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    1481736 Automatic regulation of reactive current and voltage GENERAL ELECTRIC CO 8 Oct 1974 [12 Oct 1973] 43588/74 Headings G3R and G3X Reactive current compensating apparatus includes a fixed capacitor connected in parallel with a series combination of a fixed inductor and a gated A.C. switch. The firing angle of the switch is controlled to regulate the phase angle between the current and voltage of the supply. As shown, an electric arc furnace 20 is supplied from a generator 10 over a step-down transformer 14. Fixed capacitors 30-32 and timing inductors 33-35 are connected across the supply leads in parallel with inductors 40-42 and series controlled rectifiers 40b-42b. A firing angle control circuit 65 receives a control signal from a circuit 66 which adds together signals derived from a load current sensing circuit 61 representing reactive current, and a line current phase angle sensor 70. In both cases, a measured current value is combined with a voltage signal which is processed by transformer circuits (51, 60) Fig. 3 (not shown), so as to correct for the reactive effects of transformer 14. A feedback limiting circuit (90), Fig. 5 (not shown), is included, and the overall arrangement operates to maintain the phase angle close to zero. That part of the system including angle sensor 70 operates in a feed-forward manner, and compensates the furnace supply so that demand variations do not cause voltage disturbances on additional supply lines 25-27 connected to the generator 10. In addition to arc furnaces, the arrangement is suitable for supplying drag lines, rolling mill drives and high voltage transmission lines.
    公开号:SU776582A3
    申请号:SU742065898
    申请日:1974-10-11
    公开日:1980-10-30
    发明作者:Вильям Келли Фред (Младший)；Роберт Юджин Лезан Джордж
    申请人:Дженерал Электрик Компани (Фирма)；
    IPC主号:
    专利说明:

    one
    This invention relates to the control of reactive power in power systems.
    It is known that power systems that power highly reactive loads are characterized by poor voltage stability, i.e. a significant change in the magnitude of the voltage as the load current changes. In an inductive circuit, as the load current increases, the voltage drops as well as. Power factor. In order to improve voltage regulation, power transformers are usually equipped with junction transformers to eliminate the tendency of the voltage to vary as the load current changes. Most of the system loads are inductive in nature and compensating capacitances are connected in series or parallel to the wires of the power supply line for neutralizing the inductive current-connecting load of the system. Where it is possible to predict the load with a sufficient degree of accuracy, it is possible to use fixed capacitors.
    With some variables and disordered large loads, such
    like arc furnaces, adjustable shuntyrukvd capacitance is provided by connecting directly to the load terminals, parallel to the latter, synchronously rotating or static capacitors. When the load current changes, the capacitance value must change; with a constant capacitance, the increasing voltage at the load terminals above the applied system voltage should not affect the load. However, to prevent the lamp from flickering in the line due to large changes in the voltage induced on the load, the damping time of the rotating device is chosen to be quite large. Similarly, to avoid flicker, the mechanical switching means used to control the shunt static capacitors do not react very quickly. Energy switches are made capable; to respond within at least a half-period of the frequency of electricity, but their use directly in circuits with compensating capacitors shuntyrunvdimi unsatisfactory; leading capacitive current carries residual electrons in capacitors and, as a result, voltage transients or frequency harmonics appear to cause difficulties. Some measures have been proposed for changing the effect of the total reactive current of constant shunt compensating capacitors by connecting the inductor of the inductance coils in parallel and changing the value of the reactive component of the current passing through the compensating inductors. This can be done by changing the magnitude of the shunt inductance — in each line, fl, or by changing the magnitude of the reactive component of the current passing through: the shunt coil in., With a constant value of 12. The AC power supply system is also known, which contains a power source, supply wires and a reactive current compensation node consisting of chains connected to a star and including consecutively connected capacitors and inductors, terminals of the motors connected to load terminals, from chains formed from series-connected controlled valves and inductors, connected in delta, the leads of which are also connected to the load terminals, the unit for controlling the valves, and tchik .rezhimnogo parameter W}. This device does not provide sufficient voltage stability in the supply mains ... The purpose of the invention is to improve the accuracy of voltage maintenance in the supply network. The target was achieved by the fact that in the power supply system of an alternating current load, which contains a Litani source, power supply wires and a reactive current compensation unit, consisting of j strings connected in a star and including a capacitor with inline capacitors and inductors, whose outputs are connected to load clamps, from chains formed from series-connected controlled gates and inductance coils, connected in delta, the output of which is also connected to the clamps. of the load, the unit for control both the valves and the mode parameter sensor, the angle sensor between current and voltage from the power supply side is used as the mode parameter sensor and the system is equipped with a rotor current sensor and a supermator, one of the peai: current inputs of the sensor being connected to the current load, the second - the phase voltage from the source; power; its output is connected to one of the inputs of the adder, the second input is connected to the output of the angle sensor, and the output is connected to the input of the unit to control the valves. In addition, the system is equipped with a feedback circuit from the output of the adder to its auxiliary input, consisting of a series-connected adjustable limiter and a stabilizer. An isolation transformer is installed between the power supply and the power supply wires. FIG. Figure 1 shows an electrical power system comprising a reactive component compensation unit; in fig. Figures 2a, b, and c present the electrical characteristics illustrating the operation of the compensation unit of the reactive component of the current shown in fig. one; in fig. Figure 3 shows a simplified three-phase network of an equivalent line circuit. The transmissions in FIG. 4 a, b are electrical characteristics illustrating the operation of the current shear angle sensor shown in FIG. one; in fig. 5 shows a feedback loop with an adjustable limiter; in fig. b depicts a graph of the maximum value of the reactive load current in a selected time interval; the causative action of a limiting feedback scheme. The power supply system contains a power source — a generator 1 connected to wires 2,3 and 4 of the transmission line. B. A typical high-voltage power system, the linear transmission voltage may be on the order of 115 or 230 kV, which, after generator 1, is increased by a linear transformer. Thanks to step-down transformer 5, transmission lines 2,3 and 4 supply energy through wires b, 7, 8 to a powerful 5 and randomly varying load, shown as an electric arc furnace 9. Wires b, 7 and 8, hereinafter referred to as a furnace bus, can provide, for example, a bus voltage of 34.5 kV. Energy is supplied to the arc furnace 9 from the furnace bus through a switch 10 and a step-down transformer 11. In practice, the load in the form of an arc furnace 9 may consist of one or more three-phase arc furnaces. Due to the random nature of the electric arcs in such a furnace, there is sometimes a strong imbalance in the load current. On the selected part of the power system between ge. Carrier 1 and step-down transformer 5 to wires 2, 3 and. The 4 transmission lines can be connected to many other industrial, commercial, and domestic load circuits, such as application circuits, which are connected to lines 2, 3, and 4 by means of wires 12, 13, and 14.) It is recommended that the voltage on wires 12,13 and 14 when changing the phase or amplitude of the arc load current, the furnace did not change significantly in magnitude, so the wires 12, 13 and 14 represent the power supply bus by the critical voltage at which it is required to eliminate the fast cyclical voltage change, and hence the flickering of the lamp, n resulting from rapid cyclical changes in current and power factor in the arc furnace 9. The voltage between the line and the neutral wire, or the phase voltage on the critical bus, is Vo, and the phase voltage on the arc furnace is V. The invention is applicable to any the system of transmission or distribution of electricity or to any special load where it is desirable to compensate or neutralize the reactive component of the current and thus improve the power factor, but it has particular application in the load of the electric traction furnace. An electric arc furnace provides a basic load of such magnitude and electrical characteristics that it usually causes a noticeable low-frequency change in the system voltage and, as a result, an unpleasant lamp flicker in other loads of the power system. The invention is also used to compensate for load variations of draglines, rolling mill drives and long high voltage transmission lines. The impedance of an electric arc furnace consists mainly of active and inductive resistances and with a change in the melting and enrichment state in the furnace, the impedance changes dramatically and randomly. In particular, when a new charge of metal scrap is placed in a furnace, arc discharges experience sharp and noticeable physical changes for at least several minutes, until the charge of the furnace takes on a more or less uniform character. The arc current is determined to some degree opposing. furnace generated voltage This opposing voltage has a rectangular waveform and is in phase with a lagging or inductive arc current, the effective impedance of the arc varies dramatically depending on the shape of the arc, and it changes the phase ratio relative to the supplied load stress. Thus, for an external circuit, the arc furnace load acts as a variable inductive and variable active resistance. It is these characteristics that create quickly repeated changes of phase and magnitude, load voltage relative to the voltage of the power system and, therefore, low-frequency flicker of voltage. The frequency of these voltage changes is characterized by furnace parameters. It can be on the order of 3-6 periods per second. To neutralize the reactive current, in particular, the inductive current component in the load of the arc furnace 9, a compensating reactive current source was used, containing a group of three constant capacitors 15, 16, 17 connected to the wires 6, 7, 8 and connected by a star through the corresponding inductances 18, 19, 20 settings. In each arm of the capacitors connected by a star, a corresponding inductance coil is selected between the linear and neutral wires in order to adjust the capacitive choke 21 to the selected harmonic of the power system frequency, thereby shunting the current of this frequency and filtering such currents from the grid. Preferably, the capacitive choke 21 includes three separate groups connected by a star of constant capacitors, each group being tuned to a separate harmonic, in particular to the third, fifth and seventh harmonics of the fundamental frequency. There are predominant harmonics produced by arc furnaces and thyristor phase regulators. Adjusting, by such a cut, each harmonic filter, to a series resonance with a selected frequency for this frequency, a circuit with a low total resistance is provided, so that the harmonics produced by an arc furnace 9 or a thyristor-controlled choke 22 to the power network are not connected. if additional shunt capacitance is required, oi is preferably tuned to harmonics above the seventh frequency. An inductive reactance containing three series-connected pairs of inductors 23, 23j, 24 ,, and 25, 25 connected in a triangle circuit, each arm of the triangle containing one pair of inductors between them thyristor key. In particular, between the coils 23, 23. thyristor key 26 is turned on, between coils 24, 24rj is a thyristor key 27, and between coils 25, 25 is a thyristor key 28. Each thyristor key contains a pair of thyristors or a pair of thyristor groups connected in parallel and meet each other to provide opposite half-cycles of alternating current. In the inductive reactance of the coil, the inductance is connected by a triangle mainly in order to minimize the current consumption by the thyristors and the coils ciency. When the system is balanced, the triangular connection also serves to short the circuit for the third harmonic currents and eliminate them from the transmission line. The third harmonic is an ordinary harmonic generated by the validation of the phase of the single-phase thyristor switches.
    In an energy network, both a capacitive compensating choke and an inductive compensating choke. current of the arc furnace passing through this line. In order to provide a variable total value of the leading reactive component of the current, the compensating chokes are controlled by means of the control value of the lagging component of the current passing through the constant inductance of the throttles 22, and the fixed capacitors 15, 16 and 17 provide the specified constant value of the leading component of reactive current. Adjusting the phase of the inductive component of the compensating current thus alters the apparent reactivity
    Chains .. :: - ™ - -: ---- v - -: - - -
    The constant value of the capacitance of the capacitance. Immunity is provided with condensers connected in line or a combination of one sequence and parallel connected condensers. The action of the reactive component of a constant capacitor connected in series in a line can be changed by connecting a constant inductive coil through the thyristor control phase parallel to the capacitor.
    When the thyristor switches 26, 27, .28 fail to conduct, the work in the load circuit only has a capacitive capacitance capacitor throttle. When the thyristor switches are fully wired and fully 7, the inductive choke 22 becomes fully efficient and provides the specified lag component of the reactive current greater or equal than the leading reactive current component that is provided by the capacitive choke 21. Preferably the magnitude of the leading component of the reactive current, provided with capacitive and inductive (22) com 1; TH 1 imidross. me in, in each linear wire is maintained nfJPiftepHo melting or inductive component of the cable on Рр 1 Ж пю чи ё this line when measuring the condition of the state of aggression. .: -; :
    SSiSSS:
    When the inductive component of the current in the load is balanced with an equal capacitive component of the current, obtained from a combination of compensating chokes 21 and 22, only the power or the active component of the load current is connected to wires 6, 7, 8. If, in addition, the throttles 21 and 22 are compensated for by the inductive component of the linear current required by the buckling transformer 5, the full load outside the critical voltage bus becomes active,
    If it is necessary to ensure full compensation of the negative sequence of the components of the current, it is possible that the residual component of the compensating current may significantly exceed the leading component of the compensating current. In order to regulate the magnitude of the inductive component of the current passing through the compensating choke 22, the control valves of the thyristor switches Drossel 22 are used. This circuit contains the sensor 29 of the reactive component of the current that reacts to the zeo component of the current in the load circuit itself, which is designed to determine and. continuous adjustment of the conduction angle of the thyristor switches 26, 27, 28 so that the total is reactive. the current component, produced by compensating throttles 21 and 22, turned out to be equal in magnitude 1I opposite in phase to the reactive component of the load current. The first correction operates without a noticeable time delay and without feedback, so that an undesirable displacement or shift could introduce a mismatch in the setting of the compensation device. Therefore, the throttle valve control circuit 22 additionally includes a block that is sensitive to the power factor or current shear angle on the critical voltage bus, which serves to provide a signal for controlling the conductivity angle of the valves so that the power factor on the critical bus is kept constant, unit: 5 close to one. This adjustment through the linear current and voltage sensing elements provides negative feedback and is thus a regulating control device, in contrast to a compensating control device that is open at the end. x
    In order for the feedback not to reach the ratio and the result of the critical phase to form a signal and oscillations, a certain amount of time delay and frequency attenuation must be entered into the control loop. Due to such a time delay or decay the shear angle controller
    current is slow compared to a load current compensation system. The compensating load current control device and the current offset angle control device can be used either separately or together, as shown in FIG. 1. When used together, the compensating control acts quickly as the primary control, and the current offset offset control works as adjustments to prevent shear or other misalignment.
    The control circuit for compensation of the load current shown in FIG. 1 includes a reactive component current sensor 29 receiving input signals depending on the phase voltage on the critical busbar and the load current, and operating in the manner shown in FIG. 2 to create an alternating unidirectional or unipolar output signal controlled by angle-gated triggering signals that periodically light up or turn on the thyristor switches 26, 27, 28 for each instant compensation request. By a unidirectional or unipolar output signal, is meant the signal, its direction or polarity for any given state of the reactive composition of the current, the direction of correction, or the polarity of the signal, indicating whether the reactive component of the current is lagging or relative to voltage. Thus, although the polarity of the signal varies from time to time when the total resistance of the power grid changes, for any one state of the total resistance of the grid it is unidirectional or unipolar.
    By gating angle, we mean the phase angle relative to an external ac voltage signal at which each thyristor becomes conductive. This phase angle, measured from the beginning of the direct voltage externally applied to the thyristor, is referred to as gating angle in the following. The interval during which the thyristor then after each inclusion conducts is referred to below as the conduction angle. When the conduction angle for each thyristor is 1800, the key is considered fully on or closed, when the conduction angle is 0, the key is considered completely off or open. At intermediate positions of the corners and accordingly intermediate corners, the gating key for the half period is partially on and partially off and controls the value of: a different current passing through
    him, due to the ratio of the time of the on state to the time of the off state.
    Phase voltage signal. The reactive current component supplied to the sensor 29 is branched off from wires 6, 7; 8 through voltage transformers 30 j connected to wires 6, 7, 8 at points 31, 32 and 33, respectively. By converting the voltage signal V to the load at the output of transformers 30 using a linear current signal coupled through current transformers 34, 35 and 36, in the projector 37 the voltage of the critical bus is the phase voltage V
    5 and the value corresponding to the value of the voltage between the line and the earthquake wire or the phase phase on the critical bus. This reflected apl Vg ,, phase is thus taken into account for the necessary correction of the reactive effect of the transformer 5. The reflected voltage of the phase Y is applied to the sensor 9 of the reactive component of the current and interacts with the load current signal shown
    5 in FIG. 2 in order to generate an output signal during each half-cycle of the reflected phase voltage, representing the magnitude of the reactive component of the current in the circuit
    D furnace load 9. There are three such reflected voltage signals, vV, one for each line of the three-phase grid.
    FIG. 2a with a sagyusha line shows the reflected sig- nal voltage V for one phase supplied to the sensor 29 of the reactive component of the current. The dotted line also shows the load current signal 3i. in the corresponding load wire supplied to the sensor 29 from one of the other load current transformer groups 38, 39, 40 via the source 41 of the load current signal.
    To illustrate the operation of the sensor
    5 reactive looking for the current of the current Lee, shown in FIG. 2a, shows the phase cyms of eigenvalue relative to siggsha voltage from the leading ratio at the beginning, to the lagging ratio at the end. The sensor 29 of the reactive component of the current includes a circuit for instantaneous sampling and the direction of the current signal 3i. at each intersection
    5 zero by the voltage signal phase V ,,. These current samples are shown in FIG. 26. Sensor 29. Reactive current component also includes a signal storage facility for generating a unidirectional unidirectional output signal.
    0 signal (Fig. 2, c) having a magnitude and direction proportional to the magnitude and direction of the last previous instantaneous sample shown in FIG. 26. Thus, the output signal of the sensitive component of the current component is instantaneous unidirectional; the signal for each phase, the vetachina of which represents the magnitude of the reactive component of the load current in this phase at any moment, and the polarity shows the sign of leading or lag this load current. The instantaneous selection of the magnitude of the load current at the moment of zero position of the phase voltage is a direct measure of the magnitude of the reactive component of this current relative to the sampling voltage. Each of the output signals from the sensor 29 of the reactive component of the current periodically returns to zero every half-period the voltage of the phase passing in the critical bus; in full and in magnitude, these signals represent, respectively, the phase ratios and the magnitude of the reactive component of the current, which at any time must be supplied by compensating throttles 21 and 22 to bring the linear current cSMMapHoro 3.schK to one phase with the critical bus voltage Vj ,, which it had before. The adjustment of the leading components of the reactive current passing through the compensating, throttle 21, to the required value is performed by controlling the average value of the lagging components of the reactive current IXL. The inductor 22 is limited by the gating angles of the thyristor switches 26, 27, 28. The gating angles of the thyristors, given by the sensitive element 29, are so regulated and amplified on an instantaneous basis that the common reactive current (Zuc + 3 Provided with compensating throttles 21 and 22, it is equal in magnitude and opposite in direction to the reactive component of the load current 3 c in the arc furnace 9. To control the gate angles of the thyristor switches, from the current sensor to control unit 42 Conductor angles of conductors, including separate conductor angle control circuits for each thyristor switch, are supplied by three signals of reactive component currents. If, as shown in Fig. 1, a pack of Cr & Volleyoil component, is combined with control of the current or coefficient of current offset or coefficient power, the output signal of the sensor 29 of the reactive component of the current is supplied to the control unit 42 of the conduction angle Mlf via the adder 43. If only one or a second control signal is used, the Torus sum is not required ts. When the gating angles of the thyristor switches 26, 27, 28 are set in accordance with the output signals of the sensor 29 of the reactive component of the current, the sum of the compensating reactive components of the current and supplied from the compensating inductors 21 and 22 will be equal in magnitude and opposite in direction of the reactive component The current required to supply the load of the arc furnace 9 and the downstream transformer 5, so that the total linear current L, remains in phase with the linear voltage on the critical bus. Although FIG. 2, the current for the illustration is shown as a leading voltage signal vi at the same point is an unusual condition. The reactive current components required by both the load and the transformer 5 are in fact inductive, since the total reactive component of the compensating current supplied from the compensating inductors 21 and 22 is usually capacitive. It is for this reason that the constant reactive capacitance of capacitors 15, 16, 17 is usually greater than the inductive reactance of coils 23i, 232, 24 ,, 24, j, 25, 253. Thus, when the thyristor switches 26, 27, 28 appear completely conducting (apparent reactive inductive resistance is minimal), so that the compensating inductive component of the current in the choke is maximum, then such a current is usually at least slightly less than the capacitive component of the compensating current in the choke 21. A case where the reaction is ivna component of the load current in at least one line may be advanced, such as in conditions of absence of an arc in a single phase arc furnace. In order to fully compensate, in this case, the choke 22 must be able to supply the lagging components with currents of a greater magnitude than the specified leading components of the current in the inductor. . While in FIG. Figure 2 shows the phase voltage signal and the load current in only one line, the three-phase network shown in FIG. 1 and 3, includes three such interconnections and it is assumed that three are produced as shown in Fig. 2c of the signal of the reactive components of the load current. These three signals in a balanced network will be equal, but in the case of an unbalanced load they will be different at any moment, therefore, in the case of an imbalance in any half-period, the resulting gating angles in different keys 26, 27, 28 are not the same. Due to the described control, these gates are set every half-period in accordance with the existing load current conditions. The total compensatory reactance between a couple of linear wires {due to the combined action of the chokes 21 and 2, necessary to perform the required compensation of the reactive component of the load current in each line of the three-phase grid, can be expressed by the corresponding reactive components of the load current as follows: 011-21 , B 41-2.1 -.LX-JILX-UX bE. where Xc is the total compensating capacitive reactance between the specified pairs of linear conductors aLX Lc and the lagging reactive components of the load current in the corresponding wires of the load circuit. If the solution of these equations in any case gives a negative V, it means that the total compensating reactance should be inductive rather than capacitive. From the above dependences, it is clear that controlling the phase of the current with each key 26, 27, 28 to determine the apparent inductive-reactive resistance in the corresponding branch of the throttle 22 should depend on the sum of all the reactive components of the load current produced in the manner specified by equations. The total compensating reactance between each pair of linear arcs can be expressed in terms of the active and reactive components of the load current as follows. U 1lX | SVx lV / Ь.-,, L. L. Vl2-, l A-i-. t ..in .-, .-, bVb bL ". W 9riux OiLX J c | 2, -C-2b.i -. u ± i-5 bJl ii.e. 2L.4 tV where -3,, JjLii. and 3j ,, are the active or coincident components of the load current in the corresponding wires of the load circuit, and the other symbols have the same values that f4j, nH are set for the equations before the sensor 29 though is designed to bring the resulting component The total linear current of 3T to zero does not affect the 3aMeTHoto reactive component of the load current to which the reactive component sensor 29 responds. . current, therefore, the G-Neurology of the feedback loop, by means of which it could be shown whether the corresponding adjustment is made in the sensor 29. Thus, if the output signal of the sensitive element of the reactive component of the current is superimposed or if the control circuit between the output of the sensing element of the current and the thyris gates introduces a mismatch of any limit or gain, the compensation range of the reactive component of the current can be shifted and the mismatch in done in order of compensation. When operating without feedback, such a mismatch will not detect the compensation circuit, therefore, a current angle sensor or a phase angle regulator are used in conjunction with the reactive current sensor. A current offset angle sensor 44 provides a linear current signal from current transformers 34, 35, 36 and reflected voltage signals branched off from a common linear current Lgp and load phase voltages V, which in terms of magnitude and magnitude represent phase voltages of the system Vg on critical tire. The reflected system voltage signals, branched from the voltages to busbars 6, 7, 8, are the main components of the formerly Spiral current-current angle sensors and the reactive current-current sensor. FIG. 3 is a simplified diagram of a portion of the apparatus network shown in FIG. 1. In the power grid of FIG. 3, the transmission line impedance is represented as a series impedance in series in each phase, and the impedance of transformer 5 is lowered in the form of an impedance 2 t in series in each phase of the system voltage Vg, on wires 2, 3 and 4 between the impedances and T-T are critical bus voltages that need to be kept constant by maintaining the in-phase state of the line currents 3 | T1. On the impedance of 2m from the side of the load on the conductor 1 6, 7, 8, the load voltage VL appears. In order to branch the reflected signal of the nep from the voltages of the load VL; system stresses / к which are the largest and phase voltage
    Phase system Vj, there is a set of voltage transformers 30 (Fig. 1 and 3), consisting of two voltage transformers 45 and 46. The primary winding of the transformer 45 is connected by a triangle and is powered by the loading of the load between the linidmi, and the secondary winding 5 is connected by a star. At each secondary phase winding, a transformer 45 appears in-phase proportional to the load voltage copy between the lines, 10
    The star-connected secondary windings of the transformer 45 feed the triangle-connected primary windings of the second transformer 46 and a series. The secondary winding of the transformer 15
    46 are also connected by a triangle. The voltage tta of each phase winding of the transformer 46 voltage is the in-phase copy of the voltage between the line and the neutral wire or. 20 phase V voltage, on tires 6, 7, 8
    ovens. - V-.;: -::: - iTO6H convert. the output signal of the transformer 46 to match the phase and amplitude of the voltages of the phases of the critical bus on wires 2, 3 and 4, is necessary for each phase to be fully connected. this voltage output d, i.e. make it common mode with a voltage drop on the corresponding impedance 30 of the transformer 5 and proportional to the reduction factor of the transformer 30 ny) yjby. For this purpose, each line of the current transformer 34, 35, 36 (in Fig. 3 shows only 35 one phase of it) includes the equivalent of impedance 2, proportional to the impedance of transformer 2 and the voltage of the voltage transfer voltage transformer. Q
    Output impedance
    47p is the voltage of one secondary winding of the transformer 46 and the corresponding impedance, phase z, on the terminal of which a signal is also applied of the reflected voltage of phase V. The V signal for each phase is accurately phased with the corresponding phase response of the critical bus bar. It is these reflected ",. ,, (and proportional to them) voltages 50 of the critical bus that are applied to the current shear angle sensor 44 and the reactive component current sensor.
    In order to generate an output signal, it corresponds to the angle of shift of the phases of an SFL with a linear current and the voltage of the PH phase of the UL at the critical T1dayeTs t | There is a single voltage signal Vg, in each phase in the sensor 44 of the current displacement angle 60 ts with the total linear output voltage of the line current source source of the linear current signal source.65
    FIG. 4a, a solid line shows a graph of the reflected voltage signal of a system placed on one time scale with a corresponding total line current of 3f shown by a dotted line. To illustrate, the line current 3f is shown varying in phase with respect to the system voltage from the lagging initially to the leading end of the ratio. The advance ratio cannot exist, excluding extremely low loads. Datascale / current shear includes integration tools to create a signal, O1 "which is an equivalent value that corresponds to the time offset or phase between the zero of the linear current and the zero of the system phase voltage (Fig. 4a) and has a polarity that is relative to the lagging or falling ratio the phases of the current of the SC and the voltage Vj,. Such an integrated signal is shown in FIG. 46. The integrated signal generated in this way for each half-period is fed to the corresponding signal storage memory, which creates a continuous output signal, which at any Moment is unidirectional with a UCF value equal to the last previous integration time shown in FIG. 4b, and the polarity of the cooTfieTuT ylceuyid polarity of the last decimal integrated signal. FIG. 4c shows a non-transient unidirectional output signal, the polarity and magnitude of which in each half-period is set in accordance with the integrated signal shown in FIG. 4b, and in accordance with the instantaneous phase relationship between current and voltage or current shear angle shown in FIG. 4a.
    The alternating unidirectional output is 6 lbs; and the current is supplied to the adder 43 via the stabilizer 49, the time constant in the control loop.
    In the adder 43, this one-directional signal of the angle of displacement, the current is added to the unidirectional signal of the reactive component of the load current, received from the sensor 29 in order to set such an output signal, the adder, which provides adjustment of the conductivity angle control unit of the thyristor 42, allowing power factor on a critical bus is constant, preferably equivalent to one. If a power factor is required, which differs from unity, a positive or negative bias signal of the corresponding amplitude can be applied to the adder 43.
    Controlling the current shear angle provides negative feedback through the power system wires. In particular, any generated current shear angle signals control the gating angles — the thyristors and the total reactive component of the compensating current. The phase position of the line current is set equal to or close to the desired value, whereby the current shear angle signal is destroyed. It is because of this feedback that stabilization circuit 50 is needed. Mainly due to the fact that the control circuits have the characteristic of a constant time, the message of any change of the control signal is transmitted through the control circuits to the thyristors, and from them back over the power grid taking into account the temporal characteristic. The rate of change determined by such a time characteristic corresponds to frequency. If the intrinsic time constant of the control loop and the feedback loop were such that the intrinsic delay in the terms of this frequency was 180 ° relative to the frequency of the time characteristic, the feedback would be negative in design, would become positive and cause amplification and oscillation.
    In order to prevent this effect, the stabilization circuit 50 additionally introduces sufficient control to the control loop for the oscillation time. On the other hand, because of this delay in signal transmission through the current angle control loop, this control is not performed as quickly as we would like. If only one response were used to compensate for a total throttle of 22, the delay would be significant. However, when adjusting the current shear angle is used in conjunction with the load current compensator, the current shear angle signal is usually very small and acts only as a correction for any inaccuracy of the device, controlling the load current without feedback.
    In some cases, instant. the surge of the maximum value of the reactive compensating current may exceed the maximum possible or nominally permissible upper limit of the compensating chokes, although the amplitude of changes of the maximum value is within the limits of the possibility of throttles. Therefore, if desired, the system can be equipped with a means to limit the maximum to a certain predetermined average value of the value of the reactive component of the current or the reactive current-voltage components supplied from the compensating inductors 21 and 22. Since the capacitive compensating choke 21 provides a constant value of the leading reactive component current, this control signal is applied to the inductive compensating choke 22. Ddl
    This goal is provided by an adjustable limiter circuit 51, which receives the output signal of the adder 43 and, through the stabilizer 49, supplies a limiting negative feedback signal to the cyMMaiTopa 43 input. The stabilizer time constant is shorter than the six-period arc furnace.
    The effect of the feedback constraint chain is illustrated in FIG. The horizontal time scale of FIG. 6 shows a typical oscillatory characteristic of the maximum value of the reactive TOIFYYUH6 of the 6th furnace over an illustrated period of time that is smoothed and after a new charge of the furnace. reduced To comp. relative to stationary mode. Due to the physical characteristics of the furnace and the arc, this curve of oscillation of the maximum value has a frequency of about 6 periods of 1 s.
    The ordinate of the graph represents the maximum and maximum value of the reactive current of the smoke in percent, where 100% corresponds to the maximum of the maximum value. If it is desirable to limit the maximum of the compensating reactive current to a level less than the maximum value,. slightly lower
    0 35 40 of the required full compensation under the limiting conditions, so that the power factor on the critical bus will be maintained postO} T during the operation of the limiter, wo is a certain specified value less than one. This may be desirable for limiting the size and power of the compensating chokes 21 and 22 and does not raise reasonable objections. A relatively small loss in power factor on a critical bus makes it possible to control the voltage slightly, but fairly well. In addition, if the reduced power factor is maintained
    5 to a constant over a long period of time compared to the period of the period A of the maximum value shown in FIG. 6, the voltage flicker will be further reduced.
    0 55
    FIG. Figure 5 shows a limiting feedback circuit adapted for the purpose described above. A total mismatch signal from the output of the accumulator 43 is applied to a pair of output terminals 52 with a marked polarity, and the output impedance 53 between the output terminals 54
     connect to the output terminals 52 through a series circuit of the battery 55 and the blocking diode 56.
    0 65
    权利要求:
    Claims (3)
    [1]
     Battery 55 is turned on to receive a mismatch signal at terminals 52, so that the current does not flow through the blocking diode or the limiting circuit until the mismatch signal exceeds the depleted value a little higher than the reverse bias: battery voltage 55. When the mismatch signal exceeds such a reverse voltage bias, through diode 56 and the output impedance of 53 current leaks. - While diode 56 conducts, battery 55 delivers a constant backmixing or delay to the input error signal and reduces the output The error signal at terminals 54 is the magnitude of this offset. The long time constant of the capacitor 57 connected in parallel with the output terminals 54 maintains the error output at terminals 54 for several cycles of changing the maximum furnace load, so that instantaneous decreases in the error output below the bias voltage will not intermittently interrupt the feedback. The capacitor 57, in combination with the resistance 53, functions as a stabilizer 49 (Fig. 1) and provides a large time constant for the feedback signal, i.e. order of several periods of oscillations of the frequency of change of the maximum furnace load. . Curve B (Fig. 6) shows the above offset or delay signal. This curve represents the limiting feedback signal and, consequently, the subsequent value of the delay of the reactive current relative to the maximum value of the reactive load current, therefore the resulting limited error signal applied to the conduction angle control unit 42 is equal to the sum of the curves A and B, shown in FIG. 6. The claims 1. AC power supply system, comprising a power source, supply wires and a reactive current compensation unit, consists of chains connected in a star and including series-connected capacitors and inductors, whose terminals are connected to the load terminals , from chains, formed from series-connected controlled valves and inductors, connected in delta, the conclusions of which are also connected to the load terminals of the unit for controlling neither a valve nor a mode parameter sensor, characterized in that, in order to increase the accuracy of voltage maintenance in the supply network, an angle sensor between current and voltage from the power supply side and the system is equipped with a reactive sensor as a mode parameter current and an adder, one of the inputs of the reactive current sensor used to connect to the load, the second to the voltage of the power supply, its output is connected to one of the inputs of the adder, the second input of which is connected to the output The angle sensor house and the output are with the input of the unit for controlling the valves. . 2. The system according to claim 1, characterized in that it is provided with a feedback circuit from the output of the adder to its auxiliary input, consisting of series-connected pnEgulyazhimi limiter and stabilizer. 3. The system according to claim 1, characterized in that an isolating transformer is installed between the power supply and the supply wires. Sources of information taken into account in the examination 1. US patent 3551799, cl. 233-8, 1970.
    [2]
    2. Electrical engineering USSR. T 1, 1969, p. 46-62, Pergamon Press, 1969.
    [3]
    3. Authors certificate of the USSR 251662, cl. H 02 J 3/18, 1962.
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    US05/406,139|US3936727A|1973-10-12|1973-10-12|High speed control of reactive power for voltage stabilization in electric power systems|
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