JPH0556564A - Distributed power system - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the reverse flow of power from the distributed power supply to the power system. [Configuration] Power generation device (3) connected to the power system (1)
And a load group (4), means (8) for detecting active power at this interconnection point, and a load device (15) for controlling active power consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed power system in which a plurality of solar power generators, wind power generators, etc. are connected to a power system.

[0002]

2. Description of the Related Art Recently, power generation technology development utilizing natural energy such as sunlight and wind power has been underway. Many of these have medium and small capacity, and are so-called distributed power sources that are interconnected as distributed power sources to the power system. Recently, when connecting these distributed power sources to the power grid,
The technical requirements that must be met in order to configure the power system so as not to adversely affect it, so-called grid interconnection technical requirements, are set. The main contents of this technical requirement are (1)
Keeping the power factor at the interconnection point at 0.85 or more, (2) Total harmonic current distortion rate of 5% or less, each order of 3% or less,
(3) There is a situation in which electric power is not supplied to the system side (so-called reverse power flow prevention), etc., and a compensator is required to satisfy these.

Of these, in order to keep the power factor at the interconnection point high, a reactive power compensator is often used, and recently, due to the progress of power electronics, an active filter type which also has a function of compensating for harmonic currents. Reactive power compensators have come to be used. But,
A device for preventing reverse power flow is a new technical issue, and an effective configuration is currently being explored and studied.

FIG. 3 shows an example of a conventional system configuration having a distributed power source installed in a general consumer. In FIG. 3, (1) is a power system, (2) is a power breaker, (3) is a power generator, and (4) is a load group. In normal operation, with respect to the power consumed by the load group (4), the output of the power generation device (3) considers that the natural energy that is the input is used as effectively as possible, and is maximized within the range not exceeding the power consumption. Often controlled, no reverse flow occurs in this range of operation. However, for example, when the operating capacity of the load group (4) sharply decreases, the generated power of the power generator (3) exceeds the load capacity, and until the output control of the power generator operates, the power system (1 ) Will be supplied with electricity. in this case,
With the protection relay system at the interconnection point (not shown in Fig. 3),
Reverse power flow was detected and tripped the power breaker (2), leading to system shutdown.

[0005]

As described above, the system having the distributed power source installed in the general consumer as described above has the following problems. That is, of the technical requirements for grid interconnection, reactive power and harmonics can be effectively compensated by a reactive power compensator, but reverse power flow can be effectively compensated when a reverse power flow occurs due to a sudden decrease in load, etc. Since there is no device to prevent it, a reverse power flow was detected in the protective relay system, and it was necessary to trip the power breaker and shut down the entire system.

An object of the present invention is to solve the above-mentioned problems, to prevent reverse power flow in any case, and to provide a distributed power system which can satisfy the technical requirements for grid interconnection.

[0007]

DISCLOSURE OF THE INVENTION A distributed power system according to the present invention comprises a generator and a load group connected to an electric power system, a means for detecting active power at this connection point, and consumption of active power. And a load device for controlling the amount.

[0008]

The operation of the present invention will be described. In a distributed power system having a distributed power supply, during normal operation, the output of the power generator is configured or controlled to match the amount of load groups. In this system, when the load group is drastically dropped for some reason during operation, the output control of the generator is not in time and the generated power exceeds the power consumption of the load group. At this time, the active power consumption of the load device is controlled so that the active power detected at the interconnection point does not fall below the set value. This makes it possible to prevent electric power from being sent from the interconnection point to the grid.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, (1) is a power system, (2) is a power breaker, (3) is a power generator, (4) is a load group,
(5) is a device configured to control the consumption of active power by connecting a thyristor switch (9) and a resistor (10) in series. Further, a measuring device (8) for detecting active power is added to the interconnection point. Next, the operation of the above embodiment will be described.

Usually, in the distributed power system, the power consumption of the power generator (3) is considered to be as effective as possible with respect to the power consumed by the load group (4) in consideration of the use of natural energy as an input. Control to the maximum without exceeding. At this time, regarding the conditions of the technical requirements for grid interconnection, and (3) preventing active power from flowing into the grid side (so-called reverse power flow), in normal operation, the operating conditions should be set so as to satisfy this. There is no need to compensate because it is set. However, when the load group (4) is drastically dropped for some reason during the operation of this system, the output control of the power generation device (3) will not be in time, and the generated power will be consumed by the load group (4). It will exceed the power. At this time, control is performed by controlling the voltage applied to the resistor by the thyristor switch (9) so that the active power (8) detected at the power receiving point does not fall below the set value.
As a result, the active power that cannot be consumed by the load group can be consumed by the resistor (10), and it is possible to prevent the power from being sent from the interconnection point to the system in any case. The time rating of this resistor may be a small size because it may be a short time until the output control of the power generator operates. The method of controlling the thyristor switch is not particularly essential to the present invention, and therefore is omitted here.

As described above, in the above embodiment, the measuring instrument (8) for detecting the active power is added with the active power consuming device using the series circuit of the thyristor switch and the resistor, and the active power consuming device is connected at the interconnection point. In any case, by controlling the active power so that it does not fall below the set value, the power is fed to the grid side (3) grid side of the technical requirements for grid connection (so-called reverse power flow).
A distributed power system is obtained that satisfies the above requirements. (Other embodiments)

In the embodiment described above, a device using a series circuit of a thyristor switch and a resistor is used as a device capable of controlling the amount of active power consumed, but an example using a thyristor rectifier and a resistor is used. Is shown in FIG. As a method of controlling the active power to be compensated, it was assumed that a measuring instrument for measuring the received active power was added to the interconnection point and that the value was kept below a certain value. It is also possible to apply a method of measuring the generated power and the power consumption of the load group and controlling using the difference between them.

[0014]

As described above, in the distributed power system of the present invention, it is possible to compensate for reverse power flow in any case, and it is possible to satisfy the technical requirements for grid interconnection. As a result, it is possible to obtain a highly reliable system in which the power generator and the load group are cut off from the power system due to the occurrence of an unexpected reverse power flow, etc., and no blackout occurs.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

FIG. 3 is a configuration diagram showing a conventional distributed power system.

[Explanation of symbols]

 1 ... Electric power system 2 ... Power receiving breaker 3 ... Generator 4 ... Load group 5 ... Device capable of controlling active power consumption 6 ... Meter current transformer 7 ... Meter transformer bag 8 ... Measuring active power Measuring instrument 9 ... Thyristor switch device 10 ... Resistor 11 ... Thyristor rectifier

Claims (4)

[Claims] 1. A power generator and a load group connected to an electric power system, means for detecting active power at the connection point, and a load device for controlling the amount of active power consumed. And a distributed power system. 2. The distributed power system according to claim 1, wherein a load device for controlling the consumption of active power is a thyristor switch and a resistor connected in series. 3. The distributed power system according to claim 1, wherein a thyristor rectifier and a resistor connected to a DC circuit of the thyristor are used as a load device for controlling the amount of active power consumed. 4. The distributed power system according to claim 1, wherein the output of the power generator and the power consumption of the load group are detected as active power for controlling the power consumption.