SU1464245A1 - Reactive power compensator - Google Patents

Abstract

The reactive power compensator (CRM), designed for electrical networks and electrical installations, provides for the issuance or consumption of regulated reactive power. The goal is to improve technical and economic indicators. The CRM includes at least one SI. BULK transformer and one three-phase rectifying bridge connected to its secondary winding, which has thyristor and lockable valves, a reactor connected to the pole m of the bridge, capacitors for limiting overvoltages, connected in parallel with the secondary winding of the transformer capacitors for transferring current from thyristor valves to lockable, connected in the bridge phases between the thyristor and lockable gate nodes, as well as valve control devices. The capacitance of the capacitors in the bridge phases is determined from the condition that the negative anode voltage is applied to the thyristor valves for a time that is not less than the time they are turned off. At angles of regulation close to -90 ° C, the AAC provides reactive power to the three-phase network to which its transformer is connected. For control angles close to - | -90 °, the AAC consumes reactive power from a three-phase network. The magnitude of the reactive power delivered or consumed is controlled by varying the control angle in the range of several degrees. The main distinguishing feature of the CRM is the provision of current transfer from the thyristor valves to the lockable ones due to the inclusion of capacitors in the phases of the rectifying bridge. This technical solution as compared to the known one (an increase in the thyristor valves of series-connected thyristors) has significant technical and economic advantages: a reduction in capital costs and an increase in the efficiency of the compensator are achieved. 2 Il. € (L 4 05 NU to 4 1СЛ

Description

one

This invention relates to electrical engineering and can be used in electrical networks and electrical installations to compensate for reactive power.

The purpose of the invention is to improve the technical and economic indicators of the compensator by ensuring that the current is transferred from the thyristor valves to the locked ones without an increase in the number of thyristors in series in the thyristor valves.

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FIG. 1 shows a diagram of the proposed compensator; in fig. 2 - voltage and current curves of the compensator in the mode of issuing reactive power.

The compensator (Fig. 1) contains a three-phase rectifying bridge with valves 1-12, capacitors 13-15 for transferring the current from thyristor valves 2, 4, 6, 8, 10 and 12 to lockable vents 1, 3, 5. 7, 9 and 11, a three-phase power transformer 16. through

which is a rectifying bridge connected to an AC network, a reactor 17 connected to the poles of the bridge, capacitors 18 for limiting overvoltages connected in parallel to the secondary winding of the transformer 16 through a three-phase switch 19. Gates 1 -12 number of pulses in the order of their opening management As lockable gates 1, 3, 5,, 9, and 11 are depicted as a latch.: Thyristors, but the circuit will not change if they use electrically () ny, 1c lamps or power transistors.

The capacitor 13 includes a rectifying bridge in phase A between the node where thyristor valves 4 and 10 are connected and the node where lockable valves 7 and 1 are connected. Similarly, the capacitors 14 and 15 are connected, respectively, in phases B and C of the bridge.

With the mentioned switching on of capacitors 13-15, phase terminals A, B and C of secondary transformer 16 must be connected respectively to nodes A, B and C of the connection of thyristor valves 2, 4, 6, 8, 10 and 12. These.m. in addition to the capacitors 13-15 and the flow of currents of the locked valves 1, 3, 5, 7, 9 and 11 through, these capacitors 13-15. With the conductivity of the locked valves 1, 5 and 9, the currents through the corresponding capacitors 13-15 pass in one direction, and with the conductivity of the locked p, e.ggiley 7, 1 and 3 - in the opposite direction. This provides periodic recharging of capacitors 13-15.

The compensator control system (Fig. I) contains voltage sensors 20-22 connected to capacitors 13-15, sources 23-25 of the primary impulses of the lockable gates and the drivers 26-28 of the control impulses of the locked ventilation lines, related a1 respectively to lockable valves 1, 5, and 9, sources 29-3 of primary pulses of thyristor valves and formers 32-34 of controlling thyristor-controlled impulses, related respectively to thyristor valves 10. 2 and 6, delay elements and elements AND 38-40.

Control devices for valves 4, 7, 8, P. 12 and 3 of the anode rpyrnibi are the same as for valves 10, 1, 2, 5, 6, and 9 of the cathode group.

Pa figs. 2 on the axis 41, a three-phase system of voltages connected to a knot is constructed. ikm .l, b and c rectifier bridge. Voltages L l. UB and Ijc. - these are the phase voltages of the secondary winding of the transform atomo-. ra 16 when idle. The sequence n of their voltages determines the sequence of unlocking and switching on the gates L- 12. On axis 42, the time curves of the currents iio, ia and i.e.

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0, 2 and 6 vents and currents i |, is and ig of lockable valves 1, 5 and 9, on axis 43 - time curves of currents of thyristor valves 12, 4 and 8 and lockable valves 3, 7 and 11, on axis 44 - curve voltage Uis capacitor 13.

The two inputs of element 38 (Fig. 1) are connected to a source of primary pulses 30 and a voltage sensor 20. Element I 38 refers to a lockable valve 1, and source 30 of primary pulses to thyristor valve 2, i.e., a valve that is unlocked and activated next to valve 1. Element I 38 first receives a signal from source 30 of primary pulses and then from voltage sensor 20. Thereafter, the element AND 38 sends a signal to the driver 26 of the control pulses, which outputs negative (locking) control pulses to the locking valve 1. As a result, the latter is locked at the moment when the voltage of the capacitor 13 becomes equal to Uco (with the element AND 38 the output of the voltage sensor 20 is connected, on which a signal appears during the voltage of the capacitor 13 -Uco).

The other output of the voltage sensor 20 is connected to the input of the element AND, which relates to the lockable valve 7 (this element And is not shown). As a result, the closure of the valve 7 occurs at the moment when the voltage of the capacitor 13 becomes + Uco.

Similarly, the inputs of the element AND 39 are connected to the outputs of the source 31 of the primary pulses and the voltage sensor 21, and the output of this element I is connected to the driver 27 of the control pulses. The second output of the voltage sensor 21 is connected to the input of the element AND, which relates to the lockable valve 11. Similarly, the element 40, the source 29 of the primary pulses, the sensor 22 of the voltage and the control generator 28 of the pulses are connected. The second output of the voltage sensor 22 is connected to the input of the element AND, which relates to the lockable valve 3.

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The operation of the compensator in the mode of issuing reactive power is considered using time schedules (Fig. 2).

Until ti, the current can flow through the thyristor valve 10. At this time, the voltage of the capacitor is 13 Ui3 + Uco (positive charge on the right side of the capacitor plate). By this, an anode voltage is higher than a lockable valve 1 to a lockable valve 1. At the time ti, a positive (unlocking) control pulse arrives at the lockable valve 1, and since its anode voltage is sufficiently large, it turns on. Under the action of the voltage of the capacitor 13, the current quickly passes from the thyristor valve 10 to the lockable valve 1. The current ii of the valve 1, the passage through the capacitor 3, produces its recharge.

In the interval At, the voltage of the capacitor 13 Ui3 decreases from - | --Uco to a value equal to the voltage drop of the lockable valve 1, and therefore during this period of time a negative anode voltage is applied to the thyristor valve 10. The capacitance of capacitor C is designed so that it is 1 o'clock, where 1pk.g1 is the turn-off time of the thyristor valve. Due to this, a condition is provided for restoring the controllability of the thyristor valve 10 after its current has dropped to zero at time ti (it cannot turn on when, after i, a positive voltage is applied to it).

After the time ti, after a time lag ;, set by the delay element 35, the thyristor valve 2 is unlocked. However, it cannot yet be turned on, since at this time its anode voltage is negative. The gap bb is chosen such that it is less than the gap tit2 recharged capacitor 13. In particular .- (then tsa.i is less than b).

By the time ts, the voltage of the capacitor 13 Ui3 becomes -LJco. At this point in time, the voltage sensor 20 sends a signal to the input element AND 38. There is already a signal at the other input of this element, since tii .. The element 38 sends a signal to the second input of control driver 26 and, as a result, to the lockable valve 1, a negative (locking) control pulse is applied. Valve 1 is closed, current II rapidly decreases to zero. At the same time, on the thyristor valve 2, the anode voltage rises abruptly and becomes positive. Since there is already a control pulse on its control electrode, it immediately turns on and begins to pass the current of the compensator.

Half a period (1/2 T) after the moment ti in. Moment 1c positive (unlocking) control, a pulse arrives at the lockable valve 7. At this time, a positive anodic voltage is applied to the lockable valve 7, which is higher than its voltage switching on (this is ensured by the fact that the voltage of the capacitor 13 Ui3 is LJco and the positive charge has the left side of the capacitor 13). As a result, the lockable til 7 is turned on at the moment is, and under the action of the voltage of the capacitor 13, the current almost instantaneously passes from the thyristor valve 4 to the locked valve 7.

Under the action of current i of the lockable valve 7 in the gap iji, the capacitor 13 is recharged: its voltage Uis varies from –i.:. to 4-1l-o. A negative anode is provided.

voltage to the thyristor valve 4 at time ti tBbiK.i.

At time t4, when Ui3 becomes equal to +, voltage sensor 20 sends a signal to the element AND relating to the lockable valve 7. As a result, the current of the lockable valve 7 ceases to turn on the thyristor weytl 8. Similarly, processes with capacitors are charged 14 and 15 and current transitions of thyristor valves to lockable in phases B and C of the valve bridge. The compensator operates at an adjustment angle close to -90 °, due to which its alternating currents are ahead

5, the corresponding voltages are at the same angle and the compensator delivers reactive power to the network.

To transfer the compensator from the mode of issuing reactive power to its mode

0 consumption is enough to change the angle of adjustment, making it close to - | -90 °. In the mode of reactive power consumption, you can switch to natural switching of thyristor valves 2, 4, 6, 8, 10 and 12, eliminating the work of locked

5 valves 1, 3, 5, 7, 9 and I. To accomplish this, unlocking of the locked valves 1, 3, 5, 7, 9 and 11 is stopped. At the same time, the lifetime of the valves I-12 and the capacitors 13-15 increases. . In addition, in this mode, to increase the capacitor resources 18

0 they are turned off by switch 19.

Claims (1)

Invention Formula  A reactive power compensator containing at least one power 5 a transformer and one three-phase rectifying bridge connected to its secondary winding with two thyristor and two lockable gates in each of its Phase, a reactor connected to the poles 0 bridge, capacitors connected in parallel to the secondary winding of the transformer, a control system for each thyristor valve, having in its composition a source of primary pulses and a driver for controlling pulses, a system for controlling each lockable valve, and having in its composition a driver for controlling 1 pulse with two inputs, the first of which - on the formation of the unlocking, and the second - the locking pulse, and the source of primary pulses. 0 the output of which is connected to the first input the driver, as well as delay elements and intermediate elements according to the number of thyristor valves, the source of the primary pulses of each thyristor g of the valve being connected through the delay element to the source of the primary pulses of the lockable valve, which is previous in the order of activation, and the source of the primary pulses of each thyristor fan An intermediate element is connected to the input of its driver and e-cutter to the second input of the driver for control of their pulses of the lockable valve, the previous order of switching, characterized in that, in order to improve technical and economic indicators, in each phase of the rectifying bridge between the junction of the type The histrophic valves and the connection point for the lockable valves are switched on a capacitor, which is connected to the voltage sensor. 0 having two outputs, AND elements with two inputs are used as intermediate elements, with two outputs of a voltage sensor of each phase connected one at a time to the first inputs of two AND elements related to lockable valves of the same bridge phase, and the second inputs of these elements AND are connected respectively to the outputs of the sources of the primary pulses of two thyristor valves, which follow in the order of switching on. F F L / / | F F one. L 1G -JHI; 24  J5 Pl Jlh 0 /