JP3115143B2 - Uninterruptible power system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply used as a backup power supply when a commercial power supply fails.

[0002]

2. Description of the Related Art In a computer for performing important processing, an uninterruptible power supply (hereinafter referred to as UP)
S) is used.

In recent computers, the power requirements of the main unit have been increased along with the improvement of the processing capability, and the input power supply voltage of the main unit is also of the 200 V type.
There is a growing demand for a UPS capable of multiple output of a system.

FIG. 3 shows a schematic configuration of such a conventional UPS. Generally, a power supply of 200V system is designed to be distributed at 100V system as a potential at the midpoint ground even in the UPS shown in FIG.

In FIG. 3, the power supply of the 200 V system is a UPS.
And the midpoint of the power supply is U
The frame is grounded by being connected to the ground terminal tie of the PS. The power supply output is converted to DC by a forward converter 1 of a mixed bridge composed of an L / C filter, a high-speed switching device such as IGPT controlled by PWM, and a diode, and the output of the forward converter 1 is smoothed by a capacitor 2. Is controlled to a constant voltage. The direct current smoothed by the capacitor 2 is float-charged to a storage battery 4 connected via a diode 3, and at the time of a power failure, a discharge thyristor switch 5 connected in parallel with the diode 3 is fired, so that power from the storage battery 4 is generated. Is output.

The DC smoothed by the capacitor 2 or the DC output from the storage battery 4 at the time of a power failure is input to a full-bridge inverter 6 composed of an L / C filter and a high-speed switching device such as an IGPT that is PWM-controlled. The output is converted into a constant voltage alternating current synchronized with the voltage phase, and the output of the inverter 6 is applied to an insulating transformer 8 via a changeover switch 7 with a commercial direct feed circuit. In this case, the commercial direct feed circuit can supply power without passing through the converter as long as the commercial power supply is sound, and as a backup in case of a converter failure, etc., the reliability of the uninterruptible power supply system is improved. Things.

The output winding of the insulating transformer 8 is provided with a midpoint tap so that the output is insulated and the midpoint can be grounded by the ground terminal toe.
It is possible to obtain an uninterruptible power supply having the same configuration as the input power supply.

[0008]

[Problems that the Invention is to Solve UP of such a configuration
In S, an insulation transformer 8 with a center tap is used in the output part to perform the grounding at the middle point. However, this insulation transformer 8 has a problem that not only is large in shape and mass but also high in cost.

When the UPS is used in North America, input power is often supplied to two phases of a three-phase alternating current and a neutral point at a middle age point as shown in FIG. , Each phase voltage value is 120V, but the phase difference is 120 °
As a result, the line voltage becomes 208 V, and it is difficult to obtain an output voltage having the same configuration as the input power supply.

An object of the present invention is to eliminate the need for an insulating transformer even when a midpoint ground is required, and to provide a power supply configuration on the input side irrespective of the phase difference of each phase voltage with respect to the neutral point on the supply side. Another object of the present invention is to provide a compact, economical, and high-performance uninterruptible power supply capable of realizing an output power supply configuration equivalent to the above.

[0011]

According to the present invention, in order to achieve the above object, alternating current is supplied from an AC power source having a neutral point such as a single-phase three-wire system or a three-phase four-wire system. A plurality of forward converters for converting AC into positive and negative DC voltages centered on the neutral point, and floating charging is performed by the DC voltage output from the forward converter provided on the output side of these forward converters. A storage battery, one end of which is connected to the positive side or the negative side of the DC output terminal of the forward converter, and which operates at the time of a power outage of the AC power supply to output DC power from the storage battery; and the forward converter. A plurality of inverters configured symmetrically and converting a DC output from the forward converter or the storage battery to an AC having a configuration equivalent to the AC input of the AC power source with respect to a neutral point; An inverter provided at an output side of the converter; Switching means for switching to any one of an output or a direct transmission circuit of the input power supply, and detecting the voltage phase and the voltage phase difference input to each of the forward converters when the AC power supply is established, and performing the inverse conversion. The output voltage of each inverter is controlled in synchronization with the corresponding input voltage phase, and the phase difference between the output voltages of the inverters according to the input voltage phase difference at the time of a power outage or asynchronous operation command of the AC power supply. And control means for controlling the self-running.

Further, alternating currents are input from an AC power supply having a neutral point such as a single-phase three-wire system or a three-phase four-wire system, and these alternating currents are converted into positive and negative DC voltages around the neutral point. A plurality of forward converters, a storage battery provided on the output side of these forward converters and floatingly charged by a DC voltage output from the forward converter, and a positive side of a DC output terminal of the forward converter. Or, one end is connected to the negative side, a switching unit that operates when the AC power supply fails and outputs DC power from the storage battery, and is configured symmetrically with the forward converter, and outputs from the forward converter or the storage battery. A plurality of inverters for converting the DC to an AC having a configuration equivalent to the AC input of the AC power supply with respect to a neutral point, and provided at an output side of the inverter, and an output of the inverter. Or some deviation of the direct power supply circuit of the input power supply Comprising a switching means, and control means for the output phase of the inverter to control respectively arbitrary phase relationship set by the internal reference or external switching.

[0013]

[0014]

In the uninterruptible power supply having such a configuration,
When AC is input to the forward converter corresponding to each phase, each forward converter converts the AC into positive and negative DC voltages centered on the neutral point, and the DC voltage is symmetrical with the forward converter. Since the configured inverter converts the neutral point to an AC output voltage equivalent to the AC input voltage, it is possible to obtain an AC output with the neutral point grounded without the need for isolation by a transformer. Can be.

The control means detects a voltage phase and a voltage phase difference input to each forward converter, and controls the output voltage phase of each inverter in synchronization with the input voltage phase to thereby control the input voltage and the input voltage. An output voltage having an equivalent phase relationship can be obtained.Also, by controlling the phase difference between the output voltages of the respective inverters according to the input voltage phase difference at the time of a power failure or asynchronous operation command of the AC power supply, An AC output having an equivalent phase relationship can be obtained.

Further, when the output phase of each inverter is controlled, it can be generated independently of the input side with an internal reference or an arbitrary phase relationship set from the outside. Interconversion between systems or between single and three phases is possible.

[0017]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration example of a UPS according to the present invention. In FIG. 1, a single-phase three-wire 200 V power supply having a neutral point grounded is connected to input terminals ti1 and ti2 of the UPS. In this case, each AC input is 200 V between the lines, but the neutral point input terminal t
ie, 100V each 180 ° out of phase with respect to IE
, And the input b-phase voltage. Further, the neutral point input terminal tie and the neutral point output terminal toe are connected by a neutral point line.

The alternating current input between the input terminals ti1 and ti2 and the neutral point input terminal tie is passed through an L / C filter, and a forward converter 1a comprising a voltage doubler rectification type half bridge composed of IGPT. , 1b and converted to direct current. This forward converter 1
Of the outputs converted to DC at a and 1b, the positive half cycle with respect to the neutral point is charged to the smoothing capacitor 2a, and the negative half cycle is charged to the smoothing capacitor 2b. The direct current smoothed by the capacitors 2a and 2b is float-charged to the storage battery 4 connected via the diode 3, and in the event of a power failure, the discharging thyristor switch 5 connected in parallel with the diode 3
Is fired, so that electric power is output from the storage battery 4.

The DC smoothed by the capacitors 2a and 2b or the DC output from the storage battery 4 at the time of a power failure is inverted by a half bridge composed of an L / C filter and a high-speed switching device such as an IGPT controlled by PWM. The output of the inverters 6a, 6b is converted to a constant voltage alternating current synchronized with the input voltage phase by the converters 6a, 6b. Output to terminal toe.

On the other hand, the power supply voltage input between the input terminals ti1 and ti2 and the neutral point input terminal tie is insulated by the insulation detectors 10a and 10b, respectively, and becomes an input feedback signal to provide an input current control circuit 11a and 11b.
11b and input to the output voltage reference generation circuit 12, respectively. The DC voltages smoothed by the smoothing capacitors 2a and 2b, respectively, are converted into DC voltage feedback signals by the DC voltage insulating transformer 13 and input to the input current control circuits 11a and 11b respectively. The input current control circuits 11a and 11b control the DC voltage to a reference value and simultaneously convert the input current into a sine wave with a power factor of 1 in phase with the input voltage.
Is subjected to PWM control.

The output voltage reference generation circuit 12 generates an output voltage reference signal synchronized with the input voltage phase from the power supply, and is input to the output voltage control circuits 14a and 14b. The output voltage control circuits 14a and 14b have inverters 6a,
6b is input as a feedback signal via the insulation detectors 15a and 15b, and is applied to the inverse converters 6a and 6b.
PWM control is performed on the inverters 6a and 6b so that the output voltage of the inverter 6 becomes a sine wave voltage having the same phase as the power supply voltage.

In this case, since the input voltage from the power supply is lost when a power failure occurs, the output voltage reference generation circuit 12 is provided with a storage means for storing the input voltage phase relationship before the power failure, and maintains the phase relationship when the power failure occurs. The output voltage reference in the free-running mode is output while the output voltages of the inverters 6a and 6b can be continuously controlled. Further, at the time of power recovery, the output voltage reference generation circuit 12 can again control the output voltage reference to be synchronized with the input voltage phase so that the output voltages of the inverters 6a and 6b are synchronized with the input voltage phase. ing. Next, the operation of the thus configured UPS will be described.

If the power supply is normal, the input terminal t
AC is input from i1 and ti2 to the forward converters 1a and 1b. At this time, the forward converters 1a and 1b
At the same time, the DC output is controlled by 1a and 11b so that the DC output becomes a reference value, and the input current is PWM-controlled so that the input current becomes a sine wave having a power factor of 1 in phase with the input voltage. Inverters 6a and 6b, which convert DC to AC, output the output voltage based on the output voltage reference signal generated by the output voltage reference generation circuit 12 so that the output voltage has the same phase as the input voltage with respect to the neutral point common to the input. Output voltage control circuits 14a and 14
PWM control is performed by b.

In such a state, when a power failure occurs, the thyristor switch 5 for discharging is ignited, and the power from the storage battery 4 is converted into the inverters 6a and 6a.
b, and at this time, the inverse converter 6
Reference numerals a and 6b denote output voltage control circuits 14a and 14b based on the output reference in the free-running mode while maintaining the input voltage phase relationship before the power failure stored in the storage means of the output voltage reference generation circuit 12.
PWM control is performed by b.

When the power is restored, the output voltage reference generation circuit 12 again synchronizes the output voltage reference with the input voltage phase, so that the output voltages of the inverters 6a and 6b are synchronized with the input voltage phase. PWM control is performed by the control circuits 14a and 14b.

Usually, the relationship between the a-phase and the b-phase is 180 degrees in the case of a single-phase three-wire system, and ± 1 in the case of a three-phase four-wire system.
The phase difference is 20 degrees. Therefore, the output voltage reference generation circuit 12 stores these phase relationships when the power supply is normal, so that in the event of a power failure, the output voltage phase can be generated with the stored phase difference at the set free-running frequency. If
It is possible to continuously supply an output voltage substantially equivalent to the input power supply voltage.

As described above, according to the above-described embodiment, since the neutral point potential is fixed in common with the input side, an output voltage equivalent to the input phase relationship is realized without using an insulating transformer as in the related art. Therefore, it is possible to provide a lightweight, compact, and economically advantageous device having flexibility in the phase relationship of the input voltage. In the above, the phase control at the time of the power failure of the AC power supply has been described, but the same control as that at the time of the power failure is performed also at the time of the asynchronous operation command. Next, another embodiment of the present invention will be described.

In the above embodiment, a single-phase three-wire system or a three-phase four
The case where two pairs of converters are provided corresponding to two phases of the wire system has been described. However, a neutral point is fixed using a three-phase AC power source as a power source, and three forward converters 1a and 1b are used. , 1c and the inverters 6a, 6b, 6c, the three-phase uninterruptible power supply can be constructed without a transformer.

Further, in the embodiment shown in FIGS. 1 and 2, by taking the input voltage in parallel from the single-phase 100V system, it is possible to operate as a single-phase 100V uninterruptible power supply with the same circuit. Thus, an uninterruptible power supply with more flexibility can be configured.

Further, in the output voltage reference generating circuit,
It is also possible to generate the reference independently of the input side. In the case of FIG. 1, a single output of a 100 V system can be obtained by matching the phases of the output voltage reference even in an input 200 V system. Similarly, even with a single 100V input,
A 200 V output having a phase difference of 180 degrees or ± 129 degrees can be obtained.

On the other hand, as shown in FIG. 2, when the converter is constituted by three pairs of converters, a single-phase to three-phase or a three-phase to single-phase mutual conversion is also possible. However, when the phase relationship between the input and output is not matched as described above, the phase relationship with the commercial direct feed circuit does not match, so the continuous synchronous switching of the inverter output from the commercial direct feed circuit or the commercial direct feed circuit from the inverter output is performed. Generally becomes impossible.

[0033]

As described above, according to the present invention, it is possible to obtain an output corresponding to an arbitrary input phase relationship without providing an insulating transformer, and to freely set the input / output phase relationship. Therefore, the same converter can be used for 100V to 200V or 200V for 10
It is possible to perform 0V-system mutual conversion or single-phase to three-phase or three-phase to single-phase mutual conversion, thereby providing a compact, lightweight, and economically advantageous uninterruptible power supply.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of an uninterruptible power supply according to the present invention.

FIG. 2 is a circuit diagram showing a main circuit according to another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional uninterruptible power supply.

FIG. 4 is a diagram showing a phase relationship between various power supplies.

[Explanation of symbols]

1a, 1b, 1c forward converter, 2a, 2b smoothing capacitor, 3 diode, 4 storage battery, 5 thyristor switch, 6a, 6b, 6c reverse converter, 7
... Commercial direct delivery circuit changeover switches, 10a, 10b... Insulation detectors, 11a, 11b.
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
5b ... insulation detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02J 9/06 502

Claims (2)

(57) [Claims] An AC power source having a neutral point, such as a single-phase three-wire system or a three-phase four-wire system, is supplied with alternating current, and these alternating currents are positive and negative DC voltages centered on the neutral point. A plurality of forward converters, a storage battery provided on the output side of these forward converters and floatingly charged by a DC voltage output from the forward converter, and a positive side of a DC output terminal of the forward converter. Or, one end is connected to the negative side, a switching unit that operates when the AC power supply fails and outputs DC power from the storage battery, and is configured symmetrically with the forward converter, and outputs from the forward converter or the storage battery. A plurality of inverters for converting the DC to an AC having a configuration equivalent to the AC input of the AC power supply with respect to a neutral point, and provided at an output side of the inverter, and an output of the inverter. Or switch to any of the direct-feed circuits of the input power supply Switching means for detecting the voltage phase and the voltage phase difference respectively input to the respective forward converters when the AC power supply is established, and changing the output voltage of the inverter to the corresponding input voltage phase. And control means for controlling the phase difference between the output voltages of the respective inverters in accordance with the input voltage phase difference at the time of a power failure of the AC power supply or at the time of an asynchronous operation command, and performing self-running. An uninterruptible power supply characterized by the following. 2. An alternating current is input from an AC power supply having a neutral point such as a single-phase three-wire system or a three-phase four-wire system, and these alternating currents are positive and negative DC voltages centered on the neutral point. A plurality of forward converters, a storage battery provided on the output side of these forward converters and floatingly charged by a DC voltage output from the forward converter, and a positive side of a DC output terminal of the forward converter. Or, one end is connected to the negative side, a switching unit that operates when the AC power supply fails and outputs DC power from the storage battery, and is configured symmetrically with the forward converter, and outputs from the forward converter or the storage battery. A plurality of inverters for converting the DC to an AC having a configuration equivalent to the AC input of the AC power supply with respect to a neutral point, and provided at an output side of the inverter, and an output of the inverter. Or switch to any of the direct-feed circuits of the input power supply An uninterruptible power supply device comprising: a switching unit for controlling the output phase of the inverter, and a control unit for controlling the output phase of the inverter based on an internal reference or an arbitrary externally set phase relationship.