* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download A Novel DFACTS Device for the Improvement of Power B.Y.Bagde
War of the currents wikipedia , lookup
Ground (electricity) wikipedia , lookup
Stepper motor wikipedia , lookup
Power over Ethernet wikipedia , lookup
Mercury-arc valve wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Power factor wikipedia , lookup
Electrical ballast wikipedia , lookup
Electric power system wikipedia , lookup
Electrification wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Power inverter wikipedia , lookup
Power MOSFET wikipedia , lookup
Opto-isolator wikipedia , lookup
Electrical substation wikipedia , lookup
Power engineering wikipedia , lookup
Amtrak's 25 Hz traction power system wikipedia , lookup
Current source wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Voltage regulator wikipedia , lookup
Surge protector wikipedia , lookup
Stray voltage wikipedia , lookup
Variable-frequency drive wikipedia , lookup
History of electric power transmission wikipedia , lookup
Power electronics wikipedia , lookup
Buck converter wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Alternating current wikipedia , lookup
Three-phase electric power wikipedia , lookup
A Novel DFACTS Device for the Improvement of Power Quality of the Supply P. M. Meshram1 B.Y.Bagde2 R.N.Nagpure3 1,2 & 3 Sr. Lecturers, Dept. of Electrical Engg., Yeshwantrao Chavan College of Engg., Nagpur, INDIA, 1. [email protected], 2. [email protected], 3. [email protected] ABSTRACT The proliferations of the non-linear devices cannot be restricted at transmission and distribution level because of their compactness and power handling capacity but they also draw non-linear current and hence degrade the power quality. The different non-linear loads at the distribution side are adjustable speed drives, fluorescent lighting and personal computers (PC’s), television sets, refrigerators etc. In this paper we propose the controller at the distribution side, i.e., between the utility and the customer for the improvement of the quality of supply and therefore it is called DFACTS device. The concept is analyzed and completely simulated for different types of loads i.e. linear balanced; linear unbalanced; non-linear balanced and non-linear unbalanced. Keywords: DFACTS, FACTS, power quality & Voltage source converters (VSC) concept of DFACTS device uses two Voltage Source Converters (VSC’s) utilizing Pulse Width Modulation (PWM) technique where inherent characteristics of reducing the lower order harmonics is used for the domestic, i.e., at the distribution side for improvement of quality of the power supply. The proposed concept has been simulated for different types of loads and balanced as well as unbalanced supply voltages. 2. PRINCIPLE OF OPERATION The two- level, six-pulse voltage source converter (VSC) is shown in Fig. 1. Let Es1 Fundamental component of the ac bus voltage. Ec1 Fundamental component of VSC s output voltage. δ Angle between Es1 and Ec2. X Converter reactance. P Active power Q Reactive power 1. INTRODUCTION For a given transmission line, three key parameters determine power flow: terminal bus voltages, line impedence, and the relative phase angle between the sending and receiving end. To modify these parameters, a variety of mechanically switched devices like shunt connected capacitors and phase sifting transformers are used but none responds quickly enough to changing conditions to provide real-time flow control. Each of these conventional power controllers has a conceptual equivalent based on power electronics. In addition, with advanced thyristor technology, novel controllers that have no single conventional analog have been developed and are termed as FACTS devices [1]. There are several FACTS controllers, namely, static var compensator (SVC), thyristor controlled phase angle regulator, thyristor controlled phase angle regulator (TCPAR), static compensator (STATCOM), unified power flow controller (UPFC), etc. [2-3]. The above FACTS devices are used for maintaining i.e. either supporting or the preventing from rising the voltage means supplying or absorbing the reactive power but not exclusively for the improvement of quality of the supply. This proposed DFACTS device is exclusively for the improvement of the quality of the supply. The new Idc Es1∠δ L,R Esa L,R Esb L,R Esc Ec1∠ 0 S1 S2 S3 I1 I2 Vdc C I3 S1' S'2 S'3 Fig. 1: Power Circuit of a Three Phase VSC. P= E s1 E c1 sin δ X Q= E s1 ( E c1 cos δ X (1) E s1 ) (2) From (1), the active power flowing over the VSC is primarily determined by δ . The flow of it is determined by the relative position between Es1 and Ec1. When Ec1 lags behind Es1, the VSC functions as a rectifier and absorbs real power from the left ac network. When Ec1 leads Es1, the VSC works as an inverter and gives real power to the left ac system. Similarly from (2) the reactive power is controlled by Ec1. Three basic control modes for the VSC are (a) Constant dc voltage control, (b) Constant dc current control, (c) Constant ac voltage control for the passive load, mode (c) is used and one side of the system should adopt constant dc control method. Ec2∠0 2C2 R2 Es2∠δ2 Qload L2 Edc 2C2 ZL Filte Fig. 3: Load Side of the Device. From Fig. 3, we have 3. SYSTEM DESCRIPTION The DFACTS device consists of two controllers, i.e., constant dc voltage controller and ac voltage controller. The constant dc voltage controller maintains constant dc voltage while ac voltage controller maintains the required rms value of the voltage at the load side. The two-voltage source converters are shown connected back-to-back in the Fig 2. Ps1 and Qs1 are the active and reactive power supplied; Pc1 and Qc1 are the active and reactive power absorbed by the VSC. Es1 and Es2 are the peak-to-peak voltage of the supply and load side. Ps1 Q s1 M2 ES 2 = ZL EC 2 Z2 + ZL Z1 E c 2 ∠ 0 E s2 ∠ δ 2 V SC E dc V SC Z2 IL I ZL 2 (0 ≤ Edc M 2 ≤ 1) (3) (4) From (3) and (4) we get ES 2 = Pc1 Q c1 E s1∠ δ1 E c1∠ 0 A ctiv e N etw o rk EC 2 = M2 ZL Edc ( 0 ≤ M 2 ≤ 1 ) 2 Z2 + ZL ZL ∂E S 2 1 Edc ; 0 = ∂M 2 2 Z2 + ZL (5) (6) where: E S 2 load voltage. E S 2 VSC output voltage at the load side. DC C o n tro ller at S tatio n 1 AC C o n tro ller at S tatio n 2 Fig.2: Back-to-Back VSCs M2 Modulation index at the load side. ZL load impedance. Edc dc voltage Z2 Impedance between VSC inverter and load. Eq (6) shows that there is a linear relationship between E S 2 and M 2 , so pure PI controller is adequate to meet the control equipment. 4. DCVOLTAGE CONTROLLER DESIGN The complete mathematical analysis and block diagram of the dc voltage controller is given [4]. The block diagram of the same is realized in MATLAB 6.5 E s2 ref ∆E 2 PI F req u en cy S ig n al G en eratin g F irin g P u lse F irin g P u lse 5. AC CONTROLLER DESIGN For ac voltage control station, assume the dc voltage utilization ratio of the adopted PWM method is 1 and the modulation index is M 2 0 ≤ M 2 ≤ 1 . C alcu latio n of F irin g P u lse E 2 L o ad S id e E 2b V o ltag es E 2 Fig.4: AC Controller 6. SIMULATION RESULTS Load Voltage Load Voltage Load Voltage Load Voltage Fig.5: For Linear Balanced and Unbalanced, NonLinear Balanced & Unbalanced Loads. Load Current Load Current Load Current Load Current Fig.8: For Linear Balanced and Unbalanced, NonLinear Balanced and Unbalanced Loads. Supply Voltage Supply Voltage Supply Voltage Supply Voltage Fig.6: For Linear Balanced and Unbalanced Loads Fig.9: For Non-Linear Balanced and Unbalanced Loads Supply Current Supply Current Supply Current Supply Current Fig.7: For Linear Balanced and Unbalanced Loads Fig.9: For Non-Linear Balanced and Unbalanced Loads The rated parameters of the system are as follows: Es1=11kV (peak to peak); R1=0.002ohm, L1=20 µ H, The DC voltage is 500V. The rated capacity of each VSC is 500kW and the switching frequency is 2 kHz. Increasing the modulation index with increasing DC voltage could vary the load voltage magnitude. The following different loads are considered. (1) Linear balanced load La =100 kW, 40 kVAR; Lb = 100 kW, 40 kVAR; Lc = 100 kW, 40 kVAR (2) Linear unbalanced load La = 50 kW, 30 kVAR; Lb = 100 kW, 30 kVAR; Lc = 50 kW, 50 kVAR; (3) Non-linear balanced load La = Lb = Lc = 500 kW. (4) Non-linear unbalanced load La = 167 kW; Lb = 167 kW; Lc = 100 kW. where La, Lb and Lc are the loads connected to a, b and c phases. Simulation results for the different loads as well as balanced as well as unbalanced supply voltages are shown in the Fig 5 and Fig 6. Following conclusions can be made from the Table 1 and Table 2: (a) Supply side voltage and current distortions are well within the limits though the loads are made deliberately distorted for the balanced supply voltages. (b) Though supply is made unbalanced and the loads are of different types, supply side voltage and current distortions are well within the limits. (c) The full load capacity is 500kW and it is fully applied in the case of non-linear balanced load. Table 1: Total Harmonic Distortion (THD) in the Load and Supply for Balanced Supply Voltages. % THD in ↓ Linear Balanced load Linear unbalanced load Nonlinear balanced load Non-linear unbalanced load Load voltage 1.87 3.44 9.26 32.53 Load current 1.86 2.97 24.24 55.19 Supply voltage 0.6 0.37 0.48 0.60 Supply current 0.61 2.72 0.49 0.38 Table 2: Total Harmonic Distortion (THD) in the Load and Supply for Unbalanced Supply Voltages. % THD in ↓ Linear Balanced load Linear unbalanced load Nonlinear balanced load Non-linear unbalanced load Load voltage 7.67 3.44 9.13 32.25 Load current 7.23 2.97 24.67 58.15 Supply voltage 0.6 0.37 0.54 0.49 Supply current 0.92 2.72 0.49 0.40 7. CONCLUSIONS The power quality at the supply side is maintained though loads are deliberately made distorted and follows the IEEE 519 1992 standards. Therefore this DFACTS device could be used at the distribution side i.e. between utility and the customer. This device could be called series-series controller. In the case 3 i.e. for non linear balanced load the full capacity of load was applied and it still shows the distortions on the supply side are well within the standards. Therefore whatever the impurities on the load side are not transferred on the supply side irrespective loads natures. The characteristics of the power quality improvement of the proposed DFACTS device is also hold good for the balanced as well as un-balanced supply voltages. And there is no rigmarole method of identifying the harmonics to reduce those and subsequently reducing the distortions i.e. for improvement of quality of the supply. 8. REFERENCES [1] Karl E. Stahkopf and Mark R. Wilhem “Tighter Controls for Busier Systems” IEEE Spectrum, April 1997 pp48-52. [2] L. Gyugui, “ Unified power flow for flexible AC transmission system” IEE Proceeding, PartC, Vol. 139, No. 4 July 1992,pp323-332. [3] N. G. Hingorani and and L.Gyugui, Understanding FACTS, IEEE press, New York,1999. [4] Blasko.V. and Agirman I, “Modellinng and Control of Three-Phase Regenerative AC-DC Converters” IEEE2001 pp2235-2240.