JPH05292670A - Controlling system for dispersed power supply in distribution system - Google Patents

Abstract

PURPOSE:To maintain the voltage of a distribution system within a proper range when a dispersed power supply is connected to the distribution system and operated. CONSTITUTION:Dispersed power supplies 9a, 9b are connected to a distribution line 7b directly or through an AC converter 10. A voltage time waveform V2 and a current time waveform I2 in the vicinity of the node of the distribution line 7b and a current time waveform Id2 delivered between the distribution line 7b and the dispersed power supply 9b are detected by a voltage sensor 11 and current sensors 12, 13 and taken into a conatroller 14 at the time of the dispersed power supply 9b. A voltage value on the secondary side, the distribution system side, of a transformer 3 for the distribution of electrical energy is also detected by a voltage sensor 17 and taken into the controller 14. The controller 14 controls the dispersed power supplies 9a, 9b or the AC converter 10 on the basis of these input information. Accordingly, the voltage of a distribution system can be maintained within a proper range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power distribution system distributed power supply control system, and more particularly to a power distribution system distributed power supply control system suitable for optimally controlling distributed power supplies connected to a power distribution system.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of energy saving and new energy development, distributed power sources such as cogeneration and solar power generation have been attracting attention. Unlike large-scale centralized power sources of electric power companies, these distributed power sources are located near customers in the distribution system, and therefore operate as a highly efficient power system with low transmission costs and easy response to changes in demand. I have the possibility to do it.

The operation mode for such a distributed power source is as follows.
Currently, distributed power sources are limited to receiving power from the distribution system, but in the near future, it will be possible to operate by injecting power into the distribution system by taking advantage of the above features.

[0004]

However, the current distribution system has only one power supply source connected to the upper system,
It has a tree-like structure on the assumption that there is no power source in the distribution system. Therefore, it is expected that various problems will occur in terms of power quality, supply reliability, safety, etc., depending on how the distributed power sources are operated. In particular, the following problems are expected with respect to maintaining an appropriate voltage.

As described above, since the power distribution system has a single power source and a dendritic structure, active power always goes from the power source to the dendritic end. On the other hand, the reactive power may be on the delay side due to the characteristics of the load connected to the power distribution system, and as a result, the voltage often has a distribution that decreases from the power supply toward the end. By adjusting the taps according to the distance from the distribution substation, the supply voltage to general consumers is maintained within an appropriate range. On the other hand, if a distributed power source will be connected to the distribution system in the future and will be operated by exchanging power with the distribution system, the direction of the power will change in a complicated manner depending on the operation of the distributed power source. Such a method has a problem in that it is difficult to maintain an appropriate voltage range. For example, when a large amount of advanced reactive power is supplied from the distributed power source to the distribution system, the voltage rises from the power source toward the end, and the tap adjustment in the pole transformer has the opposite effect, resulting in a general demand. The result is that the voltage supplied to the house deviates from the proper range. It should be noted that such a state is conceivable even in the present day when power is not being supplied from the distributed power source to the distribution system in a distribution system with a large capacitance, and from this point also measures must be taken to maintain the appropriate voltage range. there were. An object of the present invention is to connect a distributed power source to a power distribution system and operate the voltage distribution system when the power is exchanged with the power distribution system or when the power is operated with a large capacitance. It is to provide a distributed power supply control system that can maintain the power distribution within an appropriate range.

[0006]

In order to achieve the above object, the present invention provides a distribution system distributed power supply control system, a distribution system to which power is supplied from a higher-order power system through a distribution transformer, and the distribution system. A plurality of distributed power sources connected in the grid, and a control that controls the output of the distributed power source so that the voltage at the connection point between the distributed power sources and the power distribution system approaches the voltage on the power distribution system side of the distribution transformer. It is composed of a device.

[0007]

[Operation] The output of the distributed power source is controlled by the control device so that the voltage at the connection point between the distributed power source and the power distribution system approaches the voltage on the power distribution system side of the power distribution transformer. It can be maintained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of a distribution system distributed power supply control system according to the present invention.

In FIG. 1, the power distribution system includes a power distribution transformer 3 installed in the power distribution substation 1 for converting a supply voltage from a higher power system 2 into a power distribution voltage, and an opening / closing connected to the power distribution transformer 3. And a three-phase bus bar 5 connected to the switch 4.
And a plurality of distribution lines 7a, 7b connected to the three-phase bus 5 via switches 6a, 6b. In addition to the loads 8a and 8b, there are distributed power sources 9a and 9b on the distribution line 7b.
b is connected. Here, the dispersed power source 9a is assumed to be an alternating current power source by an alternating current generator, the dispersed power source 9b is assumed to be a direct current power source such as photovoltaic power generation or a fuel cell, and the dispersed power source 9b is connected to the distribution line 7b via the AC / DC converter 10. To be done. Here, the case where two distributed power sources are connected to the distribution line 7b is shown as an example, but it is assumed that a plurality of distributed power sources are also connected to other feeders such as the distribution line 7a.

Here, the distributed power supply 9b will be taken as an example to explain the distribution system distributed power supply control system according to the present invention. The distribution system distributed power supply control system includes a voltage sensor 11 and a current sensor 12 for detecting a voltage time waveform V ₂ and a current time waveform I ₂ near the connection point between the distributed power source 9b and the distribution line 7b.
And a current sensor 13 for detecting a current-time waveform I _d2 transmitted and received between the distribution line 7b and the distributed power source 9b, and the detection outputs of the voltage sensor 11 and the current sensors 12, 13,
The controller 14 controls the distributed power source 9b and the AC / DC converter 10. Further, the control device 14 is also provided with a cooperation control command device 16 which gives a cooperation command with another distributed power supply control device via the communication line 15. Further, the voltage value on the secondary side of the distribution transformer 3, that is, the distribution system side is detected by the voltage sensor 17 and taken into the cooperative control command device 16.

Next, the configuration of the control device 14 will be described with reference to FIG. In FIG. 2, the control device 14 includes input units 18a, 18b, which convert detection outputs of the voltage sensor 11 and the current sensors 12, 13 into predetermined voltage waveform signals.
18c, a voltage output signal from the input units 18a, 18b, 18c and a coordination command from the coordination control command device 16 are fetched, and a control signal is generated to send a control command to the distributed power source 9b and the AC / DC converter 10 by a predetermined control logic. Part 19
It has and.

The operation of the controller 14 will be described with reference to FIG. First, the cooperative control command device 16 transmits the distributed power source near the end of the distribution system, that is, the distributed power source 9b in the case of FIG.
To the control command. The control device 14 receives the control start command signal from the cooperative control command device 16, and
The control logic shown in is started. First, in S1, the secondary side voltage value V _s of the distribution transformer 3 and the voltage time waveform V ₂ ′ in the vicinity of the connection point between the distributed power source 9b and the distribution line 7b are read together with the control start command. Hereinafter, the numerical suffix 2 represents data regarding the distributed power supply 9b, and the suffix 1 represents data regarding the distributed power supply 9a. A waveform signal is represented as V ₂ ′, and its absolute value is represented as V ₂ by taking ′. At S2, the secondary side voltage value V _{s of} the distribution transformer 3
And the absolute value ΔV ₂ of the difference between the voltage value V _{2 in the} vicinity of the connection point and V ₂ is calculated and compared with the reference voltage V _th . If ΔV ₂ is not larger than V _th , it is determined that control is not necessary and the process jumps to S10. If ΔV ₂ is larger than V _th, it is checked in S3 whether active or reactive power can be supplied from the distributed power source 9b to the distribution line 7b. If it can be supplied, the current time waveform I ₂ near the connection point is output in S4. It is captured.
If the supply is impossible, it is determined that the control is impossible and the process jumps to S10. In S4, first, the phase difference θ ₂ between the voltage time waveform V ₂ ′ and the current time waveform I ₂ ′ near the connection point is obtained,
Next, the voltage drop to the vicinity of the connection point is calculated by the formula shown in S5. These equations will be described. In general, considering a distribution line section k in which the load is concentrated only at the end in the same line type, the voltage drop ΔV _{k in} that section is obtained by the following equation.

ΔV _k = r _k l _k · I _k cos θ _k + x _k l _k · I _k sin θ _k (1) where r _k and x _k are line resistance per unit length of k section and Reactance l _k : Distribution line length of k section I _k : Apparent current flowing in distribution line of k section cos θ _k : Power factor of k section In the equation (1), the first term is the voltage drop due to the active current I _p , The second term is the voltage drop due to the reactive current I _q, which is expressed by ΔV _p and ΔV _q , respectively. From the equation (1), the voltage drop to the vicinity of the connection point between the distributed power source 9b and the distribution line 7b is obtained by the following equation.

ΔV ₂ = Σr _k l _k · I _k cos θ _k + Σx _k l _k · I _k sin θ _k (2) Here, a section is a connection point from the secondary side of the distribution transformer 3 to the distributed power source 9 b. Take up. The first term and the second term shown in the equation (2) are the equations of ΔV _p2 and ΔV _q2 shown in S5, respectively.

In S6, the absolute value of ΔV _p2 is the reference voltage V
_pth, and if | ΔV _p2 | is greater than V _pth , then S
7, the effective current I _{dp2 is} applied to the distribution line 7b within the capacity of the distributed power source 9b so that | ΔV _p2 | becomes V _pth or less.
Is supplied. That is, by supplying the effective current I _dp2 , the effective current I ₂ · cos of the distribution line 7b on the higher system side from the connection point
θ ₂ decreases, and the voltage drop ΔV _p2 on the upper system side correspondingly
Will be smaller. In S6, | ΔV _p2 | is V _pth
If it is not larger, it is judged that the control of the active current is not necessary and the control of S7 is not performed and the process jumps to S8. In S8, the absolute value of V _q2 is compared with the reference voltage V _qth, and | ΔV
_q2 | proceeds to S9 is greater than V _qth, | ΔV _q2 | is supplied reactive current I _dq2 distribution line 7b within the range of capability of the distributed power 9b to be less than V _qth. In this case, the reactive current I _dq2 is supplied to reduce the reactive current I ₂ · sin θ ₂ of the distribution line 7b on the upper system side from the connection point, and the voltage drop ΔV _p2 on the upper system side is correspondingly reduced. .. In S10, the control end signal of the distributed power source 9b is transmitted to the cooperation command device 16, and the control of the distributed power source 9b ends. After receiving the control end signal of the distributed power source 9b, the cooperation command device 16 sends a control command to the distributed power source closer to the upper system than the distributed power source 9b, that is, in the case of FIG. 2, the distributed power source 9a. The control device for the distributed power source 9a controls the distributed power source 9a in the same procedure as in FIG.

In order to explain the voltage change when such control is performed, assume the following power distribution system,
This will be described with reference to FIGS. 3 to 12. First, consider a distribution line having a length of 12 km in which loads are concentrated only at the ends of the distribution line. The load current and power factor are 500
Assume A, 0.95. Therefore, the distribution line apparent current before control has the distribution shown in FIG. The line resistance and line reactance are constant along the distribution line and are 0.08 Ω / km and 0.3 Ω / km, respectively.

For the distribution line assumed above, the above (2)
Secondary side voltage value V _{s of the} distribution transformer 3 calculated by the formula
The voltage drop from is shown in FIG. FIG. 6 shows the distribution of the active current I _p and the reactive current I _q calculated from the apparent current and the power factor.

As described with reference to FIG. 3, first, the distributed power source 9b.
Is the control target. As shown in FIG. 5, the absolute value ΔV ₂ of the difference between the secondary voltage value V _s of the distribution transformer and the voltage value V _{2 in the} vicinity of the connection point is 916 V, which is compared with the reference voltage V _th. It is assumed that it is determined that control is necessary. S
In No. 3, it is checked whether power can be supplied from the distributed power source 9b to the distribution line 7b. In this case, it is assumed that power can be supplied. In S5, the respective voltage drops ΔV _p2 and ΔV _q2 due to the active current and the reactive current are obtained using I ₂ and θ ₂ as shown in FIG.

As shown in FIG. 7, since ΔV _p2 is as large as about 400 V, it is determined in S6 that active current control is required, and the active current I _dp2 is applied to the distribution line 7b within the capacity of the distributed power source 9b. Supplied. In this case, the effective current I _dp2 supplied is set to 200 A as shown in FIG. 8 due to the capability of the distributed power source 9b. As a result, in the distribution line 7b, the effective current from the connection point to the upper system side is reduced to 275A, and the voltage drop ΔV _p2 to the connection point is improved by that amount as shown in FIG.

Similarly, the reactive current I _dq2 is 140 A in S9.
The voltage drop ΔV _q2 to the connection point is also improved as shown in FIG.

With the above, control of the distributed power source 9b is completed, and S
In 10, the control end signal of the distributed power source 9b is the cooperation command device 1
6 is transmitted. After receiving the control end signal of the distributed power source 9b, the cooperation command device 16 transmits a control command to the distributed power source closer to the upper system than the distributed power source 9b, that is, the distributed power source 9a. After receiving the command signal through the control, the control device of the dispersed power source 9a operates in the same procedure as in FIG.
control a.

FIG. 1 shows how the distributed power source 9a is controlled.
Shown from 0 to FIG. In this case, since the value of the voltage drop ΔV _q1 in the distribution line 7b to the connection point of the distributed power source 9a is small, it is determined that the reactive current control is not necessary.
Only active current control shall be implemented. As a result, the voltage drop ΔV _p to the connection point is improved as shown in FIG. 11, and ΔV (= ΔV _p + ΔV _q ) as shown in FIG.
Is 378 for the voltage drop ΔV = 1099V in FIG.
It becomes V and is greatly improved.

As described above, in the voltage control by the distributed power source, the voltage drop ΔV of the distribution line on the higher system side from the connection point of the distributed power source becomes smaller. Control to make it close to the voltage on the secondary side of the distribution transformer, and then to perform efficient control by repeating the same control for multiple distributed power sources from the terminal side to the upper system side. You can On the other hand, if the distributed power supply located on the upper system side is controlled first, the voltage at the connection point will change under the influence of the distributed power supply control located on the terminal side, so re-control is necessary. The control efficiency will decrease.

[0024]

As described above, according to the distribution system distributed power supply control system of the present invention, the voltage at the connection point between the distributed power supply and the distribution system is equal to the voltage on the distribution system side of the distribution transformer. Since the configuration is such that they are controlled closer to each other, when a distributed power source is connected to a distribution system and is operated by exchanging power with the distribution system, or when a distribution system with a large capacitance is operated with a light load. Moreover, it is possible to obtain a distribution system distributed power supply control system capable of maintaining a distribution voltage within an appropriate range.

Further, in the distribution system distributed power supply control system of the present invention, from the distributed power supply connected to the terminal side of the distribution system,
Since it is configured to control the distributed power sources on the side closer to the upper power system, efficient control is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a distribution system distributed power supply control system according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of a control device in FIG.

FIG. 3 is a flowchart showing a control logic of the control device in FIG.

FIG. 4 is a diagram showing a distribution of distribution line apparent current before the control logic in FIG. 3 is executed.

5 is a diagram showing a voltage drop of a distribution line before the control logic in FIG. 3 is implemented.

FIG. 6 is a diagram showing distributions of active currents and reactive currents.

FIG. 7 is a diagram showing respective voltage drops due to active current and reactive current.

8 is a diagram showing distributions of active current and reactive current in a distribution line when the control logic in FIG. 3 is executed.

9 is a diagram showing respective voltage drops due to an active current and a reactive current of a distribution line when the control logic in FIG. 3 is implemented.

10 is a diagram showing distributions of active currents and reactive currents of a distribution line when the control logic in FIG. 3 is implemented.

11 is a diagram showing respective voltage drops due to an active current and a reactive current of a distribution line when the control logic in FIG. 3 is implemented.

12 is a diagram showing a voltage drop of a distribution line when the control logic in FIG. 3 is implemented.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Distribution substation, 2 ... Upper power system, 3 ... Distribution transformer, 4 ... Switch, 5 ... Three-phase bus, 6a, 6b ... Switch,
7a, 7b ... Distribution line, 8a, 8b ... Load, 9a, 9b ...
Distributed power source, 10 ... AC / DC converter, 11 ... Voltage sensor, 1
2, 13 ... Current sensor, 14 ... Control device, 15 ... Communication line, 16 ... Cooperative control command device, 17 ... Voltage sensor, 18
a, 18b, 18c ... Input section, 19 ... Control signal creation section.

Front page continuation (72) Inventor Yasuhiro Terada 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika factory

Claims (3)

[Claims] 1. A power distribution system to which power is supplied from a higher-level power system via a distribution transformer, a plurality of distributed power sources connected to the power distribution system, and a controller for controlling the output of the distributed power source. Wherein the control device controls the voltage at the connection point between the distributed power source and the power distribution system so as to approach the voltage on the power distribution system side of the power distribution transformer. system. 2. The distributed power supply system control system according to claim 1, wherein the control by the control device is performed based on a voltage and / or a current at a connection point between the distributed power supply and the power distribution system. 3. The control according to claim 1, wherein the control is performed from a distributed power source connected to a terminal side of the power distribution system toward a distributed power source near a higher power system. Power distribution system distributed power control system.