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They are, in general, cheaper, higher-capacity, faster and more reliable than dynamic compensation schemes such as synchronous condensers. However, static VAR compensators are more expensive than mechanically switched capacitors, so many system operators use a combination of the two technologies
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The main advantage of SVCs over simple mechanically switched compensation schemes is their near-instantaneous response to changes in the system voltage. For this reason they are often operated at close to their zero-point in order to maximize the reactive power correction they can rapidly provide
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steps the transmission voltage (for example, 230 kV) down to a much lower level (for example, 9.0 kV). This reduces the size and number of components needed in the SVC, although the conductors must be very large to handle the high currents associated with the lower voltage. In some static VAR
85:(lagging) conditions, the capacitor banks are automatically switched in, thus providing a higher system voltage. By connecting the thyristor-controlled reactor, which is continuously variable, along with a capacitor bank step, the net result is continuously variable leading or lagging power.
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device family, regulating voltage, power factor, harmonics and stabilizing the system. A static VAR compensator has no significant moving parts (other than internal switchgear). Prior to the invention of the SVC, power factor compensation was the preserve of large rotating machines such as
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control is provided by the capacitors; the thyristor-controlled reactor is to provide smooth control. Smoother control and more flexibility can be provided with thyristor-controlled capacitor switching.
237:, where there may be an existing medium-voltage busbar present (for example at 33 kV or 34.5 kV), the static VAR compensator may be directly connected in order to save the cost of the transformer.
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connected in series and inverse-parallel, forming "thyristor valves". The disc-shaped semiconductors, usually several inches in diameter, are usually located indoors in a "valve house".
260:(sometimes in the same installation), using the static VAR compensator to provide support for fast changes and the mechanically switched capacitors to provide steady-state VARs.
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Another common connection point for SVC is on the delta tertiary winding of Y-connected auto-transformers used to connect one transmission voltage to another voltage.
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By means of phase angle modulation switched by the thyristors, the reactor may be variably switched into the circuit and so provide a continuously variable
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are usually provided to smooth the waveform. Since the filters themselves are capacitive, they also export MVARs to the power system.
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More complex arrangements are practical where precise voltage regulation is required. Voltage regulation is provided by means of a
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Hingorani, N.G. & Gyugyi, L. Understanding FACTS - Concepts and
Technology of Flexible AC Transmission Systems. IEEE.
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117:, of which at least one bank is switched by thyristors. Elements which may be used to make an SVC typically include:
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is commonly used to cool them. Chopping reactive load into the circuit in this manner injects undesirable odd-order
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In transmission applications, the SVC is used to regulate the grid voltage. If the power system's reactive load is
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The thyristors are electronically controlled. Thyristors, like all semiconductors, generate heat and
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In industrial applications, SVCs are typically placed near high and rapidly varying loads, such as
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The SVC is an automated impedance matching device, designed to bring the system closer to unity
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Connected to the power system, to regulate the transmission voltage ("transmission SVC")
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injection (or absorption) to the electrical network. In this configuration, coarse
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Connected near large industrial loads, to improve power quality ("industrial SVC")
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Generally, static VAR compensation is not done at line voltage; a bank of
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Typically, an SVC comprises one or more banks of fixed or switched shunt
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Song, Y. H., Johns, A. T. Flexible AC transmission systems. IEE.
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and manual adjustment of the voltage set-point are also common.
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Thyristor-switched capacitor (TSC), shown with delta connection
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Thyristor-controlled reactor (TCR), shown with delta connection
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Mechanically switched capacitors or reactors (switched by a
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from the system, lowering the system voltage. Under
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243:The dynamic nature of the SVC lies in the use of
233:compensators for industrial applications such as
153:of a typical SVC configuration; here employing a
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427:Arrillaga, J.; Watson, N. R. (2003-11-21).
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299:Practical Power Distribution for Industry
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296:De Kock, Jan; Strauss, Cobus (2004).
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403:High Voltage Engineering and Testing
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527:Electric power systems components
44:flexible AC transmission system
42:networks. SVCs are part of the
467:. Springer. pp. 169–177.
270:static synchronous compensator
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496:"Static Var Generator Manual"
274:unified power flow controller
75:thyristor controlled reactors
51:or switched capacitor banks.
330:Deb, Anjan K. (2000-06-29).
268:Similar devices include the
159:thyristor-switched capacitor
155:thyristor-controlled reactor
128:Thyristor-switched capacitor
122:Thyristor-controlled reactor
73:(leading), the SVC will use
205:and so banks of high-power
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333:Power Line Ampacity System
406:. IEE. pp. 160–161.
92:, where they can smooth
40:electricity transmission
461:Padiyar, K. R. (1998).
433:. Wiley. p. 126.
430:Power System Harmonics
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49:synchronous condensers
25:static VAR compensator
21:Electrical Engineering
235:electric arc furnaces
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400:Ryan, H.M. (2001).
218:supervisory control
216:controller. Remote
306:. pp. 74–75.
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134:Harmonic filter(s)
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440:978-0-470-85129-6
413:978-0-85296-775-1
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214:closed-loop
100:Description
77:to consume
516:Categories
280:References
251:Advantages
245:thyristors
224:Connection
111:capacitors
71:capacitive
338:CRC Press
203:harmonics
105:Principle
83:inductive
304:Elsevier
276:(UPFC).
264:See also
115:reactors
207:filters
175:voltage
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79:VARs
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