JPH1189088A - Active filter operation / control method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To operate an active filter by an optimal detection method according to a system state and effectively suppress harmonics of a distribution system according to a purpose. SOLUTION: An active filter 50 is installed on a distribution line 12g of a distribution system in which system switching is performed at the time of a ground fault or the like, and the active filter 50 is detected by a system current detecting unit 6a and a system voltage detecting unit 6b. System current and system voltage. The power flow monitoring means 80 monitors the power flow direction of the power at the connection point of the active filter, and switches the sequence switching circuit 53 when the system switching is performed and the power flow direction changes. The control circuit 54 controls the main circuit unit 55 including an inverter or the like by using the system voltage or the system current input via the sequence switching circuit 53 to suppress the harmonic voltage or the harmonic current of the system. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating / controlling an active filter applied to a distribution system, and more particularly to a method of operating / controlling an active filter capable of improving the influence of harmonic suppression characteristics due to system switching. It is about.

[0002]

2. Description of the Related Art When an active filter is applied to a distribution system, the following two methods are usually used. Voltage detection method Detects the system voltage and controls according to the harmonic voltage included in the system voltage. Current detection method Detects the system current and controls according to the harmonic current included in the system current. It is known that the voltage detection type active filter has a great effect when installed at the end of a system having a large harmonic voltage for the purpose of suppressing voltage distortion caused by harmonic expansion of the system.

On the other hand, the above-mentioned active filter of the current detection system is designed to suppress a harmonic current flowing into a phase advance capacitor in the system due to the harmonic current or voltage distortion generated in the system. It is known that the effect is greater when installed at a higher position in a system where the value becomes larger. However, in an actual power distribution system, there are many occasions in which system switching is performed due to a load transfer, a ground fault, or the like. In this case, for example, if a ground fault occurs at the upper level of the system, to avoid a power failure at the end of the system, disconnect the section switch at the ground fault point and turn on the section switch at the lower side of the system. Power is supplied from a healthy system to the customers connected to the distribution system, and the customers at the terminal end of the system may be connected to a higher order. Similarly, a customer connected to an upper level of the system may be connected to an end of the system.

When the active filter is applied to such a distribution system, when the above-described voltage detection method is used, the voltage detection type active filter installed at a lower level has a small voltage distortion after switching the distribution line. Since it is installed on the upper side, the effect of suppressing harmonics cannot be sufficiently exhibited. In addition, when the above current detection method is used, the current detection type active filter installed at the upper level of the system is fed from the lower system after switching the distribution line, so that the system of the system with less harmonic current is supplied. Since it is arranged at the end, the effect of the active filter cannot be sufficiently exhibited.

FIG. 3 shows the configuration of a system in a normal power flow mode when this type of conventional active filter is applied to the lower side of the system. In the figure, 1 is a receiving point of a distribution substation, 2 is its transformer, 10a, 10b and 1
0c is a lead wire in the substation. In the figure, power is supplied to the first distribution line from the lead wires 10b to 11a to 11c, and the second distribution line from the lead wires 10c to 12a to 12g is supplied.
2 shows a case where power is supplied to two circuits of the distribution line. 31, 35 and 41, which are installed at important points of these distribution lines
Reference numeral 47 denotes a sectional switch using a vacuum switch or the like for disconnecting or switching the distribution system at each point. The closed state of the sectional switch is shown with a back coat, and the open state is shown without a back coat. The figure shows a state in which the sectional switch 35 is opened and all other switches are turned on. In this case,
The active filter 50 of the voltage detection system is connected to the second distribution line 12f.

FIG. 4 is an enlarged view of the power distribution system where the active filter is installed at this time. 7a to 7g are branch points for supplying to each customer,
In general, a large number of consumers are installed in distribution lines. In the drawing, as an example, one customer is collectively shown in the upper and lower positions of the installation point of the active filter 50.
The active filter 50 is connected to the distribution line 12f at the branch point 7e, the current of the distribution line is detected by the current transformer 6a, and the voltage of the distribution line is detected by the transformer 6b. We are taking in. In this figure, since the section switch 35 is open, power at this point is supplied from the section switch 46 side, and the active filter 50 is connected to the end of the second distribution line.

Power is supplied to the power receiving facilities 90a and 90b of the customers from the branch points 7d and 7g through the manual switches 48a and 48b. The power receiving facilities 90a and 90b of the customer are comprised of phase-advancing capacitors 91a and 91b for improving the power factor and power receiving transformers 92a and 92b.
After the voltage is reduced to a required voltage by 92b, the voltage is supplied to a load device including an electronic device that generates a harmonic from its secondary side.

[0008]

In the above-mentioned distribution line system, when a ground fault occurs at a point 7h of the distribution line 12d in FIG. In order to avoid a power failure, a method is adopted in which the switch 35 is turned on to open the switches 44 and 45, and power is supplied from the first distribution line to the distribution lines below the ground fault point 7h. FIG. 5 is a diagram showing the location 14 of the ground fault current when a ground fault occurs.
3 except that the open / close states of the switches 35 and 44 and 45 are changed. In this case, since the active filter 50 of the voltage detection method is connected to the upper side of the system with low voltage distortion, the target to be suppressed changes, and the effect of the suppression decreases.

That is, in the normal power flow mode before the occurrence of the ground fault, the harmonic current is small on the lower side of the system 12f in which the active filter is installed, but the voltage drop due to the higher harmonic current becomes lower in the system. The added voltage distortion increases, and this harmonic voltage is suppressed by the active filter 50. However, in the mode in which the power flow is reversed after the occurrence of the ground fault, the voltage detection type active filter 50 is connected to the upper side of the system where the voltage distortion is low but the harmonic current of each part generated in the system is collected. In the active filter of the voltage detection method,
The harmonic current cannot be effectively suppressed. That is, in this case, it is more effective to suppress the harmonic current by using a current detection type active filter.

As described above, in a distribution system in which system switching is performed, the installation point of the active filter is changed by system switching. However, conventionally, an active filter of a current detection system or a voltage detection system is used in accordance with the purpose of suppressing harmonics. Since the filter is installed in the upper or lower part of the system, it is not possible to cope with system switching, and there is a problem that it is not possible to effectively suppress harmonics after system switching. The present invention has been made in view of the above-described circumstances, and an object of the present invention is to operate an active filter by an optimal detection method according to a system state, and to adjust a harmonic of a distribution system according to an object. An object of the present invention is to provide an active filter operation / control method that can be effectively suppressed.

[0011]

As described above, before and after system switching, the installation point of the active filter in the system changes. Since the purpose of suppressing harmonics changes in the upper and lower systems, it is desirable to switch the method of detecting harmonics when switching the system, and to control with a detection signal corresponding to the installation point of the active filter. Therefore, in the present invention, a system voltage detecting means for detecting a system voltage, a system current detecting means for detecting a system current, and a power flow direction monitoring means are provided, and the active filter connection is provided by the power flow direction monitoring means provided in the active filter. The power flow direction of the point is monitored, and one of the outputs of the system voltage detection means and the system current detection means is selected according to the power flow direction to suppress a harmonic voltage or a harmonic current of the system. In the present invention, as described above, the harmonic voltage or the harmonic current of the system is suppressed according to the power flow direction. Therefore, even when the system is switched, the harmonic of the distribution system is effectively suppressed. be able to.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a main configuration inside an active filter according to an embodiment of the present invention and a connection mode of the active filter to a power distribution system. In the figure, the active filter 50 includes an active filter main circuit unit 55 connected to a connection point 7e of the distribution line 12f via a transformer 56. Based on the voltage detection signal or the current detection signal, an output having an opposite phase to cancel the harmonic is generated to suppress the harmonic of the power distribution system.

The active filter 50 takes in the distribution line current detected by the current transformer 6a, and converts the output of the current transformer 6a into a voltage proportional to the current flowing through the distribution line by the current signal converter 51. Convert. Further, the distribution line voltage detected by the instrument transformer 6b is taken in, and the output of the instrument transformer 6b is converted by the voltage signal converter 52 into a voltage signal having a signal level proportional to the distribution line voltage. A voltage signal proportional to the distribution line current output from the current signal converter 51 or a voltage signal proportional to the distribution line voltage output from the voltage signal converter 52 is taken into the control circuit 54 via the sequence switching circuit 53. The control circuit 54 calculates a compensation command value to the active filter main circuit unit 55 based on the voltage signal proportional to the distribution line current or the voltage signal proportional to the distribution line voltage. The active filter main circuit section 55 and the control circuit 54 are described, for example, in Japanese Patent Application No. 8-215504, edited by The Institute of Electrical Engineers of Japan, March 1987.
Published by the Institute of Electrical Engineers of Japan on March 31 "Semiconductor Power Conversion Circuit" P223-P2
A well-known circuit described in 35 or the like can be used.

The voltage signal detected by the instrument transformer 6b and the signal proportional to the distribution line current detected by the auxiliary current transformer 6c attached to the output line of the instrument current transformer 6a are used for power flow monitoring. Input to the device 80. As shown in FIG. 2, the power flow monitoring device 80
And a signal generator 82, and a three-phase power is calculated by a power transducer 81 based on both the voltage signal and the current signal. In FIG. 2, single-line connection is shown for simplicity. However, if the voltage and current are detected for three phases, the calculated three-phase power becomes a DC amount, and the power flow direction can be determined based on the positive / negative power. That is, the three-phase power calculated by the power transducer 81 outputs a signal proportional to the calculated power in a positive power flow and a negative signal in a reverse power flow, and the signal generator 82 receives a positive signal accordingly. When a negative signal is received from the H terminal, a power flow signal is sent to the sequence switching circuit 53 from the L terminal.

The sequence switching circuit 53 comprises exciting coils 531 and 532 of the relay and their contacts 533 and 534. Then, at the time of positive power flow, the exciting coil 532 side is excited by a signal received from the H terminal side of the signal generator 82, and the contact 534 is made. That is,
At the time of positive power flow, a voltage detection signal is given to the control circuit 54,
The main circuit section 55 including the inverter section of the active filter 50 operates to suppress the harmonic voltage of the power distribution system according to the voltage detection signal. At the time of reverse power flow, the excitation coil 531 side is excited by a signal received from the L terminal side of the signal generator 82, and the contact 533 is made. That is, at the time of reverse power flow, a current detection signal is supplied to the control circuit 54, and the main circuit unit 55 including the inverter unit of the active filter 50 operates so as to suppress the harmonic current of the distribution system according to the current detection signal. I do.

Next, the operation of the active filter of this embodiment at the time of system switching will be described with reference to FIG. The figure shows, as an example of an operation state at the time of system switching, a system state when the power flow at the installation point of the active filter has a reverse power flow to a normal power flow due to the occurrence of a ground fault. The figure shows a case where a ground fault occurs at a point 7h of a distribution line 12d substantially in the middle of the second distribution system. When the above-mentioned ground fault occurs in the distribution system, the ground fault current is detected in the system as described above, and the switch 4
At the same time that the switches 45 and 45 are opened, the switch 35 is turned on and the second
The load near the active filter connection point connected to the lower side of the power distribution system moves to the first power distribution system side.
As a result, the power flow direction goes from the switch 35 to the switch 45 side, and becomes a reverse power flow opposite to the normal power flow state.

When the power flow becomes reverse as described above, the power flow signal calculated and output by the power transducer 81 of the power flow monitoring device 80 provided in the active filter 50 becomes negative, and the power flow from the L terminal side of the signal generator 82 becomes negative. The signal is output, the excitation coil 531 side of the sequence switching circuit 53 is excited, and the contact 533 is made. Therefore, the control circuit 54 of the active filter 50 operates to suppress the harmonic current flowing out of the distribution system according to the current of the distribution system detected by the current detector 6a. Here, when the ground fault is released and the active filter 50 is connected to the lower side of the system, the power flow of the system returns to the normal flow, and the power flow signal calculated and output by the power flow monitoring device 80 is also inverted. And the contact of the sequence switching circuit 53 is 53
The voltage is applied to the voltage detection side of the fourth side. Therefore, the control circuit 54 of the active filter 50 operates in a desirable operation state of harmonic suppression so as to suppress the voltage distortion of the distribution line according to the voltage of the distribution system detected by the voltage detector 6b.

[0018]

As described above, according to the present invention, the power flow at the connection point of the active filter is monitored, and the detection signal is switched to the voltage detection signal or the current detection signal in accordance with the power flow direction at the connection point of the active filter. Therefore, since the system harmonics are suppressed, the active filter can be operated with an optimal detection method according to the system state, and even if the system is switched, the harmonics of the distribution system can be effectively suppressed. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an active filter according to an embodiment of the present invention and a connection mode to a distribution system.

FIG. 2 is a diagram illustrating a configuration of a power flow monitoring device and a sequence switching circuit according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a system state in a normal power flow mode when an active filter is applied to a lower side of the system.

FIG. 4 is an enlarged view of a power distribution system near an active filter installation point in FIG.

FIG. 5 is a diagram illustrating a system state when the power flow at the installation point of the active filter at the time of occurrence of a ground fault has a power flow opposite to a normal power flow state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power receiving point of distribution substation 2 Distribution substation transformer 31-35 Division switch 41-47 Division switch 48a, 48b Manual switch 50 Active filter 51 Current signal converter 52 Voltage signal converter 53 Sequence switching circuit 531 , 532 Switching circuit excitation coil 533, 534 Switching circuit contact 54 Control circuit 55 Active filter main circuit unit 56 Transformer 6a Instrument current transformer 6b Instrument transformer 6c Auxiliary current transformer 7a-7g Branch point 7h Ground fault occurrence Point 80 Power flow monitoring device 81 Power transducer 82 Signal generator 90a, 90b Customer's power receiving equipment 91a, 91b Phase-advancing capacitor 92a, 92b Power receiving transformer 10a, 10b, 10c Leader lines 11a to 11d in substation First distribution Electric wires 12a to 12g Second distribution line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masakazu Kohata 338-1 Ogino, Kamikusayanagi, Yamato-shi, Kanagawa Prefecture Toyo Electric Manufacturing Co., Ltd. No. 338 No. 1 Toyo Electric Manufacturing Co., Ltd.

Claims (1)

[Claims] Claims 1. An operation / control method of an active filter which is installed in a distribution system in which system switching is performed and suppresses harmonics of the system, wherein a system voltage is detected by system voltage detecting means,
The system current is detected by the system current detection means, the system voltage and the system current are taken into the active filter, the power flow monitoring means provided in the active filter monitors the power flow direction at the connection point of the active filter, and according to the power flow direction. An operation / control method of an active filter, wherein an output of one of the system voltage detection means and the system current detection means is selected to suppress and control a harmonic voltage or a harmonic current of the system.