JPH09252547A - Uninterruptible power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an uninterruptible power supply apparatus in which a higher harmonic component flowing out to a system is removed, by a method wherein a storage battery is charged by a second converter and the higher harmonic component generated by a first converter is controlled so as to be offset. SOLUTION: In an ordinary operation, a first converter 5 rectifies power from a system, and the rectified power is inputted to an inverter 3. Then, the inverter inverts the supplied power into an alternating current so as to be supplied it to a load. In addition, at this time, a second converter 6 charges a storage battery 4, higher harmonics whose phase is opposite to that of, and whose value is identical to that of, higher harmonics which are detected by a current transformer 7 and which are generated by the first converter 5 are generated, and higher harmonics on the input side of an uninterruptible power supply apparatus are removed. In the power failure of the system, DC power from the storage battery 4 is inverted into AC power by the inverter 3 so as to continue the supply of electricity to the load. As a result, the capacity of the second converter 6 can be reduced, and higher harmonics which flow out to the system can be removed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an uninterruptible power supply device having a function of charging a storage battery from a grid.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional uninterruptible power supply (hereinafter referred to as U
A configuration diagram of PS) is shown. The UPS includes an EMI filter 1, a converter 2, an inverter 3 and a storage battery 4.

The UPS normally uses the EMI filter 1
The system power supplied to the converter 2 via the converter is converted into direct current by the converter 2. The DC power converted by the converter 2 is supplied to the inverter 3 and also to the storage battery 4 to charge the storage battery 4. Inverter 3
Converts the supplied DC power into AC power and supplies it to the load.

EMI provided on the AC side of the converter 2
The filter 1 is for removing high frequency ripple generated by the PWM control of the converter 2. Also,
At the time of power failure of the system, the DC power from the storage power source 4 is converted into AC power by the inverter 3 and supplied to the load, so that the power supply to the load is continued even at the time of power failure of the system.

[0005]

Conventionally, DC power was supplied to an inverter for supplying power to a load by one converter and a storage battery serving as a power source in the event of a system power failure.
In order to charge the storage battery, it was necessary to perform constant voltage and constant current control on the converter, and it was also necessary to increase the capacity of the converter.

As the capacity of the converter increases, the high frequency ripple generated by the PWM control of the converter also increases, and it is necessary to increase the capacity of the EMI filter for suppressing the high frequency ripple.

Therefore, in the present invention, it is necessary to charge the storage battery by charging the storage battery while paying attention to the fact that the converter needs constant voltage and constant current control in order to charge the storage battery, whereas power supply to the inverter is not necessary. A converter for supplying power to the inverter is separately provided, and only the converter for charging the storage battery is subjected to constant voltage and constant current control, thereby downsizing the device. Further, by providing a converter for charging a storage battery with an active filter function, a UPS is provided that removes harmonic components flowing from the other converter to the system.

[0008]

In the uninterruptible power supply according to claim 1 of the present invention, AC power from the grid is converted into DC power by the first converter, and the DC power is converted into AC power by the inverter. And supply power to the load. Further, the accumulator is charged by the second converter, and harmonics of the same value are generated in opposite phases so as to cancel out the harmonic components generated by the first converter, thereby removing the harmonics on the alternating current side. .

In the uninterruptible power supply according to claim 2 of the present invention, in the uninterruptible power supply according to claim 1, the first converter is a diode rectification type converter, and the second converter is a high-speed switching element. The PWM rectification type converter can reduce the harmonic components generated from the first converter.

In the uninterruptible power supply according to claim 3 of the present invention, in the uninterruptible power supply according to claim 1 or 2, an EMI filter is provided on the AC side of the second converter, which occurs when the converter is switched. It is possible to suppress high frequency ripple that occurs.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a UPS according to the first embodiment of this invention. The UPS according to the first embodiment of the present invention uses a first converter 5 of a diode rectification system, a second converter 6 of a PWM rectification system, a storage battery 4 serving as a power source at the time of a power failure, and a direct current to generate an alternating current. An inverter 3 for converting to electric power, an AC device 7 for detecting AC side harmonics of the first converter, a current transformer 8 for detecting AC side harmonics of the second converter, and a current transformer 7. A control circuit 10 that performs active filter control based on the output of the current transformer 8 and has a storage battery charging function, and a first converter 5
And a blocking diode 11 for preventing the storage battery 4 from being charged.

During normal operation, the first converter 5 rectifies the electric power from the grid, and the rectified electric power is used by the inverter 3
Input. Since the first converter 5 is of the diode rectification type and does not perform high-speed switching, it has less switching noise than the PWM rectification type. Then, the inverter 3 converts the supplied power into an alternating current and feeds the load.

In addition, at this time, the second converter 6 charges the storage battery 4, and at the same time, the harmonic current having the same value as the harmonic wave generated by the first converter 5 and detected by the current transformer 7 has the opposite phase. To remove the harmonics on the input side of the UPS.

At the time of system power failure, the DC power from the storage battery 4 is converted into AC power by the inverter 3 and the power supply to the load is continued. With such a configuration, the capacity of the PWM converter can be reduced, and the PWM converter
By operating the converter as an active filter, harmonic components on the input side of the UPS can be removed.

Further, as shown in FIG. 2, the PW of the UPS of FIG.
The EMI filter 1 may be provided on the AC side of the M-rectification type second converter. In such a case, since the converter for feeding the inverter (diode rectification system converter) and the converter for charging the storage battery (PWM rectification system) are separately provided, the capacity of the EMI filter is different from that of the converter for charging the storage battery. Since only the input capacitance is required, the capacitance of the EMI filter can be made smaller and smaller than the conventional one.

[0016]

In the uninterruptible power supply according to claim 1 of the present invention, the power from the first converter is supplied to the inverter, the second converter charges the storage battery, and the power is generated from the first converter. The harmonics flowing out to the system can be removed by generating the harmonics of the same value in opposite phases so as to cancel out the harmonic components that are generated.

In the uninterruptible power supply according to claim 2 of the present invention, in the uninterruptible power supply according to claim 1, the first converter is a diode rectification type converter and the second converter is a high speed switching element. The PWM rectification type converter can reduce the harmonic components generated from the first converter.

In the uninterruptible power supply according to claim 3 of the present invention, in the uninterruptible power supply according to claim 1 or 2, the EMI filter is provided on the alternating-current side of the second converter, which occurs when the converter is switched. It is possible to suppress high frequency ripple that occurs.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a UPS according to a first embodiment of this invention.

FIG. 2 is a schematic diagram of a UPS according to another embodiment of the present invention.

FIG. 3 is a schematic diagram of a conventional UPS.

[Explanation of symbols]

 1 ... EMI filter 3 ... Inverter 4 ... Storage battery 5 ... Diode rectification converter 6 ... PWM rectification converter 7, 8 ... Current transformer 10 ... Control circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H02M 7/48 9181-5H H02M 7/48 N (72) Inventor Atsushi Otsuka Shibaura, Minato-ku, Tokyo Chome 1-1, Toshiba Corporation Head Office

Claims (3)

[Claims] 1. A first converter for converting AC power into DC power, a second converter for converting AC power into DC power, and a power source in the event of a power failure charged by the DC power from the second converter. And an inverter for converting DC power from the first converter or DC power from the power storage unit into AC power, and a second converter for charging the power storage unit and the first converter. An uninterruptible power supply comprising: a control unit that controls so as to cancel a harmonic component that is generated. 2. The first converter converts AC power into DC power with a diode, and the second converter uses high speed switching elements to convert AC power into DC power by PWM control. The uninterruptible power supply according to Item 1. 3. The EMI is provided on the AC side of the second converter.
The uninterruptible power supply according to claim 1 or 2, further comprising a filter.