JP2001359239A - Voltage fluctuation compensating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage fluctuation compensating device, having measures against higher harmonic and capable of restraining higher harmonic current included in the load current of a system, in addition to measures against voltage fluctuations by a power compensating function. SOLUTION: This voltage fluctuation compensating device restrains voltage fluctuations in a power system linked to a distributed power supply, having power fluctuations due to fluctuations in the output of the distributed power supply with a power converter connected to the power system. The compensating device is attached with a higher harmonic compensating circuit part 34, which has a notch filter 44 of canceling a higher harmonic component included in system current Is with the distributed power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage fluctuation compensator, for example, provided in a power system in which a distributed power source such as a wind power generator or a solar cell is connected to a system power source, and the voltage fluctuation of the power system due to the distributed power source. The present invention relates to a voltage fluctuation compensating device for suppressing the fluctuation.

[0002]

2. Description of the Related Art For example, in a power system in which a distributed power source such as a generator of a wind power generation system or a solar cell of a photovoltaic power generation system is connected to a system power source, the output of the distributed power source is affected by natural conditions such as wind speed and solar radiation. , Or a voltage drop due to an active / reactive current at the time of starting the wind power generator, or a sudden output fluctuation at the time of power generation by the distributed power supply, causing a voltage fluctuation in the power system. Therefore, as one measure against voltage fluctuations in the power system, it is common to install a voltage fluctuation compensating device for suppressing voltage fluctuations in the power system based on output fluctuations of the distributed power supply.

FIG. 3 shows a voltage fluctuation compensator installed in a power system in which two distributed power sources 1 and 2 of a wind power generator and a solar cell are connected to a commercial power source 3. This voltage fluctuation compensating device is schematically constituted by a self-excited inverter 4 circuit-configured with switching elements such as GTO and IGBT and a secondary battery 5 such as a lead battery connected to its DC side as shown in FIG. And a power compensation function for adjusting the voltage by the active / reactive power.

A load 6 is connected between the system power source 3 and the distributed power sources 1 and 2, and the load 6 is connected to the system power source 3.
A circuit breaker 7 is disposed between the two. The solar cell 2 is provided with a DC / AC converter 8.

The self-excited inverter 4 is a bidirectional AC / DC power converter having an inverter function and a rectifying function. The self-excited inverter 4 converts the AC power from the system bus 9 into DC and charges the secondary battery 5, and a secondary operation. The control is switched to an inverter operation in which the DC power charged in the battery 5 is converted to AC and supplied to the system bus 9.

In the voltage fluctuation compensator, a transformer 10 (PT) and a current transformer 11 (C
T), the active power and the reactive power of the distributed power sources 1 and 2 are detected, and the voltage fluctuation of the power system due to the output fluctuation of the distributed power sources 1 and 2 is calculated from the active power and the reactive power. The inverter 4 is controlled by the compensated current command signal.

In other words, by operating the inverter 4 in a rectifying operation or an inverter operation based on the compensation current command signal, a compensation current for canceling a voltage fluctuation from the inverter 4 to the system based on charging and discharging of the secondary battery 5 is generated. The output of the inverter 4 causes the compensation current to be output, thereby suppressing the voltage fluctuation of the power system due to the output fluctuation of the distributed power sources 1 and 2.

[0008]

However, for distributed power sources 1 and 2 such as a wind power generator of a wind power generation system and a solar cell of a photovoltaic power generation system, an inverter device using a semiconductor element such as a thyristor or an IGBT is used. Accordingly, harmonic currents are included in the load current of the electric power system by the distributed power sources 1 and 2, and there is a concern that adverse effects due to various harmonic disturbances may occur.

In view of the above, the present invention has been proposed in view of the above-mentioned problems, and its object is to provide not only a countermeasure against voltage fluctuation by a power compensation function but also a harmonic current contained in a load current of a system. It is an object of the present invention to provide a voltage fluctuation compensating device in which harmonic countermeasures can be taken.

[0010]

According to a first aspect of the present invention, as a technical means for achieving the above object, a power converter is connected to a power system in which a distributed power supply having a power fluctuation is interconnected, In a voltage fluctuation compensating device for suppressing a voltage fluctuation of an electric power system due to an output fluctuation of the distributed power supply, a harmonic compensation circuit unit for canceling a harmonic component included in a system current by the distributed power supply is additionally provided. .

According to the present invention, by providing a harmonic compensating circuit for canceling a harmonic component contained in the system current by the distributed power supply, the power compensating function for adjusting the voltage by the active / reactive power provides a harmonic compensating function by the distributed power supply. An active filter function for canceling the wave current can be added. The addition of the active filter function makes it easier to suppress harmonics caused by the distributed power supply.

The harmonic compensating circuit has a notch filter for removing a fundamental component from the system current, and extracts the harmonic component from the output of the notch filter. It is desirable to configure. In the harmonic compensation circuit, a fundamental component is removed from the system current by a notch filter to extract a harmonic component, and a compensation current that cancels the harmonic component is output.

It is preferable that the distributed power source is composed of a plurality of solar power generation systems and wind power generation systems. With such a configuration, a plurality of distributed power sources can be compensated collectively for harmonic countermeasures, and practicality can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a voltage fluctuation compensator according to the present invention will be described in detail below. In the following embodiment, a case will be described in which two distributed power sources, a wind power generator of a wind power generation system and a solar cell of a photovoltaic power generation system, are connected to a system, but the present invention is not limited to this. However, the present invention is also applicable to a case where one or three or more distributed power sources are connected to a system.

FIG. 1 shows a power system in which two distributed power sources 21 and 22 of, for example, a wind power generator and a solar cell are connected to a commercial system power source 23. An embodiment in which a voltage fluctuation compensating device is installed as one of measures against a failure will be described. FIG. 2 is a control block diagram of a voltage fluctuation compensator for exhibiting a power compensation function as a measure against voltage fluctuation and an active filter function as a measure against harmonics.

As shown in FIG. 1, this voltage fluctuation compensating apparatus is composed of a self-excited inverter 24, which is composed of switching elements such as GTO and IGBT, and a secondary battery 25, such as a lead battery, connected to its DC side. Has been
Two functions are exhibited: a power compensation function for adjusting voltage with active / reactive power and an active filter function for canceling harmonic currents caused by the distributed power sources 21 and 22.

The system power supply 23 and the distributed power supplies 21 and 22
, A load 26 is connected, and a circuit breaker 27 is disposed between the load 26 and the system power supply 23.
Further, the solar cell 22 is provided with a DC / AC converter 28.

This voltage fluctuation compensating apparatus includes a self-excited inverter 24 having both a power compensating function and an active filter function, and includes a power compensating circuit section 33 and a harmonic compensating circuit section 34 as shown in FIG. The inverter 24 is configured to be controlled. The self-excited inverter 24 is a bidirectional AC / DC power converter having an inverter function and a rectifying function. The self-excited inverter 24 converts the AC power from the system bus 29 to DC and charges the secondary battery 25.
The control is switched to an inverter operation in which the DC power charged in the DC power supply 5 is converted to an AC power and supplied to the system bus 29.

In the power compensation circuit section 33, the system bus 2
9 based on the system voltage V _S and system current I _S detected by the transformer 30 (PT) and the first and second current transformers 31 and 32 (CT ₁ , CT ₂ ). ,
22 active power P and reactive power Q
5 and the reactive power calculator 36. The load current I _L and the second current transformer 3 which is detected by the first current transformer 31
By generating the system current I _S is calculated by the subtracter 47 a difference between the inverter output current I _INV detected by 2, distributed power supply 2 that are the subject of harmonic compensation and power compensation
Only the output currents 1 and 22 are extracted.

The active power P and the reactive power Q output from the active power calculator 35 and the reactive power calculator 36 are multiplied by predetermined gains K _P and K _Q by gain adjusters 37 and 38 to adjust both gains. The outputs of the devices 37 and 38 are added by an adder 39, and the reference sine wave signal S is multiplied by a multiplier 40, thereby coping with the voltage fluctuation of the power system due to the output fluctuation of the distributed power sources 21 and 22. Generate an output current signal.

On the other hand, in the harmonic compensation circuit section 34, the load current I _L detected by the first current transformer 31 and the second current transformer 3
The difference from the inverter output current I _INV detected in step 2 is calculated by the subtractor 47, so that only the output currents of the distributed power supplies 21 and 22 to be subjected to harmonic compensation are obtained. inputting a I _S to the notch filter 44.

In the notch filter 44, the system current I
Remove only the fundamental wave component of 50Hz or 60Hz in _S, and extracts the harmonic components included in the system current I _S. The harmonic signal extracted by the notch filter 44 is multiplied by a predetermined gain K _H by a gain adjuster 45, and the harmonic signal output from the gain adjuster 45 is output from the multiplier 40 of the power compensation circuit unit 33. The output current signal to be output is added by the adder 46.

As a result, the amount of voltage fluctuation of the power system can be reduced.
The output current signal corresponding to the
Generate a superimposed signal by adding the harmonic signal corresponding to the harmonic
You. This superimposed signal is inverted in polarity by the polarity converter 41.
The inverted signal and the system voltage V _SAnd based on the output current
A control signal is generated by the control unit 42 and based on the control signal.
From the switching pulse generator 43.
Outputs a loose signal. This switching pulse signal
ON / OFF of the switching element of the inverter 24
Then, the operation of the inverter 24 is controlled.

The superimposed signal obtained by adding the output current signal and the harmonic signal output from the power compensation circuit unit 33 and the harmonic compensation circuit unit 34 and inverting the polarity of the added signal is the voltage of the power system. A power compensation current that cancels out fluctuations is added with a harmonic compensation current that cancels out harmonics of the distributed power supply. The output fluctuation of the distributed power sources 21 and 22 is suppressed by the power compensation current output from the inverter 24 based on the charging and discharging of the secondary battery 25, and the harmonics by the distributed power sources 21 and 22 are suppressed by the harmonic compensation current. I do.

[0025]

According to the present invention, a power converter is connected to a power system in which distributed power supplies with power fluctuations are interconnected, and voltage fluctuation compensation for suppressing voltage fluctuations in the power system due to output fluctuations of the distributed power supplies. In the apparatus, by providing a harmonic compensation circuit unit for canceling a harmonic component included in the system current by the distributed power supply, a power compensation function for adjusting voltage by active / reactive power provides a harmonic current by the distributed power supply. An active filter function to cancel can be added. By adding this active filter function, it is not necessary to separately provide a harmonic countermeasure device such as an active filter, and the voltage fluctuation compensator can easily realize not only the voltage fluctuation of the power system but also the harmonics generated by the distributed power supply. Thus, it is possible to provide a high added value voltage fluctuation compensating device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example in which a voltage fluctuation compensator is installed in a power system according to an embodiment of the present invention.

FIG. 2 is a control block diagram of the voltage fluctuation compensating apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional example of a voltage fluctuation compensation device installed in a power system.

[Explanation of symbols]

 21, 22 Distributed power supply 23 System power supply 34 Harmonic compensation circuit unit 44 Notch filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02M 7/48 H02M 7/48 RF term (Reference) 5G066 DA04 DA08 EA03 FA01 FB13 FC12 5H007 AA08 BB07 CB03 CC03 DA06 DC02 DC05 5H420 CC03 DD03 EB39 FF03 FF04 FF06 FF07 FF24 5H740 BB08 NN03

Claims (3)

[Claims] 1. A voltage fluctuation compensator for connecting a power converter to a power system in which distributed power sources with power fluctuations are interconnected and suppressing voltage fluctuations in the power system due to output fluctuations of the distributed power source. A voltage fluctuation compensating device further comprising a harmonic compensating circuit for canceling harmonic components contained in the system current. 2. The system according to claim 1, wherein the harmonic compensation circuit has a notch filter for removing a fundamental component from a system current, and extracts a harmonic component from an output of the notch filter. The voltage fluctuation compensator according to the above description. 3. The voltage fluctuation compensator according to claim 1, wherein the distributed power source includes a plurality of solar power generation systems and wind power generation systems.