JP5977191B2 - Harmonic suppression control circuit, harmonic suppression device, and harmonic suppression system - Google Patents

Description

  The present invention relates to a harmonic suppression control circuit, a harmonic suppression device, and a harmonic suppression system used in a harmonic suppression device for suppressing voltage flicker.

  On the load side of the AC system, for example, due to steep current fluctuations caused by equipment such as an arc furnace or welder in the load system, it causes visual discomfort such as flickering of lighting, and malfunction of equipment connected to the AC system Therefore, there is a demand for a technique for suppressing the flicker.

  In the active filter and voltage flicker suppression control method, voltage detection means for detecting the installation point voltage, which is the voltage at the connection point with the distribution line, and a compensation current command value are generated from the installation point voltage detected by the voltage detection means It is known to have control means for controlling and current control means for controlling the compensation current in accordance with the compensation current command value.

JP 2008-48520 A

  The technique described above is a technique for suppressing flicker in the distribution system, and there is a limit in suppressing flicker in individual load systems.

  FIG. 9 is a block diagram showing a configuration of a conventional reactive power compensator. As shown in FIG. 9, for example, in the load system 24 subject to flicker suppression, harmonic components that flow out to the load system 24 by installing the harmonic filter 28 for each order (for example, second order, third order, etc.) In addition, a reactive power compensator 110 (SVC: Static Var Compensator) was installed to suppress voltage flicker.

A reactive power compensator 110 shown in FIG. 9 has a plurality of self-extinguishing switching elements, and a self-excited converter 11 connected to a load system 24 so as to be autonomously controllable from an AC system. And a reactive power control circuit 101 that controls the device 11. Furthermore, the reactive power control circuit 101 includes a current command calculation unit 102 that calculates a current command value i _F ^* that compensates for a fluctuation component of the reactive power flowing through the load 25, and the current command value i _F ^* and the detected load system. The converter control unit 103 controls the compensation current i _F supplied from the self-excited converter 11 in synchronization with the 24 load voltage VT.

In addition to this, a current transformer 26 for detecting the load current i _L flowing through the load 25, a voltage transformer 27 for detecting the load voltage VT of the load system 24, and the like are installed. The power receiving system 22 receives power from the system power source 21, and the load system 24 is connected to the power receiving system 22 via a power receiving transformer 23.

  However, in the load system 24, a parallel resonant circuit is configured due to the system impedance 20 including the power receiving transformer 23 (referred to as system inductance Ls) and the harmonic filter 28, and a non-integer order harmonic current is generated from the power receiving side. As a result, the voltage flicker of the load system 24 increases.

The conventional reactive power compensator 110 can suppress the voltage flicker caused by the load 25 by detecting the load current i _L , but the harmonic filter connected to the load system 24 as described above. Thus, the voltage flicker generated by the parallel resonance due to 28 could not be suppressed.

  Problems to be solved by the present invention include a harmonic suppression control circuit, a harmonic suppression device, and a harmonic that can suppress voltage flicker caused by the load and the harmonic filter in a load system including the harmonic filter. It is to provide a suppression system.

In order to solve the above problems, a harmonic suppression control circuit according to the present invention is mounted on a harmonic suppression apparatus that includes a self-excited converter and suppresses harmonics in a load system to which a load and a harmonic filter are connected. A harmonic transformer control circuit that receives a detection signal from a current transformer that detects a load current flowing through the load and a voltage transformer that detects a voltage of the load system. The harmonic suppression control circuit, the detection signal from the voltage of the load system and the high-pass filter that passed by extracting harmonic components, predetermined gain to the voltage passed is extracted from the high pass filter And a second current that compensates for a fluctuation component of the reactive power flowing through the load based on a voltage of the load system and a detection signal of the load current. A current command calculation unit that calculates and outputs a command value, and adds the first current command value and the second current command value to obtain a compensation current command value, and the self-excited type based on the compensation current command value And a converter control unit that controls the current of the converter.

Moreover, in order to solve the said subject, the harmonic suppression apparatus which concerns on this invention is a harmonic suppression apparatus which suppresses the harmonic in the load system | strain to which the load and the harmonic filter were connected. The harmonic suppression device includes a current transformer that detects a load current flowing through the load, a voltage transformer that detects a voltage of the load system, a self-excited converter connected to the load system, and the detected a high-pass filter that is passed to extract a harmonic component from the voltage of the load system, and calculates a first current command value by multiplying a predetermined gain to the voltage passed is extracted from the high pass filter A gain adjustment unit that outputs, a current command calculation unit that calculates and outputs a second current command value that compensates for the fluctuation component of the reactive power flowing through the load based on the detected voltage of the load system and the load current; A converter controller that adds the first current command value and the second current command value to obtain a compensation current command value, and controls the current of the self-excited converter based on the compensation current command value; It is characterized by comprising .

  In order to solve the above-mentioned problem, one harmonic suppression system according to the present invention is installed in a load system to which a load and a harmonic filter are connected, and is a self-excited reactive power that suppresses harmonics caused by the load. It is a harmonic suppression system provided with the harmonic suppression apparatus which suppresses the harmonic resulting from a compensation apparatus and the said harmonic filter. The harmonic suppression system further includes a current transformer that detects a load current flowing through the load, and a voltage transformer that detects a voltage of the load system. The self-excited reactive power compensator includes a first self-excited converter connected to the load system, and a fluctuation component of reactive power flowing through the load based on the detected voltage of the load system and the load current. A control circuit that calculates a first current command value to be compensated and controls a current of the first self-excited converter based on the first current command value, wherein the harmonic suppression device is included in the load system. A second self-excited converter connected; a high-pass filter for extracting a harmonic component from the detected voltage of the load system; and a voltage obtained by multiplying the voltage extracted from the high-pass filter by a predetermined gain. A gain adjustment unit that calculates and outputs a two-current command value, and a converter control unit that controls a current of the second self-excited converter based on the second current command value.

  In order to solve the above problem, another harmonic suppression system according to the present invention is installed in a load system to which a load and a harmonic filter are connected, and suppresses a fluctuation component of reactive power caused by the load. A harmonic suppression system including a separately excited reactive power compensator and a harmonic suppression device that suppresses harmonics caused by the harmonic filter. The harmonic suppression system further includes a current transformer that detects a load current flowing through the load, and a voltage transformer that detects a voltage of the load system. The separately excited reactive power compensator includes a plurality of power semiconductor elements having no self-extinguishing capability, a first separately excited converter connected to the load system, the detected voltage of the load system, and the A control circuit for calculating a first current command value for compensating for a reactive power fluctuation component flowing through the load based on a load current, and for phase-controlling the first separately excited converter based on the first current command value; The harmonic suppression device includes a second self-excited converter connected to the load system, a high-pass filter that extracts a harmonic component from the detected voltage of the load system, and the high-frequency band A gain adjustment unit that calculates and outputs a second current command value by multiplying a voltage extracted from the pass filter by a predetermined gain, and a current of the second self-excited converter based on the second current command value. A converter control unit to control, Features that obtain.

  According to the harmonic suppression control circuit, the harmonic suppression device, and the harmonic suppression system according to the present invention, voltage flicker caused by the load and the harmonic filter can be suppressed in the load system including the harmonic filter. .

The block diagram which shows the structure of 1st Embodiment of the harmonic suppression apparatus which concerns on this invention. The figure which shows an example of a structure of the self-excited converter of FIG. The figure which shows an example of the frequency characteristic at the time of the harmonic suppression apparatus of FIG. 1 being installed in the load system. The figure which shows the equivalent circuit of the load system | strain shown in FIG. The block diagram which shows the structure of 2nd Embodiment of the harmonic suppression apparatus which concerns on this invention. The figure which shows an example of a structure of the existing TCR of FIG. The block diagram which shows the structure of 3rd Embodiment of the harmonic suppression apparatus which concerns on this invention. The figure which shows an example of a structure of the existing SVC of FIG. The block diagram which shows the structure of the conventional reactive power compensation apparatus.

  Hereinafter, a harmonic suppression control circuit, a harmonic suppression device, and a harmonic suppression system according to an embodiment of the present invention will be specifically described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted. Each of the following embodiments described here will be described by taking an example of a load system to which a harmonic filter is connected.

[First Embodiment]
FIG. 1 is a block diagram showing the configuration of the first embodiment of the harmonic suppression device according to the present invention. FIG. 2 is a diagram showing an example of the configuration of the self-excited converter of FIG. 3 is a diagram showing an example of frequency characteristics when the harmonic suppression device of FIG. 1 is installed in a load system, and FIG. 4 is a diagram showing an equivalent circuit of the load system shown in FIG. Hereinafter, the harmonic suppression device of the first embodiment will be described with reference to FIGS. 1 to 4.

  The power receiving system 22 receives power from the system power supply 21. The load system 24 is connected to the power receiving system 22 via the power receiving transformer 23. In addition, it is set as the system | strain impedance 20 including the receiving transformer 23, and system | strain inductance is set to Ls.

  A load 25 is connected to the load system 24. In addition, a harmonic filter 28 is connected to the load system 24 in order to suppress harmonic components with respect to the power supply frequency (fundamental wave frequency) flowing out to the power receiving system 22.

The harmonic filter 28 has a filter characteristic that suppresses the order of a predetermined harmonic. The harmonic filter 28 includes, for example, a capacitor C _F1 and an inductance L _F1 connected in series. The order of the predetermined harmonic is, for example, second order. In this case, the harmonic current i _F1 shown in FIG. 1 includes a secondary component of the fundamental frequency (referred to as f ₀ ).

  Further, the harmonic suppression device 10 a is connected to the load system 24 in order to compensate for the reactive power of the load system 24.

Load system current is to flow from the power receiving line 22 to the load system 24 includes a load current i _L of the load 25 in load line current is. The current transformer 26 detects a load current i _L flowing through this load. The voltage transformer 27 detects the voltage of the load system 24 (load voltage VT). The detected load current i _L and load voltage VT are input to the harmonic suppression device 10a.

As shown in FIG. 1, the harmonic suppression device 10 a includes a harmonic suppression control circuit 1 a and a self-excited converter 11, and generates reactive power in the load system 24 based on the load current i _L and the load voltage VT. To compensate. The harmonic suppression device 10a may include a current transformer 26 and a voltage transformer 27. Hereinafter, the harmonic suppression control circuit 1a will be mainly described.

The harmonic suppression control circuit 1a detects the harmonic component contained in the load voltage VT based on the load voltage VT, and suppresses the voltage flicker caused by the harmonic filter 28 so as to suppress the current of the self-excited converter 11. To control. Furthermore, harmonic suppression control circuit 1a based on the load voltage VT and the load current i _L, so as to suppress a voltage flicker caused by the load 25, to control the current of self-commutated converter 11.

Here, the voltage flicker caused by the harmonic filter 28 refers to voltage flicker generated by parallel resonance caused by the system impedance 20 (system inductance Ls) and the harmonic filter 28. Further, a voltage flicker caused by due to the load 25 refers to voltage flicker caused by variation components included in the load current i _L (including harmonic components).

  For this purpose, the harmonic suppression control circuit 1a includes a converter control unit 2a, an HPF unit 3, a gain adjustment unit 4, and a current command calculation unit 5, as shown in FIG.

The HPF unit 3 has a high-pass filter, and the high-pass filter has a predetermined HPF constant. The HPF unit 3 extracts a harmonic component from the load voltage VT and outputs it to the gain adjusting unit 4. As the HPF constant, for example, it has a low cut-off frequency that is higher than the fundamental frequency f _{0 and} lower than the parallel resonance frequency f ₁ caused by the harmonic filter 28.

Note that a band pass filter may be used for the HPF unit 3. In this case, in addition to the above-described low-frequency cutoff frequency, a high-frequency cutoff frequency is determined. For example, high-cut frequency, when a plurality of the harmonic filter is connected to a load system 24, defined in a frequency higher than the parallel resonance frequency f ₁ caused by the highest order harmonic filter. Alternatively, a plurality of bandpass filters having predetermined frequency passbands may be provided, and the gain adjustment unit 4 may be provided for each output of the bandpass filter to determine the gain K.

Gain adjusting section 4, it is multiplied by a prescribed gain K the extracted voltage harmonic component from the load voltage VT, and outputs to converter control unit 2a as a first current command value i _H ^*.

As described above, in order to suppress voltage flicker caused by the harmonic filter 28, the HPF constant of the HPF unit 3 and the gain K of the gain adjusting unit 4 are determined. Although details will be described later, the current amplification factor | is / i _L | in the vicinity of the parallel resonance point indicated by the solid line is suppressed, for example, as the frequency characteristic indicated by the broken line in FIG.

Current calculation unit 5 inputs the load voltage VT detected from the load system 24 and the load current i _L. The current command calculation unit 5 calculates a second current command value i _F ^* based on the load voltage VT and the load current i _L. This second current command value i _F ^* is calculated by a known technique for suppressing voltage flicker caused by the load 25.

Before being input to the converter control unit 2a, a first current command value i _H ^* and a second current command value i _F ^* and are added by the adder, the result of the addition compensation current command value i _C ^* Is input to the converter controller 2a.

Converter control unit 2a controls self-excited converter 11 based on compensation current command value i _C ^* and detected load voltage VT. That is, the converter control unit 2a controls the current of the self-excited converter 11 so that the compensation current command value i _C ^* is obtained, and synchronizes with the voltage phase of the system voltage by the detected load voltage VT. PWM control of the converter. As a result, the compensation current i _C is output from the self-excited converter 11.

  As shown in FIG. 2, the self-excited converter 11 includes a self-extinguishing switching element 31 such as an IGBT (Insulated Gate Bipolar Transistor) and an IEGT (Injection Enhanced Gate Transistor), a reactor 32, and a smoothing capacitor 33. Is done.

The self-excited converter 11 performs PWM control so as to follow the compensation current command value i _C ^* calculated by the harmonic suppression control circuit 1 a described above, and outputs the compensation current i _C to the load system 24. Thereby, the self-excited converter 11 can suppress the voltage flicker caused by the harmonic filter 28 and can also suppress the voltage flicker caused by the load 25.

  The effect of the above configuration will be described with reference to FIG. In FIG. 3, the frequency characteristic in the load system | strain 24 provided with the harmonic suppression apparatus 10a is shown in comparison with a prior art example. In particular, the solid line is an example of the frequency characteristic when the conventional reactive power compensator shown for comparison is installed in the load system, and the broken line is the case where the harmonic suppression device 10a of FIG. 1 is installed in the load system 24. It is an example of the frequency characteristic.

In FIG. 3, the horizontal axis represents frequency (Hz) and the vertical axis represents current amplification factor | is / i _L | (dB). Further, the fundamental frequency f ₀ of the system power supply 21 _{, the} parallel resonance frequency f ₁ , and the series resonance frequency f ₂ of the harmonic filter 28 are set. Moreover, the load system 24 shown in FIG. 1 is expressed by, for example, an equivalent circuit shown in FIG. 4 approximately. Note that the damping resistor Rd shown in FIG. 4 is equivalent to the harmonic suppression device 10a.

Here, for example, based on the equivalent circuit shown in FIG. 4, for the parallel resonance caused by the system inductance Ls and the harmonic filter 28, the parallel resonance frequency f ₁ can be obtained as in Expression (1). Also, the series resonance of the harmonic filter 28, the series resonance frequency f ₂ can be obtained as Equation (2).

f ₁ = 1 / 2π / √ {(L _S + L _F1 ) · C _F1 } (Formula 1)
f ₂ = 1 / 2π / √ (L _F1 · C _F1 ) (Formula 2)
Note that the capacitor value C _F1 and the inductance value L _F1 of the harmonic filter 28 are used, and the resistance of the harmonic filter 28 is not considered here for convenience.

  In the converter control unit 2 a, the HPF constant of the HPF unit 3 and the gain K of the gain adjustment unit 4 shown in FIG. 1 are determined in order to suppress voltage flicker caused by the harmonic filter 28. For example, the current amplification factor near the parallel resonance point indicated by the solid line is suppressed as in the frequency characteristic indicated by the broken line in FIG. That is, the HPF unit 3 and the gain adjusting unit 4 determine the HPF constant and the gain K that have the frequency characteristics shown by the broken line in FIG.

The HPF constant is a low cutoff frequency that allows the parallel resonance frequency f ₁ to pass, and the gain K is determined so as to suppress the current amplification factor | is / i _L | in the vicinity of the parallel resonance frequency f ₁ .

  An example of the load 25 is an arc furnace or the like, and the arc furnace is a load whose current changes abruptly. In the load system 24 to which the load is connected, for example, a low-order filter such as a secondary filter is used for the harmonic filter 28.

When a secondary filter is used for the harmonic filter 28, as shown in FIG. 3 described above, for example, the fundamental frequency f ₀ and the series resonance frequency f ₂ of the harmonic filter 28 (f ₂ = 2f _{0 in} FIG. 3). ), A non-integer-order parallel resonance frequency f ₁ appears.

For example, in the conventional reactive power compensator, the solid line in FIG. 3 is obtained by the system impedance 20 (system inductance Ls) including the power receiving transformer 23 and the impedance (C _F1 and L _F1 ) of the harmonic filter 28 shown in FIG. The parallel resonance as shown may occur. That is, a load line current i _S flowing into the load system 24, the ratio of the load current i _L of the load 25, is that the load line current i _S is increased. In FIG. 3, this corresponds to, for example, the vicinity of the resonance point of the parallel resonance frequency f ₁ existing between the fundamental frequency f ₀ (Hz) and the series resonance frequency f ₂ (Hz) of the harmonic filter 28. Yes, the harmonic current i _F1 flowing into the harmonic filter 28 is increasing.

As a specific example, for example, the parallel resonance frequency f ₁ is about 2 f ₀ −10 (Hz). In such a case, a non-integer order harmonic is generated in the load system 24 to which the conventional reactive power compensator is connected, thereby causing a phenomenon in which the voltage flicker of the load system 24 increases. Such a variation in frequency components appears as a pulsation of about 10 Hz in the voltage of the load system 24, for example, and therefore has the greatest influence as voltage flicker due to the nature of the human eye. Therefore, the voltage flicker due to the parallel resonance caused by the above-described harmonic filter 28 cannot be ignored.

The harmonic suppression device 10a of the present embodiment can suppress voltage flicker caused by the harmonic filter 28 as indicated by a broken line shown in FIG. In other words, harmonic suppression device 10a is, relative to the load system 24 in the vicinity of the parallel resonance frequency f ₁ caused by the harmonic filter 28 can act as a damping resistor Rd shown in Fig.

As described above, harmonic suppression device 10a based on the load current i _L and the load voltage VT, the load 25 can be suppressed voltage flicker due caused by compensating the reactive power of the load 25, also The voltage flicker caused by the harmonic filter 28 can be suppressed by detecting the harmonic component included in the load voltage VT.

  According to the first embodiment, voltage flicker caused by the load and the harmonic filter can be suppressed in the load system including the harmonic filter.

[Second Embodiment]
FIG. 5 is a block diagram showing the configuration of the second embodiment of the harmonic suppression device according to the present invention. FIG. 6 is a diagram illustrating an example of the configuration of the existing TCR of FIG.

  The harmonic suppression system shown in FIG. 5 includes a harmonic suppression device 10b and an existing system 113. That is, in the harmonic suppression system, what is added to the existing system 113 is the harmonic suppression device 10b.

  The existing system 113 includes an existing TCR (Thyristor Phase Controlled Reactor) 13b, a current transformer 26, a voltage transformer 27, and harmonic filters 28 and 29. In FIG. 5, the system impedance 20, the system power source 21, the power receiving system 22, the power receiving transformer 23, the load system 24, the load 25, and the like are the same as those included in FIG. Shall be omitted. The existing TCR 13b is provided in the existing system 113, but may be installed in a new system.

  The existing TCR 13b is a separately-excited reactive power compensator, and is provided mainly to suppress voltage flicker caused by the load 25.

  As shown in FIG. 6, the existing TCR 13 b includes a first separately excited converter 41 and a control circuit 44. The first separately excited converter 41 includes a power semiconductor element that does not have self-extinguishing capability, such as a plurality of antiparallel thyristors 42, a reactor 43, and the like, and is connected to the load system 24. The existing TCR 13b can change the delayed reactive power that is output by changing the point angle.

The control circuit 44 based on the detection signal of the load current i _L and the load system 24 the load voltage VT, calculates a first current command value to compensate for the variation of the reactive power flowing through the load 25. The control circuit 44 controls the arc angle of the antiparallel thyristor 42 based on the first current command value, and controls the delayed phase reactive power to be output.

The load current i _L is included in the load system current is, and the current transformer 26 detects the load current i _L flowing through the load 25. The voltage transformer 27 detects a load voltage VT applied to the load system 24. These detected load current _{i L} and the load voltage VT is input to existing TCR13b.

Existing TCR13b, based on the detected load current _{i L} and the load voltage VT, to compensate for reactive power generated in the load system 24. However, the existing TCR 13b is classified as a separately excited reactive power compensator and has a problem in terms of harmonic generation and the like. Therefore, harmonic filters 28 and 29 and the like are connected to the load system 24 in order to suppress harmonic components with respect to the power supply frequency flowing out to the load system 24. The harmonic currents i _F1 and i _F2 flow into the harmonic filters 28 and 29, respectively. The harmonic filters 28 and 29 may be used as a phase advance capacitor as a separately excited reactive power compensator.

  However, when the harmonic suppression device 10b is not installed, parallel resonance (for example, due to the harmonic filter 28 as described above) is caused by the system impedance 20 including the power receiving transformer 23 and the impedance of the harmonic filter 28 shown in FIG. For example, a solid line shown in FIG. 3 may occur, which may cause voltage flicker. The same applies to the voltage flicker caused by the harmonic filter 29. Hereinafter, the harmonic filter 28 will be mainly described.

  As shown in FIG. 5, the harmonic suppression device 10 b mainly suppresses the voltage impedance caused by the system impedance 20 of the load system 24 and the harmonic filters 28 and 29, and the harmonic suppression control circuit 1 b and the self-excited type. A converter 11 is provided. The harmonic suppression control circuit 1b detects the harmonic component included in the load voltage VT based on the load voltage VT, and controls the self-excited converter 11 so as to suppress the voltage flicker caused by the harmonic filter 28. To do.

  For this purpose, the harmonic suppression control circuit 1b includes a converter control unit 2b, an HPF unit 3, and a gain adjustment unit 4, as shown in FIG.

  The HPF unit 3 is a high pass filter, and has a predetermined HPF constant. The HPF unit 3 extracts a harmonic component from the load voltage VT and outputs it to the gain adjusting unit 4.

Gain adjusting unit 4 to a predetermined gain (K) times the voltage obtained by extracting a harmonic component from the load voltage VT, and outputs to converter control unit 2b as a first current command value i _H ^*.

  Further, in order to suppress voltage flicker due to parallel resonance caused by the harmonic filter 28, the HPF constant of the HPF unit 3 and the gain K of the gain adjusting unit 4 are determined. For example, the current amplification factor in the vicinity of the parallel resonance point indicated by the solid line is suppressed as in the frequency characteristic indicated by the broken line in FIG. That is, in the HPF unit 3 and the gain adjusting unit 4, the HPF constant and the gain K are determined so as to have the frequency characteristics shown by the broken line in FIG.

The first current command value i _H ^* is input to the converter control unit 2b. Converter control unit 2b controls self-excited converter 11 based on first current command value i _H ^* and detected load voltage VT. That is, the converter control unit 2b, so that the first current command value i _H ^*, performs current control of the self-commutated converter 11, the detected load voltage VT, in synchronism with the voltage phase of the system voltage , PWM control of the converter. As a result, the compensation current i _H is output from the self-excited converter 11. The self-excited converter 11 is the same as that of the first embodiment described above, and the description thereof is omitted here.

  In addition, the harmonic suppression apparatus 10b excludes the function part which suppresses the voltage flicker resulting from the load 25 of the harmonic suppression apparatus 10a shown in FIG.

  As described above, in the harmonic suppression system shown in FIG. 5, for example, the newly installed harmonic suppression device 10b only has to suppress voltage flicker caused by the harmonic filters 28 and 29, and therefore the harmonics of the first embodiment. Compared to the suppression device, the capacity can be reduced and the cost can be reduced.

  As described above, according to the second embodiment, voltage flicker caused by the load and the harmonic filter can be suppressed in the load system including the harmonic filter. Moreover, what is necessary is just to introduce a harmonic suppression apparatus newly with respect to the existing system.

  Furthermore, according to the second embodiment, it is possible to apply a device having a smaller capacity and a lower cost than the harmonic suppression device of the first embodiment.

[Third Embodiment]
FIG. 7 is a block diagram showing the configuration of the third embodiment of the harmonic suppression device according to the present invention. FIG. 8 is a diagram showing an example of the configuration of the existing SVC of FIG.

  The harmonic suppression system shown in FIG. 7 includes a harmonic suppression device 10c and an existing system 114. That is, in the harmonic suppression system, what is added to the existing system 114 is the harmonic suppression device 10c.

  The existing system 114 includes an existing SVC (Static Var Compensator) 13c, a current transformer 26, a voltage transformer 27, and harmonic filters 28 and 29. In FIG. 7, the system impedance 20, system power supply 21, power receiving system 22, power receiving transformer 23, load system 24, load 25 and the like are the same as those included in FIG. Shall be omitted. The existing SVC 13c is provided in the existing system 114, but may be installed as a new system.

  The existing SVC 13c is a self-excited reactive power compensator. As shown in FIG. 8, the existing SVC 13 c includes a first self-excited converter 51 and a control circuit 55. The first self-excited converter 51 includes a plurality of self-quenching switching elements 52, a reactor 53, a smoothing capacitor 54, and the like, and is connected to the load system 24.

The control circuit 55 based on the detection signal of the load current i _L and the load system 24 the load voltage VT, calculates a first current command value to compensate for the fluctuation component of reactive power flowing through the load 25. The control circuit 55 controls the current of the first self-excited converter 51 based on the first current command value. The self-extinguishing switching element 52 is a switching element such as a GTO (Gate Turn-Off Thyristor), an IGBT, or the like.

Existing SVC13c, based on the detected load current _{i L} and the load voltage VT, to control the compensation current existing SVC13c to be output to compensate for the reactive power of the load 25. Thereby, the existing SVC 13c mainly suppresses voltage flicker caused by the load 25. As a technique for suppressing voltage flicker caused by the load 25, a known technique is used.

  The harmonic suppression device 10 c is added to the existing system 114 described above, and suppresses voltage flicker caused by the harmonic filters 28 and 29 connected to the load system 24. For this purpose, the harmonic suppression device 10c includes a harmonic suppression control circuit 1c and a self-excited converter 11, as shown in FIG. The harmonic suppression control circuit 1c includes a converter control unit 2c, an HPF unit 3, and a gain adjustment unit 4. The other functional units shown in FIG. 7 are provided in the existing system 114. Moreover, the harmonic suppression apparatus 10c shown in FIG. 7 has the same function as the harmonic suppression apparatus 10b shown in FIG. 5, and the detailed description thereof will be omitted here.

  The harmonic suppression device 10 c mainly suppresses voltage flicker caused by the impedance of the load system 24 and the harmonic filters 28 and 29. As described above, in the harmonic suppression system shown in FIG. 7, for example, the newly installed harmonic suppression device 10c only needs to suppress voltage flicker caused by the harmonic filters 28 and 29. Therefore, the harmonic suppression of the first embodiment is performed. Compared to the apparatus, the capacity can be reduced and the cost can be reduced.

  As described above, according to the third embodiment, voltage flicker caused by the load and the harmonic filter can be suppressed in the load system including the harmonic filter. Moreover, what is necessary is just to introduce a harmonic suppression apparatus newly with respect to the existing system.

  Furthermore, according to the third embodiment, it is possible to apply a device that is smaller in capacity and lower in cost than the harmonic suppression device of the first embodiment.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, the features of the embodiments may be combined. Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  DESCRIPTION OF SYMBOLS 1a, 1b, 1c ... Harmonic suppression control circuit, 2a, 2b, 2c, 103 ... Converter control part, 3 ... HPF part, 4 ... Gain adjustment part, 5, 102 ... Current command calculating part, 10a, 10b, 10c ... harmonic suppression device, 11 ... self-excited converter, 13b ... existing TCR (Thyristor phase Controlled Reactor), 13c ... existing SVC (Static Var Compensator), 20 ... system impedance, 21 ... system power supply, 22 ... power receiving system, 23 ... Receiving transformer, 24 ... Load system, 25 ... Load, 26 ... Current transformer, 27 ... Voltage transformer, 28, 29 ... Harmonic filter, 31, 52 ... Self-quenching switching element, 32, 43, 53 ... Reactor, 33, 54 ... Smoothing capacitor, 41 ... First separately excited converter, 42 ... Anti-parallel thyris , 44, 55 ... control circuit, 51 ... first self-excited converter, 101 ... reactive power control circuit, 110 ... reactive power compensator, 113, 114 ... existing system,

Claims (4)

A current transformer for detecting a load current flowing in the load, mounted on a harmonic suppression device for suppressing harmonics in a load system having a self-excited converter and connected to a load and a harmonic filter, and the load system A harmonic suppression control circuit that receives a detection signal from a voltage transformer that detects a voltage,
A high-pass filter that is passed to extract a harmonic component from the detection signal of the voltage of the load system,
A gain adjusting unit that calculates and outputs a first current command value by multiplying the voltage extracted from the high-pass filter and passed by a predetermined gain;
A current command calculation unit that calculates and outputs a second current command value that compensates for a fluctuation component of the reactive power flowing through the load based on a voltage of the load system and a detection signal of the load current;
A converter controller that adds the first current command value and the second current command value to obtain a compensation current command value, and controls the current of the self-excited converter based on the compensation current command value;
A harmonic suppression control circuit comprising: A harmonic suppression device that suppresses harmonics in a load system to which a load and a harmonic filter are connected,
A current transformer for detecting a load current flowing in the load;
A voltage transformer for detecting the voltage of the load system;
A self-excited converter connected to the load system;
A high-pass filter that is passed from the detected voltage of the load system by extracting harmonic components,
A gain adjusting unit that calculates and outputs a first current command value by multiplying the voltage extracted from the high-pass filter and passed by a predetermined gain;
Based on the detected voltage of the load system and the load current, a current command calculation unit that calculates and outputs a second current command value that compensates for a fluctuation component of the reactive power flowing through the load;
A converter controller that adds the first current command value and the second current command value to obtain a compensation current command value, and controls the current of the self-excited converter based on the compensation current command value;
A harmonic suppression device comprising: A harmonic installed in a load system to which a load and a harmonic filter are connected, and provided with a self-excited reactive power compensator that suppresses harmonics caused by the load and a harmonic suppressor that suppresses harmonics caused by the harmonic filter A wave suppression system,
A current transformer for detecting a load current flowing in the load;
A voltage transformer for detecting a voltage of the load system;
The self-excited reactive power compensator is
A first self-excited converter connected to the load system;
Based on the detected voltage of the load system and the load current, a first current command value that compensates for the fluctuation component of the reactive power flowing in the load is calculated, and the first current command value is calculated based on the first current command value. A control circuit for controlling the current of the excitation converter,
The harmonic suppression device is
A second self-excited converter connected to the load system;
A high-pass filter that extracts harmonic components from the detected voltage of the load system;
A gain adjusting unit that calculates and outputs a second current command value by multiplying a voltage extracted from the high-pass filter by a predetermined gain;
A harmonics suppression system comprising: a converter control unit that controls the current of the second self-excited converter based on the second current command value. A separately excited reactive power compensator that is installed in a load system to which a load and a harmonic filter are connected and suppresses a fluctuation component of reactive power caused by the load, and a harmonic suppression device that suppresses harmonics caused by the harmonic filter A harmonic suppression system comprising:
A current transformer for detecting a load current flowing in the load;
A voltage transformer for detecting a voltage of the load system;
The separately excited reactive power compensator is
A first separately-excited converter connected to the load system, having a plurality of power semiconductor elements having no self-extinguishing capability;
Based on the detected voltage of the load system and the load current, a first current command value that compensates for a fluctuation component of the reactive power flowing through the load is calculated, and the first other value is calculated based on the first current command value. A control circuit for phase-controlling the excitation converter,
The harmonic suppression device is
A second self-excited converter connected to the load system;
A high-pass filter that extracts harmonic components from the detected voltage of the load system;
A gain adjusting unit that calculates and outputs a second current command value by multiplying a voltage extracted from the high-pass filter by a predetermined gain;
A harmonics suppression system comprising: a converter control unit that controls the current of the second self-excited converter based on the second current command value.

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