JPH0614561A - Current detecting method for voltage type inverter unit - Google Patents

Abstract

PURPOSE:To detect overcurrents in all conduction modes, including short circuit mode, for a voltage type inverter unit by means of minimum number of current detectors. CONSTITUTION:Both plus and minus DC lines between a diode bridge circuit 2 and a switching element bridge circuit 3 in an inverter unit penetrate through a first current detector 5, and a second current detector 4 detects currents flowing through the DC input side of the bridge circuits 2, 3. Current can be detected through the current detector 4 under drive mode where current flows from a DC power supply 1 to a load or regenerative mode where current flows from the load to the DC power supply 1 side, whereas current can be detected through the current detector 5 under circulation mode where energy stored in the load circulates through a diode and a switching element or ground fault mode where ground fault occurs on one phase of the load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detection method in a voltage source inverter device, and more particularly, the present invention provides a minimum number of current detectors used for protection or control of the voltage source inverter device. The present invention relates to a current detection method in a voltage source inverter device that can be used.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing an arrangement of a conventional current detector in a voltage source inverter device. In the figure, reference numeral 1 is a DC power supply of a voltage type inverter device, and the DC power supply is usually obtained by converting an AC power supply into a DC by a rectifying circuit composed of a diode or the like and filtering by a capacitor.

Reference numeral 10 denotes a bridge circuit in an inverter device for converting direct current into alternating current, which has a bridge structure in which transistors 3a to 3f, which are self-turn-off devices, and diodes 2a to 2f are connected in antiparallel. The output voltage of the inverter device is controlled by driving each of the transistors 3a to 3f with a PWM signal provided by a control device (not shown).

Reference numeral 4 is a current detector provided on the direct current side of the bridge circuit 10, 11, 12 and 13 are current detectors provided on the alternating current side of the bridge circuit 10, and 9 is an AC electric motor driven by an inverter device. Therefore, the DC input current of the bridge circuit 10 and the AC output current of the bridge circuit 10 are detected by the current detectors 4, 11, 12, and 13.

Reference numeral 14 is a rectifier, 15 and 16 are resistors,
The AC signals output by the current detectors 11, 12, and 13 are converted into DC by the rectifier 14 and the resistors 15 and 16. 17
Is an absolute value circuit, which converts the inverter output current converted into direct current by the rectifier 14 and the resistors 15 and 16 into an absolute value signal 1
Convert to 01. 18 is a priority circuit, the current detector 4
Of the output 102 and the current detection signals detected by the current detectors 11, 12 and 13 and converted into direct current by the rectifier 14 and the resistors 15 and 16, a large signal is selected and output. Reference numeral 8 is an overcurrent detector, which compares the output of the priority circuit 18 with the set value 104 and outputs an inverter abnormality signal 105.

In the figure, a DC current flowing from the DC power supply 1 to the bridge circuit 10 is detected by the current detector 4 and given to the priority circuit 18. Also, the bridge circuit 1
The AC current flowing from 0 to the AC motor 9 of the load (hereinafter referred to as the load 9) is detected by the current detectors 11, 12, 13 and converted into a DC signal by the rectifier circuit 14 and the resistors R15, R16. Then, the absolute value is obtained and is given to the priority circuit 18. The priority circuit 18 selects and outputs the larger one of the input current detection signals.

The output 103 of the priority circuit 18 is given to the overcurrent detector 8 and compared with the set value 104, and is also given to an inverter current limiting circuit (not shown) or the like for use in limiting the current of the inverter device. When an overcurrent flows from the DC power supply 1 through the transistors 3a to 3f in the bridge circuit 10 and the load 9 or a load short circuit occurs, the outputs of the current detectors 11, 12, and 13 output the overcurrent via the priority circuit 18. It is applied to the detector 8 to detect an overcurrent condition or a load short circuit. Further, the ground fault overcurrent flowing from one phase of the load 9 to the ground is detected by one of the current detectors 11 to 13 provided in each phase of the bridge circuit 10.

Further, when an arcing state, that is, a so-called upper and lower arm short circuit occurs due to a defect of the transistors 3a to 3f, the current detected by the current detector 4 becomes an overcurrent state, and this detection signal is given to the priority circuit 18. Is supplied to the overcurrent detector 8 via the, and the arc state is detected.

[0009]

The following may be considered as possible overcurrent modes in the above voltage source inverter device. DC power supply 1 and bridge circuit 10 when PWM control is abnormal
A general overcurrent mode that flows between the loads 9 through. A recirculation mode of the AC motor current flowing through the load 9 and the upper or lower transistor and diode in the bridge circuit 10. A top-bottom short circuit mode caused by one of the transistors 3a to 3f in the bridge circuit 10 being erroneously fired or damaged. A ground fault mode that flows from the AC motor 9 of the load to the ground through the positive or negative input line of the inverter DC power supply 1 and the bridge circuit 10.

Conventionally, in order to protect the inverter device from all the above modes, as shown in FIG. 7, the current detector 4 for detecting the current on the DC side of the inverter device and the output side of the inverter device are used. It is necessary to provide the current detectors 11, 12, and 13 for detecting the currents of all the phases, and there is a drawback that the configuration of the inverter device becomes complicated and expensive.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and a voltage type inverter device capable of detecting overcurrents in all the above modes by a minimum number of current detectors. It is an object of the present invention to provide a current detection method in the above.

[0012]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a diode having a multi-phase bridge connection.
In the current detection method in the voltage source inverter device, in which the bridge circuit and the switching element / bridge circuit are connected in anti-parallel, and the AC side of the diode / bridge circuit and the switching element / bridge circuit are directly connected to the load, a diode A first current detector that penetrates both the DC plus side line and the minus side line between the bridge circuit and the switching element / bridge circuit as the primary side, and the second current that detects the current on the DC input side of the bridge circuit. A detector is provided, and the current in each current-flow mode of the voltage source inverter device is detected by the outputs of the first and second current detectors.

[0013]

In the drive mode in which current flows from the DC power supply to the load through the diode / bridge circuit and the switching element / bridge circuit, or in the regenerative mode in which current flows from the load to the DC power supply side, the current is always the second Since it flows to the current detector, the current can be detected thereby.

In the freewheeling mode in which the energy stored in the load flows through the diode of the diode bridge circuit and the switching element of the switching element bridge circuit, the current is always the diode bridge circuit and the switching element bridge circuit. Since it flows in the DC plus side line or minus side line between
The current can be detected by the current detector.

Further, in an inverter device provided with a commercial power source in which one line is grounded and a DC power source composed of a rectifier, when a ground fault occurs in one phase of a load, the ground fault current is always a diode as in the above case. Since the DC current flows between the bridge circuit, the switching element, and the bridge circuit in the DC positive side line or the negative side line, the ground current can be detected by the first current detector.

[0016]

1 is a diagram showing an embodiment of the present invention. In FIG. 1, the same components as those shown in FIG. 7 are designated by the same reference numerals, and 1 is a voltage source inverter. DC power supply, 2 is a diode bridge circuit composed of diodes 2a to 2f, 3 is a transistor bridge circuit composed of transistors 3a to 3f, and the diode bridge circuit 2 is provided as a flywheel diode of the transistor bridge circuit 3. In addition, the diode bridge circuit 2 and the transistor bridge circuit 3 constitute an inverter section. Further, similarly to the conventional example, the output voltage of the inverter device is controlled by each of the transistors 3a to 3 by a PWM signal given by a control device (not shown).
It is performed by driving f.

Reference numeral 4 is a first current detector, which is provided in front of the diode bridge circuit 2 and the transistor bridge circuit 3 on the DC side, and its output 102 is connected to the diode 7. Reference numeral 5 denotes a second current detector, which connects the plus side connection line and the minus side connection line of the diode bridge circuit 2 and the transistor bridge circuit 3 in common to serve as the primary side input, and its output 101 'is rectified. Given to the circuit 6.

Reference numeral 6 is a rectifier circuit for converting the output of the current detector 5 into a DC signal, 7 is a diode forming a priority circuit together with the rectifier circuit 6, and 8 is a set value of the output of the priority circuit composed of the rectifier circuit 6 and the diode 7. An overcurrent detection circuit that detects an overcurrent as compared with 104. The output 103 of the priority circuit composed of the rectifier circuit 6 and the diode 7 is given to the overcurrent detector 8 and used as the output current limiting signal of the inverter device.

Reference numeral 9 is a load composed of an AC motor or the like, and the diode bridge circuit 2 and the transistor bridge circuit 3 are directly connected and connected to each other. 2 to 6 are views for explaining each current flow mode in the embodiment shown in FIG. 1, and the current detection method in this embodiment will be described with reference to FIGS. 2 to 6.

FIG. 2 shows a conduction mode (driving mode) in which the DC power supply 1 flows from the transistor 3a through the load 9 and the transistor 3f. In this mode, no current flows in the diode bridge circuit 2, and in the current detector 5, the current flowing in the DC positive side and the current flowing in the DC negative side cancel each other out, and the output signal 101 '
Is "0". On the other hand, since a current flowing in the negative side of the direct current flows through the current detector 4, it is possible to detect an abnormal state occurring in the inverter device by detecting this current.

FIG. 3 shows a flow mode (return mode) when the transistor 3a is on and the transistor 3f is off.
In this case, the energy stored in the inductance of the load 9 flows back through the transistor 3a, the winding wire 9'in the load 9, and the diode 2a of the diode bridge circuit 2. In this mode, the current detector 5
Since only the DC positive side current is flowing on the primary side of
The current can be detected by the current detector 5.

FIG. 4 shows a flow mode (return mode) when the transistor 3f is on and the transistor 3a is off.
The inductance energy of the load 9 at this time is circulated through the transistor 3f, the winding wire 9 ′ of the load 9, and the diode 2f of the diode bridge circuit 2. In this mode, since only the DC negative side current flows through the primary side of the current detector 5, the current can be detected by the current detector 5.

FIG. 5 shows a conduction mode (regeneration mode) when the transistors 3a and 3f are turned off from the conduction mode of FIG. In this case, the inductance energy of the load 9 is the diode bridge circuit 2
DC power supply 1 through the diodes 2c and 2d of
Is regenerated to power. In this mode, no current flows through the current detector 5, and the regenerative current is detected by the current detector 4.

FIG. 6 shows a flow mode (ground fault mode) when a ground fault occurs on the input side of the load 9. In the same figure, the DC power supply 1 in FIG. 1 is shown by a commercial power supply 20, a rectifier 22 and a filter 23 so that the current path becomes clear, and the commercial power supply 20 is connected to the ground 21 in its line. As shown in the figure, when a ground fault occurs on the load 9 side,
As shown by the solid line in the figure, the ground fault current flows from the commercial power source 20 to the ground through the rectifier 22, the current detector 5, and the transistor 3a. Further, as shown by the dotted line in the figure, the current flows from the ground 21 to the ground 21 via the transistor 3d, the current detector 5, the current detector 4, the rectifier 22, and the commercial power supply 20. As is clear from the figure, the ground fault current always flows through the current detector 5 regardless of whether it flows as shown by the solid line or as shown by the dotted line, so the current detector 5 detects the ground fault current. can do.

As is apparent from FIGS. 2 to 6, the current detector 4 is provided on the direct current side, and the plus side connecting line and the minus side connecting line of the diode bridge circuit 2 and the transistor bridge circuit 3 are commonly connected. By providing the current detector 5 as the primary side input, the currents in all the conduction modes shown in FIGS. 2 to 6 can be detected by the current detector 4 or the current detector 5. It becomes possible to cope with all possible overcurrent modes in the voltage source inverter device.

In the above embodiment, an example in which a transistor is used as a switching element of an inverter device is shown, but the present invention is not limited to the above embodiment, and other elements such as FET, IGBT (Insulated Gate Bipo) may be used.
The present invention can be applied to an inverter device using other well-known switching elements such as a lar transistor. Further, in the above embodiment, an example in which an AC motor is connected as the load of the inverter device is shown, but the load of the inverter device in the present invention is not limited to the above embodiment, and the present invention is arbitrary. It can be applied to an inverter device having a load.

Further, in order to absorb the surge voltage of the transistor of the inverter device, it is effective to put the current detector 5 and the diode bridge circuit 2 in the same package, and the size can be reduced.

[0028]

As is apparent from the above description,
In the present invention, only by providing two current detectors,
It is possible to detect current in all current flow modes such as power running and regeneration of the voltage source inverter device, and perform protection such as load short circuit and ground fault in these current flow modes, or control such as current limit. be able to.

Therefore, an inexpensive and compact inverter device can be provided, and its practical effect is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a current flow mode (driving mode) in the embodiment.
FIG.

FIG. 3 is an explanatory diagram of a current flow mode (reflux mode 1) in the embodiment.

FIG. 4 is an explanatory diagram of a current flow mode (reflux mode 2) in the embodiment.

FIG. 5 is a current flow mode (regeneration mode) in the embodiment.
FIG.

FIG. 6 is a current flow mode (ground fault mode) in the embodiment.
FIG.

FIG. 7 is a diagram showing a conventional example.

[Explanation of symbols]

1 DC power supply 2 Diode bridge circuit 2a, 2b, 2c, 2d, 2e, 2f, 7 Diode 3 Transistor bridge circuit 3a, 3b, 3c, 3d, 3e, 3f Transistor 4, 5, 11, 12, 13 Current detection Unit 6,14 Rectifier circuit 8 Overcurrent detector 9 AC motor 9'Chain line in AC motor 10 Bridge circuit consisting of diode and transistor 15 and 16 Current detection resistor 17 Absolute value circuit 18 Priority circuit 20 Commercial power source 21 Earth ground 22 Rectifier circuit 23 Filter

Claims (1)

[Claims] 1. A diode having a multi-phase bridge connection
In the current detection method in the voltage source inverter device, in which the bridge circuit and the switching element / bridge circuit are connected in anti-parallel, and the AC side of the diode / bridge circuit and the switching element / bridge circuit are directly connected and connected to the load. A first current detector that penetrates both the DC plus side line and the minus side line between the bridge circuit and the switching element / bridge circuit as the primary side, and the second current that detects the current on the DC input side of the bridge circuit. A current detecting method in a voltage source inverter device, characterized in that a detector is provided, and a current in each conduction mode of the voltage source inverter device is detected by the outputs of the first and second current detectors.