JP2501798B2 - Distribution system harmonic control method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution system harmonic control system, and more particularly to a distribution system harmonic control system for suppressing harmonics of a distribution system.

[Conventional technology]

Conventionally, a power distribution system does not systematically have a large-capacity network unit device, but a large number of network branches are connected and various devices are connected to the network load. What is particularly noteworthy here is the case where a device for controlling the electric power by controlling the firing angle of the thyristor is connected. There are other electrical devices with non-linear input / output characteristics, but when such electrical devices are connected,
In some cases, relatively low-order harmonics are generated with respect to the sine wave voltage source of the distribution system, and the harmonic problem of the distribution system has been studied.

Among such thyristor-applied devices, it is also meaningful to take some measures by predicting the degree of generated harmonics when setting large capacity ones, but for small capacity ones such as It is difficult to take countermeasures by grasping the degree of generated harmonics, and it is particularly difficult to introduce and grasp the characteristics of applicable products (for example, televisions, electric blankets, etc.) in household electric appliances. for that reason,
Recently, the generation of harmonics from a small-capacity load (for example, a television set) whose usage changes significantly has become a particular problem. An example of this detail is a paper (Journal of The Institute of Electrical Engineers of Japan, Vol. 101, No. 8 (August 1981), pages 17 to 24), Inoue's paper: "Fifth distribution line Method of estimating the equivalent circuit of the wave current source and the load ”), but within the range shown in this document, the operating condition of the electrical equipment above the power system must be changed as a countermeasure against this harmonic. Is recommended.

[Problems to be solved by the invention]

As mentioned above, various harmonic generation countermeasures have been taken as such in the past, but depending on the situation, it is difficult to take this countermeasure, and it can be said that it can be implemented in all cases. There was a problem such as not cutting.

The present invention has been made in order to solve the above problems, and an object of the present invention is to obtain a distribution system harmonic control system that can adapt to fluctuations in the distribution system with a relatively simple configuration in all current situations. .

[Means for Solving Problems] A distribution system harmonic control method according to the present invention includes a bus of a distribution system, a feeder drawn from the bus, and a plurality of branch lines further branched from the feeder. A load connected to each of the plurality of branch lines, a distribution system measurement and control means for measuring the harmonic current value of each phase of the feeder and the harmonic voltage value of each phase of the branch line, and this distribution system measurement and control Means and variable admittance means connected to the branch line, and measures and identifies the harmonic content and the same characteristics of the distribution system by the distribution system measurement and control means, and uses the results to suppress the system harmonics. The value of the wave voltage,
The value of the suppression admittance to be inserted is calculated from the system harmonic voltage currently generated, and the admittance means is controlled according to the calculated value.

[Operation] In the present invention, the characteristics and the amount of harmonics of the distribution system are detected, the amount of filters required to suppress the predetermined harmonics is calculated, and the built-in switch automatically puts the filters into the distribution system. Therefore, it is possible to adapt to fluctuations in the distribution system with a relatively simple configuration.

〔Example〕

First, prior to describing the embodiments of the present invention, the prediction of the harmonic distribution in the power distribution system, which is the principle of the present invention, will be described with reference to FIG.

FIG. 5 (a) is a study model diagram suitable for explaining the basic principle of the present invention for predicting a harmonic component. In the figure, (11) is a point P (P ₁ -P ₂ ). The current source (I _Hj ) and admittance (Y
_Hj ) and parallel connections. (12) is point P (P ₁
-P ₂ ) The load side current source, which is the current source (I _Lj ).
And admittance (Y _Lj ) in parallel. (13) is the impedance (Z _tj ) of the distribution transformer connected in series with the power source side current source (11) on the power source side viewed from the P point (P ₁ -P ₂ ), and (14) is the P point ( This is the load impedance (Z _Lj ) connected in series with the load-side current source (12) on the load side as seen from P ₁ -P ₂ ). FIG. 5 (b) is an equivalent circuit diagram when the power source side is viewed from the point P (P ₁ -P ₂ ) of the study model of FIG. 5 (a).

In general, the harmonic generation source is a constant current source, and when the current sources of the voltage (V ₀ ) generated at point P in FIG. 5 (b) are I _S and I _L , the following equation is obtained.

Here, Y _S is the admittance seen from the P side to the power supply side. Y _L is the admittance seen from the P point to the load side. Actually, the power supply side and the load side are connected to lines and devices exhibiting series and parallel impedances. Therefore, Y _S and Y _L are as follows.

Since the above Y _S, the Y _L depends on the frequency, the voltage (V _On generated at the point P with respect to the n-th harmonic generated by the harmonic current generation source such as the following equation (1) The formula holds.

At this time, I _Sn and I _Ln can be detected because they are current values that flow when the point P is short-circuited. Also, since the voltage (V _On ) can be measured, Is found. In order to short-circuit the point P, a network that has an impedance of 0 for the nth harmonic is connected.

Next, when the appropriate admittance Y _On is inserted after knowing the value of (Y _Sn + Y _Ln ) obtained by the equation (5), the following equation is obtained.

Therefore, from the formula (5) Becomes That is, impedance 0 for the nth harmonic
After making a trial connection of a network that becomes, I _Sn , I _Ln , V _On
After measuring the admittance Y _Sn on the power supply side and the admittance Y _Ln on the load side, set an appropriate admittance value Y _O for the nth harmonic to obtain the desired nth harmonic voltage. _Assuming that the value of V _OnL is V _OnL , the following equation holds.

Here, the second term on the right side can be measured.

As described above, it is possible to reduce the voltage level of the harmonic component of the order, which is the current suppression symmetry, below the level.

The 5th to 7th orders are currently being talked about as the harmonic orders, and 3rd order, 6th order, 9th order, etc.
It is not necessary to consider that the harmonic component of the multiple of circulates outside the device because it circulates in the Δ connection of the transformer. Also, the eleventh
It is said that the following and above do not have to be particularly problematic because there is no problematic amount in the current distribution system.

From the above, it is often said that the frequency characteristics of the above-mentioned suppression admittance Y _On are usually known (for example, a combination of passive elements).

Next, examples will be described. FIG. 1 is a schematic diagram of an embodiment of a distribution system harmonic suppression method according to the present invention. In the figure, (01) is a distribution system bus bar, (02) is a feeder drawn from this bus line (01), (2) is a branch line further branched from this feeder (02), (3) is a load connected to the branch line (2), (4) is a distribution system measurement and control means, and the feeder (02) Current measuring transformers (6-a), (6-
b), (6-c), and voltage measuring transformers (7-a), (7-b), (7-) for measuring the voltage of each phase of the branch line (2). It is connected to each of c). (5) is a variable admittance means, which is connected to each phase of the branch line (2) and further connected to the distribution system measurement and control means (4). The current measuring transformer (6) and the voltage measuring transformer (7) both have satisfactory frequency characteristics up to about twice or more the frequency at which the harmonic to be measured exists. .

FIG. 2 is a detailed configuration diagram of each part of the distribution system measurement and control means (4) and variable admittance means (5) shown in FIG. 1, and the same reference numerals as those in FIG. The description is omitted because it is the same as or equivalent to the above. The distribution system measurement and control means (4) samples and holds the instantaneous voltage value of each phase of the branch line (2).
Means (4-P), second means (4-C) for sampling and holding the instantaneous current value of each phase of the feeder (02), first means (4-P) and second means (4-C) ) And the measuring means (4-d) connected to the output side. The variable admittance means (5) is a filter (5-F) connected to each phase of the feeder (02), and a switch means connected to the filter (5-F) and the measuring means (4-d) described above. (5-S). FIG. 3 is a more detailed configuration diagram of each part of the distribution system measurement and control means (4) shown in FIG. 2, in which the same symbols as those in FIG. 1 are the same as those in FIG. Since it is a considerable one, its explanation is omitted. The first means (4-P) for sampling and holding the instantaneous voltage value is a voltage measuring transformer (7-a), (7-a).
b) and (7-c) are connected to the first auxiliary transformers (41-a), (41-b) and (41-c), respectively, and the three phase components connected to these first auxiliary transformers. First level converter L /
Comprised of C (43-1) and the first sample and hold amplifier (SHA) (44-1) connected to this 1st L / C (43-1) The voltage values to be measured are measured by the first auxiliary transformers (41-a), (41-b), and (41-c) respectively, and the measured values are level-converted by the first L / C (43-1). The first SHA (44-1) samples and holds the instantaneous value at the time given from the microprocessor unit (MPU). The second means (4-C) for sampling and holding the instantaneous current value is the current measuring transformers (6-a) and (6--).
b) and (6-c) are connected to the second auxiliary transformers (42-a), (42-b) and (42-c) respectively, and the first auxiliary transformers connected to these second auxiliary transformers. Second L / C similar to C (43-1)
(43-2) and the 1st S connected to this 2nd L / C (43-2)
The second auxiliary transformer (42-a), (42-b), which is composed of the HA (44-1) and the second SHA (44-2) similar to the HA (44-1), and outputs the current value corresponding to the line current of each of the three phases. , (42-c) respectively, and the second L / C (43-2) level-converts this measured value, MP
The instantaneous value at the time given by U (47) is set to the second SHA (44−
Sample and hold in 2). The measuring means (4-d)
Multiplexer (MPX) (45) connected to the first SHA (44-1) and second SHA (44-2) respectively, and this analog / digital (A / D) connected to the output side of this MPX (45)
It is composed of a converter (46) and an MPU (47) for processing the output data of the A / D converter (46).

FIG. 4 shows a filter (5-F) and a switch means (5-) of the variable admittance means (5) shown in FIGS. 2 and 3.
2 is a specific circuit diagram of S), in which the same reference numerals as those in FIG. 1 are the same as or correspond to those in FIG. Filter (5-F) is LoCo parallel resonance filter (51-a), (51 -b), (51-c) and L _S C _S series resonance filter (52-a), (52 -b), (52 -C) and These two filters are connected in series, respectively, and L _O C _O parallel resonance filters (51-a) and (51-
b) and (51-c) are connected to the respective phases of the branch line (2). The switch means (5-S) is composed of thyristor switches (53-a), (53-b) and (53-c) and is connected to the filter (5-F) to distribute the variable admittance means (5). Disconnect from the system or use capacitor C _S
Used when making fine adjustments. Each input of the thyristor switch (53-a), (53-b), (53-c) is connected to the measuring means (4-d), and this measuring means (4-d).
From thyristor switch (53-a), (53-b), (53
-C) are each triggered.

In the distribution system harmonic control system configured as described above, in FIG. 1, first, harmonics flow through the feeder (02) connected to the bus (01) of the distribution system. In order to detect the admittance seen from the distribution system side from the branch line (2) branched from the feeder (02) and the admittance seen from the branch line (2) toward the load side, the branch line (2) is detected. Variable admittance means connected (5)
Is first controlled by the distribution system measurement and control means (4). And the transformers for current measurement (6-a), (6-b), (6
-C), voltage measuring transformers (7-a), (7-b),
The current and voltage transformed by (7-c) are applied to the distribution system measurement and control means (4). In the distribution system measurement and control means (4), the current measurement transformer (6-a),
Currents from (6-b) and (6-c) and voltages from the voltage measuring transformers (7-a), (7-b), and (7-c) are instantaneously measured, and waveform analysis is performed. The admittance on the distribution system side and on the load side is detected based on the above-described principle of the present invention.

Next, from this detection result, the minimum value of the admittance change required to satisfy the harmonic voltage suppression target value at the lead-in point of the branch line (2) is determined, and whether the predetermined amount is satisfied at this point is determined. After the determination, the operation such as connecting / disconnecting the variable admittance means (5) is performed. If the operation such as connecting / disconnecting the variable admittance means (5) is not satisfactory, the situation is transmitted to an adjacent harmonic suppression device installation point by an appropriate transmission means, for example, a distribution line carrier system. To do. At this installation point, in consideration of this situation, more reliable admittance detection on the distribution system side and the load side is performed, and similarly the connection / disconnection of the variable admittance means (5) at that point is controlled.

By repeating the above, the harmonic voltage at the main points of the entire distribution system is suppressed intensively. The operation in FIG. 2 is the same as the operation in FIG. In Fig. 3, the output values obtained by the first SHA (44-1) and the second SHA (44-2) are added to MPX (45), and MPX (45) is sequentially output by the command from MPL (47). The output is switched and applied to the A / D converter (46). This A / D converter (46) is MPX (4
The analog value of the output of 5) is converted into a digital value and this is input to the MPU (47). This MPU (47) is
The converted digital value of the instantaneous current value is subjected to harmonic analysis to obtain the amplitude of each harmonic component. As a result, the admittance for each harmonic of each order is calculated from the obtained harmonic component value, and the admittance on the power distribution system side is detected as in the above-described basic principle to obtain one set of data. The same measurement is repeated a required number of times to accumulate data. In addition, this data is MPL
By processing in (47), the admittance value required for insertion at this point is calculated. In Figure 4, L _O C _O parallel resonance filter (51-a), (51 -b), to prevent the shunt current from the power distribution system (51-c) each parallel resonance to the commercial frequency of the distribution system . L _S C _S Series resonance filter (52−
a), (52-b) , ( for the next number of harmonics, each tries to reduce the _{52-c), L O C} O parallel resonance filter (51
-A), (51-b), and (51-c) resonate in series, respectively.

Now, assuming that the order of this harmonic is k, the following equation is obtained.

Bypassing C _S Is.

By selecting L _S C _S in this way, the admittance of the harmonic of the target order is bypassed as infinity. Here, the capacitor C _S may be used for fine adjustment when the series resonance is difficult to adjust with the inductance L _S.

In the above embodiment, the internal circuit of the variable admittance means (5) uses the filter.
Various modifications are conceivable as long as it is possible to prevent shunting of the frequency component of the distribution system to the filter and fine-tune the short-circuit side and the frequency for the harmonic of a specific frequency.

For example, an active filter using an inverter is suitable because the injection point impedance can be varied so that a waveform containing various harmonic components can be formed by controlling the injection.

In this type, the harmonics existing in the distribution system are searched for the frequency with a large component, then the admittance of the distribution system for this frequency is detected, and it is necessary to absorb the harmonics based on this detection result. Insert and connect the appropriate admittance value.

[Advantages of the Invention] As described above, the present invention includes a bus of a distribution system,
The feeder drawn from this bus, a plurality of branch lines further branched from this feeder, the loads connected to each of the plurality of branch lines, the harmonic current value of each phase of the feeder and each phase of the branch line. The distribution system measurement and control means for measuring the harmonic voltage value of and the variable admittance means connected to the distribution system measurement and control means and connected to the branch line are provided to measure the amount of harmonics of the distribution system and the same characteristics. Measure and identify by the distribution system measurement and control means, and use this result to calculate the suppression admittance value to be inserted from the value of the system harmonic voltage after suppression and the system harmonic voltage that is currently occurring. However, since the admittance means is controlled according to the calculated value, the fluctuation of the system harmonics due to the power supply load of the distribution system is appropriately suppressed with a relatively simple configuration. There is an effect that theft can be.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of each part of the distribution system measurement and control means (4) and variable admittance means (5) shown in FIG. 1, and FIG. Is a more detailed block diagram of the distribution system measurement and control means (4) shown in FIG. 2, and FIG. 4 is a filter (5-F) and switch means (of the variable admittance means (5) shown in FIG. 5
-S) is a concrete circuit diagram, and FIG. 5 is a model diagram suitable for explaining the basic principle of the present invention. In the figure, (01) …… Bus, (02) …… Fida,
(2) ...... Branch line, (3) ...... Load, (4) ...... Distribution system measurement and control means, (5) ...... Variable admittance means, (6) ...... Current measurement transformer, (7) ...... Voltage measuring transformer, (11) …… Power source side current source, (12) …… Load side current source, (13) …… Distribution transformer impedance,
(14) …… load impedance, (41) …… first auxiliary transformer, (42) …… second auxiliary transformer, (43-1) …… first
1L / C, (43-2) …… Second L / C, (44-1) …… First SHA,
(44-2) …… Second SHA, (45) …… MPX, (46) …… A / D
Converter, (47) ... MPU, (51) ... parallel resonance filter, (52) ... series resonance filter, (53) ... thyristor switch. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (6)

(57) [Claims] 1. A bus of a power distribution system, a feeder drawn from the bus, a plurality of branch lines further branched from the feeder, a load connected to each of the plurality of branch lines, and each of the feeders. Distribution system measurement and control means for measuring the phase harmonic current value and the harmonic voltage value for each phase of the branch line, and variable admittance means connected to the distribution system measurement and control means and connected to the branch line And measure and identify the amount of harmonics of the distribution system and its characteristics by the distribution system measurement and control means, and use the results to determine the value of the system harmonic voltage after suppression and the system harmonics that are currently occurring. A distribution system harmonic control method, wherein a suppression admittance value to be inserted is calculated from the wave voltage, and the admittance means is controlled according to the calculated value. 2. The distribution system measurement and control means comprises first means for sampling and holding the instantaneous voltage value of each phase of the branch line, and second means for sampling and holding the instantaneous current value of each phase of the feeder.
The harmonic control method for a distribution system according to claim 1, characterized in that it comprises a means and a measuring means connected to the output side of the first means and the second means. 3. The power distribution system according to claim 1, wherein the variable admittance means comprises a filter connected to each phase of the feeder and a switch means connected to the filter. Harmonic control method. 4. The measuring means comprises a multiplexer, an A / D converter connected to the output side of the multiplexer, and the A / D converter.
The harmonic control method for a distribution system according to claim 2, characterized in that it is constituted by a microprocessor unit connected to the output side of the converter. 5. The distribution system harmonic control method according to claim 3, wherein the filter is composed of a series circuit of an LC parallel resonance filter and an LC series resonance filter. 6. The power distribution system harmonic control system according to claim 3, wherein the switch means comprises a thyristor switch.