JPH04289732A - Reactive power compensator - Google Patents

Abstract

PURPOSE:To compensate reactive power, higher harmonics and reverse power flow at the time of connecting a distributed power supply to a power system. CONSTITUTION:An active-filter type reactive power compensator 13 which is connected to a power system 1 in the same manner as a generator 3 and a group of loads 4 has such a structure that a device for controlling a consumption quantity of reactive power 6 may be added to a dc circuit of the reactive power compensator 13. The device for controlling a consumption quantity of reactive power is constituted of, for example, a step-up chopper circuit and a resistor.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive power compensator installed in a customer who operates a distributed power source connected to an electric power system.

0002

[Background Art] Recently, the development of power generation technology using natural energy such as sunlight and wind power has been progressing. Many of them are of medium or small capacity, and are connected to the power grid as a distributed power source. This is a so-called distributed power source. Recently, when these distributed power sources are integrated into a power system, technical requirements have been set that must be met in order to avoid adverse effects on the power system, so-called technical requirements for grid interconnection. The main technical requirements include (1) maintaining the power factor at the interconnection point to 0.85 or higher; (2) ensuring that the overall harmonic current distortion rate is 5% or less and each order is 3% or less. to do, (3
) There is a need for a compensation device to satisfy these requirements, such as not allowing power to flow into the grid (not causing so-called reverse power flow), etc.

In order to maintain a high power factor at the interconnection point, a reactive power compensator is often used, and recently, with advances in power electronics, active filter type devices that also have the function of compensating for harmonic currents are being used. reactive power compensators have come into use. but,
A compensation device for preventing reverse power flow is a new technical issue, and effective configurations are currently being explored and studied.

FIG. 2 shows an example of a system configuration having a distributed power source installed at a general consumer. In Figure 2, (1
) is a power system, (2) is a power reception breaker, (3) is a distributed power generator, (4) is a load group, and (5) is an active filter type reactive power compensator. Further, the power receiving point has measuring instruments (9) and (10) for measuring active power and reactive power from a measuring current transformer (7) and a measuring transformer (8). In this example, the reactive power compensator (5) is operated to maintain the power factor at the power receiving point at 0.85 or higher in accordance with the operating conditions of the generator (3) and load group (4). Also,
The active filter type reactive power compensator (5) can compensate for harmonic current waveform distortion by inputting the current waveform of the instrument current transformer (7).

[0005] In normal operation, the output of the generator (3) is within a range that does not exceed the power consumed by the load group (4) in order to use the input natural energy as effectively as possible. It is often controlled to the maximum at this operating range, and reverse power flow does not occur within this operating range. However, for example, if the operating capacity of load group (4) suddenly decreases, the generator (
The generated power in step 3) exceeds the load capacity, and the power is poured into the power system (1) until the output control of the generator is activated. In this case, the protective relay system (not shown in FIG. 2) at the interconnection point detected the reverse power flow, causing the power receiving breaker (2) to trip, leading to a system shutdown.

[0006]

SUMMARY OF THE INVENTION As described above, the conventional system having a distributed power source installed in a general consumer has the following problems. In other words, among the technical requirements for grid interconnection, reactive power and harmonics can be effectively compensated for by a reactive power compensator, but for reverse power flow, when reverse power flow occurs due to a sudden decrease in load, etc., it is difficult to compensate for it. Without a compensating device, the protective relay system detected reverse power flow, tripping the incoming circuit breaker and shutting down the entire system.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reactive power compensator that solves the above-mentioned problems, compensates not only reactive power and harmonics but also reverse power flow in any case, and satisfies the technical requirements for grid interconnection. Our goal is to provide the following. [Structure of the invention]

[0008]

[Means for Solving the Problems] The present invention provides an active filter type reactive power compensator connected to a power system together with a generator and a load group, in which a device for controlling active power consumption is added to the DC circuit. The configuration is as follows.

0
009]

Operation: During normal operation, the output of the generator is configured or controlled to match the amount of the load group. However, if a large dropout of a load group occurs for some reason, the output control of the generator will not be able to be done in time, and the generated power will exceed the power consumption of the load group. At this time, this excess power is consumed by a device of the active filter type reactive power compensator that consumes active power added to the DC circuit. This prevents power from being sent to the grid from the power receiving point.

0010

Embodiment (Structure of Embodiment) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, (1) is the power system, (2) is the power receiving breaker, (3) is the generator such as a fuel cell or solar cell, (4) is the load group, and (5) is the active filter type. The reactive power compensator (6) is a device that controls the amount of active power consumed. In this embodiment, a boost chopper device (11) and a resistor (1
2) The configuration uses a series circuit. (Operation of the embodiment) Next, the operation of the above embodiment will be explained.

[0012] Normally, in a general consumer system having a distributed power source, the output of the generator (3) is designed to use the input natural energy as effectively as possible with respect to the power consumed by the load group (4). Consider this and control power consumption to the maximum within a range that does not exceed it. At this time, the power factor and harmonic current distortion at the connection point with the power grid (1) are determined by the operating state of the generator (3) and the operating state of the load group (4). these are,
Compensation is performed using an active filter type reactive power compensator (5), and among the technical requirements for grid connection, the power factor at one grid connection point must be maintained at 0.85 or more, and the total two-harmonic current distortion rate should be 5%.
The following two points can be satisfied: each order should be 3% or less. Another technical requirement for grid interconnection is that power should not flow into the three grids (so-called reverse power flow), so it is necessary to compensate in particular because the operating conditions are set to meet these requirements during normal operation. There is no.

However, when operating this system,
If a large dropout of the load group (4) occurs for some reason, the output control of the generator (3) will not be adequate, and the generated power will exceed the power consumption in the load group (4). At this time, this excess power is consumed by the resistor (12) so as not to flow out to the grid (1). The amount of power consumed by this resistor is controlled by controlling the voltage applied to the resistor by a boost chopper device (11). This makes it possible to prevent power from being sent to the grid from the power receiving point under any circumstances.

Furthermore, at this time, since the active filter type effective power compensator controls the DC circuit voltage to be kept constant, the influence of this effective power control is automatically compensated for. The control function of the reactive power compensator is not affected at all.

[0015] The time rating of this resistor (12) may be a short time until the output control of the generator (3) is activated, so it may be small. Regarding the control method of the boost chopper device (11), in this embodiment, it is assumed that by measuring the active power at the power receiving point, control is performed so that the value of the received active power does not fall below a set value. There is. (
Effects of Examples)

As explained above, in the above embodiment, an active power consumption device using a series circuit of a boost chopper device and a resistor is added to the DC circuit of the active filter type reactive power compensator, so that the Even in cases where the grid is interconnected, the technical requirements for grid connection include maintaining the power factor at one interconnection point at 0.85 or higher, not allowing power to flow into the second grid (not causing so-called reverse power flow), and preventing third harmonics. A small, low-cost reactive power compensator that satisfies the current distortion ratio of 5% or less overall and 3% or less for each order can be obtained, and is extremely effective for general demand systems with distributed power sources. Become. (Other examples)

In the embodiment described above, a series circuit of a boost chopper device and a resistor is used as a device capable of controlling the consumption amount of active power added to the DC circuit of an active filter type reactive power compensator. However, depending on the control range, it goes without saying that a buck-boost chopper device and a resistor may also be used. In addition, as a method of controlling the active power to be compensated, we assumed a configuration in which a measuring device for measuring the received active power was added to the power receiving point, and control to maintain the value above a certain value. It goes without saying that a method of measuring the power consumption of a load group and controlling it using the difference between them can also be applied.

[0018]

As described above, by using the reactive power compensator according to the present invention, not only reactive power and harmonics but also reverse power flow can be compensated for in any case, and the reactive power compensator according to the present invention can be used to compensate for reverse power flow as well as for reactive power and harmonics, and can satisfy the technical requirements for grid interconnection. This means that a power compensation device can be provided. As a result, in general consumer systems with distributed power sources, it is possible to obtain a highly reliable system that will not be cut off from the power grid and cause a total power outage due to unexpected reverse power flow. It will be possible.

[Brief explanation of the drawing]

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

FIG. 2 is a configuration diagram showing an example of a conventional system having a distributed power source installed in a general consumer.

[Explanation of symbols]

1...Power system
2... Power receiving breaker 3... Generator
4...Load groups 5, 13...Reactive power compensator 6...Device for controlling active power consumption 7...Measurement current transformer 8
...Instrument transformer 9...Measuring device for measuring active power
10...Measuring instrument for measuring reactive power

Claims (1)

[Claims] [Claim 1] In an active filter type reactive power compensator connected to a power system together with a generator and a load group, a device for controlling active power consumption is added to the DC circuit of the reactive power compensator. A reactive power compensator characterized by: