JP7129258B2 - Uninterruptible power system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply that stably supplies electric power in normal conditions and supplies electric power in a storage means to a load in the event of an abnormality.

For example, Patent Literatures 1 to 3 disclose techniques for maintaining power supply without interruption when an abnormality occurs in the input voltage. The technique disclosed in Patent Document 1 is an operation mode in which the input commercial power supply voltage fluctuation range is within a predetermined value, and under the condition that the voltage of the power storage means becomes higher than a preset value, the series compensation for series compensation is temporarily performed. The operation of the converter (first DC/AC converter) is halted, and the power from the power storage means is used to supply power to the load via the parallel converter (second DC/AC converter).

In the technique shown in Patent Document 2, a disconnection switch is provided between an AC power supply and a load, a primary side of a transformer is connected in parallel with the load between the disconnection switch and the load, and an AC power supply is connected to the secondary side of the transformer. When the AC voltage is normal, it outputs the AC correction voltage ΔV, which is the difference between the actual output voltage V _REL of the AC power supply and the specified voltage V ^* to be supplied to the load, from the input AC voltage. A converter that converts the stored voltage of the storage means into AC power and applies it to the secondary side of the transformer is connected. It is possible to reduce the loss of the converter at that time.

The technique shown in Patent Document 3 connects a first converter for waveform improvement and power factor improvement and a second converter for voltage adjustment between an AC power supply and a load 3, A capacitor and a storage battery shared by the converter and the second converter are provided, and when the power supply is normal, the first converter supplies a compensation current for waveform improvement and power factor improvement and charges the capacitor and the storage battery to a constant voltage. When the power supply fails, the DC voltage of the capacitor and the storage battery is converted into AC by the first converter and supplied to the load, and the second converter converts the DC voltage of the capacitor and the storage battery into AC voltage, It adjusts the load voltage.

Patent No. 4304519 Patent No. 4389387 Patent No. 3082849

In the techniques shown in Patent Documents 1 and 3, when the AC input voltage is not within the normal range, the switch is turned off and the parallel power converter performs backup operation. Since it takes time for the power converter to switch from the current control mode to the voltage control mode, it may cause an instantaneous interruption to the load.

In addition, since the techniques disclosed in Patent Documents 1 to 3 all have circuit configurations using transformers, the size of the apparatus is increased. Furthermore, typically, the capacity of the transformer is about 15% of the rated output capacity, and if the transformer winding rating on the power converter side is 100 V, the transformer winding rating on the commercial line side is about 15 V, If a short circuit occurs on the AC input side during a period when the polarities of the AC input voltage and current are different, the AC output voltage of the parallel power converter is applied to the 15V winding of the transformer, and the output voltage is 100V. If , the transformer saturates and an overcurrent flows to the AC input side until the switch is turned off.

Furthermore, thyristor switches are commonly used as switches to turn on/off commercial lines because of their high instantaneous overcurrent resistance and robustness. The thyristor does not turn off completely unless the current flowing through the thyristor body falls below the holding current. In other words, the switch is not turned off until the current becomes equal to or less than the holding current, causing an overcurrent to flow, which may cause an instantaneous interruption.

Incidentally, in Cited Document 1, the power factor is improved by the active filter operation, but it is difficult to make the power factor completely 1, and near the zero crossing of the input voltage and current, There always exists a period in which the polarities of are different.

INDUSTRIAL APPLICABILITY The present invention provides an uninterruptible power supply that supplies power to a load without a momentary interruption even in the event of an abnormality such as a power failure or momentary drop due to voltage phase adjustment without using a large-sized device such as a transformer. offer.

An uninterruptible power supply according to the present invention is connected to a power supply line between an AC input and an AC output, and includes a power supply switch using a thyristor that switches on/off according to the voltage value of the AC input, and the power supply switch. a series power conversion means having an AC side connected in series to the AC output; a parallel power conversion means having an AC side connected in parallel to the AC output; a series side of the series power conversion means; and a reactor connected in series between the series power conversion means and the parallel power conversion means, wherein the parallel power conversion means converts the phase of the AC output voltage to that of the AC input voltage. While synchronizing with the phase, the voltage value of the AC output is maintained at a predetermined value and output, and the series power conversion means causes the control voltage between the series power conversion means and the reactor to be the predetermined value. The phase and amplitude of the output voltage of the series power conversion means are adjusted so as to obtain the values.

Thus, in the uninterruptible power supply according to the present invention, a power supply switch using a thyristor is connected to the power supply line between the AC input and the AC output, and switches on/off according to the voltage value of the AC input. and a series power conversion means having an AC side connected in series to the power supply switch, a parallel power conversion means having an AC side connected in parallel to the AC output, a series side of the series power conversion means, and the parallel power conversion means. and a reactor connected in series between the series power conversion means and the parallel power conversion means, wherein the parallel power conversion means converts the phase of the voltage of the AC output to the While synchronizing with the phase of the AC input voltage, the voltage value of the AC output is maintained at a predetermined value and output, and the series power conversion means is connected between the series power conversion means and the reactor Since the phase and amplitude of the output voltage of the series power conversion means are adjusted so that the control voltage becomes the predetermined value, the circuit configuration is simplified without the need for large parts such as a transformer, and when an abnormality occurs. It is possible to realize a high-performance uninterruptible power supply that can reliably prevent instantaneous interruption even if the

In particular, when a short-circuit power failure occurs during a period when the polarities of the AC input voltage and current are different, the series power conversion means is connected in series with the AC input so that the voltages applied to both ends of the reactor are equal. Since the series power conversion means controls the parallel power conversion means, the overcurrent that occurs when the parallel power conversion means is switched to the backup operation almost does not flow, and the accompanying drop in the output voltage does not occur. It is effective in being able to switch to backup operation.

In addition, the value of the reactor may be within a range that can control the charging power of the storage means, and it is sufficient that there is a phase difference between the AC input and the AC output. There is an effect that it becomes possible to realize

1 is a functional block diagram showing the configuration of an uninterruptible power supply according to a first embodiment; FIG. It is a figure which shows the case where two power supplies are couple|bonded through the reactor. 4 is a diagram showing power flow when the input AC voltage of the uninterruptible power supply according to the first embodiment is within a normal range; FIG. It is a vector relationship diagram of each voltage, such as an AC input voltage. FIG. 4 is a diagram showing a power flow when the input AC voltage of the uninterruptible power supply according to the first embodiment is out of the normal range; FIG. 4 is a diagram showing an overcurrent generated from a parallel power converter to an AC input side; 3 is a control block diagram of the uninterruptible power supply according to the first embodiment; FIG. 3 is a control block diagram of a series power converter control section in the uninterruptible power supply according to the first embodiment; FIG. 3 is a control block diagram in a normal state of a parallel power converter control section in the uninterruptible power supply according to the first embodiment; FIG. 4 is a control block diagram in an abnormal state of the parallel power converter control unit in the uninterruptible power supply according to the first embodiment; FIG. It is a figure showing other examples of a power converter in an uninterruptible power supply concerning a 1st embodiment.

Embodiments of the present invention will be described below. Also, the same reference numerals are given to the same elements throughout the present embodiment.

(First embodiment of the present invention)
An uninterruptible power supply according to this embodiment will be described with reference to FIGS. 1 to 10. FIG. FIG. 1 is a functional block diagram showing the configuration of an uninterruptible power supply according to this embodiment. The uninterruptible power supply 1 is connected between the AC power supply 2 connected to the input terminals 2a and 2b on the AC input side, the load 3 connected to the output terminals 3a and 3b on the AC output side, and the AC power supply 2 and the load 3. a power supply switch 4 using a thyristor for switching on/off of the connection according to the input voltage; a first filter circuit 5 connected in series to the power supply switch 4; a second filter circuit 7 connected in parallel to the load 3 on the AC output side; a parallel power converter 8 whose AC side is connected to the second filter circuit 7; a storage battery 9 connected to each of the series-side terminal of the device 6 and the series-side terminal of the parallel power converter 8, and a reactor 10 connected in series between the first filter circuit 5 and the second filter circuit 7 .

The AC input voltage (Vi) supplied by the AC power supply 2 as a commercial power supply is constantly detected by an AC input voltage detection unit (not shown in FIG. 1), and the voltage is in the normal range (for example, at a frequency of 50 Hz or 60 Hz) When the voltage is in the range of 90 V to 110 V), the power supply switch 4 is in the ON state, and the parallel power converter 8 has the same phase of the voltage of the AC output to the load 3 as that of the AC power supply 2. While synchronizing with each other, control is performed so that a constant output voltage (for example, 100 V) is output to the load 3 (Vo).

When the voltage of the AC power supply 2 fluctuates, the series power converter 6 makes the effective value of the phase voltage (Vst) between the first filter circuit 5 and the reactor 10 equal to the AC output voltage (Vo). , the output voltage (Vc) of the first filter circuit 5 is vectorially added to or subtracted from the AC input voltage (Vi). This addition/subtraction makes Vst and Vo equal to each other, thereby suppressing the circulating reactive current generated between the AC power supply 2 and the parallel power converter 8 . Further, in this vector calculation, the phase of the output voltage Vc of the first filter circuit 5 is added or subtracted so that the phase of the phase voltage Vst leads the phase of the AC output voltage Vo. 2 filter circuit 7 and parallel power converter 8 to convert to DC power and charge storage battery 9 under constant current/constant voltage control. The details of the processing operation based on this vector operation will be described later.

When the AC input voltage Vi is out of the normal range (for example, when the voltage is less than 90 V or greater than 110 V), an AC input voltage detector (not shown in FIG. 1) detects an abnormal state and switches the power supply. 4 is given an off signal. The uninterruptible power supply 1 operates to supply the power of the storage battery 9 to the load 3 in an abnormal state. At this time, the output of the parallel power converter 8 is controlled so that the AC output voltage Vo becomes a constant output voltage (for example, 100 V) in the same manner as described above. It becomes possible to continuously supply the same electric power.

When the normal state transitions to the abnormal state, an off signal is given to the power supply switch 4 as described above. A period may occur. Conventionally, there was a possibility that an overcurrent would flow during that period, resulting in an instantaneous interruption. However, in the present embodiment, the voltage across the reactor 10 is 0, that is, Vst= By controlling the voltage Vc by the series power converter 6 so that it becomes Vo, the overcurrent flowing to the AC output is suppressed, and the power of the storage battery 9 is controlled by the parallel power converter 8 to keep the rated AC voltage constant. It becomes possible to supply power to the load 3 completely without interruption.

Here, the functions of the series power converter 6 and the processing operation by vector operation will be described in detail. First, the active power and reactive power between the two power sources when the two power sources are coupled via the reactor L will be described with reference to FIG. In the circuit of FIG. 2A, the active power P (W) can be expressed by the following equation, where θ is the phase difference between Vi and Vo.

Also, the reactive power P(var) can be expressed by the following equation.

As shown in FIG. 2(B), when the phases match, the phase difference θ is zero, and according to equation (1), no active power flows between Vi and Vo. Moreover, when the voltage values are also the same, the reactive power does not flow according to the equation (2). As shown in FIG. 2C, when Vi leads Vo in phase, active power flows from Vi to Vo according to equation (1). As shown in FIG. 2D, when Vi has a higher voltage value than Vo, reactive power flows from Vi to Vo according to equation (2). In FIG. 2(C), when Vo leads Vi in phase, active power flows from Vo to Vi according to equation (1). On the other hand, in FIG. 2D, when Vo has a higher voltage value than Vi, reactive power flows from Vo to Vi according to equation (2). The above equations (1) and (2) are intertwined with each other, but since the maximum control value of the phase difference in the actual operation of the device is about 10 degrees, in the present embodiment, the above two equations are treated as independent.

Based on the above equations (1) and (2), calculation and processing operations when the AC input voltage Vi is within the normal range will be described. FIG. 3 is a diagram showing the power flow when the input AC voltage of the uninterruptible power supply according to this embodiment is within the normal range. The parallel power converter 8 controls the AC output voltage Vo of the parallel power converter 8 so that it is synchronized with the AC input voltage Vi and also in phase. At this time, the constant voltage control mode is operated so that the value of Vo becomes the rated value (100 V here). On the other hand, in series power converter 6, phase voltage Vst between first filter circuit 5 and reactor 10 is 100 V even when AC input voltage Vi fluctuates within the normal range (for example, 90 V to 110 V). The output voltage Vc of the series power converter 6 is controlled so as to be constant. That is, voltage control is performed so that Vi+Vc=Vst=100V. At this time, the series power converter 6 does not simply add the output voltage Vc to the AC input voltage Vi, but performs a vectorial calculation with a phase shift. That is, by controlling Vc so that the phase of the phase voltage Vst leads the phase of Vo, the power forcibly flows from the phase leading side to the phase lagging side, and passes through the parallel power converter 8. The storage battery 9 is charged.

FIG. 4 is a diagram showing the vector relationship of Vo, Vi, Vst and Vc. FIG. 4A shows the vector relationship when the charging power to the storage battery 9 is small, and FIG. 4B shows the vector relationship when the charging power to the storage battery 9 is large. In FIG. 4, the phases of the AC input voltage Vi and the AC output voltage Vo match, so the directions of the vectors also match. While the AC output voltage Vo is fixed at 100 V by the parallel power converter 8, the AC input voltage Vi fluctuates within the normal range. In FIG. 4 the vector (as a scalar value) is shown for example when it is less than 100V.

The DC power converter 6 controls Vc so that Vst has the same value as Vo (constant at 100 V). At this time, θ, that is, the advance of the phase is controlled according to the charging power setting. As θ increases, the charging power charged in the storage battery 9 increases, and the amount of charging power can be adjusted by the magnitude of θ. Since Vo is applied to the load 3, the power of the storage battery 9 is used by the parallel power converter 8 and the storage battery capacity decreases. As a result, the power to the load 3 is supplied from the AC input side.

Also, even if the AC input voltage Vi is constant at 100 V, the series power converter 6 needs to add the voltages vectorially in order to charge the storage battery 9 . If there is no phase difference between Vst and Vo, no active power flows from the AC input side. From the above equation (1), if θ=0, no active power P is generated. Therefore, in this case, the electric power to the load 3 is covered by the electric power of the storage battery 9 from the parallel power converter 8, and the storage battery 9 is only discharged without being charged. That is, even if the AC input voltage Vi is 100 V and matches the AC output voltage Vo, it is necessary to change θ to perform the charging operation to the storage battery 9 .

If, when the AC input voltage Vi is other than 100 V, the series power converter 6 adjusts Vc and does not perform vector calculation, then Vi=Vst and Vo is the output voltage of the parallel power converter 8. Since the voltage is 100 V, a potential difference occurs between Vi and Vst and Vo, causing a circulating reactive current to flow in the circuit and increasing circuit loss. In addition, since the output voltage Vo of the parallel power converter 8 is synchronized with the AC input voltage Vi and is in phase (θ=0), the power of the load 3 is not supplied from the AC input side. , is supplied from the parallel power converter 8, and the storage battery 9 is discharged.

FIG. 4 shows the vector operation (addition) of Vc in the state of Vi<Vo. is done.

In this way, the series power converter 6 controls the voltage value and phase of the voltage Vst in the preceding stage of the reactor 10 with respect to the AC output voltage Vo, thereby eliminating the circulating reactive current flowing through the circuit and reducing the circuit loss. At the same time, it becomes possible to reliably charge the storage battery 9 .

Next, calculation and processing operations when the AC input voltage Vi is not within the normal range will be described. FIG. 5 is a diagram showing the power flow when the input AC voltage of the uninterruptible power supply according to this embodiment is not within the normal range. If the AC input voltage Vi is out of the normal range due to a short circuit accident or the like (for example, Vi<90V or Vi>110V), the power supply switch 4 is turned off and the series power converter 6 is stopped. The parallel power converter 8 quits synchronization with the AC input voltage Vi and operates at a free-running frequency (fixed at 60 Hz or 50 Hz). Power supply to the load 3 is performed by the parallel power converter 8 using the power of the storage battery 9 . The voltage and current paths at this time are as shown in FIG.

When switching from the normal state to the abnormal state, the power supply switch 4 is turned off as described above. Unless the current flowing through the body goes to zero, it will actually remain conductive. At this time, if the circuit does not include the series power converter 6 as described above, or if the circuit does not perform control to satisfy Vst=Vo, when an input short-circuit power failure occurs, as shown in FIG. At that time, an overcurrent is generated from the parallel power converter 8 to the AC input side through the short circuit. Then, when the overcurrent becomes zero (crosses zero), the thyristor finally turns off and the overcurrent stops flowing, so that power can be supplied to the load 3 . In other words, power is not supplied to the load 3 while the overcurrent is occurring, resulting in an instantaneous interruption.

In order to solve such a problem, in the present embodiment, the series power converter 6 always performs control such that |Vst|=|Vo| Since control is also performed to advance the phase of Vst, overcurrent does not flow to the input side until the power supply switch 4 using a thyristor is turned off. Therefore, it is possible to switch the backup operation to the load 3 completely without interruption.

Next, the control of the uninterruptible power supply according to this embodiment will be described in more detail. FIG. 7 is a control block diagram of the uninterruptible power supply according to this embodiment. The uninterruptible power supply 1 includes an AC input voltage detector 61 that detects the AC input voltage Vi, a DC current detector 62 that detects the DC current of the storage battery 9, and a storage battery 9 A DC voltage detector 63 that detects the DC voltage of, a control voltage detector 64 that detects the phase voltage between the first filter circuit 5 and the reactor 10, and an AC output voltage detector 65 that detects the AC output voltage Vo. a series power converter control unit 66 that controls the series power converter 6 based on the AC input voltage Vi, the charging current Idc of the storage battery 9, the charging voltage Vdc of the storage battery 9, the control voltage Vst, and the AC output voltage Vo; A parallel power converter control section 67 that controls the parallel power converter 8 based on the input voltage Vi and the AC output voltage Vo.

As described above, the series power converter control unit 66 and the parallel power converter control unit 67 control the operations of the series power converter 6 and the parallel power converter 8, respectively, so that the AC input voltage Vi falls within the normal range. It is possible to realize stable power supply to the load 3 according to the fluctuation of the AC input voltage Vi in some cases, and stable power supply to the load 3 when the AC input voltage Vi is not within the normal range. It's becoming In addition, when the AC input voltage Vi transitions from a normal state to an abnormal state, the control operation of the series power converter control unit 66 and the parallel power converter control unit 67 enables non-instantaneous operation switching. It is possible.

FIG. 8 is a control block diagram of the series power converter controller in the uninterruptible power supply according to this embodiment. The series power converter 6 performs constant current and constant voltage charging control on the storage battery 9 as described above. In the PLL, by giving a phase slide instruction value corresponding to the amount of charge in the storage battery 9 to the reference sine wave synchronized with the AC input voltage Vi, the series power converter 6 is synchronized with the AC input voltage Vi. The phase of the control voltage Vst is adjusted to control charging power to the storage battery 9 . By this phase adjustment, the power on the AC input side is converted to DC power through the reactor 10, the second filter circuit 7 and the parallel power converter 8, and the storage battery 9 is charged with the DC power.

The phase slide instruction value for phase adjustment is a first value obtained by amplifying the difference between the DC current Idc detected by the DC current detector 62 and the charging current instruction value Idcref, and the DC voltage detector 63. A second value obtained by amplifying the difference between the DC voltage Vdc and the charging voltage command value Vdcref is ORed, the DC voltage Vdc of the storage battery 9 is lower than the charging voltage command value Vdcref, and the DC current flowing through the storage battery 9 is When it is larger, the first value is selected, and when the DC voltage Vdc of the storage battery 9 is higher than the charging voltage command value Vdcref and the DC current flowing through the storage battery 9 is small, the second value is selected and the phase slide command value is selected. is determined.

Next, the series power converter 6 controls the effective value (1) of the AC output voltage Vo and the AC The difference between the waveform obtained by multiplying the reference sine wave (2) synchronized with the input voltage Vi by a multiplier and the control voltage Vst detected by the control voltage detector 64 is amplified, and a pulse modulation signal is generated in the PWM control section. , drives the series power converter 6 . That is, when the AC input voltage Vi is within the normal range, the control voltage Vst follows the fluctuations in the AC output voltage Vo. Overcurrent from the converter 8 to the AC input side can be prevented. In addition, in the case of backup operation due to an abnormality in the AC input voltage Vi, the series power converter 6 prevents overcurrent from flowing until the power supply switch 4 is substantially stopped, thereby preventing an instantaneous interruption that occurs during switching. can be eliminated completely.

FIG. 9 is a control block diagram in a normal state of the parallel power converter control unit in the uninterruptible power supply according to this embodiment. When the AC input voltage Vi is within the normal range, the parallel power converter 8 multiplies the reference sine wave synchronized with the phase of the AC input voltage Vi in the PLL by the output voltage amplitude instruction value (for example, an instruction value of 100 V). The AC output voltage Vo is feedback-controlled so that the value is constant.

FIG. 10 is a control block diagram in an abnormal state of the parallel power converter control unit in the uninterruptible power supply according to this embodiment. When the AC input voltage Vi falls within the abnormal range, the thyristor of the power supply switch 4 is turned off, and the parallel power converter 8 is switched from charging operation to backup operation. At this time, the AC output voltage Vo of the parallel power converter 8 is feedback-controlled so as to become a value obtained by multiplying the reference sine wave by the AC output voltage amplitude instruction value.

In this embodiment, the series power converter 6 and the parallel power converter 8 are described as full-bridge circuits, but they are not limited to full-bridge circuits, and may be half-bridge circuits as shown in FIG.

As described above, in the uninterruptible power supply according to the present embodiment, a short-circuit power failure occurs during a period in which the polarities of the AC input voltage and current are different, and when switching to backup operation, the series power converter is By controlling the voltage applied to both ends of the reactor to be zero, it is possible to prevent the flow of overcurrent and eliminate the drop in the output voltage that accompanies this, allowing the switching operation to be performed without interruption. be possible.

In addition, the value of the reactor should be within a range that can control the charging power of the storage battery, that is, within a range that can generate a potential difference between the AC input voltage and the AC output voltage. It is possible to improve the efficiency of the device.

1 Uninterruptible Power Supply 2 AC Power Supply 2a, 2b Input Terminal 3 Load 3a, 3b Output Terminal 4 Feeding Switch 5 First Filter Circuit 6 Series Power Converter 7 Second Filter Circuit 8 Parallel Power Converter 9 Storage Battery 10 Reactor 61 AC Input Voltage detector 62 DC current detector 63 DC voltage detector 64 Control voltage detector 65 AC output voltage detector 66 Series power converter controller 67 Parallel power converter controller

Claims (4)

A power supply switch using a thyristor that is connected to a power supply line between an AC input and an AC output and switches ON/OFF according to the voltage value of the AC input;
a series power conversion means having an AC side connected in series with the power supply switch;
Parallel power conversion means in which the AC side is connected in parallel to the AC output;
storage means connected to the series side of the series power conversion means and the series side of the parallel power conversion means;
A reactor connected in series between the series power conversion means and the parallel power conversion means,
The parallel power conversion means synchronizes the phase of the voltage of the AC output with the phase of the voltage of the AC input, maintains the voltage value of the AC output at a preset predetermined value, and outputs the series power. The uninterruptible power supply, wherein the conversion means adjusts the phase and amplitude of the output voltage of the series power conversion means so that the control voltage between the series power conversion means and the reactor becomes the predetermined value. Device. In the uninterruptible power supply according to claim 1,
a first filter comprising an LC filter connected in series between the power supply switch and the series power conversion means;
An uninterruptible power supply comprising a second filter comprising an LC filter connected in parallel between the AC output and the parallel power conversion means. In the uninterruptible power supply according to claim 1 or 2,
The uninterruptible power supply, wherein the series power conversion means adjusts the phase of the control voltage in a direction leading the phase of the voltage of the AC input to set the control voltage to the predetermined value.
In the uninterruptible power supply according to claim 3,
An uninterruptible power supply in which the series power conversion means controls the charging power to the storage means by adjusting the progress of the phase of the control voltage.

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