JP5985972B2 - Bidirectional converter and uninterruptible power supply using the same - Google Patents

Description

  The present invention relates to a bidirectional converter and an uninterruptible power supply using the same, and more particularly to a bidirectional converter that performs bidirectional power conversion between AC power and DC power, and an uninterruptible power supply using the same.

  The bidirectional converter is connected between a three-phase AC line and a DC positive bus and a DC negative bus, and performs bidirectional power conversion between the three-phase AC power and the DC power. The bidirectional converter includes three power conversion circuits each corresponding to a three-phase AC line. Each power conversion circuit includes a first transistor connected between the first node and the AC line of the corresponding phase, and a second transistor connected between the AC line of the corresponding phase and the second node. And first and second diodes connected in antiparallel to the first and second transistors, respectively, and a smoothing capacitor connected between the first and second nodes. The first and second nodes are connected to a DC positive bus and a DC negative bus, respectively. The DC positive bus and the DC negative bus are connected to the positive electrode and the negative electrode of the battery, respectively.

  When charging the battery, the three-phase AC line is connected to a three-phase AC power source. The bidirectional converter converts three-phase AC power supplied from a three-phase AC power source via a three-phase AC line into DC power, and supplies the DC power to the battery via a DC positive bus and a DC negative bus. .

  When the load is driven by a battery, the three-phase AC line is connected to the load. The bidirectional converter converts DC power supplied from the battery via a DC positive bus and a DC negative bus into three-phase AC power, and supplies the three-phase AC power to a load via the three-phase AC line.

  Patent Document 1 discloses a failure detection method for determining that an inverter has failed when a deviation between an AC current command value and an AC current feedback value exceeds a set value in the inverter.

Japanese Patent Laid-Open No. 7-227086

  In such a bidirectional converter, in order to prevent the power conversion circuit from being destroyed by an overcurrent, a first fuse is inserted between the first node of each power conversion circuit and the DC positive bus. There is a method of inserting a second fuse between the second node of each power conversion circuit and the DC negative bus (see FIG. 1).

  However, in this method, even when the fuse is blown by overcurrent during charging of the battery, the current flows through the smoothing capacitor, so that it is difficult for the current on the AC side to change. It was difficult to detect the failure from the AC side by the method.

  Further, if the battery is continuously charged with the fuse being blown, the smoothing capacitor may be excessively charged and the overvoltage may be destroyed.

  Therefore, a main object of the present invention is to provide a bidirectional converter capable of protecting a power conversion circuit from overcurrent and easily detecting the occurrence of a failure, and an uninterruptible power supply using the same. is there.

The bidirectional converter according to the present invention is a bidirectional converter that is connected between a three-phase AC line and a DC positive bus and a DC negative bus and performs bidirectional power conversion between the three-phase AC power and the DC power. Thus, three power conversion circuits each corresponding to a three-phase AC line are provided. Each power conversion circuit includes a first transistor connected between the first node and the AC line of the corresponding phase, and a second transistor connected between the AC line of the corresponding phase and the second node. And first and second diodes connected in antiparallel to the first and second transistors, respectively, and a smoothing capacitor connected between the first and second nodes. The bidirectional converter is further provided corresponding to each power conversion circuit, and corresponds to each power conversion circuit and a first fuse connected between the corresponding first node and the DC positive bus. A second fuse provided between the corresponding second node and the DC negative bus; a controller for controlling on / off of the first and second transistors of each power conversion circuit; A current detector that detects an instantaneous value of a current flowing through the positive bus or the DC negative bus, and at least one of the three sets of first and second fuses is blown based on a detection result of the current detector. And a failure detector for detecting this. The failure detector determines that at least one fuse is blown when the magnitude of the AC component of the detection value of the current detector exceeds a predetermined threshold value.

Preferably, the AC component of the detection value of the current detector has a frequency of three-phase AC power.
Preferably, the failure detector is obtained by a filter that extracts an AC component from a detection value of the current detector, an absolute value averaging circuit that calculates an absolute value average of the AC components extracted by the filter, and an absolute value averaging circuit. A comparator that compares the absolute value average of the alternating current component with a predetermined threshold value and outputs a signal indicating the comparison result.

  Preferably, the DC positive bus and the DC negative bus are connected to the positive electrode and the negative electrode of the power storage device, respectively. When charging the power storage device, the three-phase AC line receives the three-phase AC power from the three-phase AC power source, and the bidirectional converter converts the three-phase AC power from the three-phase AC power source into DC power. Supply to storage device. When the load is driven by the power storage device, the three-phase AC line is connected to the load, and the bidirectional converter converts the DC power from the power storage device into three-phase AC power and supplies it to the load.

  In the uninterruptible power supply according to the present invention, the three-phase AC power supply is connected to a load via a three-phase AC line. The uninterruptible power supply is inserted into a three-phase AC line, and is electrically connected when the three-phase AC power is normal, and non-conductive when the three-phase AC power is not normal. And a converter. The bi-directional converter is connected to the three-phase AC line between the three-phase switch and the load, and when the three-phase AC power is normal, the three-phase AC supplied from the three-phase AC power source via the three-phase switch The power is converted to DC power and supplied to the power storage device. When the three-phase AC power supply is not normal, the DC power supplied from the power storage device is converted to three-phase AC power and supplied to the load.

In the bidirectional converter and the uninterruptible power supply according to the present invention, the instantaneous value of the current flowing through the DC positive bus or the DC negative bus is detected, and the magnitude of the AC component of the detected value exceeds a predetermined threshold value. If it is determined that at least one fuse is blown. Therefore, the power conversion circuit can be protected from overcurrent, and the occurrence of a failure can be easily detected.

It is a circuit block diagram which shows the structure of the bidirectional | two-way converter by Embodiment 1 of this invention. It is a figure for demonstrating the principle of the failure detector shown in FIG. It is a circuit block diagram which shows the structure of the failure detector shown in FIG. FIG. 6 is a circuit block diagram illustrating a modification of the first embodiment. It is a circuit block diagram which shows the structure of the uninterruptible power supply by Embodiment 2 of this invention.

[Embodiment 1]
As shown in FIG. 1, the bidirectional converter according to Embodiment 1 of the present application is connected between three-phase AC lines UL, VL, WL and a DC positive bus PL and a DC negative bus NL. And bi-directional power conversion between DC power and DC power.

  DC positive bus PL and DC negative bus NL are connected to the positive electrode and the negative electrode of battery 11 (power storage device), respectively. AC lines UL, VL, WL are provided corresponding to the U phase, the V phase, and the W phase, respectively. When charging the battery 11, the AC lines UL, VL, WL are connected to the three-phase AC power source 12. When the load is driven by the battery 11, the load is connected instead of the three-phase AC power supply 12. In FIG. 1, the case where the battery 11 is charged is shown.

  The bidirectional converter includes power conversion circuits 1 to 3, fuses F1 to F6, current detectors 4 and 5, voltage detectors 6 and 7, a control unit 8, a failure detector 9, and a notification unit 10. The power conversion circuit 1 includes IGBTs (Insulated Gate Bipolar Transistors) Q1, Q4, diodes D1, D4, and a smoothing capacitor C1. Power conversion circuit 2 includes IGBTs Q2 and Q5, diodes D2 and D5, and a smoothing capacitor C2. Power conversion circuit 3 includes IGBTs Q3 and Q6, diodes D3 and D6, and a smoothing capacitor C3.

  The collectors of IGBTs Q1-Q3 are connected to nodes N1-N3, respectively, and their emitters are connected to AC lines UL, VL, WL, respectively. The collectors of IGBTs Q4 to Q6 are connected to AC lines UL, VL and WL, respectively, and their emitters are connected to nodes N4 to N6, respectively. Diodes D1-D6 are connected in antiparallel to IGBTs Q1-Q6, respectively. One terminals of smoothing capacitors C1 to C3 are connected to nodes N1 to N3, respectively, and the other terminals thereof are connected to nodes N4 to N6, respectively.

  One terminals of fuses F1 to F3 are all connected to DC positive bus PL, and the other terminals thereof are connected to nodes N1 to N3, respectively. One terminals of fuses F4 to F6 are connected to nodes N4 to N6, respectively, and the other terminals are connected to DC negative bus NL. Each of the fuses F1 to F6 is blown when a current exceeding a predetermined value flows. The fuses F1 to F6 are provided to prevent the IGBTs Q1 to Q6 from being destroyed by an overcurrent, respectively.

  Current detector 4 detects an instantaneous value of battery current Ib flowing through DC positive bus PL, and provides signal φ4 indicating the detected value to control unit 8 and failure detector 9. The current detector 5 detects an instantaneous value of the U-phase current Iu flowing through the AC line UL, and gives a signal φ5 indicating the detected value to the control unit 8.

  Voltage detection value 6 detects a voltage between DC positive bus PL and DC negative bus NL, that is, an instantaneous value of inter-terminal voltage Vb of battery 11, and gives signal φ 6 indicating the detection value to control unit 8. The detected voltage value 7 detects an instantaneous value of the line voltage Vuv between the AC lines UL and VL, and gives a signal φ 7 indicating the detected value to the control unit 8.

  Control unit 8 controls IGBTs Q <b> 1 to Q <b> 6 based on output signals φ <b> 4 to φ <b> 7 of current detectors 4, 5 and voltage detectors 6, 7 and failure detection signal φ <b> 9 from failure detector 9. That is, when charging the battery 11, the control unit 8 operates in synchronization with the line voltage Vuv (signal φ7), and turns on / off each of the IGBTs Q1 to Q6 at a predetermined timing. Thus, the three-phase AC power supplied from the three-phase AC power supply 12 via the AC lines UL, VL, WL is converted into DC power by the power conversion circuits 1 to 3, and the DC power is converted to the DC positive bus PL and the DC negative power. It is supplied to the battery 11 via the bus NL. At this time, the current Ib (signal φ4) flowing through the battery 11 is limited to a value equal to or less than a predetermined upper limit value. Further, when the inter-terminal voltage Vb (signal φ6) of the battery 11 reaches a predetermined DC voltage value, charging is stopped.

  Further, when discharging the battery 11 to supply three-phase AC power to a load connected instead of the three-phase AC power source 12, the control unit 8 turns on / off each of the IGBTs Q1 to Q6 at a predetermined timing. Let Thereby, the DC power given from the battery 11 via the DC positive bus PL and the DC negative bus NL is converted into three-phase AC power by the power conversion circuits 1 to 3, and the three-phase AC power is converted into AC lines UL, VL, Supplied to the load via WL.

  Control unit 8 fixes IGBTs Q1 to Q6 in an off state to prevent smoothing capacitors C1 to C3 from being overvoltage destroyed when failure detection signal φ9 is set to the activation level “H” level. .

  The failure detector 9 determines whether or not at least one fuse F among the fuses Q1 to Q6 has been blown based on the output signal φ4 of the current detector 4, and if it is determined that it has blown, the failure detection signal φ9 From “L” level to “H” level. When the failure detection signal φ9 is set to the “H” level, the notification unit 10 notifies the user that a failure has occurred by sound, light, or the like. The user repairs the failure and replaces the blown fuse F with a new fuse F.

  Next, the principle of the method in which the failure detector 9 determines whether or not at least one of the fuses F1 to F6 has been blown will be described. 2A shows the waveform of the line voltage Vuv between the AC lines UL and VL, FIG. 2B shows the waveform of the U-phase current Iu flowing through the AC line UL, and FIG. The inter-terminal voltages VC1 to VC3 of C3 are shown, and FIG. 2 (d) shows the waveform of the battery current Ib. 2A to 2D show a case where the fuse F1 is blown at 0.2 seconds.

  2A to 2D, the line voltage Vuv and the U-phase current Iu hardly change before and after the fuse F1 is blown. This is because a current flows through the smoothing capacitor C1 even if the fuse F1 is blown. Further, when the fuse F1 is not blown, the capacitors C1 to C3 are connected in parallel to the battery 11, so that the terminal voltages VC1 to VC3 of the capacitors C1 to C3 are equal and substantially constant. When the fuse F1 is blown, the capacitor C1 is disconnected from the positive electrode of the battery 11, an AC component appears in the terminal voltage VC1 of the capacitor C1, and VC1 gradually decreases. The AC component of VC1 has the same frequency (for example, 50 Hz or 60 Hz) as the frequency of the three-phase AC power (the frequency of the line voltage Vuv).

  When the fuse F1 is not blown, a small pulsating component appears in the battery current Ib. This pulsating component has a frequency that is three times the frequency of the three-phase AC power (the frequency of the line voltage Vuv). When the fuse F1 is blown, the current conversion circuit 1 is disconnected from the positive electrode of the battery 11. Thereby, even when the IGBT Q1 is turned on, no current flows through the fuse F1, an AC component is generated in the battery current Ib and the battery current Ib is reduced. The AC component of the battery current Ib is equal to the frequency of the three-phase AC power (the frequency of the line voltage Vuv).

  Although the case where the fuse F1 is blown has been described here, an AC component is generated in the battery current Ib and the battery current Ib is reduced even if any of the other fuses F2 to F6 is blown. . Therefore, in the present invention, it is determined whether or not the fuse has been blown based on the level of the AC component of the battery current Ib (signal φ4).

  FIG. 3 is a circuit block diagram showing the configuration of the failure detector 9. In FIG. 2, the failure detector 9 includes a high-pass filter (HPF) 20, an absolute value averaging circuit (ABS) 21, and a comparator 22. The high-pass filter 20 removes the direct current component of the output signal φ4 (battery current Ib) of the current detector 4 and passes the alternating current component. The absolute value averaging circuit 21 calculates the average absolute value of the AC component of the signal φ4 that has passed through the high-pass filter 20.

  The comparator 22 compares the absolute value average of the alternating current component obtained by the absolute value averaging circuit 21 with a predetermined threshold value VT, and outputs a signal φ9 indicating the comparison result. The signal φ9 is set to “L” level when the average absolute value of the AC component is lower than the predetermined threshold value VT, and is “H” when the absolute value average of the AC component is higher than the predetermined threshold value VT. To the level. As shown in FIG. 2D, when the fuse F1 is blown, the AC component of the battery current Ib increases. Therefore, it can be determined whether or not the fuse F is blown based on the output signal φ9 of the comparator 22.

  In the first embodiment, an instantaneous value of battery current Ib flowing through DC positive bus PL is detected, and it is determined whether or not at least one fuse F has been blown based on the detection result. Therefore, it is possible to prevent the power conversion circuits 1 to 3 from being destroyed by an overcurrent, and it is possible to easily detect the occurrence of a failure.

  In the first embodiment, it is determined whether or not the fuse F is blown based on the battery current Ib flowing through the DC positive bus PL, but the fuse F is blown out based on the battery current Ib flowing through the DC negative bus NL. It goes without saying that it may be determined whether or not it has been done.

  FIG. 4 is a circuit block diagram showing a modification of the first embodiment, and is a diagram to be compared with FIG. Referring to FIG. 4, in this modification, the high-pass filter 20 of the failure detector 9 is replaced with a band-pass filter (BPF) 23. The band pass filter 23 passes a signal component in a predetermined band including the frequency of the three-phase AC power in the output signal φ4 of the current detector 4. Since the frequency of the AC component that appears in the battery current Ib when the fuse F is blown is equal to the frequency of the three-phase AC power, it is possible to determine whether or not the fuse F has been blown even in this modified example.

[Embodiment 2]
FIG. 5 is a circuit block diagram showing a configuration of an uninterruptible power supply according to Embodiment 2 of the present invention. In FIG. 5, the uninterruptible power supply device includes a bidirectional converter 30, a three-phase switch 31, and a power failure detector 32. Bidirectional converter 30 has the same configuration as the bidirectional converter shown in the first embodiment.

  The three-phase AC power supply 12 is connected to a load 33 via AC lines UL, VL, WL. Bidirectional converter 30 is connected to the positive and negative electrodes of battery 11 via DC positive bus PL and DC negative bus NL, and is connected to AC lines UL, VL, WL between three-phase switch 31 and load 33. ing.

  The power failure detector 32 is connected to the AC lines UL, VL, WL between the three-phase AC power source 12 and the three-phase switch 31, and whether or not the three-phase AC power is normally supplied from the three-phase AC power source 12. And a signal φ33 indicating the discrimination result is output. The signal φ33 is set to “L” level when the three-phase AC power is normally supplied from the three-phase AC power supply 12, and when the three-phase AC power is not normally supplied from the three-phase AC power supply 12, for example, When a power failure occurs, it is set to “H” level. Signal φ 32 is applied to three-phase switch 31 and bidirectional converter 30.

  The three-phase switch 31 is turned on when the output signal φ32 of the power failure detector 32 is at the “L” level of the inactivation level, and is turned off when the signal φ32 is at the “H” level of the activation level. .

  When the output signal φ32 of the power failure detector 32 is at the “L” level, which is an inactivation level, the bidirectional converter 30 is connected from the three-phase AC power supply 12 via the three-phase switch 31 and the AC lines UL, VL, WL. The supplied three-phase AC power is converted to DC power, and the DC power is supplied to the battery 11 via the DC positive bus PL and the DC negative bus NL.

  Bidirectional converter 30 also provides DC power supplied from battery 11 via DC positive bus PL and DC negative bus NL when output signal φ32 of power failure detector 32 is at the “H” level of the activation level. Is converted into three-phase AC power, and the three-phase AC power is supplied to the load 33 via the AC lines UL, VL, WL.

  Next, the operation of this uninterruptible power supply will be described. When the three-phase AC power supply 12 is normal, the output signal φ32 of the power failure detector 32 becomes “L” level, the three-phase switch 31 becomes conductive, and the three-phase AC power is supplied from the three-phase AC power supply 12 to the three-phase switch. The load 33 is supplied to the load 33 through the drive 31, and the load 33 is driven. The three-phase AC power is converted into DC power by the bidirectional converter 30 and stored in the battery 11.

  When the fuse F is blown during charging of the battery 11, the operation of the bidirectional converter 30 is stopped, and the notification unit 10 notifies the user that the bidirectional converter 30 has failed. The user repairs the failure of the bidirectional converter 30 and replaces the blown fuse F with a new fuse F. Therefore, it is possible to avoid a situation in which the operation of the load 33 is stopped due to the fact that the bidirectional converter 30 has failed during a power failure.

  When the three-phase AC power supply 12 breaks down and a power failure occurs, the output signal φ32 of the power failure detector 32 becomes “H” level, the three-phase switch 31 becomes non-conductive, The load 33 is disconnected. At the same time, the DC power of the battery 11 is converted into three-phase AC power by the bidirectional converter 30 and supplied to the load 33. Therefore, the operation of the load 33 can be continued during the period when the DC power is stored in the battery 11 even during a power failure.

  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.

  UL, VL, WL AC line, PL DC positive bus, NL DC negative bus, 1-3 power conversion circuit, F1-F6 fuse, 4,5 current detector, 6, 7 voltage detector, 8 control unit, 9 failure Detector, 10 Notification unit, 11 Battery, 12 Three-phase AC power supply, Q1-Q6 IGBT, D1-D6 diode, C1-C3 smoothing capacitor, 20 High-pass filter, 21 Absolute value averaging circuit, 22 Comparator, 23 bands Pass filter, 30 bidirectional converter, 31 three-phase switch, 32 power failure detector, 33 load.

Claims (5)

A bidirectional converter connected between a three-phase AC line and a DC positive bus and a DC negative bus, and performing bidirectional power conversion between the three-phase AC power and the DC power,
Three power conversion circuits each corresponding to the three-phase AC line,
Each power conversion circuit
A first transistor connected between the first node and the AC line of the corresponding phase;
A second transistor connected between the AC line of the corresponding phase and the second node;
First and second diodes connected in anti-parallel to the first and second transistors, respectively;
A smoothing capacitor connected between the first and second nodes;
A first fuse provided corresponding to each power conversion circuit and connected between the corresponding first node and the DC positive bus;
A second fuse provided corresponding to each power conversion circuit and connected between the corresponding second node and the DC negative bus;
A controller for controlling on / off of the first and second transistors of each power conversion circuit;
A current detector for detecting an instantaneous value of a current flowing through the DC positive bus or the DC negative bus;
A failure detector for detecting that at least one of the three sets of the first and second fuses is blown based on a detection result of the current detector ;
The fault detector, you determined that the at least one fuse when the magnitude of the AC component of the detected value of said current detector exceeds a predetermined threshold is blown, bi-directional converter. The bidirectional converter according to claim 1 , wherein an AC component of a detection value of the current detector has a frequency of the three-phase AC power. The failure detector is
A filter for extracting the AC component from the detection value of the current detector;
An absolute value averaging circuit for obtaining an absolute value average of the AC component extracted by the filter;
Comparing the level of the absolute value average and the predetermined threshold of the AC component obtained by the absolute value averaging circuit, and a comparator for outputting a signal indicating a comparison result, according to claim 1 or The bidirectional converter according to claim 2 . The DC positive bus and the DC negative bus are connected to the positive electrode and the negative electrode of the power storage device, respectively.
When charging the power storage device, the three-phase AC line receives the three-phase AC power from a three-phase AC power source, and the bidirectional converter receives the three-phase AC power from the three-phase AC power source. Converted into DC power and supplied to the power storage device,
When the load is driven by the power storage device, the three-phase AC line is connected to the load, and the bidirectional converter converts the DC power from the power storage device into the three-phase AC power. supplied to the load, the bi-directional converter according to any of claims 1 to 3. The three-phase AC power supply is connected to the load via the three-phase AC line,
A three-phase switch that is inserted into the three-phase AC line, is conductive when the three-phase AC power supply is normal, and is non-conductive when the three-phase AC power supply is not normal;
A bidirectional converter according to claim 4 ,
The bidirectional converter is connected to the three-phase AC line between the three-phase switch and the load, and when the three-phase AC power supply is normal, the three-phase AC power supply passes through the three-phase switch. The three-phase AC power supplied in this way is converted into the DC power and supplied to the power storage device. When the three-phase AC power supply is not normal, the DC power supplied from the power storage device is converted into the three-phase AC power. An uninterruptible power supply that converts to phase AC power and supplies it to the load.

Images