Unit 3 FACTS Technology
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The document covers various aspects of FACTS (Flexible AC Transmission Systems) technology, detailing the necessity, classification, and applications of controllers such as SVC, STATCOM, TCSC, and UPFC. It explains the role of reactive power sources and the importance of power electronic controllers in enhancing the flexibility and efficiency of AC transmission systems. The advantages and operational characteristics of each type of FACTS controller are also discussed, highlighting their contributions to improving voltage regulation and power transfer capacity.
Unit 3 FACTS Technology
- 1. DEPARTMENT OF ELECTRICAL ENGINEERING JSPMS BHIVARABAISAWANTINSTITUTEOFTECHNOLOGYANDRESEARCH, WAGHOLI,PUNE A.Y. 2020-21 (SEM-I) Class: B.E. Subject: Power System Operation Control Unit No-3 FACTS Technology Prepared by Prof. S. D. Gadekar Santoshgadekar.919@gmail.com Mob. No-9130827661
- 2. Content • FACTS-(Flexible AC Transmission System Controller) • Sources of Reactive Power (VARS) • Necessity of FACTS Controller • Classification of FACTS Controller • STATIC VAR Compensator (SVC) • Static Synchronous Compensator (STATCOM) • Thyristor Controlled Series Capacitor (TCSC) • Unified Power Flow Controller (UPFC)
- 3. FACTS-(Flexible AC Transmission System Controller) “It is defined as alternating current transmission systems incorporating power electronics based and other static controllers to enhance controllability and increase power transfer capability.” It is a system based on power electronic and other static equipment that provide control of one or more AC transmission system parameters.
- 4. Sources of Reactive Power (VARS) 1. Synchronous Machines (Alternator & Motor) 2. Shunt Static Capacitors 3. Series Capacitors 4. Synchronous Condensers 5. FACTS Controllers
- 5. Necessity of FACTS Controller ∞ |𝑽| < 𝟎°G 𝑬 < 𝜹 Bus 1 Bus 2 𝑷 𝒎 𝑺 𝒔 = 𝑷 𝒔 + 𝒋𝑸 𝒔 𝑺 𝒓 = 𝑷 𝒓 + 𝒋𝑸 𝒓 Generalised Power System 𝑽 𝑺 𝑽 𝑹
- 6. Necessity of FACTS Controller There has to maintained sufficient margins in power transfer due to, • The large interconnected transmission networks are susceptible to faults caused by lightning discharges and decrease in insulation clearances by undergrounds. • The loads in power system vary by the time of day, they are also subject to variations caused by the weather and other unpredictable factors. Thus the power flow in a transmission line can very even under normal steady state conditions.
- 7. Necessity of FACTS Controller There has to maintained sufficient margins in power transfer due to, • The occurrence of contingency (due to tripping of line, generator) can result in a sudden increase /decrease in the power flow. • The increase in the loading of the transmission lines sometimes can lead to voltage collapse due to the shortage of reactive power delivered at the load centres. These power transfer margins can not be maintained due to the difficulties in the expansion of the transmission network caused by economic and environmental reasons. The introduction of fast dynamic control over reactive and active power by high power electronic controllers makes AC transmission network ‘Flexible’ to adapt to the changing conditions.
- 8. Classification of FACTS Controller FACTS controller are classified on the basis of 1. Type of connection in the power system network a. Shunt Connected Controller b. Series Connected Controller c. Combined Series-Series d. Combined Shunt-Series 2. Power Electronic Devices used in the control a. Variable impedance type controller b. The VSC based FACTS controller
- 9. Classification of FACTS Controller 2. Power Electronic Devices used in the control a. Variable impedance type controller • Static VAR Compensator-SVC (Shunt) • Thyristor Controlled Series Capacitor-TCSC (Series) • Thyristor Controlled Phase Shifting Transformer- TCPST (Combined Shunt-Series) b. The VSC based FACTS controller • Static Synchronous Compensator-STATCOM (Shunt) • Static Synchronous Series Compensator-SSSC (Series) • Interline Power Flow Controller-IPFC (Combined Series-Series) • Unified Power Flow Controller-UPFC (Combined Shunt-Series)
- 10. Static VAR Compensator-SVC It is a variable impedance device where the current through a reactor is controlled using back to back connected thyristor valves. There are two types of SVC- 1. Thyristor Switched Capacitor-Thyristor Controlled Reactor (TSC- TCR) 2. Fixed Capacitor -Thyristor Controlled Reactor (FC-TCR) 𝐿 |𝑽| < 𝟎° G 𝑬 < 𝜹 Bus 1 Bus 2 𝑷 𝒎 𝑺 𝒔 = 𝑷 𝒔 + 𝒋𝑸 𝒔 𝑺 𝒓 = 𝑷 𝒓 + 𝒋𝑸 𝒓 𝑽 𝑺 𝑉𝑅 SVC 𝑽 𝑹 ∗ + − 𝑄 𝑟 = 𝑉𝑟 𝑋 |𝑉𝑠 − 𝑉𝑟|
- 11. Static VAR Compensator-SVC The SVC is used in two main situations 1. Connected to the power system, to regulate the transmission voltage. 2. Connected near large industrial loads, to improve power quality.
- 12. Circuit Diagram:-TCR-TSC Configuration SVC High Voltage Transmission Line or Grid Step Down Transformer Potential Transformer HP Filter Tuned Filter Control Unit 𝑽 𝑹𝒆𝒇 + 𝑉𝑅 − TCR- Thyristor Control Reactor TSC Thyristor Switched Capacitor Low Voltage Bus
- 13. Circuit Diagram:-FC-TCR Configuration SVC High Voltage Transmission Line or Grid Step Down Transformer Potential Transformer HP Filter Tuned Filter Control Unit 𝑽 𝑹 ∗ + 𝑉𝑅 − TCR- Thyristor Control Reactor Fixed Capacitor
- 14. V-I Characteristics of FC-TCR SVC V-I Characteristics of TSC-TCR SVC
- 15. Applications of SVC • The midpoint located ideal SVC doubles the steady state power limit and increases the stable angular difference between the synchronous and the infinite bus from 90°to 180°. The maximum steady state power across uncompensated line without SVC corresponds to 𝛿 = 90° is, 𝑃𝑒 = 𝑉1 𝑉2 𝑋 sin 𝛿 −− −1 𝑃𝑚𝑎𝑥 = 𝑉2 𝑋 −− −2 The electrical power flow across the half line section connecting the generator and SVC is, 𝑃𝑒 = 𝑉1 𝑉2 𝑋 2 sin 𝛿 2 −− −3 𝑃𝑚𝑎𝑥 = 2𝑉2 𝑋 −− −4
- 16. Applications of SVC • Enhancement of transient stability. Uncompensated Power System Network
- 17. Applications of SVC • Enhancement of transient stability. Compensated Power System Network
- 18. Applications of SVC • The major applications of SVC is for rapid voltage regulation and control of dynamic over voltages caused by load through off, faults or other transients disturbances. • Augmentation of power system damping.
- 19. Advantages of SVC • Faster Response under transient conditions • There are no moving parts, hence requires less maintenance • There is no problem of loss of synchronism • A SVC do not contribute to short circuit.
- 20. Static Synchronous Compensator-STATCOM It is a shunt connected static compensator, which uses a voltage source converter (VSC) based on self commutated power semiconductor devices such as GTO, IGBT, IGCT, MCT etc. 𝐿 |𝑽| < 𝟎° G 𝑬 < 𝜹 Bus 1 Bus 2 𝑷 𝒎 𝑺 𝒔 = 𝑷 𝒔 + 𝒋𝑸 𝒔 𝑺 𝒓 = 𝑷 𝒓 + 𝒋𝑸 𝒓 𝑽 𝑺 𝑉𝑅 VSC 𝑽 𝒓 𝑹𝒆𝒇𝒆𝒓𝒆𝒏𝒄𝒆 + − 𝑄 𝑟 = 𝑉𝑟 𝑋 |𝑉𝑠 − 𝑉𝑟| 𝑉𝐷𝐶 + − 𝐼 𝐷𝐶 DC Energy Source 𝐸𝑆 𝐼𝑠
- 21. VSC 𝑹𝒆𝒇𝒆𝒓𝒆𝒏𝒄𝒆 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 + − 𝑽 𝑫𝑪 + − 𝑰 𝑫𝑪 DC Energy Source 𝑬 𝑺 𝑰 𝒔 𝑬 𝒕 Utility Voltage Principle of Static Synchronous Compensator (STATCOM)- The exchange of reactive power between the converter and the ac system can be controlled by varying the amplitude of the three phase output voltage, 𝑬 𝑺 of the converter. VSC−𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝑺𝒐𝒖𝒓𝒄𝒆 𝑪𝒐𝒏𝒗𝒆𝒓𝒕𝒆𝒓 𝑰 𝒒 𝑬 𝒂𝒄 𝑬 𝑺 > 𝑬 𝒕 𝑬 𝑺 < 𝑬 𝒕 Supplies-Q Absorbs- Q
- 22. 𝐼𝐿𝑚𝑎𝑥 V-I Characteristic of STATCOM- 𝐼 𝐶 𝑉𝑡 𝐼 𝐶𝑚𝑎𝑥 𝐼𝐿 1.0 0.25 Capacitive Inductive
- 23. Applications of STATCOM- • STATCOM is used to fast regulation of voltage at a load or an intermediate bus. This will also increase the power transfer capacity of network. • The smaller size and faster response of a STATCOM provides an opportunity to import power from distant economic generators while the voltage is stabilized with a local STATCOM. • The use of multi pulse and or multilevel converters eliminates the need for harmonic filters in the case of a STATCOM.
- 24. Advantages of STATCOM- • Faster response • Requires less space as bulky passive components (such as reactors) are eliminated. • Inherently modular and relocatable • It can be interfaced with real power sources such as battery, fuel cells or SMPS. • A STATCOM has superior performance during low voltage condition as the reactive current can be maintained constant. In a SVC, the capacitive reactive current drops linearly with the voltage at the limit of capacitive susceptance.
- 25. Sr. No STATCOM SVC 1 It is a converter based VAR generator, functions as a shunt connected synchronous voltage source. It is a TCR-TSC based VAR generator, functions as a shunt connected, controlled reactive admittance. 2 The real and reactive power exchange between the STATCOM and the ac system can be controlled independently of each other. Also any combination of real and reactive power generation and absorption is achievable. The Real power compensation is not possible using SVC as interfacing suitable energy storage with ac system for real power exchange is not possible. 3 The STATCOM can be operated over its full output current range even at very low, typically about 0.2 PU system voltage levels. The maximum attainable corresponding current of the SVC decreases linearly with AC system voltage. 4 The transient stability margin obtained with the STATCOM, due to the better support of the midpoint voltage is significantly greater. The transient stability margin is less for the same rating SVC. 5 Small in size. Large in size as it requires the capacitor and reactor banks with their associated switchgear and protection. Comparison between SVC & STATCOM
- 26. Sr. No STATCOM SVC 6 The maximum VAR generation or absorption changes linearly with the ac system voltage The maximum VAR output decreases with the square of the voltage 7 Attainable response time and bandwidth of the closed voltage regulation loop of the STATCOM are also significantly better than those of the SVC. Less for svc system 8 The loss contribution of power semiconductors and related components to the total compensator losses is higher for STATCOM. Lesser for SVC Comparison between SVC & STATCOM
- 27. Thyristor Controlled Series Capacitor-TCSC In this configuration a TCR is used in parallel with a fixed capacitor. It enables a continuous control over the series compensation. TCSC provides inherent protection against over voltages. TCSC is available for application in AC lines of voltage up to 500 kV. Bus 1 Bus 2 𝑽 𝑺 𝑽 𝑹 𝑄 𝑟 = 𝑉𝑟 𝑋 |𝑉𝑠 − 𝑉𝑟| TCSC 𝑃𝑒 = 𝑉𝑆 𝑉𝑅 𝑋 sin 𝛿 T1 T2
- 28. The Reactance of TCSC and current through TCR is Given by, The Reactance of TCSC (ZTCSC) is given by, XTCSC = −jXc ∗ jXTCR j(XTCR − XC) XTCSC = −jXc (1 − Xc XTCR ) The current through the TCR (ITCR) is given by, ITCR = −jXc j(XTCR − XC) IL ITCR = IL j(1 − XTCR XC )
- 29. Compute XTCSC XC and ITCR IL if, a. XTCR = 1.5XC −−−−− −XTCR > XC 𝐗 𝐓𝐂𝐒𝐂 𝐗 𝐂 = 𝟏 𝟏− 𝐗 𝐜 𝐗 𝐓𝐂𝐑 = 1 1− 1 1.5 XTCSC XC = 3.0 𝐈 𝐓𝐂𝐑 𝐈 𝐋 = 𝟏 𝟏− 𝐗 𝐓𝐂𝐑 𝐗 𝐂 = 1 1−1.5 ITCR IL = −2.0
- 30. Compute XTCSC XC and ITCR IL if, b. XTCR = 0.75XC −−−−− −XTCR < XC 𝐗 𝐓𝐂𝐒𝐂 𝐗 𝐂 = 𝟏 𝟏− 𝐗 𝐜 𝐗 𝐓𝐂𝐑 = 1 1− 1 0.75 XTCSC XC = 3.0 𝐈 𝐓𝐂𝐑 𝐈 𝐋 = 𝟏 𝟏− 𝐗 𝐓𝐂𝐑 𝐗 𝐂 = 1 1−0.75 ITCR IL = 4.0
- 31. Case-1 XTCR = 1.5XC −−−−− −XTCR > XC −−−−− −𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒊𝒗𝒆 𝑶𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏 XTCSC XC = 3.0 ITCR IL = −2.0 Case-2 XTCR = 0.75XC −−−−− −XTCR < XC −−−−−− −𝑰𝒏𝒅𝒖𝒄𝒕𝒊𝒗𝒆 𝑶𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏 XTCSC XC = −3.0 ITCR IL = 4.0
- 32. 𝑽 𝑺 𝑽 𝑹 𝑿 𝑻𝑪𝑹 𝑰 𝑳 𝑰 𝑻𝑪𝑹 𝑿 𝒄 𝐗 𝐜<𝐗 𝐓𝐂𝐑 − −𝐂𝐚𝐩𝐚𝐜𝐢𝐭𝐢𝐯𝐞 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧 𝐗 𝐜 > 𝐗 𝐓𝐂𝐑 − −𝐈𝐧𝐝𝐮𝐜𝐭𝐢𝐯𝐞 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧
- 33. Modes of Operation of TCSC Bypass Mode- In this mode the thyristor valves are gated for 180 ° conduction in each direction. The flow current in the reactor is continuous and sinusoidal. The net reactance of the module is slightly inductive and TCSC is operating in TSR- (Thyristor Switched Reactor) mode. Bus 1 Bus 2 𝑽 𝑺 𝑽 𝑹 TCSC 180° 180° T1 T2
- 34. Modes of Operation of TCSC Inserted with thyristor valve blocked mode- In this mode no current flows through the valves with the blocking of gate pulses. Here TCSC reactance is same as that of fixed capacitor. Bus 1 Bus 2 𝑽 𝑺 𝑽 𝑹 T1 T2 TCSC Both Thyristor in Blocking Mode
- 35. Modes of Operation of TCSC Inserted with vernier control mode- The Thyristor valves are gated in the region of 𝛼 𝑚𝑖𝑛 < 𝛼 < 90° such that the valves conduct for the part of a cycle. The effective capacitive reactance increases as the 𝛼 increases from 0°. And effective inductive reactance increases as 𝛼 reduces from 180°. Bus 1 Bus 2 𝑽 𝑺 𝑽 𝑹 T1 T2 TCSC Thyristor Valves Conduct for Part of the Period
- 36. Unified Power Flow Controller-UPFC Intermediate Transformer Shunt Transformer VSC-1 Intermediate Transformer Series Transformer VSC-2 Circuit Breaker SW-1 SW-2 High Voltage Transmission Line
- 37. Unified Power Flow Controller-UPFC UPFC consists of two voltage sources converters (VSC), one shunt connected and series connected. If the switches 1 and 2 are open, the two converters work as STATCOM and SSSC controlling the reactive current and voltage injected in shunt and series respectively in the line. The closing of switch 1 and 2 enable the two converters to exchange real power flow between the two converter. The provision of a controllable power source on the DC side of the series connected converter, results in the control of both real and reactive power flow in the line.