JPS58103013A - Reactive power generating device - Google Patents

Abstract

PURPOSE:To simplify the constitution of the device, by flowing positive and negative currents to a cyclo converter to operate it as a variable reactor and securing the commutation voltage only with an externally provided capacitor and making its operating frequency higher than the power source frequency. CONSTITUTION:Three power rectifier/converters 31-33 consist of thyristor bridge rectifiers 311-312 and circulating current suppressing reactors 313 and 314, and rectifiers 311 and 312 are connected in anti-parallel, and rectifiers/ converters 31-33 are connected to a three-phase system power source through transformers 41-43. Capacitors 51-53 are connected to the other input terminals 71-73 of rectifier/converters 31-34, and reactors 313 and 314 are connected through transformers 41-43, power filters 21-23, and current detectors 61-63. Rectifier/converters 31-34 are used as cyclo converters, and positive and negative currents are flowed to them to operate them as variable reactors. The commutation current is secured only with externally provided capacitors 51-53, and an optional reactive power is generated with a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactive power generation device that is connected in parallel with a power source and supplies reactive power requested by a load in place of the power source. Generally, this type of reactive power generator is:
Since it is necessary to supply a fluctuating reactive power, it is required to be able to generate both lagging and leading reactive power, and to avoid generating harmonics that adversely affect the power supply as much as possible.

Conventionally, as this type of reactive power generation device, there is a device in which a reactor is connected in series to a thyristor conversion device, and the phase of the thyristor is controlled so that it functions as a variable reactor.

This known method can generate lagging reactive power by controlling the phase of the Sirisk converter, but has the disadvantage that it cannot generate leading reactive power. A capacitor is connected. Therefore, this method has the disadvantage that not only the capacitance of the phase advance capacitor becomes large, but also that harmonic currents associated with phase control of the reactor flow into the power supply.

Recently, as one of the ideal conversion devices, a high-frequency link-type stationary converter is developed, in which the input terminal sides of two converters (converters) are connected to each other, and a high-frequency voltage supply device is connected to the input terminal position. A voltage converter is known (if necessary, see Japanese Patent Publication No. 53-25930, for example), and as an example of its application, a reactive power generator in which only a high-frequency voltage supply device is connected to the input terminal of one converter is known. Devices are also known. Possible high-frequency voltage supply devices used in this case include a rotating synchronous generator, a synchronous phase modifier, and an L-C tank circuit, but the former has the disadvantage of requiring the use of a rotating machine. It has been pointed out that even in the latter case, which has the feature of being a static type, a capacitor with a particularly large capacity must be provided in order to maintain a constant frequency regardless of increases or decreases in reactive power. Regarding the points, if necessary, IEE Transactions IA,
VOL, IA-15, No 5.1979, P521~
See 531. ).

This invention was made in view of the above, and it is possible to arbitrarily generate lagging or leading reactive power, suppress the generation of harmonics as much as possible, and create a large-capacity, economical, and compact reactive power. The purpose of the present invention is to provide a power generation device.

According to the present invention, the above object is to form a commutated voltage source by connecting a capacitor to the input side of a separately excited converter whose output side is connected to a grid power supply, and to control the phase of the converter. This is achieved by changing the magnitude of the flowing circulating current to supply leading or lagging reactive power from the converter to the grid power supply side. In other words, a conventional separately excited converter has a simple configuration of connecting the output in reverse and connecting a capacitor to the input side, but a completely new type of inverter with a different idea from the conventional one can be used. A power generation device is provided.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a main circuit configuration diagram showing an embodiment of the present invention.

In the figure, 31 to 33 are forward converter main circuits consisting of inverse converters, 41 to 43 are transformers, 51 to 53 are capacitors, 61 to 63 are current detectors, and 11 to 13 (U-W) are Three-phase grid current terminals or converter output terminals, 71-7
3 is an input terminal of the converter, and 21 to 23 are power filter reactors. The converter main circuit 31 consists of thyristor bridge rectifiers 311 and 312, which are connected in antiparallel to each other. The same applies to the main circuits 32 and 33, and therefore, these main circuits 31 to 33 constitute a three-phase cycloconverter. In addition, 313.
314 is a circulating current suppression reactor.

As is clear from the figure, this cycloconverter (
Hereinafter, it will also simply be referred to as a converter or converter. )'s normal input terminal and output terminal are interchanged here, and the normal output terminal is the circulating current suppressing reactor 313, 314.
..., are terminated by transformers 41-43 and power filter reactors 21-23, while normal input terminals are terminated only by capacitors 51-53. Hereinafter, "input" and "output" will be referred to as a cycloconverter with the capacitor terminal side as the input side.

Therefore, 71 to 73 are input terminals, and 11 to 13 are output terminals.

With this configuration, the cycloconverter performs separately excited commutation operation using the voltages of the capacitors 51 to 53 as the commutating voltage, while the active power due to circuit loss is shunted from the system power supply side 11 to 13. It can be used to generate reactive power. Finally, in this invention, the commutating voltage sources are the capacitors 51 to 53 and the converters themselves 31 to 33 having the ability to adjust reactive current,
This eliminates the need for a conventional independent voltage supply source, that is, an oscillation circuit consisting of a synchronous phase modifier (or generator) and an LC. In other words, the converters 31 to 33 have circulating current suppressing reactors 313 inside them.
．． 314..., positive group converters 311...,
Since the magnitude of the circulating current can be adjusted by changing the control angle of the negative group converters 312, this corresponds to the fact that the equivalent inductance Lc seen from the input terminal of the cycloconverter is variable. therefore,
The capacitors 51 to 53 and the converters 31 to 33 operate as if they form a tank circuit, and the inductance of the tank circuit is made variable by the phase control of the cycloconverter. You get it.

Here, how the input frequency is maintained at a constant value, that is, how the control angle is determined and stable operation is performed will be explained with reference to FIGS. 2A and 2B. Note that Figures 2A and 2B are waveform diagrams showing the relationship between the ignition pulse of the positive group converter and the negative group converter, and the output voltage.

Now, connect the output terminal of the cycloconverter (terminal 1 in Figure 1)
1 to 13) to the input terminals (terminals 71 to 7 in Figure 1).
It is assumed that the frequency is very low compared to the frequency of 3). Then, during this period, as shown in FIGS. 2A and 2B (a), it can be considered that the positive group converter and the negative group converter are given firing pulses at equal intervals T. In this state (ideal state), the relationship between the control angle αp of the positive group converter and the control angle αN of the negative group converter is αp
+αN=180° (=π). In this state, if the input frequency drops for some reason as shown by the dotted line in FIGS. 2A and 2B (b), this is due to the control angle α9. This is equivalent to each αN being smaller than the illustrated size. However,
Since π/2 × αp × π, 0〈αN〈π/2, the output voltage of the positive group converter decreases as the control angles αp and αN decrease, while the output voltage of the negative group converter increases,
Circulating current increases. This corresponds to a decrease in the apparent equivalent inductance L0 seen from the input side, and the resonant frequency of the tank (parallel resonance) circuit consisting of the capacitor and equivalent inductance increases, returning to the original steady state. I try to do that. On the other hand, when the input frequency increases, contrary to the above, an attempt is made to suppress this increase by a completely opposite effect, so that the input frequency is always maintained at a predetermined state in any case. In an actual cycloconverter, the firing pulse interval periodically expands and contracts depending on the output frequency and output voltage, but the control angles α and α are adjusted so that the circulating current does not change. By keeping the inductance Lc in a predetermined relationship (αp+αN=180°), the inductance Lc remains fixed and the input frequency remains constant. In FIGS. 2A and 2B, the thin solid line waveform represents the input voltage of the converter, and the thick solid line represents the output voltage waveform.

One of the things that is particularly important here is that the converter itself has the ability to change the input reactive current. It is possible to adjust the input reactive current by asymmetrically controlling 311, 312, and so on, and the equivalent inductance Lc can be made variable by controlling them.

Furthermore, another important point is that the converter input frequency can be arbitrarily determined by an external command, and the equivalent (variable) inductance is adjusted according to the input frequency determined in this way or the gate pulse interval determined by the frequency. L. is determined automatically, that is, it can be made into other systems. Therefore, it is possible to make the frequency of the high-frequency voltage on the input side higher than the wave number on the output side and the stain source side, and as a result, the current on the power supply side can be made closer to a sine wave, so the harmonics taken from the power supply side can be made higher. The wave current component is reduced. This also brings about the advantage that the capacitance of an externally arranged input side capacitor can be reduced.

In this way, a voltage with a frequency determined by the ignition pulse interval is established on the input side, and its operation can therefore be considered in the same way as a separately excited cycloconverter. In other words, by controlling the phase of the cycloconverter, if the voltage at its output terminal is in phase with the AC grid voltage, and if the value is set higher, a delayed reactive current will be supplied to the grid. The device according to the invention allows lead current to be taken from the grid side. On the other hand, if the voltage at the output terminal is in phase with the AC grid voltage and its value is made smaller, a leading current will be supplied to the grid.Looking at it from a different perspective, the device according to the present invention will take the lagging current from the grid. be able to.

In other words, a normal cycloconverter performs commutation using the input AC voltage, but it uses separately excited commutation, and its input reactive power is only the delay component, whereas the output side has the output voltage and current. By changing the magnitude of the output power factor, in other words, it has the property of being able to handle both leading and lagging reactive power. Therefore, this invention focuses on the characteristics of such a cycloconverter, replaces the normal input end and output end, and controls the output voltage and current of a normal cycloconverter on the AC power supply side. It is possible to generate reactive power for both leading and lagging values of .

FIG. 3 is a block diagram showing a control circuit for each of the rectifiers 31 to 33 in FIG. 1.

In the figure, reference numerals 85, 86, and 87 are control circuits corresponding to the rectifiers 31, 32, and 33 in FIG.
．． 87 is also constructed in exactly the same way. The control circuit 85 includes a multiplier 851, an adder 852, a subtracter 853, a regulator 854, a gate pulse generation circuit 855, and the like. Further, 81 is a reactive power setting device, 82 is a phase shift circuit, 83 is a frequency setting device, 84 is a sine wave generator, 11 to 13 are output terminals shown in FIG.
U"" IW is the actual current value detected by the current detectors 61 to 63 in FIG.

In the reactive power setter 81, the magnitude of the reactive current is converted into a DC voltage value and set. It is assumed that an advance amount is set on the ■ side, and a delay amount is set on the e side. On the other hand, the instantaneous value of the stain pressure is detected from the output terminals 11 to 13, and based on this, the phase shift circuit 82 calculates an AC voltage waveform whose phase is advanced by 90et from each phase voltage (this creates a reactive component). ) is input to the multiplier 851 of each phase. In multiplier 851, direct 7
, The reactive power setting value converted into a current value is multiplied by the output from the phase shift circuit 82, and the current waveform (reactive current portion) of each phase is determined according to the ■ and O outputs of the setting device 81. input section of the current regulator 854 for each phase,
That is, it is given to the subtracter 853 .

The actual value I[J - IW of each phase current waveform is fed back from the current detectors 61 to 63 in FIG. Adjustment operations are performed so that the set values match. The output of the current regulator 854 for each phase is given as a control input to the gate pulse generator 855 for each phase. On the other hand, the tact (synchronization) signal that determines the frequency on the converter input side of the gate pulse generator 855... has a phase shift of 120 eL according to the frequency set by the completely independent frequency setter 83. The output from a sine wave generator 84 that produces a sine wave is used. That is,
Conventionally, a tact (synchronization) signal was required to synchronize with the grid power supply, but in this invention, the signal from the frequency setter 83, which is provided independently of the grid power supply, is used as the tact signal. It is. Gate pulse generator 855... Takt signal and current regulator 854...
In addition, so-called cosine wave control is performed in conjunction with the control output from . The output is given as a gate pulse to each phase converter 31 to 33 in FIG. 1 to perform phase control.

Until now, this invention has been explained as an ideal reactive power generation device with no loss, but in reality it is
There are losses in the transformer or converter, etc. but,
Stable operation can be maintained by providing a commensurate amount of these losses as an effective amount from the alternating current side.

In the embodiment, the transformers 41 to 43 are connected to the output side, but it is also possible to connect them between the input terminals 71 to 73 and the capacitors 51 to 53, in which case the input As a result of the increased side frequency, there is an advantage that the transformer can be made smaller.

In addition, in FIG. 3, by adding a harmonic signal to the adder 852, it is possible to compensate for a disturbance harmonic having a phase different from this by 180 eL.

In this case, since the input frequency of the reactive power generator is high,
Compensation resolution on the output side, that is, on the grid side, is increased. Furthermore, by providing the adder 852 with a current setting that is in phase with the system voltage, active power can be taken out from the input terminals 71 to 73.

As described above, according to the present invention, since positive and negative currents are passed through the cycloconverter to cause it to operate as a variable reactor, commutation voltage of the cycloconverter can be ensured with only an externally placed capacitor, and its operation Since the frequency is regulated by a different system, it can be set higher than the power supply frequency, and therefore the capacity of the externally disposed capacitor can be reduced. In addition, the new idea of replacing the normal input/output terminals and making effective use of the characteristics of the cycloconverter has made it possible to generate delayed and advanced reactive power arbitrarily, so the configuration is simple and not foolproof. This has the effect of increasing capacity. Furthermore, since the converter according to the present invention operates with separate excitation, there is an advantage that a high-speed thyristor element required for a self-excited inverter is not required, and a large-capacity thyristor element for general power use can be used.

It should be added that the effectiveness of this invention has been confirmed through experiments called modifications.

[Brief explanation of the drawing]

FIG. 1 is a main circuit configuration diagram showing an embodiment of the present invention, and FIG.
, 2B are waveform diagrams showing the ignition pulses given to the positive group and negative group converters, respectively, and their output voltage waveforms,
FIG. 3 is a block diagram showing a control circuit corresponding to the main circuit of FIG. 1. Description of symbols 11-13... Output terminal, 21-23... Power filter reactor, 31-33... Order, reverse rectifier, 41
~43...Transformer, 51~53...Capacitor, 6
1-63... Current detector, 71-73... Input terminal, 81... Reactive power setting device, 82... Phase shift circuit, 83... Frequency setting device, 84... Sine wave Generator, 85... Control circuit, 851... Multiplier, 852...
...Adder, 853...Subtractor, 854...Current regulator, 855...Gate pulse generator, αp, αN・
...Phase control angle agent for positive and negative group converters Patent attorney Akio Namiki Agent Patent attorney Kiyoshi Matsuzaki Figure 1 Figure 2A Figure 28v 82-

Claims (1)

[Claims] 1) A capacitor is connected to the other side of a separately excited converter having one terminal connected to the grid power supply and equipped with forward and inverse converters, and the capacitor is used to control the conversion of each of the converters. By forming a current voltage source, controlling the phase of each control angle of the forward and inverse converters to satisfy a predetermined relationship, and adjusting the magnitude of the circulating current flowing to the converter, the system power source can be removed from the converter. A reactive power generation device characterized in that it supplies lagging or leading reactive power to the side. 2. In the reactive power generation device according to claim 1, ignition pulses of a desired frequency are applied to the forward/inverse converter in a predetermined order from a root generator provided separately from the grid power supply. 1. A reactive power generator characterized by reducing harmonic components taken from a grid power source side.