SU1257746A1 - Method of compensating static and sharply variating reactive load - Google Patents

Abstract

The invention relates to the field of electrical engineering and can be used to automatically compensate for reactive power in alternating current electrical networks containing consumers of reactive energy with a variable nature of load. The purpose of the invention is to improve the quality of the electrical network voltage while simplifying the main current circuit of the compensating device. In this method, by increasing the response rate of the compensating device to switching on the reactive load of the electrical network by phase control of the voltage of the throttle, together with improving the accuracy of tracking sudden changes in the reactive load of the electrical network, eliminate the voltage fluctuations in the electrical network and the load of the power source. In addition, the method of compensating highly variable loads exceeding the power of the throttle by combining the phase regulation of the voltage of the throttle with connecting the backup capacitor battery stages and then returning these stages and the throttle to the original mode makes it possible to reduce the installed throttle power and the capacitor battery stage whose currents balance each other in the original mode. Blocking the inclusion of large reactive loads of the electrical network (surpassing the power of the throttles) with a lack or absence of the reserve power of the capacitor battery and increasing the latter by disconnecting the previously connected steps to re-enable them during the joint phase regulation of the voltage of the throttle eliminates overloading the power source and prematurely entering work (backup power source, and the implementation of load control of the power source in the process of output to the reserve The connected capacitor bank steps and the start-up of the backup power source with an increase in the load current of the operating power source of the set value prevents the protection of the latter from overloading and de-energizing the mains. 1 or. (L sd vj 4 O)

Description

The invention relates to electrical engineering, in particular, to means of automatic compensation of reactive power in electrical networks of alternating current containing consumers of reactive energy with a variable nature of the load,

It is known that regulating the voltage of the drossel by changing the thyristor control angle of the high-speed switch results in the appearance of the drossel 9 in current, and hence the higher harmonic generator. This, in turn, causes a distortion of the voltage curve of the electric network that causes circulation higher harmonic current in the electrical network and its load. The currents of higher harmonics cause additional losses of electricity and create the danger of overloading a capacitor battery, the resistance of which is inversely proportional to the number of the highest harmonic. Therefore, to eliminate the negative effects associated with the phase regulation of the voltage of the throttles, higher harmonic filters are introduced into the compensating device by connecting in series with capacitors — each stage of an inductive impedance capacitor bank — reactors. This leads to an increase in the size and weight of the compensating device and additional electricity costs. method j while maintaining nominal throttle voltage in established modes due to the use of stupas nchato D adjust- able principle of compensation of reactive loads electric network, allows to eliminate these negative phenomena, t "e, distortion of the electric voltage curve. network and additional losses from higher harmonic currents to refuse to use reagents. Compensating for highly alternating reactive loads of the electrical network by means of phase-controlled voltage of village reactors is characterized by greater speed and more accurate tracking of the surge of the electrical load current of the electrical network compared to connecting a group of capacitor bat stages. yards, since it is known that in order to eliminate charge currents

.

257746 with

20

25

switching on the capacitors should wait for the moment when the instantaneous value of the voltage of the network is equal to the residual voltage on the capacitors with the opposite sign for each phase separately, according to the proposed method by increasing the response speed of the compensating device to turn on the reactive load of the electrical network by phase regulation of the voltage of the thrusts connecting capacitor bank steps at the same time as improving the accuracy of tracking sharp changes in reactive electrical load the networks achieve the elimination of voltage fluctuations in the electrical network and the load of the power source. In addition, the proposed method of compensating for alternating loads of the electrical network, exceeding cx by the magnitude of the power of the throttle, by combining the phase regulation of the voltage of the throttle with connecting the backup levels of the consumer battery and the subsequent return of these levels and the throttles to the original mode allows to reduce the installed power of the throttles and the level of the capacitor battery, the currents of which balance each other in the initial (stabilizing) mode.

The blocking of the inclusion of large reactive loads of the electrical network (exceeding the power of the throttles) caused by the lack or absence of the reserve power of the capacitor battery to the magnitude of the latter by disconnecting the previously connected steps for the purpose of their subsequent re-activation during the phase regulation of the voltage of the throttles excludes over-loading of the power source and early input to the backup power source, and the control of the load of the power source E by the process of transferring to the reserve the connected stu charge a capacitor battery and run a backup source. When the load current of the working power supply increases above the set value, it warns | The operation of the latter's protection against overload and de-energization of the electrical network.

The drawing shows a schematic diagram of a compensating device.

thirty

40

50

properties, implementing the proposed method.

The compensating device consists of an inductive element — droplets 1, and a capacitor bank, divided into stages 2–5, whose powers are in the ratio 1: 2: 4: 4. Moreover, the unit power of the largest stages 4 and 5 are equal to the power of the throttles. The choke 1 and the first three stages 2-4 of the capacitor battery are connected via high-speed thyristor switches 6 and 7 and the electrical network 8 to the power supply 9, for example, to a synchronous generator. One of the largest stages 5 of the capacitor battery is connected directly to the electrical network. The composition of the mixed load of the electrical network includes reactive loads 10.1 and 10.2, for example, asynchronous electric motors. These loads are connected to the electrical network by means of switching devices 11, for example magnetic actuators. Changes in the reactive load of the electrical network are recorded by the sensor 12 of reactive current containing two outputs 13 and 14, one of which (13) forms a high-speed signal of a change in the network’s reactive load during a transition period, and the other (14) shows a delayed signal of a change in the network’s reactive load established modes. Signals proportional to changes in the reactive load of the electrical network are sent to control unit 15, provided with outputs 16-18, through which these signals are transmitted to block 19 of the throttle voltage phase control and control pulse shaping unit 20. thyristors of high-speed switches 7, including the steps of a capacitor bank. The load of the power supply is monitored by current sensor 21. Depending on the power ratio of the throttles and reactive loads, the latter are divided into two groups. The first group consists of reactive loads 10.1, the starting power of which is less than the power of the throttles. The second group is formed from reactive loads of 10.2 1s with starting power exceeding the power of the throttle.

7464.

The reactive current of the power source must not exceed the specified value.

In the initial mode, the choke 1 is connected to the electrical network for the nominal voltage of the electrical network and is equal in power to the power level 5 of the capacitor battery. In this mode, the control voltage generated by the control unit 15 at its output 16 and supplied to the phase control unit 19 is zero. It corresponds to the complete opening of the thyristors of the high-speed switch 6, i.e. thyristors operate at zero control angle. The total reactive current I of the compensating device, defined as

Kf

 1С5Ч

(one)

where i

CS

and h the rated currents of the step 5 of the capacitor battery and the choke, respectively, are equal to zero.

in the initial mode, stages 2-4 of the capacitor bank are disabled. A reactive load 10 of the electrical network is turned on - an induction motor, the starting current of which is less than the nominal throttle current and is, as is known, reactive. The reactive current sensor 12 measures the change in the reactive component of the load current of the power source 9 with respect to the predetermined and at its output 13 a signal is generated that is proportional to the change in this current during the acceleration of the asynchronous motor. This signal is sent to control unit 15, at output 16 of which a control voltage is generated, whereby the phase control unit 19 increases the angle of control of the thyristors of the high-speed switch 6. At the same time, the voltage and current of the throttles are reduced by the increment of the reactive current of the load of the power source and the resulting current of the compensating device in accordance with formula (1) is increased by the same amount, to compensate for the increase in the reactive load current of the power source relative to a predetermined value. At the end of acceleration

asynchronous motor and reducing its starting current to the nominal value; the high-speed signal at the output 13 of the sensor 12 of the reactive current and the control voltage at the output 16 of the control unit 15 are again zero. As a result, the voltage and current of the drossel are restored to nominal values, and the resulting current of the compensating device returns to zero. After the set time delay has elapsed, the output 14 of the sensor 12 of the reactive current generates a signal j proportional to the increase in the reactive current of the load of the source 9 of the power supply in a steady state. This signal acts on the control unit 15, by means of which the output signal of the smallest backup stage 2 of the capacitor battery is generated at its output 17, and is converted to the thyristor control pulses of the high-speed switch 7 stage 3 using the pulse shaping unit 20. As a result, the compensating device current increases:

(4V

 I

WITH

 1sg - IL

As a result, the increment of the reactive current of the load of the power supply 9 in a steady state is compensated.

If it is necessary to turn on the reactive load 10.2 of the electrical network, the starting current of which exceeds the nominal throttle current, then a switch-on signal is generated in the magnetic starter 11 of this load, which is sent to the control unit 15. In the control unit, after receiving this signal, the numbers of the connected capacitor battery stages and the stages in reserve are monitored. If it turns out that at the moment when this signal for switching on the reactive load 10.2 stage 4 of the capacitor battery is in reserve, then in the control unit 15 both command signals are turned on to turn on this reactive load and stage 4 of the capacitor battery, which act on the magnetic starter 11 and the unit 20 pulse shaping, respectively. Then, as in the previous case, sensor 12

the reactive current is measured by the transient load current of the power source and at its output 13 a fast-acting signal is formed, proportional to the change in the resulting reactive current of the power source (I ,, - I) where, is the reactive component of the starting current of the load; 1 - current stage 4 capacitor bank.

This signal acts on the control unit 15, by means of which the control voltage is produced. In accordance with its value, the control unit 19 of the phase control increases the control angle of the thyristors of the speed switch 6, and consequently, the voltage and the throttle current decrease by an amount equal to the difference (2 „,, С4

uncompensated transient load current of the power source after simultaneous connection of the reactive load of the electrical network and stage 4 of the capacitor bank. By

The end of the transient process in the reactive load 10.2 at the time of establishing the zero signal and the output 13 of the sensor 12 restores the nominal voltage and current flow and disconnects the level 4 of the capacitor battery. After a time delay at the output of the sensor 14. 12 a reactive current produces a signal proportional to the change in

a steady state power supply reactive current. This signal acts on the control unit 15, H1-III, which generates the command signal for switching on the backup stage of the capacitor battery in accordance with the switching program with step regulation by code 1; 2s4, the pulse generation unit 20 performs the corresponding

switched over these steps.

If at the moment when the control signal for blocking the high reactive load 10.2 arrives at stage 15 that the capacitor battery stage 4 is already included in the electrical network and the total reserve power of the capacitor battery is less than the throttle power, then the control unit generates the specified reactive signal load and at the same time a command signal is generated, l disconnection B reserve level 4 capacitor

Noah battery. At the same time, the current sensor 21 monitors the magnitude of the increasing load current of the power supply. After that, the control unit is removed (blocking and simultaneously the reactive load permitting signal BKjpo4e 10.2 and the reclosing signal of the capacitor bank stage 4 are measured. The reactive current sensor 12 measures the change in the resultant of the reactive load current (1 cc of the power supply source and generates at its output 13 a high-speed signal, which includes the above program for changing the voltage and the throttle current and their subsequent recovery upon completion of the transient process in the reactive load in.2. The capacitor battery stage 4 remains connected to the electrical network. After the time delay at the output 14 of the reactive current sensor 12, a signal is generated about the increment of the reactive load of the power supply in the established mode, which by means of the control unit 15 and the pulse shaping unit 20 affects the speed of the switches 7 of the backup capacitor bank steps and includes them ..

 If, after the capacitor battery is connected to the reserve of the previously connected stage 4, the signal received to turn on a large reactive load 10.2 under the conditions of lack of the required power reserve of the capacitor battery, the total load current of the generator, which is in contact with the current sensor 21, becomes higher than the set value then this sensor generates an overload signal of the power supply, which in the control unit 15 blocks the inclusion of the claimed reactive load and the input of the reserve 4 of the condenser Athorne battery. At the same time, the output 18 of control unit 15 generates a signal for activating a backup power source. Due to the inclusion of the latter in the electrical network, an overload signal is output from the output of current sensor 21, forming in the control unit 15 control enable signals for applied reactive load and step 4 of the capacitor battery. The remaining operations for controlling the throttle walls and steps of the capacitor battery are repeated in a known sequence.

The technical advantages of the method of compensating static and sharply variable reactive loads are: no sinus distortion (ideal current and voltage curves of the electrical network and a compensating device in established modes; no fluctuations in the voltage of the electrical network caused by abrupt changes in the magnitude of its reactive load; simplification the main current circuit of a capacitor bank by eliminating the need to use reagents in the capacitor circuit of each stage; trosovmestimosti electrical devices electric network.

Claims (1)

Invention Formula A method for compensating static and rapidly alternating reactive load by a compensating device containing an inductive element, such as a choke and a multi-stage capacitor battery, connected via high-speed thyristor switches and an electrical network to a power source, which means that they change the voltage of the throttles by phase-adjusting its high-speed switch. and switching the steps of the capacitor bank, characterized in that, in order to improve the quality of the voltage and the electric network while simultaneously simplifying the main current circuit of the compensating device, pre-connect the choke and the largest capacitor bank stage, equal in value to the power of the throttles, to the nominal voltage of the electric network, reduce the voltage of the throttles P at the moment of switching on the reactive load of the electric network by the increment value this load, restore the nominal voltage of the throttle at the end of the transition process in the reactive load of the electrical network, form a signal increments mains reactive load in steady state, this signal is connected back-up capacitor bank stage, with switching on the reactive load of the electrical network, exceeding the power of the drossel, preliminarily generates a signal to turn on this load; they control the availability of the backup stages of the capacitor battery; in the presence of the backup power, the capacity of the capacitor battery not less than the power of the throttle includes the reactive load of the electric network and the steps of a capacitor battery, in the sum equal to the power of the throttles, regulate the voltage of the throttle in the indicated way, turn off the backup stages of the capacitor b tarei after the transition process in reaktinoy load electric network and in the absence of said reserve power capacitor of the secondary battery in signal arrival time of switch-on reactive load switching block LOAD . 257746 ki ten electrical network, increase the backup power of the capacitor battery to the desired value by disconnecting some of its connected 5 steps, while controlling the magnitude of the load current of the power supply, remove the blockage and simultaneously turn on the reactive load of the electrical network and back-up steps to a capacitor bank, regulate the voltage of the throttle in the indicated way, with an increase in the load current of the power source above the set value, caused by the transfer of a part of the connected 15 steps of the capacitor battery to the reserve, form an overload signal of the power source, block this signal by turning on the reactive load of the electrical network and 20 backup capacitor bank steps and at the same time a backup power source is commissioned. Editor L. Pchelinska Compiled by O. Nakazna Tehred L. Serdyukova Order 5034/53 Circulation 612 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 Proofreader A. Obruchar