JP4304519B2 - Uninterruptible power system - Google Patents

Description

The present invention relates to an uninterruptible power supply that supplies a stable power to a load even when an input commercial power supply fluctuates, and more particularly to a technique for improving the reliability of the uninterruptible power supply.

  FIG. 5 shows a circuit configuration of a conventional series voltage compensation uninterruptible power supply. In the circuit of FIG. 5, the AC switch 4 and the secondary winding of the transformer 2 are connected in series to the AC bus between the AC input terminal 10u and the AC output terminal 11U. A filter capacitor is connected to the primary winding of the transformer 2. 7 and the AC side terminal of the series converter 24 composed of the semiconductor bridges 20 and 21 are connected. The AC side terminal of the parallel converter 25 composed of the semiconductor bridges 22 and 23 sharing the DC part with the series converter 24 is connected to the AC output terminals 11U and 11V via the reactor 6. In addition, the storage battery 3 is connected to the direct current portions of the series converter 24 and the parallel converter 25.

  In such a circuit configuration, when the power supply voltage of the input commercial power source connected to the AC input terminals 10u and 10v fluctuates, the secondary winding voltage of the transformer 2 can be adjusted by controlling the series converter 24. By compensating the voltage fluctuation of the input commercial power supply with the secondary winding voltage of the transformer 2, a stable AC voltage can be supplied to the AC output terminal. For example, if the fluctuation of the input commercial power supply is a voltage drop, the series converter 24 is controlled so that the transformer 2 adds the drop voltage to compensate for the drop voltage. Here, when a load current flows through the AC bus, power is injected from the series converter 24 to the AC bus via the transformer 2. The energy required there is supplied from the AC bus by causing the parallel converter 25 to perform a forward conversion operation (converting AC to DC). Conversely, if the fluctuation of the input commercial power supply is a voltage rise, the series converter 24 is controlled so that the transformer 2 subtracts the rise voltage to compensate for the rise voltage. Here, when a load current flows through the AC bus, the series converter 24 absorbs DC power via the transformer 2. The DC power (energy) is regenerated to the AC bus by causing the parallel converter 25 to perform an inverse conversion operation (converting DC to AC).

The voltage waveform of each part at this time is shown in FIG. During the period when the input voltage is decreasing, the secondary winding voltage of the transformer 2 is in-phase voltage and compensates for the decreased voltage. During the period when the input voltage is increasing, the secondary winding voltage of the transformer 2 is in reverse phase. It can be seen that the voltage is compensated for the rising voltage.
Details of such operations are disclosed in Patent Document 1, for example.
Furthermore, the parallel converter 25 has a reactive current component compensation that flows from the AC output terminal to the load, that is, a so-called active filter function, and operates so that the current input from the AC input terminal to the device side becomes a sine wave with a power factor of 1.
Details of such operations are disclosed in Non-Patent Document 1, for example.
Noto 2586984 Fuji time signal, vol.77, no.6, 2004, p458-p462, large-capacity UPS "UPS8000 series"

  In the prior art, there is a delay in the control response of the series converter 24 and the parallel converter 25. Therefore, when the load suddenly changes or the input voltage suddenly changes, which is an unforeseen external factor, charging / discharging of the storage battery 3 occurs slightly but temporarily due to the delay in the control response. There was a problem that the DC voltage fluctuated.

  Normally, the storage battery 3 is held in a fully charged state. At this time, if the storage battery 3 is discharged due to the delay in the control response, the storage battery 3 has sufficient energy, so the DC voltage decreases. However, there is no particular problem. However, when charging occurs, the storage battery 3 is overcharged and the DC voltage increases greatly, which causes a problem in device protection. Therefore, prevention of overvoltage of the DC voltage has been a problem.

In the first aspect of the present invention, a transformer connected in series between an AC input terminal and an AC output terminal, a first DC / AC converter for driving the transformer, and the first DC / AC converter And a second DC / AC converter having a DC part in common and a power storage means connected to the DC part, and connecting the AC output of the second DC / AC converter to the AC output terminal. When the input commercial power supply voltage fluctuation is within a predetermined value, the second DC / AC converter supplies or regenerates DC power from the AC output terminal side to the first DC / AC converter, The AC output voltage is stabilized by adjusting the transformer voltage by the DC / AC converter, and when the input commercial power supply voltage fluctuation is a predetermined value or more, the power is stored in the load via the second DC / AC converter. In an uninterruptible power supply that supplies power In the operation mode in which the input commercial power supply voltage fluctuation range is within a predetermined value, the first voltage is temporarily set under the condition that the voltage of the power storage means is higher than a preset value and the load power is smaller than a preset value. The operation of the DC / AC converter is halted, and power is supplied to the load via the second DC / AC converter with the power from the power storage means.

According to a second aspect of the invention, there is provided an AC input switching means connected in series between an AC input terminal and an AC output terminal, and a DC / AC converter having a power storage means in the DC section, When the AC output of the converter is connected to the AC output terminal and the input commercial power supply voltage fluctuation is within a predetermined value, the DC / AC converter supplies or regenerates DC power from the AC output terminal side to the power storage means. If the input commercial power supply voltage fluctuation is greater than or equal to a predetermined value, the input commercial power supply voltage fluctuation range is within the predetermined value in the uninterruptible power supply that supplies power to the load from the power storage means via the DC / AC converter. In the operation mode, under the condition that the voltage of the power storage means is higher than a preset value and the load power is lower than the preset value, the AC input switching means is temporarily opened, and the power from the power storage means At DC Supplying power to the load via an AC converter.

  During normal operation when the input commercial power supply is not determined to be out of power, if a rise in DC voltage is detected, power supply from the input commercial power supply to the load is temporarily suspended, and the parallel converter control operation is active filtered. By switching from operation + battery charging operation to driving operation that supplies stable power to the load with energy from the storage battery, it is possible to effectively prevent an increase in DC voltage and improve device reliability. Is possible.

  The present invention relates to an uninterruptible power supply that supplies power to a load from a steady-state input commercial power source and supplies power to the load from a storage battery during a power failure via an inverter (inverter). Even so, when the storage battery voltage rises above a predetermined value, power is temporarily supplied from the storage battery to the load via the DC / AC converter.

  A circuit configuration of the first embodiment of the present invention is shown in FIG. In the main circuit of FIG. 1, the secondary winding of the transformer 2 is connected in series to the AC bus between the AC input terminal 10 and the AC output terminal 11, and the AC side terminal of the series converter 24 is connected to the primary winding. It is connected. The AC side terminal of the parallel converter 25, which shares the DC converter with the series converter 24, is connected to an AC bus having the AC output terminal 11. Further, the series converter 24. The storage battery 3 is connected to the DC part of the parallel converter 25. Here, the current detector 40 is for detecting the AC output current Iout, the current detector 41 is for detecting the output current Iinv of the parallel converter 25, and the current detector 42 is for detecting the charging current Ib of the storage battery.

In such a main circuit configuration, as a normal operation in a range where the voltage of the input commercial power supply is not determined to be a power failure, the control device 30 detects the AC output current Iout by the current detector CT40, and the invalidity included in the Iout The current component Iq is calculated by the calculation, and so-called active filter control is performed so that the parallel converter 25 compensates for the Iq, and at the same time, the charging of the storage battery 3 from the detection of the charging current Ib and the DC voltage Vdc of the storage battery 3 by the current detector 42 is performed. Control is in progress. Furthermore, the voltage Vout of the AC output terminal 11 is detected, and the output voltage constant control is performed on the series converter 24 so that this Vout becomes a constant voltage.
During such a control operation, an unexpected external factor such as a sudden change in the input commercial power supply voltage or a sudden change in the load occurs, and the DC voltage Vdc fluctuates due to a delay in the control response of the control device 30, resulting in an overvoltage. In this case, the DC voltage determination unit 31 determines the overvoltage, sends a signal to the operation condition determination circuits 33 and 34, and the control device 30 controls the series converter 24 according to the output conditions of the operation method selection circuits 33 and 34. The constant control is switched to the pulse OFF for all pauses, and the control of the parallel converter 25 is switched from the active filter control + storage battery charging control to the constant output voltage control.

  By this operation, the series inverter 24 connected to the primary winding of the transformer 2 is turned off, so that the transformer primary side is equivalent to an open state, and the AC input current Iin coming from the input commercial power supply is Instead of being limited to zero, instead of constant output voltage control of the parallel converter 25, it becomes possible to continuously supply stable power to the load with the energy from the storage battery 3. In this operation, since the energy of the storage battery 3 is consumed and discharged, the direct-current voltage Vdc naturally decreases and it becomes possible to return to the original state.

  A circuit configuration of the second embodiment of the present invention is shown in FIG. The difference from FIG. 1 which is the first embodiment is that an output current determination unit 32 is added after the DC voltage determination unit 31. When the overvoltage of the DC voltage Vdc is determined by the DC voltage determiner 31, if the load is large and the AC output current Iout detected by the current detector 40 flows sufficiently, the control of the control device 30 is not switched. By adding a discharge command from the storage battery discharge command device 35 to the storage battery charge control, it is possible to discharge excess energy flowing into the storage battery 3 from the parallel converter 25 to the load, and to restore the DC voltage Vdc to the original value. It becomes possible to return to the state. However, at this time, if the AC output current Iout is zero and there is no load, there is no other party that discharges excess energy of the storage battery 3, so that there is a risk of a reverse power flow that regenerates energy on the input commercial power supply side. Reverse power flow is not allowed due to the uninterruptible power supply performance. Therefore, the output current determiner 32 determines the magnitude of the output current Iout, and the control of the control device 30 is switched only when Iout is small.

  The circuit configuration of the third embodiment of the present invention is shown in FIG. The difference from FIG. 1 which is the first embodiment is that the main circuit configuration is a general constant commercial power supply type uninterruptible power supply device which does not include the transformer 2 and the series converter 24. Therefore, in FIG. 1, the transformer 1 and the series converter 24 performed the function of limiting the input current Iin to zero when the DC voltage Vdc is determined to be an overvoltage. However, in the circuit of FIG. 3, the AC switch 4 is turned off. This is equivalent function. The operation switching control of the parallel converter 25 when the DC voltage becomes an overvoltage is the same as in FIG.

  The circuit configuration of the fourth embodiment of the present invention is shown in FIG. The difference from FIG. 3 which is the third embodiment is that an output current determination unit 32 is added after the DC voltage determination unit 31. Since the fourth embodiment is a combination of the third embodiment and the second embodiment, the details are omitted.

  The present invention relates to overvoltage protection of a storage battery of a constantly commercial power supply type uninterruptible power supply, but can be applied to a switching power supply using a power storage means, a DC / DC converter, and the like.

Circuit configuration example showing the first embodiment of the present invention Circuit configuration example showing the second embodiment of the present invention Circuit configuration example showing the third embodiment of the present invention Circuit configuration example showing the fourth embodiment of the present invention Conventional circuit configuration example Operation explanatory diagram of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Transformer 3 ... Storage battery 4 ... AC switch 6 ... Reactor 7, 8 ... Capacitor 9 ... Load 10, 10u, 10v ... AC input terminal
11, 11U, 11V ... AC output terminals 20-23 ... Semiconductor bridge 24 ... Series converter 25 ... Parallel converter 30 ... Control device 31 ... DC voltage determination device
32 ... Output current determination device 33, 34 ... Operation method selection circuit 35 ... Storage battery discharge command device 40-42 ... Current detector

Claims (2)

A transformer connected in series between an AC input terminal and an AC output terminal, a first DC / AC converter that drives the transformer, a first DC / AC converter, and a DC unit that shares a DC unit 2 DC / AC converter and a power storage means connected to the direct current section, the alternating current output of the second DC / AC converter is connected to the alternating current output terminal, the input commercial power supply voltage fluctuation is predetermined If the value is within the range, DC power is supplied or regenerated from the AC output terminal side to the first DC / AC converter by the second DC / AC converter, and the transformer voltage is supplied by the first DC / AC converter. To stabilize the AC output voltage and to supply power to the load from the power storage means via the second DC / AC converter when the input commercial power supply voltage fluctuation is greater than or equal to a predetermined value. In
In an operation mode in which the input commercial power supply voltage fluctuation range is within a predetermined value, the first voltage is temporarily set under the condition that the voltage of the power storage means is higher than a preset value and the load power is lower than a preset value. An uninterruptible power supply characterized in that the operation of a DC / AC converter is stopped and power is supplied to a load via a second DC / AC converter with power from a power storage means. AC input switching means connected in series between an AC input terminal and an AC output terminal, and a DC / AC converter having a power storage means in a DC section, and the AC output of the DC / AC converter is the AC When the input commercial power supply voltage fluctuation is within the specified value when connected to the output terminal, DC power is supplied or regenerated from the AC output terminal side to the power storage means by the DC / AC converter, and the input commercial power supply voltage fluctuation is In the case of the predetermined value or more, in the uninterruptible power supply that supplies power to the load from the power storage means via the DC / AC converter,
AC input switching is temporarily performed in an operation mode where the input commercial power supply voltage fluctuation range is within a predetermined value, under the condition that the voltage of the power storage means is higher than a preset value and the load power is lower than a preset value. An uninterruptible power supply characterized by opening the means and supplying power to the load via a DC / AC converter with power from the power storage means.

Images