JP2000341860A - Power storage apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage apparatus capable of dealing not only with the short-period variations in the loads of power consumers but also with the long-period variations of the effective powers of the power consumers. SOLUTION: Between a power-system power supply 2 and a load 3, there are provided on the DC side of a first power converter 5 connected with the power supply 2 via a linking transformer 4 a charging/discharging capacitor 6 for compensating the reactive power of the load 3, and provided on the DC side of a second power converter 8 connected with the power supply 2 via the linking transformer 4 a charging/discharging battery 9, for leveling the effective power of the load 3 by the shifting of its peak value with respect to the long-period variation of the load 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power storage device, and more particularly, to a power storage device having both a reactive power compensating function for suppressing a variation in reactive power and a power leveling function for reducing a peak of received power.

[0002]

2. Description of the Related Art For example, large-capacity arc furnaces, electric railway loads,
In power systems with variable loads such as steel rolling loads, the quality of the system power supply (voltage fluctuation, unbalance, power factor) is poor, and reactive power fluctuations occur due to load fluctuations. A compensator is provided between the system power supply and the variable load.

[0003] This reactive power compensator 1 connects a power converter 5 between a system power supply 2 and a load 3 via an interconnection transformer 4 in a power system as shown in FIG. It has a configuration in which a capacitor 6 is provided on the DC side of the converter 5. The power converter 5 operates as a converter when DC power of the system power supply 2 is converted to DC and charges the capacitor 6, and an inverter is used when the DC power charged in the capacitor 6 is converted to AC and supplied to the load 3. Be driven.

[0004] In the reactive power compensator 1 having the above-described configuration, the charging power of the capacitor 6 charged by the initial charging or the like is AC-converted by the inverter operation of the power converter 5, and the AC output from the power converter 5 is converted. Transformer for interconnection 4
Supply to the load 3 through the power supply, the reactive power fluctuation caused by the load fluctuation is suppressed, and the power supply quality (voltage fluctuation,
Imbalance, power factor).

[0005]

However, as described above, the suppression of the reactive power fluctuation executed by the reactive power compensator 1 in order to improve the power supply quality (voltage fluctuation, unbalance, power factor) is as follows. This is due to short-period load fluctuations. on the other hand,
The load fluctuation includes not only the short-period load described above but also a long-period load as seen in, for example, a received power pattern for a day at a power consumer.

[0006] The received power pattern of a power consumer in a day has a characteristic such that the power peaks during a heavy load time period, for example, around 1 PM to 4 PM, and the power consumption pattern at midnight other than the heavy load time period (for example, at 10:00 PM). To 8:00 AM the next day) and during the light load time period (for example, from 8:00 AM to 1:00 PM and from 5:00 PM to 10:00), the received power has no power peak.
As described above, in the electric power consumer, there are a time zone in which the active power consumed by the load peaks and a time zone in which the active power is low. This is not only the received power pattern of the day but also the received power pattern of the year. The same is true for the load fluctuation in a long cycle.

[0007] In addition, as a long-period load fluctuation,
There is an instantaneous voltage drop (hereinafter referred to as a sag) in the power system due to a lightning strike. In the event of a sag, an instantaneous sag occurring in the power system is promptly detected to compensate for the voltage of important load equipment. Power needs to be supplied to the load.

However, the conventional reactive power compensator uses the charging power of the capacitor to suppress the reactive power fluctuation for the purpose of improving the power supply quality (voltage fluctuation, unbalance, power factor). It is only possible to cope with short-period load fluctuations, and as described above, it has been difficult to cope with daily received power patterns at power consumers or long-period load fluctuations during momentary voltage sags.

Accordingly, the present invention has been proposed in view of the above-mentioned problems, and its object is to provide not only short-period load fluctuations but also long-period power patterns such as a received power pattern in a power consumer. An object of the present invention is to provide a power storage device that can cope with a load change.

[0010]

As a technical means for achieving the above object, the present invention provides a first power converter connected between a system power supply and a load via an interconnection transformer. A DC power supply is provided on the DC side of the transformer with a capacitor that is charged and discharged to compensate for the reactive power of the load against short-period fluctuations, and the second power converter connected via the interconnection transformer is provided. On the DC side, there is provided a power storage which is charged and discharged in order to level the active power of the load with a peak shift with respect to long-period fluctuations.

[0011] The power storage device of the present invention has both a reactive power compensating function for suppressing the reactive power fluctuation and a power leveling function for reducing the peak of the received power.

That is, when the load fluctuation is in a short cycle, the charging power of the capacitor is converted to AC by the inverter operation of the first power converter, and the AC output from the first power converter is connected to the interconnection transformer. By feeding the load through
Reactive power fluctuations caused by load fluctuations are suppressed, and power supply quality (voltage fluctuations, unbalance, power factor) is improved.

When the load fluctuation has a long cycle, the charging power of the power storage device is changed to the second power during a time period when the active power is at a peak or when there is an instantaneous drop due to lightning as shown in the received power pattern at the power consumer. AC conversion by the inverter operation of the power converter, and supplying the AC output from the second power converter to the load via the interconnection transformer,
The peak of the received power is reduced to achieve power leveling by peak shift, and it is also used as a measure against sag.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power storage device according to the present invention will be described in detail below. The same or corresponding parts as those in FIG. 3 are denoted by the same reference numerals.

The power storage device 7 of the embodiment shown in FIG.
In the power system, a first power converter 5 is connected between a system power supply 2 and a load 3 via an interconnection transformer 4, and a capacitor 6 is provided on the DC side of the first power converter 5. At the same time, a second power converter 8 is connected via the interconnection transformer 4, and a power storage, for example, a battery 9 as a secondary battery is provided on the DC side of the second power converter 8. It has a configuration.

The first power converter 5 and the capacitor 6
Exhibits a reactive power compensation function that suppresses reactive power fluctuations.
The first power converter 5 operates as a converter when the AC power from the system power supply 2 is DC-converted to charge the capacitor 6, and the DC power charged in the capacitor 6 is AC-converted and supplied to the load 3. In this case, the inverter is operated. The capacitor 6 charges and discharges power in response to a short-period load change such as a reactive power change.

Further, the second power converter 8 and the battery 9 exhibit a power leveling function of reducing the peak of the received power. When charging the battery 9 by converting the AC power from the system power supply 2 to DC, the second power converter 8 operates as a converter. The DC power charged in the battery 9 is converted to AC and supplied to the load 3. In this case, the inverter is operated. Further, the battery 9 charges and discharges power in response to a long-period load change such as a received power pattern or an instantaneous drop at a power consumer.

In the power storage device 7 of the present invention, the first power converter 5 and the capacitor 6 having a reactive power compensation function for suppressing the reactive power fluctuation use the charging power of the capacitor 6 charged by the initial charging or the like for the first time. 1 power converter 5
AC conversion by the inverter operation of the power converter 5
The AC output from the power supply is supplied to the load 3 via the interconnection transformer 4, thereby suppressing the reactive power fluctuation caused by the load fluctuation and improving the power supply quality (voltage fluctuation, unbalance, power factor). .

Here, as shown in FIG. 2, the received power pattern of a power consumer in a day has such a characteristic that the power peaks during a heavy load time period, for example, around 1 to 4 PM. Note that there is a system for setting a low power rate at midnight (for example, from 10:00 PM to 8:00 AM the next day).

As shown in the long-period load fluctuation, that is, as shown in the received power pattern at the power consumer, late night and light load time periods (for example, 8:00 AM to 1 PM, PM5 At about 10:00 to about 10:00), the battery 9 is charged, and a heavy load time period (for example, around PM1 to 4:00 PM) is a time period during which the active power reaches a peak.
Then, the charging power A of the battery 9 is discharged, the discharging power B of the battery 9 is converted to AC by the inverter operation of the second power converter 8, and the AC output from the second power converter 8 is connected. By supplying the load 3 via the system transformer 4, the peak of the received power is reduced, and power leveling by peak shift is realized. Thus battery 9
The peak power of the discharge power B is shifted to a low power charge time zone in the middle of the night to reduce the contract power charge and to obtain the difference between the day and night power charges.

It can also be used as a countermeasure for a long-period load fluctuation other than the received power pattern at the power consumer, for example, a momentary voltage drop in the power system due to a lightning strike or the like. It is also possible to quickly detect a sag occurring in the power system and supply power to the load 3.

[0022]

According to the present invention, the load on the DC side of the first power converter connected between the system power supply and the load via the interconnection transformer is protected against short-period fluctuations. A capacitor that is charged and discharged to compensate for the reactive power, and includes, on the DC side of a second power converter connected via the interconnection transformer, active power of a load with respect to long-term fluctuations. Not only the reactive power compensation function to suppress the reactive power fluctuation but also the power leveling function to reduce the peak of the received power by equipping the power storage that is charged and discharged to level the power with the peak shift .

Therefore, when the load fluctuation is a short cycle like the reactive power fluctuation, the power quality (voltage fluctuation, unbalance, power factor) can be improved by suppressing the reactive power fluctuation, and Even if the load fluctuation seen in the received power pattern at the power consumer has a long cycle, the peak of the received power can be reduced by the charging power of the power storage and the power leveling by the peak shift can be realized. It can also be used as such, and its practical value is great.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a power storage device according to the present invention.

FIG. 2 is a characteristic diagram showing a day's received power pattern in a power consumer.

FIG. 3 is a configuration block diagram illustrating an example of a reactive power compensating device.

[Explanation of symbols]

 2 System power supply 3 Load 4 Interconnection transformer 5 First power converter 6 Capacitor 7 Power storage device 8 Second power converter 9 Power storage

Claims (1)

[Claims] 1. A method for compensating a reactive power of a load on a DC side of a first power converter connected between a system power supply and a load via an interconnection transformer. The active power of the load is leveled by a peak shift on the DC side of the second power converter connected through the interconnection transformer, with respect to long-term fluctuations. A power storage device comprising a power storage device that is charged and discharged for power saving.