SU758373A1 - Device for control of reactive power source - Google Patents

Description

The invention relates to the field of electrical engineering and is intended to improve the quality of electricity in electrical networks equipped with a regulated source of reactive power.

It is known that one of the most important indicators of power quality is voltage stability.

In the networks of industrial enterprises, the voltage does not remain constant, which adversely affects the work of consumers and is the cause of economic damage.

Voltage instability depending on the rate of its change is characterized by its deviations and fluctuations.

'It is known that rapid changes in voltage in the network are more harmful to consumers than slow ones. This is especially true of such common loads as lighting, radio and electronic equipment.

To improve the quality of electricity, regulated sources of reactive power are used, which are;

2

These simultaneously serve to increase the power factor of the load node.

A device for controlling an adjustable source of reactive power is known that is connected to the power buses of a group of consumers operating in a fast and often changing load mode (as a result, the bus voltage does not remain constant, but changes depending on the load mode of the consumers), which contains a summation unit connected to the control input of the source of reactive power, to the inputs of the summation unit are connected the outputs of the sensors of reactive current installed on the feeders of the consumers, and the sensor active the current of the feeder connecting the transformer to the tires £ ΐ],

In the summation unit, the sensor signals are summed, with the result that the resulting input of the reactive power source receives the resulting signal, under the action of which the reactive power source operates in the mode of tracking consumer currents so that voltage changes caused by load changes of consumers are reduced.

3

758373

four

"i.e., power quality rises."

Thus, the known device provides control of an adjustable source of reactive Power, depending on the mode of other consumers, and the greater the load of these consumers, the greater the load and, therefore, the heating of the reactive power source itself. Under adverse conditions, the heating of a reactive power source may exceed the normal value, which is dangerous due to the shortened service life of this source or even its complete failure.

Thus, the disadvantage of the prototype is that the control of the source of reactive power is carried out without taking into account its heating.

The aim of the invention is to limit the heating of the regulated source of reactive power and improving the quality of electricity and reliability in operation:

This goal is achieved due to the fact that the device for controlling an adjustable source of reactive power connected to the power buses of a group of consumers with an alternating load, containing sensors for the reactive component of consumer currents and a block for summing the output signals of these sensors, the output of which is connected to the input of the source of reactive power, is additionally equipped the unit for determining the heating of the source and the disconnecting contact and the inertial element, and its output is connected to the output of the unit In this case, the output of the source heat detection unit is connected to the inertial event, the output of which is connected to the auxiliary input of the source of reactive power, and the polarity of the output signal of the inertial link is opposite to the polarity of the output signal of the summation unit.

The drawing shows a structural diagram of the proposed device.

The power transformer (T) is connected to the power system (ES),,

connected to power tires (W).

The power bus is connected to η consumption. Biteles operating in fast mode and frequently changing load, as a result of which the voltage on the tires does not remain constant, but changes depending on changes in the load mode of consumers. To improve the quality of electric power, a regulated reactive power source (RRM) is connected to the tires, which also improves the power factor of the load unit as a whole. To the control input '(RRM) is connected the block <summation (BS) of the output signals of the reactive current sensor (DRT),

which are installed on consumer feeders. In addition, the device contains a block for determining the heating of a source of reactive power (BON), an inertial link (IZ).

FROM connected to the output of the BS through the closing contact BON, and the output FROM is connected to the additional control input of the source of reactive power so that the polarity of the output signal of the inertial link is opposite to the polarity of the output signal of the summation unit.

The inertial link, as is known, has a transfer function

whereby the output voltage of the inertia link is related to its input voltage as follows

ή + ρτ '

where P is the operator's sign;

T - time constant, value

which depends on the selected parameters of the inertial element.

The inertial link described by the above transfer function has the following property.

In the steady state, its output signal is equal to the input, and when. by changing the input signal, the output signal changes more slowly than the input signal and fits smoothly to its steady-state value equal to the steady-state value of the input signal.

In particular, when the input signal changes abruptly, the output signal changes exponentially

^ Out ' ^e )>

• where e is the base of natural logarithms,

ί - current time value.

As an inertial link, for example, an operational amplifier can be used, in particular, a unified block regulation system amplifier (UBSS), at the input of which a resistor is connected, and a resistor and a capacitor are connected in parallel in the feedback circuit.

The BON block is designed to determine the heating of a reactive power source. In the simplest case, it is a contact-supplied thermometer embedded in the part of the reactive power source whose temperature should be monitored. There may be several such thermometers - according to the number of controlled points. In more complex cases, which have also become widespread in industrial plants, the heat detection unit is performed in the form of thermistors or thermistors connected to

five

758373

6

electronic potentiometer (bridge), equipped with output contacts, which operate when the measured temperature reaches the specified value.

The device works as follows.

/ If the heating of the reactive power source has not reached a pre-selected value, then the contact of the BON block is in the open state, and therefore the input signal of the inertial FROM link is absent and its output signal is zero. In this case, a control signal arrives at the input of the reactive power source only from the output of the BS summation unit. Under the action of this signal, the source of reactive power RIRM works in the mode of tracking the total sum of the reactive currents of consumers and ensures the stabilization of the voltage on the tires, i.e. maintains good power quality. In addition, RIRM also maintains a high power factor of the load node at each moment of time.

If, as a result of an unfavorable combination of values and durations of reactive loads of consumers or unfavorable cooling conditions, the source of reactive power RIRM is heated to a preselected (close to dangerous) temperature, the closed BON contact is activated, and thus the IZ input is connected to the BS output. With a constant value of the sum of reactive currents η consumers and, therefore, a constant value of the output signal of the BS, the output signals of the OF and the BS, in the steady state, mutually compensate each other and the source of reactive power will go into idle mode, which will reduce losses in it, and therefore, its heating temperature will begin to decrease.

In this case, the power factor of the load node will deteriorate, but the voltage on the tires will remain stable until the sum of the reactive currents of the consumers remains unchanged.

If, however, the change in the mode of operation of consumers changes the sum of their reactive currents, then the output signal of the BS will change, whereas the output signal of the FM will change more slowly.

As a result, at the first moment of time, the equilibrium of output signals of BS and IZ will be disturbed, and under the action of the difference of these signals, RIRM will change its mode accordingly, which will reduce the voltage change on the tires, which occurs due to a change in the mode of operation of consumers. However, the output signal of the inertial link will not remain constant, but will smoothly change, approaching in magnitude to the value of the output signal of the BS.

In this case, the difference between the output signals from the BS and the BS at the control input of the RIRM will smoothly change in the direction of reduction, and the reactive current of this source will decrease accordingly. After a certain period of time, depending on the predetermined time constant IZ, the equilibrium of the signals at the control input of the reactive power source will again be restored and it will return to idle mode, which will reduce losses in it and decrease heating.

After reducing the heat to the set value, the BON contact will open, and the source of reactive power will go into tracking mode for the sum of the reactive currents of the consumers and will ensure both the voltage stability on the tires and the high power factor of the load node.

The useful effect of the application of the proposed device is that when the reactive power source is heated to a predetermined temperature, it can be left on, and while cooling down, it will continue to reduce the rapid changes (fluctuations) in the voltage caused by changes in the reactive power of consumers.

This improves the quality of electricity and increases the reliability of all current nodes of the load.

Claims (1)

Claim A device for controlling an adjustable reactive power source connected to the power buses of a consumer group with a rapidly alternating load, containing sensors for the reactive component of consumer currents and a block for summing the output signals of these sensors, the output of which is connected to the input of the reactive power source, characterized in that electricity and improve the reliability of consumers, it is additionally equipped with a unit for determining the heating of the source with the opening contact, and insulating element, wherein the input determination unit heat source connected to the output summing unit, an output determining unit • heating source is connected to the inertial element, whose output is connected to the auxiliary input source of reactive 758373 power, and the polarity of the output signal of the inertial Even is opposite to the polarity of the output ’signal of the summation block.