JP2003274670A - Ac power source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an efficiency by reducing a loss to a lowest limit by decreasing an operating period of a chopper for voltage change compensating of a capacitor, and to reduce in size and cost the chopper and an overall AC power source device by suppressing a maximum voltage conversion ratio of the chopper. <P>SOLUTION: The power source device comprises a switch 5 for short circuiting an input side and an output side of the chopper 2, a switch controller 6 for turning on the switch 5 to directly connect a capacitor 1 to an inverter 3 by the controller 6 if the voltage of the capacitor 1 falls within a DC side rated voltage of the voltage inverter 3, and stopping the operation of the chopper 2. In this case, if the voltage of the capacitor 1 is out of the range of the DC side rated voltage of the inverter 3, the switch 5 is opened by the controller 6 to operate the chopper 2 connected between the capacitor 1 and the inverter 3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alternating current equipped with an inverter capable of forward / reverse conversion, a capacitor as a storage element, and a chopper interposed between the inverter and the capacitor for bidirectionally transferring DC power. It relates to a power supply device.

[0002]

2. Description of the Related Art FIG. 2 shows a prior art of an AC power supply device of this type. In FIG. 2, reference numeral 1 denotes a large-capacity capacitor such as an electric double layer capacitor (electric double layer capacitor), both ends of which are connected to a DC terminal of a voltage source inverter 3 via a chopper 2. An AC power supply 4 is connected to the AC terminal of the voltage source inverter 3.

The voltage source inverter 3 is usually an AC power source 4
DC power is supplied to the chopper 2 by a forward conversion operation for converting the AC power into DC power, and the chopper 2 turns on and off the internal semiconductor switching element to perform DC-DC conversion to generate a predetermined voltage and current. Output and charge capacitor 1. Further, the voltage source inverter 3 performs an inverse conversion operation of converting DC power into AC power as necessary, converts DC power of the capacitor 1 via the chopper 2 into AC power, and can regenerate the AC power supply 4. Has become.

Further, in this AC power supply device, for example, when the AC power supply 4 fails, the inverter 3 supplies the DC power of the capacitor 1 to the load (not shown) connected to the AC side of the voltage source inverter 3. The operation of supplying power after converting to electric power, or supplying electric power to the AC side for the purpose of leveling various loads connected to the AC power source 4 and compensating for output fluctuations of the natural energy power generation device such as solar cells The capacitor 1, the chopper 2, and the voltage source inverter 3 constitute a kind of power storage device as a whole. Here, the electric double layer capacitor is advantageous in that it can be charged and discharged rapidly and with a large current, has a high charge and discharge efficiency, and has a long life, and is becoming popular as a DC power storage element in recent years.

In the above structure, the voltage of the capacitor 1 changes as it is charged and discharged. Since the energy stored in the capacitor 1 is proportional to the square of the voltage, for example, when the voltage is discharged to 50% of the fully charged voltage (hereinafter referred to as the maximum voltage), 75% of the stored energy is
In addition, when discharged up to 25% of the maximum voltage, 93.75% of the stored energy is released.

In order to utilize the capacity of the capacitor 1 as effectively as possible, it is necessary to increase the fluctuation range of the voltage so that most of the stored energy is discharged. However, the voltage of the capacitor 1 is the maximum voltage. Assuming that the discharge is performed up to 25%, the capacitor 1 and the inverter 3 are connected to the chopper 2
In a system that is directly connected without the intermediary of the above, it is necessary to set the minimum value of the voltage of the capacitor 1 (25% of the maximum voltage) to a value at which the specified AC voltage peak value can be output by the inverter 3. Therefore, when the voltage of the capacitor 1 is maximum, the DC voltage value of the inverter 3 that is equal to this is 4 (= 100% / 25%) times the AC voltage peak value defined above.

Thus, the capacitor 1 and the inverter 3
In the case of directly connecting and, in order to output a predetermined AC voltage from the inverter 3 regardless of the voltage of the capacitor 1, it is necessary to increase the DC-side rated voltage of the inverter 3, and as a result, high withstand voltage parts are required. become. Generally, these parts have large losses and are expensive, which leads to a reduction in efficiency of the device and an increase in price.

The chopper 2 connected between the capacitor 1 and the inverter 3 is for solving the above problem, and is constituted by a circuit called a so-called bidirectional chopper. According to this bidirectional chopper, it is possible to bidirectionally convert the DC power and transfer the power from the capacitor 1 to the inverter 3 or from the inverter 3 to the capacitor 1, and the inverter 1 is compensated for the voltage fluctuation of the capacitor 1. The DC voltage of 3 can be kept almost constant.

By interposing the chopper 2 in this way, the fluctuation of the DC voltage of the inverter 3 is reduced, and the withstand voltage duty imposed on the components of the inverter 3 is also reduced. Further, when the capacitor 1 and the inverter 3 are directly connected, it is necessary to increase the voltage of the capacitor 1 for the reason described above. Therefore, a large number of low withstand voltage storage elements are normally connected in series to obtain a voltage value. However, by increasing the voltage of the capacitor 1 by the chopper 2 and supplying the voltage to the inverter 3, the number of series elements of the storage elements in the capacitor 1 can be reduced to simplify the circuit configuration, reduce the weight, and reduce the cost. it can.

[0010]

As described above, the use of the chopper 2 can reduce the responsibility imposed on the components of the inverter 3 and the number of series elements of the capacitor 1, but on the other hand, the chopper does not. 2 Current loss due to continuous operation,
New problems such as switching loss and inductive interference due to electromagnetic noise will occur. The maximum voltage conversion ratio of the chopper 2 is 25%: 100% when viewed from the side of the capacitor 1,
The use of a reactor having a large inductance corresponding to the conversion ratio causes the chopper 2 to be upsized and the price to be increased.

When a lead storage battery is used as a storage element instead of the capacitor 1 and the lead storage battery is directly connected to the inverter 3 without a chopper, the minimum voltage of the lead storage battery is about 70% of the maximum voltage. I'm using it.
Therefore, the maximum value of the DC voltage of the inverter 3 set to output the AC voltage having the same peak value as the minimum voltage when the voltage of the lead storage battery is the minimum is (100% / 70%) times and capacitor 1
Of the system that directly connects the inverter and the inverter 3 (100% / 2
5%) times the maximum value is lower.

In view of the above points, the present invention shortens the operating period of the chopper to minimize its loss, improves the efficiency as compared with the prior art, and provides a DC side rated voltage equivalent to that when a lead storage battery is used. It is an object of the present invention to provide an AC power supply device in which the maximum voltage conversion ratio of the chopper is suppressed by using the inverter provided, and the chopper and the entire device can be downsized and the cost can be reduced.

[0013]

In order to solve the above problems, the invention described in claim 1 is an inverter capable of forward conversion and reverse conversion operations, a capacitor for storing and discharging electric energy, and the inverter. In an AC power supply device that performs DC power conversion with a capacitor and transmits one DC power to the other, and supplies the AC output of the inverter to a load, the input side and the output side of the chopper are short-circuited. Switch is provided, and when the voltage of the capacitor is within the range of the rated voltage on the DC side of the inverter, the switch is turned on to directly connect the capacitor and the inverter, and the operation of the chopper is stopped. If it is out of the range of the rated voltage on the DC side, turn off the switch and connect between the capacitor and the inverter. And it is intended to drive a chopper.

According to a second aspect of the present invention, the capacitor in the AC power supply device according to the first aspect is an electric double layer capacitor.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an AC power supply device according to this embodiment. The same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. Below, different parts will be mainly described.

In this embodiment, the bidirectional chopper 2 is used.
A switch 5 for short-circuiting the chopper is provided between the terminal on the side of the capacitor 1 and the terminal on the side of the voltage inverter 3 (both can be the input side and the output side of the chopper 2).
Then, by turning on the switch 5, the capacitor 1 and the voltage inverter 3 are directly connected to remove the chopper 2 from the circuit, and the operation of the chopper 2 is stopped, and at the same time, the switch 5 is turned off. Is connected between the capacitor 1 and the voltage source inverter 3 to operate. Also, the switch 5 is
The switch control unit 6 capable of detecting the voltage of the capacitor 1 is on / off controlled.

In the above structure, the capacitor 1 is composed of a large-capacity capacitor such as an electric double layer capacitor as described above. Further, the rated voltage on the DC side of the voltage source inverter 3 is 100% to the maximum voltage of the capacitor 1.
It is a value that can cope with a fluctuation range of about 70%. Further, the AC output of the voltage source inverter 3 is supplied to a load (not shown) or leveling of various loads connected to the AC power supply 4 and the natural energy power generation device as in the prior art of FIG. It is supplied to the outside to compensate the output fluctuation. In the illustrated example, a single-phase voltage source inverter is assumed as the inverter 3, but a three-phase voltage source inverter connected to a three-phase AC power source may be used.

In such a structure, when the voltage of the capacitor 1 is within the range of 100% to 70% of the maximum voltage during both charging and discharging of the capacitor 1, the switch controller 6 turns on the switch 5, The chopper 2 is short-circuited and the capacitor 1 and the inverter 3 are directly connected. At this time, the chopper 2 stops operating. During this time, the inverter 3 is operated in the range of the DC side rated voltage according to the voltage of the capacitor 1 and performs the forward conversion operation or the reverse conversion operation. In this operation mode, since the chopper 2 is stopped, the conduction loss, the reactor loss, the switching loss, the electromagnetic noise, etc. do not occur in the chopper 2.

On the other hand, the voltage of the capacitor 1 is the maximum voltage of 7
When it decreases to less than 0%, the switch 5 is turned off by the switch control unit 6, the chopper 2 is inserted between the capacitor 1 and the inverter 3, and the chopper 2 is operated. When charging / discharging the capacitor 1 via the chopper 2, if charging / discharging is performed with constant power, the lower the voltage of the capacitor 1, the larger the charging / discharging current, and the larger the voltage change.
The period during which the voltage of the capacitor 1 is less than 70% of the maximum voltage is practically 50% or less of the total period from 25% to 100%. Therefore, in order to output the AC voltage equivalent to that when the voltage of the capacitor 1 is 70% or more of the maximum voltage, the chopper 2 is operated for the period of 50% or less to maintain the DC voltage of the inverter 3 at the rated voltage. This is all that is required, and the loss associated with the operation of the chopper 2 can be greatly reduced compared to the conventional technique shown in FIG.

In the prior art of FIG. 2, the maximum voltage conversion ratio of the chopper 2 is 25%: 1 when viewed from the capacitor 1 side.
What was 00% was 25%: 70% in this embodiment.
Therefore, the inductance of the reactor to be used is also reduced as compared with the conventional one, and the chopper 2 can be downsized and the cost can be reduced.

[0021]

As described above, according to the present invention, since the chopper is operated only when necessary according to the voltage of the capacitor as the storage element, the loss due to the operation of the chopper can be reduced as compared with the prior art. As a result, the efficiency of the AC power supply device can be improved. Further, since the maximum voltage conversion ratio of the chopper is suppressed by using the inverter having the same DC side rated voltage as when the lead storage battery is used, it is possible to reduce the size and cost of the chopper and thus the AC power supply device. . Furthermore, if a capacitor, such as an electric double layer capacitor, which has a larger capacity per volume / weight than other types of capacitors is used as a storage element, further improvement in performance and miniaturization can be achieved.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a conventional technique.

[Explanation of symbols]

1 capacitor 2 chopper 3 voltage source inverter 4 AC power supply 5 switches 6 Switch control unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeaki Ogawa             20 Kitakanzan, Otakamachi, Midori-ku, Nagoya-shi, Aichi             No. 1 Chubu Electric Power Co., Inc. (72) Inventor Ryuji Yamada             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 5H007 CB02 CC01 CC03 CC12 DA06                       DC05

Claims (2)

[Claims] 1. An inverter capable of forward conversion and reverse conversion operations, and a capacitor for storing and discharging electric energy.
An AC power supply device that performs DC power conversion between the inverter and a capacitor, and transmits a DC power of one to the other, and supplies an AC output of the inverter to a load, wherein an input side and an output of the chopper are provided. If a capacitor voltage is within the range of the DC side rated voltage of the inverter, turn on the switch to directly connect the capacitor and the inverter and stop the operation of the chopper. An AC power supply device characterized in that when the voltage is out of the range of the rated voltage on the DC side of the inverter, the switch is turned off to operate a chopper connected between the capacitor and the inverter. 2. The AC power supply device according to claim 1, wherein the capacitor is an electric double layer capacitor.