JP2001161030A - Battery power storage system for dc power distribution system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and cost of a battery power storage system which injects the electric power from a secondary battery into the DC bus of a DC power distribution system. SOLUTION: In a battery power storage system which injects the electric power from a secondary battery 20 charged by means of an AC system 1 into the DC bus 5 of the DC power distribution system connected to the system 1, a power converter 21 is constituted of an inverter 22 which makes high-frequency conversion on the output voltage of the battery 20, a transformer 23 which boosts the output of the inverter 22, and a rectifier 24 which rectifies the output of the transformer 23 and electric power is injected into the bus 5 from the battery 20 by adjusting the output voltage of the rectifier 24 by controlling the output voltage of the inverter 22 based on the power fluctuation in the bus 5. Since the frequency of the inverter 22 is raised, the capacity, size, and cost of the power converter 21 are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery power storage system for suppressing a power peak supplied from an AC system to a DC distribution system of an electric railway or the like and leveling the received power of the DC distribution system.

[0002]

2. Description of the Related Art In an electric railway, the power consumption generally rises during the rush hour hours (heavy load) in the morning and evening, and the power consumption sharply increases. Become smaller. Therefore, when the load is heavy, the power of a specific secondary battery is injected into the DC feeder of the electric railway, and when the load is light, the secondary battery is charged from the power system on the DC feeder side. Has been researched and developed as a battery power storage system for DC electric railways by suppressing the power peak of As shown in FIG.

[0003] The battery power storage system of FIG. 3 is a system in which a secondary battery 7 is connected to a DC feeder line 5 supplied with power from an AC system 1 such as a substation via a power converter of a chopper circuit 8. An AC system 1 is connected to a DC feeder 5 via a DC feeder transformer 2, a rectifier 3, and a DC reactor 4.
And a DC distribution system of a DC electric railway that drives the train load 6. An AC voltage of several thousand volts transmitted from the AC system 1 is applied to the transformer 2 by, for example, 750V to 1V.
The DC power is reduced to 500 V, rectified by the rectifier 3 and smoothed by the DC reactor 4 and supplied to the DC feeder 5.

A secondary battery charging transformer 11, a rectifier 12, and a DC reactor 13 are connected between the secondary battery 7 and the AC system 1. Charged to about. Secondary battery 7
A chopper circuit 8 is connected between the output (discharge) terminal and the DC feeder 5. The chopper circuit 8 transforms the DC output voltage of the secondary battery 7 by intermittently controlling the semiconductor switching element S to adjust the power injected (discharged) into the DC feeder line 5. With this power adjustment, the operation of suppressing and leveling the power peak of the DC feeder line 5 is performed. Although the chopper circuit 8 in FIG. 3 has a step-down chopper configuration, it may have a step-up chopper configuration. The chopper circuit 8 includes, in addition to the semiconductor switching element S, an LC filter including a reactor L and a capacitor C for suppressing a current ripple and a voltage ripple generated during a chopper operation.

[0005] The operation of the chopper circuit 8 described above is controlled by a chopper control circuit 17. For example, the instrument transformer 15 detects power supplied from the AC system 1 to the DC feeder line 5, the demand monitoring device 16 monitors this detection signal, and outputs a charge / discharge timing signal to the chopper control circuit 17. When the DC feeder line 5 is heavily loaded, the chopper circuit 8 performs a secondary battery discharging operation, and when the DC feeder line 5 is lightly loaded, the chopper circuit 8 stops and the secondary battery is charged.

[0006]

SUMMARY OF THE INVENTION In a battery power storage system in which the DC voltage of a secondary battery is transformed by the switching action of a chopper circuit and injected into a DC feeder line, the semiconductor switching element of the chopper circuit converts the DC voltage into a DC feeder voltage. A high withstand voltage element having a corresponding rated voltage is required, and a large and expensive semiconductor switching element is required. Also, regardless of whether the chopper circuit is a step-down chopper or a step-up chopper, a voltage difference between the secondary battery voltage and the DC feeder voltage is large, and a reactor for suppressing a current ripple component generated in accordance with the voltage difference. In addition, it is necessary to use a large-size, high-cost filter having a large capacity for the LC filter, and there has been a problem that the power conversion device for converting the output of the secondary battery into an alternating current becomes large in size and high in cost.

It is an object of the present invention to reduce the size of a battery power storage system of a secondary battery specification which suppresses a power peak of a DC distribution system of a DC electric railway or the like to level power.
It is to realize cost reduction.

[0008]

Technical means for achieving the above object of the present invention is to provide a power conversion device by connecting a secondary battery charged by an AC system to a DC bus of a DC distribution system connected to an AC system. Battery storage system connected via
An inverter for converting the output voltage of the secondary battery into an alternating current, an inverter output transformer having a primary winding connected to the output of the inverter, and a secondary winding and a DC bus of the transformer. It consists of an inverter output rectifier connected in between, and controls the inverter output voltage based on the power fluctuation of the DC bus of the DC distribution system to adjust the output voltage of the inverter output rectifier. It is characterized in that the power injected into the DC bus is controlled.

Here, the inverter disposed between the secondary battery and the DC bus constitutes a variable DC voltage source by converting the output voltage of the secondary battery into an alternating current. It is possible to reduce the size of the transformer on the side and to suppress the voltage ripple at the output of the rectifier for inverter output.

In particular, when the inverter is a high-frequency inverter that greatly exceeds the commercial frequency as in the invention of claim 3, it is possible to further reduce the size of the inverter output transformer and suppress the ripple component.

Also, as in the invention of claim 2 of the present invention,
By connecting the secondary battery output and the output of the inverter output rectifier in series, the inverter output voltage can be reduced by the secondary battery voltage, and the inverter and its output side transformer,
The rectifier can be reduced in capacity and size.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention is shown in FIG. 1 and the second embodiment is shown in FIG.
1 and 2 are applied to the DC power distribution system of the DC electric railway shown in FIG. 3 for the same purpose as the battery power storage system shown in FIG. 3, and the same or corresponding parts as those in FIG. The description is omitted by attaching reference numerals.

The battery power storage system of FIG. 1 includes a DC feeder (DC bus) 5 of a DC electric railway connected to an AC system 1 via a transformer 2, a rectifier 3, and a DC reactor 4.
The secondary battery 20 charged by the AC system 1 is connected to the power converter 2
1. The power converter 21
Inverter 22 that converts the output voltage of secondary battery 20 into AC
And an inverter output transformer 23 having a primary winding connected to the output of the inverter 22, and an inverter output rectifier 2 connected between the secondary winding of the transformer 23 and the DC feeder 5.
4 is provided. The secondary battery 20 is connected to the AC system 1 as necessary.
For example, when the AC voltage of the AC system 1 is 5
The secondary battery is charged through a secondary battery transformer 31 that steps down to about 00 V, a secondary battery rectifier (diode rectifier, thyristor rectifier, etc.) 32 that rectifies the stepped-down alternating current, and a secondary battery reactor 33. The control of the charging of the secondary battery and the discharging of the secondary battery described below are performed by monitoring the feeder current IL and the feeder voltage VL of the DC feeder 5 one by one.

The inverter 22 is, for example, a high-frequency inverter for converting a DC voltage of the secondary battery 20 into a high frequency of several tens of kHz.
No. 2. The high-frequency inverter 22 and the transformer 23 step-up convert a DC voltage of about 500 V of the secondary battery 20 into a high-frequency AC voltage, and the rectifier 24 rectifies this AC power and injects (discharges) it into the DC feeder line 5. Therefore, the rated voltage of the secondary battery 20 can be designed sufficiently lower than the rated voltage of the DC feeder line 5, and the rated capacity of each circuit element of the power converter 21 including the high-frequency inverter 22 can be designed to be small.

The injection current Ic when the power conversion device 21 performs a discharging operation is determined by the formula (output voltage of the rectifier 24−feeding line voltage) / (internal impedance of the power conversion device 21). It corresponds to the load fluctuation at the time of heavy load of the DC feeder line 5. The timing of the injection of the injection current Ic and the stop of the injection are determined, for example, when the average value (integral value) per unit time of the feeder current IL exceeds a first level set in advance, and the same average value is used. The time when the level falls below the second level set in advance may be set as the injection stop timing. In this case, the first level is set to be higher than the second level.

As described above, by setting the output voltage of the secondary battery 20 to a high-frequency voltage by the high-frequency inverter 22, a small and lightweight high-frequency transformer 23 can be applied. The high-frequency inverter 22 variably adjusts the AC output voltage by performing PWM control (pulse width control) or one-pulse PWM control (conduction width control) that changes the width in one pulse. Therefore, the ripple component included in the output voltage of the rectifier 24 for rectifying the inverter output becomes high frequency, and the ripple current flowing out to the DC feeder line 5 is suppressed. In addition, since the ripple frequency increases, the inverter output transformer 23 Also, it is possible to reduce the capacity and the size of the normally used ripple suppression LC filters (not shown).

In the embodiment shown in FIG.
Is connected to the primary side of the transformer 2 for the feeder rectifier of the AC system 1, but is connected to the secondary side of the low voltage side of the transformer 2 as shown by the broken line connection circuit in FIG. The secondary battery transformer 31 can be reduced in size and weight. This is the same for the second embodiment of FIG. 2 (see the broken line connection circuit of FIG. 2).

The second embodiment of FIG. 2 differs from the embodiment of FIG. 1 in that the output of the secondary battery 20 and the output of the rectifier 24 for the secondary battery are connected in series. In the case of the embodiment of FIG. 2 as well, the secondary battery 20 is charged by the AC system 1, the output voltage of the secondary battery 20 is converted to high frequency by the high frequency inverter 22, rectified by the rectifier 24, and injected into the DC feeder 5. Is done. Here, in the embodiment of FIG.
And the output of the rectifier 24 are connected in series, and the total output power of the secondary battery 20 and the rectifier 24 is injected into the DC feeder line 5. Therefore, the injection current Ic is (output voltage of the secondary battery 20 + output voltage of the rectifier 24). −feeding line voltage) / (power conversion device 21)
Is determined by the equation:

Here, the variation range of the output voltage of the normally used secondary battery 20 with respect to the rated voltage is about ± 25%, and by connecting the output of the rectifier 24 to the output of the secondary battery 20 in series. In addition, the capacity of the power converter 21 can be set smaller by an amount corresponding to the output of the secondary battery. That is, the overall capacity of the power converter 21 in FIG. 1 is (feeder voltage VL) × (injection current Ic), and the overall capacity of the other power converter 21 in FIG. 2 is (feeder voltage VL−secondary). (The battery voltage) × (injection current Ic), and the overall capacity of the power converter 21 in FIG. 2 can be reduced in proportion to the rated voltage of the secondary battery 20, so that the size and cost can be further reduced. Become.

The present invention is not limited to charging and discharging secondary battery power to a DC feeder of an electric railway, but also charging secondary battery power to a DC bus of a DC distribution system having a variable load such as a factory load. The present invention can also be effectively applied to a battery power storage system that suppresses peak power consumption by discharging. As described above, a high-frequency inverter is the best solution for the AC conversion of the secondary battery voltage. However, in a battery power storage system with a relatively low voltage specification, a low-frequency inverter that converts the secondary battery voltage to a commercial frequency is used. It is also possible to use an inverter.

[0021]

According to the present invention, the inverter disposed between the secondary battery and the DC bus serves as a variable DC voltage source that converts the output voltage of the secondary battery into AC and boosts the voltage. It is not necessary to apply a large-voltage element corresponding to the DC bus to each circuit element of the power conversion device including the power conversion device, and it is easy to reduce the size and cost of the power conversion device. Furthermore, as the output frequency of the inverter increases, the size of the transformer for inverter output and the suppression of ripple components in the output of the rectifier for inverter output become easier, and the size and cost of the power converter are further reduced. At the same time, high performance can be achieved by reducing the ripple loss.

Further, by connecting the output of the secondary battery and the output of the rectifier for inverter output in series, the capacity of the entire power converter can be reduced in accordance with the output of the secondary battery.
The power converter can be further reduced in size and cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a battery power storage system according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a battery power storage system according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional battery power storage system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC system 5 DC bus, DC feeder line 20 Secondary battery 21 Power converter 22 Inverter, high frequency inverter 23 Inverter output transformer 24 Inverter output rectifier

Claims (4)

[Claims] 1. A battery power storage system in which a secondary battery charged by an AC system is connected via a power converter to a DC bus of a DC distribution system connected to an AC system, wherein the power converter is An inverter for converting the output voltage of the secondary battery into an AC, a transformer having a primary winding connected to the output of the inverter, and a rectifier connected between the secondary winding of the transformer and a DC bus. A DC distribution system battery comprising: controlling power output from a secondary battery to a DC bus by controlling an output voltage of an inverter based on power fluctuations of the DC bus and adjusting an output voltage of a rectifier. Power storage system. 2. The DC power storage battery power storage system according to claim 1, wherein the secondary battery output and the rectifier output are connected in series. 3. The inverter according to claim 1, wherein the inverter is a high-frequency inverter exceeding a commercial frequency.
The DC power storage battery power storage system as described in the above. 4. The DC power storage battery power storage system according to claim 1, wherein the DC bus is a DC feeder of an electric railway.