Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
  • G05F1/10—Regulating voltage or current
  • G05F1/12—Regulating voltage or current wherein the variable actually regulated by the final control device is ac
  • G05F1/32—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using magnetic devices having a controllable degree of saturation as final control devices
  • G05F1/34—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using magnetic devices having a controllable degree of saturation as final control devices combined with discharge tubes or semiconductor devices
  • G05F1/38—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using magnetic devices having a controllable degree of saturation as final control devices combined with discharge tubes or semiconductor devices semiconductor devices only

Definitions

• the present invention relates generally to voltage stabilization. More particularly, the invention relates to methods and systems that employ a variable inductance to compensate for voltage variations that may arise in power supply lines. BACKGROUND OF THE INVENTION
• Undersized lines for electric power transmission also referred to as "weak lines" have too small a conductor cross section in relation to the load requirements and a relatively high resistance. Excessive voltage drop will result from the losses caused by undersized conductors. The excessive voltage drop results in inadequate voltage levels for the electric power connected to the lines.
• a transformer is a static unit which supplies a fixed voltage determined by the number of windings on the primary and secondary sides, i.e., the transformer ratio.
• a fixed transformer ratio may result in a voltage that is too low, (i.e., an undervoltage) when the load is high, and a voltage that is too high, (i.e., an overvoltage condition) when the load is low. Because the load is dependent at all times on the highly variable requirements of individual electric power consumers, fixed ratio transformers are often inadequate to serve a dynamic load.
• the low voltage level can be compensated for by increasing the voltage in steps at the transformer that is supplying the line.
• the voltage level is controlled by means of a load tap changer on the transformer which is connected to the individual phase at the location where the voltage reaches an unacceptably low level.
• the problem of weak lines is often solved by replacing existing lines with new lines having a larger cross section and correspondingly lower resistive losses.
• several methods are employed for upgrading the line. If there is room on the existing pole, a new line can be installed on the other side of the pole in parallel with the weak line. Once the new line is installed, the old one is disconnected and removed from service. This approach allows the power transmission system to be upgraded without a noticeable interruption in service.
• Another method involves installing hardware for securing new lines to the existing poles, disconnecting the weak lines, and quickly installing the new lines. This approach results in a longer interruption in service when compared with the preceding approach.
• a new route is constructed. Such construction involves the installation of new poles and new conductors. Significantly, before construction begins, the new route may have to be approved by local government and property owners.
• a mechanically controlled variac i.e., a transformer with variable transformer ratio
• a transformer with variable transformer ratio is used in connection with a transformer.
• mechanically controlled variacs generally, are no longer used because the mechanical components required frequent service.
• Another method that is currently employed consists of relocating the electric lines closer to users and connecting a new transformer to the relocated line where it will be closer to users. This approach is also undesirable because of the large scope of work required to relocate electric lines and the high cost associated with such a project.
• Wlass U.S. Patent No. 3,409,822 to Wanlass
• a voltage regulator that includes a device with an AC or load winding and a DC or control winding wound on a ferromagnetic core.
• a DC generated flux component and an AC generated flux component are provided along the same path but with an opposite direction at all times.
• the flux components are subtracted and the core has a permeability that, to a limited extent, corresponds to the resulting flux.
• the fluxes are orthogonal to one another.
• Wanlass shows a regulator based on flux control in the core's legs via addition or subtraction of magnetic fluxes lying in the same path (coincident fluxes with opposite signs).
• the power handling capability of the device is limited because the regulator described in Wanlass is meant for operation in the non-saturated area of the core, and the permeability range is limited to the linear region of the core.
• the present invention addresses the problems related to prior solutions of the problem created by weak lines.
• the permeability control is performed using orthogonal fields and it is not performed by means of parallel fields which are added or subtracted.
• the invention is a system for voltage stabilization of power lines including an autotransformer having a series winding and a parallel winding, a variable inductance connected to the autotransformer, and a control system.
• the variable inductance includes a magnetic core, a main winding wound around a first axis, and a control winding wound around a second axis orthogonal to the first axis.
• orthogonal fluxes are generated in the magnetic core.
• This voltage stabilization system automatically compensates for voltage variations in the power supply line to which it is connected.
• the orthogonal fluxes are generated in substantially all of the magnetic core.
• the magnetic core is made from anisotropic magnetic material.
• the control system includes a processor unit which controls a control current supplied to the control winding, a setpoint adjustment unit in electrical communication with the processor unit, and a switch.
• the switch connects and disconnects the regulation and is in electrical communication with the processor unit.
• the system also includes a feedback input which senses an output voltage. The feedback input is in electrical communication with the processor unit and the power supply line.
• the control system also includes a rectifier circuit in electrical communication with both the processor unit and the control winding.
• the series winding of the autotransformer is connected in series with a first power supply line and the parallel winding is connected in series with both the main winding and a second power supply line.
• the series winding and the main winding are connected in series with a first power supply line, the main winding is located on a line side of the series winding, and the parallel winding is directly connected to a second power supply line.
• the series winding and the main winding are connected in series with a first power supply line, the main winding is located on the load side of the series winding, and the parallel winding is directly connected to a second power supply line.
• the invention includes a method of stabilizing a voltage.
• An input voltage is supplied to an autotransformer and a controllable inductance is com ected in series with at least one winding of the autotransformer.
• An output voltage is sensed.
• Orthogonal magnetic fields are generated in a magnetic core of the controllable inductance. At least one of the orthogonal magnetic fields is adjusted to control permeability of the magnetic core in order to adjust the voltage in response to the output voltage sensed.
• there is practically no transformer action between the main winding and the control winding because the two fields are orthogonal in all parts of the core.
• the operation of the device can be extended into the saturable region of the core.
• This extended operation increases the power handling capacity of the variable inductance by one order of magnitude, because the power handling capacity is proportional to the inverse of the permeability of the material (when the permeability is halved, the power handling is doubled).
• the invention can be used in high power applications.
• a dynamic voltage booster or voltage stabilization system employing orthogonal flux control to increase a line voltage as required to avoid an undervoltage condition and to adjust the line voltage to maintain the voltage at a desired value is a very efficient alternative for improving weak lines.
• Such a unit can be connected to a weak line and dynamically compensate for a load-dependent voltage drop.
• the system according to the invention includes an electronically controlled orthogonal flux inductance. Together with a transformer, this inductance provides a variable output voltage which compensates for undesirable drops in voltage.
• a voltage stabilization system for power supply lines includes a control system for controlling the current in the control winding as a function of the desired and actual operating parameters of the line.
• the operating parameter is the line voltage.
• the regulating system supplies power to the control winding in the variable inductance based on line measurements and desired values of the line voltage (e.g., setpoints), with the result that the output voltage maintains the desired value.
• Embodiments of the invention permit existing weak lines to be adapted to maintain adequate voltage in a simple and inexpensive manner when there is an increase in energy use.
• adequate voltage is maintained by connecting the voltage stabilization system in the line between the distribution transformer and the users.
• the autotransformer adds a voltage in series with the supply voltage, thus enabling the line voltage to be stabilized.
• the variable inductance regulates the voltage across the inductance (by altering the permeability of the inductance core by means of orthogonal fields), or the time voltage integral across it, in order to regulate the voltage across the series winding in the autotransformer.
• Figure 1 illustrates an autotransformer.
• Figure 2 illustrates a first embodiment of the invention.
• Figure 3 illustrates a second embodiment of the invention.
• Figure 4 illustrates a third embodiment of the invention.
• Figure 5 illustrates a general block diagram of an embodiment according to the invention.
• Figure 6 illustrates the embodiment of Figure 2 in greater detail.
• Figure 7 illustrates a control system for controlling the embodiments shown in
• Figure 8 illustrates the embodiment of Figure 4 in greater detail.
• Figure 9 illustrates the embodiment of Figure 3 in greater detail.
• Figure 10 illustrates a control system for control of the embodiment in Figure 9.
• Figure 11 illustrates a three-phase embodiment of the invention.
• Figure 12 illustrates a control system for control of the embodiment of Figure 1.
• Figure 13 illustrates a second three-phase embodiment of the invention.
• Figure 14 illustrates a control system for control of the embodiment of Figure 13.
• Figure 15 illustrates a third three-phase embodiment of the invention.
• FIGS 16-18 illustrate control systems for controlling the embodiment of Figure 15.
• Figures 19 and 20 illustrate a controllable inductance according to an embodiment of the mvention.
• An autotransformer is a transformer with a series winding S and a parallel winding P.
• Figure 1 illustrates an autotransformer TI where the parallel winding P and the series windings S are connected in series.
• the series winding S has a relatively small number of turns, while the parallel winding P has a relatively large number of turns.
• the series winding has approximately 20 turns and the parallel winding has approximately 230 turns.
• An applied voltage VI is divided in proportion to the number of turns in the series winding in S and in the parallel winding P.
• the series winding S is connected in series with a first power supply line (e.g., a first phase) from the line input LI to the line output LU.
• the parallel winding is connected to a second power supply line (e.g., a second phase) L via an orthogonal field variable inductance LR.
• the voltage in the series winding S can be changed here by changing the voltage in the parallel winding P by means of the variable inductance LR.
• variable inductance LR and the series winding S are connected in series with the first power supply line from LI to LU, with the variable inductance connected to the line side LI of the series winding S.
• the parallel winding P is connected to the second power supply line.
• variable inductance LR and the series winding S are connected in series with the power supply line from LI to LU, with the variable inductance com ected to the load side LU of the series winding S.
• the parallel winding is coimected directly to the second power supply line L.
• the second phase is a neutral conductor.
• the voltage in the first power supply line LI - LU will be changed because the variable inductance LR absorbs a time voltage integral that remains in series with the voltage from the series winding S of the autotransformer.
• the voltage absorbed by the variable inductance is a reactive voltage
• the voltage leads the current by 90°.
• the voltage to be subtracted or added to the load voltage is 90° out of phase with a resistive current drawn by the load.
• the autotransformer there is an ampere-turn balance between the series winding S and the parallel winding P.
• the current drawn by the load is therefore reflected in the parallel winding P and causes a voltage drop in the variable inductor.
• the magnitude of the voltage drop depends on the value of the variable inductance and the amount of current.
• a fixed inductor is mounted in parallel with the parallel winding of the autotransformer. This reduces the harmonics generated by the system and stabilizes control of the system.
• a variable inductance may be used.
• FIG. 5 is a block diagram illustrating both the voltage stabilizer and the associated control system (e.g., regulating system).
• the first power supply line LI passes through the voltage stabilizer which is controlled by the control system.
• Kl, K2 and K3 are switches which allow the voltage stabilizer to be connected to, or disconnected from the network.
• Kl is illustrated in a closed state and K2 and K3 are shown as open, corresponding to the situation where the voltage stabilizer is not in use. When the voltage stabilizer is in use, Kl and K2 are opened and K3 is closed.
• FIGS 6 and 7 illustrate a single-phase voltage stabilizer in more detail.
• TI is the autotransformer with the series winding S located between terminals 1-2 and 3, and the parallel winding P located between terminals 1-2 and 4. This corresponds to the first embodiment of the invention illustrated schematically in Figure 2.
• T4 is the orthogonal field variable inductance LR with a working winding or main winding H located between terminals 1 and 2, and control winding ST located between terminals 3 and 4.
• the controllable inductance LR is connected to the parallel winding P of transformer TI with terminal 2 of T4 connected to terminal 4 of TI.
• Terminals 1L1 and 1L2 supply voltage to a rectifier circuit U9 shown in Figure 7.
• Figure 7 shows a control system for regulating current in the variable inductance T4.
• the control system includes a setpoint adjustment unit, a switch S3 for connecting or disconnecting the regulation, a feedback circuit for sensing the output voltage of the autotransformer TI, a processor unit U8, and a rectifier circuit U9 for connection to the control winding of the inductance.
• the setpoint adjustment unit is a potentiometer R8 and the feedback circuit includes a transformer T7.
• the processor unit U8 includes a microprocessor.
• the system also includes an overvoltage protection circuit U10.
• the setpoint adjustment unit of Figure 7 includes a first terminal, a second terminal, and a third terminal connected to terminals 7, 1 1 and 10 respectively of the processor unit U8.
• the switch S3 includes a first terminal and a second terminal connected to terminals 4 and 6 respectively of the processor unit U8.
• the primary terminals 1, 2 of transformer T7 are connected to SI and RI to sense the output voltage appearing at LU.
• a primary winding of transformer T7 is protected by fuses.
• a first terminal and a second terminal of a secondary winding of transformer T7 are connected to terminals 5 and 9 respectively of the processor unit U8.
• terminals ILl and 1L2 which correspond to RI and SI, are connected to line inputs of the processor unit U8.
• an isolation transformer is used to reduce the voltage that appears at ILl and 1L2 before it is applied to the processor unit U8.
• the overvoltage protection unit U10 includes a first terminal, a second terminal, and a third terminal connected to ILl, a rectifier positive output terminal, and 1L2 respectively.
• the overvoltage protection circuit includes a first potentiometer RI connected between the first terminal and the second terminal, and a second potentiometer R2 comiected between the second terminal and the third terminal.
• the over voltage protection circuit also includes fixed resistors R3 and R4.
• terminals ILl and 1L2 of Figure 6 are also connected to a first terminal and a second terminal of the rectifier circuit U9.
• the rectifier circuit U9 output includes a positive terminal and a negative terminal that are connected to the control winding ST at terminals 3T4 and 4T4 respectively.
• a resistor network including one or more resistors (e.g., R5, R6 and R7) is connected in series between the negative terminal and the control winding ST.
• the rectifier circuit U9 is a full wave bridge circuit including four diodes VI, V2, V3 and V4.
• diodes VI and V2 are controlled rectifier diodes, e.g., thyristors.
• the rectifier circuit U9 is connected to processor unit U8 via control terminals for diode VI and control terminals for diode V2.
• diode V5 is connected between the positive terminal and the negative terminal of the rectifier circuit U9.
• the control system of Figure 7 automatically adjusts the voltage drop across the main winding H of the controllable inductor T4 by adjusting the power supplied to the control winding ST in response to changes to the output voltage of the autotransformer TI.
• a setpoint representative of the desired output voltage is established via the setpoint adjustment unit R8.
• a feedback circuit provides the processor unit U8 with an indication of the autotransformer TI output voltage.
• the processor unit U8 compares the setpoint to the feedback voltage and adjusts the power supplied at the rectifier output terminals by controlling the operation of the rectifier circuit U9.
• the output of the rectifier circuit U9 is a DC current.
• This first embodiment of the invention shown in Figure 6, where inductance LR is series connected with the parallel winding P on the autotransformer TI, is implemented by a voltage across the parallel winding P in TI.
• This voltage is regulated by the inductance T4 which is connected in series by means of a transformer with the line voltage LI - LU between input terminal XI and output terminal XI :7.
• the voltage supplied to the load from R and S on XI :7 and XI : 10 can be increased. If the difference between the feedback signal and the setpoint is large, the regulator will increase the control current to the inductance T4, thereby increasing the additional voltage which compensates for the voltage drop.
• FIG 8 illustrates in more detail the third embodiment of the invention originally described broadly with reference to Figure 4.
• TI is an autotransformer with series winding S, located between terminals 1-2 and 3, and parallel winding P located between terminals 1-2 and 4.
• the control system related to this circuit is illustrated in Figure 7.
• T4 is the orthogonal field variable inductance with main winding H located between terminals 1 and 2, and control winding ST between terminals 3 and 4.
• Terminal 1 of inductance T4 is coupled to the output terminal of the series winding S at terminal T3.
• the control current is fed from the positive and negative terminals of a controlled rectifier circuit U9 in Figure 7 to terminals 3 and 4 on the control winding ST of Figure 8.
• the feedback of the output voltage from terminals R and S of the voltage stabilizer of Figure 8 is connected to transformer T7 terminals 2 and 1 of Figure 7. This connection provides a feedback signal to the rectifier regulator U8 of Figure 7
• setpoint adjustments may be made via potentiometer R8.
• the voltage input to the rectifier U9 of Figure 8 is supplied from terminal XI :2 and XI :4 of Figure 7.
• stabilization is implemented by regulating the stepped-up output voltage from TI (outgoing line voltage) via a controllable inductive voltage drop across the inductance T4 which lies in series in the line.
• FIG. 9 illustrates in more detail a second embodiment of the invention.
• TI is the autotransformer with series winding S located between terminals 1-2 and 3.
• the parallel winding P is located between terminals 1-2 and 4. This embodiment corresponds to the embodiment illustrated schematically in Figure 3.
• the associated control system is shown in Figure 10.
• T4 is the variable inductance with main winding H located between terminals 1 and
• Terminal T4:2 of the controllable inductance is connected to the series winding S at terminal Tl : l-2.
• the parallel winding P is also connected to the terminal Tl :2.
• Figure 10 shows how the control current is fed from the positive and negative terminals of a controlled rectifier circuit U9 to terminals 3 and 4 on the control winding ST of Figure 9.
• the feedback of the output voltage from terminal R and S of the voltage stabilizer is connected to transformer T7 terminals 2 and 1. This connection provides a feedback signal to the rectifier regulator U8.
• setpoint adjustments may be made via potentiometer R8.
• the voltage input to the rectifier U9 is supplied from terminal XI :2 and XI : :4 of Figure 9.
• This voltage regulator connection includes the inductance LR connected on the line side of and in series with the series winding S.
• stabilization is implemented via regulation of the auto transformer input voltage via adjustment of the voltage drop across the inductance T4 which lies in series in the line.
• the regulator will increase the control current to the inductance T4, to decrease the voltage drop across the inductance and compensate for the voltage drop. Conversely, if an overvoltage condition exists, the power supplied to the control winding is decreased in order to increase the voltage drop across the inductance and maintain the output voltage supplied to the load approximately equal to the setpoint voltage.
• a three-phase embodiment for the single-phase solutions described thus far may be based on the same technical method of voltage regulation based on a comparison between the output voltage and a reference (e.g., a setpoint).
• a reference e.g., a setpoint
• FIGs 11 and 12 illustrate a three-phase embodiment of the single-phase solution according to the second embodiment of the invention that is illustrated in Figure 3.
• the control windings ST of inductances T4, T5 and T6 are shown connected in series and thereby are regulated equally via the control circuit of Figure 12.
• Figure 12 shows a regulation system corresponding to those described earlier.
• the regulation system includes a setpoint adjustment resistor R8, a switch S3 for connecting and disconnecting the regulator, a transformer T7 for feedback voltage from phase RS, a processor unit U8 (e.g., reactor regulator), a diode rectifier U9 and an overvoltage protection circuit U10. From the output of the regulation system (points 3T4 and 4T4), a current signal is sent to variable reactance T4. Separate regulation for each phase is also possible in a version of this embodiment.
• the phase sequence is important since the voltages in the series windings S are added vectorially to the phase voltage from the feed transformers to the line (not shown).
• the series winding is placed between points 1 and 3 while the parallel winding is placed between points 2 and 4.
• the autotransformers for each phase TI, T2 and T3 are also shown in Figure 15.
• the variable inductance T4 regulates the voltage to TI in response to the feedback signal supplied from phase R-S (XI :7 and XI : 10).
• Variable inductance T5 regulates the voltage to T2 in response to the feedback signal supplied from phase S-T (XI : 12 and XI : 14).
• Variable inductance T6 regulates the voltage to T3 in response to the feedback signal supplied from phase T-R (XI : 14 and XI : 10). In this manner, the line voltages for each phase can be regulated independently of one another.
• Figure 16 illustrates regulation of the voltage in TI by means of T4 in response to the desired voltage represented by the set point established by setpoint adjustment R8. The output signal (see bottom right in Figure 16) is applied to the points 3 and 4 on T4.
• a corresponding regulation of T2 by means of T5 in response to setpoint adjustment RIO is illustrated in Figure 17. Regulation of the voltage in T3 by means of T6 is illustrated in Figure 18.
• the three-phase system as described above shows a delta connection of the parallel winding.
• the parallel windings are connected in a star (i.e., a wye) configuration which is well known connection topology for three-phase systems.
• Figure 19 shows an embodiment of the controllable inductor T4.
• the controllable inductor T4 includes a first pipe element 101, a main winding H wound around the first pipe element 101.
• the controllable inductor also includes magnetic end couplers 105, 106 in one embodiment.
• the controllable inductor T4 is manufactured from anisotropic material.
• the anisotropic material is grain oriented anisotropic material. Where grain oriented material is used a grain oriented direction (GO) and a transverse direction (TD) can be defined.
• the controllable inductor T4 also includes a second pipe element 102.
• a control winding ST is wound around the second pipe element and a second axis that is orthogonal to a first axis around which the main winding H is wound.
• the second pipe element 102 is located concentrically within the first pipe element 101.
• End couplers 105 and 106 each connect an end of the first pipe element 101 to a corresponding end of the second pipe element 102.
• a magnetic core is formed by the first pipe element 101, the second pipe element 102, and end couplers 105, 106.
• the first axis M is an annular axis relative to the second axis L.
• second axis L is a linear axis located at the center of the second pipe member 102.
• the controllable inductor T4 of Figures 19 and 20 develops two orthogonal fluxes.
• a first magnetic field H f and a first magnetic flux B f are generated when the main winding H is energized.
• a second magnetic field H s and a second magnetic flux Bs are generated when the control winding ST is energized.
• the magnetic fields H f , H s are orthogonal to one another in substantially all of the magnetic core
• the magnetic fluxes B f , B s are orthogonal to one another in substantially all of the magnetic core.

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Cited By (13)

Citations (4)

• 2003
  • 2003-12-12 BR BR0316600-7A patent/BR0316600A/pt not_active Application Discontinuation
  • 2003-12-12 AT AT03781106T patent/ATE423342T1/de not_active IP Right Cessation
  • 2003-12-12 KR KR1020057010740A patent/KR101059739B1/ko not_active IP Right Cessation
  • 2003-12-12 DE DE60326274T patent/DE60326274D1/de not_active Expired - Fee Related
  • 2003-12-12 AU AU2003288800A patent/AU2003288800A1/en not_active Abandoned
  • 2003-12-12 JP JP2004558573A patent/JP2006510088A/ja active Pending
  • 2003-12-12 CA CA2509490A patent/CA2509490C/en not_active Expired - Fee Related
  • 2003-12-12 WO PCT/NO2003/000417 patent/WO2004053615A1/en active Application Filing
  • 2003-12-12 EP EP03781106A patent/EP1576437B1/de not_active Expired - Lifetime

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