RU2713213C1 - Automatic reactive power compensation device - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention can be used in electric engineering for reactive power compensation. Device comprises reactive power controller (1), reactive power meter (2), current and voltage sensors module of network (3), n cosine capacitors (4), first contactor (5), n switches (6), diagnostic module (7), n temperature sensors (8), n strain gauges (9), n current sensors (10), m standby cosine capacitors (11), second contactor (12), m additional switches (13), third contactor (14), n generators of test signals (15). Continuous monitoring of state of cosine capacitors in process of operation and in case of output of capacitor parameters beyond specified limits, its disconnection and rapid replacement to standby capacitors with corresponding nominal capacitance value. After disconnection of the capacitor from the network, its operative diagnostics and assessment of the possibility of further use of automatic compensation of reactive power are included in the device.EFFECT: improved quality of electric power and increased efficiency of energy saving due to increased reliability of operation.1 cl, 1 dwg

Description

The invention relates to electrical engineering, and in particular to devices that provide energy saving by automatically compensating for reactive power under variable loads.

AC electric power is characterized by a phase relationship between current and voltage. The current phase lagging behind the voltage phase occurs due to the predominance of inductive loads, while the current phase leading the voltage phase occurs due to capacitive loads. The in-phase ratio of voltage and current is possible either with purely resistive loads or with a balance of inductive and capacitive loads. A commonly used measure of the phase relationship between current and voltage is a power factor that is equal to the cosine of the phase angle between them or between active power and apparent power. The power factor is maximized at a value of unity, that is, when there is no phase shift between the current voltage in the network.

In practice, there are usually more types of inductive loads, such as electric motors, transformers connected to power lines, than capacitive ones. In a circuit having reactive loads, the power factor is less than one. Although reactive power is not consumed as such in the load, it is delivered to the power system and returned to the generator. Accordingly, power lines must pass more current than necessary to provide power to a power distribution network having reactive loads. Additional current can lead to additional real power losses caused by losses of power lines, and requires the generating device to increase power, which leads to an increase in the cost of generating electricity.

Increased load of networks with reactive current also leads to a decrease in voltage in the network, and sharp fluctuations in reactive power lead to voltage fluctuations in the network.

There are many solutions known in the art for compensating reactive power in enterprise power systems. In this case, mainly for compensation, the following means are used: shunt reactors, static thyristor compensators of the STATCOM type and compensators made using batteries of shunting cosine capacitors.

A reactive power compensation device [US Pat. RF №2335056 from 09/27/2009, Pat RF №2392717 from 06/20/2010], made on the basis of tunable shunt reactors. The disadvantage of such devices is low manufacturability large dimensions, as well as low manufacturability and low reliability.

Known devices for automatic compensation of reactive power [US Pat. US No. 8154896 B2 of 04/10/2012, US Pat. RF №2280934, H02J 3/18, dated July 27, 2006], made on the basis of controlled thyristor-reactor groups with high harmonic filters (STATCOM), in which the above disadvantages were partially eliminated. However, the disadvantage of this device is the high cost, significant consumption of active power and a high level of harmonics, the source of which is STATCOM.

The most promising networks with voltage up to 0.4 kV are devices for automatic compensation of reactive power, made on the basis of batteries of switched cosine capacitors.

The main advantages of using cosine capacitor batteries in energy saving devices are small, specific losses of the active power of cosine capacitors, the absence of mechanically moving parts during operation, ease of installation and operation, and relative ease of switching control.

Known [US Pat. RF №2229766 dated 05.27.2004, Pat. US No. 8519679 from 08.28.2013, US Pat. US No. 9335776 dated 10/05/2016] automatic reactive power compensation devices made on the basis of commutated cosine capacitor batteries having the above advantages, but they do not have high enough compensation accuracy and reliability.

The closest in technical essence of the known is a device for automatic compensation of reactive power [US Pat. US No. 7002321 of 02.21.2006] containing a reactive power regulator, a reactive power meter, the output of which is connected to the information input of the reactive power regulator, a current and voltage sensor module, the output of which is connected to the reactive power meter input, n cosine capacitors, the capacitance of which is selected from the relation Ci + 1 = 2Ci, where 1≤i≤n, the first conclusions of which are combined and connected to the neutral wire of the network, the first contactor, the first power output of which is connected to the phase wire, n switches are the first s outputs of which are connected to the second terminal of each of the n capacitors of cosine and second power terminals are coupled and connected to the second power terminal of the first contactor. The advantage of this device is the potentially high accuracy of reactive power compensation, limited only by the value of the capacitance of the lowest stage of the binary sequence. However, the known device does not have a sufficiently high reliability of operation, due to possible failures of individual cosine capacitors, both as a result of current and voltage overloads caused, including by the presence of reactive loads, and as a result of aging of capacitors.

In addition, cosine capacitors in reactive power compensation units together with inductive loads are capable of forming oscillatory circuits with parameters close to the appearance of resonance at one of the frequencies of higher harmonics. This leads to a significant increase in the current flowing through the capacitors, which, in turn, leads to overheating, which reduces the resistance of the dielectric and its breakdown. Also, when overheating, due to heating of the dielectric fluid (mineral oil or synthetic dielectric), gas formation is observed. The appearance of gas in a sealed condenser housing creates excessive pressure, which can lead to expansion of the condenser housing and even its explosion with damage to other elements of the compensation device.

Due to the increased thermal effect, the real service life of the cosine capacitor is reduced. So from technical sources it is known that at an average temperature of 40-45 degrees of a cosine capacitor, an increase in its temperature by 7 degrees reduces its expected life by half.

When a dielectric with recovery is used in capacitors, at the time of electrical breakdowns, metal spraying evaporates in their place and is removed from the breakdown site. As a result, non-metallizing non-conducting zones are formed. Despite the fact that after local breakdowns, the capacitor regains its working capacity, this ultimately leads to a decrease in its capacitance.

The technical task of the claimed device is to increase the efficiency of energy saving by improving the quality of electric energy by increasing the reliability of operation.

The problem is solved due to the fact that the device for automatic compensation of reactive power, containing a reactive power regulator, a reactive power meter, the output of which is connected to the information input of the reactive power regulator, a module of current and voltage sensors, the output of which is connected to the input of the reactive power meter, n cosine capacitors, the capacitance of which is selected from the relation Ci + 1 = 2Ci, where 1≤i≤n, the first conclusions of which are combined and connected to the neutral wire of the network, the first contact a torus, the first power terminal of which is connected to the phase wire, n switches of which the first power terminals are connected to the second terminals of each of the n cosine capacitors, and the second power terminals of which are combined and connected to the second power terminal of the first contactor, the following are introduced: a diagnostic module connected to the information bus with a reactive power regulator, n temperature sensors, n strain gauges and n current sensors, located near each of n cosine capacitors, electrical outputs that are connected to the corresponding the current information inputs of the diagnostic module, m reserve cosine capacitors, the capacitance of which is selected from the relation Cj + 1 = 2Cj, where Cm = Cn / 2, 1≤j≤m, the first conclusions of which are combined and connected to the network neutral wire, the second contactor, the first the power terminal of which is connected to the phase wire, m additional switches, the first power terminals of which are connected to the second terminals of each of the m backup cosine capacitors, and the second power terminals of which are combined and connected to the second power terminal of the second contact RA, the third contactor, the first power output of which is connected to the phase wire, n shapers of test signals, the outputs of which are connected to each of the second outputs of the corresponding n cosine capacitors, the power inputs of which are combined and connected to the second power output of the third contactor, and the control inputs of which connected to the corresponding control outputs of the diagnostic module, while the corresponding control outputs of the reactive power controller are connected to the control inputs of the first, second and third contactors, controlling inputs of n switches and controlling inputs of m additional switches.

The technical result of the claimed device lies in the fact that constant monitoring of the state of cosine capacitors is ensured during the operation of the device for automatic compensation of reactive power and, if the capacitor parameters exceed the specified limits, it is switched off and quickly replaced with reserve capacitors with the corresponding nominal capacitance value. After disconnecting the capacitor from the network, its operational diagnostics and assessment of the possibility of further use as part of the device for automatic compensation of reactive power is carried out.

The invention is illustrated by the drawing, which does not cover and, moreover, does not limit the entire scope of the claims of this technical solution, but is only illustrative materials of a particular case of execution. The relations indicated between the functional blocks are generally multichannel in order to ensure the functioning algorithm reflected in the claims and the description of the invention. The power of the functional units is provided by an uninterruptible power supply, which is not shown in the drawings.

In FIG. 1 shows a functional diagram of a device for automatic compensation of reactive power.

A device for automatic compensation of reactive power contains: a reactive power regulator 1, a reactive power meter 2, a current and voltage sensor module 3, n cosine capacitors 4, a first contactor 5, n switches 6, a diagnostic module 7, n temperature sensors 8, n load cells 9 , n current sensors 10, m redundant cosine capacitors 11, a second contactor 12, m additional switches 13, a third contactor 14, n test signal conditioners 15. Moreover, the first, second and third contactors 5, 12, 14 can be made in ide mechanical power switches, 6i switches and additional 13i switches are based on high-speed power thyristors. The reactive power controller 1, reactive power meter 2 and the diagnostic module can be made on the basis of modern digital controllers. The test signal generator 15 in its simplest form can be made in the form of an included voltage regulator, but it can include, for example, pulse test signal generators, the parameters of which are set by the diagnostic module 7.

A device for reactive power compensation works as follows. When the device is turned on, according to the signal from the reactive power meter 2, generated according to information from the voltage and current sensors 3, the regulator 1 generates a corresponding control command to turn on the first contactor 5, corresponding from the switches 6 _{i ... n} , connecting the corresponding cosine capacitors 4 _{i ... n} . When changing the load parameters in the network during operation, based on the signals from the reactive power meter 2, the reactive power controller 1 provides the formation of commands for connecting and disconnecting cosine capacitors 4i ... n, thereby compensating for reactive power in the network. Information about the cosine capacitors 4i ... n connected to the network via the information bus is constantly supplied to the diagnostic module. At the same time, from the temperature sensors 8 _{i ... n} , the load cells 9 _{i ... n} , the current sensors 10 _{i ... n} , the diagnostic module constantly receives relevant information about the parameters of each of the cosine capacitors 4 _{i ... n} . If the parameters (temperature, housing deformation, current flow) are exceeded by any of the cosine capacitors 4 _{i ... n of the} boundary values set in the diagnostic module memory 7, the corresponding signal is issued to the reactive power controller 1 via the information bus. In accordance with this signal, the reactive power controller 1 issues a command to turn off the cosine capacitor with the detected abnormal functioning, as well as commands to turn on the second contactor 12 and the corresponding switches 13 _{i ... m} . Moreover, if the capacitance of the disconnected capacitor G _i ≤C _n / 2, then one reserve cosine capacitor C _{i of} the same value as the disconnected one is turned on, and if the capacity of the disconnected capacitor Ci> C _n / 2, then the set of backup cosine capacitors is turned on, the total capacitance of which is equal to the capacitance of the disconnected cosine capacitor.

After disconnecting the cosine capacitor C _i with an emergency, a command is issued from the reactive power controller 1 to turn on the third contactor 14, while power is supplied to the test signal conditioners 15 _i . The signal from the diagnostic module 7 ensures the inclusion of the shaper of the test signals connected to the cosine capacitor C _i with the detected abnormal functioning. In accordance with commands from the module diagnostics 7 via driver control signals 15 _i and 10 _i of the current sensor automatically evaluates performance cosine capacitor C _i (e.g., checking the dielectric loss tangent, a rough estimation of capacitance change, checking for internal electrical flashovers different levels and forms voltage). Repeated verification of the parameters of the cosine capacitor may be provided after lowering the temperature of its housing to the nominal values (according to information from the temperature sensor 9 _i ). The availability of information from the load cells 8 _i allows you to timely detect the bloating of the body of the cosine capacitor C _i and prevent its explosion in the device.

In the case of positive results of the check, the corresponding information is issued from the diagnostic module 7 to the reactive power controller 1 via the information bus, according to which the possibility of further use of the tested cosine capacitor is provided. In this case, the reactive power controller 1 ensures that the previously connected redundant cosine capacitors are switched off and the tested cosine capacitor C _{i is} switched on instead of them. The second contactor 12 and the third contactor 14 are also turned off.

In the case of negative test results, the capacitor C _{i is} replaced with a similar one, followed by testing by the diagnostic module 7 and transferring the test results to the reactive power regulator 1. The combination of the cosine capacitor 4 _i , temperature sensor 8 _i , strain gauge 9 _i and current transformer 10 _i it is advisable to perform in the form of a single easily removable design, providing the possibility of its replacement without disconnecting from the network devices for automatic compensation of reactive power.

Thus, the proposed technical solution provides an improvement in the quality of electric energy and an increase in the reliability of operation due to the constant monitoring of the parameters of the cosine capacitors, which results in the automatic replacement of a failed capacitor with a reserve one. In this case, despite the fact that the number of cosine capacitors in the backup battery is half that of the main battery, equivalent capacity replacement of any of the cosine capacitors of the main battery is provided. Carrying out automatic diagnostics of cosine capacitors after they are turned off, allows you to return part of the capacitors to the main battery, which increases the overall service life of the device for automatic compensation of reactive power. Processing in the diagnostic module 7 information from the load cells 8 _i allows you to timely fix the bloating of the body of the cosine capacitor C _i and prevent its explosion in the device.

In FIG. Figure 1 shows an implementation of the invention for one of the phases of a 3-phase network; the implementation for other phases can be identical.

Claims (1)

A device for automatic compensation of reactive power, comprising a reactive power regulator, a reactive power meter, the output of which is connected to the information input of the reactive power regulator, a current and voltage sensor module, the output of which is connected to the input of the reactive power meter, n cosine capacitors, the capacitance of which is selected from the relation C _{i + 1} = 2C _i, where 1≤i <n, the first terminals are coupled and connected to the neutral wire of the network, a first contactor, a first power terminal which is connected to a core wire, n switches, the first power terminals of which are connected to the second terminals of each of the n cosine capacitors, and the second power terminals of which are combined and connected to the second power terminal of the contactor, characterized in that a diagnostic module is connected to the reactive power regulator by an information bus, n temperature sensors, n strain gauges and n current sensors located near each of n cosine capacitors, the electrical outputs of which are connected to the corresponding information inputs of muzzle diagnostics, m reserve cosine capacitors, the capacitance of which is selected from the relation C _{j + 1} = 2C _j , where C _m = C _n / 2, 1≤j <m, the first conclusions of which are combined and connected to the neutral wire of the network, the second contactor, the first power terminal of which is connected to the phase wire, m additional switches, the first power terminals of which are connected to the second terminals of each of the m backup cosine capacitors, and the second power terminals of which are combined and connected to the second power terminal of the second contactor, the third contactor, the first power the output terminal of which is connected to the phase wire, n shapers of test signals, the outputs of which are connected to each of the second outputs of the corresponding of n cosine capacitors, the power inputs of which are combined and connected to the second power output of the third contactor, and the control inputs of which are connected to the corresponding of the control outputs diagnostic module, while the corresponding control outputs of the reactive power regulator are connected to the control inputs of the first, second and third contactors, controlling the inputs of n switches and the control inputs of m additional switches.

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