JP5649485B2 - Uninterruptible power system - Google Patents

Description

  The present invention relates to an uninterruptible power supply, and more particularly to an uninterruptible power supply having a bidirectional power converter.

  A conventional uninterruptible power supply includes a semiconductor switch connected between a commercial AC power supply and a load, and a bidirectional power converter connected between the power storage device and the load. During normal operation, the semiconductor switch is turned on, and AC power from a commercial AC power supply is supplied to the load via the semiconductor switch. Further, AC power from a commercial AC power source is converted into DC power by a bidirectional power converter and supplied to the power storage device.

  In addition, when the load current increases during normal operation and the current flowing through the semiconductor switch exceeds the rated current value, the DC power from the power storage device is converted to AC power by the bidirectional power converter and exceeds the rated current. Minute AC current is supplied to the load from the bidirectional power converter. Therefore, the current flowing through the semiconductor switch can be reduced below the rated current value.

  Further, at the time of a power failure of the commercial AC power supply, the semiconductor switch is turned off, and the DC power from the power storage device is converted into AC power by the bidirectional power converter and supplied to the load. Therefore, the operation of the load can be continued for a predetermined time even during a power failure (see, for example, Patent Document 1).

JP 2008-295160 A

  However, the conventional uninterruptible power supply has a problem in that when the current flowing through the semiconductor switch exceeds the rated current value, the effective current is supplied to the load, so that the voltage between the terminals of the power storage device decreases rapidly. When the voltage between the terminals of the power storage device decreases to the discharge end voltage, the operation of the bidirectional power converter stops, and the power supply from the bidirectional power converter to the load stops. In addition, even when the current flowing through the semiconductor switch becomes equal to or lower than the rated current before the voltage between the terminals of the power storage device decreases to the discharge start voltage, the power storage device needs to be recharged.

  Therefore, a main object of the present invention is to provide an uninterruptible power supply device capable of reducing a current flowing through a semiconductor switch to a rated current value or less while suppressing a decrease in voltage between terminals of a power storage device. .

The uninterruptible power supply according to the present invention includes a semiconductor switch having a first electrode connected to an AC power supply and a second electrode connected to a load, and a connection between the second electrode of the semiconductor switch and the power storage device. The AC power from the AC power source is converted to DC power and supplied to the power storage device, and the DC power from the power storage device is converted to AC power and supplied to the load, and flows to the semiconductor switch. A current detector for detecting a reactive current flowing in the current and the load, and a control unit for controlling the semiconductor switch and the bidirectional power converter based on the detection result of the current detector are provided. During normal operation when AC power is supplied from the AC power source, the control unit causes the semiconductor switch to conduct and also supplies DC power from the bidirectional power converter to the power storage device. If the rated current value of the semiconductor switch is exceeded, the reactive current is supplied to the load from the bidirectional power converter, and the current flowing through the semiconductor switch is the rated current value even if the reactive current is supplied from the bidirectional power converter to the load. In the case of a power failure when the AC power from the AC power supply is stopped , the DC power supplied from the bidirectional power converter to the power storage device is reduced . AC power is supplied to the load from the bidirectional power converter.

Another uninterruptible power supply according to the present invention includes a semiconductor switch having a first electrode connected to an AC power supply and a second electrode connected to a load, a second electrode of the semiconductor switch, and a power storage device. A bi-directional power converter connected between and converting AC power from an AC power source to DC power and supplying it to the power storage device, and converting DC power from the power storage device to AC power and supplying it to a load; A current detector that detects a current flowing through the semiconductor switch and a reactive current flowing through the load, and a control unit that controls the semiconductor switch and the bidirectional power converter based on the detection result of the current detector. During normal operation when AC power is supplied from the AC power source, the control unit causes the semiconductor switch to conduct and also supplies DC power from the bidirectional power converter to the power storage device. If the rated current value of the semiconductor switch is exceeded, the reactive current is supplied to the load from the bidirectional power converter, and the current flowing through the semiconductor switch is the rated current value even if the reactive current is supplied from the bidirectional power converter to the load. If the power supply exceeds the rated current value, the bidirectional current converter supplies the active current to the load and turns off the semiconductor switch in the event of a power failure when the AC power supply from the AC power supply is stopped. as well as, Ru is supplied AC power to the load from the bidirectional power converter.

  Further preferably, a bypass switch is further provided in which the first electrode is connected to an AC power source and the second electrode is connected to the second electrode of the semiconductor switch. The control unit turns on the bypass switch when the time during which the current flowing through the semiconductor switch exceeds the rated current value during normal operation exceeds a predetermined time, and the current flowing through the semiconductor switch is rated during normal operation. When the overcurrent value larger than the current value is exceeded, the semiconductor switch is turned off, and the bypass switch is turned off during a power failure.

In the uninterruptible power supply according to the present invention, the current flowing through the semiconductor switch and the reactive current flowing through the load are detected, and when the current flowing through the semiconductor switch exceeds the rated current value, the reactive current of the load is converted into a bidirectional power converter. If the current flowing through the semiconductor switch exceeds the rated current value even if reactive current is supplied from the bidirectional power converter to the load, the DC power supplied from the bidirectional power converter to the power storage device is reduced. Ru is reduced. Therefore, the current flowing through the semiconductor switch can be reduced below the rated current value while suppressing the decrease in the voltage between the terminals of the power storage device.
Further, in another uninterruptible power supply according to the present invention, the current flowing through the semiconductor switch and the reactive current flowing through the load are detected, and when the current flowing through the semiconductor switch exceeds the rated current value, both the reactive currents of the load are detected. Even if the reactive current is supplied from the bidirectional power converter and the reactive current is supplied to the load from the bidirectional power converter, if the current flowing through the semiconductor switch exceeds the rated current value, both effective currents exceeding the rated current value are The load is supplied from the power converter. Therefore, the current flowing through the semiconductor switch can be reduced below the rated current value while suppressing the decrease in the voltage between the terminals of the power storage device.

It is a circuit block diagram which shows the principal part of the uninterruptible power supply by one embodiment of this invention. It is a circuit block diagram for demonstrating the control method of the bidirectional | two-way power converter shown in FIG. It is a circuit block diagram for demonstrating the method of calculating | requiring the effective component and invalid component of an electric current from the detected value of the alternating voltage and electric current shown in FIG. FIG. 4 is a diagram showing a relationship between currents IS, IL, and IC shown in FIGS. 2 and 3. It is a figure for demonstrating the control method of the bidirectional | two-way power converter shown in FIG. It is another figure for demonstrating the control method of the bidirectional | two-way power converter shown in FIG. FIG. 7 is still another diagram for explaining a control method of the bidirectional power converter shown in FIG. 1. It is a figure which shows the comparative example of this Embodiment.

  As shown in FIG. 1, an uninterruptible power supply according to an embodiment of the present invention includes an input terminal T1 connected to a commercial AC power supply 1, an output terminal T2 connected to a load 2, a semiconductor switch 3, and a bypass switch. 4 is provided. The commercial AC power source 1 may be a three-phase AC power source or a single-phase AC power source. In FIG. 1, only a portion related to one of the three phases is shown in order to simplify the drawing and description.

  The semiconductor switch 3 is connected between the input terminal T1 and the output terminal T2. The semiconductor switch 3 is a semiconductor element that can be controlled to be turned on / off, and includes, for example, an IGBT (Insulated Gate Bipolar Transistor), a thyristor, or the like.

  One electrode of the bypass switch 4 is connected to a node N1 between the input terminal T1 and the semiconductor switch 3, and the other electrode is connected to a node N2 between the semiconductor switch 3 and the output terminal T2. The bypass switch 4 is a mechanical switch that can be turned on / off, and is configured by, for example, a relay. The rated current of the bypass switch 4 is sufficiently larger than the rated current of the semiconductor switch 3.

  The uninterruptible power supply includes a power storage device 5 that stores DC power, and a bidirectional power converter 6 connected between the power storage device 5 and the node N2. The power storage device 5 is composed of, for example, a storage battery or a capacitor. The bidirectional power converter 6 is controlled by a control signal CNT, converts the DC power of the power storage device 5 into AC power and supplies it to the load 2, and AC supplied from the commercial AC power supply 1 via the semiconductor switch 3. The electric power is converted into DC power and supplied to the power storage device 5.

  The uninterruptible power supply device includes an AC voltage detector 10, current detectors 11 to 13, and a DC voltage detector 14. The AC voltage detector 10 is connected to the input terminal T1, and detects an instantaneous value of the AC voltage VAC from the commercial AC power source 1. However, the AC voltage VAC may be detected at any position between the input terminal T1 and the output terminal T2. The current detector 11 is provided between the node N1 and the semiconductor switch 3, and detects an instantaneous value of the current IS flowing through the semiconductor switch 3. However, the current IS may be detected between the semiconductor switch 3 and the node N2.

  The current detector 12 is provided between the node N2 and the output terminal T2, and detects an instantaneous value of the load current IL. The current detector 13 is provided between the node N <b> 2 and the bidirectional power converter 6, and detects an instantaneous value of the current IC flowing into the bidirectional power converter 6. DC voltage detector 14 is connected to power storage device 5 and detects terminal voltage VDC of power storage device 5. Since IS = IL + IC, if two current detectors among the three current detectors 11 to 13 are provided, three currents IS, IL, and IC can be obtained by calculation.

  The uninterruptible power supply includes a semiconductor switch control circuit 20, a subtracter 22, a limiter 23, and a bypass switch control circuit 24. The semiconductor switch control circuit 20 includes a comparator 21 that compares the current IS detected by the current detector 11 with a predetermined overcurrent value. When the current IS is larger than the overcurrent value, the semiconductor switch 3 is turned off. Let Note that the overcurrent value is sufficiently larger than the rated current value of the semiconductor switch 3.

  The subtracter 22 subtracts the rated current value of the semiconductor switch 3 from the current IS detected by the current detector 11. Therefore, when the current IS flowing through the semiconductor switch 3 exceeds the rated current value, the output of the subtractor 22 becomes positive. The limiter 23 is a minimum 0 limiter. When the output of the subtracter 22 is 0 or less, that is, when the current IS flowing through the semiconductor switch 3 is less than or equal to the rated current value, the limiter 23 outputs 0, and the current IS is the rated current. If the value is exceeded, the current value for the excess is output.

  In response to the output current value of the limiter 23, the bypass switch control circuit 24 turns on the bypass switch 4 after a delay time corresponding to the output current value has elapsed. For example, when the output current value of the limiter 23 reaches 10% of the rated current value, the bypass switch 4 is turned on after a delay time of 60 seconds elapses from that time. Further, when the output current value of the limiter 23 reaches 20% of the rated current value, the bypass switch 4 is turned on after a delay time of 10 seconds has elapsed since that time.

  If the output current value of the limiter 23 becomes 0 before the delay time has elapsed, the bypass switch 4 is not turned on. When the bypass switch 4 is turned on, since the impedance of the bypass switch 4 is smaller than the impedance of the semiconductor switch 3, the current flowing through the bypass switch 4 becomes larger than the current IS flowing through the semiconductor switch 3, and the current IS is less than the rated current value. become.

  Moreover, at the time of a power failure in which the supply of AC power from the commercial AC power supply 1 is stopped, a power failure detection signal is output from a power failure detector (not shown). The semiconductor switch control circuit 20 turns off the semiconductor switch 3 in response to the power failure detection signal, and the bypass switch control circuit 24 turns off the bypass switch 4 in response to the power failure detection signal.

  The uninterruptible power supply includes a phase detection circuit 30, an active current / reactive current calculation circuit 31, a converter supply calculation circuit 32, a DC voltage control circuit 33, an adder 34, and a converter control circuit 35. The phase detection circuit 30 obtains the phase angle θ of the AC voltage VAC based on the instantaneous value of the AC voltage VAC detected by the AC voltage detector 10.

  The effective current / reactive current calculation circuit 31 is based on the detection results of the phase detection circuit 30 and the current detectors 11 to 13, and the effective components ISd, ILd, ICd and the invalid components ISq, ILq, ICq of the currents IS, IL, IC. Ask for.

  The converter supply amount calculation circuit 32 obtains a current value to be supplied from the bidirectional power converter 6 to the load 2 based on the calculation result of the active current / reactive current calculation circuit 31, and supplies the current value to the adder 34. give. Specifically, the converter supply amount calculation circuit 32 determines that the reactive component ILq of the load current IL is generated from the bidirectional power converter 6 side when the current IS flowing through the semiconductor switch 3 exceeds the rated current value of the semiconductor switch 3. The current value is obtained and supplied to the adder 34 so as to be supplied.

  If the current IS flowing through the semiconductor switch 3 still exceeds the rated current value of the semiconductor switch 3, the converter supply amount calculation circuit 32 also supplies the excess effective current to the load 2 from the bidirectional power converter 6 side. Thus, the current value is obtained and given to the adder 34. Moreover, the converter supply part calculating circuit 32 outputs a charging current reduction command to the DC voltage control circuit 33 when it is necessary to reduce the charging current IC to the power storage device 5. The operation of the converter supply part calculation circuit 32 will be described in detail later.

  The DC voltage control circuit 33 compares the voltage VDC between the terminals of the power storage device 5 detected by the DC voltage detector 14 with the rated voltage value, and from the bidirectional power converter 6 to the power storage device 5 based on the comparison result. A current value to be supplied is obtained and the current value is given to the adder 34. When the charge current reduction command is output from the converter supply amount calculation circuit 32, the DC voltage control circuit 33 reduces the current value.

  The converter control circuit 35 controls the bidirectional power converter 6 based on the output current value of the adder 34 and the detection value of the current detector 13. In addition, when the commercial AC power supply 1 fails, the converter control circuit 35 responds to a power failure detection signal from a power failure detector (not shown) and AC power is supplied from the bidirectional power converter 6 side to the load 2. The bi-directional power converter 6 is controlled to be supplied.

  Next, the operation of this uninterruptible power supply will be described. During normal operation, the bypass switch 4 is turned off and the semiconductor switch 3 is turned on, and AC power from the commercial AC power supply 1 is supplied to the load 2 via the semiconductor switch 3. Further, AC power from the commercial AC power source 1 is converted into DC power by the bidirectional power converter 6 and supplied to the power storage device 5.

  Also, during normal operation, when the load current IL increases and the current IS flowing through the semiconductor switch 3 exceeds the rated current value, the DC power from the power storage device 5 is converted into AC power by the bidirectional power converter 6. Then, the alternating current exceeding the rated current value is supplied to the load 2 from the bidirectional power converter 6 side. At this time, the bidirectional power converter 6 preferentially supplies the reactive component ILq of the load current IL to the load 2. Thereby, the current IS flowing through the semiconductor switch 3 can be reduced below the rated current value while suppressing the decrease in the voltage VDC between the terminals of the power storage device 5.

  When the time during which the current IS flowing through the semiconductor switch 3 exceeds the rated current value exceeds a predetermined time, the bypass switch 4 is turned on by the bypass switch control circuit 24. At this time, since the bypass switch 4 has a lower impedance than the semiconductor switch 3, a current flows through the bypass switch 4, and the current IS of the semiconductor switch 3 is reduced.

  When the load current IL increases and the current IS flowing through the semiconductor switch 3 exceeds the overcurrent value, the semiconductor switch 3 is turned off by the semiconductor switch control circuit 20. Therefore, it is possible to prevent the semiconductor switch 3 from being destroyed by an overcurrent.

  When the commercial AC power supply 1 is blacked out, the bypass switch 4 and the semiconductor switch 3 are turned off by the control circuits 20 and 24, and the DC power from the power storage device 5 is converted into AC power by the bidirectional power converter 6 and loaded. 2 is supplied. Therefore, the operation of the load 2 can be continued for a predetermined time even during a power failure.

  Next, a method for controlling the bidirectional power converter 6 which is a feature of the present application will be described in detail. In this uninterruptible power supply, as shown in FIG. 2, the instantaneous value of AC voltage VAC supplied from commercial AC power supply 1, the instantaneous value of current IS flowing through semiconductor switch 3, the instantaneous value of load current IL, The instantaneous value of the current IC supplied to the bidirectional power converter 6 is detected by the AC voltage detector 10 and the current detectors 11 to 13.

  Further, as shown in FIG. 3, the AC voltage detector 10 detects an instantaneous value of the AC voltage VAC, and the phase detection circuit 30 detects the phase angle θ of the AC voltage VAC based on the detected value. On the other hand, the instantaneous value of the load current IL is detected by the current detector 12, and the effective component ILd and the ineffective component ILq of the load current IL are obtained by the dq converter 31L based on the detected value and the phase angle θ. The dq converter 31L is included in the active / reactive current calculation circuit 31 of FIG. Similarly, the effective current / reactive current calculation circuit 31 includes an effective component ISd and an invalid component ISq of the current IS flowing through the semiconductor switch 3, and an effective component ICd and an invalid component ICq of the current IC supplied to the bidirectional power converter 6. And

  FIG. 4 is a diagram illustrating a calculation result of the effective current / reactive current calculation circuit 31. In FIG. 4, the radius of the circle indicated by the dotted line indicates the rated current value IR of the semiconductor switch 3. In FIG. 4, a current IS having a rated current value IR flows through the semiconductor switch 3, and the current IS is shunted to the load 2 and the bidirectional power converter 6. The sum of the effective component ILd and the ineffective component ILq of the load current IL and the effective component ICd of the current IC supplied to the bidirectional power converter 6 is the current IS flowing through the semiconductor switch 3.

  The converter supply amount calculation circuit 32 calculates the current to be supplied from the bidirectional power converter 6 side to the load 2 based on the calculation result of the active current / reactive current calculation circuit 31, and converts the calculation result to the converter control. This is given to the circuit 35. In the state of FIG. 4, no current is supplied to the load 2 from the bidirectional power converter 6 side, and the current ICd is supplied to the bidirectional power converter 6 to charge the power storage device 5.

  FIG. 5A shows a state where the effective component ILd of the load current IL increases from the state of FIG. 4 and the current IS flowing through the semiconductor switch 3 exceeds the rated current value IR. In this case, the converter supply amount calculation circuit 32 determines that the reactive component ILq of the load current IL should be supplied from the bidirectional power converter 6 side to the load 2 and sets ICq = −ILq. This calculation result (ICq = −ILq) is given to the converter control circuit 35 via the adder 34.

  The converter control circuit 35 controls the bidirectional power converter 6 based on the calculation result given through the adder 34. As a result, as shown in FIG. 5B, the ineffective component ILq of the load current IL is supplied from the bidirectional power converter 6 side, and IS = ILd + ICd. Further, the current IS decreases, and IS = IR in FIG.

  Further, as shown in FIGS. 6A and 6B, when ICd is relatively large, and ICq = −ILq, even if IS> IR, ICd is further reduced to IS = IR.

  Further, as shown in FIGS. 7A and 7B, when ICd = 0, when ICq = −ILq and IS> IR, it is further effective for the load 2 from the bidirectional power converter 6 side. Current ICq is supplied to set IS = IR.

  FIGS. 8A and 8B are diagrams showing a comparative example of the present embodiment, and are contrasted with FIGS. 7A and 7B. 8 (a) and 8 (b), when the load current IL increases and the current IS flowing through the semiconductor switch 3 exceeds the rated current value IR, bidirectional power conversion is performed on the excess and invalid components of the current IS. Supplied from the vessel 6 side. In this comparative example, the effective current ICd and the reactive current ICq are supplied from the bidirectional power converter 6 to the load 2, and the terminal voltage VDC of the power storage device 5 quickly decreases.

  On the other hand, in the present invention, the reactive current ICq is preferentially supplied from the bidirectional power converter 6 to the load 2 as shown in FIGS. 5 (a) (b) to 7 (a) (b). Further, it is possible to minimize a decrease in the voltage VDC between the terminals of the power storage device 5.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 AC power supply, 2 load, 3 semiconductor switch, 4 bypass switch, 5 power storage device, 6 bidirectional power converter, 10 AC voltage detector, 11-13 current detector, 14 DC voltage detector, 20 semiconductor switch control Circuit, 21 comparator, 22 subtractor, 23 limiter, 24 bypass switch control circuit, 30 phase detection circuit, 31 active current / reactive current calculation circuit, 31L dq conversion unit, 32 converter supply calculation circuit, 33 DC voltage control circuit , 34 Adder, 35 Converter control circuit, T1 input terminal, T2 output terminal.

Claims (3)

A semiconductor switch having a first electrode connected to an AC power source and a second electrode connected to a load;
Connected between the second electrode of the semiconductor switch and the power storage device, converts AC power from the AC power source into DC power and supplies the DC power to the power storage device, and converts DC power from the power storage device to AC power. A bi-directional power converter that converts the power to the load and supplies it to the load;
A current detector for detecting a current flowing through the semiconductor switch and a reactive current flowing through the load;
A control unit for controlling the semiconductor switch and the bidirectional power converter based on a detection result of the current detector;
The controller is
During normal operation in which AC power is supplied from the AC power supply, the semiconductor switch is turned on and DC power is supplied from the bidirectional power converter to the power storage device.
When the current flowing through the semiconductor switch during the normal operation exceeds the rated current value of the semiconductor switch, the reactive current is supplied from the bidirectional power converter to the load.
Even if the reactive current is supplied from the bidirectional power converter to the load, if the current flowing through the semiconductor switch exceeds the rated current value, the bidirectional power converter is supplied to the power storage device. Reduce DC power,
An uninterruptible power supply apparatus that makes the semiconductor switch non-conductive and supplies AC power to the load from the bidirectional power converter during a power failure when supply of AC power from the AC power supply is stopped. A semiconductor switch having a first electrode connected to an AC power source and a second electrode connected to a load;
Connected between the second electrode of the semiconductor switch and the power storage device, converts AC power from the AC power source into DC power and supplies the DC power to the power storage device, and converts DC power from the power storage device to AC power. A bi-directional power converter that converts the power to the load and supplies it to the load;
A current detector for detecting a current flowing through the semiconductor switch and a reactive current flowing through the load;
A control unit for controlling the semiconductor switch and the bidirectional power converter based on a detection result of the current detector;
The controller is
During normal operation in which AC power is supplied from the AC power supply, the semiconductor switch is turned on and DC power is supplied from the bidirectional power converter to the power storage device.
When the current flowing through the semiconductor switch during the normal operation exceeds the rated current value of the semiconductor switch, the reactive current is supplied from the bidirectional power converter to the load.
Even if the reactive current is supplied from the bidirectional power converter to the load, if the current flowing through the semiconductor switch exceeds the rated current value, the effective current corresponding to the rated current value is exceeded. Supplying the load from a power converter ;
An uninterruptible power supply apparatus that makes the semiconductor switch non-conductive and supplies AC power to the load from the bidirectional power converter during a power failure when supply of AC power from the AC power supply is stopped . And a bypass switch in which the first electrode is connected to an AC power source and the second electrode is connected to the second electrode of the semiconductor switch,
The controller is
When the time during which the current flowing through the semiconductor switch during the normal operation exceeds the rated current value exceeds a predetermined time, the bypass switch is conducted,
When the current flowing through the semiconductor switch during the normal operation exceeds an overcurrent value larger than the rated current value, the semiconductor switch is turned off,
The uninterruptible power supply according to claim 1 or 2 , wherein the bypass switch is turned off during the power failure.

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