is varied by changing angle control. In the fifth chapter static VAR compensator control block diagram are presented (figure 3). Software control technique is used to control static VAR compensator. When th e firing delay of thyristors is changed from a to a+Aa the effective suseptance will be changed from B(a) to B(a)+AB(a). Figure 4 shows the modular organisation of the static TCR/FC compensator control system. v*. V voltage regulator (VR) AB gain ^ compensator (GO firing controller (FC) Software controller RMS evaluator (RE) ex. }1 TCR/FC comp. voltage transduc.^ Figure 4. Software control module The voltage trasducer samples the voltage, N times per cycle v(l),v(2)v(k),...v(N) so that the RMS values can be computed by the software module, V(1),V(2)V(k),...V(N) Assume that nominal and actual RMS values of a voltage are Vr(k) and V(k), then the error signal V(k)=Vr(k)- V(k) passes into the VR module. VR module is discrete PID control algorithm. AB(k) = (Kp+ K,T + Kd/T) AV(k)- (Kp+2Kd/T) AV(k-l)+(K/0 AV(k-2) (7) It computes AB(k) and Aa(k) is computed by (GC) module. FC module will add Aoc(k) to aj to find new firing angle otj+1. ocj is the value of firing angle in the last control interval. Thus aj+i=aj+Aa(l)++ Aa(k)++Aa(N) (8) xvuThis control algorithm can be examined on the single phase circuit where the load is only inductive and have only line reactance. The compensator is connected parallel to the load. XVU1

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